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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => LAB Subwoofer FUD Forum Archive => Topic started by: Mark Steven Lewis on July 26, 2007, 08:54:50 pm

Title: Push pull configuration for LAB Horn?
Post by: Mark Steven Lewis on July 26, 2007, 08:54:50 pm
In earlier discussion, it was generally agreed that the push pull driver configuration minimizes the 2nd order distortion, correct?

If so, it doesn't seem very hard to apply this to the LAB horn. Does this make sense? If so, what would be the best way to achieve the push pull arrangement? Change the horn and/or reverse the phase of the driver?

If this works, is it worth the effort? Thanks for consultation.

... Mark
Title: Re: Push pull configuration for LAB Horn?
Post by: Vince Byrne on July 27, 2007, 01:32:29 pm
Mark Steven Lewis wrote on Thu, 26 July 2007 19:54

In earlier discussion, it was generally agreed that the push pull driver configuration minimizes the 2nd order distortion, correct?

If so, it doesn't seem very hard to apply this to the LAB horn. Does this make sense?


What problem are you trying to solve? Do you hear objectionable distortion in the output from LABs?

Distortion in the LABs is already typically single digit, and lower than the vast majority of sub designs. Of the low distortion that remains, 2nd order is the least objectionable and is musically relevant.

The LAB design is pretty optimized, and it is doubtful you could make this type of modification without negatively affecting output SPL, frequency response, extension, etc.

Quote:

If this works, is it worth the effort? Thanks for consultation.


It wouldn't be for me, only you can judge if it would be for you. A more important question might be if it doesn't work. You could end up with a very expensive pile of firewood.
Title: Re: Push pull configuration for LAB Horn?
Post by: Josh Billings on July 28, 2007, 04:07:31 am
It's already been done. I have a pair of them

pispeakers.com

12pi

There is very little change and the added size isn't worth the difference. They are pretty much the same speakers just the push pull is quite a bit wider and more expensive Machined Aluminum parts.

I'd say stick with the labs and get a bunch of em

-Josh Billings
Title: Re: Push pull configuration for LAB Horn?
Post by: Grant Rider on July 29, 2007, 03:41:01 pm
The machined aluminum parts are for cooling not push/pull. I built some after lots of emails with Wayne Parham and I can tell you for sure they work great. Flat pack kits make them easy to build. I was impressed.

The cooling plugs work great for sure. You should put them in labs. No reason to leave them out because its cheap insurance from blown woofers.  I blew woofers easy without plugs and don't blow them with plugs. I also tried a blower motor to cool down the woofers and it didn't work as well. The cooling plugs made my speakers work at mondo power levels.

The push/pull part makes sense to me too but I haven't got any way to check it. Maybe a side by side measurement will be made to know for sure how much distortion goes down in 12Pi basshorns compared to labs. Hopefully someone will take labs to Tulsa in October.
Title: Re: Push pull configuration for LAB Horn?
Post by: Josh Billings on July 29, 2007, 08:04:38 pm
I've owned both and i would take the LABs any day. They are smaller, put out the same SPL (Honestly can't notice a difference) and they are cheaper to make.

You can buy the 12pis alrady assembled though for a reasonable price ($2,200). However i wish i went smaller, like the danley TH-115s in the beginning. These giant horns are just way too big.

4 TH-115s would take up a lot less space than 4 LABs/12pis and make things a lot easier on the back

-Josh Billings
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on July 29, 2007, 11:11:10 pm

I'm sorry you feel that way, Josh. Honestly, I'm a bit surprised since you wrote to me last month asking prices for flat pack kits.  I know you wanted drivers, CNC cut wood and machined aluminum all for $750.00, but that's way below cost.  The raw materials, baltic birch, aluminum, hardware and drivers for either a 12Pi or a LABhorn cost at least that much, without precision CNC machining.

The LABhorn is a great subwoofer, so you could definitely do worse than building a set of them.  Your preference is entirely your affair.  That said, I must clarify a couple of things about the 12Pi basshorn sub.

The 12Pi basshorn uses the same drivers as the LABhorn, but the similarities end there.  The 12Pi basshorn subwoofer has a few tricks up its sleeve that set it ahead.  It uses push-pull drive to reduce distortion and it uses a patent-pending cooling system that increases its thermal limit and power handling capacity.  It is also different than the LABhorn in flare shape, throat area, mouth area and front and rear chamber sizes.

The reduction in distortion from push-pull drive is evident in measurements, as is the reduction in motor temperatures and increased power handling that result.

Compare the response curves of the horns measured at the 2005 Prosound Shootout.  We measured distortion at this event, so you can compare the 12Pi basshorn with other horns that don't use push-pull drive.  In all of the charts, amplitude response is shown as a blue line and THD+N distortion is shown in violet.  You'll notice that at high power levels, the 12Pi basshorn sub has a lot less distortion than the other horns that didn't use push-pull drive.  You'll also notice that distortion doesn't rise rapidly under horn cutoff like the other basshorns do.  Rising distortion under cutoff is to be expected, since the horn unloads.  But the 12Pi doesn't rise nearly as much because of its push-pull drive.

There's one other thing that may be of interest to you as a DIY'er.  Some people omit front chamber fill.  Response is still good, so I guess it's optional.  But response is better when front chamber fill is installed as shown in the plans.

When the 12Pi basshorn is made with front chamber volume of 20 liters, response is perfectly flat from 30Hz up.  But this is difficult to do in practice, and makes manufacturing difficult.  The front chamber fill shown in the plans reduces front chamber volume to under 30 liters.  This makes nice response, having only a slight dip around 45Hz.  When the 12Pi basshorn is made without any fill in its front chambers, they're larger, causing a little more dip around 45Hz.  Response is still good, but not as good as when the front chambers are smaller.

See the post called "12Pi basshorn subwoofer - the best yet!" for more information on response changes with respect to different front and rear chamber sizes.
Title: Re: Push pull configuration for LAB Horn?
Post by: Grant Rider on July 30, 2007, 06:58:35 am
Josh Billings wrote on Mon, 30 July 2007 01:04

I've owned both and i would take the LABs any day. They are smaller, put out the same SPL (Honestly can't notice a difference) and they are cheaper to make.


I see the 12Pi as a souped up lab. It maybe isn't louder at the same power level but can take more power without blowing drivers. Look at it like insurance. Don't think the cost difference is much if any at all unless you use the expensive castor wheels.  Laughing

Josh Billings wrote on Tue, 17 July 2007 05:21

Maybe i'm doing something wrong but i've never experienced the LABs outperform a JBL Dual 18 (SRX). I know they are supposed to be able to...maybe only in groups of 4. I know that's supposed to be the magic number

-Josh Billings


I think you have a different perspective? Small size might be better for you so the big hornsubs are no good?  I've been told smaller indoors venues are better served with smaller nonhorn boxes.
Title: Re: Push pull configuration for LAB Horn?
Post by: Josh Billings on July 30, 2007, 07:41:08 am
Wayne:

I'm not knocking the speaker, i'm just saying if i had it to do over again i'd probably go with 4 LABs vs. 3 12pis (Roughly Same size). The plates start warming up a bit and i don't feel too comfortable throwing much more than 1,800 watts at each cab which is 200 more than what i put at the LAB Horns with no failures (3 years of use).

The LAB Horns are a little lighter, a little smaller and a little cheaper to make (less aluminum / machining & less wood since it's a smaller cabinet). There may be a SLIGHT increase in SPL and yes it can probably handle a bit more power but with the plates warming up i know power compression is setting in and there isn't much left for the drivers to put out. More boxes is the only answer.

I'd say if you're going with one of these, make sure you do 4 to get it to sound good. We had 2 12pis & 2 LAB Horns Together (4 total) and the sound really impressed me. They were like new speakers. The block of 4 is what these things seem to need to work properly. They word well otherwise, but if you're going with less than 4 i'd recommend some good Dual 18s (EAW SB-850/1000).

I do indoor stuff and smaller venues so i do think that these big horns may of not been the right choice.

To clear everything up, the speakers sound great and they perform flawlessly and there is nothing wrong with them at all. They are fantastic speakers, but when posed with the choice of the 12pis or LABs (i've owned both) i think the LABs  are just a better choice if starting from scratch. They perform equally well (can't hear a difference between the two) and if i would have to learn towards one as being better as far as performance is concerned i'd lean towards the 12pi. It's just the added cost & size vs. minor performance increase that i would give it to the lab.

