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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: Josh Billings on July 06, 2006, 10:06:37 pm

Title: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 06, 2006, 10:06:37 pm
I'm thinking about building 4 matching subs and i'm curious if this heat exchanger really help that much and if the push pull design is a better idea? Anybody A/B these speakers?

I've heard great things about the 12pi and it had AMAZING results at the shootout

Let me know your thoughts

http://www.prosoundshootout.com/

http://www.pispeakers.com/catalog/product_info.php/products_ id/262

-Josh Billings
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 11, 2006, 08:29:14 am
200 Views and no responses?
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Gareth James on July 11, 2006, 08:55:03 am
Hi Josh,

I think the key thing here is to realise what the 12pi sub is. It is basically a scaled up Labsub with slightly longer path length and greater mouth area to allow it to reach slightly lower frequencies. IMO the size difference (labsub being around 2/3 the size) doesn't warrant the extra few hz (but as said thats just my opinion).

The design is also "different" in that it incorporates the heat exchanger basically linking the rear of each driver to the aluminium plate for greater heat sink action. One of the drivers has been reversed as well to create a push-pull system to help cancel even harmonic distortion.

Seeing as the original Labsub was measured (correct me if im wrong) less than a few % throughout its useable range, i doubt you'd hear any kind of dramatic sound quality improvement.

As to the heat exchanger, i doubt the touted 3dB powerhandling increase would still be in effect once multiple subs were stacked on top of each other.

I would very much like to see recorded measurements for 4x/6x Labs vs 4x/6x 12pi's, i doubt there'd be much difference although i wouldn't want to be stacking the pis.

I guess to conclude, the labsub was a free design given to the community by Tom Danley. "12pi" sub RRP $2800 or so if i remember correctly.... Rolling Eyes
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 11, 2006, 05:36:11 pm
The 12pi plans are free too, i just got a copy and we were gonna build. I actually only have space to run two subs so i was thinking about these instead of LABS because everywhere i hear the LABs need 4 to do what they are supposed to do

-Josh Billings
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Al Limberg on July 11, 2006, 08:18:37 pm
I think it would be a much more reasonable statement to say you need four to reach their maximum performance potential.  Even running just a pair (preferably as a center cluster and from an aux) will still outperform an equal or greater truck space volume of double eighteens.  The only adjustment I typically make when running less than four is to raise my HPF to 32 or 36hz depending on how hard I expect to run them.

Al
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 12, 2006, 09:00:18 am
As a pair though the 12pis should go a little lower and louder correct? I think with the large mouth for me just using 2 it makes more sense to build these

+ the added power handling is handy

-Josh Billings
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 12, 2006, 11:16:07 am

The 12Pi hornsub actually has several improvements, all of which I think are significant.  I originally intended to focus mostly on reduction of harmonic distortion using drivers with shorting rings and had Eminence build some prototype drivers.  I later decided to go with the push-pull arrangement instead, because it works better at very low frequencies.  I also wanted to make the response curve flatter, because I thought some improvement could be made there, particularly when small numbers of subs are used.  The heat exchanger designed for the 12Pi is another thing that provides significant improvements.  You can see test data at the links below.

To be very honest, I originally intended to make the 12Pi horn have an entirely different internal shape, largely to ensure there would be no comparisons between the LABhorn and the 12Pi other than performance.  But as I began to layout the final shape, I realized that I could make the 12Pi heat exchanger available to LABhorn owners as a bolt-on upgrade if I laid it out similarly.  LABhorn owners can simply buy cooling plugs or go to a machine shop and make their own and install them on their existing LABhorns.  I did this in the spirit of cooperation.  In my opinion, it doesn't make any sense to run a LABhorn or a 12Pi basshorn without cooling plugs because the price/performance ratio is extremely high.  Just bolt on a couple of plugs and the motors run much cooler.

Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 12, 2006, 11:25:57 am

The 12Pi is only 5.5" wider than the LABhorn.  The 12Pi basshorn fits nicely in semis, having truck pack dimensions.  And stacking is no problem, just space them apart with a 2x4 to allow airflow between boxes.  If you already haved LABhorns, you can easily add cooling plugs, as many people already have.  The difference in motor temperature is significant, as is the reduction in the number of burned voice coils after heavy use.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Tom Danley on July 12, 2006, 06:00:40 pm
Hi

Is the pi an upgrade to a lab?
Better it is to ask what is a labsub first?
Some time ago, in a live audio forum far away, a bunch of people were talking about building some traditional bass horns, “W” bins.
I like DIY, was disgusted with several “big name” horn subwoofers on the market and had some casual rules at my job at the time (Servodrive) so I offered to take a whack at a “modern” horn alignment and a rough layout,  based on the cumulative inputs from the participants here on LAB.
The group decided on the standard truck pack dimension of 45 by 45 by 22 ½ inches this was as large and heavy as anyone wanted to move around.  A group of 6 should be good to about 30 Hz, it should be as powerful as possible.

