Frequency Response Chart: Precise! Meaningless!

[joelpatterson]

Don't get me wrong--my new [matched] pair of Earthworks QTC30's are the cat's meow in every way. But I'm a little puzzled by the frequency response chart that accompanied them.

There are two lines on the same chart: one showing a dip in the mids, and the other a rise in the mids, and a fall-off at 22kHz vs. a fall off at 30kHz. There is no way to distinguish which line is a graph of which mic. The way they meet at 10kHz... there is no way to know if the mic that's low in the mids also drops off earlier... or not.

A pretty bizarre response from their support staff assured me that even with these fluctuations, the mics are "matched", and any way the chart is just to show me how matched they are, and they could look it up and tell me which was which, but why bother?

Huh?

[Kiwiburger]

I'm not sure that "matched mics" mean diddly squat. You want a stereo effect, right? A mismatched set would probably sound better and more 'stereo'.

[tINY]

So, what is the variation in the mid range and how much variation is there at 25 kHz?




-tINY

[Jim Williams]

Reminds me of the "frequency response" graph that came with the Royer ribbon I saw. It was hand drawn over a non-linear "log" frequency plot. Totally bogus info showing flat resonse to 16k when I know I heard nothing above 8k from it.

Jim Williams
Audio Upgrades

[mixerguy]

Heya Jim

maybe YOU don't hear anything higher than 8k!



JUST KIDDING!!!

[joelpatterson]

Originally Posted by tINY

So, what is the variation in the mid range and how much variation is there at 25 kHz?




-tINY

Probably less than a db's worth of difference in the mids, at 25kHz one is even, one is up a db.

Well when you put it that way... still... why oh why not just one graph = one mic, another graph = another mic? Isn't this doubling up... just kinda... stupid?

[tINY]

I imagine the graph plotted on opaque paper. How do you compare the two if they are printed on different paper?

If you really must know which is which, you need to record three tones played though a speaker and record each mic in exactly the same position.

Normalize the levels using a 10kHz tone and then use a 1k and a 20k tone to distinguish the two.

Jeeze......



-tINY

[joelpatterson]

I would compare the two: how much they each deviate from the "zero" line. I just say it's idiotic to have these ultra-precise readouts, and then no way to match them to either mic.

It is pretty esoteric, I admit...

[tINY]

The purpose of the graph is to show how well they match.

If you bought them as measurement mics, each would come with a separate graph and a disk that had the numerical data on them so you could calibrate your system.

They may be able to send you this anyway.




-tINY

[joelpatterson]

Well, it kind of surprised me because the support from Earthworks is supposed to be excellent? And when I brought all this up, Alex told me, "I could send you separate graphs," and then went on to explain why he wasn't going to bother.

And then he said that even though the graphs didn't "match", each one was within the spec, which leads me to conclude that ANY QTC30 that falls within the spec will match ANY other QTC30, so what does the word "matched" mean?

I say again, huh?

[Bob Ross]

Now you know why Earthworks is the Avis of omni mics.

[joelpatterson]

I keep learning so much... why aren't I smart?

[swankdoc]

Originally Posted by joelpatterson

I keep learning so much... why aren't I smart?

utfsf

[joelpatterson]

... as if I had the time....