DIY Flat Panel Speaker Love

[geosand]

So has anyone used a panel product like this before: https://www.homedepot.com/p/Amvic-Mu...-301619814-_-N . Its high density EPS which everyone seems to like (28 PSI compression, which is even higher than XPS foamular 250 @ 25 PSI). Higher compressive density should mean better HF propagation. But whats unique is the sculpted front surface which contains and additional 98 small protruding rectangles! Looks nice. But I wonder if this could be ideal as those smaller rectangles may also have their own resonance points (which is a good thing as the more resonance points the lower any one resonance may be and thus the smoother the FR should be.) Yes it is 2" thick which may not be a plus (or could be who knows) and its only available in 2'x4' sheets. But the size and the front sculpting may be a plus for WAF :-). Any thoughts?

[Mahdokht]

I ordered a box of these from Home Depot to experiment with. I've also built a foam cutter so I can cut thinner sheets and cut some sheets around 1/3" at 21x34" for testing. They sound pretty good, but I don't think I like them as much as the XPS foam. They also have some sort of weird resonance in the 300-450hz range when turned up fairly high that sounds terrible. I'm going to do some more experimenting with them for a while and I haven't played with the left-over sheet I have with the protruding squares yet, so I'll let you know how that turns out. Home Depot also messed up and sent me a second box of these (as though I need more EPS in my life...) so I'll have plenty of material to mess around with for a while. Oh, I've also only been using the DAEX30HESF-4 exciters.

Since this is my first post here, I should probably also put in a little background. I'm part of the Tech Ingredients wave of interest in these speakers, but I know some of you have considerably more experience with them since I've spent a lot of time just reading through almost every post in this thread and some of the others on other forums. My first set of these speakers were pretty much a copy of the foam/acoustic tile combo set that TI showed in his video. These sounded pretty good in conjunction with each other (especially after using a DSP to flatten out the response), but I've since learned that this is a fairly naive approach and misses some of how DML works. My second version is currently using these EPS sheets, but I am going to mount them to the wall at 4 points and support the exciter so that it isn't just attached to the foam (probably use some soft foam attached to the wall to cup the back of the exciter to provide support). I'm also going to make some XPS ones of the same dimensions when I get a chance to compare the two.

[Kornbread]

IIRC, as the panel became more free to move and stabilizing the exciter by giving it something solid to push from, were two of the largest positive contributors to improving the sound.

[MisterD]

Hi folks!

This is my first post here. I signed up to learn a bit about speaker building and thought I’d start with making some “dml” foam panel / exciter speakers.
I asked a question over at audiocircle, about driver placement of two exciters on one panel - but was told by just one person that they’d never heard of that sort of placement - nothing more - so I want to ask this here.

Have any of you tried using two exciters on one panel - with them placed in exactly the same spot but across from each other - one on each side of the panel front and back - then wiring so that they work together, one pushes while the other pulls? Basically giving the panel twice the “shake” in exactly the same spot.

I was thinking also, of using a wooden or metal “U” bracket that would perform as a spine (spline, as some like to call it), with both sides of the “U” holding the backs of the two exciters - and using no frame or panel suspension. The bottom of the “U” could be solidly attached attached to a pole for the speaker stand or mount..

Any thoughts about this idea?

Duane

[Mahdokht]

Which exciters were you going to be using? Also, would you be using them out of phase with each other? In phase seems like they would just be cancelling each-other's input.

Depending on the exciters you are using, I think you will find that one provides plenty of output on a foam panel in terms of volume (I'm assuming you are using the 1" x 24" x 24" panels to start with). As far as placing multiples in different places, I haven't played with that yet but from my reading it seems like it would be hard to get a placement where you won't have some unwanted interference with each other. At least it seems like it would be hard for the home-gamer without some very high-end modeling software or analysis tools. I have seen a paper on optimal placement for multiple exciters that looked pretty interesting though. If I remember correctly, they were placed relatively close to each other in a slightly off-set line.

[Kornbread]

Hi folks!

This is my first post here. I signed up to learn a bit about speaker building and thought I’d start with making some “dml” foam panel / exciter speakers.
I asked a question over at audiocircle, about driver placement of two exciters on one panel - but was told by just one person that they’d never heard of that sort of placement - nothing more - so I want to ask this here.

Have any of you tried using two exciters on one panel - with them placed in exactly the same spot but across from each other - one on each side of the panel front and back - then wiring so that they work together, one pushes while the other pulls? Basically giving the panel twice the “shake” in exactly the same spot.

I was thinking also, of using a wooden or metal “U” bracket that would perform as a spine (spline, as some like to call it), with both sides of the “U” holding the backs of the two exciters - and using no frame or panel suspension. The bottom of the “U” could be solidly attached attached to a pole for the speaker stand or mount..

Any thoughts about this idea?

Duane

Somewhere on this, or the other very long thread, it is noted that the radiation pattern is not symmetrical across the panel, in particular, the treble tends to emanate from the area directly in front of the exciter. Some have gone to the trouble of thinning or dimpling the area directly in front of the exciter to improve the highs. Although I can imagine there are benefits of this mounting arrangement, I would have to question what affect placing one exciter directly in front of the other would impart on the treble. If the benefits of the front to front arrangement prove beneficial, what about mounting a small traditional tweeter to the back of the front facing exciter?

Mahdokht I have read several papers/forum posts about the placement of multiple exciters. If you watch the youtube dml video posted elsewhere in this thread, I think it will become apparent how complex, or downright chaotic, a dml panel behaves during sound reproduction.

Agreed, we need a real and precise software solution to driver placement/panel size/panel material/etc. IMSHO, there are just too many variables at play to 'get it right' by haphazardly sticking exciters on a sheet of materiel.

