Re: Amp Power vs. Speaker Power


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Posted by Mickster on January 29, 2001 at 14:11:18:

In Reply to: Amp Power vs. Speaker Power posted by Moyle on January 27, 2001 at 17:05:24:

:
: How much larger should an ampheads wattage be, compared to a cabinets wattage for full clear volume.

Hey Moyle, what's up?

First off, you can use almost any head with almost any bottom.There are however
a few rules you should follow. Let's first take the example of a more powerful
head with a lower rated bottom. O.K. The amp is 1,000 watts rms(a loose term
indicating roughly how much power it can produce cleanly before clipping,
which is the point where the amp starts to produce a distorted signal) the bottom is a typical 4x10 bottom rated at 600 watts. Just because the amp has
1000 watts DOES NOT mean it will blow the bottom apart. It simply means that
the amp *CAN* produce more power than the bottom can handle. If you run across
an amp with an output meter on it(my stereo has them) you'll see what I mean.
My stereo amp puts out 200watts/channel, and the speakers I have(Bose 501V)
can also handle 200 wattts/channel. This just happens to be a coincidence by
the way; I've had the amp a lot longer than I've had the speakers. Now, when
I'm listening to music, let's say The Eagles, to get low background level volume, the volume control is at about the 9 o'clock position, and the power
meters indicate the amp is putting out between .5 and 2 watts. If I turn the
volume control to 10 o'clock, a good listening level, the power meters show
between 5 to 50 watts. If I turn it up to 12 o'clock, the stereo is now very
loud, and the power meters usually peak at 200 watts, which I don't let them do.
If I see 200watts, I reduce the volume just a little, then the amp puts out
no more than 100 watts, and both amp and speakers are happy. Now, this is with
program music(regular music) played by a full range stereo system. It's basically the same with a bass amp/bottom, it's just that we're dealing with
only lower and midrange frequencies, as opposed to the full sound spectrum
of the stereo. The bass amp will do roughly the same thing as far as power
output in relation to the position of the volume control. At the 12 o'clock
position the 1,000 watt head will be putting out about 200-400 watts. Now the
bottom as we said can handle 600 watts, so we're still safe. If you keep increasing the volume on the head you'll soon reach the point where it will be
producing 600 watts or more which is the power handling capacity of the bottom.
The 600 watts the head is producing is clean power, because it's still within
the amp's safe operating range of "up to" 1,000 watts. This "clean" 600 watts
is fine with the speakers, because they're designed to handle this much power,
and most speakers can actually handle more than their rated capacity, although
you do this at your own risk. All these ratings are a standard Manufacturers
use to approximate power output/handling capacity. Now if we reverse the amp and bottom relationship, let's say a 200 watt head with a bottom that can handle 1,000 watts, at about the 12 o'clock volume setting, the amp will be
nearing it's power output limit, while the speakers can handle 4 times the power that the amp is capable of producing *cleanly*. You're much more likely
to blow a speaker from a lower powered amp that's "trying" to give more output
than it was made to produce, and is now putting out a distorted signal(which
hurts speakers) than a high power amp that's putting out a speaker's full power
handling capacity(or slightly more) but producing a very clean signal.

Also, an active bass will send a stronger to the preamp section of the amplifier, which will make the active bass louder at any given volume setting
as compared to a passive bass, which produces a weaker signal.

So... if you don't have power meters to check the output of a given amplifier,
use these two common sense rules: 12 o'clock on the volume means it's TIME to
stop increasing the volume, and: If an amp sponds like it's straining or
distorting, IT IS! Lower the volume. By the way, you can buy power meters at
an electrical parts supplier or even Radio Shack for about $30.00

Hope this helped,
Mickster

P.S. It always better to have more power than you need, but, then this brings
up the old money issue, not to mention that more powerful amps and bottoms
don't transport as well as smaller amps.


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