Using the modern horn math was where Wayne first popped into the lab sub picture, over on the Audio Asylum forum.   He was first criticizing the use a horn for this project (low  frequency) and then of the Marshal Leach’s math (which I used as a starting point) vs the older hifi lore approach (of a low mass driver etc).  
A search of the archives there would be humorous if your bored.
Anyway, I derived a set of driver parameters for what would be a “modern” driver alignment and laid out the horn similar to another one I had designed, the Servodrive BT-7 which worked well.
The driver was not a stock part or close to any stock driver at the time, this was a problem.  I posted the needed parameters so any speaker company could make a driver for the project.
As this was not a company asking for a new driver but rather an internet forum, only one company ended up actually being both willing and able to make a driver.    
I have to hand it to Jerry at Eminence for stepping up to the plate on a speculative driver for the project.

Wayne, somewhere along the line “converted” to the view that maybe the heavy lab sub alignment /driver might work, he has made a somewhat larger version, the pi 12.

However, his measured curve for one pi 12 and 1 measured lab sub are only about 1 dB different at most, the measured lab sub is nicer than his model of it fwiw.

The push pull driver arrangement has the same advantage that a push pull transformer does, it reduces the (drivers electromechanical portion) of the 2 nd  harmonic (which is also the least audible of all of them) but does not improve the others or any of the odd (most objectionable) ones, hence it is rarely considered worth the bother.

Part of the reason for the odd front volume shape /size on the lab sub is that by lowering the upper passband limit with the un obvious acoustic low pass filter, one can reduce all the higher distortion components (at a given output level) at the same time.

Under some duty cycle conditions the cooling plugs probably increase the long term power capacity.
Under other more musical, dynamic conditions (pink noise has a Peak to Average ratio of only 6 dB, even compressed FM rock is more like 10dB P/A) with larger dynamic ranges it would be unlikely to have a significant effect.   It only takes seconds to smoke a voice coil and bass signals are more like large amplitude, low frequency tone bursts.

This is a DIY project, one can layout a different horn of course if you have a different space, one fellow (Brad I think his name was) did that with 4 or 6 at a Church or something I think.     If you search the archives here, one finds the acoustic dimensions and such are given if you want to roll your own horn and this is / was a DIY project.
As long as you keep the throat area and front / rear volumes in the neighborhood, the lab sub driver / horn alignment works.
Heck, Wayne went from being a vocal critic of the premise, the basic design philosophy and driver on the A.A.,  to now occasionally promoting a close copy of it and his website here so I guess that says something.

Lastly, keep in mind the idea behind this was using a modern design approach, to make a VERY powerful subwoofer for “live sound” that keeps up with / beats 95% of the other subs available at any price, that you can build yourself.  
Many have found the lab to be more than they expected so far as acoustic power.
Wayne’s box would be very powerful too.
Hope that helps,

Tom Danley

Danley Sound Labs

Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 12, 2006, 08:43:57 pm
The one restraint i have is that i ONLY have room for 2. I have a tiny 5x8 trailer and i do shows of about 300-500 people or so. I like the labs, but orginally these were build wrong and i'm starting to get air leaks and the cabinets are making a creaking noise and the guy who build them never put t-nuts in for the access panel and a whole bunch of crap was done wrong.

So i was going to get a new pair built but when i saw the 12pi the specs looked great. The 30" wide however is a little much. I know barely get the LABs through the doors (my casters suck). I guess i can get there through but it would be a snug fit.

How much extra do these things weigh?? ANy idea?

I also have to do 1 per side, so i figured the 30" wide mouth would be huge for that extra mouth area and lower hz.

I was going to do 4 dual 18s because they would take up the same (if not less space) but i woudl need 4x the amplifier power to do it right ( i figured 4 PLX3402s bridged when i really only need 1 right now) That also requires extra circuits and stuff that gets complicated for a mobile rig.

I love bass, but i love my back too, if the 12pis are going to be signifigantly heavier i'll probably just build the LABs with the cooling plugs.

