Re: Speaker Dilemma


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Posted by Mickster on January 16, 2001 at 17:00:35:

In Reply to: Speaker Dilemma posted by Rich Laird on January 16, 2001 at 11:45:08:

: Ok…somebody out there must have some answers to my little problem. I’m probably making this more complicated than it is, so if you feel like slapping me around – I don’t blame you. But since you can’t do that over the internet anyway…here goes:

: It’s time to buy a speaker cabinet but I’m not sure what to get. My amplifier – a Peavey Century - isn’t really that powerful (says “100 watts” on the back)…but I want to get something fairly good and well-matched….and have confidence that I’m not going to overpower my new speakers and blow them out (very depressing….brings back too many memories of cheesy garage blues bands). But I also know that if I get a cabinet that’s too big, my amp will just wimp out.

: I always thought that if an amp is rated 100watts RMS, then you probably want speakers rated for about 200 watts. But I checked out a 200 watt cabinet (2x10 with a tweeter) at a music store the other day and plugged a 50 watt Fender Bassman into it to see what it sounded like. Am I crazy? The sound was breaking up on low Es, even with the amp set at about half volume. So now, I’m beginning to think that I really need to get something rated for like 300-400 watts. Would that be a reasonable match for my 100 watt amp?

: If that’s true, then what I need is probably a 4x10 – maybe with a horn or tweeter in it – those usually seem to be rated about 300-400. That’s sort of what I was thinking in the first place…maybe it comes down to going with your instincts and what actually sounds good and forgetting about watts, and RMS ratings and all that. Any thoughts?

: Also, it says “4 ohms” on my amp. Does that mean that I absolutely have to get a 4 ohm cab? Would an 8 ohm cab also work? Is there any advantage of one over the other? Low-impedance usually means lower noise…does any of this ohm crap really matter?

: One more thing while I’m indulging in this over-neurosis (I always get this way when spending money is involved): It also says on the back of my amp that “outputs are parallelized”. There’s two speaker outputs….does that mean that if I plugged each one into a separate cabinet that I would be getting 200 watts? Is that why the amp says “Century 200” on it?

Hey Rich, what's up?

First of all, 100 watts is a medium sized amp.(power wise)Rather than worry about matching watts to watts(amp to speakers) it's more important to get
a speaker or cabinet with a high efficiency rating. The more efficient the
cabinet is, the louder it will sound with any given amp. Today's cabinets
are very efficient compared to amps of years ago. That 50 watt bassman sounded
like it was breaking up at half volume because of two reasons:
1) There are exceptions to this rule, but, in general once you go past the 12
o'clock position on the volume control, you're starting to enter the amp's
clipping zone(the area where it will no longer produce a clean signal) as you
turn the volume higher after this point, the amp has less and less "headroom",
or reserve power. As the amp keeps trying to put out more power, it soon reaches
its rated power. A 100 watt amp can put out double or even quadruple its rated
power, but, not cleanly.(without distortion) When you blow a speaker, it's
usually because you're sending a distorted signal to the voice coil, which
can only really use a clean signal. The 50 watt bassman was "trying" too hard,
and that's the distortion you heard. If you had switched to say, a 400 watt head, you would have heard no distortion because the more powerful head would
have no problem putting out the power needed for the volume you wanted. Think
of an amp's watt output like a car engine's horsepower output. Same idea.
2) The lower a frequency you try to amplify, the more power you need to keep
a consistent volume. This is because human hearing can't hear very low or very
high frequencies well. This is why you need 3 or 4 times the power for a bass
amp to keep up with a guitar amp. A guitar's range is almost all midrange, which is what we hear best.

Getting back to volume; 100 watts will give you just so much volume and no
more. So even if you buy a cabinet that can handle 400 watts, without 400
watts of power going into it, it's not going to give you the benefit(volume)
of its large power handling capacity. A car of a certain weight will go faster
with 400 hp than with 100, and it will maintain a higher speed more easily with
the bigger engine.

Which bottom should you buy? I would suggest a good 1x15 or a 2x10. You can
go bigger, but remember: It will sound fuller with a bigger bottom(4x10 or
1x18)but not necessarily louder. If you're playing a 5 string, I'd get the
1x15. Maybe even a 2x15. Try bringing your head to the store, this way what
you hear is what you get. If you settle for slightly less volume, most of the
problems go away.

As for the 4 ohm indication on your amp, this is the lowest you should go.
You can go higher to 8 ohms, but the amp was made to work best at 4 ohms.
If you went to a 2 ohm load, and cranked the amp, you'll fry it. Ohms are
resistance. Think of them as gears in a car's transmission. Your car may go
100 mph in third(top) gear, but, what would happen if you tried that in first?

Bottom line: 100 watts is a good size amp.(I have one) They just don't put
out deafening volume.

Hope this helped man.
Mickster




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