Topic: SP-CMC-4U Mics

[Church-Audio]

If this a stupid question, then apologizies in advance, but why does the distortion attack 1k the most?

Distortion does not "attack" any one frequency.  1k was just chosen for the test.  What you do is put a 1k tone in (eg., through a loudspeaker) and measure the mic output (through a preamp/ADC step and into the computer).  If all was working you would see only 1k on the output.  But instead you often see *multiples* of the input (2k, 3k, etc) which are called "harmonics".  Hence the term "total harmonic distortion".  These should not be there, but are caused by nonlinearities in the response of the mic (well, the whole signal chain, actually).  You measure the distortion by comparing the desired peak (1k) to undesired ones.  Here you have (in red, I think) the main peak at (approx) -28dB and the 2k peak at -73dB.  The difference is approx 45dB.  So the distortion is 45dB below the signal.  20dB is a factor of ten (in power) so you've got, less than 1% distortion.  1% would be exactly 40dB down.

Bye...

  Richard

Wow, thank you! +T
That's a great explanation...

1k is also the standard test frequency. We all know that mics usually don't distort at high frequencies they distort  at low frequencies but its very hard to find a source ( speaker ) that puts out say 40hz with no distortion at 114db so that's why the industry standard is 1k. I think it should be 60hz 150hz and 1k and 10k and 20k because that gives you a picture of the performance of the mic the real problem is finding a speaker that has no distortion at these frequencies. That is very hard. I think its important when your producing mics to know what your distortion figures are so that when I sell a pair of mics they are matched both in distortion performance and total output is matched to with in 0.3db of each other and distortion matching is to with in 0.03% of each mic in a stereo pair.. So when your mics overload they both overload at the same time. If this is not done you could have you left side distort much earlier then the right side.

Yeah, thanks Chris for all this geek speek!

  Richard

Hehehe.. I have a lot to learn about electronics.. I will be the first to admit that. But its a lot of fun designing things. But its more fun to talk as a group to see how we can make something better. Then everyone benefits from our tinkering... Guys like you and Bob who spend lots of time seeing how things work and figuring it all out. Thats fun.. I love the smell of burnt electronics in the morning


Chris Church

[Alchemy]

If this a stupid question, then apologizies in advance, but why does the distortion attack 1k the most?

Distortion does not "attack" any one frequency.  1k was just chosen for the test.  What you do is put a 1k tone in (eg., through a loudspeaker) and measure the mic output (through a preamp/ADC step and into the computer).  If all was working you would see only 1k on the output.  But instead you often see *multiples* of the input (2k, 3k, etc) which are called "harmonics".  Hence the term "total harmonic distortion".  These should not be there, but are caused by nonlinearities in the response of the mic (well, the whole signal chain, actually).  You measure the distortion by comparing the desired peak (1k) to undesired ones.  Here you have (in red, I think) the main peak at (approx) -28dB and the 2k peak at -73dB.  The difference is approx 45dB.  So the distortion is 45dB below the signal.  20dB is a factor of ten (in power) so you've got, less than 1% distortion.  1% would be exactly 40dB down.

Bye...

  Richard

Wow, thank you! +T
That's a great explanation...

1k is also the standard test frequency. We all know that mics usually don't distort at high frequencies they distort  at low frequencies but its very hard to find a source ( speaker ) that puts out say 40hz with no distortion at 114db so that's why the industry standard is 1k. I think it should be 60hz 150hz and 1k and 10k and 20k because that gives you a picture of the performance of the mic the real problem is finding a speaker that has no distortion at these frequencies. That is very hard. I think its important when your producing mics to know what your distortion figures are so that when I sell a pair of mics they are matched both in distortion performance and total output is matched to with in 0.3db of each other and distortion matching is to with in 0.03% of each mic in a stereo pair.. So when your mics overload they both overload at the same time. If this is not done you could have you left side distort much earlier then the right side.

Yeah, thanks Chris for all this geek speek!

  Richard

so that was every reason to take away a ticket?...not that I'm following along of course 
getting back to the topic at hand...

[Church-Audio]

If this a stupid question, then apologizies in advance, but why does the distortion attack 1k the most?

Distortion does not "attack" any one frequency.  1k was just chosen for the test.  What you do is put a 1k tone in (eg., through a loudspeaker) and measure the mic output (through a preamp/ADC step and into the computer).  If all was working you would see only 1k on the output.  But instead you often see *multiples* of the input (2k, 3k, etc) which are called "harmonics".  Hence the term "total harmonic distortion".  These should not be there, but are caused by nonlinearities in the response of the mic (well, the whole signal chain, actually).  You measure the distortion by comparing the desired peak (1k) to undesired ones.  Here you have (in red, I think) the main peak at (approx) -28dB and the 2k peak at -73dB.  The difference is approx 45dB.  So the distortion is 45dB below the signal.  20dB is a factor of ten (in power) so you've got, less than 1% distortion.  1% would be exactly 40dB down.

