RS Digital SPL Meter correction values

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SoCalWJS

RS Digital SPL Meter correction values
« on: 2 Feb 2012, 06:15 pm »
I am trying to do some measurements using a Radio Shack Digital SPL Meter to get some values in order to assist me in determining speaker placement. I used the Alan Parsons Soundcheck2 CD as the source for the levels. After doing so, was getting ready to either pitch my speakers, the meter, or commit Hari-kari (maybe all of them).

I then remembered that the RS meter has some issues with regards to accuracy (it's been awhile since I've done this). Googled and found a bunch of correction values, all generally within a few db of each other, however, they are mostly for the older analog meter.

So, 2 questions:
1) Are the Analog and Digital versions of this meter roughly the same (i.e., can I use correction values for the Analog meter for my Digital meter)?; and
2) Is there a concensus on the correction values to use? I got my numbers from this site,and it seems roughly the same as several others.

http://diyaudioprojects.com/Testeq/RadioShack_33-2050/33-2050.htm

Thanks.

Speedskater

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Re: RS Digital SPL Meter correction values
« Reply #1 on: 2 Feb 2012, 08:53 pm »
They have been making those Radio Shack Digital SPL Meter's for decades!  Probably in several different factories with components sourced from many places.  So don't expect much consistency from batch to batch.
This is an SPL meter not a frequency response meter.  I checked mine on a pro SPL tester and it was surprisingly close.
For frequency response measurements there are other better budget meters.
Don't put much stock in any of those amateur correction curves for the meters measured and even less when transferred to your meter.

Phil A

Re: RS Digital SPL Meter correction values
« Reply #2 on: 2 Feb 2012, 10:25 pm »
Rives Audio sells a test disc for $21 that supposedly compensates for the microphone in the RS meter.

Rob Babcock

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Re: RS Digital SPL Meter correction values
« Reply #3 on: 2 Feb 2012, 10:51 pm »
FWIW, I think the Rives disc is pretty close.

cheap-Jack

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Re: RS Digital SPL Meter correction values
« Reply #4 on: 2 Feb 2012, 10:58 pm »
Hi.
I am trying to do some measurements using a Radio Shack Digital SPL Meter....
http://diyaudioprojects.com/Testeq/RadioShack_33-2050/33-2050.htm

I have been using RS 33-2055 SLM for many years. 3055 is a higer digital version of 3050 with on-scree digital readouts for all functions, from slow/fast response. peak/average readout, A/C weighting etc etc. I don't think there is any need of 2055 readout corrections.

Pretty handy. Frankly I use it casually to test the peak SPL of my music.

For testing loudspeakers response, you may need a signal generator to generate pink noise signals rather pure sinewave signals to avoid standing waves due to the interior acoustsics.

c-J


Ethan Winer

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Re: RS Digital SPL Meter correction values
« Reply #5 on: 3 Feb 2012, 05:00 pm »
This is an SPL meter not a frequency response meter.

Yes, exactly. Though the low frequency response is adequate for optimizing speaker position and assessing improvements after adding bass traps etc. This article compares two different RS meters with a number of microphones ranging from dirt cheap to very expensive:

Comparison of Ten Measuring Microphones

In the end, the only way to know which speaker placements are best is to measure the LF response at high resolution using appropriate software:

Room Measuring Primer

Typical test tone CDs are not useful because they contain sine waves at only third-octave intervals, which completely hides the true response.

--Ethan

SoCalWJS

Re: RS Digital SPL Meter correction values
« Reply #6 on: 5 Feb 2012, 04:58 pm »
Thanks for all the responses. I know that the RS meters have serious shortcomings, but wanted to use the one I had to try to get an idea of where I'm starting from before I get serious about room treatments. After 2 days of sliding my speakers around, I got a flatter response curve than where I started at. It's weird though - I was fairly happy with the sound of the speakers initially. Went back the next day and it seems as the mid-bass has become somewhat boomy. Ah well....

First round of OC703 2" scheduled to arrive on Friday.

If I get serious, I'll have to figure out how to get REW running. Seems it's getting tougher to find a combination of computer OS/soundcard/microphone that work well together.

May take a look at the Omnimic setup if I can find it at a better price (Parts Express seems to be out of stock).

Thanks again!