Invisible speaker / wall audio transducer discussion thread (moved from Construction forum) - AVS Forum
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To not further clog up Bryan's HT thread ,My Mahogany / Invisible Speaker build , this discussion related to Invisible speaker / wall audio transducer moved here.
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post #3 of 29 Old 10-16-2013, 10:43 AM - Thread Starter
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The below copied/pasted from page 8 of http://www.avsforum.com/t/1313580/my-mahogany-invisible-speaker-build/210
Quote:
Originally Posted by mtbdudex View Post

There is another transducer thread here, and wanting to learn from your experience I re-post my Q to him now also to you:
Quote:
Originally Posted by mtbdudex View Post

I come to this thread looking for acoustic measurements, like to learn about all the wall mounted transducer performance.
I'm looking for waterfall for below 250hz and gated ETC for above 250hz, did not see them posted.
Also, you are not using Audyssey EQ at all?
( I can't recall reading if you did or not).

Specifically what acoustic calibration was done?

From what I've gathered there are 2 suppliers, I've not seen any Freq response / gated ETC charts / waterfall plots, or spec sheets, nor any objective measurements by those that have used them in their website.
http://www.invisiblestereo.com/html/faq.html and http://www.hiddenaudiosystems.com/index.html

So, looking for your take.

Quote:
Originally Posted by MississippiMan View Post

Those "two" suppliers are actually one and the same, however it must be noted that I am the factory representative for Hidden Audio Systems. I don't advertise that fact because I'm not on here to do so.

Specs are such:

20 hz-20,000khz +/-3db (... depending upon the surface on which the transducer is mounted...)
Drywall is 35hz-18,000khz

Power Handling: 200 watts Peak / 100 watts Continious.

Each Transducer comes supplied with a Ray Chem Poly Switch, which is a liquid, self resetting device which prevents over powering the unit when is seriesd inline between the transducer and the amplifier. It is rated for 90 watts, but I find myself seldom using it because of the robust nature of the transducer and the simple fact that quite often I am paralleling at least 2 or more when using them for high performance, home theater applications. That effectively doubles are rated continuous power input capability.... and there are not many audio applications which will be delivering a continuous 180 watts to any specific channel.

As a point of reference, most of the channels in RedTopDown's system have four transducers in parallel, which are in turn serise'd with another for transducers, making for a total of 8 transducers per channel. That configuration allows for a rated the power input of 360-watts continuous per channel.

The real object of using transducers to produce audio through a structual solid is too and put enough energy to make the solid resonate accurately to any and all given frequencies. Certainly, the density, mass, and structural makeup of a structural solid will play an important role as far as the efficiency of the transducer and. the accuracy of the reproduced sound.

Quote:
Originally Posted by mtbdudex View Post

Quote:
Originally Posted by MississippiMan View Post

Those "two" suppliers are actually one and the same, however it must be noted that I am the factory representative for Hidden Audio Systems. I don't advertise that fact because I'm not on here to do so.

Specs are such:

20 hz-20,000khz +/-3db (... depending upon the surface on which the transducer is mounted...)
Drywall is 35hz-18,000khz

Power Handling: 200 watts Peak / 100 watts Continious.

Each Transducer comes supplied with a Ray Chem Poly Switch, which is a liquid, self resetting device which prevents over powering the unit when is seriesd inline between the transducer and the amplifier. It is rated for 90 watts, but I find myself seldom using it because of the robust nature of the transducer and the simple fact that quite often I am paralleling at least 2 or more when using them for high performance, home theater applications. That effectively doubles are rated continuous power input capability.... and there are not many audio applications which will be delivering a continuous 180 watts to any specific channel.

As a point of reference, most of the channels in RedTopDown's system have four transducers in parallel, which are in turn serise'd with another for transducers, making for a total of 8 transducers per channel. That configuration allows for a rated the power input of 360-watts continuous per channel.

The real object of using transducers to produce audio through a structual solid is too and put enough energy to make the solid resonate accurately to any and all given frequencies. Certainly, the density, mass, and structural makeup of a structural solid will play an important role as far as the efficiency of the transducer and. the accuracy of the reproduced sound.

Can you share 3rd party testing done in a anechoic chamber with a "typical" wall install method that you use?
I'd like to confirm the results.

btw, we have a few anechoic chamber's at my work, here's my daughter at "bring your child to work day" in one of them

Quote:
Originally Posted by cowger View Post

Quote:
Originally Posted by mtbdudex View Post

There is another transducer thread here, and wanting to learn from your experience I re-post my Q to him now also to you:
From what I've gathered there are 2 suppliers, I've not seen any Freq response / gated ETC charts / waterfall plots, or spec sheets, nor any objective measurements by those that have used them in their website.
http://www.invisiblestereo.com/html/faq.html and http://www.hiddenaudiosystems.com/index.html

So, looking for your take.

Mike, unfortunately I don't have any of those technical answers for you, sorry. I am using the Audyssey feature of my Onkyo receiver, FWIW.

Perhaps Maurice could point you to someone there locally with an installation, or if you're ever here in Northern Cal, you're welcome to swing by, if that would help.

Bryan

Quote:
Originally Posted by MississippiMan View Post

Quote:
Originally Posted by mtbdudex View Post

Can you share 3rd party testing done in a anechoic chamber with a "typical" wall install method that you use?
I'd like to confirm the results.


  1. Due to the omnidirectional dispersion characteristics of the Transducer, measurements are slanted toward somewhat false readings. For instance, db levels are high while SPLs are markedly lower.
  2. Simply placing a partition wall assembly upright does not allow for the structural mass coefficient that is required to allow the sound to propagate effectively, and develop the full range of frequencies.
  3. Measurements taken via the use of a Audio Spectrum Analyzer have often shown a remarkably Flat response, even in some very extreme acoustically deficient environs.(Churches / Large Halls / Bare Rooms.

In the end, Transducers have primarily depended upon an effective installation, done correctly, and using optimal materials. Years ago before I ever considered installing them instead of "speakers" for home and commercial use, I focused on installing the on the front and rear windshields of Cars, and building them into the walls and cabinets of Vans. Glass is the absolute ideal medium for accurate resonance, with select Non-Void Plywood w/hardwood veneers. (Marine Grade Douglas Fir / Oak / Mahogany Paneling) Drywall comes in after those,but constitutes the vast majority of applications.

However they are used on the Steel Bulkheads of "every" ship in our Navy, (...and more than a few other countries as well...) as well as most every Shore Based Office application for Sound masking / Security apps as well as "explosion proof" audio within volatile environments. (...ditto with Hyperbaric Chambers and Floatation Tanks...) where they interface with FiberGlas, Steel, and Wood. They have been used for years in Spas / Hot Tubs / Saunas....everywhere sound is wanted but usually cannot be accommodated. They work very well affixed to Drop Ceiling Tiles (...solid Fiberboard variety...)

I have helped design Acoustical Art projects for years among the Scholastic and Artistic groups. David Tudors "Rain Forest" exhibits are world renowned for the use of Transducers on a wide variety of surfaces..In Spain a couple years back, I went over to help design and install a 40' long Steel Tunnel with 80 Transducers where groups of 8 each received various feeds of frequencies supplied by Dripping water into various sized thin Copper Bowls that themselves had Transducers applied to their bottoms and used in reverse as Microphones.

It was a surreal experience..... eek.gif

On and on it could go...but that is not my intent here. Suffice it to say that for over 25 years prior to my interest in DIY Screen making, and the resulting Patents obtained therein, I was pretty much instrumental in the development of every Transducer application previously listed, but ya gotta know, turning a Wall into a Center Channel and then painting a Screen onto that spot hold the nearest and dearest spot in my heart.

In truth, since Julian Hirsch http://en.wikipedia.org/wiki/Julian_Hirsch last reviewed the Audio Transducer back in 1972,(..and gave it high marks BTW...) my Peers have either overlooked or discounted the use of Transducers....leaving me as the sole individual promoting their use across the globe. Such was my fate.....a Teamster converted in 1977 into a Audio Pioneer.

Somebody stick a fork in me....I'm done here. biggrin.gif

Quote:
Originally Posted by mtbdudex View Post

Quote:
Originally Posted by MississippiMan View Post

Quote:
Originally Posted by mtbdudex View Post

Can you share 3rd party testing done in a anechoic chamber with a "typical" wall install method that you use?
I'd like to confirm the results.


  1. Due to the omnidirectional dispersion characteristics of the Transducer, measurements are slanted toward somewhat false readings. For instance, db levels are high while SPLs are markedly lower.
  2. Simply placing a partition wall assembly upright does not allow for the structural mass coefficient that is required to allow the sound to propagate effectively, and develop the full range of frequencies.
  3. Measurements taken via the use of a Audio Spectrum Analyzer have often shown a remarkably Flat response, even in some very extreme acoustically deficient environs.(Churches / Large Halls / Bare Rooms.

In the end, Transducers have primarily depended upon an effective installation, done correctly, and using optimal materials. Years ago before I ever considered installing them instead of "speakers" for home and commercial use, I focused on installing the on the front and rear windshields of Cars, and building them into the walls and cabinets of Vans. Glass is the absolute ideal medium for accurate resonance, with select Non-Void Plywood w/hardwood veneers. (Marine Grade Douglas Fir / Oak / Mahogany Paneling) Drywall comes in after those,but constitutes the vast majority of applications.

However they are used on the Steel Bulkheads of "every" ship in our Navy, (...and more than a few other countries as well...) as well as most every Shore Based Office application for Sound masking / Security apps as well as "explosion proof" audio within volatile environments. (...ditto with Hyperbaric Chambers and Floatation Tanks...) where they interface with FiberGlas, Steel, and Wood. They have been used for years in Spas / Hot Tubs / Saunas....everywhere sound is wanted but usually cannot be accommodated. They work very well affixed to Drop Ceiling Tiles (...solid Fiberboard variety...)

I have helped design Acoustical Art projects for years among the Scholastic and Artistic groups. David Tudors "Rain Forest" exhibits are world renowned for the use of Transducers on a wide variety of surfaces..In Spain a couple years back, I went over to help design and install a 40' long Steel Tunnel with 80 Transducers where groups of 8 each received various feeds of frequencies supplied by Dripping water into various sized thin Copper Bowls that themselves had Transducers applied to their bottoms and used in reverse as Microphones.

It was a surreal experience..... eek.gif

On and on it could go...but that is not my intent here. Suffice it to say that for over 25 years prior to my interest in DIY Screen making, and the resulting Patents obtained therein, I was pretty much instrumental in the development of every Transducer application previously listed, but ya gotta know, turning a Wall into a Center Channel and then painting a Screen onto that spot hold the nearest and dearest spot in my heart.

In truth, since Julian Hirsch http://en.wikipedia.org/wiki/Julian_Hirsch last reviewed the Audio Transducer back in 1972,(..and gave it high marks BTW...) my Peers have either overlooked or discounted the use of Transducers....leaving me as the sole individual promoting their use across the globe. Such was my fate.....a Teamster converted in 1977 into a Audio Pioneer.

Somebody stick a fork in me....I'm done here. biggrin.gif

So are you saying that there are no 3rd party testing to share?
Or, there is but the readings do not match what you claim the ears hear?
Please share what objective testing has been done.

Also - explain how "db levels are high", yet SPL are lower? Please post the charts that back up these statements, I'd like to "grok" them.

Quote:
Originally Posted by MississippiMan View Post

Quote:
Originally Posted by mtbdudex View Post

So are you saying that there are no 3rd party testing to share?