Bye...

  Richard

Wow, thank you! +T
That's a great explanation...

1k is also the standard test frequency. We all know that mics usually don't distort at high frequencies they distort  at low frequencies but its very hard to find a source ( speaker ) that puts out say 40hz with no distortion at 114db so that's why the industry standard is 1k. I think it should be 60hz 150hz and 1k and 10k and 20k because that gives you a picture of the performance of the mic the real problem is finding a speaker that has no distortion at these frequencies. That is very hard. I think its important when your producing mics to know what your distortion figures are so that when I sell a pair of mics they are matched both in distortion performance and total output is matched to with in 0.3db of each other and distortion matching is to with in 0.03% of each mic in a stereo pair.. So when your mics overload they both overload at the same time. If this is not done you could have you left side distort much earlier then the right side.

Yeah, thanks Chris for all this geek speek!

  Richard

so that was every reason to take away a ticket?...not that I'm following along of course 
getting back to the topic at hand...

I did not take your tickets I just gave you a T+ 

[pool]

I wish there were more people like Chris, Brian, Richard and guysonic and less big-headed-big-heads in this world.

[BayTaynt3d]

What I don't understand is why SoundPros have not caught on and offered three wire battery boxes.  They are missing a *huge* market here.

They'll just tell you need phantom power. 
But I *really* do agree...

I'm not at all trying to bad-mouth Sound Professionals, but you know I asked Chris (Sound Pro Chris) a bunch of questions and got *completely* different answers from what other technical minded people on here told me.

Here is the problem with the A-T mics as I see it.. Number 1 the distortion figures they are using are not accurate.. These mics do distort badly I have measured them at 114db at 1k these mics have a distortion that is almost 15% that is VERY HIGH! I measure my own mic capsules from the factory they are 10% typical but after my mod the AT mics measure 0.5% and my mics measure 0.5%. So getting the mod done to these mics saves them from distortion but you do sacrifice some level that's why after doing the mod you should invest in a preamp.. To run your mics unless your always taping loud shows then you don't need a preamp in most cases..

Chris Church

I find people that are using the MT do need a preamp after my mod because the noise floor in the MT preamp is bad to begin with. And when you need the extra gain from the MT it brings up the noise floor too much, that being said the preamp in the Edirol R-09 is much better and more often then not for most loud shows not needed..

Hey Chris.  I think the problem is AT mics were *never* designed to run as "two-wire" at all.  If you look at any of the numerous AT powering options, they use a three-wire circuit.  Even the power modules that are battery/phantom split the battery voltage so that half is across the FET and half across the (source) load resistor.

As far as "not enough gain" that is subjective.  Sure, if you're trying to run into a NJB3 or Iriver, you've got a problem.  But several line inputs, like Edirol R01/R09, and Minidisc have enough gain to bring this up nicely for any amplified music.  I think they might add 10-15dB or so but that is quite enough.  That is why I've been using my MD so much even though I've got a lot (!) of other gear.

  Richard

Richard they are not really three wire capsule all they are is two wire capsules that have a separate ground wire to the case. The red wire is the signal the Yellow is the negative if you remove the ground wire the mic will still work but will be noisy in a true three wire capsule it will not work..

This is the same as the other capsule I use for my mics. I could be wrong but that's what I have discovered.

I gotta disagree with you there!

AT and yours are both three wire.  Red is the drain of the FET, Yellow is the source of the FET and shield is ground (of the capsule).  The other end of the capsule goes to the gate of the FET.  For two wire you short yellow and ground (at the 3.5mm stereo plug, usually).

Your mics have three wires too, +, audio, and ground.  Some variants have a source resistor (eg., 2.2k) soldered between audio and ground.

  Richard

Ok I stand corrected I have never opened up an AT mic.

