New RS SPL Meter Corrections are posted...

[Sonnie]

We wanted all members to be aware that we have posted new RS SPL Meter Correction Values on the Downloads page here at the Shack. The new values are from 7Hz to 200Hz. These new calibration files were calculated based on a comparison to my ECM8000 mic that has been calibrated and certified by West Caldwell Calibration Laboratories. We believe these will be the most accurate corrections available, short of having your RS SPL meter professionally calibrated.

We have also created new Excel Workbooks for those that may be interested. The workbooks include new graph axis from 7Hz to 200Hz. These are also available from the Downloads page.

Special thanks to brucek for all his work on this...

[krunk]

Super!

Bart

[gyusher]

I know I'm slow but are you saying to deduct or add those values to the meter reading we are getting. . .An example is at 20Hz you show -10 or whatever the actual number is. .Can't remember. . .What I see is if (say) you have your meter set on 80Hz and your SPL is reading 80Hz do you deduct from your meter reading for the actual SPL at that frequency if your correction numbers show a minus??

What I'm trying to do is get a quick and dirty reading when setting up my room. . .Just curious if you would set that 20Hz level higher or lower on the RS meter reading. . .

Maybe I need to go to bed. . .I know I'm smarter than I appear right now. . .

I always knew those meters were 'off' at the lower frequencys but never knew how to compensate for it. . .

[brucek]

are you saying to deduct or add those values to the meter reading we are getting

Those numbers show the deficiency at a specific frequency, so you add them to the needle reading.

brucek

[gyusher]

brucek wrote:

Those numbers show the deficiency at a specific frequency, so you add them to the needle reading.

brucek

Thanks for that. . .I was about to go nuts trying to ask that question. . .

Happy Easter. . .

[Exocer]

This calibration file made a huge difference to my measurements...a driver swap is in order

[sparkgap]

Thanks for the great software package!
I can't seem to get the spl meter calibration file loaded into REW.
When I browse to the file I downloaded (at the above link), and click 'OK' it tells me 'Not enough data values in the file'. Also, if I use this file, do I have to check the 'C weighted' box or does a loaded file contain the 'C' weighting?

Help!

Thanks
Tom

Edit, OK I'm an Idiot, I downloaded the .xls instead of the cal file. Oops!
T

[brucek]

do I have to check the 'C weighted' box or does a loaded file contain the 'C' weighting?

You only need to check the C-Weight box if you intend to measure past 200Hz where the file ends. The C-Weight checkbox will extend and continue the calibration file past the 200hz at a standard C-Weighting.

brucek

[sparkgap]

Thanks Bruce!

Tom

[Chrisbee]

Thanks to all concerned for the new cal files.

In a desperate attempt to undermine your efforts I did some new traces using the new cal files.

Green and mustard are my two RS meters old and new using the new cal file for old meters. I have a 3dB calibration difference between the two meters on pink noise but they track well on the response curves.

The Galaxy 140 (C-unchecked) consistently reads lower output at about -32dB on SPL calibration. It shows falling output with falling frequency compared with the RS meters. 10dB discrepancy by 11Hz.

Deliberately checking C-weighting makes it droop even further with falling frequency.

I double checked that I reloaded the correct cal files after clearing each cal file. I checked on the graph that the correct cal curve was shown as well as the name appearing in the box under "Settings".

I carefully checked I had C weighting cleared (or checked) as appropriate for each meter and matching cal file.

I tried fast and slow on the Galaxy and carefully "calibrated SPL meter" to 75dB(C) in all cases.

All 3 meters were orientated at right angles to the IB and fitted to the tripod at the listening position without moving the tripod.



Any useful thoughts please?

[brucek]

Deliberately checking C-weighting makes it droop even further with falling frequency

C-Weight check box has no effect within the start and stop limits of the calibration file.

Green and mustard are my two RS meters old and new using the new cal file for old meters.

I don't understand what you're attempting to do here, since I don't know the model numbers or names of the calibration files you're referring to.

I have a 3dB calibration difference between the two meters on pink noise

The calibration files are basically normalized at 1000Hz, with no appreciable difference above 80Hz. Overall gain differences are accounted for in the calibration of REW.

Any useful thoughts please?

If I understand correctly, your problem is that you feel your RadioShack meters don't track the Galaxy meter at low frequencies? If that's what you're saying, then I wouldn't be surprised. The calibration files are for Sonnies meters against his ECM8000. Since he tested each of the Galaxies against each other and they were very consistent, then I would think the Galaxy calibration file would likely be considered accurate for most Galaxy meters. As for the RadioShack meters - it's a crap shoot. Why do you continue to use them when you have a Galaxy?

brucek

[Chrisbee]

brucek wrote:

Why do you continue to use them when you have a Galaxy? brucek

Because I get better bass from the RS meters.

More seriously: I thought they should all track each other if I used the appropriate cal files. I posted my results to see if you agreed

BTW: If I do check C-weighting using the Galaxy cal file and Galaxy meter then it really does make a difference to the response curve. It droops in the low bass. I'll save the graphs next time to prove it.

[brucek]

If I do check C-weighting using the Galaxy cal file and Galaxy meter then it really does make a difference to the response curve. It droops in the low bass.

What does low bass mean? If it's below the calibration file (of 5Hz for the Galaxy and 7Hz for the RadioShack), then the response would be considered unusable. The area between 5Hz and 200Hz for the Galaxy and 7Hz and 200Hz for the RadioShack is unaffected by the C-Weight checkbox.

brucek

[Jerm357]

Just wondering are the files for the 33-2055 Digital RS Meter and the 33-4050 Analog RS Meter supposed to be the same? I belive that you may have the Correction values for the Digital RS meter listed for both Analog and Digital.

[Chrisbee]

brucek wrote:

What does low bass mean? If it's below the calibration file (of 5Hz for the Galaxy and 7Hz for the RadioShack), then the response would be considered unusable. The area between 5Hz and 200Hz for the Galaxy and 7Hz and 200Hz for the RadioShack is unaffected by the C-Weight checkbox.

brucek

I meant below about 25-30Hz.

I am sure I saw a droop on one test when I checked C weighting.
Now I can't replicate it.

I have been following your advice and cutting back on the 20Hz boost filters.
30 sweeps later I'm getting there and the low test levels using the Galaxy are slowly rising. 2 x 20hz +3dB.

Can't let Rodny win this one. IB reputations are at stake!



Oh alright it's rubbish! Where's Steve Callas when you need him? Bwah!

[brucek]

Just wondering are the files for the 33-2055 Digital RS Meter and the 33-4050 Analog RS Meter supposed to be the same?

Yes, they're the same. They're too close to need separate files.... That's why the filename has both the meter model numbers in it.....

brucek