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SPL meter, Realistic Analog 42-3019

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Hey, has anyone used this meter? I am wondering how accurate it is... I found it in my dad's old stuff and figured it couldn't hurt to check out the system. (My dad was an orchestral musician and a music instructor at a college in the SF bay area. I kinda wonder why he had it.) Anyway... 

I threw a new 9v in it and it fired right up. The only way I could get any good response out of it was to set it to "C" weight (from what I understand "A" weight is more of a 2kHz centered curve for normal speech?) and put it on fast response. This gave me a reading of, on avg, 116 to 120db SPL , with occasional peaks at 122db SPL. This is with a single B2 12", sealed enclosure, driven with 500W RMS, and Focal components up front with 50W per speaker. 

So, knowing that "A" weighted is a bell curve around 2Khz, what is the "C" weight? Is it full range? Or is there a curve on that as well??? 120db SPL seems low, as this sub shakes my steering wheel like it's got palsy, and my side view mirrors won't stay aligned to save my life. (It's an old truck... the side view mirrors just keep dipping lower and lower with vibration. As a side note I would LOVE to know a good fix for this.) 

Anyway I would love to know more, if anyone has experience with these analog meters. 120db just doesn't seem high enough, but wtf do I know?! 

Thanks :)



realistic 42-3019.jpg

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That meter looks sick man, your dad has some cool stuff!

did some digging and found this on a forum; Source

There is a well-known LF correction that must be applied to these meters for accuracy in the bass.
You can find info at: http://www.audioasylum.com/audio/speakers/messages/11710.html

and on the same page

The weighting is for varying implementations of Fletcher-Munson type curves to compensate the level to what we actually hear. The most common are "A" and "C". The "A" curve is based on the 40 phon curve and is used for assessing environmental noise. The "C" curve is for louder noises. You can find out more about them along with the actual curves at wikipedia:

Sounds like an interesting tool I wonder how it’d be of use for car audio.

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Nice link! According to the wikipedia charts, the C weight still has a roll-off that starts around 100(ish) Hz that kinda matches the other link's innacuracy adjustments. ... more reading definitely required. 

I tell ya what... watching the meter move is kinda fun. I was trying to hold it every direction I could think of in order to account for sine wave variances, and it held pretty damn steady. 

As for car audio... I can't think of any real reason to use it. It's more just for curiosity sake. ... what I can say is that my system plays clean at 120db, and that the needle only drops a couple db between the bass kicks and the mids and the highs! 

I figure because of the analog response that this is more of a 'sum' of the sound, as opposed to a higher end digital meter that can measure a quick transient SPL hit. ... but again.... I'm just talkin out my ass cause I really have no idea. 

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