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[Robert Patch]

An email from Evan,

"The picture posted was one of 5 mic positions, and that was the one that gave me the least coherence in the HF. The cardboard was removed for the measurements posted on PSW, and I picked the best looking results for the forums."

Sorry if my photo was an incomplete picture.  This is all pretty new to me.

[Art Welter]

Jeff Permanian wrote on Thu, 20 January 2011 17:09

Orbit Shifter: 2 watt so minus 3db for a 1 watt

Jeff,

“2 watt so minus 3db for a 1 watt “ so -3 dB from the 98.3 Hz 110 dB peak, we get 107 dB.
At 36.6 Hz the graph shows 103.6 dB, keeping in whole numbers 104 dB -3 dB is 101 dB.
Halfway between the two is 104 dB, yet you rate the Orbit shifter sensitivity at 106 dB at 8 ohms in your web site specifications.



2 dB is not a big deal, but a discrepancy.

If the test used a 4 volt signal, that would be 2 watts at 8 ohm.

However, 4 volts is 8 watts at 2 ohm, if the Orbit Shifter speaker was wired at 2 ohms and driven with four volts, the  adjusted one watt sensitivity would be 98 dB, which would be a large discrepancy.

Would you please explain the 2 dB (or possibly 8 dB) discrepancy, and tell us some measurement details, such as the voltage used, the impedance (2 or 8 ohm), distance from microphone to speaker, microphone calibration, and distance to any walls ?

Art Welter

[Steve Hurt]

That's odd.  (The spec page)
I thought my Orbit Shifter were 4 ohm.
Have to check that.

[Art Welter]

Steve Hurt wrote on Fri, 21 January 2011 12:39

That's odd.  (The spec page) I thought my Orbit Shifter were 4 ohm. Have to check that.

Also odd that the Growler is rated at 100 dB sensitivity, yet is within a dB or so of the  JBL SRX718, rated at 95 dB sensitivity.



Phil’s test results look to be a few dB high overall.

Hopefully, Jeff will clarify.

[Steve Hurt]

If the SRX are rated in full space (and JBL sort of says they are) the difference in subs specs, and at the same time, similarity in Phil's measurements, would make a lot of sense.

[Art Welter]

Steve Hurt wrote on Fri, 21 January 2011 15:04

If the SRX are rated in full space (and JBL sort of says they are) the difference in subs specs, and at the same time, similarity in Phil's measurements, would make a lot of sense.

The SRX subs are not measured in full space, neither were Phil's measurements of either sub. His measurements of the JBL are within 2 or 3 dB of the JBL chart, considering his microphones are not calibrated or big buck, that is pretty close.

I recently (finally) got to compare my dual LAB 12" front loaded sub to a JBL SRX 728 outdoors, either the 728 sensitivity is what it is claimed, or my subs magically gained 6 dB   .

[Grant Conklin]

Art Welter wrote on Fri, 21 January 2011 18:29

I recently (finally) got to compare my dual LAB 12" front loaded sub to a JBL SRX 728 outdoors, either the 728 sensitivity is what it is claimed, or my subs magically gained 6 dB   .

I'd be interested to see the results of that comparison.

[Ivan Beaver]

Grant Conklin wrote on Fri, 21 January 2011 20:20

Art Welter wrote on Fri, 21 January 2011 18:29 I recently (finally) got to compare my dual LAB 12" front loaded sub to a JBL SRX 728 outdoors, either the 728 sensitivity is what it is claimed, or my subs magically gained 6 dB   . I'd be interested to see the results of that comparison.

http://srforums.prosoundweb.com/index.php/m/612837/6883/#msg _612837

[Jeff Permanian]

Art Welter wrote on Wed, 19 January 2011 18:00

But now I know the one watt one meter sensitivity of four front loaded dual Lab 12s is only around 98 dB, I want a pair of DSL TH -218, their sensitivity is 10 dB higher ! Art Welter

Art, Since you've take quite an interest in my specs maybe you should take a look at other manufactures. DSL doesn't make a TH-218 but they do make a TBH-218, rated at 112db sensitivity, 2.83 volts, 2 ohms so minus 6db for a 1 watt sensitivity.

[Jeff Permanian]

Art Welter wrote on Fri, 21 January 2011 18:29

The SRX subs are not measured in full space, neither were Phil's measurements of either sub. His measurements of the JBL are within 2 or 3 dB of the JBL chart, considering his microphones are not calibrated or big buck, that is pretty close.

Art Welter wrote on Thu, 20 January 2011 14:20

I have attempted to calibrate my Smaart readings, but am not sure if they are absolutly on. I have not attempted to calibrate them with the RTA 420 microphone I was using in the above test. I have  written several times that I can’t get my 3 meters to agree at more than one frequency.. Art Welter

Forgive me if I question the absolute level of your measurements and your correlated sensitivities.