Chris,
Could there be a difference in the way you are measuring distortion in your lab, and the way this affects the mics under concert conditions?
The reason I ask is that I have made hundreds of recordings since Nov '02 (and heard other tapers efforts too) with SP-CMC2s (AT831 cardioids), that are not distorted to my ears, unless the PA is also distorting.
I have tested them at the loudest venues London has to offer (The Borderline, and The Underworld, which can be painful in seconds without earplugs), and made killer recordings.
I'm not having a go, just trying to further my knowledge.
Humbug
What I do is measure distortion at 1k. Now when I measure my mic capsules unmodified they have a distortion of 7% at 114db at 1k when I measure AT 853 Its the same after my 4.7k mod both mics are 0.5% distortion. When I measure the 900 series mics the distortion is 0.5% with out any mods what so ever.. I have measured lots of these mics over 10 pairs that's 20 mics and they were all the same. Now its possible you could be subjecting the mics to a lower battery voltage and a much higher spl say 122 db but your ears would be bleeding before that happens.
I think its possible ( just a theory ) some of these mics have the same fet as the 853 or there is some kind of defect in the capsules of these mics * maybe * that is causing the distortion on some of the 900 series mics. I dont know but my tests show they are at least performing as well as my modified mics perform.
When you put my mod on a pair of mics that dont need it your actually degrading the mics signal to noise ratio unnessisarily. I am not saying that under certain applications these mics will not distort. But there are a lot of variables. My testing is not one of them. Its a pretty standard test I do.
I can measure the same mics over and over again and get exactly the same results. I would like to run a test on a pair of mics that is "known" to distort if someone has a pair they would like to send me. But to be honest guys its impossible to rule out a lot of variables because each concert is different.
For example some distortion is caused by wind. The air movement a big PA system is capable of can easily bottom out a diaphragm to its back plate and cause distortion how many of you use windscreens * if you look at the 900 series mics you can see the diaphragm quite well that tells me there is not enough wind protection built into the mics and windscreens are 100% necessary.
Also distortion does change with frequency its possible the 900 series are very stable at 1k but not so much at 100hz and below.. this is not very desirable because good microphones should be pretty linear at low and high frequencies as far as distortion is concerned, and if this mic is subject to distortion at low frequencies it might be because the back chamber of the microphone has a tuning issue.
I dont know, all I know is that the mics I tested in the same exact method I test all my mics at were operating at the same distortion point at my other mics after my mod. So I feel its not really necessary. But that being said I would love to get some samples of the 900 series mics overloading so I can hear it and I would like to get a few pairs of mics to test again.
You also have to remember these mics were NEVER designed for high spl at low frequency.. They are after all lapel mics.. So it would seem its possible the design engineers at AT did not test for ultra low frequency distortion. And it would make sense not to test for it because lets face it this mic was not designed for recording loud sources. As most lapel mics are not. I really dont know what the issue is but I will try and figure it out for the benefit of my fellow T.S members
Topic: mics directly into recorder question (at943 4.7k/853/ssdsm6; r-1;r09;iriverh120 (Read 32882 times)