Sorry to be pedantic, but the operative word was "issues" 😉 They are earlier in time so not such a problem perceptually.
I think not because the release is not providing any momentum to the spring, the spring moves under its own acceleration due to its contracting force, and the resulting spectral content is entirely generated by the spring's own properties, whereas an impulse like a knuckle wrap is injecting momentum into the panel or spring with its own spectral content.
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So the spring can be displaced by any movement irrelative of it's spectral content but upon release resonates at it's own frequency, like a guitar string. What I was trying to convey was that the result of the release may as well have been an impulse.
Perhaps it's better that the bell analogy since the cabinet isn't struck in the same way with a wide band impulse from a stationary position with an abrupt "discontinuity".
Perhaps it's better that the bell analogy since the cabinet isn't struck in the same way with a wide band impulse from a stationary position with an abrupt "discontinuity".
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Rev 2...
This one uses the much softer and more difficult to work with foam "rubber" yoga mat material. Instead of connecting the speaker to the enclosure rear wall through the post and a piece of cushioning piece of material, I now connect it to a 2nd suspension.
So the driver is floating pretty freely on a trampoline made of this stuff. It only has its own mass plus that of the wood post to push against. I've yet to design a way to measure the resonant frequency of the suspended driver structure. Obviously, this design allows more sprung mass to be "bolted on" at the rear of the cabinet. I'm guessing by feel it's going to be pretty low. Wish I still had "work access" to a shaker table -
Unfortunately, with this particular material I believe sagging will be a problem. The "tail" suspension holds the driver square to the front baffle - otherwise it would just twist around and point upward.
Even with this in place, pressing my ear against the cabinet sidewall I still hear all kinds of nasty structural resonances within the cabinet material - unstuffed - when playing music. I'll stuff back in the original material and see if that tames this down any, as I imagine the sound is really bouncing around in there without it.
Not feeling a lot of vibration on that wingnut when playing. I know. I'm the wingnut.
This one uses the much softer and more difficult to work with foam "rubber" yoga mat material. Instead of connecting the speaker to the enclosure rear wall through the post and a piece of cushioning piece of material, I now connect it to a 2nd suspension.
So the driver is floating pretty freely on a trampoline made of this stuff. It only has its own mass plus that of the wood post to push against. I've yet to design a way to measure the resonant frequency of the suspended driver structure. Obviously, this design allows more sprung mass to be "bolted on" at the rear of the cabinet. I'm guessing by feel it's going to be pretty low. Wish I still had "work access" to a shaker table -
Unfortunately, with this particular material I believe sagging will be a problem. The "tail" suspension holds the driver square to the front baffle - otherwise it would just twist around and point upward.
Even with this in place, pressing my ear against the cabinet sidewall I still hear all kinds of nasty structural resonances within the cabinet material - unstuffed - when playing music. I'll stuff back in the original material and see if that tames this down any, as I imagine the sound is really bouncing around in there without it.
Not feeling a lot of vibration on that wingnut when playing. I know. I'm the wingnut.
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There will always be some energy transfer.
Even with the most dampening material, like sand, transfers sound (which anyone who has had one ear pressed against the sand on a busy beach will know).
The trick is of course to make it as small as possible, and do a high or low pass (via material and suspension type) to minimize the transfer to air and reflection back into the cone.
Even with the most dampening material, like sand, transfers sound (which anyone who has had one ear pressed against the sand on a busy beach will know).
The trick is of course to make it as small as possible, and do a high or low pass (via material and suspension type) to minimize the transfer to air and reflection back into the cone.
Interesting thread. To really see if there is an effect, can you make some measurements with and without the vibration isolation methods employed? Look at the harmonic distortion vs frequency at higher SPLs. If that goes down, then you have done something significant. The cushioning shouldn’t be too soft though as the pressure recoil may actually cause vibration (rattling) and more noise/distortion.
>To really see if there is an effect, can you make some measurements with and without the vibration isolation methods employed?