-Josh Billings
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on July 30, 2007, 11:25:02 am

Thanks for the clarification, Josh.  I agree with you about using direct radiators in small environments rather than using a small number of basshorns.  That makes sense.  I also agree with you that the 12Pi is what a person would pick if they wanted quality and could spend a little more;  It's a no-compromise basshorn.  However, I do want to point out that the cost difference between DIY building a 12Pi and a LABhorn is marginal.  It's only about $100 if buying pre-made aluminum parts, even less if you machine them yourself.  Plans for both the 12Pi and the LABhorn are available at no cost, and no purchase is necessary.

The thermal benefits of the cooling plug have been quantified.  Tests show that a LAB12 driver with a cooling plug can be run continuously with power levels that are 225% higher than one without a cooling plug.  That's significant.  I'd suggest that all 12Pi and LABhorn owners should install them.  As has been said many times before - It's cheap insurance.

You said the cooling plates on your 12Pi basshorns start to warm at 1800 watts.  That's good because it means heat is being conducted away from the motors and dissipated by the plate.  Now just imagine how hot the motors are in your LABhorns, since they have no heat condution path to the access panels.  At that power level, the voice coil glue in your LABhorns is being weakened and will eventually fail.  You told me this had already happened when we first spoke.  You were looking for driver recone kits, as I recall.

Performance improvements using the push-pull arrangement has also been quantified.  Measurements have shown this configuration to be very effective at reducing distortion.  It is employed by many manufacturers, including JBL and EAW.  The JBL 728S we measured at the 2006 Prosound Shootout uses push-pull drive, for example.

There are two woofers in both the LABhorn and the 12Pi basshorns.  Since there are two woofers in use, it makes sense to orient them so they cancel distortion.  One could argue that the distortion is euphonic or they could argue that it is not all that audible.  We've all heard those arguments about distortion in subwoofers over the years.  But if we're willing to compromise ourselves with those kinds of arguments, why bother making improvements at all?  We could all have just settled with 1970's gear and called it good.

I don't mean to be argumentative, and I appreciate your candor.  But I have worked very hard to make the 12Pi basshorn be the best I could make it.  It has undergone a lot of development and testing, and has proven itself.  So I think it is important to let people see the test data in addition to our comments here.  Some of this data is specific to the 12Pi, but a lot of it is general purpose information that is useful to anyone studying subwoofers and loudspeakers in general.


12Pi development and construction

Test results and related information
Title: Re: Push pull configuration for LAB Horn?
Post by: peter.golde on July 30, 2007, 06:42:31 pm
Josh Billings wrote on Tue, 17 July 2007 05:21

Maybe i'm doing something wrong but i've never experienced the LABs outperform a JBL Dual 18 (SRX). I know they are supposed to be able to...maybe only in groups of 4. I know that's supposed to be the magic number
-Josh Billings


One Lab by itself is not very impressive unless corner loaded, 4 together are a very different story. It seems maybe you went too big out of the gate without better quantifying your needs. I use 4 24" wide Tuba 30's each loaded with a single Eminence 4012 and have been beating on them regularly for over a year now (EDM). They have the same number of drivers and roughly the same size as 2 JBL SRX dual 18's, but they easily spank the JBL's for output, throw, sound quality, low freq response, efficiency, indoors or out, small room or large.
I would not recommend any front loaded boxes for bass after owning, listening to several different bass horn designs. I still say the biggest problem with huge amounts of good clean low bass, is not enough midbass. To put any front loaded box on top of Labs, you will not be getting the full potential. The Lab and other horn subs (when used properly) move serious amounts of air. In order to get the full effect of how much air is being moved, you need to do the same with a midbass horn, which will add the hard hitting impact or kick, clean and powerful. Care also has to be taken with placement within a room to reach the full potential.

Josh, you should have been happy to feel heat being sinked away from the drivers to the outside air, it can only help prolong driver life under abusive conditions. Power compression does set in, but grouping horns together, corner or wall loading, thereby increasing efficiency, helps the drivers to not have to work as hard, moving more air with the same amount of power rather than creating more heat.



Title: Re: Push pull configuration for LAB Horn?Cooling question?
Post by: Ivan Beaver on July 31, 2007, 07:59:27 am
Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?  Don't they get pretty hot just sitting there-therefore putting heat back INTO the driver with the driver acting as a heat sink for the cooling plug?

Of course if they are protected from the sun by say another cabinet, then how well do they radiate the heat by not having accesss to open air, therefore reducing the effectivness.

Were the tests done with the plugs covered up with another cabinet or laying on the ground, and not just standing out in free air?
Title: Re: Push pull configuration for LAB Horn?Cooling question?
Post by: peter.golde on July 31, 2007, 09:42:36 am
Ivan Beaver wrote on Tue, 31 July 2007 07:59

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?  Don't they get pretty hot just sitting there-therefore putting heat back INTO the driver with the driver acting as a heat sink for the cooling plug?

Of course if they are protected from the sun by say another cabinet, then how well do they radiate the heat by not having accesss to open air, therefore reducing the effectivness.

Were the tests done with the plugs covered up with another cabinet or laying on the ground, and not just standing out in free air?


Interesting points about reverse heat sinking in the sun, something to think about. I lost a horn sub driver playing outside due to high winds into the horn mouth, the high air pressure at the horn mouth created very high pressure at the driver, and shattered the cone. Like reverse Bernoulli effect.
Title: Re: Push pull configuration for LAB Horn?Cooling question?
Post by: John Roberts {JR} on July 31, 2007, 10:13:13 am
Ivan Beaver wrote on Tue, 31 July 2007 06:59

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?  Don't they get pretty hot just sitting there-therefore putting heat back INTO the driver with the driver acting as a heat sink for the cooling plug?

Of course if they are protected from the sun by say another cabinet, then how well do they radiate the heat by not having accesss to open air, therefore reducing the effectivness.

Were the tests done with the plugs covered up with another cabinet or laying on the ground, and not just standing out in free air?


What do you mean "we"....

Your comments are a consideration for any external heat sink, but I suspect we'll get a much longer answer.

JR
Title: Re: Push pull configuration for LAB Horn?Cooling question?
Post by: Wayne Parham on July 31, 2007, 10:44:23 am

Ivan Beaver wrote on Tue, 31 July 2007 06:59

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?


We recommend a denim flap be placed over plates exposed to direct sunlight.  It can be snapped in place, and it works perfectly.  This information is included in the documentation that comes with the horns, kits and plan requests.

There is enough surface area on the plate that no real airflow is required to dissipate heat wicked out of the motor core.  But you definitely don't want sunlight heating the plates.
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on July 31, 2007, 11:01:52 am

Wicking heat out of the motor core is something that has caught the attention of several loudspeaker manufacturers.  It is very effective.  In my opinion, it is as important as gap venting.

Heat radiated from the voice coil builds up in the core and is not effectively removed by venting.  It increases thermal compression, shifts electro-mechanical parameters and weakens the voice coil adhesive, often eventually causing failure.

In the example Josh gave above, (4) LABhorns without cooling plugs verses (3) 12Pi basshorns with cooling plugs, the cooling plugs give the 12Pi's the edge.  Four horns provide 2.5dB more output than three, but cooling plugs more than double the power handling, which is a 3dB increase.  Both systems will be in power compression at maximum power but the system without cooling plugs enters compression sooner and its effects are more severe.  Further, the system without cooling plugs is more prone to failure, and will likely melt the voice coil adhesive at extended sustained high power levels.  So the 12Pi has a clear advantage.
Title: Re: Push pull configuration for LAB Horn?
Post by: Tom Danley on July 31, 2007, 03:35:24 pm
Hi Wayne
At the risk of triggering even more promotional posts, I hesitate to reply,  guessing (based on past exchanges) you will not read with a mind towards understanding but only towards crafting another torrent of such replies.

I found it interesting you chose to respond so extensively to the poster who’s first hand experience with both, led him to say   “I've owned both and i would take the LABs any day. They are smaller, put out the same SPL (Honestly can't notice a difference) and they are cheaper to make.”

Well lets see what the jist is here, I mean aside from his feelings that you try to talk him out of in several following posts.

The Lab IS the truck pack size the group (Here) picked and has the low cutoff the group (Here) picked.
Get the picture, it IS the size it is because that is what people wanted, it also has the low cutoff it has for the same reason and for use in a group.
I did not pick these things and it was not because I was limited to the driver at hand, I derived the parameters, specified the driver remember.