-Josh Billings
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 12, 2006, 08:45:08 pm
P.S. It's an honor to have you respond to one of my posts Mr. Danley, without you i would be stuck with Cerwin Vega bass.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Al Limberg on July 12, 2006, 08:46:42 pm
Cerwin-Vega Bass  - isn't that an oxymoron??

?;o)
Al
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Ivan Beaver on July 12, 2006, 09:14:50 pm
He did say bass and NOT sub bass Laughing   It is all a matter of what freq.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Josh Billings on July 12, 2006, 11:06:28 pm
ha
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Bogdan Popescu on July 13, 2006, 03:21:30 am
I always try to get the original not the copy

Besides, the LABsub is already heavy enough, i wouldn't add any kg there, it is tested, documented and has a great support on this forum.

...and one should not come to the LAB-forum and advertise his site and products !!!

Bogdan
owner of 8 LAB's
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 11:09:42 am

I have used McBean's Hornresp program for designing horns practically since its introduction, and its results are consistent with Leach's math.  So what Mr. Danley has said is incorrect, and looks mostly like sour grapes.

The things I didn't like about the LABhorn - from the start - were its physical size and its dips in response, neither of which were good for home hifi.  Audio Asylum is largely populated by home hifi enthusiasts, and a basshorn sub isn't practical for most of the people there.  I also thought Danley was being overly commercial at Audio Asylum, having absolutely no DIY designs available at the time, essentially just marketing the Unity and other SPL products.  Since I was a financial contributor and sponsor of the website, I objected to Tom's blatant commercialism there.  Basically, I thought his posts were free advertising.  Since no plans were offered for any of the designs he frequently proposed, Tom's suggestions could only be taken by actually purchasing his products.

The plans for my designs have always been offered for free, and while I applaud the LABhorn design for what it is, I have improved upon it in the 12Pi basshorn sub.  The cooling plug has been designed to be compatible with the LABhorn, and this provides a significant and easy-to-use improvement for existing LABhorns.  It was done in the spirit of cooperation and many have taken advantage of it, installing cooling plugs in their horns.

If building new, I would suggest building a 12Pi hornsub, since it provides greater output, better response, reduced distortion, and greatly improved thermal performance, making it a much more robust and durable horn.  It is the same weight as a LABhorn, only 5.5" wider and loads nicely having truck pack dimensions.

If you already have existing LABhorns, you can greatly improve them with the simple addition of cooling plugs which are very easy to bolt on.  The addition of cooling plugs will at least make the LABhorn as durable as the 12Pi.  That one simple addition - which I have desgned to make very easy to do - will give your LABhorns a huge improvement with very little effort or cost.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 11:23:20 am

The 12Pi is only 28" wide, so it easily fits through 30" doors.  The braces are cut to save weight and so 12Pi basshorns weigh about the same as LABhorns.

If starting to build, I would suggest 12Pi basshorns because they provide greater output, better response and reduced distortion in addition to the thermal benefits offered by the cooling plugs - This is especially true if you are planning to run only two horns.  The 12Pi basshorn will definitely work better for you.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 11:38:46 am

Did you use aluminum plates for access panels?  If so, you should have a machinist make cooling plugs for your horns.  They bolt right on, a very easy install.  And the difference in performance is incredible.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Tom Danley on July 13, 2006, 01:30:12 pm
Hi Wayne

To be clear, Mc beans program models the response of a given horn and driver.
Your confusion lies in the fact that this program is unrelated to Marshal Leach’s math we had discussed.   That has nothing to do with modeling a physical horn but rather choosing what driver T&S parameters are suited to a given  (ideal size) horn and visa versa (our disagreement based on the fact that you preferred the old light cone way, remember?).  Mcbeans program is not at all what Marshal’s math describes or is for.

Wayne, my background is DIY, if read my olds posts, often you see I am answering technical questions about how things work, not promoting a product.  This is partly a result of a promise I made to a mentor 35 years ago.
None of my products (except for the contrabass) have ever even been for sale to the end user,  I don’t know of a single instance where a DIY’r went out and bought one of my products as a result of a post or answering questions etc and your right, I had no plans for sale but my advice was always free.
If you read the LAB sub development posts, I explained essentially every detail and strategy of what went into it so what the heck do you want?

