help ASAP comparing freq response of pair of C414s

J

jonrusso99

New member
I only have one more day to decide if want to keep a pair of C414 B-xls'. They aren't matched and Im trying to decide if they are adequately close enough or if i should go with a matched pair. Two of the people I talked to at Fullcompass felt that AKG is very reliable and two mics will be virtually identical.
Ive been trying to test them to see if this is the case. I can't hear a difference but my ears are not the most reliable. I used a Waves PAZ frequency analyzer to compare them on a couple of sources and the results are very similar, but there are a few subtle differences. Of course I can't get the mics in exactly the same position from the source but they are close.

Any suggestions on how to test further, and whether minute differences in the PAZ chart are something to worry about?
 
I don't know much about mic testing, but:

White and pink noise contain energy at all frequencies. Using one of these as the noise source may give you a more accurate picture of each mic's response. This also gives you a repeatable consistent source to compare the mics with.

Do them one at a time, and get the positioning as close as possible.

That being said, very subtle differences won't make any difference, really, and may indeed be in part due to your testing methods.

Any time a salesman tries to not sell you something, you can probably assume he's right. :D
 
borntoplease asked an almost identical question a day or two ago.

If you want to check how well they are aligned, you might get some ideas from having a look at my previous posting here, which contains the "standard procedure":

http://www.homerecording.com/bbs/showthread.php?p=1396092#post1396092

Hope this helps you decide?

In any case, as boingoman said, even if they are not perfectly matched, you may get a long way with them anyway. What I consider the most critical application is true stereo recording with an XY pair of e.g. an orchestra, where minor differences can make the stereo imaging a bit fuzzy (different frequencies from same instrument appear in different positions). I would guess that using them as a spaced pair means less impact from minor differences.

And if you plan on using them as overheads or guitar mics, I wouldn't worrry if they are not too different -- unless, that is, you're paying full price for them as a matched pair?

Rgds,


-- Per.
 
baekgaard, thanks for the suggestion. I gave it a try and something must be going wrong. I definitely got a lot of phase cancellation but still a lot came through. I had my preamps set up identically and used the invert audiosuite plug in protools to reverse the phase of one after being recorded. It seemed like most of the uppermids were still there.
I made sure all the settings on the mic and preamp were set the same and levels were virtually identical.
Something must be happening because like I said, the PAZ freq. graphs were almost identical.

Any idea?
 
jonrusso99 said:
I gave it a try and something must be going wrong. I definitely got a lot of phase cancellation but still a lot came through. I had my preamps set up identically and used the invert audiosuite plug in protools to reverse the phase of one after being recorded. It seemed like most of the uppermids were still there.
I made sure all the settings on the mic and preamp were set the same and levels were virtually identical.
Click to expand...

Sounds a bit strange.

Anyway, virtually identical levels is not really enough.

Did you make sure to adjust the levels on one of the channels until they cancel as much as possible? You said you tried to have the same settings on the preamps, but you need to adjust the levels on one channel until they almost cancel, so the levels are usually not fully identical (should be close, though, but 1-3 dB difference is not unusual).

If you don't do this crucial step, then the results will be grossly incorrect.

If it is easier for you, you might also be able to adjust the levels in protols by nudging one of the faders up/down until they cancel as much as possible... even in steps of 0.01 dB or something close to that.

Oh... and the plug you used on one channel, make sure it does not introduce any kind of delay accidently (I assume this is OK in protools).

If you already did all of this, and still get a lot of midrange, then I'd be a bit hessitant to use the mics for true stereo recording. But since you say they look almost identical on the frequency plots, there may have been something with the test, as you hint at.

Are you in a small room with many reflections? For this type of test, a dead room is best. You might want to try the test again in a larger room, as dead as possible, and maybe work the mics from a larger distance (but still close to the mic than the walls are to the mics). Outdoors could be an option also?

And the mics are well aligned and as close to one another as possible?


Just some suggestions,


-- Per.
 
You must log in or register to reply here.
Back
Top