DIY Flat Panel Speaker Love

[Gary.M]

Re: DIY Flat Panel Speaker Love

"the standard 2'x2' project panels " - Remind me, are these in 1" extruded polystyrene?

Playing with the DAEX32Q-4 if you pluck the metal suspension vanes with a fingernail, the ones that will be closer to the panel have quite a "ping" while those to the rear are much deader. Perhaps a thin coating of something to damp any resonance in the metal will help with the sound?

[rmeinke]

Re: DIY Flat Panel Speaker Love

"the standard 2'x2' project panels " - Remind me, are these in 1" extruded polystyrene?

Playing with the DAEX32Q-4 if you pluck the metal suspension vanes with a fingernail, the ones that will be closer to the panel have quite a "ping" while those to the rear are much deader. Perhaps a thin coating of something to damp any resonance in the metal will help with the sound?

This may be a very good idea Gary(and especially since you haven't listened to it yet). I hear more exciter with the DAEX32Q-4 than I am accustomed to when standing behind the panel. I actually have one right now in the listening room flipped so the exciter side of the panel is facing the listener. I didn't really play it much as we have been out of town but the initial test was that it didn't sound noticeable different... my thoughts were that listening flipped might give the panel more needed presence but was a "no go". But this line of thought is not associated with your modification.

My thought after listening to these and not making any real improvements in sound quality with EQ was to cut off the second spider to make the exciter more compliant (which is a good thing on really light panel material like XPS) but your idea is easier and a quick test. Hard to believe that enough output from the spider would make its way onto the panel and be strong enough to give the mid range that unpleasant signature but these exciters are stronger than you imagine so not ruling it out.

Now I need to find a material around the house that will work good. If I can't find any good materials I might have to resort to masking tape or something like that. The stuff you use to hang pictures would be good... just not sure if we have any around the house yet... hmmmmm.

Here we go making work again... :-)

[Gary.M]

Re: DIY Flat Panel Speaker Love

Yeah, maybe masking tape is a good non permanent thing to try. Other possibilities would be a thin layer of a rubber like contact cement left to dry (flexible yet damping)... a thin layer of polyurethane sealer, or even some pva? (Needs to be able to remain flexible)... just thoughts.

I also thought that cutting off one of the sets of metal vanes might be something to try but its non reversible. It does look like you might be able to remove the screw and spacer that holds the rear most set and then just fasten the front set.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Once I got home from work, I plucked at the metal suspension on mounted and unmounted exciters and all of mine tight and solid feeling... fairly dead.

To test, I grabbed all 4 metal spiders and damped with my fingers... no change and possibly for the worse... I lifted the panel by the exciter and listened so the panel was completely undamped and this seemed slightly better but not significant in any way.

Swing and a miss...

[Gary.M]

Re: DIY Flat Panel Speaker Love

Ah yes I see. I was holding it between my fingers. If I press it gently on some solid surface it is much deader. Not completely dead though. Consider that we are intensely exciting this item and everything it is made of. If you were to sweep the audio range I'm sure you'd find suspension related resonances. Transducers tend to do everything you don't want them to.

[Gary.M]

Re: DIY Flat Panel Speaker Love

Just did a frequency sweep on my bench with it pressed against the bench top. It seems it might be prone to a bit of a buzz in the 250 - 350Hz range. Also there might be a peak in the 2.5kHz region, these were both noticeable with it being held in free air too... Will be different on a panel of course.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Just did a frequency sweep on my bench with it pressed against the bench top. It seems it might be prone to a bit of a buzz in the 250 - 350Hz range. Also there might be a peak in the 2.5kHz region, these were both noticeable with it being held in free air too... Will be different on a panel of course.

I did some sweeps over lunch today at fairly loud levels and really couldn't hear any questionable buzzing... a little resonance possibly around the 200Hz range but not anything strong or definitive. The upper frequencies had nothing noticeable either.

My post from last night probably wasn't very clear, but I did firmly hold the 4 sets of metal spiders with my fingers and did not notice the coloration go away. Slightly more damped in the high frequencies while resting on my (damped) stands. When I just lifted the panel from the exciter with all spiders being suppressed by my fingers some of the high frequency air returned but the coloration was still present but possibly, if only very slightly, reduced. Heavy damping might make this coloration more noticeable?!? I won't be playing with that exciter more except possibly cutting off 1 set of the steel spiders but really hate to do that...

Anyway, back to the drawing boards.

But on the positive side... I listened to my old 1/16" Baltic birch panels with the Thruster exciters and have to say it sounded better than what I remembered. Sensitivity was not as reduced as much as I had thought. Have to test further to confirm. The point... not a bad panel material and has potential with some light balsa support along the edges to keep the panel from flopping and a layer or 2 of a hard finish might also firm them up more as well. Very nice sounding but this is compared to the 24"x24" XPS panels and DAEX32Q-4 so a comparison to the 24"x30" XPS and Ultra exciter is needed.

