Planar magnetic dual membrane bass panel

[Few]

Great work, as usual, Joppe! While watching your videos I was struck by how taut your membranes are. As I’m sure you know, with electrostatics, tension is necessary so the diaphragms aren’t pulled into the stators even with no signal. That's not a concern for your magnetically driven panels, so I think you could safely try lower tension. That would lower the resonance frequency and probably reduce its Q as well. You may recall from the discussions in the parallel universe at diyaudio that my planar magnetic mid/tweeter panels incorporate a compliant surround. I have found that unless the tension gets ridiculously low, the low tension has not caused any trouble, and it keeps the fundamental resonance well out of the target range. Perhaps you’ve got other reasons to keep the tension high, but I thought I’d toss in the suggestion.

Again, great work, and fun-to-view videos!
Few

 

[Hayabusa]

thanks !, i know that but its not enough to damp the main resonance, . it gets split , and lowered a bit, but its still to high, unless you use a plate with tiny holes on the back of the magnets and speaker cloth the metal plates damps the most. because it has rather limited airflow.

Maybe an experiment with varying shaped of perforation? The Final electrostatics have some patterns and 'bands' in the perforation that maybe could help you?

 

[Joppe Peelen]

Great work, as usual, Joppe! While watching your videos I was struck by how taut your membranes are. As I’m sure you know, with electrostatics, tension is necessary so the diaphragms aren’t pulled into the stators even with no signal. That's not a concern for your magnetically driven panels, so I think you could safely try lower tension. That would lower the resonance frequency and probably reduce its Q as well. You may recall from the discussions in the parallel universe at diyaudio that my planar magnetic mid/tweeter panels incorporate a compliant surround. I have found that unless the tension gets ridiculously low, the low tension has not caused any trouble, and it keeps the fundamental resonance well out of the target range. Perhaps you’ve got other reasons to keep the tension high, but I thought I’d toss in the suggestion.

Again, great work, and fun-to-view videos!
Few

Hi Few , you also here ? well yeah lower tension i think also drives the foil less even maybe because when tensioned it acts slightly more as one thing.. for tweeter this usually is not a huge deal indeed. for low end it might, and with dual foils i have the feeling higher tension would even be better. but that indeed would make getting a low res rather hard i received some 28micron mylar today, maybe ill make 2 new foils, using the thicker mylar, and heavier alu traces from 30 micron to 50. so i have a bit more drive and more weight... should lower res a little as well. i still need to find a proper damping method.. so far everyhgin in between the foils over damps.. or just sounds weird and ugly, also distortion 80-200hz goes up when damped in between the foils.. weird but true. tested it a few times

 

[Joppe Peelen]

Maybe an experiment with varying shaped of perforation? The Final electrostatics have some patterns and 'bands' in the perforation that maybe could help you?

well i think they try damping by changing the perforations , less per where it needs to damp and vica versa. in my case i dont have anything on the front and back. hence why i tried some speaker cloth. and that works, but it might even be to transparant so maybe i need more crappy speaker cloth that damps more haha

 

[Few]

Yeah, I’m here as well. There goes the neighborhood, eh? It’s too bad it would be tricky with two diaphragms, because it would be interesting to try keeping your inner tube diaphragm tensioner as part of a panel so you could easily change just the tension and measure what happens. In any case, I’ll look forward to hearing of your results if you try the diaphragm thickness and all trace changes.
Few

 

[somebodyelse]

I'm just imagining the automated pump system to keep constant gauge pressure, unless tweaking it manually is part of the appeal.

 

[Few]

How about a stroboscope to view the diaphragm’s mode of motion? I just noticed Parts Express sells one with a flash rate range of 1 Hz to 666 Hz for ~60 USD. It would be fun to watch , if nothing else. Might even be informative!

 

[Joppe Peelen]

Of wat rijst