Posted by Wayne Parham [ 184.108.40.206 ] on November 02, 2006 at 15:44:06:
In Reply to: Re: JBL SRX728S posted by Tom Danley on November 02, 2006 at 07:55:21:
Each of those charts was done with a 2v signal. Since the distance was 10 meters, add 20dB for the 1m value. Add another 3dB if you want to normalize to 2.83v. The JBL SRX728S response chart shows about 98dB/2v/1M at 100Hz, 97dB at 70Hz and a smidge under 96dB at 50Hz. Peak output is about 106dB at 500Hz, and there's a peak to 104dB at 220Hz. There's a 10dB dip at 200Hz and a 20dB dip at 450Hz.
I think what may be causing some confusion is the way Praxis works. The data captured hasn't been post-processed or anything like that. There is a sense line that reads amplifier voltage and presents the data normalized to a reference level. In each of the datasets captured at this year's Prosound Shootout, the reference level was 2v. This is comparable to last year's 28.3v measurement, but offset by 23dB. There is also a decibel/voltage/power conversion chart posted so that people can compare SPL between systems having different impedance.
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