Like many other internet spawn, there is a lot of 'opinion' being presented as 'fact' in regards to dml panels.

The price of admission is cheap so I encourage everyone to give it a try, but please report back to us with what you discover. While it may give us the warm fuzzies to gush over our latest revelation ... we prefer measurements.

[MisterD]

Guys, thanks for the replies.

I’ll be using the “thruster” exciters and wiring so that they’re out of phase - one pushes while the other pulls. My thought was that -maybe- I could get greater panel extension that way and possibly better bass out of the 2’ square panel. I can see how the upper frequencies might emanate from the location of the exciter; I think that won’t change much with two in the very same spot, but I won’t know ‘till I try them. Another reason for me wanting an exciter on each side is ‘cause I’ve been reading how the sound seems to come from behind the panel - I think that’s because most exciters are located on the reverse... How does the panel sound with a single exciter mounted only on the front?

Anyway, I just rounded all panel corners today, then went all around with the router to round the edges. I’ll be sanding and hopefully giving them a first coat of diluted wood glue, darkened with black food coloring sometime tomorrow. I’ll post again after I get a bit further along.

[geosand]

Speaking of measurements, can someone recommend the cheapest/free "measuring system" that will give usable results preferably using a smartphone (i.e., what software recommendation?). I am aware of REW but I don't currently have a Win Laptop. I have an ZTE Axon 7 running Android 7.1 so plenty of processing power and a good audio chipset. If theres a cheap external mic that would improve results that wuld be helpful as well.

[Kornbread]

miniDSP Umik 1 and the Dayton PE umm6 are both usb mics that come in around $70. Of the two, I think the Umik 1 is the preferred mic.

Grab a cheap used laptop for price of a Friday night meal and load REW or ARTA.

https://www.roomeqwizard.com/

http://www.artalabs.hr/

[geosand]

miniDSP Umik 1 and the Dayton PE umm6 are both usb mics that come in around $70. Of the two, I think the Umik 1 is the preferred mic.

Grab a cheap used laptop for price of a Friday night meal and load REW or ARTA.

https://www.roomeqwizard.com/

http://www.artalabs.hr/

Thanks Kornbread! ARTA looks very sophisticated.

So I have an old 8" tablet running Win 10 and 2GB memory. Its slow but should be enough for Arta and REW I hope...

Still though if anyone else has suggestions for a smartphone let me know.

[MisterD]

Hey folks!

I’ve been listening to and enjoying my DIY DML panels since October last year (2019). I decided to make my first set from the 1” 2’x2’ Foamular panels sold at Home Depot and I’m using the “Thruster” exciters.

Seems I can’t find the same XPS stuff in 4x8’ sheets locally. If anyone knows of a supplier in the Socal or central California area (around Bakersfield?) please let me know.

I think I’m ready for some larger panels for better bass. Has anyone tried this 1” XPS Foamular material in a 2’x4’ panel speaker and liked their sound? Unless I can find some 4’x8’ sheets, I’m thinking of bonding two 2’ square panels together, edge to edge, to make a 2’x4’. Thoughts?

[Bob Johnson]

New Member - just started to explore the DML ideas with the exciters. Currently have 2 1/4 plywood 4x4 panels hanging on pipes with 2 25MM dayton exciters driven by the 2020 amp. Tried driving full range , highs and mids were fine but the panels rumbled and could not dampen the low frequency's sufficiently. But now have them passively crossed over at 2K and they lose all the extra resonances. Ran a few sweeps and found very little distortion. Yes 2K is high but I added a few ported boxes to handle below 2K and the difference is quite dramatic.

My idea is as follows - Try this wood material for mids/highs and some open baffle woofer designs - perhaps 2 15's in a open baffle dipole design. Bi Amp with a Mini DSP for the adjustments. Thinking the Goldwood 15's can go up to about 1-2k . has anyone tried this. It brings together the open baffle+ dipole idea for both sets of drivers. Never seen this done yet . Looked around for any examples and didn't find any.

Also has anyone tried real tonewood? Specifically Spruce ?

And are there any DYI events in the northeast coming up soon? I would like try this out there.

[Dukk]

Cool post. When I was in retail I sold NXT 'picture frames' and they were super cool but pricey in the early 2000s. I have a neat little set that are about 4"x6" and they always get comments if I leave them out.

Going to have to play with some exciters this year.

[Kornbread]

But now have them passively crossed over at 2K and they lose all the extra resonances. Ran a few sweeps and found very little distortion. Yes 2K is high but I added a few ported boxes to handle below 2K and the difference is quite dramatic.

My idea is as follows - Try this wood material for mids/highs and some open baffle woofer designs - perhaps 2 15's in a open baffle dipole design. Bi Amp with a Mini DSP for the adjustments. Thinking the Goldwood 15's can go up to about 1-2k . has anyone tried this. It brings together the open baffle+ dipole idea for both sets of drivers. Never seen this done yet . Looked around for any examples and didn't find any.

Also has anyone tried real tonewood? Specifically Spruce ?

And are there any DYI events in the northeast coming up soon? I would like try this out there.

I was wanting a one driver, crossoverless speaker but after toasting a lot (6?) of the daex32 (I think the large panels used were becoming too excited and forcing the exciter past its excursion limits) the thought occurred to use the exciters as conventional drivers are with a smaller lighter exciter for the migs/highs and a bass shaker, on a separate panel, for the lows. The experiment got cut short as the frustration level increased due to the reliability issue and a warning that no further exciters would be replaced. I have yet to see someone use a bass shaker for the low end. You game?

Somewhere in one of the other large threads, someone did use tonewood for their panel. Don't remember their results.

InDIYana 2020

[Dukk]

Ordered up 3 pairs of different exciters last night. Time for some experimenting