Actually ,zenker and others on This site have done a lot of work with dml.
There is a lot to read,I just noticed that in another paper he measured the dips in the response in the 100 to 200hz region in an anechoic chamber.
I have always wondered about this in conjunction with the room suck outs, I think this proves my theory of overlapping the response of the bass unit and the panel ?
If done correctly it should work.
Although I'm probably not going to agree with a lot of what he does to the dml panels regarding the panel sound,his tests are relevant.
It also looks like he has done some tests on the bass panel I posted ,but I have not found that yet ?
These articles are picking up on things I have thought about for years.
I wonder how many more things are going to pop out at me😀
Very interesting.
Steve
There is a lot to read,I just noticed that in another paper he measured the dips in the response in the 100 to 200hz region in an anechoic chamber.
I have always wondered about this in conjunction with the room suck outs, I think this proves my theory of overlapping the response of the bass unit and the panel ?
If done correctly it should work.
Although I'm probably not going to agree with a lot of what he does to the dml panels regarding the panel sound,his tests are relevant.
It also looks like he has done some tests on the bass panel I posted ,but I have not found that yet ?
These articles are picking up on things I have thought about for years.
I wonder how many more things are going to pop out at me😀
Very interesting.
Steve
Steve / Pway
This is all very interesting indeed. In fact, the paper uses the exact same exciter as I'm using (the Dayton Audio DAEX25FHE-4) - with a very similar trough towards the top end. If I'd been writing the paper, I'd probably have tried different exciters. As it stands, it may be hard to disaggregate exciter effects from panel effects. I have three different exciter brands on the way, so I will be in a position to see whether they have similar on-axis characteristics.
I must confess to not being able to visualise the BOF / BIF thing it talks about.
When I gat home from a weekend away, I'll try some on and off axis measurements. Actually, the off-axis output is relevant to me as my DMLs face straight forward and my listening position may be as much as 30 degrees off axis.
This is all very interesting indeed. In fact, the paper uses the exact same exciter as I'm using (the Dayton Audio DAEX25FHE-4) - with a very similar trough towards the top end. If I'd been writing the paper, I'd probably have tried different exciters. As it stands, it may be hard to disaggregate exciter effects from panel effects. I have three different exciter brands on the way, so I will be in a position to see whether they have similar on-axis characteristics.
I must confess to not being able to visualise the BOF / BIF thing it talks about.
When I gat home from a weekend away, I'll try some on and off axis measurements. Actually, the off-axis output is relevant to me as my DMLs face straight forward and my listening position may be as much as 30 degrees off axis.
I started reading part 2 first by mistake.
He states that the paneled woofer is a new concept ?
He obviously has not seen this patent.
US3164221A - Low frequency loudspeaker system
- Google Patents
I have not read all this as yet ,I think my head is going to explode.
I think he is only testing the fixed edge panel ?
In my mind ,this type of panel is very similar to the canvas panel except for the reduced HF performance.
I wouldn't worry too much about the BOF it is how much the magnet moves ,and how much the coil moves,basically.
(PDF) Low-Frequency Performance of a Woofer-Driven Flat-Panel Loudspeaker (Part 2: Numerical System Optimization and Large Signal Analysis)
My epoxy has arrived ,but I think I'm going to be reading a lot 😕
Steve.
He states that the paneled woofer is a new concept ?
He obviously has not seen this patent.
US3164221A - Low frequency loudspeaker system
- Google Patents
I have not read all this as yet ,I think my head is going to explode.
I think he is only testing the fixed edge panel ?
In my mind ,this type of panel is very similar to the canvas panel except for the reduced HF performance.
I wouldn't worry too much about the BOF it is how much the magnet moves ,and how much the coil moves,basically.
(PDF) Low-Frequency Performance of a Woofer-Driven Flat-Panel Loudspeaker (Part 2: Numerical System Optimization and Large Signal Analysis)
My epoxy has arrived ,but I think I'm going to be reading a lot 😕
Steve.
anyway, back to real dml panels.
the bird sounds on this recording can be quite painful if played too loud, but otherwise a clean sound.
as i have said before , because the exciters dont have to work so hard on eps ,i believe the coil resonance and other problems are reduced, but obviously not if pushed very hard .
ive noticed the harshness on vocals sometimes .
steve.
the bird sounds on this recording can be quite painful if played too loud, but otherwise a clean sound.
as i have said before , because the exciters dont have to work so hard on eps ,i believe the coil resonance and other problems are reduced, but obviously not if pushed very hard .
ive noticed the harshness on vocals sometimes .
steve.
Ammos
edge driven? two glass plates. etc..