OK, I tore out the stiffer suspension material from the other cabinet and readied it for comparison testing. I used 3/4 scrap ply and left the post attached to the driver magnet assy - it doesnt touch the back of the cabinet in this case, being ~3/4" off the surface.
After the adhesive cures, I'll first try the pink noise out of phase cancelling test for a side panel to side panel radiation comparison using a measurement mic with REW;s nth octave band analysis. I can do swept sine also.
OK, I tore out the stiffer suspension material from the other cabinet and readied it for comparison testing. I used 3/4 scrap ply and left the post attached to the driver magnet assy - it doesnt touch the back of the cabinet in this case, being ~3/4" off the surface.
After the adhesive cures, I'll first try the pink noise out of phase cancelling test for a side panel to side panel radiation comparison using a measurement mic with REW;s nth octave band analysis. I can do swept sine also.
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An important factor is mechanical impedance matching. To maximise energy transfer similar impedances must be used, and by corollary to minimise transfer differing impedances used.
The sand comparison is so because the energy travels through material which is identical, ie. sand. Sea waves pass energy relatively easily for the same reason - water to water, with only viscous and frictional energy loss.
So to avoid transfer a mismatch is beneficial, but this also may result in reflected energy. (Sea waves htiing sea wall and 'bouncing' back.)
Soft coupling
I tried an experiment with my TABAQ's last night. Installed O-rings under and over each mounting screw, tightening each so the driver is not down tight to the cabinet. The box sound was greatly reduced and overall a big improvement in sound quality. well worth the effort.
Larry
I tried an experiment with my TABAQ's last night. Installed O-rings under and over each mounting screw, tightening each so the driver is not down tight to the cabinet. The box sound was greatly reduced and overall a big improvement in sound quality. well worth the effort.
Larry
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>well worth the effort
I wish I could say the same. Apparently the boxes I have (Cheap MDF with no frame cleats nor bracing) seems to respond more to the acoustic internal sound pressure constrained by the enclosure, than it does to mechanical coupling from the driver.
I setup the out of phase pink noise test and wiggled until I got the null pretty good. Straight away I could hear not much difference between the sound coming off the side panels. I put my measurement mic about 3/8" off the panel surface, centered.
The graph does show some differences in character - but nothing "wow!" to write home about. The SPL isnt calibrated, but since I just slid the mic stand over to the adjacent speaker panel and kept the same mic distance, should be OK to compare.
So. Methinks if you have a cheap, resonant enclosure, mechanically vibration-isolating the driver wont buy you much. It's the SPL within rattling the box panels. Perhaps adding bracing would be a more effective use of ones effort, to make such an enclosure more than just a little bit, if at all, better.
The slight differences in the spectrums could easily be due to the slight structural changes to the box, in order to accommodate the foam suspension. ~1/3 of the side panel is no longer edge attached to a solid front baffle board in the foam-sprung driver I implemented.
I wish I could say the same. Apparently the boxes I have (Cheap MDF with no frame cleats nor bracing) seems to respond more to the acoustic internal sound pressure constrained by the enclosure, than it does to mechanical coupling from the driver.
I setup the out of phase pink noise test and wiggled until I got the null pretty good. Straight away I could hear not much difference between the sound coming off the side panels. I put my measurement mic about 3/8" off the panel surface, centered.
The graph does show some differences in character - but nothing "wow!" to write home about. The SPL isnt calibrated, but since I just slid the mic stand over to the adjacent speaker panel and kept the same mic distance, should be OK to compare.
So. Methinks if you have a cheap, resonant enclosure, mechanically vibration-isolating the driver wont buy you much. It's the SPL within rattling the box panels. Perhaps adding bracing would be a more effective use of ones effort, to make such an enclosure more than just a little bit, if at all, better.
The slight differences in the spectrums could easily be due to the slight structural changes to the box, in order to accommodate the foam suspension. ~1/3 of the side panel is no longer edge attached to a solid front baffle board in the foam-sprung driver I implemented.