Yes...and I know that is strange for some to accept, but the emphasis on distribution has be within Commercial Industry and Military applications, and the attributes of the Transducer has been / is well known and accepted in the Educational & Artistic communities for many years. when the most recent version was released, one that was / is 4x more proficient than the former, it didn't take much convincing within those fields to accept it "as is".

As for using within the A/V realm, such is / has always been limited to specific trained Dealer/Installers, with no direct sales allowed, for just the sort of reasoning you might expect....the Mfg and myself do not want improper installation...or the issues that result from "Sellers" making the product seem to be something that youy just stick on the wall or a window and have at it.

As such, showing it in action in actual, properly installed applications is the primary way to exhibit / test the Transducer. Trade Shows, Home Shows, or direct demonstrations get that accomplished...with the expected "OMG" results that do all the convincing.
Quote:
Or, there is but the readings do not match what you claim the ears hear?
Also - explain how "db levels are high", yet SPL are lower? Please post the charts that back up these statements, I'd like to "grok" them.

You realize what happened to the "Stranger in a Strange Land" right? He got a little too "Grok'ed" eek.gif People were just not ready to accept what he had to offer them...or at least failed to understand.
I have often felt that way myself when explaining the Transducer to those who could not accept the possibilities inherent in the unit. Instead, I simply let the "Jaw drop" syndrome do all the convincing...."IF" I could arrange for a decent demonstration. wink.gif

But consider this "layman's" explanation.

Conventional Speakers produce sound by first resonating a diaphragm of some type, and with the resulting "push/pull action of the voice coil, pump those frequencies into the environment, resulting in both db and SPL production.

A surface that has a Transducer mounted behind it resonates a 360 degree, 1/2 hemisphere of dispersion...up to 8' in diameter, with every frequency radiating outward from center to it's specific point where the wave length can saturate that given point, making it accurately resonate. Highs only travel a short distant before doing such...each to a specific point, Mid-range travel further, and Bass the furthest. This is exactly what / how any full range speaker works, and it's pretty much accepted that a 10" full range speaker does a better job than a 5"er because of it's larger diaphragm area, and the obviously larger enclosure most such drivers would have if not a "Free Air" installation.

But there the differences between such "Air Motion Drivers" and Audio Transducers come into play.

The existent air pressure of a room lying against the surface a Transducer is mounted absorbs and propagates the resonant energy on the surface of the structural solid, outward into the room, air molecule to air molecule, in a cascade effect....furthering the omnidirectional dispersion. The wall does not move / travel back & forth. Instead, the Transducer itself moves very slightly within the wall / opposite side, and does so in conjunction with the amount of travel of the voice coil within the Magnet Structure / Gap.

this is why effective volume can be obtained without nearly the amount of SPL production a normal speaker produces. It is that property in and of itself that makes a Transducer system far less susceptible to acoustic concerns resulting from SPLs / and standing wave interference.

Oh....absolutely some degree of SPLs are produced, but they are markedly lower than the db levels would seem to indicate they should be. That is why at first, to many who are used to how convention speakers sound, the sound seems somehow "different" to them. Much the same as is experienced with Electrostatic Panels.

All of the above is why the Transducer is the most accepted device for sound masking applications Industry-wide. You cannot absorb frequencies into a solid if the energy of the incoming frequency does not match or exceed the level of resonant energy inherent within the material, or exceed the naturally suppressive properties of said material. And if the frequency of the surface is tuned to an appropriate level (...w/ White or Pink noise...) the surface can...and will effectively cancel out reflections, deadening the surface's absorption / reflective properties.

That is about the extent I care to delve into the subject on Cowger's thread, as I do not want the subject to become a primary focus. But I'm sure both Cowger and RedTopDown will confirm what I've related, so therein is you "Independent testing" examples....real world as it were.

But let me add this. The dearth of 3rd party Testing is really more a result of years of disinterest by those who fixate on conventional speakers, combined by the inability to test the Transducers in the many different varieties of applications it can potentially cover. The Transducer ain't a "One Trick Pony"....but just the same, it's not the "End All' in audio reproduction either, nor is it ever going to be acceptable to those who pursue and value sheer Volume / SPL production above all else.

But that's OK....let 'em regress into needing hearing aids. I myself suffer from hearing loss that comes from the excessive volume I allowed myself to suffer, from just 4-5 years involvement in the Pro Sound Reinforcement industry building and testing Live Concert PA and Discotheque systems that could...and did make my ears ring for days. Excessive use of Headphones during Mixing only worsened my loss. frown.gif

Quote:
Originally Posted by TMcG View Post

There are so many misstatements of fact in the above post I barely know where to start. The reason transducer technology is found in artistic, education and trade set-ups - because sound quality doesn't matter (primarily loudness) or it is designed to NOT be seen and/or easily stolen or damaged. There's a big difference between having exposed speakers make sound in an artistic display vs. integrated transducers into the piece in a stealth way because they want people to focus on the art. The military uses transducers as the most effective way to transmit underwater audio and signals as well as crowd-dispersing technology like the LRAD. Both are applications conventional speakers can't handle or do not perform as effectively as a transducer.

However, to equate a direct correlation from these market niche's into a high-fidelity home theater lacks the necessary translation. There is a reason why speaker manufacturers are aware of this technology and yet don't produce for high-fidelity home use....because the technology has limitations well beyond installation considerations. If a person is wanting a completely stealth look with no apparent speakers, no acoustically transparent fabric (including the screen), then transducers are the only option to get you there, but there are significant trade-offs and compromises.

MTbdudex is rightly justified in challenging your notions of fidelity as empirical measurement data is the only thing that truly evaluate actual in-room performance. What's the polar response of a transducer in typical building materials of 1/2" drywall, 5/8" drywall, 1/2" veneered plywood? All easily tested in a lab under controlled conditions and yet it's not done by the manufacturers, leaving for ad-hoc impressions as the best evidence. Every other speaker manufacturer publishes these specs for this reason. The whole realm of acoustics is focused on the science of sound reproduction for this reason....and yet you discount those of us who are of the opinion that we like to understand the performance data of our speakers, either conventional or tranducer.

This doesn't even begin to discuss integration strategies with a soundproof shell. How could a transducer perform effectively through a double 5/8" drywall / Green Glue wall? It can't, so now another wall has to be built in addition to the shell just to integrate the transducer technology....and how much will all this additional time and expense cost for what amounts to a lower fidelity system? And if you have a driver go bad in a room as nice as Cowger's, what has to happen to replace it? Tearing into all of the finish carpentry, at a minimum. Seems like a risky proposition, especially for someone without Cowger's skills (and tools) and talent to rectify the problem with surgical precision.

I think Cowger has a very nice looking theater and made the choice for what fit best with his design aesthetic while compromising on different design considerations every step of the way, including speakers. And I am sure Cowger is very happy. But it is not a responsible statement to say that transducer technology has equivalent fidelity to a conventional speaker system. Given the low cost, I am sure every other commercial theater would otherwise have transducer technology instead of an array of speakers if it didn't lack in performance in such a venue.

Quote:
Originally Posted by MississippiMan View Post

I plainly stated that the technology is not the "End All" nor for everyone to consider.

....and you really have no idea how widely dispersed the use of the specific transducer related is.....not at all. So don't be so wholly dismissive.
The construction methods you stated relate to what is required for conventional high db / SPL systems. Of course it is not meant to nor is applicable to use through 1 -1/2" of Fire Rated Drywall. Nope....but it does just fine through a single layer of 1/2" or 5/8". But I prefer Wood Paneling myself.

Your response parallels those I've heard over many years coming from those with little or no actual experience with the product discussed, let alone in a proper installation.

Why the adamant and negative post? Because the entire subject runs contrary to "know and accepted' beliefs. The "knee jerk" reaction is expected. But it's a little obtuse and somewhat myopic. And where did I "discount" anyone ....beyond stating that there was no vested interest or desire for many to pursue such technology?

That's really all just OK...but my intent was not to get any promotional discourse started, nor advocate the use of such in favor of or to the exception of the treasured conventional audio so many value.

So don't take it to be anything of the sort. I'll simply let Cowger and any other's make their own determinations....and so should you.

So let Cowgers project be the primary focus.

Quote:
Originally Posted by TMcG View Post

Quote:
Originally Posted by MississippiMan View Post

I plainly stated that the technology is not the "End All" nor for everyone to consider.

....and you really have no idea how widely dispersed the use of the specific transducer related is.....not at all. So don't be so wholly dismissive.
The construction methods you stated relate to what is required for conventional high db / SPL systems. Of course it is not meant to nor is applicable to use through 1 -1/2" of Fire Rated Drywall. Nope....but it does just fine through a single layer of 1/2" or 5/8". But I prefer Wood Paneling myself.

Your response parallels those I've heard over many years coming from those with little or no actual experience with the product discussed, let alone in a proper installation.

Why the adamant and negative post? Because the entire subject runs contrary to "know and accepted' beliefs. The "knee jerk" reaction is expected. But it's a little obtuse and somewhat myopic. And where did I "discount" anyone ....beyond stating that there was no vested interest or desire for many to pursue such technology?

That's really all just OK...but my intent was not to get any promotional discourse started, nor advocate the use of such in favor of or to the exception of the treasured conventional audio so many value.

So don't take it to be anything of the sort. I'll simply let Cowger and any other's make their own determinations....and so should you.

So let Cowgers project be the primary focus.

The technology behind Cowgers invisible speaker project IS the focus here. There's no harm in discussing the invisible audio technology behind this theater in this thread, right? After all, it is in the title and you were the one that helped install the system. I can't think of a more appropriate place to discuss the details and design considerations, including trade offs. The entire AVS community benefits from these discussions.

I don't find it appropriate to make assumptions on my own personal experience or feelings with transducers. Although not as in-depth as you appear to be, it may surprise you to find that over the last 21 years I have used some transducer-based speakers, including in my current home with a variation made by Sound Advance, the SA2 speakers. I have a pair of these in my dining room for an ultra-stealth look and people are amazed with sound emanating directly from the wall. It's always a point of discussion for those that visit our home and hear the system. But I can tell you that even with a fully engineered transducer solution with complementary back box, the transducer technology has no where near the fidelity of a conventional speaker. Further, Sound Advance actually makes a compensation circuit device (essentially an EQ) that is used to help make the transducer speaker sound as good as possible. Although optional, the difference is so dramatic I think the device should be standard equipment with the speakers. An example can be found HERE.

You had mentioned that the speakers have a 35Hz - 18,000kHz frequency response through drywall, which indicates that this had been tested but then immediately turn around and state testing was not available when mtbdudex asked for additional information. I (and I am sure many others following this thread) was also interested in seeing and learning. It's obvious the radiating pattern for a transducer is different for different substrates and we were asking you to shed a bit more light on how these performed in real life from an acoustical measurement / scientific standpoint vs. the "it sounds good" more emotional standpoint as reiterated in the quoted post above. Certainly somebody who is actively involved in developments and patents would be able to offer more information to this point. But if you don't have it, then I guess you don't have it.

Quote:
Originally Posted by aackthpt View Post

Quote:
Originally Posted by cowger View Post

Now I need to figure out how to treat that surface. I was thinking either mineral oil or perhaps something called salad bowl finish. Any other ideas on what to do with this? I want something food safe that won't mind being chopped on a bit...

Looks like salad bowl finish contains some sort of polyurethane, and while it might be safe for food contact it appears it is anti-recommended for a cutting surface. Then again the anti-recommenders might be crazies, so do what works for you.

