Underpowering cabs

[ML94]

As the title says I'm interested in knowing what could happen if I underpower my cabs. At the moment I have a 600w Genz rig, both at 300W and head being a powerful 600w amp. What if I powered my 600w cabs with a 500w amp.

What would the consequences be ?

[Chrismanbass]

slighly less volume than the cabs are able to produce tbh thats about it

[ML94]

So nothing blowing up right?

[discreet]

If both cabs are 8ohms and your amp gives 500W at 4ohms then you potentially have 500W on tap... which you are unlikely to use in practice as it will be very loud. And of course... wattage is no measure of loudness, it depends on the sensitivity of the cabs and a whole load of other stuff I don't understand. But you are unlikely to do any damage, if that's what you're worried about.

[Chrismanbass]

na shouldn't do thats only if you over power speakers so for example using a 900w head on 700w cabs tbh using your ears is the best bet the speakers will fart out if your head is too powerful

[TimR]

The power figures are fairly meaningless.

The speaker power is just the electrical power the speaker coils can dissipate before they melt.

The amplifier power is a measure of the current it can deliver before the transistors release the blue smoke.

The danger of having a big amp driving small speakers is you can either overheat the coils or more likely the speakers will move too far (called over excursion) and break mechanically. You will hopefully hear this happening.

The danger of having a small amp is the same but the added danger is that the amp could overheat before either of those things happen.

You always need to listen carefully for distortion when you use gear and recognise when it's doing damage. However, not all distortion is bad, depends how long and how hard you drive everything.

Edited November 30, 2013 by TimR

[BassTractor]

Another way of putting it is that it has the same effect as not totally opening the volume pot on the 600W amp. I guess you are somewhat used to [b]that[/b] at least.
So IOW the word "underpowering" is [b]not at all[/b] appropriate in the situation as you describe it (bar maybe some very, very special cases, but I'm not torturing my brain to make one up right now).

[JTUK]

Also want more cab power than amp power.

Bass is brutal on speakers so I want the cabs pushed but not overdriven.
Watts are not the garauntee that a cab will handle what is thrown at it...only a
an indication...IMO.

[bluesparky]

I appreciate threads like this, even though I read as much as I can about amps, power, impedance and figures etc i still come across a fact or twist in the technical theory that I don't understand.
I love the fact there is a wealth of knowledge out there from Basschatters who are willing to help out.
Cheers.

[steve-bbb]

[url="http://barefacedbass.com/technical-information/understanding-power-handling.htm"]this[/url]

Edited December 1, 2013 by steve-bbb

[Musky]

AFAIK the whole under-powering thing comes from the PA world, where they tend to use much larger amps than the speakers can handle. The reason for this is that clipping can damage tweeters. This isn't a problem for bass units where over excursion is a far bigger problem, and big PAs are usually used in conjunction with limiters to prevent just this.

So no, using a 500w amp with 600w speakers won't be a problem for you.

[chris_b]

What do you mean by underpowering? You can't hurt cabs by putting[i] less [/i]volume into them.

You have 300 watt cabs so putting 250 watts into each is ok, but are you running your amps flat out? If you're playing at "normal" semi-pro band levels you're probably putting 60-100 watts into each cab.

If you change amps you'll probably be playing at the same overall volume level, so your amp might be working slightly harder (going from 600w to 500w) but the cabs won't see any difference.

[4 Strings]

Its a bit like saying 'my car can do 120mph, will I cause damage if I drive it at 100?'

To carry on the car analogy, overpowering would be like putting a lorry engine into a go-kart chassis. Apply any real power and it will twist it into a knot.

Underpowering would be like putting a go-kart engine into a lorry. It won't have enough guts to really get it going.

You're asking about putting a 1300cc engine in a 1500cc hatchback. It'll be fine, just would work a little harder if you pushed things to the limit.

[Guest bassman7755]

In summary its a bit like asking "will it damage my high grade 180mph tyres if I use a lower powered engine that can only get me to 100".

Edited December 2, 2013 by bassman7755

[BassTractor]

Wow! One or two more analogies and this has to be moved again - now to the Humour in Music forum!

[TimR]

Analagies rarely work.

As I wrote above; Watts are fairly meaningless.

