Topic: Sonic characteristics of CK61

[Carrera2]

So after buying a pair of CK61s I have been recording with them like the happy idiot and had no complaints with the results. Last night I recorded an outdoor concert and upon review noticed that the levels were suprisingly different. So I took both mics and recorded on the same recorder channel (744T) and had the mics extremely close to the same speaker. While I can understand the potential variation introduced with this "living room lab" test, I do know that similar results were obtained in a variety of locations so the results noted here are reasonably representative.

I started out just to check for relative levels. That seemed OK, but it was the frequency response that surprised me.

Is it usual for mics to have frequency curves this different?

With white noise, the sonic differences are quite apparent, as are the differences noticeable in the graphs as well. Note that the section of the foobar screen print to the right is the white noise played from its original source.

I really don't notice this in live recordings.

[I must say that after a bunch of tests, I didn't have the stamina to swap capsules and preamps so it is not clear what sonic differences are introduced by which.

[grider]

outdoor shows will not generally be as loud, and you will have none of the room reflection what you would experience indoors, both of which in part explain the variation in recording levels

[boojum]

Matched pair?

Room characteristics could be the contributing factor.  Mics are measured in an anechoic chamber.

[BC]

Good comments, you might get better results outdoors, just use 1 speaker on a calm day and stay away from any walls or the like.

[Carrera2]

Good thoughts, thanks.

I solved the problem of levels, however. When I was recording outside. I had set the 744T pre on one channel to run on the low amplitude range and the other on the high range. I fixed that and the indoor "speaker" test reflected similar levels between the two mics. Just f+&*^% up the settings. I am suprised it wasn't more apparent on the meters.

So the quest now is to understand the wide disparity in frequency response curves.

[SmokinJoe]

I think my CK61's are probably off by about 1.5db with respect to each other in overall sensitivity throughout the range... that is to say that if I record a stereo set with the V3 I generally end up running one side about 1.5db hotter than the other (and with a V3 it's easy to dial that in exactly), and when I get home it sounds pretty evenly balanced.  Or if I record with V3 set evenly, I will probably have to boost one side by about 1.5db. That's not doing a frequency response sweep, just kind of an average of what I need to make it "sound even" in headphones.  I see similar results with my CK63's.

[Church-Audio]

So after buying a pair of CK61s I have been recording with them like the happy idiot and had no complaints with the results. Last night I recorded an outdoor concert and upon review noticed that the levels were suprisingly different. So I took both mics and recorded on the same recorder channel (744T) and had the mics extremely close to the same speaker. While I can understand the potential variation introduced with this "living room lab" test, I do know that similar results were obtained in a variety of locations so the results noted here are reasonably representative.

I started out just to check for relative levels. That seemed OK, but it was the frequency response that surprised me.

Is it usual for mics to have frequency curves this different?

With white noise, the sonic differences are quite apparent, as are the differences noticeable in the graphs as well. Note that the section of the foobar screen print to the right is the white noise played from its original source.

I really don't notice this in live recordings.

[I must say that after a bunch of tests, I didn't have the stamina to swap capsules and preamps so it is not clear what sonic differences are introduced by which.

The plots aren't that different I can move a mic a few mm and get that much change in a response curve the only way to see the real differences is to make a simple test jig.

place one mic in the middle of the tweeter and woofer measure at about 12 inches or so measure the response... With out moving the mic power down the preamp and carefully unscrew the capsule again with out moving the mics position and screw in the other capsule. You should see pretty close response. But again unless these were factory matched they are not going to be exact and even if they were there are always going to be differences.

Chris

[OFOTD]

FWIW, AKG does not provide mic/capsule matching.

[datbrad]

I agree with Chris. The only way to make this kind of comparison is to remove all variables except the capsules, ALL VARIABLES. I have made close "stack" recordings of bluegrass bands in places like the Carolina Theater and the CVPAC down in Hickory, and found that even when running XY, the centimeter or so separating the caps on the vertical axis is enough to result in very slight harmonic differences between the channels, simply because this tiny spacing still places the capsules in different proximities to the individual drivers in the cabinet.

I suggest you do the living room test as Chris suggested, only swapping the caps on the same body left in fixed postion for each one, recording off one single speaker. I predict that you will find little difference between the caps. Also, you should take a look at the QA spectrogram sheets that are included with every capsule AKG sells with the capsule's serial number printed on it, to show that it met published specs before leaving the factory in Austria. I have looked at mine, and there are a couple of very tiny differences in amplitudes, but they remain with the +/- DB range specified on the data sheets.

Good Luck!

[Chuck]

I got meticulous about this a while back with my AKG capsules.
I regularly check mine. When I think there is a problem, I set up and make a recording of my DAW speakers playing tones and noise pretty loud. Mono in. I use the same mic body and just swap out the capsules. I eventually bought and sold capsules, until I got a pair that matched closely in response and output level.

edited for spelling

[Church-Audio]

I got meticulous about this a while back with my AKG capsules.
I regularly check mine. When I think there is a problem, I set up and make a recording of my DAW speakers playing tones and noise pretty loud. Mono in. I use the same mic body and just swap out the capsules. I eventually bought and sold capsules, until I got a pair that matched closely in response and output level.

edited for spelling

The biggest thing people need to know about this capsule is that it will change over time. One of the major problems with this capsule is the use of a foam spacer between the circuit board and the diaphragm there is a spring inside that is sitting against this foam. The problem is over time the foam gets deteriorated to a point where its crumbling now the force of the backplate against the diaphragm has changed and this will result in a weaker output and possibly less bass.


Chris

[datbrad]

I got meticulous about this a while back with my AKG capsules.
I regularly check mine. When I think there is a problem, I set up and make a recording of my DAW speakers playing tones and noise pretty loud. Mono in. I use the same mic body and just swap out the capsules. I eventually bought and sold capsules, until I got a pair that matched closely in response and output level.

edited for spelling

The biggest thing people need to know about this capsule is that it will change over time. One of the major problems with this capsule is the use of a foam spacer between the circuit board and the diaphragm there is a spring inside that is sitting against this foam. The problem is over time the foam gets deteriorated to a point where its crumbling now the force of the backplate against the diaphragm has changed and this will result in a weaker output and possibly less bass.


Chris

Do you know if this applies to the CK63 as well, Chris? Also, was this foam spacer used only on the older capsules going back to the early 460 days (Late '80s-Early '90s), or are the new CK capsules sold with 480s today also made this same way using the foam? Thanks !!