I didn't see any live video, just the computer generated ads.
Looks to me like it's designed for ikea.
Ammos - Crystal Clear Audio on Vimeo
edge driven? two glass plates. etc..
I didn't see any live video, just the computer generated ads.
Looks to me like it's designed for ikea.
Ammos - Crystal Clear Audio on Vimeo
I had always assumed that this peak was due to the cavity resonance formed by the empty volume inside the exciter plus the vent formed by the gap between voice coil former and outer shell. In fact I'm not sure he's eliminated this possibility, because the smaller volume of a smaller exciter would result in a higher frequency cavity resonance, and so would the stiffening element he added, which also decreases the volume. Perhaps the voice coil buckling is merely a side effect of a helmholtz resonance?
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Thought I would also share a method for attaching and removing exciters onto foam prototypes, so you can use them many times. I've used the technique with the Dayton 'thruster' exciter 5 times so far and it works well, and does not seem to damage the polymer voice coil former. (Other types may have different plastics which are incompatible with acetone so test first before using the method.)
First mark a circle where the exciter will sit on the panel. Mix some 2-part epoxy glue and spread inside the circle to create a continuous smooth surface. This provides a good base, and prevents damage to the foam from the solvent-based glue used next.
After the epoxy cures, mount the exciter with VHB tape for a new exciter, or gorilla glue for second and subsequent uses. (Standard cyanoacrylate glue would probably also work, but I don't know how difficult it would be to get off in the final step. Gorilla glue is flexible so can be peeled away.) Weigh down the exciter with a small weight as glue cures, to squeeze out the majority of glue from the interface and create an intimate connection.
To remove the exciter when you've finished studying a prototype, cut out the exciter by taking out a circle of foam with a knife, saw or hot knife, leaving the exciter with a circle of foam attached.
Now put a few millilitres of acetone into an old metal or ceramic dish. Lower in the exciter, foam side first and the foam will quickly dissolve away. You will be left with just the glue attached to the exciter, which can now be easily peeled away.
First mark a circle where the exciter will sit on the panel. Mix some 2-part epoxy glue and spread inside the circle to create a continuous smooth surface. This provides a good base, and prevents damage to the foam from the solvent-based glue used next.
After the epoxy cures, mount the exciter with VHB tape for a new exciter, or gorilla glue for second and subsequent uses. (Standard cyanoacrylate glue would probably also work, but I don't know how difficult it would be to get off in the final step. Gorilla glue is flexible so can be peeled away.) Weigh down the exciter with a small weight as glue cures, to squeeze out the majority of glue from the interface and create an intimate connection.
To remove the exciter when you've finished studying a prototype, cut out the exciter by taking out a circle of foam with a knife, saw or hot knife, leaving the exciter with a circle of foam attached.
Now put a few millilitres of acetone into an old metal or ceramic dish. Lower in the exciter, foam side first and the foam will quickly dissolve away. You will be left with just the glue attached to the exciter, which can now be easily peeled away.
Pway.
I still haven't read this yet ,but just had a quick look through at the measurements.
Fig 4 shows no sign of ringing on the free coil,but peaks on the magnet ,this could be voice coil breakup,but it could also be a number of other problems as you say ?
The obvious one to me is that The coil is attached to a board ,which is now part of the measurement .
Usually when I reduce the peak at around the 10k region(depending on panel material) the frequency response above this usually increases,which point to cancellation problems within the coil surface area ,I believe ?
The air cavity problem is a separate issue, but is ignored as well.
Exciter wobble could also be an issue?
But the measurements are interesting even if the conclusion is not.
Steve.
I still haven't read this yet ,but just had a quick look through at the measurements.
Fig 4 shows no sign of ringing on the free coil,but peaks on the magnet ,this could be voice coil breakup,but it could also be a number of other problems as you say ?
The obvious one to me is that The coil is attached to a board ,which is now part of the measurement .
Usually when I reduce the peak at around the 10k region(depending on panel material) the frequency response above this usually increases,which point to cancellation problems within the coil surface area ,I believe ?
The air cavity problem is a separate issue, but is ignored as well.
Exciter wobble could also be an issue?
But the measurements are interesting even if the conclusion is not.