So, could this be playing a role in my problem at all? I have AT943's wired from SP to be used with the Samsom adapters. For some reason, they seem to work fine using phantom and the adapters, but I've had a lot of problems running them into a 3-wire box and then into my H120. Seems like they kill the 9v battery in the 3-wire preamp quickly and/or aren't getting enough juice or something weird. But I also wondered if it was b/c of my H120 unit or something, cause it seems to work OK from the 3-wire preamp into my R4. I read somewhere about some H120's not being grounded properly internally. Could that cause the problem? Again, it seems that AT943 > Samson > FP24(Tape Out Mini) > H120 works, and even AT943 > 3-Wire Preamp > Mini Stereo-to-dual-1/4" > R4 works too, but having lots of trouble with AT943 > 3-wire preamp > H120? It's so weird, I mean WTF? In different combos, everything works! The H120 seems to work with the FP24 and samson adapters, and the 3-wire preamp seems to work with the R4, but the H120 and the 3-wire preamp don't seem to like each other for some ungodly known reason (and that's the combo I need for hardcore stealth). When I plug the 3-wire output into the H120 input, I actually get a signal for a second or two, then I hear a minor "swooshing" sound as it fades away to no signal. Weird. Tried new batteries too, and it works with the R4? WTF? Any ideas?

[Church-Audio]

What I don't understand is why SoundPros have not caught on and offered three wire battery boxes.  They are missing a *huge* market here.

They'll just tell you need phantom power. 
But I *really* do agree...

I'm not at all trying to bad-mouth Sound Professionals, but you know I asked Chris (Sound Pro Chris) a bunch of questions and got *completely* different answers from what other technical minded people on here told me.

Here is the problem with the A-T mics as I see it.. Number 1 the distortion figures they are using are not accurate.. These mics do distort badly I have measured them at 114db at 1k these mics have a distortion that is almost 15% that is VERY HIGH! I measure my own mic capsules from the factory they are 10% typical but after my mod the AT mics measure 0.5% and my mics measure 0.5%. So getting the mod done to these mics saves them from distortion but you do sacrifice some level that's why after doing the mod you should invest in a preamp.. To run your mics unless your always taping loud shows then you don't need a preamp in most cases..

Chris Church

I find people that are using the MT do need a preamp after my mod because the noise floor in the MT preamp is bad to begin with. And when you need the extra gain from the MT it brings up the noise floor too much, that being said the preamp in the Edirol R-09 is much better and more often then not for most loud shows not needed..

Hey Chris.  I think the problem is AT mics were *never* designed to run as "two-wire" at all.  If you look at any of the numerous AT powering options, they use a three-wire circuit.  Even the power modules that are battery/phantom split the battery voltage so that half is across the FET and half across the (source) load resistor.

As far as "not enough gain" that is subjective.  Sure, if you're trying to run into a NJB3 or Iriver, you've got a problem.  But several line inputs, like Edirol R01/R09, and Minidisc have enough gain to bring this up nicely for any amplified music.  I think they might add 10-15dB or so but that is quite enough.  That is why I've been using my MD so much even though I've got a lot (!) of other gear.

  Richard

Richard they are not really three wire capsule all they are is two wire capsules that have a separate ground wire to the case. The red wire is the signal the Yellow is the negative if you remove the ground wire the mic will still work but will be noisy in a true three wire capsule it will not work..

This is the same as the other capsule I use for my mics. I could be wrong but that's what I have discovered.

I gotta disagree with you there!

AT and yours are both three wire.  Red is the drain of the FET, Yellow is the source of the FET and shield is ground (of the capsule).  The other end of the capsule goes to the gate of the FET.  For two wire you short yellow and ground (at the 3.5mm stereo plug, usually).

Your mics have three wires too, +, audio, and ground.  Some variants have a source resistor (eg., 2.2k) soldered between audio and ground.

  Richard

Ok I stand corrected I have never opened up an AT mic.

So, could this be playing a role in my problem at all? I have AT943's wired from SP to be used with the Samsom adapters. For some reason, they seem to work fine using phantom and the adapters, but I've had a lot of problems running them into a 3-wire box and then into my H120. Seems like they kill the 9v battery in the 3-wire preamp quickly and/or aren't getting enough juice or something weird. But I also wondered if it was b/c of my H120 unit or something, cause it seems to work OK from the 3-wire preamp into my R4. I read somewhere about some H120's not being grounded properly internally. Could that cause the problem? Again, it seems that AT943 > Samson > FP24(Tape Out Mini) > H120 works, and even AT943 > 3-Wire Preamp > Mini Stereo-to-dual-1/4" > R4 works too, but having lots of trouble with AT943 > 3-wire preamp > H120? It's so weird, I mean WTF? In different combos, everything works! The H120 seems to work with the FP24 and samson adapters, and the 3-wire preamp seems to work with the R4, but the H120 and the 3-wire preamp don't seem to like each other for some ungodly known reason (and that's the combo I need for hardcore stealth). When I plug the 3-wire output into the H120 input, I actually get a signal for a second or two, then I hear a minor "swooshing" sound as it fades away to no signal. Weird. Tried new batteries too, and it works with the R4? WTF? Any ideas?

