DIY Flat Panel Speaker Love

[Unbiasedsound]

Since that paper was written 10 years ago with no new info it could also mean it was a failed DML design attempt. There are a lot of these type of thesis papers of DML tech that lead nowhere. I pull my ideas from others successful designs like the Podiums, BERTAGNIS, Yamaha NS-20/30 ear speakers, sony apm's etc....I even use other successful techniques like XRK's foam core enclosure with some modifications and techniques from the Karlsonator on my frames oooppps giving away another secret technique. LOL

Like I said before the most coherent in sound is when only 1 exciter is used per panel because when more then one exciter is used the sound waves over lap each other and there is no way to completely stop them from overlapping. The only way to do this is to use large separate panels with only 1 exciter per panel basically like STACKING separate panels together.

Bertagni's and my modified Bertagni panels are two ways but there are techniques use to minimize and control the vibrations from overlapping each other to a degree but there is no way to completely stop them unless using separate panels. My modified Bertagni 2-way panels sound really good but they do not sound as coherent/accurate as my panels utilizing only a single exciter.

Also I am not saying the CBT array using DML tech cant be done, its just that no one has SUCCESSFULLY done it yet. Maybe you might be the one to prove me wrong. I don't mind because my design everytime I hear them play puts a huge smile on my face. LOL

My main goal for DML panels is hi fidelity sound quality and everything else is secondary.....I am not here to make novelty panels that can be used for room decorations and or surround sound/back ground music.

[bradley.s]

This paragraph makes me think MAPs are good candidates for Floyd Toole's speaker placement in conjunction Keel's CBT flat array. This paper was written in 2010. Today, we have inexpensive multichannel DSP as well as very inexpensive digital amplifiers that can make something like this accessible to DIYers.

"Multiactuator panels can be used alternatively to
dynamic loudspeaker arrays for wave field synthesis with
added benefits. Due to their low visual profile, they can be
integrated into the listening environment as part of the
room decoration. Furthermore the radiation of multi-
actuator panels is evenly distributed across the listening
area and over a wider frequency band. This characteristic
helps in merging the individual secondary sources of
wave field synthesis correctly for a large listening area. In
addition when multiactuator panels are used in non-
anechoic wave field synthesis setups, room reflections are
less correlated to the direct sound than those radiated
from pistonlike loudspeakers, and thus constructive and
destructive interference of sound is minimized. As a
consequence the localization precision is not degraded by
room acoustics as with dynamic loudspeaker arrays. The
proper sound localization and the minimum degradation
provided by multiactuator panels are important for wave
field synthesis installations"

[bradley.s]

These guys call it a MAP (Multiactuator panel.) But as of this paper they didn't try it in the form of a CBT. Maybe they did in a later paper.

https://www.researchgate.net/publica...t_Developments

[Unbiasedsound]

Personally though I wouldn't do a line array with DML/BMR panels as it defeats the purpose of using larger panels plus its not needed since the panels throw a huge soundstage horizontally as well as vertically.

[bradley.s]

If I were to do a line array type of DML or I should say BMR type of speaker I would use multiple separate panels with one exciter on each panel instead of multiple exciters on a single panel.https://www.youtube.com/watch?v=L5zJ4C9mYLk

If the CBT array works you could do 24 individual exciters. I'm trying to see if you can cut the exciters in half and still get a CBT. If that works the next step would be to see how few exciters you could use to produce a CBT. Maybe you could get away with as few as 3,2,1,1,1 with a five foot CBT.

[Unbiasedsound]

New to the board and this thread. Some questions that hopefully haven't been asked too many times before.

On panel material: Has anyone tried Polyisocyanurate foam board. Its denser and thus a bit heavier than say foamular 150 and maybe a bit more dense than foamular 250. https://www.homedepot.com/p/R-Matte-...stomer_reviews

On reducing board resonances, in the original Tech Ingrdients video, during the part on reducing resonances, just before he mentions using weights placed at the 2/5,3/5 locations of the sub-divided rectangles, he quickly mentions you could also just cut holes at those locations. Has anyone tried this or determined how big/small those holes would be? Seems like it might work better than adding weights/mass at the resonant points?

