mellymelsr
Member (SA)
...I'm gonna have to stop by and have a listen to that one Norm...I was eyeing one of the China models...
Sharp GF-800z
- Thread starter Superduper
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oldskool69 said:Superduper said:
Not measuring SPL. Using actual voltage output from the speaker terminals. It's a simple starting formula, not as accurate as a test bench but will give you a general idea:
Say at 1kHz test tone with volume turned all the way up, you get 10v output (AC) at the speaker terminal.
Multiply this by the same, so 10v x 10v = 100v.
Now divide by resistive load, e.g. 8 ohms, so 100v / 8 ohms = 12.5w
Now, one must realize that attempting to get all 12.5w is unrealistic for usable power, factor -27% (-3.375 in this case) for circuit loss and inefficiencies, plus account for the fact that the power supply is being drained by rails for other components as well. This also accounts for the fact that the amplifier will go into clipping faster as it's starving. (Most amp chips deal in varying voltage requirements for desired output depending on application. That gets into the heat factor which is it's own issue.)
So 12.5 - 3.375 = 9.125w
Keep in mind you have NO speakers hooked up (unless you want to blow one or go deaf) during testing. And when you play your music, remeber that music fluctuates greatly so your mileage will vary on percieved loudness. So don't get hung up in the numbers. But it is fun nonetheless and will give you somewhat of an idea of what your boomer can really do.
Now why in the world didn't I think of that. My Sencore SG-165 has an RMS output test measurement function in 2 ranges: 0-10w in low range or 0-100w in high range. With the addition of an oscilloscope, we can actually take a reading at just before when distortion manifests giving us usable RMS power. I've never used this function on this tester since I'm way more interested in fixing dead channels, troubleshooting tuner issues, etc with this instrument. Determining receiver RMS output power is interesting, but not usually why I whip out a peice of test instrument. Hey guys, if you want to learn to troubleshoot boomboxes, I proclaim the Sencore SG-165 AM/FM Stereo Analyzer the instrument of choice and indispensable for this purpose. In my opinion, if you buy no other piece of equipment, this has got to be one of the first after a simple digital multimeter, and priced very reasonably too, with respect to test instruments which typically are mucho mucho dinero.
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