Is this one of my preamps??? If so I would love to take a look at the H120 and the preamp and see whats going on. I am trying to get my hands on a H120 as we speak I wanted to do some tests with it just to see how it works and where the ground problems are.. I have not had other customers complain but I have heard that the h120 has issues....

[George]

i am soo pissed off right now i cant even explain it......

so what is a better option in your guys' opinions??
 the mic mod?
 or the 3 wire BB?

either way .. where to get it/them done??

Mr.Church.. is this something you can do reasonable quick??
thanks

When I purchased my at853's from soundpro then read about phantom power, naturally, I wanted to jump aboard the gravy train.  I sent my mics back to soundpro and had them attach mini xlr inoputs at the end.  For a while, I ran with those damn xlr samson adapters and a preamp (such as the beyer mv-100 or sound devices mp-2).  It was hell taping with this setup as the samson adapters stuck out quite a bit and made it for a rather uncomfortable experience interms of stealthing or just lugging this stuff around into a open taping show. 

I eventually got a DIY mini xlr bbox from the yard sale and all was well but that sucker fell apart and I went to Chris Church and he sold me a bbox with mini xlr inputs for a good price (no preamp section, so I gotta rely on the H140's gain).  I like the at853>chris church bbox>H140 rig I run for stealth.  It's small and easy to conceal and it sounds good.  Best of luck whichever path you choose, just avoid the samson adapters though.

[Scuba Jeremy]

Take the male end of that cable into these phantom adapters (http://www.soundprofessionals.com/cgi-bin/gold/item/SP-XLRM-MINI-2) XLR Male into the UA-5 that gives 48v phantom to the AT's on top of the stand.

works like a charm and sounds great!  about to send the UA-5 off for the Bman tinkering.

Back in the day I used to run my SP-CMC-4 (old mics, before the CMC-4U) with a 2 wire battery box. I'm wondering if this phantom adapter setup would work well with a Denecke PS2 and if it would sound better than the battery box? Any thoughts? I would prefer to leave the 1/8 connection intact and not send them back in to SoundPros to be modded to XLR connectors.

[Church-Audio]

Take the male end of that cable into these phantom adapters (http://www.soundprofessionals.com/cgi-bin/gold/item/SP-XLRM-MINI-2) XLR Male into the UA-5 that gives 48v phantom to the AT's on top of the stand.

works like a charm and sounds great!  about to send the UA-5 off for the Bman tinkering.

Back in the day I used to run my SP-CMC-4 (old mics, before the CMC-4U) with a 2 wire battery box. I'm wondering if this phantom adapter setup would work well with a Denecke PS2 and if it would sound better than the battery box? Any thoughts? I would prefer to leave the 1/8 connection intact and not send them back in to SoundPros to be modded to XLR connectors.

If you do the mod that I do to your mics by connecting the Yellow wire to a 4.7k 1/8th watt 1% metal film resistor and ground you will lower the distortion of this mic from 14% at 114db to 0.5% at 114 db and you can keep your 1/8th inch plug you might need a new one as you will have to chop and re solder the resistors. ( I can send you a pair of resistors for free if you want just pay for the stamp )

[hawghunter]

thanks everyone,
just an fyi, i ran a small experiment (not done yet). nothing with mods, just differnt setting on the MT (change the setting to 'L'). Set up rig in car, system that pushes 400 watts rms (50 watts * 4 channels and 200 watts to sub, not peak but constant power). I don't know what type of dB level this would be, but its loud.  It doesn't appear to overload the MT now (no red lights). So maybe I had the wrong setting. I need to check some other things and I'll report back.  Not quite as technical as all the post here, but I'm learning.
Thanks again,     
John

[mmadd29]

Guys,

After reading through this thread, I have a few concerns with what I was planning to use for one of my setups.  I just bought these mics:

[SOUND PROFESSIONALS DELUXE MINI CARDIOID STEREO MICROPHONES. MADE IN USA.]
   
SP-CMC-22 - SOUND PROFESSIONALS - DELUXE MINI CARDIOID STEREO MICROPHONES

I was going to buy:

SP-SPSB-8 - SOUND PROFESSIONALS - MINI BATTERY MODULE WITH OPTIONAL BASS ROLL OFF AND OUTPUT LEVEL CONTROL.

Then run to my Church audio ST-9000 preamp, then to JB3

I plan on taping metal and hard rock, not in arena's, but small clubs.

Am I going to have a problem with distortion, and if so, when do I need to buy/mod.

Thanks for the great thread, I have learned alot.