You (at the same point in time) argued against the idea of the heavy / strong driver on the AA forums.

Later, you find the LAB sub approach actually does work, but has fatal flaws that can be resolved simply by throwing away one of the main criteria and make it bigger.
You take the driver made for this job, take the same folding arrangement (with more kinks than needed) and increase its cubic Volume.
You find with the increased size at one Watt you can get what, a dB more in some places, dang, that is like… radical dude.

With your plugs you claim to raise the power handing 225%
You might have been able to find a condition where this might be true, to suggest that this is true in use with music or in general use is disingenuous as I would bet you did not measure the electro acoustic efficiency of a group of labs to a group of Pi’s or under power with music in actual use.
You larger compliance volume (which I see you have addressed with a retro fit filler plug) did smooth the response for one box, at the cost of more excursion for a given power.

Under the right conditions, your plugs would help too, but so do the aluminum plates already used in the lab sub, those get hot too.       Unlike your plugs, there was no claim made about how much the unusual aluminum cover plates helped, only that they do a little compared to wood.
While the aluminum cover plates transfer heat out of the chamber and driver, to the out side world, that is conditional on how they are used and most sound folks know you can still blow a driver even with a cool magnet
The more dynamic the source, the less likely the magnet temperature will reflect the instantaneous VC temp.
Heck, on most of my Tapped horns, the drivers are fully out in the open, mounted  “where the air is really moving” but I don’t claim any increase in PHC over normal.

So far as the push pull part, it is generally not considered worth the effort and other things are so much stronger factors in measured results.
In particular, the lab sub’s “strong heavy driver” in a small back volume (ala Servodrive alignment) which at the time was fully contrary to the “W bin” light cone / big volume horn lore of the day, when combined with a linear motor, produces much less distortion and much more acoustic power than those “old school” horn driver alignments.

Here too, I would bet you did not actually measure a group of LABs side by side with your Pi’s.  You might well be pleased with how low in distortion your Pi’s measure, but so are the owners of the Labs subs, they are also lower than most everything out there.

Lastly since your spinning your pitch off the lab sub as the main reference, build, instrument and (fairly) measure a few side by side.
Even better, to get an actual perspective, compare it and yours to the big money / big loudspeaker names people have been buying for the last 10 years.
In addition to something cool to build, instead of more W bins,  part of the point of the lab sub project was to expose how lame some “well-respected” and costly products actually were, a fact only visible when measured or exposed in side by sides.
While the Lab sub is a mature project now and there are many new subwoofers out there, it still holds up very well.

Cheers,
Tom Danley

Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on July 31, 2007, 04:50:43 pm

Josh said the 12Pi was slightly louder than the LABhorn and that he was happy with its performance.  But he also said he prefered LABhorns because they were easier to build, smaller and cheaper.  He went on to say he preferred JBL SRX-728S dual 18's to LABhorns.  That's fair;  He is doing indoor gigs.

The 12Pi basshorn has been extensively tested and it does exactly what I say it does.  It's not like it is just some hypothetical design on paper.

I posted to clarify a few things, because I though Josh's initial comments gave the wrong picture of some technical details.  There's no need to rehash;  My comments are shown above in this thread.

The cooling plug is something that can be added to LABhorns.  That way they can benefit from improved cooling just the same as the 12Pi's.  People can make their own or they can buy them.  Without a cooling plug, there is no conduction path to the access plate so it is ineffective as a heat sink.  The whole point of discussing things like this here is so people can learn things to take advantage of and make their sound systems better.

The LABhorn size was chosen by the group, and so had a size contraint.  That's fine.  I wasn't involved with that and have no complaint.  I also have no complaint with the driver chosen.  The whole issue of heavy verses light cones or Keele verses Leech is an argument you have had with others.

My argument with you regarding the LABhorn was with your suggestion to use it well under cutoff for hifi systems.  I said that if you use a 30Hz basshorn down to 16Hz, you're really just making a distortion amplifier.  At 16Hz, a LABhorn is unloaded and is just a direct radiator in an undersized sealed box.  The fundamental isn't loud at all because neither the sealed rear chamber or the horn pathway are tuned for it.  But the second and third harmonic is presented to the horn and amplified by it.

If the LABhorn used push-pull drive, that would help a lot to reduce distortion below cutoff.  I don't know that I would suggest using it below cutoff for other reasons, but at least you would have the distortion cancelling effects provided by the push-pull configuration.

By the way, will you be bringing any subwoofers to the Prosound Shootout in October?  We'd hate to miss you there a third year.
Title: Re: Push pull configuration for LAB Horn?
Post by: Josh Billings on July 31, 2007, 07:04:53 pm
I'd really love to see some TH-115s & Original LAB Subwoofers against the 12pis actually Smile

-Josh
Title: Re: Push pull configuration for LAB Horn?
Post by: Pascal Pincosy on July 31, 2007, 07:08:37 pm
Josh Billings wrote on Wed, 01 August 2007 00:04

I'd really love to see some TH-115s & Original LAB Subwoofers against the 12pis actually Smile

-Josh


+1

Pascal
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on July 31, 2007, 09:14:40 pm

Josh Billings wrote on Tue, 31 July 2007 18:04

I'd really love to see some TH-115s & Original LAB Subwoofers against the 12pis actually Smile

-Josh


Me too.

Honestly, it should be a very nice time.  A bunch of winners come to these things and a great time is had by all.  Pretty much all the gear represented is great and the people there are super good folks.
Title: Re: Push pull configuration for LAB Horn?
Post by: Josh Billings on August 01, 2007, 07:02:49 am
Wish i could of afforded 4 of those TH-115s, smaller cabinets would be nice for the small room we are in

-Josh Billings
Title: Re: Push pull configuration for LAB Horn?
Post by: Tom Danley on August 01, 2007, 10:53:16 am
Hi Wayne

“My argument with you regarding the LAB horn was with your suggestion to use it well under cutoff for hifi systems. I said that if you use a 30Hz basshorn down to 16Hz, you're really just making a distortion amplifier. At 16Hz, a LABhorn is unloaded and is just a direct radiator in an undersized sealed box.”

Your recollection is conveniently skewed, the idea of using them in a living room for home theater wasn’t until after the project design was done.
Your objection was in the initial design phase, I know at least one person found them entertaining and saved your posts, perhaps they will post them and refresh your memory.

“By the way, will you be bringing any subwoofers to the Prosound Shootout in October? We'd hate to miss you there a third year.”

We go to other peoples shoot-outs, like the last one in New York, but I would ask, have you ever taken your box anywhere, I mean a shoot out other than yours?

As a look at the archives (here) from last year would show, you were, at the time, unwilling to go into detail about what you were going to do, your replies to me were cryptic at best, you turned down an offer to have a TEF machine and operator because he is a friend of mine and it wasn’t clear if you were going to have much in the way of competitive products there.
You have to understand, this is a business, it costs money to ship speaker and equipment to “other peoples” shoot outs and there has to be a plausible business justification to go.

Can you honestly look at the photo’s from the first year and say it would have made sense to go, I don’t think so.  Maybe last year it might have.

So, if your keen to have my stuff there, get someone with a TEF machine or something just as reliable and accurate, get some commercial subwoofers in addition to Jeff’s and the Basmaxx to test and compare to.  
Get some popular touring sound subwoofers.
In other words, make it something that makes sense for us to do.

This would be a chance for you to finally hear the full range Synergy horns too.
It would be logical to bring a couple SH-50’s to put above the subs too don’t you think?
The possible subs would be the TH-115, TH-215, TH-50, a new one and possibly even the Matterhorn in case you go for most/lowest bass from “one box”.
I don’t know if it would be fair to compare the TH-115 to the Pi, it is half the size and weight, yet its measurements suggest it would still be ok.
Cheers,
Tom


Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on August 01, 2007, 12:54:41 pm

Tom Danley wrote on Wed, 01 August 2007 09:53 (about the LABhorn)

Your objection was in the initial design phase, I know at least one person found them entertaining and saved your posts, perhaps they will post them and refresh your memory.


That's not true.  I didn't know about the LABhorn until its design was done.  A prototype had been built and measurements placed online.  People were already ordering drivers and starting to build with them.  You posted about the LABhorn on another forum, suggesting it would be useful in home hifi systems driven to very low frequencies.  You said that it would be fine to drive it below cutoff because the power levels were low.

