Hi trenth. Stupid question - why are you so set on getting tonewood? Using tonewood is no guarantee that a panel will perform well in all frequency ranges. Materials with bad tonal qualities like carbon fibre, aluminum, polystyrene can make great sounding panels. Most plywoods used for panel speakers are made from wood that don't necessarily have tonal qualities.
I've been temped to try that myself many times, but never have. One tricky part is that it comes pairs of pieces that are each only about 8-1/2" x 21". So I expect you would have to glue them together. Here are a few other sources:
stewmac
americantonewood
alliedlutherie
Eric
PS, wrote this a few hours ago but just realized I never hit send!
trenth,
What do you mean by "soft ply in between the hardwood veneers"? As far as I know, these tonewood panels are a single layer of wood.
Or are you saying that is what you have in mind to do?
Eric
twocents,
I can't answer for trenth, but the reason I would be interested to try it would be for its sensitivity, due to its low density. The thing that might hurt is that the stiffness across the grain will be very low, and I don't know for sure what the effect of that would be. I also suspect it will need the addition of some good damping, to counter the ringing at its resonances.
Those who have been hanging around this forum for a while will recall the JMC Soundboard that was made with "350 year old resonance spruce" tonewood.
JMC Soundboard
Eric
While I agree that damping does give very short impulse responses with cone drivers and enables me to turn up the volume with lass distortion ( cone breakup) .
But It does soften and smooths the sound , creating a very boring sounding unit lacking in dynamics.
This sounds very good on classical and smooth jazz, but heavy metal rock tends to sound like I have two pillows strapped to my head, with a totally lifeless sound.
This has the same affect on a dml panel.
Alu foil and silicone give no rigidly to the panel only damping, similar to using mastic and bitumen on the side of a washing machine.
In the end I compromised with my 3inch paper cone midrange drivers and used thin strips of blu-tack which had the same effect as the mastic damping but kept more of the detailed sound.
But it still sounded too smooth and boring for rock music.
Once you know how damping deadens the sound of any driver even though the impulse response looks lovely, it is not for everyone.
Certainly not for me.
Steve.
My impression when I saw your recent video with the proplex panel, was that when you tapped it it seemed quite substantially damped. No ringing at all. It might have more internal damping than you realize. If you had REW you could make some measurements and we could know for sure.
Eric
Eric.
I am pretty sure that on many occasions I have mentioned that the proplex panel is a heavily damped material, that is why I tapped it with the screwdriver to demonstrate how damped it was.
I do not need REW to tell me this.
That is why I recommend using strips of paper or the poly film to increase the dynamics and detail of the panel, similar to other heavily panels such as ply.
Steve.
I am pretty sure that on many occasions I have mentioned that the proplex panel is a heavily damped material, that is why I tapped it with the screwdriver to demonstrate how damped it was.
I do not need REW to tell me this.
That is why I recommend using strips of paper or the poly film to increase the dynamics and detail of the panel, similar to other heavily panels such as ply.
Steve.
Is it with EQ?
From the waterfall of the 15cm full range, we see it needs for almost all the frequencies 6 cycles to get a 20 to 25dB attenuation. Interesting. I wrote quite recently a Python script to get the spectrogram from an IR, maybe I should add the view in cycles. If I remember there is a paper from D Griesinger about that (cyclogram).
EQ is a good possibility to get the desired on axis FR. In my understanding, there is a prerequisite which is to have a smooth directivity from the speaker building.
Christian
JohnnoG sent me a 2ft square proplex panel, and all I did was glue on the exciter.
The performance of sound was excellent, with a smooth frequency range from 40hz to 20k .
What was not to like.
But it is not perfect.
It was designed to withstand the weight of a forklift truck.
The round flutes and the polythene give good internal damping with low colouration.
but it is still a heavy inefficient panel that needs a lot of driving.
And being a heavy panel, even though it has a frequency response up to 20k, it has a tendency to sound dull.
I noticed this problem on heavy panels when listening to the podium panel speakers when they were first demonstrated in the UK.
I did wonder if scaling down the thickness of this proplex panel would improve things?
There are options to improve this by using a whizzer cone maybe, or using my strips of paper or my polythene film techniques.
My thoughts were to use the proplex panels with my eps panels and roll off the high frequencies on the proplex panels, at what frequency I am not sure as yet, but it could be anywhere between about 100hz to 20k.
My original thoughts were to use the proplex panels between about 60hz and 300hz and let the subs handle the very low frequencies.
This would remove any hint of box colouration.
To be decided.
Steve.
Pixel1.
The proplex panel is 6mm.
Because of the flutes the panel also flexes differently across and along the panels flutes.
Which I think also helps, especially when using a square panel.
Steve.
The proplex panel is 6mm.
Because of the flutes the panel also flexes differently across and along the panels flutes.
Which I think also helps, especially when using a square panel.
Steve.
Makes sense.
no doubt
Agreed. A square panel is really only "square" in the DML/bending sense if the stiffness is the same in both directions. If the stiffness in each direction is really different, the one way to be absolutely certain that the panel doesn't act like a square is to cut it into a square!
Eric
@spedge The Link shows there are Two Types of Round Fluted Sheet where the Thickness is 6mm @ 5.6Kg per Sheet and 5mm @ 3.4Kg per sheet.
The sample dimension you have used at the above weights will be 6mm @ 0.93Kg and 5mm @ 0.56Kg.
It does look like the 5mm might bring more as a Single Use Material and looks the better material to produce a composite as suggested.
It would be nice to learn who is the manufacturer, as there might be rejected boards for quality reasons, maybe the Thickness is on certain rejects too thin to meet the 5mm Spec. A Sheet as thin as 3.5mm @ approx' 2Kg, might be discovered to be produced on occasion that is classed as reject board ?
Food for Thought
https://entrypointusa.com/product/impactboard-fr-2500/
The sample dimension you have used at the above weights will be 6mm @ 0.93Kg and 5mm @ 0.56Kg.
It does look like the 5mm might bring more as a Single Use Material and looks the better material to produce a composite as suggested.
It would be nice to learn who is the manufacturer, as there might be rejected boards for quality reasons, maybe the Thickness is on certain rejects too thin to meet the 5mm Spec. A Sheet as thin as 3.5mm @ approx' 2Kg, might be discovered to be produced on occasion that is classed as reject board ?
Food for Thought
https://entrypointusa.com/product/impactboard-fr-2500/
I am suffering from a really bad cold at the moment, but I presume you ment "the one way to be absolutely certain that the panel doesn't act like a square is NOT to cut it into a square!"
Steve.
No Steve...
Because the panel is anisotropic, cutting it into a square is the one way to make sure it DOESN'T ACT like a square.
Eucy
Steve, do you mean to say you don't prefer damping at all on your DML panels? Like even the damping provided from framing in those plywood ones you showed me?
Also, are there some examples of CF panels people have made, and where can I source this material?