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A Study of DML's as a Full Range Speaker
A Study of DML's as a Full Range Speaker
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Old 24th February 2020, 03:29 PM   #1191
tagis is offline tagis  United States
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Hello Group,
I have been following this Thread for awhile it seems quite active.
The latest recordings BurntCoil sounds very similar to what I was hearing with gator boards. I am attributing the sound quality to being a chromatic effect rather than damping. With the layered ply's the sound frequencies have different speeds and does not appear to be a constant so it shows up as a doppler shift. I am trying to come up with a experiment to confirm my suspension of doppler shift by using REW sonograph and multiple frequencies.
Cheers
Steve
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Old 24th February 2020, 08:16 PM   #1192
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Hi Steve and welcome.

Do you mean in addition to the usual speed differential by frequency?
It would be interesting to learn more.

Burnt
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Old 24th February 2020, 08:25 PM   #1193
DMLBES is online now DMLBES
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Quote:
Originally Posted by tagis View Post
Hello Group,
I have been following this Thread for awhile it seems quite active.
The latest recordings BurntCoil sounds very similar to what I was hearing with gator boards. I am attributing the sound quality to being a chromatic effect rather than damping. With the layered ply's the sound frequencies have different speeds and does not appear to be a constant so it shows up as a doppler shift. I am trying to come up with a experiment to confirm my suspension of doppler shift by using REW sonograph and multiple frequencies.
Cheers
Steve
If I am not mistaken Burnts latest recordings were done without any damping.
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Old 24th February 2020, 08:28 PM   #1194
gazzagazza is offline gazzagazza  New Zealand
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I'm looking at a source of 3mm bamboo ply here and thinking about those tall narrow panels.
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Old 24th February 2020, 09:49 PM   #1195
tagis is offline tagis  United States
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Burnt, What I am trying to wrap my mind about is the tone quality that the Gator Board and thin plywood produce. I am thinking along the line of optics since that is my physics background and the chromatic dispersion that one has when passing light through glass. If I am not mistaken each ply is at a different grain so in my model it would be like different index of glass and has the wave "sound"propagates through it would either speed up or slow down thus having a "dispersion" of acoustic frequencies.

To explore this I am thinking that one sends a 440Hz tone for 23 milliseconds and record the sonograph "Spectrograph" of the response it should only see the 440Hz tone if the time resolution can approach the tone burst of the 2.3 milliseconds.

One could do this for several frequencies to get a dispersion response

DMLBES does your foam panels have a similar tone quality?
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Old 24th February 2020, 11:07 PM   #1196
xrk971 is online now xrk971  United States
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A Study of DML's as a Full Range Speaker
I think doing a swept tone FFT in REW will give you the info you seek. The excitation swept from say 20Hz to 20kHz. The 2nd through 9th harmonics are displayed as a function of frequency. This would reveal the dominant order of harmonic distortion and the relative levels of each one over the whole frequency band.

Then just plot the sonogram and that will tell your where the energy is stored/decays.
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Old 24th February 2020, 11:31 PM   #1197
DMLBES is online now DMLBES
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Quote:
Originally Posted by tagis View Post
Burnt, What I am trying to wrap my mind about is the tone quality that the Gator Board and thin plywood produce. I am thinking along the line of optics since that is my physics background and the chromatic dispersion that one has when passing light through glass. If I am not mistaken each ply is at a different grain so in my model it would be like different index of glass and has the wave "sound"propagates through it would either speed up or slow down thus having a "dispersion" of acoustic frequencies.

To explore this I am thinking that one sends a 440Hz tone for 23 milliseconds and record the sonograph "Spectrograph" of the response it should only see the 440Hz tone if the time resolution can approach the tone burst of the 2.3 milliseconds.

One could do this for several frequencies to get a dispersion response

DMLBES does your foam panels have a similar tone quality?
Any panel material that does not have some sort of damping will result in that same type of hollowish reverb diffused type of sound that you heard from Burnt's sound clip.

It seems people forget the simple steps of DML 101. Two beginner damping techniques is the water/glue mixture and or paint. For wood though I wouldn't use the water/glue mixture instead I would use Latex acrylic paint.
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Old 25th February 2020, 12:15 AM   #1198
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Don’t forget room reflection

DM where are your recordings and images?. It would be good to compare and, as you are a damping advocate, a detailed look at how you damp your panels would help everyone as you say we keep on getting it wrong.

Last edited by BurntCoil; 25th February 2020 at 12:20 AM. Reason: It’s late
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Old 25th February 2020, 12:22 AM   #1199
BurntCoil is offline BurntCoil  United Kingdom
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Quote:
Originally Posted by xrk971 View Post
I think doing a swept tone FFT in REW will give you the info you seek. The excitation swept from say 20Hz to 20kHz. The 2nd through 9th harmonics are displayed as a function of frequency. This would reveal the dominant order of harmonic distortion and the relative levels of each one over the whole frequency band.

Then just plot the sonogram and that will tell your where the energy is stored/decays.
That makes sense X. When I am up to speed on REW I will try it. Thank you.
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Old 25th February 2020, 12:33 AM   #1200
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Quote:
Originally Posted by tagis View Post
Burnt, What I am trying to wrap my mind about is the tone quality that the Gator Board and thin plywood produce. I am thinking along the line of optics since that is my physics background and the chromatic dispersion that one has when passing light through glass. If I am not mistaken each ply is at a different grain so in my model it would be like different index of glass and has the wave "sound"propagates through it would either speed up or slow down thus having a "dispersion" of acoustic frequencies.

To explore this I am thinking that one sends a 440Hz tone for 23 milliseconds and record the sonograph "Spectrograph" of the response it should only see the 440Hz tone if the time resolution can approach the tone burst of the 2.3 milliseconds.

One could do this for several frequencies to get a dispersion response

DMLBES does your foam panels have a similar tone quality?
Understood. One of the aspects about DMLs to bare in mind is that what you hear is a bending wave on the surface of the panel. Bending wave velocity is frequency dependent, high frequencies have a higher velocity than lower ones, so DML’s are naturally dispersive. I think what you are proposing is well worth a try but would not the velocity differential swamp any difference you might measure?

The other factors to consider are that these recording were not made to represent any quality factor, they were just a quick and dirty recording to answer DM’s request for the same tracks I had used on a framed and damped version a few days ago. The focus was actually on bass reproduction from tall panels, not overall quality. I have a way to go before I would say I was happy with these panels from a quality perspective. The discussion has veered from ‘how low can they go’ to tonality. That might be a little premature.

Burnt.
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