[Bill Fitzmaurice]

[quote name='ML94' timestamp='1385849982' post='2292925']
As the title says I'm interested in knowing what could happen if I underpower my cabs. At the moment I have a 600w Genz rig, both at 300W and head being a powerful 600w amp. What if I powered my 600w cabs with a 500w amp.
What would the consequences be ?
[/quote]For the woofers, nothing. If you have tweeters they can be damaged by too much harmonic content, and excess harmonic content is what's created when an amp (or any device in the signal chain, including fuzz pedals) is pushed to clipping. You're far more likely to push a smaller amp to clipping than a larger one, and the smaller it is the more likely that scenario.

[flyfisher]

[quote name='TimR' timestamp='1385852456' post='2292968']
The power figures are fairly meaningless.
[/quote]

This^ . . . .
(particularly when comparing 500W and 600W and considering the wide variation in how such things are specified)



[quote name='BassTractor' timestamp='1385852535' post='2292971']
Another way of putting it is that it has the same effect as not totally opening the volume pot on the 600W amp. I guess you are somewhat used to [b]that[/b] at least.
[/quote]

. . . . and that^

(I'd bet everyone here has 'underpowered' their cabs at some time, probably most of the time, but I've not seen the topics full of damaged speakers ).

[Bolo]

[quote name='Bill Fitzmaurice' timestamp='1386021302' post='2294814']
For the woofers, nothing. If you have tweeters they can be damaged by too much harmonic content, and excess harmonic content is what's created when an amp (or any device in the signal chain, including fuzz pedals) is pushed to clipping. You're far more likely to push a smaller amp to clipping than a larger one, and the smaller it is the more likely that scenario.
[/quote]
And this.

The difference between 500W and 600W is nothing to worry about.

[4 Strings]

[quote name='BassTractor' timestamp='1386007202' post='2294556']
Wow! One or two more analogies and this has to be moved again - now to the Humour in Music forum!
[/quote]

What about putting Amir Khan in the ring with Mike Tyson?

[flyfisher]

[quote name='Bill Fitzmaurice' timestamp='1386021302' post='2294814']
For the woofers, nothing. If you have tweeters they can be damaged by too much harmonic content, and excess harmonic content is what's created when an amp (or any device in the signal chain, including fuzz pedals) is pushed to clipping. You're far more likely to push a smaller amp to clipping than a larger one, and the smaller it is the more likely that scenario.
[/quote]

While not disputing tweeter sensitivity to excess harmonic distortion, is this really a practical issue with modern gear?

Is the THD figure for modern amps really so excessive these days that it could damage a properly rated tweeter, even at full volume?

Also, do cab manufacturers not include any simple filter protection for their tweeters? It would be fairly easy to roll off the frequency response above, say, 25khz - or perhaps this is not necessary because of the above point?

[Bill Fitzmaurice]

[quote name='flyfisher' timestamp='1386063296' post='2295071']
While not disputing tweeter sensitivity to excess harmonic distortion, is this really a practical issue with modern gear?
Is the THD figure for modern amps really so excessive these days that it could damage a properly rated tweeter, even at full volume?[/quote]The THD figure you see listed for amps is what's used as a benchmark when measuring the amp output. That might be anywhere from 0.1 to 1% THD on average. By no means is that the limit to the THD that they can produce. If you crank the amp, or boost the signal level going in to the amp, you can easily reach 20% THD and more. That's how guitar players get their tone, and for that matter why guitar amps never use tweeters, because they'd never last through even one gig. Bass players tend to use amps large enough that they don't have to crank them to get loud enough, but not all do. And bass players who use distortion devices tend to cook their tweeters.

[quote]Also, do cab manufacturers not include any simple filter protection for their tweeters? It would be fairly easy to roll off the frequency response above, say, 25khz
[/quote]25kHz isn't the problem. Everything a tweeter reproduces is harmonics. A tweeter normally sees only 5% of the broadband power content. That means a tweeter in a 400w rig normally will never receive more than 20w. When you go from 5% THD to 15% THD the level of the harmonics goes up by 10dB. The tweeter that normally is called on to handle 20w now might be gettting 200w. Magic smoke ensues. Woofers aren't phased by the increased harmonics since they would be able to handle 400w anyway.

[seymourfluid]

I run a 600w Mesa Boogie M6 Carbine through 1200w of cab, a 600w Powerhouse 1x15 and a 600w Powerhouse 2x12.

I'm not sure how that helps but I'm happy.

:-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-)

[Conan]

Presumably when you run your amp at anything less than full volume (with lots of low-end EQed in) you are underpowering your cabs....

It's kind of meaningless isn't it?