I countered saying I didn't think that was a good idea because even though it probably wouldn't hurt the drivers at moderate power levels, it might not sound as good when used below 30Hz for several reasons.  I maintained that a basshorn used below cutoff is basically a direct radiator in a fancy box.  Response gets peaky near cutoff.  Below cutoff, output drops and distortion goes up.  It seemed to me then, and still does now, that a direct radiating woofer is probably be a better deal for home hifi than a basshorn used well below cutoff.

I was asked by either you or Todd Michael what I would do if I were going to build a 30Hz basshorn instead.  Not for home hifi, not for use below 30Hz, I was asked my idea of what should be done.  Maybe you guys were just trying to call my bluff or something, I don't know.  But that challenge is what ultimately prompted me to design the 12Pi basshorn subwoofer.  It is "what I would do."

Tom Danley wrote on Wed, 01 August 2007 09:53 (about past Prosound Shootouts)

As a look at the archives (here) from last year would show, you were, at the time, unwilling to go into detail about what you were going to do, your replies to me were cryptic at best, you turned down an offer to have a TEF machine and operator because he is a friend of mine and it wasn’t clear if you were going to have much in the way of competitive products there.


The Prosound Shootouts have always been grass-roots events where we were interested in gathering useful data.  We asked Too Tall and some of the others here to do the measurements, but it was not possible.  So all the exhibitors agreed to self-police.  We found a good venue and posted a test plan of what we planned to do.

Tom Danley wrote on Wed, 01 August 2007 09:53

You have to understand, this is a business, it costs money to ship speaker and equipment to “other peoples” shoot outs and there has to be a plausible business justification to go.


Yes, I understand.  I also know the drive from Chicago to Tulsa and think you would enjoy yourself if you came down.  I think it would also be good exposure, not that you need it but it couldn't hurt.  I expect it would be less costly than shipping to NYC.  I don't know about the "ours" and "yours" part of the shootouts, but I would like to see each of them to be all-inclusive and welcoming.  You are certainly welcome to attend and always were.

Tom Danley wrote on Wed, 01 August 2007 09:53

So, if your keen to have my stuff there, get someone with a TEF machine or something just as reliable and accurate, get some commercial subwoofers in addition to Jeff’s and the Basmaxx to test and compare to.  
Get some popular touring sound subwoofers.
In other words, make it something that makes sense for us to do.


You are welcome to attend.  See the link below for more information about what we do and who's planning to be there.


Tom Danley wrote on Wed, 01 August 2007 09:53

It would be logical to bring a couple SH-50’s to put above the subs too don’t you think?


Top boxes are most welcome for the listening portion of the event.  Subs don't sound like much without them.

Tom Danley wrote on Wed, 01 August 2007 09:53

The possible subs would be the TH-115, TH-215, TH-50, a new one and possibly even the Matterhorn in case you go for most/lowest bass from “one box”.


Bring anything you like.  But please decide and write in with your plans because we have to set the schedule.  We want everyone that attends to be able to have their equipment measured.

Tom Danley wrote on Wed, 01 August 2007 09:53

I don’t know if it would be fair to compare the TH-115 to the Pi, it is half the size and weight, yet its measurements suggest it would still be ok.


Lots of equipment of various sizes will be measured.  Even though this event is called a "shootout", it is really a fact finding event and no one is really declared a winner.  We simply measure the equipment and post our findings.
Title: Re: Push pull configuration for LAB Horn?
Post by: Todd Michael on August 16, 2007, 09:47:55 am
Hi Wayne,

This is a direct copy of an exchange you had with Tom, it was either on this forum or AA I can't remember. It was just after the design was completed and the first production batch of woofers was being made at Eminence.

 > Why would I go on a public forum like the LAB, where there are
> > some 50,000 people looking on, in the heart of one of our
> > companies business, then say "I can make a bass horn that I say
> > will stomp any similar sized VC driven horn out there",
> > then turn over a design for one and get a driver manufacturer
> > (Eminence) to make a "perfect" driver to order for it to boot.
  

Are you saying that, here and now? Do you think this horn of yours will "stomp" every other VC driven bass horn out there?

I would say that given that the driver(s) is near the edge of what can be built and exactly suited to the job that it will be hard to beat
so far as its acoustic power vs size and input power. Even at 30 Hz, the excursion limit is a huge acoustic output (14mm linear Xmax)


You ask me "why." So I'll tell you what I think. If you have said that then I suppose you are either very confident or very
arrogant. Honestly - and no offense because I use Eminence too and like 'em - But if you think that an Eminence based
product will "stomp" similarly sized offerings using more expensive drivers then it isn't confidence, Tom.
It's arrogance.


We will see.


 > Why would I go as far out on a technical limb as you feel I and
> > discuss the design with hundreds of people at AES and other trade
> > shows if it is bogus?


I dunno. Attention? Arrogance? You tell me.
maybe you're just excited about it. That would be a much nicer thing to believe. Yes, that's it. You're just excited about it.
(But Tom, "stomp any similar sized VC driven horn out there?" With a hundred and fifty dollar woofer? Come on.)


Again, time will tell and soon

> > Why would I do all this when so many of our customers do have test
> > equipment, measure speakers themselves and would easily find out
> > if it was not real?

OK. I give up. What the hell are you doing?!! Are you crazy, or what?!!

Or what....
 > Either I had to be pretty sure about what I was saying or not care
> > at all what happens if I am wrong, I can tell you it isn't
> > the latter.


So, yeah [snicker], that Eminence-powered LAB horn is going to just bust everything else right off the market. Why even
think about any other bass horn? Forget Altec, JBL and TAD. Here comes the LAB!!!



Now to me it sounds like you were pretty negative about the design and what it was capable of doing and you certainly do not sound like you would ever be interested in making a similar design of your own. Yet here we are now and lets face it, your 12pi is a LAB horn made a little wider and one woofer turned around, oh! and some aluminum heat sinks.

And as for me asking what you would make. I asked you if you were given the task of designing ANYTHING to meet the performance requirements that were set by the group of people on the LAB at the start of the project what would you have deigned instead? And I remember you saying you would not make a bass horn of any kind but rather a bass reflex system, which you thought would be much better for the task requirements at hand. It was not a challenge rather a question to see what you would do if you were in Tom's shoes. I really doubt based on your attitude in the exchange between you and Tom above that the 12pi is a direct result of that "challenge".

Wayne if I know you you will now reply with a response saying how this is not how it happened and it was taken out of context, and that I am saying this just because of the relationship I have with Tom. But in my opinion I think anyone that has followed this LAB project from the start up to now it is very clear that you did nothing but try and shoot holes in the design right from the word go. And now here we are years later and you have a product (which I am sure is very good) which is very similar. Yes you can argue the benefits of your push/pull design and heat sinking all you want but the foundation of your design is based on the LAB sub.

Todd Michael





Title: Re: Push pull configuration for LAB Horn?
Post by: John Roberts {JR} on August 16, 2007, 10:48:39 am
Todd.. I will reply with, what is the point of this?

I believe the vast majority here have already formed their own personal opinions about these two gentlemen.

I see no reason to prod them to continue these dueling monologues. Do you expect anything to change?

Why not let sleeping dogs lie. It was quiet for a fortnight.

JR

Title: Re: Push pull configuration for LAB Horn?
Post by: Todd Michael on August 16, 2007, 11:34:29 am

Yes I would agree most have already formed their own opinions about Tom and Wayne.  I was simply trying to set the record straight, especially about Wayne's reference to me "challenging" him to design a bass horn.

Do I think this will change anything? No, but that was not my intention in the first place.

Woof, woof......

Todd
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on August 16, 2007, 05:15:56 pm

Todd Michael wrote on Thu, 16 August 2007 08:47

Wayne if I know you you will now reply with a response saying how this is not how it happened and it was taken out of context, and that I am saying this just because of the relationship I have with Tom. But in my opinion I think anyone that has followed this LAB project from the start up to now it is very clear that you did nothing but try and shoot holes in the design right from the word go. And now here we are years later and you have a product (which I am sure is very good) which is very similar. Yes you can argue the benefits of your push/pull design and heat sinking all you want but the foundation of your design is based on the LAB sub.

