Re: Why Do TEF Systems read 3-5 dB high ?
I have no grudge against JTR, and neither does Phil Lewandowski, he owns (or owned) both JTR Growlers and JBL SRX 718 cabinets.
I have no grudge against any manufacturer, but having studied a metric shitload of graphs and simulations, it seems that various TEF results look high compared to other tests.
If and when I install DSL product (or any other product), I’d like to know for sure that if DSL sub cabinet “X” graph shows 3 dB more sensitivity than a JBL sub of similar frequency response, it will indeed match the sensitivity of two JBL subs.
If there is a difference of 3 dB (or more), as I suspect, I can't make that assumption.
Phil tested the JTR Growler with the Beta 2010 12” 23 mm Xmax driver, posted results on Thursday, 27 May 2010 21:27 on the old LAB.
JBL SRX718 - Basic Distortion Measurements
http://srforums.prosoundweb.com/index.php/t/56314/19717/
Figures are raised by 20 dB to account for the difference between one meter and ten meters, so they should equate to one watt one meter .
The tests were done using sine wave tones at 85 volts (900 watts at nominal 8 ohms)
55hz - 125 dB
60hz - 126 dB
70hz - 130 dB
80hz - 128 dB
Phil did a JBL SRX 718 test the same day posted Thursday, 27 May 2010 21:47.
55hz 125dB
60hz 126dB
70hz 129dB
80hz 127dB
From that test, it is clear that the Growler and the SRX 718 have very similar output in the 55-80 Hz range.
JBL’s graph shows the 718 as slightly under 95 dB, they rate it as 95 dB one watt one meter.
JTR does not have graphs on his website, but rates the Growler as 100 dB sensitivity, +/- 1dB from 45-90 Hz.
IIRC Jeff had Mark Seaton do his TEF testing.
It appears either JBL is understating their product by 5 dB, or Jeff overstates his.
JBL’s specs are not in whole space, I have confirmed that with my own side by side testing of an SRX 728 to one of my ported dual Lab 12 cabinets.
Art Welter