Also, If not for your vigorous efforts in the very beginning to discredit the Unity horn on AA (also without benefit of ever hearing one) there probably would still be a DIY version that was offered by my friend Nick at Lambda acoustics.
My posts and introduction to you were in trying to correct the nonsense you were spouting and then trying to explain how it worked to you and why phase / time mattered.
If you saw Pat Brown’s technical review of the SH-50 in Live-sound a couple months ago, you will finally see for your self from the independent detailed measurements that the horn arrangement REALLY DOES WORK as described, unlike anything else in pro sound, it also preserves the input waveshape.

Lastly your statement “If building new, I would suggest building a 12Pi hornsub, since it provides greater output, better response, reduced distortion, and greatly improved thermal performance, making it a much more robust and durable horn. It is the same weight as a LAB horn, only 5.5" wider and loads nicely having truck pack dimensions.” seems like at a minimum, blatant BS / wishful thinking / marketing spray, to me.
In the real world (to be taken seriously) one would have had to actually compared the two side by side and measured them.  Clearly, you have not actually built a labsub,  your measured response of a real pi 12 is a 1dB or less typically from a measured Lab sub, as I have mentioned many times, your computer model seems to overstate the “Q”s.
Conversely, one can do a much detailed acoustic model of the pi 12 than McBeans allows you know.
Even then, it would depend on what you wanted to do with them.  
For example, in a system of 8 labs, only 6 pi’s fit in the same truck space.
Which has more peak capacity, more displacement, 16 drivers or 12 drivers?
You larger rear volume allows Xmax to be reached at a lower input power (fwiw, not good), your larger front volume costs you efficiency in a large array.

I will grant you that the aluminum plug would increase the steady state power dissipation, assuming the aluminum cover plates were free to convection flow the heat away.
In a stack, where the plates are blocked off from convection, there would be MUCH less improvement and in either case, with typical music as the source, I wonder “how much” it really does, of course that’s another round of measurements where you would need to have a real Lab sub to compare to.

So far as “sour grapes” maybe there is an element of that, your vocal effort ending in killing the DIY Unity back then made me angry, I was pleased to be able to wangle that agreement out of my boss and thought it would be cool to have that available for DIY, so did your  bashing of the Lab sub design process vs the traditional “Lore” on AA.
Clearly from a historical perspective you have a problem with me and what I design and at this point I guess I am heartened by that, I figure I must be on the right track.
 
Personally, I think you have an amazing nerve to frequently come here to the Lab sub forum and promote YOUR  Pi forum and Pi 12 when you have also pulled posts on your forum which point out errors in your claims.
You haven’t picked up on this yet but frequent blowing of ones horn (promotion) gets annoying, it is way better to make good stuff that customers talk about.
If this were my forum, I would say if you want to advertise your Pi forum, Pi 12 or Pi plans here, go buy a banner ad (like we did).
Cheers,

Tom

Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: John Roberts {JR} on July 13, 2006, 01:42:44 pm
Sorry that you have to waste your time responding to this stuff. I think most here know who the real deal is.

It's human nature to be defensive of one's designs. It takes a little ego to tackle great tasks. Thank you for being so civil in your response.

Cheers,

JR
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 01:58:09 pm

The push-pull configuration has been shown to reduce distortion, incorporated by very well respected people like Dr. Linkwitz, EAW, etc.  Any mechanical engineer will confirm that the heat exchanger provides much better cooling than air venting alone.  This, combined with the fact that I went to great efforts to make the cooling plug design compatible with the LABhorn makes your discounting of these things particularly irresponsible, in my opinion.  It has been shown to be very effective, and I think your going to such great lengths to discount it is purely ego driven.  The fact is that lots of people have suffered from LAB12 failures that immediately stopped once they installed cooling plugs.

On a personal level, I'm about sick of this crap from you, Tom.  You're a smart guy, and have done a lot of good work.  So why you've acted this way is beyond me.  You often describe yourself and the companies you work with as "Davids" set upon by industry "Goliaths".  But where you and I have been involved, you're  the one that has been the predatory "Goliath" and I think you should look at that.

Look at the history -  A few years back, I ran a little DIY business that sprung out of my passion for audio, and you were the main guy at ServoDrive.  We really operated on two different levels.  You sold commercial products. I provided free loudspeaker plans and discussed them with hobbyists.

I had several good speakers with plans available at that time, and I still do.  My speakers were popular, sounded good and people were satisfied.  I still have those same speakers available, and people still love them.

