M31 Mic calibrator ?

[Dune'nQuadzilla]

Hi,

Question 1: Are there any calibrators available for the M31
microphone?

Question 2: If not then how would you recommend doing this?

Thanks

[cstrahm]

The M31 has a non-standard diameter body (8mm). We custom made adapters to fit our calibrator and other tooling, and you probably won't find any off the shelf calibrators that fit this size. The M50 series is a standard 12mm diameter and does fit most calibrators.

If you wish to have it reswept you can send it back in to us. There is a $25 charge for resweeping mics. Some people buy two M31 mics, and then they can cross check them to verify response whenever they like.

The M31 is a very low cost measurement mic. Most calibrators would cost much more then the M31 mic does itself. And then you still have the issue of the calibration of the calibrator. We can cross check between three references that we use at the factory.

It is also important to understand the limitations of a calibrator. Most only produce a single frequency or a couple frequencies. This will check the mic at those frequencies, but that is often not enough.

A damaged element can often have correct midrange response but serverely incorrect low or high frequency response. It may look fine on a calibrator, but yet the element is damaged. We have seen M31's with damaged elements where the low frequency response rolls off at 100Hz rather than 1Hz. The same thing has happened with a B&K4133 when the diaphram had microscopic perforations. A calibrator won't catch these problems.

The only way to properly check a mic is to sweep it across its full frequency range. That way you catch any and all defects.

[Acoustic]

Hi guys

Just to share with the users

I've got 5 units of M31 since 1995 (I think) and brought them with me to UK for study and in year 2000 managed to cross-check with a MLSSA system using standard big type measurement mic (I think it was a B&K) from amina technologies www.amina.co.uk

Their results were 99.99% same.

I cross check all 5 of my M31 and they are all the same.

In that same year I also cross check with anothe MLSSA from Salford University http://www.acoustics.salford.ac.uk/ and a CLEO from nxt www.nxtsound.com and all results were 99% same.

I'm very pleased with LinearX's product.




I've dropped one M31 since, but forgot which one...... :( but none has shown any signs to anomaly.

However this recent measurment job of mine may require new calibration ceritficate :(

[cstrahm]

Thanks for the feedback. We have now produced over 10,000 microphones and to date we have never received a single legitimate complaint about their accuracy, when compared to any other properly working laboratory grade mic. Even when we have the opportunity to re-sweep mics which are 5-8 years old, the new curves overlay the originals within a few tenths of a dB.