Randy Bass wrote:The 200-watt Ashdown would be absolutely fine with the SP212. The thing you want to avoid is turning the amp up all the way to full since the power section may be capable of hard clipping (I'm not entirely sure how it's designed). You could conceivably blow a 600-watt cab with a 20-watt solid-state amp if its' power section is distorting. If you can get enough volume out of the Ashdown without the volume on 10, it should be a suitable backup.
Hi there. Me again!
Agree with the first bit, not the second.
Blowing speakers is a complicated subject, with many different factors and different ways of doing it. But it is
always (in one way or another)
too much power which blows speakers.
When you push solid state ('s.s.') amps beyond their clean ratings into power section distortion (= at too high volume settings) they very quickly go into 'hard clipping' distortion. They simply can't put out a clean waveform beyond their rated power so the tops and bottoms of the waveform they then output are clipped off = distortion. (Valve amps clip more softly - the waveforms instead of being cut off flat are rounded off. Their 'soft clipping' distortion sounds much more natural and the power doesn't increase so dramatically quickly.) The problem with pushing s.s. amps into 'hard' clipping is that when you do they can
very quickly put out up to about double their rated (clean) power output. A hard clipped 200W s.s. amp for example will pretty soon be putting out up to about 400W. It isn't so much the hard clipping waveform itself which is bad for speakers though, it is the unexpected sudden increase in power, as opposed to the much more progressive 'squashing' of 'soft clipping' valve distortion.
A 200W s.s. amp really isn't likely to blow a (genuinely) 600W rated cab by simply overpowering it. Damage CAN happen, but not simply through sheer output wattage. See below
*! And with a 20W amp that
just won't happen!!!
So yeah, the 200-watt Ashdown would be absolutely fine to use with the SP212. If you push it too hard and hear nasty sounding distortion (like a tranny radio turned up too loud) just turn it down a bit! You'll want to anyway - sounds horrible!
FWIW you can't damage a speaker by 'underpowering' it by using a 'too low power rated' amp. That myth simply comes from the fact that any s.s. power amp cranked into distortion will far exceed its clean power ratings, so running a 100W amp into say a 150W speaker isn't safe if you crank it beyond its clean limits into output section distortion.
Since we are talking about
bass gear here, which is different from guitar amplification, there are a couple of things worth knowing.
For starters with bass the speakers 'thermal power handling' = the power the voice coil can handle (= the only wattage rating manufacturers normally give)
isn't usually the main limiting factor to what the speaker will safely handle!
Most of the power that goes to your speaker turns into heat. Well over 90% of it ends up as heat, not as sound energy. If the voice coil gets
too hot (= too much continuous power for too long) than it can be damaged. But that doesn't mean that a 100W rated speaker will die as soon as you put a signal of 101W into it. Or 150W. Or even 200W. What it means is that it can't take
continuous and sustained power levels above 100W. It is an 'average power' thing, and normally a voice coil won't sustain thermal damage from brief signals of even
several times its rating, as long as there are sufficient gaps between bursts of high power for it not to overheat.
This means that the peak power levels a speaker can handle are MUCH higher than its continuous average (RMS) rating.
BUT...
Putting out low frequencies at high power means a lot of cone travel. (Hit a big low bass note and you can see the speaker cone move backwards and forwards - quite a lot!) If the amp is set to put out a lot of low bass you may exceed a speakers mechanical limits and blow it,
even without getting anywhere near its thermal power rating!
This is called 'excursion limited power handling' (
*), and has to do with the speakers low frequency power handling. Some speakers, even of the same rms power rating, will have much higher low frequency power handling than others. Guess what, with bass amplification this tends to be much more of a limiting factor than the thermal power rating to what you can get away with.
If you want to know about that you need to look up things like 'Xmax' and 'Xlim' ratings, but basically Xmax is the maximum excursion a speaker can travel with less than 10% distortion (a
distance then!), and Xlim is the maximum excursion before actual physical damage happens. I've been reading up on this stuff a lot lately and used to think that you'd not really hear things happening there before they suddenly stopped happening. But while that
is true with most 'hi-fi' type speakers, most quality professional speakers apparently do have a much greater difference between these two figures so you will get some warning (in terms of audible distortion) before you actually destroy the speaker. There you go, live and learn.
Another thing to think about with bass cabs is that clipping distortion (yep, that stuff again) usually causes most power increase in the higher frequencies. This is due to increased harmonics being created (= harmonic distortion). This tends to blow HF tweeters so if running cabs with tweeters you want to be especially careful. Normally the HF component of your sound only needs a small proportion of the amps power, but the increase in power output at higher frequencies can be dramatic with hard clipping and tweeters if fitted will usually be the first thing to blow. So listen out for them having a hard time and if you hear them distorting
turn something down! Either the amp or at very least the tweeter itself if the cab is fitted with a separate tweeter control.
Main difference with guitar amps / speakers is that there you are mostly talking about mid range frequencies, not the high or low frequency extremes of bass amplification. (I know, people think 'electric bass' is all about bass frequencies, but it is actually a much more full range instrument than electric guitar. In fact electric guitar is almost all about the midrange frequencies, and bass signals can go both lower and much higher!) So for guitar the main limiting factor to what the speaker(s) will handle
is the thermal (RMS) power handling rating. Basically with guitar speakers you want to make sure you never exceed that so having speakers rated for double the amps output rating is in most cases perfectly safe.
Guidelines for bass are significantly different and as you see a bit more complicated. But whatever amp you are hooking up to whatever cab for bass the simplest answer is always to listen to your speakers! If they sound like they are in distress THEY PROBABLY ARE!
Hope that helps some.
Andy.