"Note that this test did not attempt to evaluate anything other than raw frequency response. We didn't measure distortion, off-axis response, maximum SPL capability, build quality, or residual noise."

bapu
"Note that this test did not attempt to evaluate anything other than raw frequency response. We didn't measure distortion, off-axis response, maximum SPL capability, build quality, or residual noise."

:-) Glad to see someone read the article.
 
I guess he didn't realize he had to explain that none of those qualities seem to have much consequence in the context of making room measurements.
 
distortion: Hopefully it is so low that it isn't discernible when the mic encounters <90dBSPL
 
off-axis response: The mics mentioned are all omni pattern small diaphragm mics, meaning that they purportedly have very even off axis response. No omni mic has perfectly even off axis response and all have some fall off at the highest frequencies. The basic design of pressure sensitive omni capsules tends to make them perform more similarly "off axis" than not. The pressure gradient cardiod type mics, on the other hand have wildly differing off axis response characteristics.
 
maximum SPL capability: Again, the context of room testing suggests that all the mics will have 20, 30 maybe 40dB of head room before the MaxSPL is approached. As a reminder, the MaxSPL rating of a microphone is related to some defined level of distortion at it's output.
 
build quality: The mics either work ok or they don't. For example dbx has two mics which they sell as Real Time Analysis mics. One is made of "sturdy metal" and the other is made of "plastic". dbx advises that either work fine with the dbx RTA systems.
 
residual noise: This quality could be a possible concern, but I can't remember the last time I heard residual noise on any of my contemporary design mics. I can certainly turn up the gain until I find the noise floor, but at nominal gain levels it hardly seems to be a concern. Some of my vintage, or vintage style mics do have residual noise that sometimes shows up during normal use.
 
 
So anyways... just pointing this out for anyone who didn't read the article.
 
 
One thing I found very interesting is how similar all the mics are. I think this is because they are all omni mics and omni mics are inherently flat and even in their response.
 
When I compare the similarities reported in the article to the idea that professional mic calibration file services provide you with a database that represents your mic's specific frequency response it makes me wonder how much variance those professional service providers actually see from mic to mic.

Did you bother to switch your large diaphragm mic to Omni?
 
 
 
All the test mics mentioned in the article were very small diaphragm design. They are very similar to Karyn's test mic.
 
 
If you look in your Shure KSM44 user guide you will see that the omni off axis response isn't very Omni above 6400 Hz. In Omni mode, "on axis", the diaphragm has a reduced bass response starting at -3dB at 20 Hz and sloping up near 0dB at 1.2kHz where it presents big resonant +4dB peak centered at 6kHz that then plumments back to -5dB.
 
If you download the cheap as dirt Behringer ECM8000 "Measurment Mic" specifications you will see that the Omni pattern remains fairly Omni at 8000 Hz with a gentle roll off on the side The "on axis" frequency response is relatively flat from 20Hz out to 5Khz where there are a few slight peaks near the capsules resonant frequency that flatten back out after 10kHz.
 
If you are going to try to use another mic for testing... you'll probably want to use a mic that has the attributes of a test mic.

Glad you got that XLR plug fixed up. :-)

Am I wrong in thinking you can get 80% of the way there by sitting in the listening position and playing some test waveforms (i.e. sine sweep from 18kHz - 10 Hz or whatever) and adjusting your favorite EQ plugin?
 
I did this and it made a big difference, but I'd be the first to admit it isn't perfect. But it is better.

DeeringAmps
You can "fix" the peaks that way, but the "nulls" will still be nulls.

That makes sense. Thanks.

DeeringAmps
You can "fix" the peaks that way, but the "nulls" will still be nulls.
My guess is that ARC does some phase shifting to "fix" the nulls.
It helps a lot in my room.
YMMV
T

A reasonable guess, Tom, based on the fact that IKM don't go out of their way to dispel that presumption. In fact, they're annoyingly vague about what ARC really does, preferring that you just chalk it up to magic.
 
However, the patent can be read online if you want to know more (and have the patience to read deliberately-obtuse patent applications). It makes no mention of phase shifts as a means to mitigate resonances, just a complex algorithm for calculating the gain, center frequencies and bandwidths of parametric filters around measured peaks.
 
And no, sadly it can't fix nulls. The only way to do that is with multiple subwoofers and/or gobs of bass trapping.
 
stickman, you are correct: any parametric equalizer is theoretically capable of achieving the same result. ARC's strength is not in its filters, but in the software that calculates how to set them up. Doing it yourself is possible, but a lot more difficult.
 
If you attempt it, I'd advise just addressing the 3 or 4 most prominent (and broadest) low-frequency peaks, using low-Q low-gain filters, and don't shoot for total flatness. Determine those frequencies by measurement rather than by ear, by recording white noise playing through your speakers. The microphone isn't important, because you're not going to be making corrections above 500 Hz.

mike_mccue
Opinion: If you are not going to put your speakers in a place where they sound good you should rush out and buy something to make they seem better.

But if people do this, isn't it now a fact?

So is the best place to put studio monitors on your studio (computer) monitor?
 
I R CONFUSED. 

bitflipper
However, the patent can be read online if you want to know more (and have the patience to read deliberately-obtuse patent applications). It makes no mention of phase shifts as a means to mitigate resonances, just a complex algorithm for calculating the gain, center frequencies and bandwidths of parametric filters around measured peaks.

Phase is implied by the words "frequency domain" and any operations in the frequency domain include phase unless you deliberately leave it out.
 
Note that they specifically use the words "frequency domain response" (which includes phase) not "frequency response" (which doesn't).

bapu, you neeeeeeeed these!!!:
 

 
 
Ooops, my mistake... I thought it said "patented on page 30".
Nothing to see here.

mike_mccue

drewfx1

mike_mccue
It doesn't correct the room reflections but it endeavors to load the room in anticipation of the effect of the reflections you are dealing with.
 

How do you know it doesn't correct the room reflections?

 
The premise of my statement is that the room reflections, the resonance, and impedance of the air within it is not physically changed, but rather it is anticipated and the signal injected into the room is altered in some way which interacts with the existing physicality in such a way that a net effect is achieved.
 
This is, to date, my best understanding of what is going on... I'm eager to learn more.
 
 
 
 
In the mean time, I'm saving up for a full set of Ninjapanels™ to mount on the walls and to use as gobos. They have induction motivated pivoting platelets that respond at 96kHz sampling to achieve >96% diffusion in any room larger than a shower stall, and recent developments inspire reason to feel encouraged that a shower stall gambit will soon be realized.

These?

I tried to look them up, sound's interesting...
 
Seriously Mike, a link for Ninja Panels? Can't find them, inquiring minds and all...
 
J

Guitarhacker 
 
 
Some time back, I was kind of taken to task for suggesting that I could use the ARC mic to record my acoustic guitar since it's freq response was flat and not warm like some other mics. Kind of a shoe on the other foot thing.
 

So... did you go ahead and try it?
 
J

bapu

mike_mccue
Opinion: If you are not going to put your speakers in a place where they sound good you should rush out and buy something to make they seem better.

But if people do this, isn't it now a fact?

5 stars and 48 reviews at Sweetwater!!!

I have a hard time imagining the bapu as anything but a wise man.
 
I'll bet those macrame things could easily get 48 "it decoupled the bass from my table" 5 star reviews too if Sweetwater sold them. 
 
Someone should try making them out of mil spec nylon. Maybe call them SpaceSager™ or something.