 Measuring power going to speakers?
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Just curious how to measure how much power is going to the speakers in my system? Last night I hooked up the other M3 to the centre channel in parallel and it sounded AWSOME. Wow, there was no sign of current limiting (while driving all 5 channels) and I had to decrease the trim by about -5db on the centre (I am sitting about 12 feet away from the centre channel). I then watched about 1 hour of Battle Star Gallactica (I must say that the drums that play regularly in that series sound WICKED on the M22s and the EP500 sub, frackin' eh!) with the Parallel M3s. I was listening for any signs of distorion at all...I thought I mabey heard some, so I disconnected one of the speakers (I should add here that my wife was totally freaking out for me pausing and rewinding this one scene where I suspected the distortion). After cutting it down to one M3 the scene sounded exactly the same (I was pushing the AV reciever a bit to -20dbs for a bit to see if the RX-V659 could handle the 4ohm load on the centre, not sure how loud that is, my wife again told me to turn it down  ). There was a major diference from parallel M3s down to 1 M3, the 2 M3s in parallel sounded just so awsome, I couldn't believe it. Back on topic in my own topic...how can I measure the power going to each channel to see how much current they are all getting?
Last edited by Hutzal; 02/02/07 05:04 PM.
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Re: Measuring power going to speakers?
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This is getting into the, too much time on my hands, things to do list.
I would use a multimeter and measure the AC amperage going out to the speakers and then the voltage, from that you can calculate the wattage. I don't remember the formula's any more. I checked my system real quick and found I had 270 milliamps at low listening levels, I forgot to write down the voltage, my kids were battling at the time.
I am guessing you are concerned about the parallel M3's power consumption?
Jason
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Rick
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>>I am guessing you are concerned about the parallel M3's power consumption?>>
Exactly, in the manual is states that a 4ohm load is ok for the mains, but a 6ohm should me the max that should be used for the centre channel.
I suspect that all is well, I just want to make sure that I don't ruin anything. I bought the 5 year extended "exchange for any model for any reason" guarantee from Sounds Around, so at least I know that if someting blows in the 659, I am covered. But from the sounds of it, i thought that the amp was handling the load very well and judging by the fact that I had to trim down the centre channel -5db proves that there is no current limiting going on (right?).
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Hi,
You're OK so long as you aren't hearing any distortion. If the amp goes into current limiting, then the overall power output is reduced so it could clip (distort) more easily.
You won't hurt anything because the amp's protection circuit would normally shut it down if the output transistors got too hot. All protection circuitry usually has thermal monitoring to shut down the amp if the output stage overheats.
Measuring real-time power output levels is really difficult because of the constantly varying music signal, so you'd want to know what the peak values are. In some ways, it would be easier to put an oscilloscope across the amp output signal and monitor the waveform for any evidence of clipping. You can see that when the top and bottom of the waveform is truncated. If that occurs, I expect you'd hear the distortion because it would be in the 1% to 3% range (at least), which is pretty audible.
Regards,
Alan Lofft,
Axiom Resident Expert (Retired)
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Re: Measuring power going to speakers?
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>>oscilloscope>>
Wow, never seen that word before, I think its a little out of my price range just to find out if the 4ohm load is ok (>$300).
I was thinking about playing some music through all the 5 speakers, cranking it up really loud and seeing if the centre channel distorts/clips at all. I already tested this method yesterday, but no louder than -20db.
The problem with that is that there is so much noise everywhere it would be hard to determine if the centre channel is indeed clipping.
So if there was a problem...I would hear the speakers coming in and out right? I also didn't notice any excessive heat coming from the amp after 2 hours of Dolby Digital 5.1 content at -30 db.
EDIT: Was just reading on AVS' RX-V659 thread, a user is using 2 surround channels that are 4ohm and only noted that the amp got pretty warm but not excessivly hot, and he didn't notice any distortion when watching a dts movie.
Seeing as I will only have one 4ohm load (even though the center is used more than the surrounds) I think the 659 can handle it. I am quite amazed at the speakers that this budget receiver can drive. I am probably going to watch a familiar movie tonite (or bits and pieces anyway) to determine for sure.
Last edited by Hutzal; 02/02/07 11:21 PM.
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I am willing to bet your EP500 that you will not have any trouble with the Yammie. Have some more fun tonight watching and listening to your new HT. Wait a minute you still have work to do..hurry up and get that room done would ya. 
Jason
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Alan told you the correct way of doing it. What you need is either the scope or a peak reading power meter/ voltmeter.
