Some microphone things I learned.

robbnj

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I posted this in the REW thread in another forum I belong to, and thought I would also share here since it involves direct use of REW.
Please remove if the share isn't appropriate or allowed.

So my UMIK-1 arrived and I had a few minutes to play while wife was away.
As promised, I did a comparison of the UMIK against the other mics I already had (and had compared against each other with surprising results).
It was far from "scientific, but I tried to make the test accurate and consistent as possible (at least enought o tell me what I wanted to know)
I tested each mic four times in a row. At the beginning of each test I confirmed the signal was coming from that particular mic, and on the 4th test I wrapped it in six layers of bath towel to make sure it was still where the signal was coming from. In other words, each response definitely came from the mic I was testing.
All were mounted on a tripod, 36" from the floor, pointed at the ceiling. They were arranged on a tripod in a line about 3" across, parallel to the front wall, as the apex of an equilateral triangle.
I calibrated REW using a calibrated RadioShack SPL meter.

The list of "competitors": UMIK-1 ($80); Dayton Audio IMM6 ($30); Audyssey "Eiffel Tower" ($40); 15+ year old Panasonic mic element from Digikey (probably $2.00 or less when purchased).
No calibration files were entered. This is just raw recording. 0-20KHz sweep.

My takeaway (just my personal evaluations and feelings; don't get angry if your results vary): These microphones are far more similar in what they pick up from my system than I ever expected or would have imagined. In my opinion that's a good thing because CONSISTENCY. But It also bums me out a bit because PRICE. I'd almost wonder if they aren't all the same capsule model in different clothing, they are THAT close. Let's put it this way: If you applied these as an EQ curve to your system and compared all four, I would be very surprised if you could tell them apart by listening.

For ME, I would have no problem using the cheapest of them to calibrate a system, once I dialed in a calibration curve for it, or saving that, I would have no problem using the cheapest calibrated one, which is the Dayton IMM6. I had read several complaints that the Dayton was lacking in it's ability to accurately pick up low frequencies. If that's the case, then it seems the Audyssey and the UMIK have a similar deficiency.
I will admit that the calibration file for the UMIK has data points than the IMM6, but I have to wonder how much that can matter when we are talking frequency responses seen in speakers in an average home setting.
And yes, the response curves are with Audyssey engaged. They're a mess, and are similarly messy when I used my IMM6 with the cal file loaded. I thought Audyssey shined in its handling of bass, but the graph is not all that different with or without Audyssey. I guess I have some troubleshooting to do.
Maybe a MiniDSP will be in my stocking next month...


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dcibel

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Cheap mice are fine for basic FR, consistency will be more dependent on the calibration process than the mic capsule. Low noise and distortion is where you should expect the pricey options to shine, as well having a mic that is very flat pre-calibration has its benefits too.
 

Wayne A. Pflughaupt

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No calibration files used – but if the graphs are with Ausyssey, so that mic’s reading has the calibration “baked in.” It’s likely that if you measured with no Audyssey, the Audyssey mic might not fare so well… ?

Regards,
Wayne
 

robbnj

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Cheap mice are fine for basic FR, consistency will be more dependent on the calibration process than the mic capsule. Low noise and distortion is where you should expect the pricey options to shine, as well having a mic that is very flat pre-calibration has its benefits too.
Yes. But these mics range from $2 to $80 (the venerated UMIK-1). The thing I am seeing is that the capsules exhibit virtually identical response (close enough for audio) at the widely varying price.
My wristwatch analogy is the $750 Movado with a $13 ETA movement, versus the $100 store-brand watch with the same movement.

I could apply the same calibration file to all four (plus the Behrenger 8000 that I returned), and get pretty much the same results from REW in my home setting.
 

robbnj

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No calibration files used – but if the graphs are with Ausyssey, so that mic’s reading has the calibration “baked in.” It’s likely that if you measured with no Audyssey, the Audyssey mic might not fare so well… ?

Regards,
Wayne
The “baked in” calibration is the response of the microphone itself, which will be the same on any device it’s used on. The calibration gets applied by the measuring device as a correction to the measurement.

So, they must use a generic correction in all Denon receivers because the mics aren’t matched to the receiver.
This would make sense if they all use the same capsules.
The age of the mics I tested: PC-15+, Audyssey-8, Dayton-5, UMIK-new, Behringer(not in graph)-new.

Though I only show this one graph, I tested the mics on multiple systems using the REW sweep tones. Strikingly similar response pickup by all the mics involved.

.
 

BenToronto

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What a coincidence, I just posted the following thoughts on the AudioSense forum. For sure, they all use similar capacitor capsules to pick up the sound. I use a second-hand mic mixer (lots of them for sale by old DJs) Behringer with phantom power for the non-USB mic. But gives me flexibility and also a read-out on how loud is the mic level and output and other bits of control.

The calibration of these mics is so close to flat that hardly worth fussing about using any correction (esp since the room acoustic tests are vastly wilder anyway).

When I compared the mics in a Mac laptop to my individually calibrated mic in the same location and not much different, north of the bass region. And, since it is testimony of your ears that ultimately matter and since testing tends to be iterative, the mic reading in a given location in your room is just a relative benchmark anyway to examine as you adjust the DSP step by step.

B.
 

robbnj

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What a coincidence, I just posted the following thoughts on the AudioSense forum. For sure, they all use similar capacitor capsules to pick up the sound. I use a second-hand mic mixer (lots of them for sale by old DJs) Behringer with phantom power for the non-USB mic. But gives me flexibility and also a read-out on how loud is the mic level and output and other bits of control.

The calibration of these mics is so close to flat that hardly worth fussing about using any correction (esp since the room acoustic tests are vastly wilder anyway).

When I compared the mics in a Mac laptop to my individually calibrated mic in the same location and not much different, north of the bass region. And, since it is testimony of your ears that ultimately matter and since testing tends to be iterative, the mic reading in a given location in your room is just a relative benchmark anyway to examine as you adjust the DSP step by step.

B.
From my reading, the $2 capsule was used very widely in telecom BECAUSE it had such a flat response. They probably made millions (Panasonic WM-61A). And then cellphones took over. I'd bet a nickel they ended up in almost every Audyssey "Eiffel tower" mic, all fo the Dayton test mics, the UNIK-1, all the way up to multi-thousand-dollar test mics.

Old test data: https://issuu.com/150176/docs/audioexpress_-_testing_panasonic_wm
 
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