Personally, for wooden cutting boards (which I prefer these days by a huge margin) I saturate them with mineral oil to keep them "wet" inside and eliminate splitting or water take-up from the occasional washing (in the sink, not the dishwasher for god's sake). Then, to for a longer lasting surface finish and to hold the oil in better I use a combination of beeswax and mineral oil that I make myself. It's something like this. I'm very happy with the results of this system.

The one drawback of this system in your situation is that that the mineral oil can actually go through the wood fibers if you apply enough to really soak the wood--which is a problem due to having a cabinet under this top. It may or may not be much of a problem for you since you'd be applying to side-grain rather than end-grain, but better safe than sorry. So I'd polyurethane the underside of the 'top to eliminate the soak-through issue, then keep the top as wet as possible with mineral oil for 2-3 days, remove the excess, then apply the beeswax mixture.

The Wood Whisperer does apply a thinned polyurethane to his end-grain boards to fill the grain and make it less porous. He doesn't seem to have been sued out of existence, so it's probably reasonably legit to use salad bowl finish, thinned polyurethane, or whatever works for you.

I'll throw in my 2 cents on the transducer issue: I wouldn't buy speakers (anymore) based on simply listening to them playing music or other material, and I wouldn't buy speakers based on a frequency response rating. At minimum I'd better see an on-axis frequency response (out of the near field), and probably still wouldn't without polars or off-axis FR curves.

I imagine one of the great things about this transducer plan is that if a person decided they didn't like their transducer install sound, you just stop feeding them and start using regular speakers--nothing lost.

Quote:
Originally Posted by mtbdudex View Post

One of the reasons I stay active with AVS vs the 4-5 other audio forums I am a member is the "S" in AVS is for Science.
Subjective statements need to be backed up with objective, fact based data. This is fundamental to the scientific method.

For sure I don't want to muck up Bryan's HT thread, like TMcG also stated this community can learn from a articulate and fact based exchange of ideas.

From what I see, Roland Maurice Boughton (MississippiMan) has a patent in Projection screen coating, not transducer technology.
For transparency, he is also the Registrant for Invisible Stereo, not sure who is behind Hidden Audio Systems transducers, though since Roland is their factory rep he may be the Registrant for that website as well.

Thru my "daily job" I've applied for a patent a few years back, but it was not awarded, I do understand the scientific method.

I simply originally asked Bryan these Q's:
Quote:
I come to this thread looking for acoustic measurements, like to learn about all the wall mounted transducer performance.
I'm looking for waterfall for below 250hz and gated ETC for above 250hz, did not see them posted.
Also, you are not using Audyssey EQ at all?
( I can't recall reading if you did or not).

Specifically what acoustic calibration was done?

Bryan stated he has not done any acoustic measurements.

I still request Roland to take acoustic measurements to back up his claims, to not further clog up Bryan's HT thread possible the Audio Theory forum may be a better place for such discussion.
Later I will start a thread there, and copy/paste from here to there to continue the discussion, exchange, and learning.
(too busy to create that thread just now, later today I will and edit this post and link above to point towards it)
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From the other audio transducer build thread, "Reel Time" Build Log-14' Scope, 9.7 17,000W Transducer Audio, Dedicated Stadium Room
Quote:
Quote:
Originally Posted by RedTopDown View Post

STILL CATCHING UP WITH PAST WORK, TRYING TO GET EVERYONE (AND MYSELF) BACK UP TO SPEED! PLEASE BEAR WITH ME!


Installed a total of 12 tactile transducers with four under each row.


Quote:
Originally Posted by RedTopDown View Post

Some shots of the transducers for the hidden audio system that MississippiMan will be installing in an 11.4 channel setup.





Quote:
Originally Posted by RedTopDown View Post

Okay, so now that MMan has headed back south to warmer weather and I have a chance to breathe, here's an update of our audio install.


Here are some shots of the actual transducer install process.



Two shots of one of the rear channels with four transducers mounted to the drywall. We added a horizontal batt to enclose the space since the rear subs sit below, and a batt in the back to decrease the depth a bit.









Two shots of one of the surround side channels. MMann's head is seen in the one! Two of the four transducers were mounted on a 3/4" cabinet-grade ply for more bass response. For each side surround channel, a total of eight transducers were used. The slack of the wire was pulled into the adjacent plenum to keep them off the AC line you see.









One more shot of some of the transducers in one of the front channels






We modified the layout a bit in the end and expanded the count of transducers from 52 to 56 with four on order for me to install now that I've learned from the master.


8 - Surround Rear L & R (4 each) - 1 EP2000

16 - Surround L & R (8 each) - 2 EP2000

16 - Right & Left (8 each) - 2 EP2000

8 - High Effects L & R (4 each) - 1 EP2000

8 - Center - 1 EP2000


56 transducers & 7 Berhinger EP2000 Amps


Three of the four channels of the other two EP2000's drive 12 tactile transducers mounted in three rows of four in the floor below each row.


My hands are still trying to recover from the cutting, stripping, and crimping! Here's my approximation of the effort they went through. Yes, I know... Boo Hoo... I wanted to add this all up for my own knowledge anyhow!


There's a 12ga wire from the amp to each group of four transducers to achieve a 2 Ohm load. So that's 14 "supply" lines. Each supply line is then connected to four short leaders going to each of the transducers in the array. There are two crimp connectors that are used to connect the transducer to those leaders.


140 Cuts

28 - 14 supply lines x 2

112 - 56 leaders x 2


140 Sheathing Strips

28 - 14 supply lines x 2

112 - 56 leaders x 2


280 Conducter Strips

56 - 14 supply lines x 4

224 - 56 leaders x 4


112 Connector Crimps

112 - 56 leaders x 2


That doesn't include re-working the channels a bit, connecting the leaders to the supplies, Neutrik connectors, ...


Okay, that's enough whining, right?


I'll put a review of the sound in another post.

Quote:
Originally Posted by RedTopDown View Post

Okay, now I have to admit that I went into this with no actual visit to an existing home or theater with a transducer-based audio setup. I did make a few calls to some of MMan's clients to get their opinions, but no one was really close to me for a visit. I drank the Kool-Aid based on their feedback and listening to the words and wisdom of MMan.


Let me tell you my thoughts leading up to the install and first listen - trusting but nervous. No matter how much I read up about transducers (little out there I know) and talked to MMan, I still couldn't get my mind around the fact that great sound would come out of a medium known as drywall! All my listening experience has been from standard speaker setups that we all know about.


Some recent online and print reviews of transducer systems (albeit MUCH, MUCH smaller and less planned out) didn't help me when they would say things like "don't expect great quality audio" and "it was just decent audio". Not what I was looking for at all. Now, these systems were nothing like we installed with 56 transducers properly wired to multiple amplifiers for a 2 Ohm load (see previous install post) and all in a design specific to the task.


Okay, enough of the dribble of my fears leading up to flipping the switch on the first amp!


So after finishing up our install on Monday, making some final connections, and having my 17 y/o lug up the four Outlaw subs (two of them monsters), we were ready to fire it up.


We started with the amp on the top which drove two rows of the tactile transducers in the floor. I flipped on the switch on the front of the EP2000 and POWWWWW! A large spark/arc went off inside the amp! That scared us right off the bat. After checking connections and some testing, we quickly determined that there was a defect in the amp itself. One amp DOA!


Needless to say, turning on the next amp was not easy given the first! But we pressed on! One by one we fired up the amps until it sounded like a small jet getting ready for take off in the room. Yes, as many of you know, they are not quiet. That's why they are going behind closed, sealed doors.


We set the gain at 50% on each amp and put in a movie to test everything out. Keep in mind that we have a raw room and I still need to seal the plenums behind for the front, effects, and center channels.


All I can say is that I was truly amazed! Sound was coming from everywhere around us in the room FROM THE DRYWALL. We did a little tweaking here and there, but we have yet to even start to do any calibration. I can't speak enough about how great everything sounds considering the raw nature of the room in its current state. We put in the movie "House of Flying Daggers" to the Echo Game scene to try a good test. If you know that movie and scene, there is very delicate sounds going on from beans rattling in a bowl to earrings tinging as the game begins. Then loud spurts begin as the drums get going and she begins to rap each drum in a repeating sequence. Everything was coming through clear and distinct and from all around us as the movie depicted.


We threw in some more movies, watching half of Rango and then all of Captain America. The dialog was very good, but definitely being affected by the open plenums. Going up to the screen wall you would hear the sound resonating from the drywall and if you got behind the wall you would hear the same sound in the chamber with a lot of echos. So sitting out in front watching the movie, the two sounds front and back were competing against each other and in some ways cancelening the other out. We'll get a big improvement when I close those plenums off.


After MMan departed on Tuesday, the family pulled out some cushions and piled on the floor to watch Green Lantern. I tweaked the channels a bit more as the movie rolled and the sound just kept getting better and better. I can only imagine what it will be like when the room is dampened with carpet, furniture, etc. AND we properly calibrate the whole system.


Finally, I'm not going to sit here and bash any system, traditional or not. Each to his or her own. Just a week ago I went to a highly-regarded local audiophile/HT dealer in town and sat in one of their theaters. The audio system alone was $50K+. No doubt, it sounded wonderful as we watched the Echo Game scene I talked about above. I can't properly compare the two since they have a perfectly treated room and calibrated system and I have a raw room, incomplete install, and uncalibrated system. Even with those major differences and listening to the same test, I'm perfectly happy with my decision to go with transducers. I have no doubt that after equalizing the room and system, the differences will be minute.


I have no doubt that my future guests will be blown away as I was and then starting looking around for the speakers. They will be quite shocked when they can't find any of them sitting in the room or masked behind cloth.


I look forward to updating everyone on sound tests as we move forward.


Thanks MMan. I'm glad I put my faith in you. You delivered!

Quote:
Originally Posted by stockmonkey2000 View Post

Very interesting build. I looked at your thread a while ago and assumed that the transducer audio was referring to the floor transducers shown earlier. I didn't realize the extent of the transducer audio.


How do the transducers perform in terms of sound pressure levels? It seems that with that much power available and that much surface area you have the potential for a lot of displacement.


I'm really curious as to how large panels will perform for high frequencies. It seems like it would take tremendous amounts of power (which you have) to make that large of a surface move 15,000 - 20,000 times a second.


Also looking forward to the FOSI install. I just finished my FOSI ceiling installation (what a relief to have that done)


Suscribed to your thread.

Quote:
Originally Posted by FOH View Post

Quote:
Originally Posted by stockmonkey2000 View Post

Very interesting build....


How do the transducers perform in terms of sound pressure levels?....


I'm really curious as to how large panels will perform for high frequencies.


+1


Interested as well.

Quote:
Originally Posted by tony123 View Post

I, also, didn't realize that "transducers" meant...the entire audio system? I know nothing about it and will continue to follow along and hopefully learn something! Glad to hear your enthusiasm for it after your first listening experience!

Quote:
Originally Posted by RedTopDown View Post

Quote:
Originally Posted by tony123 View Post

I, also, didn't realize that "transducers" meant...the entire audio system? I know nothing about it and will continue to follow along and hopefully learn something! Glad to hear your enthusiasm for it after your first listening experience!


I spoke with MMan today and he'll be leaving some specifics on the whole transducer setup soon. He will leave the experience to me. I gave a review of what I can after tweaking the system for about 10 minutes. I still have two transducers to add to the left and right channels each since we changed the design mid-stream.