You're right, I think you've taken this out of context.  You say this like Tom has been the helpless victim of product bashing.  What you and others in the Danley camp fail to see is that you are the ones most guilty of that kind of thing.  You insult your "opponents" rather than having a discussion.  You won't even look beyond your own noses to objectively evaluate what others are saying.  Your goal is to discredit them, hoping to influence public opinion.  It's like you think you're the only ones in the game, and that all others should crawl before your feet.  That's not cool.

I don't know where you got that "exchange" or whatever it was that you posted.  It does express my frustration with Tom, so I could have seen me saying it somewhere.  I do know what is publicly displayed online over at Audio Asylum, where you asked me what I would do instead if I were designing a subwoofer like the LABhorn.  Specifically, you asked, "If the job was yours and you were asked to design (like Tom did) a subwoofer for maximum 30-150 cycle reproduction, to be used under the circumstances that the LAB Horn was designed around, then what would you have designed instead ?"

We were discussing subwoofers for home hifi use and I replied that the solution was indicated by the conditions.  I suggested that a big basshorn might be a big much, and that a single basshorn was acoustically undersized anyway.  Since the LAB12 in a ported box could be made smaller and reach a lower f3, that's what I suggested for that situation.

I later decided to take you up on your challenge and design a basshorn subwoofer "for maximum 30-150 cycle reproduction, to be used under the circumstances that the LAB Horn was designed around".  The 12Pi basshorn subwoofer is my response to your challenge.

I believe that the improvements from features in the 12Pi are significant.  The push-pull drive reduces distortion and the cooling plug reduces thermal stress.  Please look through the links below for more information on the benefits of each one:

With two drive units, my thinking is why not run them push-pull?  What possible reason would you have for not taking advantage of this configuration when there are two drive units anyway?  Measurements at the Prosound Shootout in 2005 showed that distortion was very low, lower than other horns that didn't use push-pull drive.

The cooling plug provides remarkable reduction of temperatures.  As I've said many times before, heat radiated into the pole piece is a woofer killer.  Forced air cooling via gap vents is helpful, but it does almost nothing to remove heat build-up in the motor core.  What you really want is a cooling plug to wick that heat out in addition to gap venting.

I even went to some effort to make the cooling plug compatible with the LABhorn so it could be used on existing devices.

So what exactly is it that causes such a reaction from the Danley camp?  Why is it that every time the cooling plug or 12Pi basshorn subwoofer comes up here that at least one of you that are associated with Tom Danley jumps on to try and squelch it?  I mean, you asked me what I would do.  It's like you didn't like the fact that my 12Pi had some good ideas, like you have a bad case of the "wasn't invented here" syndrome.  That is what has been most frustrating to me when dealing with Danley and his associates over the years.
Title: Re: Push pull configuration for LAB Horn?
Post by: Vince Byrne on August 16, 2007, 06:18:13 pm
Wayne,

I'm not in any camp and have no relationship with Danley or any other vendor. I did, however, follow the LABsub project back in the day and also ran across some of your exchanges with Tom on other forums.
Wayne Parham wrote on Thu, 16 August 2007 16:15

 So what exactly is it that causes such a reaction from the Danley camp? Why is it that every time the cooling plug or 12Pi basshorn subwoofer comes up here that at least one of you that are associated with Tom Danley jumps on to try and squelch it?

What I saw is that back then you rejected nearly every out-of-the-box concept that Tom described out of hand and publicly.

I have no reason to believe your cooling plug and 12Pi don't work as advertised, but they stand on the shoulders of the original LABsub work that Tom gifted to the DYI community and which you so soundly and rather rudely rejected. And now you profit from it too, and advertise it in the forums the LABsub was conceived in. Personally, I would be pissed.

Wayne Parham wrote on Thu, 16 August 2007 16:15

It's like you didn't like the fact that my 12Pi had some good ideas, like you have a bad case of the "wasn't invented here" syndrome.

This rings like when the Vanilla Ice dude was arguing that the Ice Ice Baby bass riff wasn't lifted from Under Pressure. An extra note in the second bar does not make an original composition.
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on August 16, 2007, 07:29:33 pm

Vince Byrne wrote on Thu, 16 August 2007 17:18

I have no reason to believe your cooling plug and 12Pi don't work as advertised, but they stand on the shoulders of the original LABsub work that Tom gifted to the DYI community and which you so soundly and rather rudely rejected. And now you profit from it too, and advertise it in the forums the LABsub was conceived in. Personally, I would be pissed.


Have you ever looked at the Renkus-Heinz CoEntrant horn and compared it with the Unity horn?  They are virtually identical.  Or how about the old Jensen Transflex?  Any similarity to the Tapped Horn?

The 12Pi is completely different than the LABhorn.  It uses a different flare, different throat, different front and rear chambers and different driver configuration.  It uses the same drivers, but the drivers in the 12Pi are modified.  It uses a spiral fold, but so did my 1970's 10Pi, which was a 40Hz basshorn.  So why then would you credit my work as standing on the top of Tom's work, any more than any other work stands on the top of work done before it?

I "met" Tom Danley online in about 2001.  Actually, my first encounter was with Mark Seaton.  These guys were saying the Unity horn was better than any other horn, and attacking other designs.  At the time, their published response curves weren't very good.  They showed a deep notch about an octave above the crossover frequency, so I think probably summing was off in those early models.  I'm not sure if they corrected that or not, but I can assure you that any criticism I've had of Tom's work has been nothing compared to the attacks that he and his camp have given me.  Worse still, what I'm saying about the cooling plug and push-pull drive has great technical merit, yet they've done everything they could to squelch it.  So please don't talk to me about rejecting concepts out of hand and publicly.
Title: Re: Push pull configuration for LAB Horn?
Post by: Vince Byrne on August 16, 2007, 11:55:02 pm
Wayne Parham wrote on Thu, 16 August 2007 18:29

 
Have you ever looked at the Renkus-Heinz CoEntrant horn and compared it with the Unity horn?  They are virtually identical.

Yes, and it's been years but I've read the patents. The base concepts with multiple drivers loading a common horn are very similar. IIRC the Unity patent added the opening spacings along the length of the horn, described how the physical spacing offset group delay in the speakers, and the improvement in phase alignment.

As a (non-audio) engineer, I really admired how this approach addressed phase at a basic physics principles level but I had no idea at the time whether the phase improvement would be significant or audible. Neat idea, but is it worth the effort. When I heard some TD-1s at a seminar I could hear the difference, and it wasn't subtle. Imaging I was not familiar with. I couldn't hear any gack in the crossover bands. Nearly inaudible coverage seams between two hard-packed cabinets. The cleanest coverage pattern I've heard. Pretty cool, definitely worthwhile.

From what I've read I gather that Tom and Ralph respect each other more than a little and see each other as on the same side as point-source advocates.
Wayne Parham wrote on Thu, 16 August 2007 18:29

   Or how about the old Jensen Transflex?  Any similarity to the Tapped Horn?

Nope, I haven't looked at Transflex, and I don't know it's history. I like the physics behind the Tapped Horn, and there seems to be very few others (Bassmaxx is certainly notable) getting comparable output with comparable LF extension. I haven't heard either of these yet, but I'd like to.

Wayne Parham wrote on Thu, 16 August 2007 18:29

   The 12Pi is completely different than the LABhorn.  It uses a different flare, different throat, different front and rear chambers and different driver configuration.  It uses the same drivers, but the drivers in the 12Pi are modified.  It uses a spiral fold, but so did my 1970's 10Pi, which was a 40Hz basshorn.

Hmmm. With reasoning like this, comparing the Unity and the RH Coentrant is like comparing apples and bricks.  Very Happy

From what I've read, those who have 12Pis are very pleased. Bigger in one dimension from the LAB so it doesn't meet the LAB design goals, but not a problem. Spiral fold, nothing new. A bit bigger, of course the design optimizition details will be different. A bit louder, cool. By all accounts an excellent sub.

What is bothersome is that your positioning of 12Pi comes across as a "better LABsub" due to push-pull and cooling plugs. If it did this in the same form factor I would agree, but it's not. It's bigger.

Wayne Parham wrote on Thu, 16 August 2007 18:29

   
So why then would you credit my work as standing on the top of Tom's work, any more than any other work stands on the top of work done before it?

Tom never claimed the LAB was an end-all sub, just that it was a well executed conventional horn design that outperforms many big name commercial products, to specs driven by the user base, at very reasonable cost, and was within the capabilities of DIYers.

