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Response to Dennis H. post #28, I believe

Crossover design phase issues are relative; we are not using absolute phase to design the crossover. If you use the same microphone for all of your measurements, phase error should not be an issue. I believe that John K. has a post on the diyaudio.com site discussing this.

Jay
 

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Herb's the best! Always very quick on delivery.
Well, not always (unfortunately). In fact I'm working up some mics and meters today that (when all is said and done) will have shipped out about 3-4 days after folks placed their orders. It comes down to a) do I have product in stock, and b) am I actually around to ship the products. Most times folks get lucky and I can move stuff fairly quickly. Some folks aren't nearly so lucky.

I'm hoping that in the next six to twelve months I can hire on some help and ship things more consistently. But for now, I'm trying my best.
 

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This might be a dumb question, but why isn't Cross Spectrum accredited by ANSI, ISO, etc?
Going through that process would require a statistical analysis of my processes, calibrations of my measurement equipment made directly against NIST primary sources (as opposed to know where my equipment is calibrated by cal labs who in turn have their equipment calibrated against primary sources) and annual inspections/audits by certifying agencies, all of which I have to pay for. (it may also require that I set up a stable temperature/humidity environment but I'm not positive about that). I would also have higher insurance costs since any "accredited" mics/services I offer might be used by customers for multi-million dollar projects where measurement accuracy is paramount (environmental noise, concert hall renovations, etc) and if something went wrong I could be liable for heavy damages. I looked into it a while back, and the initial costs for all of this would be in the low mid-five figures (upgrading equipment, performing statistical analysis, upgrade my lab, etc), and the annual audit/inspection costs would be in the low-five figures. And that's just for ANSI/NVLAP (USA) accreditation, ISO and IEC have much stricter requirements.

I could do it, but then the prices I would have to charge to recoup my costs would be similar to what other NIST-traceable labs have to spend: ~$150 for mic basic calibrations, $250+ for meter calibrations, etc. And at that point I would be directly competing with the few dozen other NIST-traceable labs around the country, and frankly there wouldn't be much point.

As the other parts of my business grow there is always the possibility that we may decide to gt NVLAP accreditation for other purposes and in that case I may let the mic biz free-ride on that accreddition, but that is a long ways off.
 

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News from Spain.

I'm just receiving a EMM6 Basic+ calibrated mic from CSL. Thanks Herb for your very good job. Only 7 days from payment. This is awesome speedy.

And mic appears great. Response curve is almost flat from 20 to 3Khz, and only a few crest of 4dB at 12.5 Khz.
Cal files have a lot of intermediate values.
I am very happy and wanting to play with it.:nerd:


What I did not expect was the size of this micro. I have another Audyssey microphone, and is smaller. It seems that size does matter, even in the micro world:R

Again thanks Herb.:clap:
 

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Is it possible to get the omnimic run through your calibration process and provide a correction file????
There are two issues with calibrating the omnimic microphone:

  1. 2
  2. The version I saw last year only worked with the Omnimic software. I've heard rumors that has changed with recent versions and that now the Omnimic shows up as a USB audio device - if that's true, than I can use it with my rig, otherwise I can't measure it (at least not easilly)
  3. The diameter of the Omnimic mic I played with wasn't a standard diameter (I don't understand why mics manufacturers do this, the industry has standardized on 1/4", 3/8", 1/2", and 1" for decades now), which makes it harder for me to use in my low-frequency jig.
Assuming the mic does show up as a USB audio device, if someone wants to send one to me, I'll check it out.
 

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There are two issues with calibrating the omnimic microphone:

  1. 2
  2. The version I saw last year only worked with the Omnimic software. I've heard rumors that has changed with recent versions and that now the Omnimic shows up as a USB audio device - if that's true, than I can use it with my rig, otherwise I can't measure it (at least not easilly)
  3. The diameter of the Omnimic mic I played with wasn't a standard diameter (I don't understand why mics manufacturers do this, the industry has standardized on 1/4", 3/8", 1/2", and 1" for decades now), which makes it harder for me to use in my low-frequency jig.
Assuming the mic does show up as a USB audio device, if someone wants to send one to me, I'll check it out.
Tell me where I should measure for the diameter of the mic. If its one of the standardize ones you listed, I'd be interested in sending it in for testing. It is the more recent version of the mic, not the original one.
 

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Tell me where I should measure for the diameter of the mic. If its one of the standardize ones you listed, I'd be interested in sending it in for testing. It is the more recent version of the mic, not the original one.
At the "business end" of the mic, at the capsule (it's just over 1/4-inch IIRC).
 

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I must be doing something wrong

Hi Herb,

I am a recent owner of a calibrated Galaxy meter (verified +).


How reliable is calibration at the extremes supposed to be, specifically in the sub-10Hz region?

The reason I am asking is that results I am getting do not look realistic at all.

As you can see in the attached REW measurement snapshot I am getting 30dB jump from 70db at 15Hz to almost 100dB at 5Hz. Is it even theoretically possible?


The calibration file I amusing with REW is called "one_third_octave_band_response_random-incidence_C-wtd.frd". Is this correct file to use?

Here's the content of the file:


5 -30.49 0
6.3 -23.99 0
8 -19.35 0
10 -15.72 0
12.5 -12.62 0
16 -10.03 0
20 -7.9 0
25 -6.16 0
31.5 -4.74 0
40 -3.58 0
50 -2.66 0
63 -2.01 0
80 -1.65 0
100 -1.29 0
125 -1.04 0
160 -0.83 0
200 -0.73 0
250 -0.62 0
315 -0.5600000000000001 0
400 -0.48 0
500 -0.4 0
630 -0.28 0
800 -0.07000000000000001 0
1000 0 0
1250 -0.24 0
1600 -0.38 0
2000 0.44 0
2500 0.38 0
3150 0.36 0
4000 1.54 0
5000 2.55 0
6300 3.05 0
8000 2.2 0
10000 -0.19 0
12500 -5.07 0
16000 -10 0
20000 -15.2 0
25000 -19.97 0

I am not sure what it is that I am doing wrong. Any guidance you can offer is much appreciated.
 

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Re: I must be doing something wrong

Hi Herb,

I am a recent owner of a calibrated Galaxy meter (verified +).


How reliable is calibration at the extremes supposed to be, specifically in the sub-10Hz region?

[snip]
I'm not an REW expert, but I would recommend trying the "narrow_band_response_random-incidence_C-wtd.frd" instead of the one-third octave band file. Also, do you have the meter set to C-weighting when you make the measurement? The data you quoted looks plausible - the Type 1 C-weighting value at 5 Hz is -25 dB, at 8 Hz -17.7 dB, at 10 Hz -14.3 dB, at 12.5 Hz -11.3 so it's certainly in the right ballpark.

What is the serial number of your meter?
 

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Re: I must be doing something wrong

SN 110508226

I am using C weighting and response slow.

I will try the narrow band cal file and report back.

Thank you very much!
 

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Re: I must be doing something wrong

results using both cal files look very close to me.
The cal files for your meter look kosher. Try checking in the REW forum to make sure there isn't something wrong with the software settings. If that's not it, maybe your meter went bad - if the REW forum folks can't clear it up, you can ship the meter back to me and I can take another look.

(also, did you take advantage of the HTS discount for your meter?)
 

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Re: I must be doing something wrong

The cal files for your meter look kosher. Try checking in the REW forum to make sure there isn't something wrong with the software settings. If that's not it, maybe your meter went bad - if the REW forum folks can't clear it up, you can ship the meter back to me and I can take another look.
sounds good, thank you very much.
(also, did you take advantage of the HTS discount for your meter?)
no, I did not
 
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