Looking for mic suggestions to dip into REW. Are precalibrated worth the prem? - AVS Forum
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post #1 of 23 Old 08-16-2014, 10:31 AM - Thread Starter
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Looking for mic suggestions to dip into REW. Are precalibrated worth the prem?

As the title states, I think I want to finally take my setup to the next level and tune everything. It started with my DIY sub setup I am working on and got a DSP in my AMP. I noticed today that my Denon 1912 actually does have calibration settings for diff freq ranges, so I figured now is as good a time as any to play with this and try to learn more.

Now Originally I was looking at ordering A Dayton UMM-6, but then someone in another forum mentioned getting an SPL meter too which confused me. I thought this would take place of an SPL meter also and measure within the rew app?
Then I started reading more about getting pre calibrated UMIK's and UMM-6's from a calibration place ( i forget the name off the top of my head) and they were more accurate than the calibrations given by MiniDSP and Dayton in their config files?

Can anyone help me to determine if the calibrated by a service is really needed? Or can i spend $60 on a Dayton and be ok?

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post #2 of 23 Old 08-16-2014, 11:09 AM
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Here's what the included calibration files look like a group of UMIK-1's, the direct or on-axis or 0 degree calibration





How much accuracy you desire sends you to secondary calibration, where you get a curve for 0, 45, and 90 degrees (or other angles) - Cross Spectrum was the name of one calibrator for the UMIK.

The files look something like these curves:



The difference is mainly way up high. Your room problems are generally way down low.

Do you want a calibrated measurement mic - yes, I did. I bought a UMIK-1.

Do you want additional calibrations for different mic angles - I didn't.


Here's the data from the calibration file (text) for my mic plotted in excel:


I'll be back later...


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post #3 of 23 Old 08-16-2014, 12:26 PM - Thread Starter
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I guess I am confused what this means. Are the stock umiks and umms not calibrated? Or not calibrated as well as spectrum would since they do specially for that mic and not a batch of mics?

I will need laymans speak for this as this is very new to me
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post #4 of 23 Old 08-16-2014, 01:10 PM
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Calibration just means that a microphone is tested against a standard and a calibration (correction) file is created for that specific microphone, to "correct" the microphone error when it is read into some measurement software like REW..

There may be some terribly expensive microphones where the hardware itself is "calibrated", but we aren't talking about them.

You take a measurement with something like REW, and it refers to the file to "correct" the response of the microphone.

The file has frequencies and corrective level changes like this:

Code:
"Sens Factor =-1.214dB, SERNO: 7004591"	
10.054	  -5.9051 
10.179	  -5.7374 
10.306	  -5.5730 
10.434	  -5.4117 
10.564	  -5.2536 
10.696	  -5.0987 
10.829	  -4.9468 
10.964	  -4.7980 
11.1	  -4.6522 
11.238	  -4.5095 
.. and on and on up to the top of the range...
18356.24	  1.2021 
18584.752	  1.1897 
18816.107	  1.1765 
19050.346	  1.1625 
19287.498	  1.1481 
19527.604	  1.1331 
19770.697	  1.1170 
20016.816	  1.1005
Cross-Spectrum does a calibration at 3 different angles, and maybe they are more exact, who knows. They charge a premium of $20, can't be too painstaking.

Anyway, they don't do anything to the mic itself, just read it, and give you a correction file.

If they are doing their job correctly, they DO individually test each microphone and create a unique file for it. Note "Serial Number" in my file example.

I'll be back later...


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post #5 of 23 Old 08-16-2014, 01:28 PM - Thread Starter
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So do you feel paying their premium over a stock umik or umm is really necessary?
Or do most run the cal files from the manufacturer and fine this sufficient?

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post #6 of 23 Old 08-16-2014, 01:35 PM
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I bought the basic UMIK-1 from miniDSP themselves.

$75 + $20 two day shipping from HongKong to USA.

I read the Cross Spectrum site, they do 0, 45, and 90 degree calibrations - the angle of the microphone to the source being measured.

I decided that the 0 degree file ( point the microphone at the source) as included with the UMIK-1 from the factory was sufficient for my purposes (2 channel).

You will find that the problems in your room far outweigh any tiny calibration differences you might find between two competent calibrators.

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post #7 of 23 Old 08-17-2014, 07:35 AM - Thread Starter
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Is HDMI neccesary for using REW? I assume this is to run test tones through the system?
None of my laptops nor desktops have HDMI out. Any other options?

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post #8 of 23 Old 08-17-2014, 07:43 AM
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REW generates it own tones.

The main test tone is a quick logarithmic sweep.

You can send it to your system with whatever output you have available.

I use it in 2 channel mode, via Optical or USB output.

If you are using it for multichannel, I don't have an answer to that.