As I stated in my brief review, I'm very impressed with the system and amazed that drywall can produce sound of this calibre. I'm anxious to seal off the plenums for the front L/R, effects L/R, and center channels now and then do some more serious calibration. Still the room is quite hot with a lack of any soft/asborbing materials.


I'll keep everyone posted.

Quote:
Originally Posted by MississippiMan View Post

Ok Guys...here's the Skinny.


Audio Transducers such as the ones employed in RTD's system are decidedly simple things.


1. A 2.2 lb Alnico Ferrite Magnet Structure


2. A 1.5" Edge Wound Aluminum Vice Coil, which is both Frequency contoured, and heat dissipation assisted by the use of Ferro Fluid.


3. They are completely Sealed. Toss 'em in the Ocean for a year and no problem....they'll play just fine.


4. They are encased in a medium Density Composite Resin Plastic whose varying case thickness serves to both dampen and enhance Resonant Energy Transfer.


5. They come in 8 Ohm & 4 Ohm models. 200 Watts Max Output. 100 Watts Continuous.


6. Effective radial/hemispherical dispersion is 8' diameter from the epicenter of attachment.


History:


Curtis Rolen introduced the first effective Transducer designed to resonate "solids" in 1958. In 1962, the basic design still in use today was developed. Improvements on materials, casing design, the use of high temperature Adhesives, and the drastic improvements in Amp / Signal source performance in relation to cost to performance ratios have only served to make what has always been a unique item all the more effective.


That it gets no press, let alone "A/V Enthusiast" respect is due to the fact that it's primary market has been Industrial / Military applications. Also Medical. Also Artistic. And a lot of other things that have nothing whatsoever to do with this Thread, .


What is certain is that it's the efficiency at what the Transducer can actually do when attached to a wide range of solid materials that still have a degree of resonant ability is what makes it something that few have ever experienced...considered possible...and fewer still can even comprehend let alone accept.


But for me...that's where all the fun comes in!


My roots lay in the design and construction of big...as in BIG Sound Reinforcement Systems and PAs. Multiple Drivers in Multiple cabinets...the literal "Wall of Sound" concept. God knows I'm personally responsible for the destruction of many of my generation's Inner Ear Cilla.....and most obviously my own. For me, db Ruled.


I digress.


In Red Top's system, the creation of multiple Driver arrays to accommodate effective dispersion of energy into the room was/is the primary goal. This can be compared to the example of the original "Wall of Sound" first advocated by Julian Hirsch in 1964....where 12 - 5" Full Range speakers were mounted in a specific pattern onto a 8' x 6' Wall enclosure. That led to the use of multiple 12" Extended Range Drivers, Exponential Horns, and Rear Loaded Bass Horn Cabinets to create a uniform "Blanket" of sound in huge areas.


Ouch.


But those same ideas and concepts still hold fast to deep truths. Distribute energy evenly and efficiently across a wide area and both accurate frequency production and dispersion will produce a physicality and presence that is at one more natural and uncolored than most directional speakers.


That's why the very most expensive conventional speakers more oft than not employ "many" drivers arrayed to distribute sound in such a manner as to make perceiving "directionality" almost impossible.


The Audio Transducer accomplishes this by imparting accurately produced frequencies (35 hz -18.5 khz on Drywall ... 20 hz-20 khz on Glass ) into a structural Solid via a focused point, and then the frequencies themselves radiate outward, with the highest Freq. waveforms localized at the center, Mid Range freq. traveling out until they reach their own specific point of resonant saturation, and the Bass freq. traveling out to the perimeters of a surface where their resonant energy can rake advantage of the increased mass of such broader, wider expanses.


Compare a 8' diameter resonating surface to a 8" diameter Full range speaker and what you have is simply a super-sized version...something akin to the huge Driver whimsically portrayed by Robert Zemeckis in "Back to the Future" and blasted by Marty McFly . A silly analogy, yes...but essentially a good visual representation..


So what about Red Top's system? Well if one Transducer can effectively energize up to 8' in diameter of Drywall or Wood...or Fiberglass...or anything resonant, the how well will am array of 2...or 4...or 8 such devices accomplish the same goal? (Shoot....I've used up to 16 Transducers on a 16' x 9' Screen Wall!")


The key to creating something "out of this World" lies in making a structural solid resonate accurately. Bending it's molecular structure to your collective will by imparting just enough energy over a broad enough area to cause it's molecules to do exactly what you want them to do.....aurally speaking.


I have a couple analogies I've used a few times over the last 33 years to help explain why using greater numbers of transducers is not a lesson in redundancy...but rather a cause to an effect.


Using a quantity of such Transducers is a way of doing what a Choir accomplishes. If you take a single vocalist and place him in a Sanctuary, even one with excellent acoustics, he'll be able to only go so far as to filling that space with energy (ie: volume...presence)


Now have 7 other Choir members join him. No one is trying to sung any louder than the solo member was singing, but collectively, the energy imparted into the room produces a significant increase in volume due to the saturation of frequencies into the air. Add another 49 Choir members and....



Now as far as energizing a structural solid.....


Suppose your driving a full sized car along and at the bottom of a hill you run out of Gas. You try to push the car uphill, against resistance and gravity, to the Gas Station you know is just ahead at the Top. You might make it...but what a chore! But hooray! 7 of you Buds come along, lay hands on the Fenders and together you just about effortless move that car up the hill.


Well, brook no mistake, accurately resonating a solid's molecules at any real volume with a single Transducer is a Yeoman's task. Always has been. Background Music? Sure. Moderate entertainment levels? absolutely. Full blown high volume Home Theater or Critical Listening? Best not send a single Boy to do a Man's job. But call out the entire 5th Grade class and see how fast you get it done!.


So now I gotta explain the difference between db and SPL production. (...no more cute examples....I promise...)


The Transducer produces Resonant frequencies.

The Solid it's attached to accurately resonates to said frequencies.

The Frequencies spread out across the opposite surface the Transducer is mounted to, each specific frequency finding it's own specific saturation point where it resonates the molecules to that frequency. No Frequency interferes with another...no cancellation occurs (...when units are properly spaced...)

As the surface of the Solid resonates, the air (ie: volume & pressure) itself that lies against the resonating surface sympathetically resonates, and that imparted energy cascades outward in a chain reaction of resonant energy transference.


The Audio Transducer's 180 degree hemispherical dispersion creates what can be considered to be the most perfect example of a omnidirectional sound dispersion pattern that could be obtained from a flat planar surface. As such, very effective db levels can be obtained, levels that are not accompanied by the normally expected Sound Pressure Levels that would otherwise be expected from such decibel levels.


This decided lack of sound pressure means that many acoustic concerns and considerations are effectively negated to a great extent...if not indeed actually eliminated. (...The Transducer uses this ability to excel at the art of Sound masking...)


For Red Top, the purpose of the design was to deliver the maximum aural and physical presence possible, but at the most comfortable decibel levels. On the past I've used all manner of amplification t accomplish such tasks. Everything from lowly Pioneer and Panasonic Receivers to Sony's and Yamaha s. I've seen Harmon Kardon Citation Amps...McIntosh s...Carver Studio Grand...Krell...and a few European Esoteric s that cost as much as my last 2 cars combined.


But in the end, it's all about simply having enough "clean" power and reserve headroom to be able to deliver unadulterated, accurate amplified frequencies to the transducer, and then using the correct number of devices needed to energize the mass of the solids involved without over taxing a single unit, or trying to over saturate a material with too much focused resonant energy from a single unit or a combined array of the same.


Too whit, it's no stretch to be able to understand that "expense" does not always relate to "effect. Judicious choices of equipment combined with effective design, adequate construction, and yeah....a bit of a crazed desire to do what many feel is patently impossible, can combine to deliver something that defies the accepted conventions of the A/V world.


Hey....did I mention about the Painted Screen?

Quote:
Originally Posted by MississippiMan View Post

Quote:
Originally Posted by MississippiMan View Post

Hey....did I mention about the Painted Screen?


Not yet.....


In actuality, the painting of the 12' wide 16:9 Screen using S-I-L-V-E-R went very well, and pretty quickly. The resultant image was excellent.


But.....



The Primer undercoat, which went on via a Low Nap Roller prior to my arrival on-scene, re-introduced itself. Although RTD did a great job at rolling, and under a straight on examination before spraying the surface, and under normal lighting.... looked pristine, once the High Contrast S-I-L-V-E-R went on, across the top edge downward you could...under the PJ's light and with lightly hued content (Sky...etc,), see some vertical lines (roller marks) that came down into the image area about 6"-8". That's where most such marks occur because of uneven roller pressure, and in the case of such a flat white, if they are not an actual "tactile" ridge, it takes an additional layer of a darker paint to bring them out.


So at this conjecture we have a 2-3 options.


1. Wait for 3-4 weeks to see if the marks fade and frame in whatever dimension / format screen we want.


2. Spray Coat the surface with 3 coats of a ultra Dark Gray tinted Primer and then Re-prime with White and re-coat with S-I-L-V-E-R


3. Cover the wall surface with a Black Out Cloth or similar material and spray on a High performance coating. ***

*** RTD has determined just of late to go back to having a 2.35:1 CHI affair. That might mean the Roller Marks up top might not be any further issue (yay...
)


Here is a collection of shots of the Screen in progress. Note the heavy Duty Air Exchange/Filter System! Suck---Whooosh!





Here are a few shots of the Screen in action:






Does it look good? Is it still worthy despite having a few streaks? You tell me.....and for reference note how the "Adult" people below are stretched out laying prone on a dusty Plywood floor for 2 hours watching Captain America, actin' like Kids up on the first Row of a Movie Theater.


That's Lovin' it....absolutely!






A side note to my previous post:


Please excuse me if my explanation of the Audio Transducer system seems a bit too "layman-esque". I'm driven by the experiences of the past and having to explain such stuff to individuals who are more than just a bit clueless. Well that, and the fact that those with a "clue' often discount such a application out of hand.


But even more so, I don't want to personally expound too greatly upon the aspects and attributes of RTD's Transducer system. That's for him to do...or not. His was essentially a DIY'er thing, with my presence more of a "Helping Hand" and Adviser than as a "Contractor". Lemmie tell ya sumpthin...RTD is the most "Hands On" individual I've ever combined forces with, and the Theater you see on this Thread.....90% of it is all his doing....his efforts built it. It's all more than just impressive....it's almost intimidating!



Anyone who wants any particular further illumination of the Transducer and it's workings may contact me via PM.

Quote:
Originally Posted by RedTopDown View Post

First, thanks to MMan for all his too kind comments in his last post. Only trying to make it all it can be! I'll do the hands-on grunt work to keep the experts like MMan focused on the big stuff!


MMan noted the vertical streaks that can be seen in the bright scenes. I thought I had rolled the primer to perfection, but I guess not. Sounds like prepping to get ahead screwed us up as the primer probably should have been sprayed on.


However, it looks like we will be doing a redo on the screen to support going back on my decision to have a large 16:9 screen and forgo CIH. MMan and I are still talking about it, but the best move may to go with a PJ with lens memory and have settings for zooming to 2.35, large 16:9, and a smaller 16:9 that will have a picture that won't be cut off by the front row seats/heads. More on that to come I guess.


I worked on filling the plenums of the center, left, right, and effects channels with batts and then closing them off with drywall. Pictures below show the batts with the cutout areas where the transducers are located. Pulled out all the insulation and left the paper.