Last year, one of the board members did exactly that and posted his results. As I recall, the peak to average power was about 25:1 which indicated to me that one needs to be concerned with both peak and average power.
Maybe someone can find those posts and put them here.
The Rat.
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Rick
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Robb, there'd be no reason for the paralleled center speakers to be "clipping". When the speakers are operating in parallel there's an increase of 3dB in sound level, so dropping the level 3dB to keep it the same as before results in only half as much power being required, not more. Apparently, as strongly suspected, the 659 has no problem with that load, which drops below 4 ohms at certain frequencies.
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Yes, that is the one. Good show!!!!
Does Gena still post on this board? I haven't seen anything from him in quite a while. Of course, that could just be me since I haven't been all that active until recently.
I still think that that series of posts was one of the best technical threads.
I have continued to look for articles on peak/ average power per speaker for 5.1 and 7.1 systems but haven't found any. I suspect that some of the major companies have run tests but are keeping the data proprietary.
The Rat.
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Quote:
I have continued to look for articles on peak/ average power per speaker for 5.1 and 7.1 systems but haven't found any. I suspect that some of the major companies have run tests but are keeping the data proprietary.
Not sure what you mean here, as those kind of specs would be continuously variable per speaker during playback depending on the volume a person wishes to listen at and the mix that was done.
Jason
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Re: Measuring power going to speakers?
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Yes, you are absolutely correct!!!!
However, there ought to be some metrics on how much power the fronts, surrounds, and rear surrouds take on different types of music at different listening levels.
For example, if the fronts take 1 watt, then I would expect that the surrounds would take 1/4 watt or something like that.
It should not be that difficult for a major company to put scopes or peak reading power meters on all speakers and see what the readings are.
The Rat.
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Quote:
Robb, there'd be no reason for the paralleled center speakers to be "clipping". When the speakers are operating in parallel there's an increase of 3dB in sound level, so dropping the level 3dB to keep it the same as before results in only half as much power being required, not more. Apparently, as strongly suspected, the 659 has no problem with that load, which drops below 4 ohms at certain frequencies.
Well, i got my email back from Yamaha Canada, they stated that the centre channel is not designed for a 4ohm speaker, i suspect that since it is 2 speakers creating a 4ohm load, like you said John, the output is 3db louder and thus the load will be 3db less than normal 4ohm speaker.
They recommended NOT to run a 4ohm speaker on the centre channel, I have not experienced any distortion or clipping from the load on the reciever even after playing at really loud levels in my little room around -15db is loud to me 
I'll let you all know if further problems persist with the 4ohm parallel load, but I suspect that all will be fine.
PS: The downstairs is ALL painted! just waiting for the carpet....ooooooooooooooo yyyyyyyyeeeeeaaaaaaahhhhhhh.
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I think that you may be starting to get confused with driving point impedance and power versus how many speakers that you are using. Your amplifier really does not care how many speakers are connected in parallel, series or a parallel-series combination to give a driving point impedance of 4 ohms, 8 ohms or any other value. The efficiencies of the speakers connected in whatever fashion will determine the sound level.
Not to make things complicated, but 4 ohms is 4 ohms is 4 ohms.
The Rat.
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Quote:
Not to make things complicated, but 4 ohms is 4 ohms is 4 ohms.
This is true but a 4 ohm impedence will draw more power from an amp at any given point on the dial.
Rick
"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud
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Quote:
Yes, you are absolutely correct!!!!
However, there ought to be some metrics on how much power the fronts, surrounds, and rear surrouds take on different types of music at different listening levels.
For example, if the fronts take 1 watt, then I would expect that the surrounds would take 1/4 watt or something like that.
It should not be that difficult for a major company to put scopes or peak reading power meters on all speakers and see what the readings are.
Why would the surrounds only take 1/4 of a watt if the front takes 1 watt? They will take what ever they need to send out the sound to the proper calibrated level. The amount a speaker takes depends on the level commanded by the source. If the front is 1 watt then the same sound source through your surrounds would be 1 watt, if all the speaker settings are the same.
Or are you wondering about adjusted speaker levels and the fact that the rears might be adjusted to output, say 3db higher to achieve 75db at main listening spot. In this case I know there is a formula to go from db to watts,(something like 10watts per decibel). Then using my made up formula, the extra wattage needed for the +3db speaker is somewhere near 30 watts more power needed.
Jason
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Quote:
Not to make things complicated, but 4 ohms is 4 ohms is 4 ohms.
But there is such a thing as 4ohm using less power and 4ohm using more power correct?