Go for it and see for yourself.

[Kornbread]

Somewhere in this thread or the diy thread, there is discussion about cutting grooves into the foamboard that basically serves to sever vibration propagation. For example, out of one large sheet of blueboard, or whatever panel is chosen, a basic 'two-way' could be formed. While my experiments have come to a complete standstill due to very little free time and the aggravation caused by dealing with their unreliability, I have often though about creating a multi-panel in this fashion using 'bass shakers' for the bass, and exciters more suited for the mid and treble ranges. My thoughts are that over-excursion combined with tin leads on the daex32 were the cause of the failures. Like an ordinary driver, the motor must be able to control the panel but once the vibrating panel overcomes the exciters ability to control the panel, it basically beats the exciter to death. This was the thought process leading to a more conventional two-way design using bass shakers for the bottom end.

[geosand]

New to the board and this thread. Some questions that hopefully haven't been asked too many times before.

On panel material: Has anyone tried Polyisocyanurate foam board. Its denser and thus a bit heavier than say foamular 150 and maybe a bit more dense than foamular 250. https://www.homedepot.com/p/R-Matte-...stomer_reviews

On reducing board resonances, in the original Tech Ingrdients video, during the part on reducing resonances, just before he mentions using weights placed at the 2/5,3/5 locations of the sub-divided rectangles, he quickly mentions you could also just cut holes at those locations. Has anyone tried this or determined how big/small those holes would be? Seems like it might work better than adding weights/mass at the resonant points?

[Kornbread]

And don't forget the Russian's business (cannot remember his nor his company's name), who posted way back in the diyaudio thread and went on to use the panels in professional sound reinforcement.

No, I have not heard commercial iterations of the technology. It would be quite revealing if people started showing up at the diy events with dml panels.

I feel NXT had strong potential in the autosound industry but now the effort seems to have disappeared. Curious as to what happened to that effort.

[Unbiasedsound]

Kornbread besides your own panels have you heard other DML manufacturers like Podiums? Bertagni's? Goebels? Sheet control? NXT? etc

[Kornbread]

I have a pair of Apogee Acoustics Caliper sigs, and although my experiments with exciter technology were not as extensive as some, I could never mistake the sound of any of my admittedly experimental dml panels for an Apogee planar.

Was I able to achieve better sound reproduction than 'WalMart' offerings? Sure.

Did they offer a diffuse type of sound? Yes.

Does the technology have potential? I believe so.

[Unbiasedsound]

If I were to do a line array type of DML or I should say BMR type of speaker I would use multiple separate panels with one exciter on each panel instead of multiple exciters on a single panel.

Just saw a new vid of Sheets controls panel and from the sound, it seems they made improvements to it. https://www.youtube.com/watch?v=L5zJ4C9mYLk

[bradley.s]

At present: 5, 3, 2, 1, and 1 exciters. That's half the number of drivers appropriated in each of the five sections of the CBT24K. If it doesn't work I'll have a lot of work peeling them off without damaging them. If it does work I'll create a center channel with a horizontal virtual CBT. So very DSP and labor intensive but low material costs. Although, maybe not labor intensive compared to making an enclosure and crossovers.

[Unbiasedsound]

Interesting design. How many exciters per panel? Let us know the outcome, good luck.

[bradley.s]

This is probably going to fail but I'm doing it anyway. I picked up a composite honeycomb panel at the carbon fiber store. Composite honeycombs, cloth facing. I coated one side with epoxy resin then layered stands of carbon fiber that fans out as it goes down the panel. I left one side uncoated, just the plain cloth material. Panel is 1/2" thick. Each piece is 2.75" wide cut at different lengths. I plan on using these to make two tall, thin panels with digital signal processing -- FreeDSP -- to make it behave like a curved CBT array. Because it's a flat CBT without an enclosure I'll place it away from the wall like an electrostat. Maybe the virtual CBT will appear to arc backward to send the soundfield forward and also arc forward to send the soundfield into the wall for reflections.

Again, it will probably fail. On the other hand, if it does work it will be an inexpensive CBT array.