Originally Posted by OllieS
Originally Posted by arnyk
Probably the best way to measure the power drawn by your speakers is to measure the voltage across the speaker terminals. Yes, its not power, its voltage but under most conditions, the voltage across the speaker terminals is the best way to determine if the power drawn by your speakers is causing your amplifier to clip.
How would I go about doing something like that?
(1) Obtain a voltmeter with good frequency response. As others have pointed out, most multimeters cheap or not are designed to measure regular electrical power whose frequency ranges from 50 Hz to 400 Hz. It is not the least bit uncommon for the response of a common multimeter to drop like a rock starting around 1 KHz. Obviously, to measure audio voltages we need a meter that responds accurately over the regular audio band, from 20 to 20 KHz at minimum. Just to confuse the matter, the actual frequency response of common voltmeters is often not specified as well.
Here are some frequency response curves for common Digital Voltmeters (DVMs) that have frequency response that is at least above average:
One of the more available and cheaper of them (Fluke 27) retails for $475. Several such as the excellent and classic Fluke 8060 are discontinued. I've seen some likely candidate 8060s on eBay for around $100. Caveat Emptor.
(2) The second problem is that audio in general varies a lot and the digital displays on DVMs don't even pretend to keep up. If you want to accurately capture the peaks and variations, then you need something like a digital recorder that can withstand the relatively large voltages that one finds on speaker terminals - probably up to 50 volts RMS. AFAIK, you are on your own engineering project if you want such a thing.
If I wanted to measure power, not voltage, is that something that a person can do, or is measuring voltage the only method people use for checking how much juice is being used?
There are such things as watt meters, either mechanical or electronic, but again they are typically designed for use with power line current and therefore only operate accurately over a narrow range of frequencies. I've measured true power delivered to speakers but I ended up engineering the equipment/software used myself and spent over $1,000 assembling it.
I believe that there are commercial audio test sets such as those made by Audio Precison that have actual power measurements as a standard feature, but even the first edition of AP equipment (AP System 1) now decades old in good condition is sold for thousands of dollars and takes serious training and experience to use competently.
Say I'm watching a movie like Master and Commander. I switch my subs off. Just want to measure the power on the most dynamic portions of the movie. I know that movie very well. Chapter 4 is when the cannons go crazy... very soft, to very, very loud.
I know of no off-the-shelf options for you that don't require a big financial and time investment.
I guess I'm just really curious to know what is going on here. If my speakers were only using, say, 40 watts, at the levels I listen at, I would find that interesting.
But as far as amp clipping goes, would it not be obvious whether it was clipping?
If one makes a digital recording of the voltage across the speaker terminals and looks at it with an audio editor even just freeware Audacity software, the flat-topping would be pretty obvious.
I thought amp clipping was audible.
If there is enough of it, its readily audible and not nice to listen to.
I don't hear gross distortion at any point on my system, but I sure would like to know how much of the available power is being wasted. It would teach me not to spend money on things I don't need!
I still think that AVRs should have clipping indicators. They are common features of pro audio amps, and many of them like the simple but highly sensitive and effective one that QSC uses don't cost a ton of money to implement. I think the QSC clipping indicator circuit is composed of 6 parts costing less than a dime each in production quantity (4 signal diodes, 1 LED and 1 resistor).