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Accelerometers to measure panel vibrations?
Accelerometers to measure panel vibrations?
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Old 14th December 2020, 08:04 PM   #21
Mr BA is online now Mr BA  England
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Default ACH-01

Several years ago, I played with an ACH-01, which you used to be able to buy a battery powered amplifier to go with it. You can find amp ref in bwaslo link in post #19. I used REW in an attempt to produce similar waterfall plots as shown in Stereophile. I used "Tacky Wax" to fasten it to the cabinet.
As several others have advised, it is not easy to calibrate and it does n't really tell much about what is going on.
Dependent upon how your rigid your cabinets are to start with it may be worth using the frequency generator in REW or similar, then using your hand or stethoscope to feel the vibrations.
For those wishing to DIY the amp, here is the detail.
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Old 14th December 2020, 08:59 PM   #22
cracked case is offline cracked case  England
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Quote:
Originally Posted by puppet View Post
I've used half a glass of water or coffee. ... wouldn't connect that to a Mac or iPhone though.
I have a water bowl beside a beach grinder at work, despite the bowl being round, the ripples form lots of small ( 3/16" ) squares, I find this quite amusing.
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Old 14th December 2020, 09:40 PM   #23
bwaslo is offline bwaslo  United States
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Accelerometers to measure panel vibrations?
Quote:
Originally Posted by Mr BA View Post
...
For those wishing to DIY the amp, here is the detail.
It can actually be much simpler than that, just a 2.2k between the battery +9V and the "drain" connection. Connect the "source connection" to the "ground" connection. A 3.3uF cap from the "drain" to the soundcard hot input, and battery [-] connection to ground, and soundcard cold/hot connection to ground. Two other parts only.
The opamp circuit is if you want all the dynamic range you can get, but that isn't likely needed unless you are trying to drive a pro audio mixer input.
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Old 14th December 2020, 09:45 PM   #24
mbrennwa is offline mbrennwa  Switzerland
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Accelerometers to measure panel vibrations?
Just in case you happen to have a measurement microphone, you could use this instead of an accelerometer to test box/panel vibrations. See here: Cabinet bracing: measurements?
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Old 14th December 2020, 10:28 PM   #25
acg is offline acg  Australia
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I have one..is good...

PCB and Front panel for Accelerometer preamplifier
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Old 14th December 2020, 10:46 PM   #26
bradleypnw is online now bradleypnw
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Quote:
Originally Posted by head_unit View Post
I plan to make some cabinets, and want to experiment with damping, bracing, coating.
If the context of your question is building personal DIY speakers this won't help you. Resonances show up in the frequency response graph. Build the speakers, if the frequency response is good you know you don't have resonance problems.
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Old 15th December 2020, 07:28 AM   #27
classicalfan is offline classicalfan  United States
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Originally Posted by head_unit View Post
Ya just stick that one with...what the heck DO you stick it on with? I've read Atkinson's measurements for years, and is it Vance Dickason? But I don't remember the details.

My idea is have a professional build the cabinet shells, and then I experiment with all the internals. Like how about a rigid brace, versus a brace under compression but with a gel pad at one end. Well, something more durable than gel but with some vibrational elasticity which I someone opined was more effective than total rigidity.
Probably pretty much a waste of your time. You might be able to move the resonant frequencies up higher, but you really can't get rid of them in a box speaker.

Siegfried Linkwitz covered this subject quite well at Burning Amp 2017.

Here is link to the video:

Burning Amp 2017 - Siegfried Linkwitz - YouTube

Make sure you watch the whole thing. It's almost an hour long and he talks about this towards the end.

Last edited by classicalfan; 15th December 2020 at 07:56 AM.
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Old 15th December 2020, 10:15 AM   #28
cracked case is offline cracked case  England
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I both agree, and ( respectfully ) disagree, yes adding braces with shift the frequency higher rather than diminishing the vibration ( unless it's shifted above the crossover point of the mid/bass, in which case it's possible that a worth while improvement could be effected ), however I do believe ( and possibly Remlab would agree ) that box resonances can be significantly reduced, however you do have to make significant changes to box construction to do this, Eclipse TD, BBC ls3/5a, Remlab sandwich baffle or box in a box. I applaud head_unit's intention of implementing a methodical series of experiments, and hope to see the results.
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Old 15th December 2020, 10:23 AM   #29
scottjoplin is offline scottjoplin  Wales
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Originally Posted by cracked case View Post
I applaud head_unit's intention of implementing a methodical series of experiments, and hope to see the results.
Agreed. There is an awful lot of talk on the subject and a pitiful amount of data.
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Old 15th December 2020, 11:03 AM   #30
Joel Wesseling is offline Joel Wesseling  Canada
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