power meter

One approximate method is to work backwards using Radio Shack's SPL meter.

From one meter away measure a pink noise signal. You need to know your speaker's efficiency. Only run the L or R channel. Say your speaker puts out 90Db @ 1 meter with one watt in.

Read your SPL:
90Db 1 watt
93 2 watts
96 4 watts
99 8 watts
.
.
.

Furman VU40 pro audio unit (now discontinued) can read in dB (VU meter) and in watts (power amps) both average and peak readings.

You would have to measure the output at the speaker terminals, not the input to the amp.

If you are using a test signal (normally into a resistive load), then you might be able to get away with a multimeter.

I always though it would be cool if they had a small meter that had five-way binding posts on either side. Then you could put it inline between your speaker and amp. This would be great for just getting a general idea of how many watts your speakers need during certain demanding scenes.

It would help a lot with upgrade decisions.

What you can do is get a Kill A Watt power meter (cheap from Amazon, etc..). That will let you measure the power/current draw off the wall socket. So due to losses in the amp, the actual amp output will be lower than this draw from the wall. That will give you a range.

Radio Shack used to have some audio power displays; there's a couple on eBay now. The Velleman kit K4307 looks just about ideal: it displays up to 2000 watts/4 ohms, and doesn't need an external power supply. It's mono, and sells for about $40. Just google K4307 and you'll find a bunch of places to buy it. The manual has the schematic, if you wanted to build one from scratch.

For line level display, there's the "American Audio" dB-Display, available new from $60.

Wow, someone answered a thread from nine months ago