It might be that thanks of the way the sound is radiated from the panel (omni directional), the quality of the sound stage (the sound doesn't seem to come from the panel) we can tolerate more uneven FR than with standard speakers.
It is a big difficulty in communication around the DML; The FR are not nicely flat but the sound is really pleasant.
+ @spedge
A panel reaching nearly clamped condition is louder than any other suspension modes.
Christian
What do you base that on?
In that case, why does Tectonic use compliant suspension?
Thank you Steve
Hi Q recorder is no more free.
I had a short test with recforge 2 but I stopped seeing the parameter the choice of the top mic OR the bottom one but no mention of both or stereo record (not stereo output file with twice the same track).
I don't know if there is a possibility of a real stereo recording with a phone.
Here is a record made with a hand recorder H1n with 2 external omni electrets from my armchair (about 2.3m from the panels?). It is not for sure a nice record from a good sound track. Just the TV playing at "normal" volume. First the mics are close of each other. At about 8s separated by something like 25cm, coming back together just before 20s (small spike when they shock) and then separated again at 27s. Need further investigation to say what gives a relevant record. Even if the sensitivity of the mics is not too bad, it is low for this application without increasing the volume. The internal mics of the hand recorder are even less sensitive.
Christian
From different papers about the acoustic of plate dealing with their boundary conditions. I am not sure to be able to find the exact source... Too many readings by the time being.
In the Tectonic design, I don't know under which condition they are (see the role of the 4 rubber fixations in addition) really. If the level is an advantage of the clamped edge, the first resonance frequency is also the highest of all the classical conditions. there are probably other reasons... I am not experienced enough about the suspension. some investigation on going.
Hello,
I would like to come back on 2 topics under discussion those days... double exciters and role of suspension.
On post #5095 I shown 2 FR, one with one exciter, the second with 2 exciters with no big differences; encouraged by the exchanges here, different readings, I decided to make some additional tests to understand if it has to be a design rule (as suggested in the Tectonic patent to get a balance panel) for the future... and today something went different compare to the previous tests. With 2 exciters, there is a lack of HF. I tested different positions of the second exciter, no big change... what's wrong I don't know! What is true, I don't know...
The second test was to see what happened changing the way the panel is attached (string, corner hand held, on the side hand held). So it changes clearly the bass. When the panel is hand held at the bottom corner, the 1st resonance seems disappearing. @Leob, not exactly what you have but more close than before...
2 exciters test : blue one exciter at 2/5, purple 2 exciters post 5095 (previous test), green 2 exciters at 2/5 (symetric) today, bronw 2 exciters today.
blue : 2 strings attached on the upper short side (Spedge's method ;-) ), red : hand held at the 2 lower corners, pink : hand held at 0.22 of the length of the long side from the upper corners (similar position than Tectonic rubber fixation but only 2 points)
I would like to come back on 2 topics under discussion those days... double exciters and role of suspension.
On post #5095 I shown 2 FR, one with one exciter, the second with 2 exciters with no big differences; encouraged by the exchanges here, different readings, I decided to make some additional tests to understand if it has to be a design rule (as suggested in the Tectonic patent to get a balance panel) for the future... and today something went different compare to the previous tests. With 2 exciters, there is a lack of HF. I tested different positions of the second exciter, no big change... what's wrong I don't know! What is true, I don't know...
The second test was to see what happened changing the way the panel is attached (string, corner hand held, on the side hand held). So it changes clearly the bass. When the panel is hand held at the bottom corner, the 1st resonance seems disappearing. @Leob, not exactly what you have but more close than before...
2 exciters test : blue one exciter at 2/5, purple 2 exciters post 5095 (previous test), green 2 exciters at 2/5 (symetric) today, bronw 2 exciters today.
blue : 2 strings attached on the upper short side (Spedge's method ;-) ), red : hand held at the 2 lower corners, pink : hand held at 0.22 of the length of the long side from the upper corners (similar position than Tectonic rubber fixation but only 2 points)
It makes sense in that you basically have a trampoline which returns a lot of energy on each excursion. The trade off is big variations in FR as the panel tries to get back to fundamental frequency.
I don't, but I know some of the composites sites provide tools to do it.
Christian.
basically when you are holding the sides with your fingers you are changing the standing waves on the panel.
I use this method to find places to apply weights.
I usually slide my fingers down the panel while watching in real time the output of the panel with pink noise.
with this method you can fill in some of the dips in response in the 100hz to 400hz region.
Steve.
basically when you are holding the sides with your fingers you are changing the standing waves on the panel.
I use this method to find places to apply weights.
I usually slide my fingers down the panel while watching in real time the output of the panel with pink noise.
with this method you can fill in some of the dips in response in the 100hz to 400hz region.
Steve.