You and Seaton started promoting the Unity over on my forum, and barraged us with several posts about it.  I haven't followed your progress with the Unity since then, but frankly, that version sucked.  It had a huge 15dB spiked dip, obviously a crossover anomaly about an octave above the crossover frequency.  Summing was bad, and I said so.  You attacked other loudspeakers, but your own loudspeaker sucked.  The design probably had potential, and you were proud and all, that's fine.  But the implementation sucked and you shouldn't have attacked people when your own product was that poor.

You similarly championed the LABhorn, sort of forcing it down people's throats.  Most of the guys you were talking to ran tiny power tube amps.  They didn't need or want something like the LABhorn.  But you railroaded that thing and some people took offense.  Frankly, the most vocal opponents to the LABhorn were Edgarhorn supporters, not Pi Speakers enthusiasts.

Seems you've never let go of those controversies.  I've tried to move on and treat you like a gentleman, but you seem bent on keeping a fight going.  It is so bad that you criticize things you know better, things that you know work well.  The push-pull configuration reduces distortion and you know it.  But instead of saying that, you criticize it because you are still hanging on to sour grapes.  That does a disservice to all those that look up to you.

And the worse thing is how you've discounted the cooling plug.  On that matter, I'm not sure if you know it works and just discount it out of spite, or if you really don't understand heat transfer.  You're a smart guy, but you're not a mechanical engineer.  It is possible that you don't know how much effect black body radiation has on the heat transfer inside the motor.  It's not really your field of expertise, and even if you get a patent on something, that doesn't make you expert in the field.  It just means you've done something (for right or wrong) that no one else paid the PTO to register as being novel.  But whether or not you understand the significance of this, you could have tested it and your discounting it without testing is extremely irresponsible.

Next time you post something about the cooling plug, consider running it by a degreed mechanical engineer.  People look up to you here, and you've promoted yourself as a "Myth Buster".  So I'd appreciate it if you'd stop spreading so many myths of your own.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Gareth James on July 13, 2006, 02:00:51 pm
Wayne the 12pi pushes the lab12 driver harder than the original labsub design. IMO too hard.

The "dip in response" which you are always referring to as having been part of your reasoning for "designing" (note the loose use of this term) the 12pi appears quite less pronounced in actual measurement. The effect it has on adequately damping the driver at very low frequencies still remains however whereas your 12pi horn only increases distortion for little gain.

I had no idea that there had been a DIY unity horn in concept, to learn that you had involvement in its undoing irritates me somewhat.

I blow my nose at you!



EDIT: Wayne as Tom already explained in a calm and reasonable fashion, the push pull configuration only reduces EVEN harmonic distortion and as I already mentioned in another post the original Labsub design wasn't exactly high in distortion. In fact maybe your push-pull design almost makes up for the extra excursion the drivers are dealing with in the 12pi.

As far as the cooling plug, as (once again) Tom has already explained quite adequately musical signals do not bear much if any resemblance to steady state signals. Drawing comparisons from measurements using steady state signals cannot be accurate. The cooling pipe may wick heat away over long periods but during a short burst of energy the only cooling going on will be the voice coil directly giving off heat to its immediate surroundings.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 02:11:27 pm

As I am irritated with anyone that discounts serious design efforts prior to honest examintation.  I suggest you consult a degreed mechanical, electrical or acoustical engineer before making attacks on things that you have not properly investigated.  As an example, go find a degreed mechanical engineer and ask them about the heat exchanger idea, see what he says.  Then go get a napkin for your nose.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Gareth James on July 13, 2006, 02:19:55 pm
Wayne I can't be bothered answering you on 2 posts so I shall concentrate my efforts on this one. As I thought I'd already explained clearly, my points were taking into account your meticulous tests and the fact that steady state power is not an accurate representation of power handling.

I wasn't entirely discrediting your idea. I just don't believe the extra long-term wicking power of the heatsink will aid the staying power of the voice coil with large musical peaks as much as it would with a constant signal.

I'd also be pretty suprised that if the fellow who managed to burn 16 labs multiple times didn't also learn to turn it down a notch eventually. As real as real world performances get its still impossible to subjectively analyse the results of one evening to the next, there will ALWAYS be differences.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 02:24:08 pm

You haven't tested the cooling plug.  I have.  The fact is that it significantly increases power handling and reduces thermal compression.  Bass is bass, and power is power.  The motors get hot, and whatever you can do to cool them down helps a great deal.  Again, go ask a mechanical engineer about this concept.  Or build some cooling plugs and try them out.  Or both.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Gareth James on July 13, 2006, 02:54:33 pm
Wayne as I thought I'd made clear what feels like a few dozen times now, I'm not debating the fact that a large heatsink will aid long term cooling. Yes you have indeed performed AFAIK one destructive test involving 2 woofers (hardly definitive evidence) but using cycled sine waves.