Steve.
the solitudes recording i just posted was recorded a lot closer to the panels than i usually record as i was trying to get away from the junk piled up each side of the room 🙄
hopefully it still sounded ok.
a few trips down to the tip is in order
i do hate getting rid of old audio gear,ooops ,i just realized i just said yes to having my friends old mullard valve amps,how am i going to sneak those through the door without the other half noticing ?
the idea was to have an audio room to myself with just my audio and some antique gear on display in a cabinet ,not a dml work room come broom cupboard junk room 😕
now where did i put that epoxy resin 😀
steve.
hopefully it still sounded ok.
a few trips down to the tip is in order
i do hate getting rid of old audio gear,ooops ,i just realized i just said yes to having my friends old mullard valve amps,how am i going to sneak those through the door without the other half noticing ?
the idea was to have an audio room to myself with just my audio and some antique gear on display in a cabinet ,not a dml work room come broom cupboard junk room 😕
now where did i put that epoxy resin 😀
steve.
Along the lines of the stretched canvas builds: has anyone tried attaching an exciter to heat shrink plastic over a frame?
Top Flite MonoKote Neon Orange 6''' | Tower Hobbies
Top Flite MonoKote Neon Orange 6''' | Tower Hobbies
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In his base case, which he refers to as the "raw panel", the perimeter of the panel is glued directly to a 40 mm wide frame. In the BOF (Bitumen On Frame) case, instead of gluing the panel directly to the frame, he glues the bitumen damping layer (40 mm wide) to the face of the frame, and then glues the panel to the surface of the bitumen. In the BIF case (Bitumen In Frame), he glues the panel directly to the frame (as in the raw panel case), and he applies the bitumen layer (again 40 mm wide) to the surface of the panel, just inside the inner perimeter of the frame. So in this case, the bitumen touches only the panel, but not the frame.
He found that both damped cases (BOF and BIF) improved the "Directivity Index" without significantly compromising sensitivity. The BIF version seemed to be slightly better, he thought.
Another advantage of the damped (BOF/BIF) cases over the free (i.e. hanging from strings) or simple clamped case is improved spectral decay, which he shows in a different paper:
(PDF) Optimized Radiation Pattern and Time Response of Flat Panel Loudspeakers due to the Specific Damping of the Boundary Conditions
Eric
Not surprising BIF is better because you have damping both
my setup needs lots of work, nothing behind the panels, small room, no rug. On my setup, overall sound is bright with "sssss..." with many female vocals, but I am surprised at your extended bass response...
Attachments
Just to add, on my ebay exciters I used hot glue, seems to work OK, and since hot glue can usually be peeled off hard surface I am betting that I can detach the glue peel when I want to move to another panel...
Many thanks Eric. Now I understand. I'm wondering if a BIF/BOF combo might be even better. (Sounds rather like boxing...)
gychang, good idea re. hot glue. I may try it on my ply panels. When my new exciters finally arrive I'll be doing a ply vs eps shootout with otherwise identical setups.
gychang, good idea re. hot glue. I may try it on my ply panels. When my new exciters finally arrive I'll be doing a ply vs eps shootout with otherwise identical setups.
I like those papers by Zenker et al, because they are a good blend of theory grounded in experiment. Much more valuable than patents I think because there you find a lot of open conjecture and ambit claims, alongside well-established fact.
Another issue with many papers is the lack of actual physical data. I've read quite a few papers on bending wave theory, mainly from the field of vibration in mech eng. Most of them seem to present some hypothesis, and then validate it with finite element analysis. IOW to them finite element IS the real world! Cant help thinking many of these are like self-fulfilling prophesy, or GIGO.
Another issue with many papers is the lack of actual physical data. I've read quite a few papers on bending wave theory, mainly from the field of vibration in mech eng. Most of them seem to present some hypothesis, and then validate it with finite element analysis. IOW to them finite element IS the real world! Cant help thinking many of these are like self-fulfilling prophesy, or GIGO.
Has anyone used PVC foam? It's harder and thinner (down to 3mm) than EPS/XPS, so should support high freq better. Still quite low density. Its used by the printing industry for signage and is available in large sizes. You could presumably make a big speaker with photo printed on the front. https://www.palram.com/au/wp-content/uploads/sites/3/2020/03/PALFOAM_En_Leaflet_61152_1.pdf
Add Some Surface Texture..
Speaking of PvC..
~3mm thick..
https://www.amazon.com/Dundee-Deco-...refix=pvc+shower+wall+panels,tools,227&sr=1-6
Speaking of PvC..
~3mm thick..
https://www.amazon.com/Dundee-Deco-...refix=pvc+shower+wall+panels,tools,227&sr=1-6
It looks like a contender: same thickness as the poplar plywood I'm using and about a third of the density. Available in sizes up to A0 on Amazon UK. 5 sheets of A3 3mm £12.45 delivered. The paper coating on each side suggests the usual PVA treatment may be needed.
Just when you think you knew what you were going to do next...