[Church-Audio]

Guys,

After reading through this thread, I have a few concerns with what I was planning to use for one of my setups.  I just bought these mics:

[SOUND PROFESSIONALS DELUXE MINI CARDIOID STEREO MICROPHONES. MADE IN USA.]
   
SP-CMC-22 - SOUND PROFESSIONALS - DELUXE MINI CARDIOID STEREO MICROPHONES

I was going to buy:

SP-SPSB-8 - SOUND PROFESSIONALS - MINI BATTERY MODULE WITH OPTIONAL BASS ROLL OFF AND OUTPUT LEVEL CONTROL.

Then run to my Church audio ST-9000 preamp, then to JB3

I plan on taping metal and hard rock, not in arena's, but small clubs.

Am I going to have a problem with distortion, and if so, when do I need to buy/mod.

Thanks for the great thread, I have learned alot.

Try it first listen alot of people already have the AT mics and dont have distortion issues. Try your setup and see how it is. if it does distort I can show you how to mod the mics or send them to me I will do it for $10.00

Chris Church

[mmadd29]

Guys,

After reading through this thread, I have a few concerns with what I was planning to use for one of my setups.  I just bought these mics:

[SOUND PROFESSIONALS DELUXE MINI CARDIOID STEREO MICROPHONES. MADE IN USA.]
   
SP-CMC-22 - SOUND PROFESSIONALS - DELUXE MINI CARDIOID STEREO MICROPHONES

I was going to buy:

SP-SPSB-8 - SOUND PROFESSIONALS - MINI BATTERY MODULE WITH OPTIONAL BASS ROLL OFF AND OUTPUT LEVEL CONTROL.

Then run to my Church audio ST-9000 preamp, then to JB3

I plan on taping metal and hard rock, not in arena's, but small clubs.

Am I going to have a problem with distortion, and if so, when do I need to buy/mod.

Thanks for the great thread, I have learned alot.

Try it first listen alot of people already have the AT mics and dont have distortion issues. Try your setup and see how it is. if it does distort I can show you how to mod the mics or send them to me I will do it for $10.00

Chris Church

That sounds reasonable....thanks

[Alchemy]

Guys,

After reading through this thread, I have a few concerns with what I was planning to use for one of my setups.  I just bought these mics:

[SOUND PROFESSIONALS DELUXE MINI CARDIOID STEREO MICROPHONES. MADE IN USA.]
   
SP-CMC-22 - SOUND PROFESSIONALS - DELUXE MINI CARDIOID STEREO MICROPHONES

I was going to buy:

SP-SPSB-8 - SOUND PROFESSIONALS - MINI BATTERY MODULE WITH OPTIONAL BASS ROLL OFF AND OUTPUT LEVEL CONTROL.

Then run to my Church audio ST-9000 preamp, then to JB3

I plan on taping metal and hard rock, not in arena's, but small clubs.

Am I going to have a problem with distortion, and if so, when do I need to buy/mod.

Thanks for the great thread, I have learned alot.

Try it first listen alot of people already have the AT mics and dont have distortion issues. Try your setup and see how it is. if it does distort I can show you how to mod the mics or send them to me I will do it for $10.00

Chris Church

Just to clarify...the CMC-22s do not have AT capsules, they have Panasonic capsules...

[Church-Audio]

Guys,

After reading through this thread, I have a few concerns with what I was planning to use for one of my setups.  I just bought these mics:

[SOUND PROFESSIONALS DELUXE MINI CARDIOID STEREO MICROPHONES. MADE IN USA.]
   
SP-CMC-22 - SOUND PROFESSIONALS - DELUXE MINI CARDIOID STEREO MICROPHONES

I was going to buy:

SP-SPSB-8 - SOUND PROFESSIONALS - MINI BATTERY MODULE WITH OPTIONAL BASS ROLL OFF AND OUTPUT LEVEL CONTROL.

Then run to my Church audio ST-9000 preamp, then to JB3

I plan on taping metal and hard rock, not in arena's, but small clubs.

Am I going to have a problem with distortion, and if so, when do I need to buy/mod.

Thanks for the great thread, I have learned alot.

Try it first listen alot of people already have the AT mics and dont have distortion issues. Try your setup and see how it is. if it does distort I can show you how to mod the mics or send them to me I will do it for $10.00

Chris Church

Just to clarify...the CMC-22s do not have AT capsules, they have Panasonic capsules...

Oh I am sorry I thought they were AT mics........ In that case I dont think they can be modifyed.... I am sure they will be fine I think SP already mods these mics but I might be wrong I would ask Chris at SP. I am sure he can tell you what kind of levels these mics will work at....

Chris Church