I finished to late Monday night to test the sound improvement out. Got home late Tuesday and couldn't find time then either, but did have five minutes to step into the HT when my boys were watching a movie. I'm pretty sure it made a big improvement. Just didn't have enough time to full listen to it, and I "was distracting the boys and their movie!" I headed down to Ocean City, MD yesterday for the long weekend, so I'll have to post a review next week!


Back on the change to the HT for the screen size, I'm thinking I'll be going with (if we can make it all work!) a 2.35 size of around 14-15' wide. To make that work the front corner walls had to be cut back to allow more of the screen wall to be visible. In the pictures below, you'll see that we have more wall to prep and paint! I think it looks much better just in cutting back the walls to about 40" wide instead of just under 60". Here's a rough before and after look.


BEFORE





AFTER





BTW, the blue tape on the wall in the picture above denotes a 14', 14.5', and 15' wide scope screen. I can go 15' and still have ever seat in the HT see the full screen, so that's my max width. If I went the CIH route, I would want the 14.5' or 15' scope in order to get a 16:9 that was large enough for the room. If I go the zoom route, then I can expand and contract accordingly as needed.


One final update - I ordered all the trim for the room. Lots of baseboard, crown, and casing. With the tall ceiling and large room, I had to go with some beefy moldings. I've got lots of cuts coming my way with those wall bumps! Baseboard is one thing, but that crown will test my patience!


Finally, Happy Thanksgiving to all!

Quote:
Originally Posted by RedTopDown View Post

52 transducers plus we relocated eight and had to fill back in those holes with screws. That's 6 screws times 60 so 360 total. So yes, lots of screws! My drywall finishing guy will not be happy and will think that I went nuts with a 12ga!
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post #6 of 29 Old 10-17-2013, 12:48 PM - Thread Starter
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post #7 of 29 Old 10-17-2013, 02:25 PM
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This bit has had me scratching my head for a while

Quote:
The Transducer produces Resonant frequencies.

The Solid it's attached to accurately resonates to said frequencies.

The Frequencies spread out across the opposite surface the Transducer is mounted to, each specific frequency finding it's own specific saturation point where it resonates the molecules to that frequency. No Frequency interferes with another...no cancellation occurs (...when units are properly spaced...)

As the surface of the Solid resonates, the air (ie: volume & pressure) itself that lies against the resonating surface sympathetically resonates, and that imparted energy cascades outward in a chain reaction of resonant energy transference.


The Audio Transducer's 180 degree hemispherical dispersion creates what can be considered to be the most perfect example of a omnidirectional sound dispersion pattern that could be obtained from a flat planar surface. As such, very effective db levels can be obtained, levels that are not accompanied by the normally expected Sound Pressure Levels that would otherwise be expected from such decibel levels.


This decided lack of sound pressure means that many acoustic concerns and considerations are effectively negated to a great extent...if not indeed actually eliminated. (...The Transducer uses this ability to excel at the art of Sound masking...)

Sound propagates as a wave. I'm not sure I understand the distinction being made between dB and SPL. We measure SPL in dB because of the wide range that our ears are sensitive to. It's just a logarithmic scale. My understanding of the physics is in order for us to perceive a sound as louder, SPL necessarily needs to go up. We "hear" sound pressure.

Also, I don't see the connection between resonating molecules and some other means of energy transfer. Sound propagates as a longitudinal/pressure wave. A resonating molecule/sheet of drywall can create these waves, but the method of propagation is the same. I can see that these walls may be simulating a planar array. In that case the SPL does not fall off the same as it would for a point source. So that at least would would allow you to use a lower input power, but that should be quantifiable as a sensitivity or efficiency of the panel.

I'm very interested in this technology if for no other reason than to learn about something new, but there seems to be very little technical data about these systems that allows a meaningful comparison.

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post #8 of 29 Old 10-18-2013, 06:26 PM
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Quote:
Originally Posted by J_P_A View Post

I'm very interested in this technology if for no other reason than to learn about something new, but there seems to be very little technical data about these systems that allows a meaningful comparison.

Yeah, Mtbdudex was kind enough to set up this thread so hopefully the entire community could learn more about the details and in-room measurements of this technology. Like you, I'm not exactly sure how there is a hemispherical radiation pattern on a flat substrate. Perhaps there's a difference in amplitude, with the transducer as "ground zero" for the highest amplitude ratings.

There's just a lot to get your head around with this type of system. In RedTop's system pics above there is an array of four transducers placed in close proximity to one another for each of the left, center and right channels. What determines the proper spacing of these drivers? If they are all producing the same sound using the same substrate, what is the acoustic interaction between these drivers? How do you prevent comb filtering.

MM had also said in a previous post that the transducer can achieve 20Hz low frequency and 35Hz low frequency in 1/2" drywall.....is there a particular size of substrate used to achieve these measurements? In other words, is that resonating a 54" x 12' piece of drywall in free space? What is the db output level at 20Hz? Is it -50db at 20Hz or is it -3db at 20Hz?? Does attachment of the drywall to 16" OC vs. 24" OC studs make a difference and / or short-circuit the effective resonating area of the drywall?

There seems to be so many unanswered questions and sufficient data to get a solid understanding of how the technology is actually working in a real-world environment. MM has alluded to some measurement data, but nothing concrete has been forthcoming in any posts I could find.

It would also be nice to get some REW measurements of these rooms to shed some light on the subject, along with differences in installation techniques to achieve these measurements.
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I wouldn't pretend to know any more than you guys about this - certainly I don't. MM's posts are my only exposure.

My inference is that the effective radiating area of the substrate is frequency dependent - high frequency radiation would behave more like point source and the lower the frequency, the broader the source size. This makes intuitive sense to me, but may be wrong. I suspect that as a result, the transducer spacing and the size of the free area of substrate (free, as opposed to constrained by screws binding it to framing) relate to the intended high pass point.

According to the link below (Architectural Acoustic, by Marshall Long), an unsupported 5/8" sheet of drywall has a resonant frequency of around 18Hz. I think getting drywall to resonate at good frequencies for reproduction looks totally feasible, though I'm not in a good position to do the math. If you click the link, you can see the context.

Fn is the resonant frequency
P0 is atmospheric pressure
m is mass
gamma is the ratio of specific heats = 1.4 for air (I don't understand this part, right off)
S is the area
h is the depth of the air cavity.

http://books.google.com/books?id=MnYUfErtBGEC&pg=PA202&lpg=PA202&dq=natural+frequency+of+drywall&source=bl&ots=nT203fG1qP&sig=Wq6ph_D4sCrjoNnLf9gaz7yGI4o&hl=en&sa=X&ei=hNNhUozeMqei2wW24oDwBg&ved=0CD4Q6AEwAg#v=onepage&q=natural%20frequency%20of%20drywall&f=false
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No question that a wall can be used as a speaker, and a very good one under some circumstances I would wager. The first questions that come to mind for me have to do with MM's statement that there is some different means of energy transfer that reduces the necessary SPL. That could be as simple as the wall is acting as a line/plane array, but I'm not clear how that would relate to any resonant effects in the room.we're just making waves after all smile.gif

My other questions are really just the specifics that TMcG alluded to. Under what circumstances is a transducer based system preferred over a more traditional speaker configuration. I'm the type that likes data. I'm a believer in we should be able to measure what we "like" to hear, so measurements of what make this better would go a long way towards answering my questions.

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That could be as simple as the wall is acting as a line/plane array, but I'm not clear how that would relate to any resonant effects in the room.we're just making waves after all smile.gif
I think increasing the effective size of the radiating surface is going to go a long way toward mitigating some of the in-room effects we work against. Consider: the speed of sound in drywall is much higher than in air - approximately 20 times based on a quick googling (See table 2) The surface wave on the substrate, induced by the transducer, will be able to propagate along the substrate at a rate that allows (IMO) the resulting sound wave to be considered a plane wave - at least within 1 wavelength (maybe more) of the center (again, that's based on intuition more than experience or education). So if that plane wave coming off the wall is within 1/4 wavelength of the floor or ceiling (or both), I think we can reasonably ignore any interference that would normally be generated by sound reflecting from the boundary (SIBR - and obviously the rest of the mounting wall is not the refection source I'm talking about - I mean adjacent, presumably perpendicular surfaces like floor and ceiling. If that is true, an array of transducers that extends to within around 1.5m of both the floor and the ceiling behaves as a line array. That's a pretty serious advantage - changing (diminishing) the propagation losses and increasing the fidelity (compared to equally linear point sources). For clarity, I got the 1.5m figure by multiplying the wavelength of 300Hz sound by 1.25 - figuring that plane wave down to Schroeder frequency would be adequate, but lower would be easily achievable, given my intuitive statement of this theory. (Edit: I knew it was too late at night for this - the plane wave breaks down at higher frequencies, not lower of course. Plane waves at low frequency is easy; getting plane waves with short wavelengths is tough. Given my assumptions/inferences about 1.25 wavelengths, to get plane wave formation above 1000Hz, the transducers would need to be within about 17 inches of the margins of the wave.)

Have you gotten around to reading Toole yet? One of the major loudspeaker design shortcomings he would like to get around is the propagation losses associated with point-source radiation. (radius cubed) Especially for surround channels, line arrays provide significant calibration advantages for that reason - the sweet spot is broadened significantly and vertical variations are eliminated entirely.

Naturally, the reflected waves from the opposing wall would behave no differently than before (except they are still plane waves, so they may be higher gain than if from point sources), so in especially small rooms this may pose a problem. My brain is too tired to articulate clearly form here - I'm going to bed. smile.gif

I'm totally with you that I would like to see data and competent analysis of the psychoacoustic ramifications. I think this is the right track, but could be wrong.
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post #12 of 29 Old 10-18-2013, 08:53 PM
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As I said in one of my posts in Cowger's thread (copied above), I have a pair of Sound Advance SA2 speakers. They are a fully engineered transducer-based system that requires their own Sound Advance back box that's designed specifically for the SA2s. But even with this complete control over the design of the entire system, essentially making a fully boxed speaker using a transducer-based design, the system still benefits DRAMATICALLY from an active electronic compensation circuit to the point that I am surprised it is not an included accessory. Yes, you get sound....but depending on what you are playing the quality can be varied.

Like JPA, I like data - especially when it comes to speakers and their radiating patterns.

Thanks for the post / link Fred. I think it's funny how they quote the resonant frequency of drywall in free air because, unless it's on some fancy minimal attachment cable suspension, how the heck is that practical information, right? You'd think they would quote acoustic data for typical 16" OC and 24" OC constructions.
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post #13 of 29 Old 10-18-2013, 10:19 PM
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HF, that's what I was getting at with regard to a line/planar array, but I'm not sure why the brochure doesn't come out and say that. That would be marketing gold to HT enthusiasts. As it stands, everything I've read just makes me think of commercials that come on TV at three in the morning with some dude yelling about sealing my gutters with something from a spray can...... On that note, I think I'm up entirely past my bedtime.

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post #14 of 29 Old 10-19-2013, 10:20 AM
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Without any real understanding of the history of Transducers in these application, much can be misconstrued or misdirected. While I do not, nor cannot speak at the level of authority or knowledge that more learned members on this thread can, I do have a working knowledge obtained by over 30 years involvement. I do not mind being held up as being less than learned in the technological aspects and intricacies involved in Audio Theory....and self depreciation comes easily when accompanied by modesty

Almost no one knows that the original design for Sound Advance incorporated the use of the older Rolen Star, but was quickly changed to the use of NXT-based "Exciter" technology...which are simply smaller, less robust and more limited versions of Audio Transducers. This was done primarily because of a desire for efficiency, as well as to create a lighter weight "insert-able frame" with a thinner membrane that could be installed during framing and then "specially" taped / mud'ded and painted over. (...Plaster or heavily Textured coatings were NOT advised...even Wall paper was advised against rolleyes.gif...solids such as Wood were out of the question altogether...) It was also incorporated into 2'x 2' Drop Ceiling Assemblies, but that effort died quickly due to terribly excessive cost..

