Axiom Home Page Forums General Discussion Technical Questions Radio Shak SPL meter

I own one of these meters and have lost the instructions. Can any body tell me what the weigthing switch does / means (A and C)? I usually keep it a C, but I don't understand, isn't volume scale in dB. How can it change? And why isn't here a weighting B?

Thanks

Paul

I just bought one of these today (the digital ones) and I was looking through the manual.

I don't remember the exact descriptions of the two, but it said that A was for 'natural environment frequencies' or something along those lines.

It said to use c for the calibration of PA's or stereo equipment.

Edit: here is a link to the manual

http://rsk.imageg.net/graphics/uc/rsk/Support/ProductManuals/3302055_PM_EN.pdf

Hi Worfzara,

Always use the "C" weighting scale for all measurements of reproduced music levels at home, live music SPL measurements and outdoor measurements of any kind of industrial sound levels or live concerts. The "C" weighting takes into account bass frequencies, whereas the "A" weighting scale suppresses the importance of deep bass.

I can't recall if there is a "B" weighting or what it represents. I've never come across a reference to it in all my years writing about and reviewing audio components and loudspeakers.

Regards,

Alan

According to the manual the A rating responds to
'mainly frequencies in the 500-to-10,000 Hz range only'

So I imagine it would not be very good to calibrate a stereo system!

C-weighting takes in to consideration the "frequency response" of the human ear.

And no, Alan.. they don't include B-weighted, D-weighted or any of the ISO weightings/curves.

Bren R.

Thanks everyone for the info!

Radio Shack (Circuit City) here in Canada only sells one SPL meter and it is digital. I have talked to a home theater setup professional and he said that the digital meters are far less accurate than the analog meters, and he doesn't know where to find an analog one around here. I can find an analog one on the Internet easily, but it will be more expensive. If his advice is true, I will definitely go the analog route.

Has anyone else heard anything, or experienced the difference between the digital and analog SPL meters.

Thanks

The meter I have is my dad's, and he bought it in early 80's. It is analog. Thanks for posting this, cuz I was gonna give it back to him and buy a digital one. Maybe I will just keep it.

Paul

I bought one like this (not this seller) on ebay last year, I think it was about $30 to get it to my doorstep. It looks very similar to the old RS analog meters, but I'm not sure if it's the same internally or just a knock off.

Anyways, it has worked well enough to let me calibrate my speakers to each other. The whole thing could be off 10db, but at least all the speakers match! Someday I'll bring it out to site and see how it matches up against the meter they use down in the OH&S department.

My understanding is that both are equal in terms of accuracy, but many prefer the analog meter for HT calibration.

I would think it would be easier to read a fluctuating needle than it is on a digital display.

Hey Wheelz, call a music/instrument store as they're a good place to start. I know the one in my neighbourhood (Burlington) has some that you can rent or buy. I ended up getting the digital one as at the time it was all they had and it was cheaper.

You should be able to find a place in Toronto that has some and can ship to Peterborough.

Thanks for your help, it's greatly appreciated. I was trying to think of other stores that might have other meters but I couldn't come up with anything. A music/instrument store makes a lot of sense.

Thanks again

According to my professor for noise and vibration control class the A-weighted scale closely models the human response to sound below 55 dB and the C-weighted scale models the human response for sound above 85 dB. The human response is a function of not only frequency but also level.