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Old 10th January 2012, 10:05 AM   #1
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Default RTA mic for subs and 20hz

I have heard that most of the cheaper rta mic
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Old 10th January 2012, 11:01 AM   #2
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what I meant was, I have heard that most of the cheaper rta mic's dont do very well at 20hz and are not consistent. Can anyone recommend an RTA mic for subwoofers?

Cheap is good but only if its good enough.

thanks,
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Old 10th January 2012, 03:14 PM   #3
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Originally Posted by reminence View Post
what I meant was, I have heard that most of the cheaper rta mic's dont do very well at 20hz and are not consistent. Can anyone recommend an RTA mic for subwoofers?

Cheap is good but only if its good enough.

thanks,
The SIA RTA-420 is a good cheap mic, I bought one used from Harry Brill of Tiger Audio,he sells them new too. Unit to unit variation is always a problem, even for expensive mics, but the RTA-420 is certainly good for the price.
The same element is used on several other test mics costing more than the RTA-420.
I have a pair of very expensive test mics, B&K 4004, some info about the RTA-420 compared here:

PSW Sound Reinforcement Forums: LAB: The Classic Live Audio Board => Testing the Test Microphone

The picture below shows the RTA-420 is 4 dB down at 16 Hz from the 4004s, the test source obviously is not flat, but both mics were placed as close as possible to the same position.
The B&K 4004 came with an individual test sheets, they are (were) +/- 2dB from 10 Hz -40 KHZ.

The B&Ks have hardly left the mic locker since getting the RTA-420, if I have a speaker that produces anything much below 30 Hz I can just refer to the comparison and add a few dB appropriately.

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Old 10th January 2012, 03:37 PM   #4
jbell is offline jbell  United States
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Lilmike's Mic - AVS Forum

lilmike's solution is relatively flat, and CHEAP !!
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Old 11th January 2012, 12:39 AM   #5
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Lilmike's Mic - AVS Forum

lilmike's solution is relatively flat, and CHEAP !!
Back in the winter of 1999 I built some microphones like lilmike., housed them in male XLR shells.

I first used an electret mic element from a telephone, I was amazed that it had far flatter response than I expected.

Then I ordered several Panasonic elements, the pair of WM62 and a phone unit are compared to the RTA-420 below.

The phone unit has a midrange boost and HF rolloff.

One of the WM62 A has a reduced LF, even though the upper response matches the RTA-420 pretty well, and seems to be picking up 60Hz and harmonics.

Funny, just dug them out of the mic closet the other day, your post made me curious to test the response out. The 9V batteries were all pretty low after 13 years of storage...

Anybody wanting some cheap test mics can PM me :^).

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Old 11th January 2012, 03:42 AM   #6
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I ended up just going with a dbx RTA-M which is said to be very similar to the discontinued SIA RTA-420.

I went with this since I live in aus its fairly available here and I am not good at making electronics nor would I trust myself making an rta mic.
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Old 11th January 2012, 06:02 AM   #7
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If you had a spare 700USD laying around you could have bought a Term-LAB measurement system. It uses a pressure sensor instead of a microphone.

http://www.termpro.com/storefront/page605.html
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Old 11th January 2012, 09:03 AM   #8
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haha, yes, that's cheap lol. but maybe doable when I do gigs for more than a thousand people
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Old 11th January 2012, 09:45 PM   #9
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Originally Posted by reminence View Post
I ended up just going with a dbx RTA-M which is said to be very similar to the discontinued SIA RTA-420.

I went with this since I live in aus its fairly available here and I am not good at making electronics nor would I trust myself making an rta mic.
Good choice.
I suspect most of these cheaper mics probably use the same elements anyway, the (working) Panasonic WM62 is almost a direct overlay of the SIA RTA-420.
I have a DOD RTA mic that measures about the same too.

Considering how drastically measurements vary with position, spending more than $100 or so on test mics is hardly warranted unless you are getting paid big money for the measurements.
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Old 14th January 2012, 05:57 AM   #10
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Yeah, I suspected I would be much better off with this than something the likes of behringer...
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