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Watt rating of audio equipment

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LAN_403

Part Scavenger

Fri Mar 03 2006, 03:50AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

OK, what's the deal with audio equipment? I just got a 600W surround sound system that claims 100W per speaker. Ok, first of all, the watt rating on the power supply says 160W MAX. Secondly, the 15 something foot long looks like 20-22 ga wire they sent with it isn't supposed to carry 10A. (6 ohm speakers). AND there was a 1000W system that would not get nearly as loud. I know the power going through the speakers is not continuous, but still. Something seems out of wack here.

I tested the output of my stereo (different than the one referred to above) and I used the AC function on the meter, connected it to the speaker output. I took that voltage rating (between 30 and 40V, don't remember) and used ohm's law and the ratings of the fuses to calculate the watt rating. I came up with 50W per channel and 200W in all. Is this correct? I think I should have probably used a sine wave, but I was going for "general".

So what's up with audio watt ratings and did I measure my amplifier correctly?

Hazmatt_(The Underdog)

Fri Mar 03 2006, 04:22AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

did you look at the specifications in the back of the booklet that came with the amp?

What you're looking at is 600W peak not r.m.s.

ChemTechLabs

Fri Mar 03 2006, 05:03AM

Registered Member #98 Joined: Thu Feb 09 2006, 05:53PM
Location:
Posts: 14

are you using your own amp? or did it come with the suround sound set?

ragnar

Fri Mar 03 2006, 05:31AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
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Posts: 1425

Don't worry, there's nothing wrong with the ratings, you, or your amplifier.

Often you'll see people selling speakers like this:

"80W* Speakers**! Buy now!"

* 10W RMS. 80W Peak-peak-peak maximum instantaneous system*** power.
** System of four speakers
*** System power consists of four speakers at 40WRMS max operating power.

It's a bit of a shame. They'll quote the wattage figure, and that's really the PEAK-PEAK-PEAK-MAXIMUM wattage EVER for the whole SYSTEM. You'll find the RMS power for the system is less than half that, and the RMS power for each speaker less than half that again (depending on how many speakers

All a bit stupid really. =)

Liam

Fri Mar 03 2006, 06:32AM

Registered Member #113 Joined: Fri Feb 10 2006, 01:40AM
Location:
Posts: 49

The last time I set up audio equipment for our school dance I actually totalled up the wattage (a few thousand watts) and I realized that that couldn't possibly be true because the system was plugged into a 15A circuit. The subwoofers alone would have tripped the breaker. I then realized what was said above. The power supply can suck say, a few amps, but there are usually some fairly massive capacitors that can allow you to hit a few thousand watts - as long as it's just for a short amount of time!

thom

Fri Mar 03 2006, 06:37AM

Registered Member #239 Joined: Thu Feb 23 2006, 03:15AM
Location: canada
Posts: 23

blackplasma wrote ...

It's a bit of a shame. They'll quote the wattage figure, and that's really the PEAK-PEAK-PEAK-MAXIMUM wattage EVER for the whole SYSTEM. You'll find the RMS power for the system is less than half that, and the RMS power for each speaker less than half that again (depending on how many speakers

All a bit stupid really. =)

Yeah, they use incredibly small amounts of time to maximize peak power.. that or they just make it up.

Next time do a little more research, or look into high quality used speakers.

http://en.wikipedia.org/wiki/Watts_RMS

Hazmatt_(The Underdog)

Fri Mar 03 2006, 08:35AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I really wouldn't worry!

I have a Yamaha 600W HTR-5730 and it really is a fantastic amp. At -11dBm its just great. And at 0 dBm all hell breaks loose. This with my 100W RCA sub turned up at 9:00 position (~25%) it makes a great theater. I often have to turn it down because it shakes the walls too much XD.
I have 2 100W tube amps that I play guitar through, not at the same time, but occasionally I crank them up to about 2 when I play with friends. These guys will absolutely push 100W+ and make your head ring, but you can't turn them up that loud, its just too loud.
So conservatively you need maybe 20-30W for each speaker of your surround system.

A buddy of mine has a 40W fender (forgot what vintage model) and you can't even get close to it, its just too dammed loud.

So don't worry! 50W per channel is plenty to make you deaf :P

Heck, if I ever get around to making an 18W practice amp I'm sure turning it up half will be plenty loud.

Steve Conner

Fri Mar 03 2006, 10:55AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Nice speaker cabinet hazmatt!

What is it, a 2x10?

It's a well known fact that audio amplifier ratings are inflated to impress customers. Better quality amps might say "2x 400W RMS" on them, but even so, it's understood that the duty cycle of music applies. What this means is that the amp can theoretically output a continuous sine wave at its nameplate power rating, but will go into thermal shutdown (or catch fire) after a minute or so.

Tube musical instrument amps are famous for being loud. Mostly they really can output the amount of RMS power shown on the nameplate, continuously. To get a distorted sound, they are usually overdriven to the extent that they put out considerably more than rated power. And they are usually used with high efficiency speakers that can put out an ear-bleeding racket with a relatively low power input.

HV Enthusiast

Fri Mar 03 2006, 12:29PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Or on the other side of the spectrum, I have an ORION HCCA amplifier which is rated for 100W, but is able to put out 800W (rms) into a 1/2 ohm load.

Steve Conner

Fri Mar 03 2006, 01:10PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yea, but surely it can only do that for like 5 seconds before it explodes? What manufacturers do is aim to get the "Biggest number on the nameplate per dollar spent on components". So they wouldn't sell it with a 100 watt nameplate if they thought it could deliver more than that reliably.

I think the worst thing is these computer speakers that produce "2000W PMPO" from a 10 watt wall-wart power unit. They probably wouldn't make 2000W if you fired them from a railgun at Mach 9.

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