Hey
But my point was that those issues (if they are real), would be irrelevant to it's performance in a DML sub that's limited to uncer 100 Hz.
Eric
Sorry, I messed up again. I meant XPS not EPS. Don't know why I can't keep that straight! The panels even have "XPS" printed right on them!
But my point was that those issues (if they are real), would be irrelevant to it's performance in a DML sub that's limited to uncer 100 Hz.
Eric
Leob.
I was going to try to explain the idea of rigidly mounting of a 3mm ply panel, but thought the last page of this forum I posted in 2015 explains most of it anyway.
https://www.audiocircle.com
Steve.
I was going to try to explain the idea of rigidly mounting of a 3mm ply panel, but thought the last page of this forum I posted in 2015 explains most of it anyway.
https://www.audiocircle.com
Steve.
Christian,
Nope. Just about right. Per my spreadsheet, they should have a B (or D if you prefer) of about 10 Pa m3, which is probably close to 3 mm plywood. BUT with a B/mu^3 of around 100, so rivaling PS foams in that regard. In theory, at least. This construction has literally been on my list of things to try (#5 actually), since I developed my spreadsheet. But I was afraid the fiberglass (or carbon) would suck into the cavities of the nomex honeycomb, unless I used a prepreg. But apparently it can be done just fine with plain old fiberglass and epoxy. The process he followed is actually simpler than my process for carbon/balsa panels.
Eric
What I'm planning for my XPS subwoofer is to make a wooden frame (using say 1x4 nominal poplar or pine) with inner dimensions just a little larger than the panel, and with an inner frame screwed into the main frame that is offest about an inch below the face of the main frame. Then the panel would be attached to the inner frame with double sided foam tape, so that the face of the panel would be inset about 1/2" behind the face of the main frame, providing some protection, at least for the edges of the panel. The frame makes the panels even bigger, I know. But apparently that's not an issue at your house!
Eric
You are vacuum bagging? It can be done even without vacuum bagging by doing one side at a time and letting it fully cure. You wet one layer on your release surface then lay the honeycomb on it and then weights and let it cure (I've seen a layer of closed cell and a piece of plywood laid carefully on the honeycomb to give even pressure). As long as you don't overwet the honeycomb won't wick up too much. Then when it's cured repeat for the over side. I think that same guy did this with aluminum honeycomb.
You are right that carbon beats glass when it comes to stiffness and weight. But the challenge for a DML panel is that to avoid being too stiff, the carbon needs to be very thin. I think the glass he used was just about the right thickness for a DML (about .08 mm maybe?). For carbon ideally you'd probably want someting even thinner, which is hard to find I think. Or expensive if you do. The closest reasonably priced thin carbon I can get is a 90 gsm spread tow that would finish out at about 0.12 mm.
I think glass just might actually work out better, in this case.
Usually yes. But I don't have too. I had thought of bagging the skins separately, then gluing to the nomex. But your method, or the one in the video, would probably work better, I think.
Eric
Eric.
I don't know how you stand ,when it comes to dml subs, but in the tectonic patent just posted ,in fig 9A it shows in the 200hz region the change over from dml mode to pistonic mode ,and by 100hz it is heavily pistonic.
My problem is , knowing how good cone bass drivers are , and the likes of the B139 , is it worth trying to build a sub dml panel (that isn't actually dml anyway ?) With all its problems ?
I have found that I need a very powerful low frequency driver system just to try and keep up with my panels which are in dml mode, which does not bode well for a dml sub ?
Large dml bass panels would be able to move more air but would take much longer to stop moving.
B.E.S used a fairly small (large) bass dml panel for their speakers, but I would not want to overdrive that unit, and of course the Yamaha ear unit , but these are all based on drive unit design, similar to bmr.
Do you have any thoughts on this ?
Steve.
I don't know how you stand ,when it comes to dml subs, but in the tectonic patent just posted ,in fig 9A it shows in the 200hz region the change over from dml mode to pistonic mode ,and by 100hz it is heavily pistonic.
My problem is , knowing how good cone bass drivers are , and the likes of the B139 , is it worth trying to build a sub dml panel (that isn't actually dml anyway ?) With all its problems ?
I have found that I need a very powerful low frequency driver system just to try and keep up with my panels which are in dml mode, which does not bode well for a dml sub ?
Large dml bass panels would be able to move more air but would take much longer to stop moving.
B.E.S used a fairly small (large) bass dml panel for their speakers, but I would not want to overdrive that unit, and of course the Yamaha ear unit , but these are all based on drive unit design, similar to bmr.
Do you have any thoughts on this ?
Steve.
NaRenaud,
See here for my carbon/balsa method. I've done fiberglass/balsa too.
https://www.diyaudio.com/community/...s-as-a-full-range-speaker.272576/post-6924919
Eric