Galaxy CM-140 Calibration File Info Thread

**Sonnie** · **03-09-07, 07:03 PM**

I stated that I would provide a calibration file for the CM-140 and I plan on doing just that. However, it may be a couple of weeks before I actually post it. Some of you will no doubt ask why. There are a couple of reasons for this that I will explain below.

First of all, I am having my ECM8000 re-calibrated at West Caldwell Calibration Lab. These guys are the real deal. The cost for calibration is $150. I could provide you with a calibration file today, but once my mic has been re-calibrated, the .cal file may be slightly different than it is now. While more than likely it will be very close, I prefer to make absolutely sure and not be releasing a .cal file today and then in two weeks be releasing another .cal file telling you the first one is no good.

Secondly and most assuredly something that will excite several of you... my ECM8000 is going to be calibrated down to at least 5Hz. Once it is returned, I will hopefully be able to provide you with a calibration file to 5Hz or lower for the CM-140.

In the meantime you can use the CM-140 as is and be fairly close.

Once the .cal file is ready... it will be available for download on the Downloads page.

**brucek** · **03-09-07, 07:32 PM**

Quote:

In the meantime you can use the CM-140 as is and be fairly close.

By checking the C-Weight box in REW of course.......

brucek

**Ilkka** · **03-09-07, 07:44 PM**

Quote:

brucek wrote:

By checking the C-Weight box in REW of course.......

brucek

Well actually...it was ~7 dB high @ 10 Hz with the C-weighting checked, and ~7 dB low without it. Pick your poison.

**Sonnie** · **03-09-07, 07:49 PM**

You could use the ECM8000 .cal file with no C-Weighting and be almost there.

ecm8000.cal

**Ilkka** · **03-09-07, 07:53 PM**

Quote:

Sonnie wrote:

You could use the ECM8000 .cal file with no C-Weighting and be almost there.

ecm8000.cal

True. Assuming your current calibration for the ECM8k is accurate, you'd be less than 2 dB off @ 10 Hz which is more than enough accurate for most in-room measurements.

**Sonnie** · **03-09-07, 08:01 PM**

Quote:

Assuming your current calibration for the ECM8k is accurate

Yeah... I hope it is because we've been using it for quite a while to calibrate against. I think Kim does a good job from what I've been told... and if you remember yours and my mic are almost spot on. But we will know for sure here pretty soon... either way.

**Ilkka** · **03-09-07, 08:15 PM**

Quote:

Sonnie wrote:

Yeah... I hope it is because we've been using it for quite a while to calibrate against. I think Kim does a good job from what I've been told...

I don't doubt that at all.

Quote:

and if you remember yours and my mic are almost spot on. But we will know for sure here pretty soon... either way.

My mic? I've never had an ECM8000. My mic is recommended by the ETF Acoustics and it's only ~0.6 dB off at 10 Hz without a calibration file.

**Sonnie** · **03-09-07, 08:29 PM**

Exactly... but when we both provided calibration files for one of the RS meters a while back... you might remember we were spot on, except at one frequency I believe. This would indicate that mine must be pretty accurate.

**Geoff Gunnell** · **03-10-07, 01:32 AM**

Thanks for taking your time and money to re-reference your mic to a physical standard before calibrating others' equipment from it, Sonnie. It's the right thing to do. It's also kind of an honor, I think, to transfer a standard of measurement. We know in advance that we cannot get it exactly right, but we have the courage to try anyway

**tweakophyte** · **03-10-07, 09:29 AM**

Hi-

Yes, thanks for spending the extra bucks to make sure your mic is "perfect" so our mics will be.

I'm glad I got in on the buy. It's laying the groundwork for my next investment into my HT, too.

**Sonnie** · **03-10-07, 05:41 PM**

It is my honor to do so... I want nothing less than as good as I can provide for everyone...

**Eric_RP** · **03-13-07, 10:17 AM**

Quote:

Sonnie wrote:

Secondly and most assuredly something that will excite several of you... my ECM8000 is going to be calibrated down to at least 5Hz. Once it is returned, I will hopefully be able to provide you with a calibration file to 5Hz or lower for the CM-140.

This is awesome Sonnie.

Thanks much for doing this! Can't wait to get it and put it to use.

Eric

**ifeliciano** · **03-15-07, 12:24 PM**

Thanks Sonnie !!

**nerdful1** · **03-16-07, 11:41 AM**

Are you having the high end done, and above 8khz? Now I think I should have bought a 140 instead of getting my RS charted...Jim

**Sonnie** · **03-16-07, 12:05 PM**

The initial plans are to provide a calibration file for the bass region. I will provide some measurements full range, but I'm not sure anyone is going to be up to the task to complete a calibration file for it. It would be a fairly gruesome task IMO.

