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Author Topic: Measurement Microphones  (Read 86711 times)

Dave Barnett

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Re: Measurement Microphones
« Reply #50 on: December 24, 2008, 11:40:59 am »

Tom Young wrote on Tue, 23 December 2008 06:35

"So as much as I love to use Beringer as a punch line I will have to hold back some times and go with my old standby: Bose."

I actually tried their measurement mic. If you ignore the phase response that results from the 4 front-aimed capsules and the one rear-aimed capsule.... they are not that bad. But make sure you use their preamp or the frequency response will be restricted to 160Hz-7kHz.

 Twisted Evil  


Now that's comedy.
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Dave Barnett

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Re: Measurement Microphones
« Reply #51 on: December 24, 2008, 11:49:55 am »

Kent Clasen wrote on Wed, 24 December 2008 09:14

While I haven't compared mics myself, I use the Audix TR40 and have a handful of the Superlux for multi mic measurement, where I am mostly looking at relative changes in different areas.

An interesting note, I don't know if it was already discussed, I didn't read every post. Pat Brown compared measurement mics in his VOL36 Aug 08 newsletter.  He found the angle of incidence to have a major impact on the mics.  He lists several mics and the recommended angle.

He found a 10dB frequency response deviation using the same angle on every mic, but when using the proper incidence angle, only 2dB diff!

Some angles where 0, 45, and 90 degrees depending on which microphone you are using. DPA, Earthworks, Soundfirst were some he tested.


I guess they're not truly omnidirectional then?
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Too Tall (Curtis H. List)

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Re: Measurement Microphones
« Reply #52 on: December 24, 2008, 01:15:55 pm »

Bob McCarthy wrote on Mon, 22 December 2008 16:26

I own 8 Earthwoks M30s. They are sufficient for my needs, although I probably would have bought DPA 4090 series mics had they been on the market at the time I bought mine. They are now 5 years old. 2 of them will go back for rework shortly. They drift in level over time and as a result I calibrate them at every job. I never do any work with a single mic so for me relative level and freq response are more critical parameters than absolute freq response.

As for the earlier question re the B&K calibrator - it SHOULD work with the M30 adaptor. Calibrators are made to a standard and different mics have a specific adaptor mechanism to fit that.

Finally, at a recent SIM school in Germany a guy pulled out his Beringer mic and we compared it to the DPA 4007 using a dual mic transfer function. Everyone was prepared for a big laugh but the 25 cent mic did very well (this is the second time I have seen this so I was not too shocked.) So as much as I love to use Beringer as a punch line I will have to hold back some times and go with my old standby: Bose.


A point of interest on the Behringer.

I use a 2-conductor unbalanced microphone made by Kim Giardin.
It works with the built in mic preamp in the Praxis Audpod (Interface).

The mic is a 9/32" tube with the capsule in one end.

index.php/fa/19839/0/

NOTE: On the other end of the pipe is a female RCA. Kim makes a 9/32" brass tube that is about 36" long as an extension. With the 11" mic reaches almost 4 feet to get away from mic stand reflections)

The mic cable can be no more then 30' and 25' is better or the top end rolls off.

The mic is calibrated for both freqency SPL and phase to a Top line ACO mic for hundreds of points and can be imported into several programs, including Praxis.

I asked Kim to come up with a way to make his mic balanced low impedance so I could use it over long distances.

Rather then buy the transformer/electronics or other pieces he suggested that gutting a Behringer to use everything except the capsule would be the cheapest for parts and labor.

When he started working on it he found that there is an active EQ filter built into its circuit board.

He made it work anyway (including calibration), but decided he would NEVER do that again.

Long story short, do we know of any other microphones that do this?
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Too Tall
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Tom Young

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Re: Measurement Microphones
« Reply #53 on: December 24, 2008, 10:46:59 pm »

"I guess they're not truly omnidirectional then"

Absolutely not. No mic is.

How does a mic remain omnidirectional when the mic (diaphragm) is turned to the point that direct sound does not strike it or even move it at higher frequencies where diffraction cannot occur ?

But the better designed and more expensive mic's have more even off-axis response, which is very audible in listening (when you use them for recording or sound reinforcement) and obviously has an effect when used for measurements.

