Rat Shack SPL Meter Corrections

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05-16-2005, 08:19 AM
CraigT

Rat Shack SPL Meter Corrections

I went to Radio Shack to get the meter everyone talks about for calibrating their audio systems to find that there are now two new meters...one analog and one digital. The digital has more features and for 10 bucks more seems the better buy. All the correction factors I've found on the net are for the OLD analog meter. I've read a gazillion posts where people say the new meter probably should need the same correction factors but nobody seems to know for sure. Before I drop $50 bucks on a meter and spend time trying to calibrate my sub, does anyone know positively that the correction factors for the old analog meter work for the new digital(or new analog for that matter).

Thanks!
05-16-2005, 10:19 AM
bikeman

Quote:

Originally Posted by CraigT

Before I drop $50 bucks on a meter and spend time trying to calibrate my sub, does anyone know positively that the correction factors for the old analog meter work for the new digital(or new analog for that matter).
Thanks!

The correction factors may not be accurrate for the old meters, let alone the new ones. It's something I've taken on faith but I realize the meter may not be all that accurate. I used to work at an audio archieve that has a calibrated meter. I should stop by and see if that's still the case and compare it my RS meter. Someday.

David
05-16-2005, 02:06 PM
ClutchBrake

As far as I know there has pretty much always been both a digital and analog. The analog was updated recently though.

Pretty much everyone goes with the analog meter. It is cheaper and most people find it easier to use than the digital meter.

Interpreting the analog out of your peripheral vision is much easier than the digital. Same reason most car enthusiasts prefer analog to digital for tach and speedo.

I do not know whether or not the old correction values are relevant to the new meter.
05-17-2005, 09:10 AM
Lee Bailey

I've modified both my RS meters with instructions from this site:
Eric Wallin's Internet Site

I've written to the author, and since he's from MIT, I figure he knows what he's doing. Basically, he responded to me stating that with the 20% tolerances of the components used, no 2 meters would be the same on response.
05-17-2005, 09:53 AM
jimsiff

Quote:

Originally Posted by Lee Bailey

I've modified both my RS meters with instructions from this site:
Eric Wallin's Internet Site

I've written to the author, and since he's from MIT, I figure he knows what he's doing. Basically, he responded to me stating that with the 20% tolerances of the components used, no 2 meters would be the same on response.

Lee,

Did you do both mods, or just the first one that extends low frequency response? Did you add the caps to the back of the board, or remove the original caps?

So the stock caps in the RS meter have a 20% tolerance? If so, is he essentially saying that no matter what correction tables are used, a stock RS meter will be somewhat inaccurate? If there is a 20% tolerance, then I wonder why he says you can keep the old ones in place. You'd think it would be better to use tighter tolerance caps throughout the meter, rather than adding to the poor caps alreaddy in place. Comments?
05-17-2005, 12:44 PM
Lee Bailey

Quote:

Originally Posted by jimsiff

Lee,

Did you do both mods, or just the first one that extends low frequency response? Did you add the caps to the back of the board, or remove the original caps?

So the stock caps in the RS meter have a 20% tolerance? If so, is he essentially saying that no matter what correction tables are used, a stock RS meter will be somewhat inaccurate? If there is a 20% tolerance, then I wonder why he says you can keep the old ones in place. You'd think it would be better to use tighter tolerance caps throughout the meter, rather than adding to the poor caps alreaddy in place. Comments?

I did the cap and mic mod on one unit, and just the cap mod on the second unit. I removed the original caps and soldered the new ones in their place.

I think you should send him an email to address your second question. :confused: I am not an EE.(otherwise, I would have created the mod!) :cool:
05-18-2005, 06:42 PM
soundfreak38

Lee have you looked at the Rives site? I believe their cd2 can be used with the digital meter. To me, the digital is much easier to read especially when I dont really see that well. There is no guessing just record the reading on the chart that can be downloaded from the Rives site. BTW, do you live in a mobile home? I have looked at a few of your pics and it kinda looks like you do---just curious because i do reside in a mobile home.
Phil
05-19-2005, 06:19 AM
BradJudy

The corrections are for C weighting and apply to new/old/digital/analog or even a non-RS meter that uses C weighting.
05-19-2005, 06:47 AM
Lee Bailey

Quote:

Originally Posted by soundfreak38

Lee have you looked at the Rives site? I believe their cd2 can be used with the digital meter. To me, the digital is much easier to read especially when I dont really see that well. There is no guessing just record the reading on the chart that can be downloaded from the Rives site. BTW, do you live in a mobile home? I have looked at a few of your pics and it kinda looks like you do---just curious because i do reside in a mobile home.
Phil

I have the Rives Audio CD. They include 2 sets of tones, one set uses the RS corrections, so you don't have to perform them manually. As for a mobile home, no, it is a ranch style house. I've not owned the digital RS meter.
05-19-2005, 10:05 AM
shane55

Quote:

Originally Posted by Lee Bailey

I have the Rives Audio CD. They include 2 sets of tones, one set uses the RS corrections, so you don't have to perform them manually. As for a mobile home, no, it is a ranch style house. I've not owned the digital RS meter.

Lee... thanks for the advice on the Rives disc. Just ordered one. Sounds like a no-brainer.

cheers