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Accelerometers to measure panel vibrations?
Accelerometers to measure panel vibrations?
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Old 15th December 2020, 10:59 AM   #31
Lojzek is offline Lojzek  Croatia
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There is an article in Audio Xpress, june 2011,"Accelerometer Testing of Loudspeaker Drivers" and within there is reference to cabinet panels.
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Old 15th December 2020, 01:15 PM   #32
EarlK is offline EarlK  Canada
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There are 2 Threads over at AVS that deal with this subject.

The VibSensor Accelerometer Test Thread

An RPI based diy vibration meter > now available for other Operating Systems.

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Old 15th December 2020, 05:33 PM   #33
classicalfan is offline classicalfan  United States
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Quote:
Originally Posted by scottjoplin View Post
Agreed. There is an awful lot of talk on the subject and a pitiful amount of data.
The question is not whether you can measure the resonances or not. They will be there and you can find them. The question is what can you really do about it. And particularly for the average DIYer.

SL with all of his time and talent finally concluded after a lot of testing that the answer to that question is - not much. Some may disagree, but I'm inclined to accept the conclusions of a man with his genius and time investment for understanding sound reproduction from speakers.

If you haven't watched the referenced video I highly recommend it. Not only for this subject, but for a lot of other material in the beginning that is very useful.

Last edited by classicalfan; 15th December 2020 at 05:56 PM.
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Old 15th December 2020, 06:14 PM   #34
scottjoplin is offline scottjoplin  Wales
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Did he change his opinion about the audibility of diffraction?
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Old 15th December 2020, 06:19 PM   #35
classicalfan is offline classicalfan  United States
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I don't know how to answer that. What to you think his opinion has been in the past?
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Old 15th December 2020, 06:23 PM   #36
scottjoplin is offline scottjoplin  Wales
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I should have been more specific, I was about to edit my post, I'm talking of edge diffraction, he mentions at the end that he doesn't like stepped baffle because of the diffraction. Diffraction from baffle edges
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Old 15th December 2020, 06:29 PM   #37
tomchr is offline tomchr  Canada
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I recall Analog Devices releasing some accelerometer ICs many moons ago. Probably 15 years ago. One approach could be to start with one of the evaluation boards for these. At the time I was thinking to measure camera/lens vibration with them for the evaluation of various tripods.

Accelerometers are commonly stuck to surfaces using bees wax. The wax doesn't mar the surface and cleans up easily. Of course nothing prevents you from using epoxy or something similar, which could be handy for prototype builds where you want the accelerometer stuck in one place for a long time.

Tom
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Old 15th December 2020, 06:34 PM   #38
gdan is offline gdan  Greece
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Accelerometers to measure panel vibrations?
Here is a measurement with the ACH accelerometer placed on the panels of a subwoofer cabinet.
The side panels were very well braced and the back panel was not braced at all.
There is a difference of almost 20 dBs between them.

My opininon is that if you have the capability to make measurements, then there is a lot of things you could do to lower the vibration of a cabinet panel.
It will be a slow, step-by-step procedure but the final result will be much better.
And an accelerometer like ACH is a good start.
Attached Images
File Type: jpg Cabinet Vibration measurements.jpg (123.7 KB, 198 views)
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Old 15th December 2020, 06:54 PM   #39
classicalfan is offline classicalfan  United States
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Quote:
Originally Posted by scottjoplin View Post
I should have been more specific, I was about to edit my post, I'm talking of edge diffraction, he mentions at the end that he doesn't like stepped baffle because of the diffraction. Diffraction from baffle edges
I'll read the material you referenced when I have more time. It's rather lengthy and SL isn't always easy to understand. Sometimes it takes several readings. At least for me.

But I think the quick answer to this particular video is that there is an alternative - namely electronic time delay. So if you can avoid any possible diffraction issues due to physical geometry why not do so electronically. SL is big on digital processing in general.
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Old 15th December 2020, 07:01 PM   #40
Remlab is offline Remlab  United States
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Accelerometers to measure panel vibrations?
Box resonances start at the midbass driver and propagate through the cabinet. The most efficient and cost effective way to deal with this is a sorbothane gasket decoupling the midbass on the front of the baffle with rubber washers decoupling the screws on the back of the baffle(This part can only be done with a removable baffle though). As far as transient response concerns go, Laurence Dickie of Vivid has been doing this with virtually all his designs(From the woofers all the way up to the tweeters) since the B&W Nautilus with world class results. I took the concept further than that for a relatively huge cost($250 for each 7" x 12" removable baffle), but using the technique I just mentioned, you could get about 70% of the way there(Maybe more) for the cost of the sorbothane and some precision cutting with an exacto-knife. Once again, if Laurence Dickie uses this method, there is no debate. He's proven the efficacy of the technique beyond a reasonable doubt.
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Last edited by Remlab; 15th December 2020 at 07:16 PM.
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