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Author Topic: Push pull configuration for LAB Horn?  (Read 17500 times)

Josh Billings

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Re: Push pull configuration for LAB Horn?
« Reply #20 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
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Tom Danley

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Re: Push pull configuration for LAB Horn?
« Reply #21 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


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Wayne Parham

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Re: Push pull configuration for LAB Horn?
« Reply #22 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.
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Wayne Parham
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Todd Michael

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Re: Push pull configuration for LAB Horn?
« Reply #23 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





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John Roberts {JR}

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Re: Push pull configuration for LAB Horn?
« Reply #24 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

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Todd Michael

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Re: Push pull configuration for LAB Horn?
« Reply #25 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
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Wayne Parham

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Re: Push pull configuration for LAB Horn?
« Reply #26 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.
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Vince Byrne

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Re: Push pull configuration for LAB Horn?
« Reply #27 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.
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Wayne Parham

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Re: Push pull configuration for LAB Horn?
« Reply #28 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.
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Vince Byrne

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Re: Push pull configuration for LAB Horn?
« Reply #29 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.

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