Where can I buy one of those? I can find a lot of information, but all old. And I don't have time go get into some DIY construction project about it.
I plan to make some cabinets, and want to experiment with damping, bracing, coating. Therefore it would be really handy to have an accelerometer of some kind (I'd hope connectable to Mac or iPhone) to quantify improvements or lack thereof
I plan to make some cabinets, and want to experiment with damping, bracing, coating. Therefore it would be really handy to have an accelerometer of some kind (I'd hope connectable to Mac or iPhone) to quantify improvements or lack thereof
The absolute cheapest way would be "Guitar Pickup Piezo Contact Microphone" off ebay, for < $15, shipped.
It wont have the infrasonic response a real accel might have and you wont be able to calibrate it to compare measurements with someone else. But it should give you relative indications of the effectiveness of your damping applications, i.e. brace / no brace, coating / no coating, etc.
It wont have the infrasonic response a real accel might have and you wont be able to calibrate it to compare measurements with someone else. But it should give you relative indications of the effectiveness of your damping applications, i.e. brace / no brace, coating / no coating, etc.
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.
The accelerometer method is either tedious or quite inaccurate. Tedious: you will have to measure every other square inch (way of speech) of the panel involved and next calculate the integral to get a reliable impression of the actual sound production of the panel. Inaccurate: if you only measure on a few spots, you will not have a clue about the mechanical-acoustical transmission of the vibrating panel.
Furthermore, don't worry too much about panel vibrations, as a decent cabinet will do fine in domestic situations. With possibly one exception for the vibrations of loudspeaker units to the baffle.
Furthermore, don't worry too much about panel vibrations, as a decent cabinet will do fine in domestic situations. With possibly one exception for the vibrations of loudspeaker units to the baffle.
I bought an accelerometer for exactly this purpose, then realised it would tell me nothing about the Q of the resonances nor the real-time energy storage of the enclosure, both of which I consider rather important. I would tend towards a low mass, highly damped enclosure rather than an ultra-stiff (within reason - ie. not a hollowed-out 2 ton boulder) and possibly high Q option.
Sorry to stray off-topic a little, but I have been think along these lines; using a two-piece brace supporting opposite walls with a visco-elastic material joining them and operating in shear.
I believe Earl Geddes and KEF both use this approach. The latter has nice BEM modeling on this in a white paper about the LS50.
If you are interested for an assembled and calibrated Accelerometer system, have a look here:
https://www.diyaudio.com/forums/swa...accelerometer-preamplifier-4.html#post5617620
https://www.diyaudio.com/forums/swa...accelerometer-preamplifier-4.html#post5617620
I have the contact mics and they work OK. As the frequency response is unknown, they are mostly used for comparison. The bass response is weak, which doesn't help. They come with adhesive on them, but it's meant to be semi-permanent. I removed that and used some very thin tape made for mounting photos. It isn't blameless, but the best I've found.
A few years back I talked with SY about using accelerometers for this sort of thing. He gave me some pointers, which I never put into practice. He also suggested MEMS microphones.
A few years back I talked with SY about using accelerometers for this sort of thing. He gave me some pointers, which I never put into practice. He also suggested MEMS microphones.
Step one, lay cabinet on its side.
Many here won't admit to, or forgot using this method to set engine points back in the day.
...ash-tray sand on the surface to check... though visual checking only. One advantage : the sand moves mores where it vibrates the most, so countermeasure at the opposite side (fillets, bracing, damping) are easier to locate... maybe !
This one (the old ACH-01) can be connected like an electret microphone (use a 9V battery or the like to power it). It claims an essentially flat response, but that depends on how it is mounted of course. And, as someone earlier said here, you'll get a different measurement with about every place you mount the sensor, and you still only get to know how that point vibrates, with out really much info about how much that will radiate sound. You also can identify the frequencies of resonant vibration, finding something that fixes or changes it can be surprisingly difficult.
Remlab mentioned a Bluetooth accelerometer available from Amazon in his " midrange experiment", I found something similar " Bluetooth 2.0 6 axis IMU sensor on amazon uk. Despite trying to isolate drivers from the cabinet I still find the wall vibrate, I have no idea if it's caused by the transmission of vibration or by alternating air pressure inside.