SA's original marketing strategy was to price the product at an exorbitant level so as to attract people by using the old adage that "if it cost a lot, it's gotta be worth it". , and employ our good fellow Tom Cruise to promote it. biggrin.gif And for the most part it worked, as many such hyped efforts do. But it was not to last.

So many Dealer / Installers had issues with both the expense of the product and the degree of difficulty of effecting a truly seamless installation (..it ain't invisible if you can see it's outline...) that in no way was Sound Advance ever a "Mainstream" solution. This has been borne out by SA becoming defunct and relinquishing their product for distribution to Parts Express, and the price plummeting because of Chinese Mfg. obtained by same. That the SA needed a special EQ just to work effectively even when using a thin, diaphragm-like membrane coated with just paint pretty much says that it was really just a over engineered attempt to bypass the then current Patent held by the mfg of the Rolen Star. Once they went down that road, they were effectively stuck in a rut of their own making. Later on, Stealth Technologies produced a Hybrid NXT / Bass Driver panel that also failed due to both price and installation concerns.

BTW, almost every Audio Transducer system of import I have installed in upper end Home Theaters employed a Parametric Dual 32 Band EQ, especially prior to the advent of Audessey EQ (Stand alone and built-in...) and most Home systems have at least 16 Band EQs in them. No one knows better than I do what advantages such EQs offer when dealing with the variables inherent in using structural solids as speaker surfaces. And even before that, the use of variable Dynamic Range Expanders, and the "OmniSonic Image Expander" all were used to make Audio Transducer systems more "Speaker-like" and increase presence at a time when amplification was at lower yet more expensive levels.

For me, the quality of both signal source and amplification has always been among the most important aspect of effecting a decent system...almost to a fault.
'
Dating back to 1982, my systems down in Florida were among the very first in the US to employ CD players (Harmon Kardon), and from the start, my systems used expensive, Audiophile-level amplification whenever possible. It would produce a chuckle from some to realize that many of my customers were of an average of 65 years "young" and had never owned a stereo beyond those embedded in thier Console TVs. Imagine such people owning a rack of Hamon Kardon equipment at a time when such costly equipment was considered only the realm of true audio purists.

Yet one of my oldest Florida systems on Marco Island, a 21 room / 2 TV Room w/4 Channel Dolby dating back to 1980 had two Radio Shack 100 watt per/ch Digital Receivers powering them, and it's still in operation, with all the original equipment....after 3 hurricanes and over 80% of the Drywall having been replaced over that time span.

Audio Transducers were selected for the Solara 2, the worlds first completely "Stand Alone" Solar Powered home in Tampa (1982)...which was a hoot because the audio system used more power than the Heating / Cooling system, pegging the Output meters in the battery Room like VU meters. biggrin.gif

Through it all both before and after SA's insertion in the equation, Audio Transducers remained firmly rooted in the New Construction / Architectural genres, and NO effort to promote it to mainstream consumers was made. This simply because even in it's most simpler renditions, effective design and installation is of paramount importance. It was over this time period I became used to personally dealing with, and training virtually ever individual or entity that procured the product. Not because I'm a certified Engineer, but because I was about the only individual who really focused on the thing long enough to discover through direct application how best to utilize it over the widest selections of applications. And the uses developed are far more far ranging than can be discussed on this or any 10 threads. Suffice it to say than much of what was related prior to this post in this Thread helps explain in technological terms what I myself could not / cannot. Multiple Driver arrays powered adequately upon specific material can accomplish things most cannot believe possible. That's not hyperbole...it's a simple statement of fact.

What is NOT a fact is that I have ever stated that the Use of Audio Transducers in Home Theater or Critical Listening environments is absolutely preferable to conventional Speakers. That has been unfairly attributed to me by either intentional or unintentional misconstruing my remarks that to effect stated that in many ways, they can be preferable to many people...and to that I stand my ground. I know this, having designed and installed hundreds of systems that have met with absolute satisfaction.

No one, not a single person on this Forum would love to see the attributes of the Transducer held up to scrutiny and observation than would I. Do I myself have the ability to do the extensive testing so desired of late? No. Can I cajole the owner at HAS to do so? Perhaps, but I cannot give any effective promises or timeline thereof. Does that mean I am intentionally withholding data? I cannot believe anyone with any degree of sense could construe that as being the case. The truth in fact is that I could inundate the Forum with testimonials.....literally hundreds, some in excess of 25 years in operation and 3-4 changes in Home Owners... but they would all be "opinions" by people who only know what they have and enjoy. And that cannot wash with people who have a overriding desire to know absolutes.

So speaking of absolutes...I would absolutely enjoy fielding questions regarding either of the Transducer applications shown on this Forum, most applicably RedTopDown's Theater if the more extreme end of the scale is to be considered, and Cowger's system if a more representative example of normal design is to be considered. And i would do my best to expound on other types of applications as well.

What I don't want or need or comments about my lack of engineering fortitude, nor expressions of disdain for my attempts to explain in layman'esque terms the workings of a product that I hold close to my very existence. If a question / s are asked, it should be with the expectation that I will do my utmost to provide an effective answer....and those answers are not to be construed as being intentionally misleading nor in anyway promotional. Just me responding as best as I can in a courteous manner, and expecting the same in return.

I appreciate that AVS is a "Science-based' Forum...but it sure the 'ell isn't a "Slashdot.Com" !

Mostly. redface.gif

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post #15 of 29 Old 10-19-2013, 02:05 PM - Thread Starter
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MM -
This 3 1/2 year old thread, Surround Sound Without Speakers?, it seemed to never reach closure.
Did you and Kal R ever get together?

Again, all I am asking for is basic in room measurements of end result using REW and a calibrated mic.
Very simple to do, so I'm scratching my head at the lack of that data being available.

I know you have the ability to do that, have you ever measured your many-many builds?

Forget the 3rd party lab tests, I realize that can cost $$k's to secure the lab, but real world in room measurements, surely that is within your expertise to have them.
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post #16 of 29 Old 10-19-2013, 03:10 PM
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Quote:
Originally Posted by mtbdudex View Post

MM -
This 3 1/2 year old thread, Surround Sound Without Speakers?, it seemed to never reach closure.
Did you and Kal R ever get together?

Nope.  Not high on my agenda and not found locally.


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post #17 of 29 Old 10-20-2013, 08:28 AM
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No one, not a single person on this Forum would love to see the attributes of the Transducer held up to scrutiny and observation than would I. Do I myself have the ability to do the extensive testing so desired of late? No. Can I cajole the owner at HAS to do so? Perhaps, but I cannot give any effective promises or timeline thereof. Does that mean I am intentionally withholding data? I cannot believe anyone with any degree of sense could construe that as being the case. The truth in fact is that I could inundate the Forum with testimonials.....literally hundreds, some in excess of 25 years in operation and 3-4 changes in Home Owners... but they would all be "opinions" by people who only know what they have and enjoy. And that cannot wash with people who have a overriding desire to know absolutes.

So I guess spending $100 on a USB microphone and running free REW software with the transducer in different types, sizes and thicknesses of substrates in different construction methods is out of the question....

If you want, send me a transducer (or a few), along with how you would like to see the test set up and I'll be happy to post the REW graphs and return the transducers to you.
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post #18 of 29 Old 10-20-2013, 01:52 PM
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MM, please don't take my posts as confrontational, or as an attempt to "call you out." I certainly don't mean it that way. However, perhaps as a result of my particular line of work I tend to be skeptical of something like this until I understand how it works. And in this case more so perhaps because it almost seems too good to be true as it seems to go against some pretty well established principles. As an example
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All Walls "AND" Ceilings are solidly packed with Pressure Blown Cellulose Insulation (...goes in Wet, dries into a compact dense layer....) except the Partion Wall up front and as stated, that is packed with dual layer of R-19 Kraft Faced Fiberglas.

So adverse non-harmonic resonance should be effectively held to non-issue levels.

Using Transducers, their specific attribute is that they generate concentric dispersing wave forms of every frequency, radiating out from the epicenter 360 degrees, and in doing so also create a 180 degree hemispherical "half-Globe" of omni-directional sound off the chosen surface.

The very act of exciting the molecular structure of the chosen material, and especially the room-side surface of same, also delivers the benefit of "masking"...or refracting incoming standing wave forms. Transducers are used extensively in Private, Government, and Military circles for security sound masking applications, and as sound masking for unwanted intruding vibrations from elctro-mechanical sources.

In other words, a active battery of Transducers under power effectively squashes, or in the least greatly reduces the chance that a standing waveform of any pressure level will adversely impart a non-harmonic resonance into a surface so equipped.

Installed in rooms where acoustics are deemed terrible, they can produce a pretty darn Flat response across the entire frequency spectrum. Now that is not to say they are perfect, nor that they work miracles for all applications and every instance. However........overall....when properly designed and installed, they often accomplish something akin to a miracle by eliminating the need for a gross effort and expenditure for acoustical teatments.

........

The bolded statement above gives me pause. Thinking about this from a basic physics standpoint would seem to indicate that in order to cancel a room mode, the energized panel would need to move on the order of the same wavelength (maybe 1/4 lambda) or have a displacement on the order of the amplitude of the offending frequencies. It doesn't seem that a constrained panel would be able to do either of those at any appreciable SPL. Sound "masking" (particularly speech masking) is another topic all-together, as I don't think operation in the modal region would be important.

Also, I would be surprised if anyone would argue that a transducer based system would be superior in ALL proposed installations. However, for the product to be successful, there clearly must be some scenarios where it is superior. The clear example is space constrained rooms. Obviously a transducer based system has the advantage here when compared to traditional floor standing speakers. The topic of modal cancellation above is another example. This would be a HUGE benefit to sound reproduction in small rooms. People go to great lengths to address modal issues in their listening spaces, and often sacrifice lots of space and money. If a transducer based system will cancel these modes, that is potential savings on many fronts.

The question is, under what other circumstances are these systems superior, and what data is available to support that. Unfortunately, it doesn't appear that data or technical publications are available to explain this or to allow side-by-side comparisons.

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post #19 of 29 Old 10-21-2013, 12:42 PM
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J_P_A,

Actually, your responses and Q's have been a example of restraint.

I know how decidedly different the concept of "Transducer'ing solids" is...and hard it it is for those with considerable training and experience to accept. Such has always been the case, though mitigated once those types actually got some experience with the things. I myself wholly discounted the potential in Home / Office / Commercial applications, having gotten my own feet firmly planted in Pro Audio Sound Reinforcement design and Cabinet construction. It was a plaintive statement made in the original enclosed literature of the Rolen Star, (...something that looked like it was composed in 1955... rolleyes.gif ...)stating that Glass constituted the optimal surface of the Transducer that led me to try it out on Front & Rear Car widows, at a time ('77) when the only other Amplification out there beyond "Power Boosters" was a Fosgate Amp that delivered 50 "clean" watts x 2, but both drew almost 10 amps off a 12 Volt system (...Headlights would "strobe while driving!...) and cost over $500.00 (...the Transducers only cost $14.50 at the time...)