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post #9 of 23 Old 08-17-2014, 07:44 AM
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Quote:
Originally Posted by PM-Performance View Post
Is HDMI neccesary for using REW? I assume this is to run test tones through the system?
None of my laptops nor desktops have HDMI out. Any other options?
Not at all. HDMI provides some convenience in testing speakers in a multi-channel environment but that is only possible if you can get it to work which is a challenge in itself. In stereo testing this of course does not apply at all.

I think everyone needs to get started with REW by simply using the analog out from the laptop. That always works and will get you as far as you need to get in this topic.

As for calibration, Ray is right. You don't need to spend the extra money. The mic already comes with a calibration file that gets you close. The difference is not material in analyzing room response because you need use your ears for balance of high frequency to low as opposed to shooting for a flat line.

Also, volume calibration is not necessary either even though REW insists on it. You are looking for before and after frequency response variations. Not any kind of absolute performance.

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post #10 of 23 Old 08-17-2014, 07:58 AM
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UMIK-1 with REW

Latest beta version of REW "knows" about UMIK-1.

REW asks if you have a calibration file and if you do, disables any further calibration. The Calibrate button on the REW SPL meter becomes ineffective.



The Windows Record Level for the UMIK-1 should be set to 25.

This gets you real close to the values a standalone SPL meter shows when compared to the SPL meter in REW. If you do want to get it closer to an external meter, adjust the level in the Sound Manager - Recording tab for UMIK-1


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post #11 of 23 Old 08-17-2014, 08:02 AM
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I have a few questions.

I have a onkyo 818 with xt32 for calibration.

Once you get started into REW are the adjustments mostly made by moving the actual speakers? My speakers are pretty much in place and cannot be moved.
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post #12 of 23 Old 08-17-2014, 08:12 AM
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REW does measurements.

It is up to you to figure out a way to make a modification to your system, and measure again to see what good or harm you did.

That could include inputting data to some device in your rig, moving speakers, or applying room treatments.

I'll be back later...


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post #13 of 23 Old 08-17-2014, 08:19 AM
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Ok that's what I sort of thought. Appreciate the help
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post #14 of 23 Old 08-17-2014, 08:26 AM
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Quote:
Originally Posted by Holiday121 View Post
I have a few questions.

I have a onkyo 818 with xt32 for calibration.

Once you get started into REW are the adjustments mostly made by moving the actual speakers? My speakers are pretty much in place and cannot be moved.
Ideally you'll use REW with something like a BFD (Behringer Frequency Destroyer), which will implement the corrections REW suggests. Otherwise, you are limited to either using any controls in the preamp or receiver, or moving speakers around.

Personally, I'd use REW by itself for corrections only if I didn't have Audyssey or another room-correction solution. XT32 has better resolution at the frequencies your sub covers and measures from multiple points in the listening area, while REW measures at the main listening position only. REW, however, can give you a graphic plot of your sub's in-room response, while the consumer levels of Audyssey do not. It also has an RTA function which can come in very handy.

Having said this, I have used REW and a BFD in conjunction with the Audyssey (non XT32) in my Onkyo receiver. REW and the BFD were used to match my two subs as closely as possible before beginning the Audyssey calibration, and I'm happy with the results.

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post #15 of 23 Old 08-17-2014, 08:35 AM
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Back to the original question:

Quote:
Originally Posted by PM-Performance View Post
As the title states, I think I want to finally take my setup to the next level and tune everything. It started with my DIY sub setup I am working on and got a DSP in my AMP. I noticed today that my Denon 1912 actually does have calibration settings for diff freq ranges, so I figured now is as good a time as any to play with this and try to learn more.
Now is a good time to start.

Quote:
Originally Posted by PM-Performance
Now Originally I was looking at ordering A Dayton UMM-6, but then someone in another forum mentioned getting an SPL meter too which confused me. I thought this would take place of an SPL meter also and measure within the rew app?
REW includes an SPL function. The calibration file that comes with the Dayton is probably enough to satisfy REW, but I don't have experience with that mic to say for sure.

Quote:
Originally Posted by PM-Performance
Then I started reading more about getting pre calibrated UMIK's and UMM-6's from a calibration place ( i forget the name off the top of my head) and they were more accurate than the calibrations given by MiniDSP and Dayton in their config files?
The unique calibration file that can be downloaded for the mic is probably "good enough".

Quote:
Originally Posted by PM-Performance
Can anyone help me to determine if the calibrated by a service is really needed? Or can i spend $60 on a Dayton and be ok?
You can probably be "ok" with the manufacturer supplied calibration file.

As Amirm mentioned, you are more interested in relative measurements than absolutes. Relative - meaning look at the curves for high places and dropouts.

If you do have a chance to use an external SPL meter, you can then check if the levels match between REW and the meter - expect a couple of dB difference. If concerned you can adjust the gain of the mic in windows or REW (if it doesn't block adjustment due to having a calibration file to read)

I'll be back later...


