REW vs OmniMic

[Chuck Gerlach]

I have been using OmniMic for 10 years or longer but needed to validate its perfrormance on my LFE channel. So I used REW. From the two plots below, the results between about 20Hz and 100Hz are close enough. But south of there, huge difference. How accurate is REW south of 20Hz?. I have had the miniDSP mic for a very long time but never used it and I did download the cal file.

 

[Wayne A. Pflughaupt]

Hard to say with what you gave us to go on. One can’t make a valid argument for or against either platform without knowing if the measurements were taken with the same mic and calibration file.

Regards,
Wayne A. Pflughaupt

 

[Chuck Gerlach]

OmniMic uses it own mic and the associated cal file just like REW uses a miniDSP mic and associated cal file. I would have expceted some minor differences but not like what I got. What I would like to know is if I could use my much more expensive ($900) mic and associated cal file into a USB mic preamp into REW. ?.

 

[Wayne A. Pflughaupt]

Why do you assume the issue is with REW, and not the miniDSP mic and / or its calibration file? And, why do you assume OmniMiic is the one that’s accurate?

Again, both platforms will require a measurement from the same mic and calibration file. Without that we can only guess about the discrepancy.

Regards,
Wayne

 

[Chuck Gerlach]

I’m not sure where I implied either was right or wrong. I have no way of knowing. I know I can’t use the REW mic on OmniMic and I don’t know if I can use the OmniMic mic on REW. If I can, I will give that a go. assuming the cal file can be put into the correct format!

 

[Kal Rubinson]

I’m not sure where I implied either was right or wrong. I have no way of knowing. I know I can’t use the REW mic on OmniMic and I don’t know if I can use the OmniMic mic on REW. If I can, I will give that a go. assuming the cal file can be put into the correct format!

I use my OmniMic mic and my XTZPro mic, as well as the UMIK-1, on REW. If you want to compare softwares, use the same mic on both.

 

[Chuck Gerlach]

Thanks Kal. I will give that a try. Should prove interesting. Do you get identical (or at least similar) results on REW using each of those mics?

 

[Kal Rubinson]

Thanks Kal. I will give that a try. Should prove interesting. Do you get identical (or at least similar) results on REW using each of those mics?

I have not done the testing.

 

[DanDan]

Both look the same at 20Hz, one drops about 5dB by 10Hz. I wouldn't sweat subsonic stuff. Be sure that REW is not set to C Weighting. Best not use Cal files when comparing.

 

[Chuck Gerlach]

I do sweat the subsonic stuff since (a) I paid good money for it and (b) I would like to know which one is correct so I can account for it. The OmniMicplot shows I’m down 5dB at 7Hz while the REW plot shows I’m down about 8 or 9 dB more. Also could be that neither of them are correct!!

Question: why not use cal files?

 

[DanDan]

Good money? I remember that..... I guess you are trying to figure out if the Omnimic app or REW is telling the truth. Omitting the Cal files removes a layer of possible confusion.
Can you look at both Cal files and see if they are different down there? I reckon these are auto factory jobs, not lab quality, manual.
I use these very very cheap (relatively) mics for relative measurement. Brilliant for out and about, rain, nightclubs...... But if I really want to know, I pull out the serious big guns. DPA or B&K. They state the full spectrum spec, and I always see it holds water. I had a chat with Dirac Live's Mathias about the influence of mic quality. He reckons, personally and with client feedback, that the 'real' mics, with better phase and other behaviour, do a better job.

 

[Chuck Gerlach]

I have an expensive Earthworks mic (and cal file) I will try to use with a mic preamp into REW. The variance of the Earthworks mic is tiny parts of a dB without the cal file. That will at least be another data point!!!

 

[DanDan]

I think Rolls Royce had a motto..... Nobody regrets buying the best...

 

[Chuck Gerlach]

I think Rolls Royce had a motto..... Nobody regrets buying the best...

“Except when they do”

 

[Chuck Gerlach]

I took a look at the cal file I downloaded for my miniDSP mic and noticed there were NO correction values below 20Hz. That would most certainly explain why my LFE plot took a nose dive in that region. Is that typical for one of those cal files or is there another place I might obtain one that go further down the spectrum?

 

[DanDan]

Maybe JohnPM will join in. I can tell you this, I tested two UMIKs here, different years. Both were 1.8dB off compared to my B&K2250, which is Calibrated.
I just rewrote the Sens line in the Cal file, either added or subtracted 1.8dB. Worked fine.
I don't know how many data points would be needed, but I guess it may be possible to eyeball the Omnimic response and manually write in a few?

 

[Chuck Gerlach]

I could do that easily but that assumes the OmniMic is still operating properly. I went on-line to buy a new mic with cal file to 10Hz and no matter where I went, they are all out of stock!!

 

[Chuck Gerlach]

I am continuing to try to get the LFE measurements to be correct south of 20Hz. I created a new cal file with adjustments to fix it but when I run a sweep with both the original cal file and my modified one, the results are identical. Clearly I am doing something wrong but I'm not sure what it is. I am attaching the two cal files: one labeled "Original" which has no adjustments below 20Hz and the other labeled "Sub20" which does have the adjustments. Any suggestion would be helpful.

Also, is there a "REW on a Mac User Guide" Video that can walk me through all of the ways to use it, variables, optoins, etc?

 

[John Mulcahy]

The extra values in your cal file are the wrong sign, the cal file response should mimic the response of the mic and go down at low frequencies, not up.

Not a video, but this thread covers mac setup well.

 

[Chuck Gerlach]

I'm a bit confused on the sign. The original file has nothing below 20Hz and the plotted response drops off dramatically below 20Hz. So I (apparently incorrectly) assumed that I needed to use plus values to force the plotted response in the right direction.

And thank you for the link. I will check it out.

Off topic. Had you authored some other similar measuring software with a different name prior to developing REW? A gazillion years ago, I used some PC software for measuring and your name sounds so familiar.

 

[John Mulcahy]

No other measurement software from me, but REW has been around since 2004.