But even then, both the unique aspect of having the Glass and surrounding Body cavities reproduce sound, combined with the elimination of the need to cut 6" x 9" holes in Kick Boards or Rear Decks made it very desirable to many....if they heard it demonstrated. There you have a good example where the Transducer filled a very real need for many people...at the time. Yet all the while I was so involved, I also supplied units to some College Fellows at Butler University in Indy, and they absolutely sold a TON of them to Students who were placing them in the Ceilings of their Dorm Rooms, and driving them with the type of Gear only College students and Returning Military Servicemen possessed.(...Audiophile Hobbyists notwithstanding...) Even then I refused to even consider that Drywall could measure up to Glass....so I never even bothered to try.

......until my efforts to secure Venture Capital to produce a EQ/Amp - Transducer Package met with failure. I dropped the whole thing for about 11 months until the opportunity came to install the big system on Marco Island, and once the Drywall went up and the system could be demo'ed in the "raw"....with no furnishings or carpet, I got such effusive responses from so many people that it made me beat my head against the wall for being so stubborn.

So you see, my own myopia kept me from realizing that if installed driven adequately, the Transducer could in effect make drywall sound very good. Better than even a Audiophile could imagine possible. Was it up to "reference standards". No...but then again, even then many such people were getting guff from Wives about their huge Floor-standers in the Family rooms, and many were the esoteric speaker systems that got booted up into the attic storage. But it was just exactly those type individuals that required that a Transducer system be given more thought than simply applying them and wiring them up.

Drywall or Paneling had to be effectively installed....no sloppy workmanship. If a Exterior Wall had insulation, so did the opposing interior wall to prevent the interior wall from having a hollow, booming sound. Amplification HAD to be clean, and posses enough headroom to allow for the use of enough power without clipping. Equalization was almost standard, down to the very most basic systems. And if "Gut Thumping Bass" was desired, the use of Crossover networks, and either Mid-High Range & Bass-Dedicated Transducer circuits were used, or Sub Woofers were also considered mandatory. In short, everything any current day enthusiast employs to assure themselves of the best possible sound was also expected of those earlier systems. And all of that long before such things were considered mainstream.

And as far as Room -to- Room House-wide audio, there was never a question that true invisibility combined with decent signal source / amplification created a demand that outstripped that of conventional speakers....especially when the "Better Half" came into consideration. Yeah...certainly I rode the coat tails of that aspect over the years....but along the way several thousand individuals enjoyed Audio systems that would never have happened otherwise. It simply became a case where my own standards were what made those systems be all that they could be...and I transferred that mindset to every Dealer / Installer....or they were NOT a Invisible Stereo Dealer/ Installer. Period.

So let's do a Bullet List here.

  • Audio Transducers can do a spectacular job properly engineered and installed. Will such measure up to everyone's standards? Certainly not, but then again...what system does?
  • Is the room's own layout and design, combined with the materials it is made of a factor. absolutely. But then again, all rooms used for Audio have those issues to contend with.
  • When is a Transducer system preferred? When Cosmetics, Cost, and room design dictate such. And in many instances, that can cover a very wide variety of circumstances.
  • Can a true, professionally designed and installed Transducer system featuring adequate Transducers and Power deliver "Theater-like" sound? Absolutely.
  • Will the last mentioned item be satisfactory to all? It would be more than presumptuous for anyone to say so, and I have NEVER said anything of the sort.
  • Would effective and comprehensive Audio testing do Transducer-based systems a favor, or belittle them? I have to vote with the "favor' side, but I'm somewhat biased. Go figure.

Referencing the last point, I stated that in the past, when needed, and when effective measurements were taken to adjust to EQ especially large, open areas such as Meeting Halls, Churches, Ballrooms, Auction Halls, Restaurants, Bistros, even modest Live venues......a plethora of different applications, the end result was always the same. Some pretty amazing results that perplexed and astounded the Audio Engineer "hired" to do that EQ set-up. Usually, Frequency response was within 3 db across the board, excepting Bass response below 60 hz, and High Frequency response above 16-17K. Depending upon the materials, sometimes the Midrange between 1000 & 4000 khz had a timbre that needed contouring, because it was overly predominant, but that was almost always "material related" (...the use of too-thin or not dense enough substrates....) Too Thick / too Dense materials needed a corresponding boost None of that was published....it was always a "Work Related' effort.

Bench testing, or the type done in a Lab setting was always considered both too expensive and too limited in scope, and as I pointed out and others have taken umbrage with, not really going to be effective in judging the performance potential across a wide scope of real world applications. The Transducer simply does not allow for "Free air" testing, or that done on limited sized / unsupported materials. Even in the case of my providing such, I cannot believe that any one set of tests done in one singular instance...on one type or even two different substrates will serve to convince skeptical individuals. No sir.....that has always and only been the domain of actual experiencing an application in real life use. I will admit, almost sheepishly, that many would value the expressed opinion and results provided by a 3rd party before they would ever accept such from me. Sad...but all too true.

It's just not easy......never has been, and as stated before in this thread by others, it seems that mostly, the determinations made or that have been made are confined to those of a Empirical nature.

But I would change that.....I really would
.** If those among you can help, that would be great....just know that it is not, nor ever was my intent to ask for such. In fact, as both cowger and RedTopDown will confirm, it was always my primary intent that they themselves be happy, and I always had my own concerns about the postings of explanations on this, a Forum based on science, not simple conjecture and/or opinions.

** Anyone who has the means to do such testing, with the Transducers mounted and driven correctly (...within reason...) is welcome to do so. I'm pretty certain I can get the factory to send out some units sent out gratis, along with the Mounting discs. as long as it is no issue that I advise all such efforts to make sure that there can be no "Well you didn't do it right..." kind of fall back.

Much of all this parallels my own years of involvement in DIY Screen design. Everything I have accomplished was done without schooling, degrees, or any extensive lab testing. Simply because I'm out there everyday doing what I do, and I have the ability to produce...and refine my results via actual experience. That it works...a lot of Videophiles could care less...and some are adamant that in no way can a DIY Screen ever measure up to it's Mfg counterpart. I feel strongly that I have effectively trashed that sort of reasoning....but when the stated opinions of those who feel strongly that their experience and knowledge flies in the face of my own and hundreds of other users stated end results, the same impasse crops up. Also the same request...."Where's the beef?"

It's simply this way....I can supply the ingredients...and the recipe....even walk a person through every step of the way. But they usually have to do the cookin'. Obviously I cannot be "The Little Red Hen Who Baked The Bread" in this situation, because no one...or at least those who doubt the application most vehemently....is going to "bite" down, chew, and swallow anything I take out of the proverbial oven.

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post #20 of 29 Old 10-21-2013, 01:04 PM
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Quote:
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So I guess spending $100 on a USB microphone and running free REW software with the transducer in different types, sizes and thicknesses of substrates in different construction methods is out of the question....

If you want, send me a transducer (or a few), along with how you would like to see the test set up and I'll be happy to post the REW graphs and return the transducers to you.

No...it's not out of the question....just not as easy "time wise" as you make it sound.

I will admit that if anyone has such opportunity to do so across a wide range of apps, it certainly would be me.

But for instance, at present I'm getting a 13 room w/2 Theater Home Show display in order..... http://www.avsforum.com/t/1491572/128-2-35-1-theater-project-w-3-week-time-limit-warp-factor-9-5-engage
.....and I have several other commitments that take precedent. Yet even with such true and valid reasons, it's all to easy for some to view such as being just "excuses".

It might be whimsical for some to realize that these days, 90% of my postings are done via "Speak to Text" on my Galaxy IIs excepting the ones posted after 1 am biggrin.gif I'm on the job at least 12 hours a day...and at 60 years old, that doesn't amount to having much free time. But your desires are noted....and will be considered, as I also hope that you few peers might consider taking up some of the slack (...TMcG, I heard you...and I will try to oblige....PM me an address. mtbdudex....you too.)

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post #21 of 29 Old 10-22-2013, 10:52 AM - Thread Starter
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MM - really you are to busy to take measurement(s) on some of your fabulous rooms?
For $100, you can easily supply many here with fact based in room measurements.....to ask TMcG or I to re-create an install and then measure.....hmmmm

Heck, for free you can at least install this RTA and show us that data, it's a start.
Not as granular as a full freq sweep, but....
https://play.google.com/store/apps/details?id=radonsoft.net.rta&hl=en


So, my simple request:
-download RTA, it's free
-play pink noise 20-20k
-run RTA, capture that response at MLP and other seat(s)
-show room size/layout/seats/transducers/subwoofers (if used) etc
-post pict


OT;
You've helped and guided many here in DIY screens, me included, thank you.
(I said this in recent PM between us, want it public also)
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post #22 of 29 Old 10-23-2013, 08:51 AM
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I can try to put it on my agenda....but I'm hoping that cowger and RedTopDown can do similar tests and provide separate any absolutely unbiased reports. But brook no mistake, I do appreciate the "asking" and the acceptance that any such results I might provide would be taken at face value. """

I do intend to get a couple units to TMcG, once I get an address.

And no, I realize better than anyone that effective testing must be done on applicable surfaces, but that does not mean that a pair cannot be quickly placed up over a ceiling in the most rudimentary manner, tested, and the results taken placed in the according light. But as I said, such tests must be weighted to correspond within the peculiarities of the Transducers. For instance, you would not get any real measurement at 1 watt / 1 meter because the Transducer requires at least 3-5 watts to produce anywhere near an appreciable volume from a structural solid. And as stated before, the very omni directionallty factor, and the propagation of sound through free air resonance without the added boost of moving air physically via cone travel suppresses spl levels below what actual db levels are produced, once a "power to volume" efficiency is reached.

Anyone who does testing...or reads the results of such tests would have to be willing and able to read into those results a markedly different way of construing what they represent. I have tried to relate this before, to some degree of non-acceptance...but I see that as simply a carryover of the usual standard of non-familiarity breeding non-acceptance. That is nothing new.

Doing testing for those of you who have requested such and not complying in a "priority" based manner does not constitute any unwillingness, simply a "no time to focus" type circumstance. Certainly you show that expense in not a factor.....and that of course will play into the ability to eventually respond in kind.

As far as my being busy....you have no idea. biggrin.gif Between my doing systems to pay my bills, installing a Star Field, taking care of my Farm chores, and trying to rest, yeah.....such testing for my own sake has not been on my agenda. For instance, i just came down from the attic in the Home show display, after pulling 4 bundles of Fiber optic and pushing the ends through the 1 mm holes in the Ceiling....and I'm resting my back. So I have a little time to compose this response.

I have only 10 days to get ready for a major show where 35,000 souls will troop through my Theater, and be cocked and loaded to give their own "Thumbs up or Thumbs down" determination. You can bet that does take precedent over just about anything else. Once that show starts, I will be there every single day for 3 weeks and 3 weekends.....9 am to 7 pm....demo'ing the System and Video. Any free moments in the evenings, and/or before the Show will be spent running down Lead requests and making appointments and scheduling work that will commence after November 24th. At the end of that time frame, you can be absolutely certain I will have a slew of "I gotta have my system in before Christmas! Can you do that?" along with "I gotta have my system in before the Bowl games....can that happen?"

.......and then there is my time spent responding to requests from DIY'er on this Forum. Once again.....I get no slack from those requests......but ya gotta know i'd have it no other way. wink.gif

So what might seem to be recalcitrance against what to some seem a more than reasonable request is really just a case of my being wholly restricted to a frantic timeline, and have a decided lack of the ability to stop and focus so as to oblige such requests.