12Pi meets mostly the same goals, in nearly the same way. Same base concept, using all of the same criteria except one dimension. Again, by all accounts an excellent sub. But, done after the fact in "me too" fashion, and then placed in competition to the LAB.

Wayne Parham wrote on Thu, 16 August 2007 18:29

   
I "met" Tom Danley online in about 2001.  Actually, my first encounter was with Mark Seaton.  These guys were saying the Unity horn was better than any other horn, and attacking other designs.  


I think I ran across Unity a bit later than that. What I remember (my paraphrase) is Tom saying that he designed Unity in the quest for phase coherence because he was convince that phase was more important than the conventional wisdom thought, and that others would agree with him if they actually experienced it.

You were pretty adamantly opposed to this idea at the time, and it was clear that you hadn't heard Unity horns.

Wayne Parham wrote on Thu, 16 August 2007 18:29

   
Worse still, what I'm saying about the cooling plug and push-pull drive has great technical merit, yet they've done everything they could to squelch it.  So please don't talk to me about rejecting concepts out of hand and publicly.


I think your case for the cooling plug would be much better if you presented data that in a pack of four LABs (or 12Pi) that power handling improves by xxx watts, giving an increased max output of yyy dB.

BTW, how does the plug work with the reversed driver in the 12Pi? Are plugs on both sides still of benefit?

Same thought for push-pull, data would help. Theory says distortion should improve, you have said the improvement is measureable, but I haven't seen any numbers. My guess is that the audible difference going from 50% on a front load to 10% on a LAB   is more significant than going from 10% on a LAB to even 5% if 12Pi gets there.

I have no doubt that the cooling plug moves some heat. Push-pull could lower distortion. Tom felt that the improvements wouldn't be significant. Data from you would help your case.

Title: Re: Push pull configuration for LAB Horn?
Post by: Pascal Pincosy on August 17, 2007, 01:02:50 am
Hey Vince, This has all been rehashed and re-rehashed to death. Over and over and over again. Wayne's had his Pi Horn at both the measurement shootouts he's done and distortion measurements were taken and are available online.

Now I'm not privy to all those early discussions (thank god Rolling Eyes ) and I certainly can't speak for who said what. But this thread after thread after thread about the same stupid stuff is pretty stale and I'm certainly tired of reading it. People need to either kiss and make up, or take it off-line, or at least find something new and more interesting to argue about.

Fact: The Pi horn has less distortion because it uses the push-pull. This makes it wider. Thus it doesn't truck-pack as well as the LAB horn. Compromise.

Fact: Wayne's cooling plug reduces heat buildup in the driver. This is a good thing. Cabinets built in this manner are somewhat less user-friendly as flaps or spacers are needed to allow for proper cooling. Compromise.

What it all comes down to is that Tom Danley built a subwoofer for the LAB, to their specs. Wayne Parham built one for himself, to his specs. They are different speakers made for different purposes. There is no better here.

And who the hell cares if Wayne is trying to "compete" with a free design anyway? Tom's not losing any sleep over it. His company is growing by leaps and bounds, and they don't make a dime from the LAB horn. Like I said, I wasn't around back in the day when this schism started, so to me, it all reads like a pissing contest where the goal is to soak your own shoes.

I'd like to remind everyone of an old chestnut: "Imitation is the sincerest form of flattery." Can we get back to talking about how JBL is the best or how to build a better sub for our Honda's already?
Title: Re: Push pull configuration for LAB Horn?
Post by: Vince Byrne on August 17, 2007, 08:23:01 am
Pascal Pincosy wrote on Fri, 17 August 2007 00:02

Hey Vince, This has all been rehashed and re-rehashed to death. Over and over and over again.

Yeah, I'm done. Wayne asked "why are they picking on me" and I took the bait. As if he doesn't know. I'm so ashamed ...
Title: Re: Push pull configuration for LAB Horn?
Post by: Todd Michael on August 17, 2007, 08:42:26 am
Wayne,

I think, as usual, you are seeing things from your own perspective and nobody else's. First off I never publicly bashed any of your products and I did mention that I thought the 12pi was probably a fine sounding sub. What I "bashed" was you and your attitude towards the LAB sub from day one. It is well documented that you were not a fan of the design or the designer right from the word go. And here you are now with a very similar design and you have never given any credit (that I have seen) to Tom for the work he has done.


I think you should go back and read the AA posts again about what you would build specifically for the LAB, NOT HOME HI-FI, we were not talking about home Hi-Fi applications and I made that very clear. Your answer was a bunch of direct radiator cabinets loaded with JBL drivers.You said that one of the biggest design targets was that it had to be portable and you thought bass horns like the LAB sub were too big to be portable, then you make the 12pi which is even bigger!

The obvious question why did you not make a new product like that instead of making the 12pi?

Next to Tom I'm pretty sure I have done more work with the Unity design than anyone else so I am very aware of its similarities to previous designs. But the difference between Tom and R.H and you and the 12pi and LAB sub is that Tom was never publicly bashing the R.H co-entrant design and then months later came out with the Unity. I think Tom even sited the RH design as previous art in his patent.


 Like I said in my first post you can argue about your push/pull drivers and heat plugs all you want. I am very aware of their benefits and I did not discredit them or the work you have done designing them, again I think you are missing the point.

I can see this just going around and around in circles. I guess you will have your view point and I will have mine of the events that unfolded since the beginning of this project and that is fine.

Todd
Title: Re: Push pull configuration for LAB Horn?
Post by: John Roberts {JR} on August 17, 2007, 10:15:22 am
I continue to be amazed at how much energy people spend trying to change the opinion and behavior of others. I haven't yet mastered changing my own.

It is not surprising that people will have a personal perspective, perhaps colored by self interest. This is just being human.

The past is past and can't be changed with any amount of hand wringing.

Perhaps we can get back to talking about something new or different, and not rehashing the same old nonsense.

JR
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on August 17, 2007, 12:02:22 pm

Todd Michael wrote on Fri, 17 August 2007 07:42

What I "bashed" was you and your attitude towards the LAB sub from day one. It is well documented that you were not a fan of the design or the designer right from the word go.


I wasn't "a fan of the design or the designer right from the word go", that's true.  Well, maybe I should correct that just a little bit.  I didn't have a problem with Danley and his associates at first.  I probably would have liked him just fine and agreed with many of his design principles if we had met on different terms.  But you see, my introduction to Tom Danley was by way of his associate Mark Seaton coming into the Pi Speakers support forum and bashing our speakers, championing his own Unities instead.  So you're right that, at least after that time, I wasn't a fan of the "designer right from the word go".

Todd Michael wrote on Fri, 17 August 2007 07:42

And here you are now with a very similar design and you have never given any credit (that I have seen) to Tom for the work he has done.


Perhaps you didn't read this:


Todd Michael wrote on Fri, 17 August 2007 07:42

I think you should go back and read the AA posts again about what you would build specifically for the LAB, NOT HOME HI-FI, we were not talking about home Hi-Fi applications and I made that very clear.


Maybe you should re-read the posts.  There's a link to them in this thread, so it's easy to do.  It was started by a guy that was building a home hifi sub.  The whole Asylum website is dedicated to home hifi hobbyists.  My position was very clear there, and I have not changed it to this day.

Todd Michael wrote on Fri, 17 August 2007 07:42

Your answer was a bunch of direct radiator cabinets loaded with JBL drivers.


That would be an excellent choice for small venues, like home hifi.  Especially if the goal is use below 30Hz, a direct radiating subwoofer makes more sense than a 30Hz basshorn with the bottom end EQ'ed up.  Just like I wouldn't suggest the LABhorn in that situation, I wouldn't recommend my 12Pi to someone for home hifi, or for use below 30Hz.

Todd Michael wrote on Fri, 17 August 2007 07:42

You said that one of the biggest design targets was that it had to be portable and you thought bass horns like the LAB sub were too big to be portable, then you make the 12pi which is even bigger!


No, I said a basshorn has to be large to work at low frequencies.  One that is small enough to be portable is severely compromised at low frequencies.  Again, for home hifi, it's probably overkill to use a LABhorn or a 12Pi and they aren't designed to be used below 30Hz anyway.  My suggestion was to use a direct radiating sub that was tuned lower.  It would be smaller and have lower f3.