As you said yourself the woofer fitted with the heatsink was still suffering from power compression artifacts above 500w or so. How can you say then that the motor has had its (useful) power handling more than doubled?

I would like to see more conclusive/exhaustive/whatever testing of your device, although I admit I'm not sure how that could be accomplished. I am simply making the point that the electrical power handling of the original LAB driver IMO was largely governed by the 2.5" voice coil.

I just can't see how a heat wicking solution post coil is going to stop a sudden burst of energy from generating enough heat at the coil itself to potentially cause damage. Maybe a different set of tests would prove/disprove this.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 03:46:16 pm

The information is there, take it or leave it.

I'll also suggest that engines with water-cooled heads develop more power than those with air-cooled heads.  You can argue all day long that combustion is a fairly transient thing and that the intake charge passes through much too rapidly for head temperature to matter.  But you'll be arguing it alone, while the engine with better cooling is lapping you on the track.

Don't be fooled.  This isn't some kind of weird widget.  It works, works well, and its benefits are rather obvious, to be very blunt.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: John Roberts {JR} on July 13, 2006, 04:50:44 pm
Wayne Parham wrote on Thu, 13 July 2006 14:46


The information is there, take it or leave it.

I'll also suggest that engines with water-cooled heads develop more power than those with air-cooled heads.  You can argue all day long that combustion is a fairly transient thing and that the intake charge passes through much too rapidly for head temperature to matter.  But you'll be arguing it alone, while the engine with better cooling is lapping you on the track.

Don't be fooled.  This isn't some kind of weird widget.  It works, works well, and its benefits are rather obvious, to be very blunt.




Be sure to let us know when you finish water cooling your voice coils as that would surely be superior. Might as well water cool your power amps too. Laughing

I don't think anybody is disputing that adding your heatsink could help under the right conditions. I for one would like to hear from some actual live SR users. That is IMO the definitive test, real world use. We already know pretty well how you feel about it.

JR
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 13, 2006, 06:28:21 pm

I've already told you that there are plenty of these cooling plugs in the field, and everyone gets the same results I have.  The motor stays cooler, it's pretty simple.

My comments about this device aren't motivated by how I "feel".  They come from what I know, based on what I've tested and from results in the field.

Some of the posts I see here on the heat exchanger subject are sort of like reading "the Earth is flat because the Pope said so" or "you're stupid not to listen to the Pope".  What happened to the ideals of this forum, where actual measurements trumped speculation?  Looks to me like that has gone out the window.

I won't put anyone on the spot, but I will tell you that there are a lot of people that have stopped posting because of the attitudes here.  There are some good people that haven't been around in a while, and it is because they see people they used to respect saying things they know not to be true.  What we see now are insults hurled at anyone that does something to improve the LABhorn.  Why would anyone subject themselves to this?
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: John Roberts {JR} on July 13, 2006, 07:44:56 pm
Wayne Parham wrote on Thu, 13 July 2006 17:28


I've already told you that there are plenty of these cooling plugs in the field, and everyone gets the same results I have.  The motor stays cooler, it's pretty simple.

My comments about this device aren't motivated by how I "feel".  They come from what I know, based on what I've tested and from results in the field.

Some of the posts I see here on the heat exchanger subject are sort of like reading "the Earth is flat because the Pope said so" or "you're stupid not to listen to the Pope".  What happened to the ideals of this forum, where actual measurements trumped speculation?  Looks to me like that has gone out the window.

I won't put anyone on the spot, but I will tell you that there are a lot of people that have stopped posting because of the attitudes here.  There are some good people that haven't been around in a while, and it is because they see people they used to respect saying things they know not to be true.  What we see now are insults hurled at anyone that does something to improve the LABhorn.  Why would anyone subject themselves to this?



I can't and won't speak for what other people think.

I won't respond to; The Pope, "Flat Earthers", forum ideals, missing regulars or any of the other misdirection.

This is a public forum with no verifiable credentials or technical certification required before posting. I don't know you and you don't know me so all we can each do is make judgements based on how information is presented and how we comport ourselves. In matters of fact all we need do is wait for the "rest of the story". The beauty of this place is that it is still frequented by enough knowledgeable people that the BS is kept down to a steady roar and doesn't take over.

