What "speaker or transducer" is used for RTA - AVS Forum
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post #1 of 8 Old 05-25-2013, 06:53 AM - Thread Starter
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I see all these mic curves from 20hz to 20 Khz. users and tutorials post

What is being used as a transducer to produce these wide freq tones? Surely a laptop won't due.

Are users using headphones?
Any sound box that with specific speakers?

I vision your mic some distance from a speaker of sort?

So far I have performed RF Mic systems sweeps, now I would like to graph about 6 different mics.

TIA
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post #2 of 8 Old 05-25-2013, 02:39 PM
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You need a calibrated mic to perform useful measurements. Try here.
Measurement distance is traditionally 1m, but it will depend on whether indoors or out. Indoors you will need to gate to keep reflections from contaminating the measurement, unless the purpose is to determine the effect of the room.
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post #3 of 8 Old 05-25-2013, 04:31 PM
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Quote:
Originally Posted by jerryray View Post

I see all these mic curves from 20hz to 20 Khz. users and tutorials post

What is being used as a transducer to produce these wide freq tones? Surely a laptop won't due.

Are users using headphones?
Any sound box that with specific speakers?

I vision your mic some distance from a speaker of sort?

So far I have performed RF Mic systems sweeps, now I would like to graph about 6 different mics.

TIA
There are a lot of different "things" going on in your post.

ANY speaker can produce 20-20Khz. Now how LOUD those extremes are-is quite a different story.

What you see posted are simply measurements of the particular speaker in question.

Yes a laptop is used as the measurement system and tone generator.

IF you are trying ot compare different mics, then the best you can do is to have a comparison-not an absolute of the mic itself.

What exactly are you trying to do/accomplish-that would help.

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post #4 of 8 Old 05-25-2013, 04:37 PM
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Quote:
Originally Posted by A9X-308 View Post

You need a calibrated mic to perform useful measurements. Try here.
Measurement distance is traditionally 1m, but it will depend on whether indoors or out. Indoors you will need to gate to keep reflections from contaminating the measurement, unless the purpose is to determine the effect of the room.
You don't need a calibrated mic or a calibrated measurement system if one needs to do is measure the freq response. It could be 20dB (or more) off and the measurement will still be just fine.

The only thing that would be off is the absolute SPL level. ANd for most people that is not that important-at least when looking at freq response.

All a "calibrated mic" gives you is the reference output voltage. The rest of the system ALSO has to calibrated in order to do accurate SPL measurements.

But again-in MOST measurement applications absolute SPL is not important.

I do tons of measurements-and probably 99% are not calibrated-it doesn't matter for what I am trying to accomplish at the time of measurement.

The only I time I bother to calibrate the system is when I am gathering data for a data sheet.

All the other times it is purely "relative differences" that I am interested in.

Just wanting to clarify

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post #5 of 8 Old 05-25-2013, 04:40 PM
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Quote:
Originally Posted by A9X-308 View Post

You need a calibrated mic to perform useful measurements. Try here.
Measurement distance is traditionally 1m, but it will depend on whether indoors or out. Indoors you will need to gate to keep reflections from contaminating the measurement, unless the purpose is to determine the effect of the room.
The information on the mic you posted a link for is not so much SPL calibration-but rather freq offsets-due to the response not being flat.

To me those are very different things.

A real measurement mic is FLAT form beyond 20-20K-so the only that is needed is SPL-NOT correction data-which is what Dayton is saying is "calibration".

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post #6 of 8 Old 05-25-2013, 10:41 PM - Thread Starter
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OK, thanks for the responses. What I am trying to accomplish is sweep the RF Mic system, then sweep the system with 6-7 different Lav mics.
The system is one transmitter and one receiver

I service the Lectrosonics Professional mic systems. Typically I sweep and use THD for our proof of performance.

Some customers send me mp3 files claiming hiss, peaks, hums. We can't duplicate this.

So I want a library reference to compare with this condition when it happens again.

I hope I have explained what I am trying to do.

I use a Audio precision unit to do a THD, Level,, IMD, Phase, SN.

With theTruerta software I am hoping to measure what I can;t hear.
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post #7 of 8 Old 05-26-2013, 08:12 AM
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Quote:
Originally Posted by jerryray View Post

OK, thanks for the responses. What I am trying to accomplish is sweep the RF Mic system, then sweep the system with 6-7 different Lav mics.
The system is one transmitter and one receiver

I service the Lectrosonics Professional mic systems. Typically I sweep and use THD for our proof of performance.

Some customers send me mp3 files claiming hiss, peaks, hums. We can't duplicate this.

So I want a library reference to compare with this condition when it happens again.

I hope I have explained what I am trying to do.

I use a Audio precision unit to do a THD, Level,, IMD, Phase, SN.

With theTruerta software I am hoping to measure what I can;t hear.
What i would do isget a good quailty studio monitor-or something that has a pretty flat response. Since you are talking wireless mics-20-20K is not important-as the mics will never be used to capture those extremes.

And unless you are using omni capsules on a small body-the mic itself is going to have a big influence on what you actually measure-ie it will not be flat.

HOWEVER if you capture REFERENCE traces of know good mics-then you can compare the reference to the "subject mic".

However this will not do any good for things like hiss and hums. Most of the time those are operator errors-and your Audio Precision will do a better job of looking at that.

The only thing an RTA (and HIGHLY SUGGEST NOT using an RTA-but rather a transfer function-there are so many things wrong with an RTA-PARTICUALLY for what you are looking to do). would do would show variences in the freq response.. Btu that is also important to measure and know.

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post #8 of 8 Old 05-26-2013, 09:54 PM - Thread Starter
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OK I have made some test today by using A pro Sony headset on top of the lav mics. Not exact or scientific, but I do have a curve baseline for 6 different lav mics now.
Also found a file save bug in TrueRta software.
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