Todd Michael wrote on Fri, 17 August 2007 07:42

Next to Tom I'm pretty sure I have done more work with the Unity design than anyone else so I am very aware of its similarities to previous designs.


The Renkus-Heinz CoEntrant design and the Danley/Yorkville Unity/Summary are exactly the same thing.  I'm sure the patent was granted based on a small detail that Danley claimed was different, but the principle is exactly the same.  If it weren't, one of them wouldn't work.  They are physically similar so they must be configured similarly too.

Especially in light of that, I think it is extremely wrong for you or any other Danley supporter to point to the 12Pi and say it's a copy of the LABhorn.  I spent hundreds of hours working out the details.  It was a significant effort.  There is a considerable amount of design, testing and refinement that was required to perfect the design.

The layout of the motor chambers was completely different in order to support push-pull drive.  The cooling plugs were the result of considerable effort, starting first with a ducted air-cooling system and evolving later into the cooling plug which was much more effective.  Then there was the matter of layout, and how to position everything in the cabinet.  The end result allowed me to make a cooling plug that was simple, and is compatible, allowing it to be used on the LABhorn.  That was a contribution I made to the people here.  But do you give me credit for it?  No, you shrug it off and minimize it.  That's wrong, very wrong.

If you and Tom and other Danley associates want to come here and minimize my efforts, don't be surprised when I do the same to yours.

Todd Michael wrote on Fri, 17 August 2007 07:42

Like I said in my first post you can argue about your push/pull drivers and heat plugs all you want. I am very aware of their benefits and I did not discredit them or the work you have done designing them, again I think you are missing the point.


That's complete BS.  Tom Danley and Ivan Beaver both took a position that they didn't work.  You may not personally have made those comments, but Tom and Ivan did.  They are seen as experts in the field, so when they make statements, sometimes people believe them without checking the facts.  That's not cool.

Tom and Ivan were pretty vocal about trying to discredit the cooling plug approach last year. It was incredible to me, since any competent mechanical engineer that examines the device immediately understands what it does and how it works.

Tom's position was that radiated heat was not significant.  That's not true at all.  Not only was he wrong, but he was rude about how he tried to discredit me and the cooling plug approach.  What he would have found, if he actually did some tests, is that the whole motor core is heated by energy radiated by the voice coil.  One of the most effective things you can do to reduce voice coil temperature is to wick away the radiated heat.  Keep the forced air cooling from the gap vents, and add to it some cooling plugs.

When several hundred watts are applied to a speaker voice coil, it gets hot like a large soldering iron. Even if the speaker system is very efficient, you still have hundreds of watts dissipated as heat. Take a theoretical 400 watt speaker at a very optimistic 50% efficiency level - You still have 200 watts of heat. This heat source is surrounded by steel and then covered by a large chunk of ceramic. This is a pretty good heat container, one that is almost made to hold heat. So one of the best things you can do is to get a good conductor of heat down inside the motor, in contact with the pole piece. Wick the heat out of the core and radiate it away.

It's the most effective thing I've ever seen for removing built-up heat from the motor core.

John Roberts  {JR} wrote on Fri, 17 August 2007 09:15

I continue to be amazed at how much energy people spend trying to change the opinion and behavior of others. I haven't yet mastered changing my own.

It is not surprising that people will have a personal perspective, perhaps colored by self interest. This is just being human.

The past is past and can't be changed with any amount of hand wringing.

Perhaps we can get back to talking about something new or different, and not rehashing the same old nonsense.


I agree, wholeheartedly.  I'm sorry for my part in the deal.  

I've tried to let this die for the past year or two, but Danley and company keep attacking me.  It has been the same since I first encountered them, and I never understood it.  From the first time they rudely came into my forum and started pushing the Unities, I was pretty miffed.  I pushed back, sometimes pretty hard, and maybe that was my mistake.

But I'm not the only one Danley has attacked.  I see him putting down others too.  Sometimes it is an overt attack, like what he does to JBL or EAW.  Other times, it is more like a patronizing comment, one that kind of says "you're OK if you stay in your place" but with the inference that he is king of the hill.  I see this in comments about Bassmaxx and others that participate here.  None of these guys like it, and in most cases, it isn't fair or even truly accurate.  It's spin, and I don't like it.

I make loudspeakers because I love to do it.  I'm proud of my work.  They very good products and people like them.  They are technically advanced and definitely worthwhile, at least in my opinion.  They're my best work.

All of my designs are offered to the DIY community.  I don't have some that are proprietary and others that are open.  All my designs are open.  I don't charge for the plans, even for products that have been developed at great expense of time and money.  This started as a hobby of mine, and just kind of took off.

So I have taken extreme offense to Danley trying to bully me over the years.  How am I to respect a man that acts like that?  Still, I've let things slide for the most part.  Look back through the threads Danley and I have been on in the past couple years and I think you'll see I've been restrained even when being patronized or outright attacked.  So I've let it drop, let it roll off.

I'm happy letting the truth express itself.  It always does in the end.
Title: Re: Push pull configuration for LAB Horn?
Post by: John Roberts {JR} on August 17, 2007, 12:37:21 pm
stop stirring the pot...

JR
Title: Re: Push pull configuration for LAB Horn?
Post by: Ivan Beaver on August 17, 2007, 01:10:06 pm
I have been deliberately staying out of this so not to prolong the thread and was waiting for it to die, but I feel I must step in here, since I was accused directly.

It is not mine (nor Tom's) suggestion that the cooling plugs do not work.  I sure they do help.  It is my thoughts that they do not add all the benefit that is claimed.  Yes I assume it is possible to achieve the results you have regarding the power handling increase that you have claimed. That is not to dispute.

What I have a problem with (as stated in earlier threads) is the test procedure used.  You were using a continuous source and music is far from that.  Music has a higher crest factor than you were using, so the tests were not representative of the real world conditions.  SO the idea that now the driver can handle that much extra music power (and the peaks associated with it-those are the real danger) I feel is in error.

If I am not mistaken, you only burned a couple of drivers.  It takes more than that to establish an "average" or baseline-especially for failure conditions.  1 or 2 is not an average.  I seriously doubt that you burnt say at least 10 drivers with and without your plug.

Yes there are some similarities between the Unity and the co-entrant devices.  Yes they both use the same horn for both bands (except the unity-as in the TD1 was a 3 way device while the RH is a two way device).  The co-entrant used a "waveguide" to get the mids into the horn, while the unity mid path is much shorter.  The unity also has different expansion rates for the highs and mids (and lows as well) which allows the horn to load the different bands as needed.

As a result the unity arrays better up higher in freq, because the walls of the cabinet are closer to the HF driver than in the case of the co entrant.

The crossovers were derived ENTIRELY different.  The co-entrant was just a crossover based on a certain freq-as normal.  The unity has overlapping filters and uses the delay associated with the phase shift of those filters to achieve a flatter amplitude and phase response (the biggest issue in Tom's world).

The holes in the unity are acting as low pass filters on the mids as well.

This is in no way dissing the co-entrant (in fact I think it was one of RH's better sounding boxes), but the basic idea of having all the drivers occupy the same physical place in space is one that has been sought after for many years.  Different people are trying different approaches the get there, some better than others.

In regard to the Jensen, it looks a lot more like a transmission line than a tapped horn.  The "horn" part is missing.  Yes Toms earlier experimental work did look more like a transmission line than it does now.  Of course the new stuff works much better-Just wait!

Back in my hole now. My apologies to those who wanted this to die.
Title: Re: Push pull configuration for LAB Horn?
Post by: Pascal Pincosy on August 17, 2007, 02:04:02 pm
And round and round the broken record goes. Now Wayne will retort with his views on why the cooling plug's testing was great. This is nothing new. We have heard it all for at least a year now.

It's clear to me that these arguments have little to do with science and a lot to do with bruised egos on both sides. If you guys had all stuck to discussing the facts and the science, and left out the ad hominum in the first place, we wouldn't be here today.
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on August 17, 2007, 03:54:53 pm

Pascal Pincosy wrote on Fri, 17 August 2007 13:04

And round and round the broken record goes. Now Wayne will retort with his views on why the cooling plug's testing was great. This is nothing new. We have heard it all for at least a year now.


Seems like it, doesn't it?  I won't rehash how the testing was done, but I think maybe we're getting somewhere on an understanding of the significance of radiated heat and how the cooling plug works.  So please bear with me while I reply to Ivan.

