A Study of DMLs as a Full Range Speaker

I've also been working on honeycombed cardboard... Honeycombed, not corrugated. So it's similar to Nidaplast, construction-wise.
This is a 10mm cardboard panel, 300mm x 400mm. No frame, no damping, no edge termination. Driven with an XT32-4.
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Here's the same panel after being mounted with PVA in a 400mm x 500mm canvas frame. The canvas is tightened (I think I over-tightened it too much, hence the bass being a little attenuated). I've used a 34g weight to iron out the ubiquitous 600hz peak.
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The next version will have slightly looser canvas, and careful damping to increase the bass dB slightly; and epoxy resin in front of the driver to increase the tops.
 
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Leob.
I was referring to this recording of two exciters situated next to each other.
As can be seen in the video, one exciter is having problems, while the other is rock solid.
These exciters in these positions are unable to work in tandem.
Are there any positions that will allow them to work together in harmony, which is essential for low end performance.
What are the exact positions of your exciters on your panels, so that I can test them on my eps panels.
I intended to start with the nxt positions first, are your positions similar?
Steve.
Will be out today, but will get back to you with the drawings.
 
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Looks like the hole has an opposite effect? So, something to do with the VC area? And damping the VC cavity with felt or foam did not help either?
Yes, the hole creates a notch instead of a peak. I'm sure it has something to do with the size of the VC area.
Damping this cavity had no effect, whereas the Dayton Megabass (DAEX 32QMB) which had a 7kHz peak on Twinwall, did benefit greatly from a thick felt plug inside the VC cavity.
 
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Yes, the hole creates a notch instead of a peak. I'm sure it has something to do with the size of the VC area.
I'm not at all surprised by this result...A significant amount of the hf response comes directly from this zone..I was a bit surprised by the subsequent rise in hf until I realised that you drilled a 25 dia hole when the voice coil is 32mm dia. So you have an overhanging edge effect going on in the voice coil zone
 
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Yes, the VC is 32mm dia indeed.
But the hole in the former is 25mm, the former lip overhangs inside and outside the coil dia
Ok...I thought after I made that comment that this may be the case. So the extended hf is arising from a zone outside the hole (obviously LOL).. Would be interesting to do a Chandni test at these frequencies...I would take another punt and suggest that maybe it's arising from the former ring area around the hole.

In retrospect, it would have been instructive to start with a small hole using a step drill, test, fill it with mastic, test, if no good, go to the next step size etc etc.

20/20 rear vision is a great asset 😁
 
@Andre Bellwood maybe during the test try holding onto the back of driver, or add a mass to the back of the driver (maybe doubling it's weight), to see if it has any significant effect on that peak.

My first thought when you cut the hole was that the back of the driver is out of phase with the panel and it now has a clear and direct path for that opposite wave to interfere.

Also, just a thought, but maybe that's not a peak at 9kHz, maybe it's a dip from 2kHz - 8kHz :p