You have already presented your case, a little forcefully for my taste, but no matter. I'm waiting for some real users with applicable first hand experience to check in. I don't need you to tell me the same thing again. Frequency may improve results in advertising but in matters of credibility it can hurt and some independent corroboration, preferably from LAB regulars would be far more effective.  

I'm sorry if my sarcasm seems a little pointed. I'm not attacking you, just the inappropriate analogies, and lack of modesty in making performance claims.

It's OK to be proud of your designs, and defend them if you feel they've been maligned, but this is not a court of law and there is no easy mechanism to verify performance claims. Credible evidence in this court of opinion comes from other peoples experiences. Don't waste your time trying to convince me.  

JR  
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Ivan Beaver on July 13, 2006, 07:57:53 pm
Wayne Parham wrote on Thu, 13 July 2006 14:24


 Bass is bass, and power is power.  

Power is usually expressed in continuous numbers-ie sine waves.  Music is very dynamic, without the continuous nature of sine waves.

I have no doubt that the cooling exchanger will help with long term power (assuming it is able to dissapate it into the air), but we are talking about music.

I would like to see multiple failure tests conducted (differences between drivers issue) with the EXACT same musical signal applied to each (with and without exchanger) as see what the differences are.  Sine wave tests don't impress me,, unless you consider that music?
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Pascal Pincosy on July 13, 2006, 08:10:45 pm
I have never even heard a LABsub at full volume, and I certainly have zero experience with Wayne's heat exchanger. I'm also annoyed by Wayne's claiming that his heat exchanger is the cure-all for problems with LABsubs, especially when that problem is obviously overexcursion of the drivers and has nothing to do with heat buildup. Come on Wayne, please! You are repeatedly spamming the board with your product and it's out of line.

However I have plenty of experience blowing up sub drivers  Rolling Eyes . And I can say with certainty that long-term thermal buildup is a killer. Run your subs for 8 hours straight with a compressed signal well above RMS and you will slowly roast voice coils. The heat created by the motor has to go somewhere. In a sealed chamber there's no where for the heat to go. That's why open-basket designs like the Bassmaxx subs and Danley's tapped horns can provide better long-term performance. The heat is being wicked away by the surrounding air instead of being contained in an insulated chamber. I see no reason why Wayne's heat exchanger wouldn't do the same thing ie wick heat away from the motor.

Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 14, 2006, 01:19:04 am

Actually, all music is composed of sine waves.  The test signal I used is pretty similar to what a loudspeaker is subjected to during a live performance, in fact, it wasn't as brutal because it had several cooldown periods, not a constant signal.  Use whatever test signal you want, the device with a heat exchanger still vastly outperforms one without.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 14, 2006, 01:33:38 am

I'm about sick of being accused of "spamming" when what I've done is to provide my engineering skills, my mechanical engineer's skills, my test results, my designs and photographs of the build-up process free of charge.  What I've done is to provide freely available plans for a high performance basshorn, and to mention that here.  I've responded to people that have asked about 12Pi basshorns.  And I've given LABhorn owners information about a compatible part they can make and install on their horns to improve them.  If that's disagreable spamming, then what in the world is this forum even here for?

By the way, the problem isn't heat build-up in the rear chamber.  It's heat build-up in the motor, radiated into the pole piece and stored in the ceramic and metal.  Open back designs suffer too, because the heat build-up is in the motor.  You have to wick the heat out of the motor.  Perhaps you'll consider this information "spamming" or maybe you'll dismiss it as being unsupported, in which case I encourage you to duplicate my work, test my claims and see for yourself.  Or don't, whatever.
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Andy Peters on July 14, 2006, 03:02:38 am
Wayne Parham wrote on Thu, 13 July 2006 22:19

Actually, all music is composed of sine waves.


Techno is primarily sine waves, and since I don't do drugs, I find it boring.  Desperately dull.  Ugh.

Seriously, though, many of us understand Fourier transforms.  I think that Ivan's point is that there's a difference between running a 75 Hz pure tone into a sub cabinet at crush and running the kick drum and bass-E-string-every-quarter-note.  The duty cycle differs, for one, and I'm sure you know that.

Quote:

The test signal I used is pretty similar to what a loudspeaker is subjected to during a live performance, in fact, it wasn't as brutal because it had several cooldown periods, not a constant signal.  Use whatever test signal you want, the device with a heat exchanger still vastly outperforms one without.


