Hi all,
I've made a transducer that is crude but works, it takes mechanical vibration and reports it as a voltage on my multi-meter.
I'm curious if there's a simple way to take this voltage as an input into a basic audio interface (I have a USB audio interface that takes TRS and XLR input microphones) and then take that signal into graphing software like REW or Audacity, etc, just for easy graph correlation with other measurements like frequency sweeps with my actual microphone, etc. Also not sure if I need to calibrate the signal or not?
It's literally a 12" driver with the leads on a multi-meter but in a controlled setup and frame. The back-and-forth mechanical movement of the driver when it vibrates produces AC voltage that I measure. I'm currently getting readings of single and double digits mV values. Low. Triple digit at worse, like 200~300 mV.
So just looking to see if I can wire that driver to a terminal that goes into my audio interface and read it as signal in software? Or if it will be problematic in some way or something I just don't know about? I just want to measure the voltage readings easily and graph it easily. It doesn't need to be accurate; the system issues will be constants anyways.
Very best,
I've made a transducer that is crude but works, it takes mechanical vibration and reports it as a voltage on my multi-meter.
I'm curious if there's a simple way to take this voltage as an input into a basic audio interface (I have a USB audio interface that takes TRS and XLR input microphones) and then take that signal into graphing software like REW or Audacity, etc, just for easy graph correlation with other measurements like frequency sweeps with my actual microphone, etc. Also not sure if I need to calibrate the signal or not?
It's literally a 12" driver with the leads on a multi-meter but in a controlled setup and frame. The back-and-forth mechanical movement of the driver when it vibrates produces AC voltage that I measure. I'm currently getting readings of single and double digits mV values. Low. Triple digit at worse, like 200~300 mV.
So just looking to see if I can wire that driver to a terminal that goes into my audio interface and read it as signal in software? Or if it will be problematic in some way or something I just don't know about? I just want to measure the voltage readings easily and graph it easily. It doesn't need to be accurate; the system issues will be constants anyways.
Very best,
The only issue would be too much output from the 12" driver when pushed with loud audio but most audio interfaces should handle it just fine. Connect it like a microphone, its the same except a diaphram thats 12" in diameter instead of 1". Its HF response won't be so great. The LF pretty good. In some PA systems the drivers were used as both speakers and mikes so its nothing new.
Ok,
So do you think I could just wire it directly to an XLR terminal (3 prong) and go? I guess I'll see if I can find examples of this and what was done with the ground pin?
Very best,
Simple, it works.
I just did pos/neg leads from the driver to the leads on the 3 pin XLR cable and into the audio interface. I adjusted gain at the interface until it had enough signal to be happy with it.
I ran some REW measurement and just pushed on the driver to get a voltage going and it recorded it.
Working model for now. Will refine.
Very best,
I just did pos/neg leads from the driver to the leads on the 3 pin XLR cable and into the audio interface. I adjusted gain at the interface until it had enough signal to be happy with it.
I ran some REW measurement and just pushed on the driver to get a voltage going and it recorded it.
Working model for now. Will refine.
Very best,
Intercom systems use speakers as microphones, and they work well but the speaker resonance produces a very colored sound. The two solutions are a ~1KHz 6dB "high-pass" filter, or, load the speaker at the rated impedance. This tames the resonance to produce a balanced frequency response.
Hi,
Well, its a bust. I did a comparison and the vibration it measured and made voltage from didn't change much, despite SPL changing a lot.
A quick test setup.
I put two different subs in the same location in a room, same distance from the front of the baffle to the test equipment. Level matched at one frequency. Ran the sweeps and measurements.
I moved the other away and measured one at a time in the same location at the same distance from the instruments level matched at 1 frequency (28hz at 100db).
So, they are only level matched at 28hz. The room response is quite similar here in the same physical location and distance. Some minor differences because they're not the same dimensions, etc, and different designs entirely (sealed vs open baffle).
The important thing to note is that something excited SPL at 8~10hz on my sealed setup, 20db higher than the open baffle setup. Not hard to expect either. The rest is very similar. But down under 20hz the sealed shows higher SPL and yet the measured vibration from the 12" transducer is staying basically the same. It measures vibration when it happens, the same way, but doesn't seem to increase down at those frequencies. So it's either not sensitive, or dampened, or limited resolution, etc. I don't know. Either way, infrasonic is essential for tactile response comparison, it's the only thing you experience (we don't hear 10hz normally obviously). So if I can't measure a difference at 10hz then it's pointless to use this instrument. So I think this is getting scrapped and will be just a failed experiment.
Very best,
Well, its a bust. I did a comparison and the vibration it measured and made voltage from didn't change much, despite SPL changing a lot.
A quick test setup.
I put two different subs in the same location in a room, same distance from the front of the baffle to the test equipment. Level matched at one frequency. Ran the sweeps and measurements.
I moved the other away and measured one at a time in the same location at the same distance from the instruments level matched at 1 frequency (28hz at 100db).
So, they are only level matched at 28hz. The room response is quite similar here in the same physical location and distance. Some minor differences because they're not the same dimensions, etc, and different designs entirely (sealed vs open baffle).
The important thing to note is that something excited SPL at 8~10hz on my sealed setup, 20db higher than the open baffle setup. Not hard to expect either. The rest is very similar. But down under 20hz the sealed shows higher SPL and yet the measured vibration from the 12" transducer is staying basically the same. It measures vibration when it happens, the same way, but doesn't seem to increase down at those frequencies. So it's either not sensitive, or dampened, or limited resolution, etc. I don't know. Either way, infrasonic is essential for tactile response comparison, it's the only thing you experience (we don't hear 10hz normally obviously). So if I can't measure a difference at 10hz then it's pointless to use this instrument. So I think this is getting scrapped and will be just a failed experiment.
Very best,
Do you have a box to put the driver in? Even a reasonably stiff cardboard box? You are trying to measure pressure with that. For vibration the cone spider will be too stiff at low frequencies. You can also add a weight to the cone but then you are measuring how much your stand vibrates.
Pretty much all Audio systems have little output below 20 Hz. In fact below 60 Hz most are rolling off.
Pretty much all Audio systems have little output below 20 Hz. In fact below 60 Hz most are rolling off.
I could build nearly anything for it, but if its not going to be a good transducer to show vibration into infrasonic, then its just the wrong tool and was a fun quick experiment. Doesn't look like its going to be useful though. Still, learned a bunch. Might still fiddle with it some but ultimately it's not going to do what I'm looking for which is measure vibration and translate that as a tactile reseponse metric.
I'm gonna go back to my accelerometer and angular velocity sensor and build a drum or something with that.
Very best,