**Vader** · **03-16-07, 12:27 PM**

Sonnie,

I have always read that the Rat Shack meter is 2 to 3 dB low when using the pink noise on DVE to calibrate (ie. when the meter reads 72 dB it is actually about 75 dB). Does the Galaxy meter need a similar correction factor?

**Sonnie** · **03-16-07, 01:28 PM**

I'm not sure how anyone could qualify that correction. Your response is not perfectly flat and the SPL meter is going to read the highest peak in your response when that pink noise is playing. If that peak is at 500Hz, then neither meter is really going to need any correction, yet if it were at 20Hz it would... but with pink noise how can you tell where the peak is unless you have an RTA. I think most of the time we see peaks down low in the 30Hz to 60Hz region. With the old RS meters it could mean anywhere from 2db - 7db of correction, with the newer RS meters it could mean from .5db - 2db and with the CM-140, it would not need any at all in that region. So ultimately, I would say you would not need to perform any corrections to the CM-140 for pink noise.

**Vader** · **03-16-07, 02:40 PM**

Sonnie,

Ron had me use that correction when we were trouble-shooting my first cylinder last year. He had me run several tests using both my AVR test tones and DVE (which is 10dB hot on the sub test). When I reported the results of the sub tests, I thought they were all 2-3 dB low, but Ron said they were spot-on, because of this correction. Based on this, I calibrated the subs to "flat" with respect to the meter, so it would really be 2-3 dB hot (or so I understood).

Edit: My wife just called and said that my meter came today, so I guess I'm gonna be re-calibrating tonight. It will be interesting to see how far off my old Rat Shack meter really is (I bought it when I was in college - 1991 - and have never re-calibrated it...). Thanks so much, Sonnie!

**Ilkka** · **03-16-07, 07:28 PM**

Quote:

Vader wrote:

Sonnie,

I have always read that the Rat Shack meter is 2 to 3 dB low when using the pink noise on DVE to calibrate (ie. when the meter reads 72 dB it is actually about 75 dB). Does the Galaxy meter need a similar correction factor?

DVE's pink noise is not good for setting up the subwoofer level. It's too wide band to be accurate if your frequency response isn't close to dead flat. Especially any amount of "room curve" can cause one very interesting results. AVIA and pretty much all receivers have band limited pink noise for setting up the subwoofer and speaker levels. Usually the noise for subwoofer is limited in ~40-80 Hz range. Since normal C-weighting reads around 1-2 dB low in that range, the same amount of correction is needed for the CM-140 too. So adjust your subwoofer to output around 73-74 dB on the CM-140 when using your receiver as the source. With DVE it's much more difficult to define the correct compensation but around 2 dB is a good starting point. Your ears should always be the final judge, don't just blindly trust on the SPL meter. If the subwoofer sounds too loud, turn it down.

**Vader** · **03-16-07, 08:14 PM**

Ilkka,

So you would recommend that I use the AVR's TT instead of DVE? I had always heard that DVE was the better way to go because it tests the entire signal path (from DVD player --> AVR to Speakers --> SPL meter). What you say makes perfect sense too. What about the other channels? Would it be better to simply calibrate all of them to keep consistancy, or use DVE for everything except the LFE channel? I know, I need to get AVIA.... just haven't gotten around to it yet.

**Ilkka** · **03-16-07, 08:22 PM**

Quote:

Vader wrote:

Ilkka,

So you would recommend that I use the AVR's TT instead of DVE? I had always heard that DVE was the better way to go because it tests the entire signal path (from DVD player --> AVR to Speakers --> SPL meter). What you say makes perfect sense too. What about the other channels? Would it be better to simply calibrate all of them to keep consistancy, or use DVE for everything except the LFE channel? I know, I need to get AVIA.... just haven't gotten around to it yet.

The signal path doesn't really matter at all in this case. I would use the AVR's test tones instead of DVE for all channels.

**Sonnie** · **03-16-07, 09:05 PM**

Ilkka, you can still have quite a variance in response from 40Hz to 80Hz, so how do you account for it? I realize the CM-140 is pretty accurate in that range, other than maybe reading a db or so low on C-Weighting, which on an SPL meter 1db is pretty hard to adjust for, but on those who still have RS meters, that could be anywhere from 1db to 4db, with the C-Weighting reading low... 2db to 5db from 80-40Hz respectively.

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