But for anyone listening 1/16" Baltic birch is a panel material you might like given certain design criteria (aesthetics, material you have available, etc.).

[augerpro]

Re: DIY Flat Panel Speaker Love

Forgive me if this is a stupid suggestion, I haven't followed this interesting thread too closely, but could you try using one of those flat diaphragm drivers from TangBand instead of the exciters?

[Gary.M]

Re: DIY Flat Panel Speaker Love

Forgive me if this is a stupid suggestion, I haven't followed this interesting thread too closely, but could you try using one of those flat diaphragm drivers from TangBand instead of the exciters?

Can you point to a suggested driver?

I have some more exciters on their way to add to my arsenal. Also I have bought a couple of 3" pro wideband drivers with the idea of removing the basket and adapting the motor. I think these little exciters may be a weak point.

[Gary.M]

Re: DIY Flat Panel Speaker Love

OK, Tangband do have an interesting possibility!

http://www.parts-express.com/tang-band-w3-2088s0f-35-rbm-micro-subwoofer-4-ohm--264-951

Only question is how rigid the coupling from the voice coil through to the DML panel would be. A disk of suitable material would need to be added on top of the speaker diaphragm to clear the rubber surround and couple to the panel. The driver would have to be supported.

Can you point to a suggested driver?

I have some more exciters on their way to add to my arsenal. Also I have bought a couple of 3" pro wideband drivers with the idea of removing the basket and adapting the motor. I think these little exciters may be a weak point.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Hey Brandon! Yeah, i see the logic.

There are a few things to consider here:
* The larger the voice coil, the less HF extension that should be expected. So while the cone is flat, you would still probably want to connect the voice coil directly to the panel.
* The driver would have to be supported via spline mounting. Given that the panel edges would need some serious suspension/clamping. With such large XMax I have to think that the panel would work in a quasi pistonic/DML mode depending on the frequency?!?!
* While I think some of the exciters are a little more fragile than others, tend to think the NXT has worked hard and performed due diligence to create the exciters we have today. Its a complete assumption of course and others have used small full-ranges on the forums with mixed success and no home runs to speak of so tend to think NXT and others have us pointed in the general direction to DML.

Gary, heck... give it a shoot... there is little to lose here other than a few fairly inexpensive drivers.

[Gary.M]

Re: DIY Flat Panel Speaker Love

Second thought on those Tangband drivers... I think perhaps the suspension compliance is too low for our needs. I think we need a stiffer suspension as the mass load the panel offers is much larger than the cone on the driver. Amongst other things too soft a suspension would allow the panel to pull the voice coil off centre unless everything was aligned perfectly and gravity didn't have its way over time.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Second thought on those Tangband drivers... I think perhaps the suspension compliance is too low for our needs. I think we need a stiffer suspension as the mass load the panel offers is much larger than the cone on the driver. Amongst other things too soft a suspension would allow the panel to pull the voice coil off centre unless everything was aligned perfectly and gravity didn't have its way over time.

Its been done, and the spider and surround would keep the VC in alignment well enough so long as the panel is suspended properly and the large XMax would allow the driver to move the panel large distances. Someone over at AC had a custom exciter created that had a large Xmax which moved the panel in more of a pistonic motion at lower frequencies so these small subs would operate very similarly. But overall, not an ideal exciter...

[rmeinke]

Re: DIY Flat Panel Speaker Love

one more thing...

One concept to kick around... what does everyone think about settling on a easy to build, simple, common "reference" panel and exciter so that we can begin to compare different designs?

We seem to go sideways more often than we go forward and we can not honestly say whether *this* design sounds better than *that* design, etc., etc.

Of course personal preference vary and there will be disagreement is what "sounds best" to each of us but have to think that we would at least get closer and help to continue to improve the sound quality of our flat panels.

Thoughts?

Guys, any feedback on this? This might be the best way to really determine progress and differences between the multitudes of panel designs and exciters we are using?!?

Thoughts??

[Gary.M]

Re: DIY Flat Panel Speaker Love

Its been done, and the spider and surround would keep the VC in alignment well enough so long as the panel is suspended properly and the large XMax would allow the driver to move the panel large distances. Someone over at AC had a custom exciter created that had a large Xmax which moved the panel in more of a pistonic motion at lower frequencies so these small subs would operate very similarly. But overall, not an ideal exciter...

I've read all of that thread, and keep an eye on it. I've seen people propose this sort of thing, and in particular the impressive driver you mention, but I've not seen any significant follow through.

Btw that Tang band driver has no spider...

I don't think a large Xmax is required for this, I'd be looking for linearity and the ability to operate consistently over a wide frequency range.

I think the exciters we're using are intended for mid-fi. The fact that good (but not excellent) results are reported is encouraging. If you search billionsound in China you'll find these exciters in their OEM form. I think they are being rebadged Dayton. In quantity they are just a few dollars each.