Now I'll put on my engineer's hat.  Have you measured the heat-transfer efficiency of your heat sink and of the whole system?  Seems to me that there will be a positive effect through the conduction cooling, but you're still heating the inside of the cabinet (esp. if the cabinet is stuffed with insulation), limiting overall heat-transfer efficiency.  I suspect that there's little, if any, convection (other than the cone moving), so in practical terms, the benefit may not be all that great.   The only way to know for sure is to instrument the motor structure, the heat sink and a couple of locations inside the cabinet.  A handful of thermocouples or RTDs and an Omega logger will do the trick.

And along those lines, can you quantify the statement, "the device with a heat exchanger still vastly outperforms one without"?  I'd like to know what your test set-up is like, and I'm sure that others may wish to duplicate your results.

Perhaps the motor heatsink is like those metal things you can buy for your computer memory.  Yeah, they're heat sinks, but moving the heat a sixteenth of an inch from the chips makes little difference if you don't remove the heat from the heatsink.  These things are little more than a placebo.

-a
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 14, 2006, 03:28:07 am

Read the posts that show the heat exchanger construction.  It is described in great detail, enough that you can build one and install it.  Also shown are test results, conditons, setup, etc.

Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Matt Jordan on July 14, 2006, 05:24:40 am
 Confused This place used to be fun. Get off your high horse and bake me a nice meatloaf. We are all in this together. Remember?
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: John Roberts {JR} on July 14, 2006, 10:16:44 am
Andy Peters wrote on Fri, 14 July 2006 02:02



Now I'll put on my engineer's hat.  Have you measured the heat-transfer efficiency of your heat sink and of the whole system?  Seems to me that there will be a positive effect through the conduction cooling, but you're still heating the inside of the cabinet (esp. if the cabinet is stuffed with insulation), limiting overall heat-transfer efficiency.  I suspect that there's little, if any, convection (other than the cone moving), so in practical terms, the benefit may not be all that great.   The only way to know for sure is to instrument the motor structure, the heat sink and a couple of locations inside the cabinet.  A handful of thermocouples or RTDs and an Omega logger will do the trick.

And along those lines, can you quantify the statement, "the device with a heat exchanger still vastly outperforms one without"?  I'd like to know what your test set-up is like, and I'm sure that others may wish to duplicate your results.

Perhaps the motor heatsink is like those metal things you can buy for your computer memory.  Yeah, they're heat sinks, but moving the heat a sixteenth of an inch from the chips makes little difference if you don't remove the heat from the heatsink.  These things are little more than a placebo.

-a


Is an engineers hat that floppy little job worn by the guy driving the train?

OK back on topic. You can measure the rise in VC temp non-invasively. Copper has a pretty well established temperature coefficient, so by comparing the cold or room temp VC resistance to hot VC resistance you can impute how hot the VC is or isn't getting. This mechanism could even be used in smart powered speakers to detect and manage power compression.

Getting heat out of VC is a classic problem and there are lots of patents covering sundry approaches. You are quite correct that a major problem is getting the heat out of the box. Hi/lo ports allow for some natural convection and asymmetrical ports that bias airflow direction could pump cool air though a box. Any number of approaches help to some degree, and some can compliment each other. None AFAIK is a magic bullet.

There has also been much work done to make VC adhesives and materials more tolerant of extreme temperatures but this doesn't mitigate the power compression caused by the resistance rise.  

JR  
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 14, 2006, 12:19:44 pm
My first prototype used a venting system as you've described.  The diaphragm motion was ducted into two ports, each that introduced turbulent flow in one direction but allowed laminar flow in the other.  My thought was to duct heated air out through a heat exchanger, returning cool air into the system.  Unidirectional flow was required so that a hot air slug didn't move back and forth along the duct.


The venting arrangement worked extremely well for introducing unidirectional flow.  The real problem was that even with motor temperatures well above 150
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on July 16, 2006, 01:04:26 am
http://audioroundtable.com/images/Laughing_Felix.gif
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Grant Rider on August 02, 2006, 02:45:02 am
First post here. Nice job! Where can I learn more about this 12pi subwoofer? Can I see the plans?
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Wayne Parham on August 02, 2006, 11:58:01 am

You can request AutoCAD drawings for the 12Pi basshorn on the Pi Speakers forum, or just shoot me an E-Mail.  I'll send them right out.  More information about the 12Pi basshorn can be found at the links below.

12Pi development and construction
Test results and related information
Title: Re: Is the 12pi Subwoofer an upgrade to the LAB?
Post by: Grant Rider on August 03, 2006, 04:03:08 am
Sending email directly.