But I will try...so please don't fault me for my lack of immediate response.

Meanwhile, keep the discussion going. Ask those with systems to give more complete evaluations, as their determinations should / do carry some weight.

To quote James T. Kirk;
"I'm laughing at the superior intellect"

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post #23 of 29 Old 04-30-2014, 04:41 AM - Thread Starter
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This thread stalled out....and got buried among many others...

A few days back on a facebook Home Theater group https://www.facebook.com/groups/5007104247/ page a member there suggested to use transducers as a soultion for front center channel instead of a in-wall speaker.

So I did a search to see where this thread went or conclusions made...

MM, it's been 6 months now, any data to share?
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post #24 of 29 Old 04-30-2014, 05:13 AM
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Quote:
Originally Posted by mtbdudex View Post

This thread stalled out....and got buried among many others...

A few days back on a facebook Home Theater group https://www.facebook.com/groups/5007104247/ page a member there suggested to use transducers as a soultion for front center channel instead of a in-wall speaker.

So I did a search to see where this thread went or conclusions made...

MM, it's been 6 months now, any data to share?

The transducers shown above remind of NXT transducers.

http://en.wikipedia.org/wiki/Distributed_mode_loudspeaker

An attempt was made to popularize them for automotive audio, but not seeing any mainstream commercial applications..

A project leader in that effort can be reached though his consulting company DLC Design Audio: http://www.dlcdesignaudio.com/

Trust me, the effort was well documented at the time!
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post #25 of 29 Old 09-22-2014, 12:24 PM
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I have plans in the works to have a very well respected AVS Member who does Pro Audio & Video Calibration conduct a wide variety of measurements on both the Transducers and my Screen coatings.

In the end, a non-involved unbiased source of testing on the Transducer will be looked to as being more dependable a benchmark, especially when the Tester already has a good reputation within the Forum Community, and particularly involving quasi-esoteric and esoteric level A/V systems.

Doing so will cost me far more than making such an attempt myself, but the essence of validity that having such data come from a outside source will be priceless.

To quote James T. Kirk;
"I'm laughing at the superior intellect"

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post #26 of 29 Old 09-22-2014, 04:13 PM
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Invisible speakers have been commercially viable for good number of years. Many didn't sound very good but the better brands with proper DSP equalization can sound surprisingly good. Here is an example of Amina speakers in my company's design center:



There are actually six (6) invisible speakers there. Two for left, center and front. We put in two to increase the power handling. We bring people to that room and ask them where the speakers are. They never find them. When we have them touch the wall and feel the sound coming out of them they are quite shocked that such fidelity can be extracted from invisible speakers.

Here is more detail on this and other solutions in an article I wrote for Widescreen Review Magazine: http://www.madronadigital.com/Librar...uralAudio.html. As you see there, they are using an array of small transducers.

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post #27 of 29 Old 09-23-2014, 06:18 AM
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Yes, the concept shown in the post above has enough past reference to be determined as being a well establish product.

Actually, a more correct term is "Exciters" as the units being used are based around NXT Technology, and are essentially the same product as Sound Advance, and in a couple of instances, the Stealth Audio of times past....where a hybrid of Exciters and a Low Freq. Driver are used behind the Thin Honeycomb Faceplate. They also present a nearly omnidirectional dispersal pattern

In fact, they do not "Use the Wall" but rather emulate a wall surface by blending in the large diaphragm-like surface contained within a Back Box, which must be inserted into new or existing Framing, and blended in using special Tape and Drywall compound.

The fragility of such installations usually requires that such a product be installed at or above Head Height or in the Ceiling to avoid a elbow or shoulder denting or even puncturing the flush mounted Diaphragm
.
They are not inexpensive...and require the same outboard EQ processing as did both the aforementioned products. And a Mounting Box or Frame...all of which adds further to the expense. If anything more aggressive than Paint is overlaid on top of the lightweight, Honeycomb like Diaphragm, considerable equalization is necessary. They are however more efficient "power-wise" than actual Transducers that energize and "excite" structural solids.

Having originated in the UK, duplicating the Plaster Wall finishes was essential if it was to be marketed in any real numbers beyond the original concept of "Wall Hung" Picture-like panels with Graphic Art applied. It was just such examples that were first exhibited at CEDIA '97 London, where I was in attendance and showing off a 16' x 8' Framed wall Partition with 8 Rolen Star Audio Transducers.

This sort of concept was and is still marketed to the higher end clientele, and they are not an inexpensive option....requiring specific outboard EQ to compensate for the suppression of sound caused by even the overlay of Wall Paper and thinner Paints. Nor are they sold direct, but only through authorized Dealers who must either employ the finishing skills needed to interface with the given structural materials, or depend upon a local Contractor to do so....which can be problematical at best. Retro-fitting such a product into existing structures is almost totally cost and logistically prohibitive....but as in other such things, where there is a Wallet there is always a way.

However, just as Sound Advance did before, they will find a market in the Individual who is both needful of a completely invisible Speaker system (...IF they are installed perfectly....) and whose budget can accommodate them. However under a direct comparison to the Transducers used for structural sound, there is in fact no real comparison.

To quote James T. Kirk;
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post #28 of 29 Old 09-23-2014, 08:25 AM
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Quote:
Originally Posted by MississippiMan View Post
Yes, the concept shown in the post above has enough past reference to be determined as being a well establish product.

Actually, a more correct term is "Exciters" as the units being used are based around NXT Technology, and are essentially the same product as Sound Advance, and in a couple of instances, the Stealth Audio of times past....where a hybrid of Exciters and a Low Freq. Driver are used behind the Thin Honeycomb Faceplate. They also present a nearly omnidirectional dispersal pattern

In fact, they do not "Use the Wall" but rather emulate a wall surface by blending in the large diaphragm-like surface contained within a Back Box, which must be inserted into new or existing Framing, and blended in using special Tape and Drywall compound.

The fragility of such installations usually requires that such a product be installed at or above Head Height or in the Ceiling to avoid a elbow or shoulder denting or even puncturing the flush mounted Diaphragm
I am unclear if you are referring to my post or that of Arny's. Yes, the Amina's are DMLs. The excitation though is a super strong aluminum composite. That in turn is coupled to a board that is more robust than the drywall you have around it. You certainly can't dent it easily. We have a sample unit that we show customers and it has endured huge amount of abuse. The corners are chewed up some but the surface of the panel is as smooth as ever. These are not the thin consumer NXT type speakers. They are exceptionally heavy and strong for what they are.

That said, with these or any other such design, you do have to be careful to not damage them electronically. As doing so obviously requires ripping out the wall. To that end, the Amina speakers come with a protection box and we use limiters upstream in the form of DSPs in Crown amps to eliminate any danger of overload.
.
Quote:
They are not inexpensive...and require the same outboard EQ processing as did both the aforementioned products.
They are expensive by DIY standards as they are sold through the custom channel. BTW, Triad sells the same speakers as Amina so they are another brand to look for in this regard. The EQ however is not mandatory. That is something we do because we have speciality in acoustics and quite comfortable programming the DSP in Crown Amps using London Architect. I suspect all other installations are put in as is and without any kind of DSP.

The other key component here is making sure to roll off the bass relative to the power level as to not cause the wall to literally shake itself apart. You can damage the paint, or make other items hanging from the wall elsewhere to fall off and such. In the context of this thread which I think is home theaters, this may not be an issue. But in the common usage we have for them which is in living rooms, kitchens, libraries (where you can actually use a wood panel in front of them), these are the things we take into account in programming the DSP and sizing up the units.

Quote:
And a Mounting Box or Frame...all of which adds further to the expense.
There is no mounting box. What you have is essentially a patch in a drywall. Imagine cutting a 1 foot by 2 foot part of your drywall, and patching it with another. That by itself is not expensive. What gets expensive is that if you want them to be totally invisible, then you want to spend the extra dollars for level 5 drywall finish and that of course is expensive. So yes, these products as we use them are luxury items.

Quote:
If anything more aggressive than Paint is overlaid on top of the lightweight, Honeycomb like Diaphragm, considerable equalization is necessary. They are however more efficient "power-wise" than actual Transducers that energize and "excite" structural solids.
Again, there is nothing lightweight in the Amina/Triad units I have been talking about. Here is a picture of the back side:



The honeycomb again is made of super strong aluminium.

Quote:
Retro-fitting such a product into existing structures is almost totally cost and logistically prohibitive....but as in other such things, where there is a Wallet there is always a way.
They are pretty easy to put in. Again, if you can patch a drywall, you can patch these. So retro is not an issue at all. But you are right that per my earlier comments that the typical application is a high-end one, looking for completely invisible look.

Quote:
However, just as Sound Advance did before, they will find a market in the Individual who is both needful of a completely invisible Speaker system (...IF they are installed perfectly....) and whose budget can accommodate them. However under a direct comparison to the Transducers used for structural sound, there is in fact no real comparison.
I have not looked at Sound Advance much but from the bit I know they did use a stretched panel with the issues you talk about. The Amina/Triad as I have been explaining, are transducers coupling to solid surfaces through an excitation/amplification plate.

I apologize for not having read the thread carefully enough to see what you are calling transducers used for structural sound. So I am unclear on the distinction you are trying to make with respect to the products I have been talking about.

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post #29 of 29 Old 09-23-2014, 11:33 AM
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OK....I saw Triad's display at InfoTech & CEDIA last year, so I can relate to your description.

As for the practicality issue, any In-Wall device that has enough potential to damage a wall's structure, or dislodge fasteners or Tape/Mud joints is simply not well designed for such use. Clark Synthesis Absolute Tactile Transducers were extremely adept at producing extended Bass as well as soaring highs, but unfortunately the very robustness that let them activate solid Flooring made them wholly inappropriate for "in-Wall" use. Something akin to having Trolls inside your walls wielding Sledge Hammers. It wasn't long into their production that all mention of use for Full Range reproduction was dropped from their literature, while yet they still retained the ability. Later on, they produced more dedicated, Low Freq. units that also can in at more reasonable price points.

Basically, that would mean that to be able to obtain the performance desired across the Lower Mid range up to the High Freqs, the Amina/Triad design had to incorporate a material sturdy enough to accept the reproduced Bass Response as well. According to your description, they do exactly that, yet the "exciter panel" can also produce enough energy at the edges to impart harmonic resonance that does not propagate as easily into the surrounding area. This is due to the disparity between the structural rigidity and density of the wall vs the flexibility of the Exciter panel, and a insufficent union joining strength between the two.

This can also lead to a situation where since the energy cannot easily dissipate outward, the edges of the Exciter Panel will start to non-harmonically "Vibrate" once certain volumes are reached / frequencies are injected. This can create a lot of adverse interaction between the two different materials, and produce what many call a "Howl". So absolutely, I can see where a judicious use of Cross-over points to exclude bass freq. that come in below...say 100hz would be highly advisable if any real amount of volume potential was going to be sought after.

Even with all that, the design as stated shows how far such products have come beyond the Sound Advance concept, and how the trend back toward exciting the solids of the room has caught on and garnered acceptance with at least some audio engineers.

Now it will boil down to a "Cost vs Acquired performance" ratio that will determine acceptance. I feel that is where a more simplistic system such a one that uses Audio Transducers to activate the Drywall itself holds a big advantage. Personal Bias notwithstanding.

BTW...I like your Sig.
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In accordance to what we both do, it's an all important aspect to strive for.

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