Amp/Cab compatibility

[geilerbass]

I've searched around on here and elsewhere for information regarding amp/cab power ratings, ohmage and their associated compatibility and have read a great deal on the subject, but haven't been able to figure out the answer to my specific questions.

I have a 350W RMS (700W peak) Trace Elliot AH350SMX head, with the 350W rated at 4 ohms (it's minimum impedance). Currently I run it through a David Eden D210T, which has an impedance of 4 ohms and is rated at 250W RMS. So far, I've never had to put the amp particularly loud, since I've always played small venues and the rig has almost exclusively been for on-stage sound only, so the sound has been fine.

However, it looks as though I could be playing some bigger venues in the future, with a requirement for more onstage sound and so I have three questions.

1) Am I likely to kill my Eden cab if I have to push the output up on my head, to achieve louder volumes? Obviously there will come a point where it is driving the cab with more than 250W RMS and will definitely peak higher than that.

2) If I were to get a replacement cab (say a 4x10) what is a sensible power rating to go for?

3) Most decent cabs that I see available (Mark Bass and Eden for example) seem to be rated at 800W. I've read that pushing a lower rated amp to it's limits when driving a much higher rated cab can cause damage to head and/or cab. Is this true? And if so, would this likely be a problem for me were I to keep my head and get a cab rated 800W at 4 ohms?

I know there are so many threads/queries regarding power ratings, so apologies in advance, but despite much searching I can't find any conclusive solution to my problem.

Many thanks in advance.

[bass_ferret]

Have you looked at the articles in the basschat wiki?

[geilerbass]

Yes, that was the first place I looked, though there's nothing there to give me a conclusive answer. Am I right in thinking that this is not an exact science and therefore, I'm going to have to rely on luck to an extent? I really doubt that if I were to get a new cab, I'd have the opportunity to try it out with my amp.

Based on the Wiki it looks as though I would need a cab that takes 500W RMS at 4 ohms. I haven't seen any cabs at this kind of rating from any of the main manufacturers, so that's why I was enquiring as to whether I'd likely get problems with a lower or higher rated cab.

Edited May 15, 2008 by geilerbass

[lowhand_mike]

as far as i understand this you would need to go for the higher rated cab. but where the problem of breaking the head or cab comes in is IF you tried to get the full power out of your head into the cab, i.e. turning it up so that it started to clip. but just because you have the ability of the higher cab to handle say 500w doesn't mean i can handle a signal clipping at 350w, think this is due to spikes in the sound which no drivers could handle.

i am going to assume you just want the one cab, as you could get round the problem by having 2 8ohm cabs rated at around 300-400 which when used together would drop the ohms to 4 which would give you your full 350w. for example an ashdown abm 2x10 cab is rated at 350 watts but is an 8ohm cab so used on its own it would comfortable handle the 200+ watts your amp would put out at 8ohm, say you added another 2x10 your amp would then be putting out up to 350watts and the cabs would handle that.

basically (and please correct me if i am wrong cos i'll be learning something) if you do get a 650watt 4 ohm cab it will work fine so long as you dont crank it to silly settings.

Edited May 15, 2008 by lowhand_mike

[bass_ferret]

Using a 250w cab with a 350w amp would be fine if you follow the golden rule - if it starts distorting turn it down. The problem comes when you start using effects that dramatically alter the sound, with loud guitars and drummers, and you dont hear the distortion until it too late.

[MythSte]

In all honesty, Id look at it like this.

The Eden cab you have is a quality cab, i wouldnt be afraid to push it a bit as i'd expect a quality cab to be able to take a bit of push. As long as you use your ears to listen out for any distortion your on your way.

[BOD2]

You can happily drive your 250W cab with a 350W amp up until the point where you start to hear unexpected distortion. That's the limit that you will reach at some point, although the volume at the point could only be determined by trial and error.

If you expect to reach that point then you'll need higher powered speakers. Because your current cab is rated at 4 ohms, adding another 4 ohm cab would give a load of 2 ohms. If your amp cannot drive 2 ohms, then you would have to replace the cab, rather than add another one.

There is NO PROBLEM in driving an 800W cab with a 350W amp as long as you are sensible. By "sensible" I mean if you hear the amp distorting like crazy because it's being overdriven beyond its limits you simply turn it down a little. All sensible players who care about their sound would notice this long before it reaches that point.

The articles you've seen indicating that damage can occur refer to hifi speakers and amps and NOT bass/guitar speakers and amps which are designed tio handle quite different frequency ranges.

You can play through virtually any combination of different powered amp and speakers as long as you listen to the sound and control the volume accordingly.

An 800W cab with a 350W amp might seem a little excessive, but it will work fine and if you ever change the amp for a higher powered one in the future then the cab will be able to cope ok.

[geilerbass]

Thanks for all the advice!

Again, I know people find this subject a real bore - I've read through numerous threads about ohmage and power, both here and on talkbass, but I've not really been able to get my head around it.

It seems the general advice is: don't push your amp too far and listen out for distortion.

I'm pretty sure I've run my rig with both gain and volume on about half and had plenty of volume with no distortion. I don't really have room for another cab at home, so I think I'll stick with this set up until I notice that it becomes a problem. Then you might be seeing an Eden D210T appearing in the classifieds here...

Edited May 15, 2008 by geilerbass

[BOD2]

[quote name='geilerbass' post='199391' date='May 15 2008, 11:00 AM']It seems the general advice is: don't push your amp too far and listen out for distortion.[/quote]

That's it exactly.

You won't go far wrong with that advice.

[lowhand_mike]

what BOD2 said was what i wanted to say but my numpty brain couldn't articulate the words correctly.
but yeah use your ears and be sensible with the turny knobs

[MythSte]

Oh, and a priceless bit for advice for anyone worried about pushing there cab;

If you need more bass/mids/treble etc DONT BOOST, cut everything else and turn the volume from there. wont suckup watts that way! (Im not sure where i heard that, or even if i did indeed "hear" it at all, but it works!)

[lowhand_mike]

nice bit of advice, noticed something along those lines on me combo, when you up the bass/mid/treble controls the vu meter goes up too so you have to back off the gain (yeah the vu meter does actually do something )