Accelerometer Testing of Loudspeaker Drivers

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To support the previous post, here are two measurements that I took by putting the accellerometer at the same point of the top panel of a test loudspeaker box.
One is without any damping and the second is with some damping on this panel.

With such an equipment, it is very easy to compare different damping technics and decide what is the best.
 

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  • Accelerometer measurements for the effectiveness of the dampening.JPG
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I have available new versions of the PCB and the Front panel for the accelerometer amplifier as shown in the photo. The functionality of the device remains the same. A more compact box can be used now to house the amplifier.
The cost is 60 Euros for both. The shipping cost is 15 Euros.
If you are interested, send me an email: gntanavaras@gmail.com
 

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  • PCB and Front Panel for Accelerometer amp.jpg
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Hello George,

I received last Friday your box. It looks great, really nicely done. I tested it with my FFT spectrum analyzer and it works perfectly. Very precise measurements. I have to admit, I did a small mod, added a BNC connector. All my test cables are ether with BNC or bananas and it was easier just to add BNC to the box.


Thank you for the great product.

AR2
 
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Measurements of the vibrations of a turntable

A very interesting application of the accelerometer, in cooperation with an audio measurement and analysis PC software like ARTA, is the investigation of the vibration behavior of the parts of a turntable.

The first photo shows a very simple setup I made for this investigation.
An 8” woofer was used to vibrate the shelf on which the turntable was positioned.
The ACH accelerometer was shielded with an aluminum foil to suppress any external EMI interference of 50 Hz mains voltage, because the level of the output signal of the preamplifier was very low level.

The second photo shows five measurements.
The first measurement was taken with the accelerometer in position P1, very close to the 8" woofer. As we can see the excitation of the shelf is almost uniform between 100 to 900 Hz.
The second measurement was taken with the accelerometer in position P2, on the basis of the turntable.
The third measurement was taken with the accelerometer in position P3, on the platter of the turntable, where an LP was also placed.
The fourth measurement was taken with the accelerometer in position P4 on the top of the Rega RB300 arm of the turntable.
The bottom measurement shows the noise floor of the setup (with the woofer muted).

With such a tool and with the above measurements, it is very easy to find solutions that will improve the behavior of every turntable in vibrations.

If you want to built this tool, you will find some usefull information here:
http://www.diyaudio.com/forums/swap...front-panel-accelerometer-preamplifier-2.html
 

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  • Turntable setup.JPG
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  • Turntable vibrations measurements.PNG
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I have used the ACH accelerometer with its pre-amplifier to measure the distortion of a woofer and its peak displacement in relation to the input voltage.
I used the STEPS part of the ARTA software (STEPS Main Menu --> Record ---> Distortion vs. amplitude) with the output of my accelerometer amplifier (set to "Exc" to measure displacement) connected as an input to the software.
The accelerometer is attached to the center of the woofer's cone and the microphone very close to the cone.
In the attached photo you can see such a measurement of a 12" subwoofer placed in a box of about 30 litters.
 

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  • Cone Displacement measurements at 20 Hz.jpg
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Yes, there is, at least for the woofers larger than 8".
The ACH-01 accelerometer has a weight of 3 grams and could be used without serious effects on drivers that have a cone mass weight greater than 25 -30 grams.
I have used it also in smaller woofers with acceptable results.