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With the driver raised a bit due to the o-rings, were you able to maintain an airtight seal between the driver and the box cutout?
A small pinhole air leak on a TL can ruin the deepest bass response. This is a well known effect with anyone who has played a flute or recorder or other woodwind instrument. A small leak from you fingerpad on the lowest hole (C on a flute) prevents the lowest note from achieving “lock” and sounds weak and fluttery.
Costal waves are pretty different in nature, since they are rotating/torsional, partially converted by the coast wedge.
But notice how the cost absorbs the waves pretty well because it’s a wedge and mostly of sand.
Look at the Manger driver with its starshaped edge pattern, or a sound dead room with its foam wedges.
We should probably aim at the same gradual absorption to avoid too much impedance related reflection.
This can be done with shape, materials or both.
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Nice effort!
Here’s some thoughts you might consider. The rod connecting the driver magnet might be too rigidly connected and might form a secondary slave driver to the foam on the back.
The rod might also in itself form a radiator that might send highs through the port.
You might also consider a mechanically connected microphone instead, instead of air transfer. That would take a lot of unknowns out.
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@X I used a light foam gasket between the o-rings to maintain a seal, bass was still good!
Larry
Larry
Yes they differ, but have the properties I described to an extent.
When I was thinking of reflection I had in mind, but did not state, the waves hitting a coastal wall, where there is a massive reflection.
Gradual absorption? Well I think the material should be transmission like with high losses.
I found this, see "Contact Vibration Reduction"
Speaker Design: Driver-Induced Vibrations | audioXpress
There are some interesting definitions that answer some questions raised here.
I recommend reading the full article .....🙂
" After this look at how to combat vibration, it's now time to see what you can do to reduce the energy conduction itself. From Newton’s third law of motion, you know that most of the mechanical energy generated by the driver is transferred to the panel through the frame; Therefore, if you decouple it, you reduce the energy that reaches the panel and, consequently, its resonance amplitude. Another positive effect of chassis decoupling is a reduction of driver interaction, because the same energy that reaches the panel goes to the other drivers, too ."
" My personal recipe for a hypothetical three-way loudspeaker is to use a box for the woofer only, made of plywood with many braces so that the panel resonance is ..........."
Speaker Design: Driver-Induced Vibrations | audioXpress
There are some interesting definitions that answer some questions raised here.
I recommend reading the full article .....🙂
" After this look at how to combat vibration, it's now time to see what you can do to reduce the energy conduction itself. From Newton’s third law of motion, you know that most of the mechanical energy generated by the driver is transferred to the panel through the frame; Therefore, if you decouple it, you reduce the energy that reaches the panel and, consequently, its resonance amplitude. Another positive effect of chassis decoupling is a reduction of driver interaction, because the same energy that reaches the panel goes to the other drivers, too ."
" My personal recipe for a hypothetical three-way loudspeaker is to use a box for the woofer only, made of plywood with many braces so that the panel resonance is ..........."
Squeak; thanks. It was a fun test to setup, even if I didnt like the results.
academia50; Apparently in my case most of the mechanical energy generated by the driver ends up in the sound pressure it makes, while the reaction to the force it takes to do so is minimal due to the mass of the driver.
If I decouple that mass further from the cabinet, it's apparent that not much racket is added into the cabinet structure, compared to what the sound pressure inside the box does to it.
I really thought it was going to make a huge difference. Perhaps if the driver frame and magnet assembly had no mass at all...
academia50; Apparently in my case most of the mechanical energy generated by the driver ends up in the sound pressure it makes, while the reaction to the force it takes to do so is minimal due to the mass of the driver.
If I decouple that mass further from the cabinet, it's apparent that not much racket is added into the cabinet structure, compared to what the sound pressure inside the box does to it.
I really thought it was going to make a huge difference. Perhaps if the driver frame and magnet assembly had no mass at all...
Why? You need a half decent cabinet to start with. Blu tack might be worth experimenting with.
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