If microphones (any and all) were measured and the data was provided to us at/with the level of detail that most professional loudspeakers are ..... I think we'd all be a bit surprised and possibly dismayed.
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Tom Young
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Mac Kerr

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Dinner conversation
« Reply #54 on: December 24, 2008, 10:56:25 pm »

Tom Young wrote on Wed, 24 December 2008 22:46

"I guess they're not truly omnidirectional then"

Absolutely not. No mic is.

How does a mic remain omnidirectional when the mic (diaphragm) is turned to the point that direct sound does not strike it or even move it at higher frequencies where diffraction cannot occur ?

But the better designed and more expensive mic's have more even off-axis response, which is very audible in listening (when you use them for recording or sound reinforcement) and obviously has an effect when used for measurements.

If microphones (any and all) were measured and the data was provided to us at/with the level of detail that most professional loudspeakers are ..... I think we'd all be a bit surprised and possibly dismayed.

Hmmm... Tom, didn't we just have this conversation at dinner the other night? It's interesting that your point about balloon plots for mics came up here so soon.

Mac
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Tom Young

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Re: Dinner conversation
« Reply #55 on: December 25, 2008, 07:55:58 am »

What can I say ?

It was fortuitous that this subject came up befor I forgot this aspect of the subject  Wink

Time for some eggnog for breakfast........

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Tom Young
Electroacoustic Design Services
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Email: dbspl@earthlink.net
www.dbspl.com

Adam Robinson

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Re: Matching Microphones, or not...
« Reply #56 on: December 25, 2008, 01:43:38 pm »

Mac Kerr wrote on Mon, 22 December 2008 14:19

Adam Robinson wrote on Mon, 22 December 2008 14:53

I own a TR40 and when I tested it against others, I did not have the same result.


Against what others? All mics will vary slightly, even 2 brand new mics of the same type. I did this test because I found that with 3 different speaker systems, dv-DOSC mains, VRX932 delays, and 108P front fills I was making very similar eq changes. I asked for the other mics to check to see if there was an issue with my measurement mic. While it is down in level it is not grossly different from the other Earthworks, so I remain fairly confident in its output. As I said, I will still get it checked at the factory, but I don't feel the differences in the 2 mics greatly effected the alignment of my system. Final tweaking was done by walking and listening to the transitions between zones and the overall coverage of the room.

Mac


Sorry for being late on the response.  I meant in my reply above that when I tested my TR40, I found it to not have that 6db (avg) boost against other mics in my test,  like your picture showed.  All of the responses were decently close to each other.

FWIW, a while back, I did have one go wonky on me.  I sent it back to Audix and they were happy to repair it.  
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Brad Weber

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Re: Measurement Microphones
« Reply #57 on: December 30, 2008, 09:24:45 am »

Bennett Prescott wrote on Wed, 17 December 2008 17:59

I see he now offers the SF-111, which is even better for less than twice the money!

Just got a SF111 from Ray a couple of weeks ago along with an "unlocked" SP395 for field survey use.  The SF111 will now be the reference for the Earthworks M30S mics I usually use on site.
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Brad Weber
muse Audio Video

Tom Young

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Re: Measurement Microphones
« Reply #58 on: December 30, 2008, 10:58:49 am »

Me, too.

I already had a SF101 and recently bought the SP395 from Ray.

Please let me know what you find it takes to get your SP395 to talk to your PC (Terralink).
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Tom Young
Electroacoustic Design Services
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Email: dbspl@earthlink.net
www.dbspl.com

Christopher Wintz

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Re: Measurement Microphones
« Reply #59 on: January 01, 2009, 06:29:01 pm »

Not to beat a dead horse, but I have more questions about measurement mics.

I picked up a Beyerdynamic MM1 the other day.  Not the greatest mic on the market, but it was well within my price range and it looks like it will be a good performer.

In the spec booklet it mentions an energy build up that can accour in front of the mic at 10+KHz, if the make is facing directly towards the source, thus throwing off the frequancy response and creating some phase issues.  Which makes sense as the wavelangth would then be smaller then the diameter of the mic.

Two questions:
Are all mics susceptible to this? (And that all measurement mics should be perpendicular to the source during measurement...)
How would you compensate for this while using a mic calibrator, do you need to?
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ProSoundWeb Community

Re: Measurement Microphones
« Reply #59 on: January 01, 2009, 06:29:01 pm »


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