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post #16 of 23 Old 08-17-2014, 10:03 AM
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Quote:
Originally Posted by PM-Performance View Post
So do you feel paying their premium over a stock umik or umm is really necessary?
Or do most run the cal files from the manufacturer and fine this sufficient?
depends on how accurate you think you need to be. The capsules (vibrating part of the mic) are not consistent enough for a generic calibration file to be accurate for every specific mic of a particular make and model. Heck, even expensive (multikilobuck) recording mics (which are not necessarily anything like flat) exhibit enough sample-to-sample difference that it's worth paying to have a pair specifically matched to each other so that weird unintended panning things don't happen when they are used as a stereo pair. Like so the ride cymbal doesn't move two feet to the right when the drummer plays on the bell instead of the body of the cymbal.

IDK if there are significant tests of these sixtyish dollar or hundred dollar omni condensers to tell us the sample to sample differences we're likely to see. Last time I was researching them (ended up not buying any) many seemed to be the same Chinese capsule (nothing inherently wrong with that) in similar or identical bodies with different manufacturer names. Nothing inherently wrong with that, either. But the retail cost of a mic developed specifically for measuring and has reasonably consistent response from sample to sample is in the $500 to 1000 range (I am thinking of Earthworks).

We sort of know that he inexpensive mics that Audyssey's systems use (short of the pro system) have differences of up to plus or minus 2 dB from each other, because Audyssey tells us so. We also know, IIRC, that Audyssey tests the mics they receive, and throws out a bunch that aren't within that four dB window.

If I were going to step my lazy butt up to do REW, I'd probably want an individually calibrated mic, just so I'd know . . . . Because if I'm being picky, I'm being all the way picky . . . . But that's just me.
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post #17 of 23 Old 08-18-2014, 08:09 AM - Thread Starter
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Well it deff makes sense to get the UMIK from Crossspectrum than Minidsp themselves as they charge quite a bit of shipping. Price difference from Cross Spectrum is only about $5
Now do I need a seperate mic stand with boom? Or do you guys just sit the OEM supplied tripod on one of your seats?
If a boom is needed, I would probably rather start with the UMM to see how it goes as adding those parts and free shipping still yeilds to be cheaper.

Also looks like both measure to 18-20 hz. So nothing below that will be measured? How do you guys get around this for subs that will still produce well below these points? My boxes are tuned to like 14hz.

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post #18 of 23 Old 08-18-2014, 08:38 AM
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Quote:
Originally Posted by PM-Performance View Post
Well it deff makes sense to get the UMIK from Crossspectrum than Minidsp themselves as they charge quite a bit of shipping. Price difference from Cross Spectrum is only about $5
Now do I need a seperate mic stand with boom? Or do you guys just sit the OEM supplied tripod on one of your seats?
If a boom is needed, I would probably rather start with the UMM to see how it goes as adding those parts and free shipping still yeilds to be cheaper.

Also looks like both measure to 18-20 hz. So nothing below that will be measured? How do you guys get around this for subs that will still produce well below these points? My boxes are tuned to like 14hz.
You want the mic away from reflective surfaces... I have mine on a little desk stand that puts it at ear position on the couch.

The calibration files go lower, Cross Spectrum takes it from 5Hz-25kHz

You're right about the price difference, I didn't stare long enough.

I'll be back later...


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post #19 of 23 Old 08-18-2014, 08:39 AM - Thread Starter
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hmmmm, this stuff adds up quick. lol
Ok, so add a boom in there and bracket for the mic then too.
Obviously, if your subs are tuned to go lower than that 18hz, it serves a true benefit to get the calibrated one then?

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post #20 of 23 Old 08-18-2014, 08:41 AM
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Quote:
Originally Posted by PM-Performance View Post
hmmmm, this stuff adds up quick. lol
Ok, so add a boom in there and bracket for the mic then too.
Obviously, if your subs are tuned to go lower than that 18hz, it serves a true benefit to get the calibrated one then?
Tape the mic to a broomstick...

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post #21 of 23 Old 08-18-2014, 08:55 AM - Thread Starter
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I have a camera tripod I use for my Audessy mic, but not sure how I would attach this mic to it. I guess I could fabricate something up in a ghetto manner. lol

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post #22 of 23 Old 08-18-2014, 10:31 AM
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Quote:
Originally Posted by RayDunzl View Post
Tape the mic to a broomstick...
And fly! Fly, my pretties.

Sorry couldn't help myself.
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post #23 of 23 Old 08-18-2014, 02:54 PM
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Mic boom is def the way to go. If you use a tripod you inevitably must place one leg on the seat, which will transmit vibrations to the mic. You can get one for around $20 that will do the job. Makes your Audyssey calibrations more accurate as well.

The main difference between the calibrated UMIK-1 and UMM-6 is that the UMIK-1 comes with a sensitivity factor in the calibration file. Without the sensitivity factor you have to "calibrate" the SPL (with a separate SPL meter) each and every time you run REW (makes it a whole lot easier to compare graphs from different sessions).

That being said, you can generate your own sensitivity factor for the UMM-6, although personally I don't trust it....I "calibrate" the SPL each and every time.
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