Axiom Home Page Forums General Discussion Home Theater Axiom speaker power usage ?

Brandon, a multimeter can measure voltage, amperage and resistance(rather than single-purpose voltmeters or ammeters)and power can be derived from the results by using Ohm's Law.

If you're listening to music (ie time-varying signals) don't you need to measure both current and voltage at the same time ?

John, that's the case for accurate power measurements. For example, NI points out here that "simultaneous" voltage and current measurement is necessary. Depending on what the capability of the Fluke 83 is, I suppose that resistance measurements could be taken, then the various voltages, and an estimate of power arrived at by using P=V(squared)/R. We'll see.

Hey guys, lighten up. There's no need to bring mathematics into this. Just use your ears, please.

>>Depending on what the capability of the Fluke 83 is, I suppose that resistance measurements could be taken, then the various voltages, and an estimate of power arrived at by using P=V(squared)/R. We'll see.

If you're willing to treat the speaker as a constant impedence then only one of voltage or current is required. I guess the question is whether that is close enough for this purpose. The impedence varies with frequency, so depending on the content you could have power levels differing by 2:1 at the same voltage.

I guess as long as the signal is "typical music" you could measure voltage (across the speaker) and current (in line with the speaker wire) once by playing the same material twice, use those values to calculate average impedence (I'm gonna feel stupid if it's exactly "4 ohms" ) and then for the rest of the calculations use that average value plus voltage measurements.

V^^2 / 4 is sounding better and better all the time.

Sorry for not updating my post sooner, but the Outlaw issue has become a way more involved than I had thought it would be. But bridgman has it correct with "V^^2 / 4 is sounding better and better all the time" In the past several weeks I have invested over $8k in Axiom/Outlaw products, and I thought I would have more than enough power to run the five M80's, even at a rather high level at times. The 770 is having a problem doing that, and after trying all of the trouble shooting ideas from tech support at Outlaw, and being told that it was very possible that my M80's, two of which have 60' runs for speaker wire, could be demanding to much power and causing the left rear amp to go into thermo protection, I needed to find some way to test the M80's consumption and see exactly what was happening. Since I do not have a $50k of test equipment, my simple mind went with the Fluke I have and do a simple voltage check. I have been doing this for several days, differant source material, differant volume levels, swaping out the M80's to differant locations, so on and so on.
I really need to thank Alan, as he has spent several hours with me on the phone about this issue, and I have needed to learn a way more about the M80's than I wanted to. lol Once again, I'm waiting for a call this morning from Outlaw to see what they have decdied to do. I will post an update as soon as I have some sort of resolvement to the problem, all I know for sure at this point, it is not my Axiom speaker wire, banana plugs, or speakers. From my very basic tests, all of the Axiom products are staying within the specs, and not over driving the 770. Thanks for all of the interest, and will have some data when done. ;-)

yes, but i have yet to see one that can do all of those at the same time. I suppose he could play the music at a set volume and take the voltage readings, and then hook the meter up to measure current and then play the material again at the same volume. Im not sure how much current is needed to drive the speakers but i imagine its way over what the meter is rated for.

Will try to clear up any confusion on how I trying to prove to Outlaw that the M80's are not drawing more then the 300 watts @ 4 ohms, which is what the 770 specs state. I'm using the Fluke meter on the 400 ac range, attached to to the speaker, and then just to the 12ga Axiom speaker wire. The meter is set to record the max,min, and average voltage. The CD soruce material is played for the same length of time, at the same voulume levels. I have used the meter, and I know the resistance of each speaker wire when connected to just the speaker, the amp, and just length of each speaker wire. When I have the voltage readings from each sampling of music and the volume levels, I then use V^^2 / by which ever resistance to determine the wattage. As I stated before, this is the only way I have to do a wattage test, to try and show Outlaw the M80's are not over driving the 770, its strictly a heat distribution issue on the 770. Well the wattage useage I find may not be 100% totally accurate, its the only way I could think of to try and prove what is happening with the 770 in my enviroment. ;-)