Ivan Beaver wrote on Fri, 17 August 2007 12:10

It is not mine (nor Tom's) suggestion that the cooling plugs do not work.  I sure they do help.


They do help, a great deal.

Tom Danley has maintained a position that radiant heat is not significant and that the pole piece is heated by conduction through the air.  Perhaps you guys are now realizing this is not true.  Most of the heat in the pole piece is radiated from the voice coil, not conducted through air in the gap.  That's important, because if you assume center pole heat comes from conduction through air, then it is natural to assume air cooling will remove all the heat.  It looks like that is what Tom assumed, so I can see why he would think the cooling plug wouldn't be effective.

To be honest, that's how I thought for a long time too.  My first attempt at loudspeaker cooling used a ducting arrangement to improve the forced air convection cooling provided by the gap vents.  What I found was even when the air was made very cool and blown through the gap, it did almost nothing to remove heat from the pole piece and magnet.  Radiated heat becomes a big problem at extended high power levels, because it builds up in the motor core and cooks the voice coil, weakening the adhesive.  But as I said, my first assumption was air cooling would remove all the heat.  I don't fault Tom for this assumption because it is an intuitive assumption to make.


After realizing the significance of radiated heat, I wanted to make this information known, so it could be useful to everyone.  To tell the truth, it made cooling improvements pretty easy.  The cooling plug is very easy to make and implement.  That's the important information I bring here.  I don't think it's anything revolutionary, and certainly mechanical engineers look at it and say "duh".  It has been overlooked, I think, by some.  That's why I have said it here.

Some heat is removed from forced air convection through the gap vent.  But a lot of heat is trapped in the motor core that cannot be effectively removed by forced air convection.  That's because it is radiated into the pole piece and magnet in the first place.  To get it out, the best way to do it is to conduct it out with something in direct contact with the pole piece.  That's why the cooling plug works so well.  Best to do both, air cooling through the vents and heat wicking using a cooling plug to some sort of heat sink.

Ivan Beaver wrote on Fri, 17 August 2007 12:10

It is my thoughts that they do not add all the benefit that is claimed.


What is claimed is that cooling plugs reduce temperature in the motor core, and all the benefits this brings.  Specific measurement data has been provided.

Ivan Beaver wrote on Fri, 17 August 2007 12:10

Yes I assume it is possible to achieve the results you have regarding the power handling increase that you have claimed. That is not to dispute.


So which is it, Ivan?

On one hand, you say you're sure they do help, and you assume the power handling increases when using them.

On the other hand, you say they might not add all the benefit that was claimed.

What is claimed is that cooling plugs reduce temperature in the motor core, and all the benefits this brings.  The temperature reduction is significant.  It stabilizes electro-mechanical parameters, reduces compression and makes the speaker more robust and durable.

Ivan Beaver wrote on Fri, 17 August 2007 12:10

What I have a problem with (as stated in earlier threads) is the test procedure used.  You were using a continuous source and music is far from that.  Music has a higher crest factor than you were using, so the tests were not representative of the real world conditions.  SO the idea that now the driver can handle that much extra music power (and the peaks associated with it-those are the real danger) I feel is in error.


Tell you what.  Make one and test it for yourself.  Get some aluminum tubing from McMaster-Carr and lathe it to fit.  Give it a try and see what you learn from it.

Pascal Pincosy wrote on Fri, 17 August 2007 13:04

It's clear to me that these arguments have little to do with science and a lot to do with bruised egos on both sides. If you guys had all stuck to discussing the facts and the science, and left out the ad hominum in the first place, we wouldn't be here today.


That's absolutely right, Pascal.  Let's stick to discussing the facts.  The data speaks for itself.
Title: Re: Push pull configuration for LAB Horn?
Post by: Grant Rider on August 27, 2007, 12:42:48 pm
Since even the naysayers have agreed that cooling plugs and push pull woofers are improvements I'm not sure what there is to argue about. I missed a lot of this but what I see looks petty as hell. The protestations here remind me of Topsy the Elephant.
Title: Re: Push pull configuration for LAB Horn?
Post by: Tim McCulloch on August 28, 2007, 02:01:25 am
Thank you for that stunning insight into subwooferdom.  Please drive thru.

Tim Mc
Title: Re: Push pull configuration for LAB Horn?
Post by: Grant Rider on August 29, 2007, 11:32:27 am
Tim McCulloch wrote on Thu, 23 August 2007 15:30

30 years ago *we* got our start the really old-fashioned way: at the library.  It's the lack of preparation that probably chaps my ass more than any other single thing.  Posting a few questions on internet forums is NOT research, studying, or preparation, although it might lead to that...

Good suggestion. Check the air in your tires.
Title: Re: Push pull configuration for LAB Horn?
Post by: Tim McCulloch on August 29, 2007, 02:18:56 pm
Grant Rider wrote on Wed, 29 August 2007 10:32


Good suggestion. Check the air in your tires.


Always a good idea.  Safety and economy.

Tim Mc
Title: Re: Push pull configuration for LAB Horn?
Post by: Grant Rider on October 11, 2007, 11:59:30 am
 http://srforums.prosoundweb.com/index.php/mv/msg/24934/25264 1/0/#msg_252677

Tom Danley admits to "a certain friction which goes way back" but says he "was thinking of sending a new box (to the Tulsa sub shootout) but the first samples, while impressive sounding, were I felt too far short of the computer model".

Maybe we are seeing an end to the friction?

Tom Danley wrote on Tue, 09 October 2007 23:49

I have sent speakers to shootouts before and think proper measurements and side by side comparisons vital in getting to reality.  Personally Wayne and I seemed to exhibit a certain “friction” which goes way back and my daughter has surgery that weekend so I couldn’t go anyway.
I was thinking of sending a new box but the first samples, while impressive sounding, were I felt too far short of the computer model.    I (hope) figured out what wasn’t right and have a second set in the works.  These boxes should in a stack of 4 have about 10dB of forward directivity gain in addition to sensitivity and a lower cutoff, but hey, they aren’t measured yet.


Title: Re: Push pull configuration - measurement data
Post by: Wayne Parham on October 25, 2007, 12:28:38 pm

I've compiled some data that shows the benefits of push-pull drive.  Response and distortion charts taken from the last few Prosound Shootouts are lined up side by side for easy comparison:

Title: Re: Push pull configuration for LAB Horn?
Post by: Ivan Beaver on October 26, 2007, 07:21:13 am
The 2nd version of that model Tom was talking about works much better.  It is 30Wx48Tx26 deep (smaller than a lab sub and easy to move and great truck pack).  Output @30Hz with 2.83V input is over 102dB.  Combine that with 2000watt RMS power and you have an idea that it will get VERY loud and low!
Title: Re: Push pull configuration for LAB Horn?
Post by: Wayne Parham on October 26, 2007, 10:58:41 am

Ivan Beaver wrote on Fri, 26 October 2007 06:21

The 2nd version of that model Tom was talking about works much better.  It is 30Wx48Tx26 deep (smaller than a lab sub and easy to move and great truck pack).  Output @30Hz with 2.83V input is over 102dB.  Combine that with 2000watt RMS power and you have an idea that it will get VERY loud and low!


Too bad you didn't bring it to the Prosound Shootout.  Would have loved to see you there.

Did you notice how little distortion the 12Pi had?  Even when pushed to extreme power levels, the distortion is down at the levels of the noise floor.  Most basshorn subs have distortion that's louder than the fundamental at very low bass frequencies near horn cutoff.  The 12Pi doesn't, distortion remains low at high power even at the deepest bass frequencies.  I think that clearly shows the benefit of using push-pull drive.

One thing you notice right away is how most horns make a throbbing, whooshing, sometimes a thumping sound way down low.  I'm not talking about the jackhammer sound of the voice coil hitting the plate, I'm talking about LF distortion.  It is pure distortion, down way under the horn cutoff frequency where the fundamental is very quiet but harmonics are amplified by the horn.

The 12Pi basshorn is dead quiet when driven by signals under cutoff.  When the frequency is raised into the passband, the horn comes alive.  No distortion.

Most people don't run basshorns under the flare frequency.  Some do.  But everyone runs them down as low as possible, and the distortion reduction from push-pull drive is clearly evident in the passband, especially at the lower end.  I don't think I'd ever build a basshorn with two drivers that didn't use push-pull drive.  That's one of the biggest advantages of having two drivers, in my opinion.