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Hi,
It doesn't surprise me that Yamaha Canada warned against running a 4-ohm load on the center channel. Most mainstream AV manufacturers would say the same thing because of consumer liability issues.
But in your small room, it seems your 659 is not unduly stressed by the lower impedance.
By the way, I wouldn't try and keep increasing the output level on your Yamaha beyond normally loud levels, as you wouldn't want the center channel amp to clip. It might do so and send a square wave to the M3's tweeter burning it out instantly. The protection ciruitry in the 659 is supposed to prevent this from happening but, you never know. And it could happen before you heard any gross distortion because the masking effects of 5.1 channels running are substantial. Distortion in the center might go unnoticed until it was too late. . .
Axiom would get really cranky about replacing your M3's tweeter if that happened while you were "testing" how loud it would play.
Regards,
Alan Lofft,
Axiom Resident Expert (Retired)
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Re: Measuring power going to speakers?
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>>Axiom would get really cranky about replacing your M3's tweeter if that happened while you were "testing" how loud it would play.>>Thanks for the warning Alan, I didn't know that this could possibly happen. I will cease to continue my testing on the centre channel, the last thing I want is a cranky Axiomite 
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Wid: that is not necessarily true. You are forgetting about the speaker's efficiency. In theory, a 4 ohm speaker could be "louder" than a 8 ohm speaker for the same input power.
Jake: I'm not quite sure what you are trying to say. But, the power distribution between the fronts, rears, rear surrounds is most probably NOT equal for any music composition. This may be even more profound when signal processing is used. I have been looking for relative distribution parameters but haven't found any. The bottom line is that it is highly unlikely that all of your channels would require either maximum peak or average power at the same time.
The Rat.
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This is true and I should have said of the same efficiency.
Rick
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Jason, the actual formula for the dB relationship between two power levels is 10 log(P2/P1). For example, the log of 2 is about 0.3, so when power is doubled this results in 3dB more loudness. This is true regardless of whether the increase is from 1 watt to 2 watts, 10 watts to 20 watts, 100 watts to 200 watts, etc.
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Quote:
Jake: I'm not quite sure what you are trying to say. But, the power distribution between the fronts, rears, rear surrounds is most probably NOT equal for any music composition. This may be even more profound when signal processing is used. I have been looking for relative distribution parameters but haven't found any. The bottom line is that it is highly unlikely that all of your channels would require either maximum peak or average power at the same time.
Exactly, not equal for any music composition, its the music that dictates how much sound comes out of the speaker, so depending on what you are listening to, the power at each speaker will never be the same, constantly variable as I said before, which would be next to impossible to put a power figure on, except maximum and minimums. The power needs are always changing. You can take max and min readings for one disc/song and the next disc/song will have different readings.
But as you stated you are thinking more in terms of the power distribution of DSP settings and the amount they decide each speaker should have when in Jazz or Arena modes. I would bet that each manufactureer has their own set of parameters and they would be very hard to find. I guess you could try using a steady input source and then measure each speaker to see how much each gets during each mode.
And thanks for math lesson John. I can never remmeber those formulas for very long.
Jason
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Well, the point that I was trying to make is that I strongly suspect that the power required for the fronts is much more than that required for the surrounds or rear surrounds for almost any music. The question is what is the relative ratio?
I may have to "borrow" a peak reading voltmeter and make some measurements myself.
The Rat.
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Quote:
I may have to "borrow" a peak reading voltmeter and make some measurements myself.
peak reading meter AKA oscilliscope
i think rms x 1.44 = peak
i think most meters were at one time were designed for ~60 hz readings, but maybe they are accurate over a larger freq. range now.
hth
randy
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I think that you need to review peak and RMS calculations as compared to both a sine wave and a complex signal!
The Rat.
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Quote:
Well, the point that I was trying to make is that I strongly suspect that the power required for the fronts is much more than that required for the surrounds or rear surrounds for almost any music. The question is what is the relative ratio?
I may have to "borrow" a peak reading voltmeter and make some measurements myself.
I still think that depends on the DSP and music. I like to listen in 6channel stereo and from my listening position with all speakers calibrated to the same levels (all speakers same distance from sweet spot and of the same type) they should all have the same power requirements, for the same note played through all the speakers, other wise why would the amps need the same amount of power for all channels? That would make the all channels driven spec a marketing ploy. My old Pro logic receiver had lower center channel and rear surround wattage than the front mains and it was impossible to get the speakers to equalize during play back.
Please do some testing, enquiring minds want to know. Well at least you and I.
Jason
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