Speaker ratings

MattBanshee

So, I've spotted a nice, compact bass cab (Ashdown VS112) locally for a very cheap price, rated at 150W 8ohm. I'm tempted as the rehearsal studio I use doesn't provide amps, and my current cab weighs an absolute ton.

I currently have a Marshall 1x15 250W 8ohm (sidewinder) as my only bass cab, and my amps are an Ampeg PF350 (250W into 8ohm) which I use for rehearsal and an SVT450H (also 250W into 8ohm, 450W into 4ohm) that I gig with. I was hoping to be able to use the Ashdown 1x12 with the PF350 for practice, and the SVT with the Marshall (or both cabs) for gigs.

Question is; if I put the PF's 250W 8ohms into the 150W 8ohm speaker, how likely/quickly will I blow the speaker? The volume on the PF is usually set at 60-70% at practice (currently into the Marshall) depending on the size of the room.

ecc83

IIRC ICBM has said THE most common thing to fail in bass rigs is the speakers and they presumably WERE supposed to be the correct rating?

Make of that what you will!

Dave.

MattBanshee

Took a punt on it, as it was so cheap. Read up on speaker info on Barefaced Cabs' page which reckoned that a speaker should be fine up to double RMS or something. The PF350 has a limiter switch too to prevent spiking, which I have engaged anyways.

Worst case, if I pop the speaker, I'll get a high rated neo for it.

mart

@ecc83 is right, but for home practice you’d have to be really going some to blow a 150w speaker. If it’s band practice with a drummer, then the risk is much higher.

I would not take Barefaced’s comments as a guide to how an Ashdown cab would behave.

ICBM

Ashdown's OEM speakers - especially the blue-cone ones - are quite optimistically rated, and there's a significant chance of blowing it with a 250W amp at band volume. Actually, running with the limiter engaged probably increases the risk, since you'll be able to get a higher average power output without it being obvious.

Barefaced's advice also assumes that the sound is strictly clean - the idea of running a more powerful amp with a lower-rated speaker only works then. Any overdrive/distortion/fuzz at all - even from a pedal - and the opposite applies, like a guitar amp.

If you do blow it, I would replace it with a minimum rating of 300W and preferably higher - luckily this doesn't have to be expensive, the Eminence Delta 12A is around £70 and rated for 400W. (Although it's also heavy.)

ecc83

mart said:

@ecc83 is right, but for home practice you’d have to be really going some to blow a 150w speaker. If it’s band practice with a drummer, then the risk is much higher.

I would not take Barefaced’s comments as a guide to how an Ashdown cab would behave.

Agreed IC but 'it'appen as was the case very recently when a guy on another forum blew his 150W rated Celestion hi fi speakers with a 400W amp. The setup had been working as studio monitors for a couple of years it seemed but a series of bad consequences buggered them.

Corse! With s'state amps you can always fit fuses!

Dave.

ICBM

Yes, the problem with having the amp more powerful than the speaker rating is that it gives no margin for error - if the amp does go into distortion or even just continuous full power rather than an averagely-weighted music programme signal, the speakers are toast.

The only way to prevent it entirely is to have the speakers capable of taking the full distorted output of the amp, which for guitar speakers is usually around twice the clean power, but for a PA/monitor speaker will be much higher to avoid overpowering the tweeter, probably at least four times - unnecessarily costly for almost any purpose*.


(*Except rehearsal room PAs operated by musicians .)

MattBanshee

Update:

Got the cab, looked inside and it had an Ashdown Blueline speaker inside, marked as 200W 8ohm. I expect that maybe they have underrated the cab slightly (150W) to account for unreliability?

Anyway, I ordered a 400W Eminence Delta from Lean Audio to go in it.

ICBM

MattBanshee said:

Got the cab, looked inside and it had an Ashdown Blueline speaker inside, marked as 200W 8ohm. I expect that maybe they have underrated the cab slightly (150W) to account for unreliability?

Probably.

MattBanshee said:

Anyway, I ordered a 400W Eminence Delta from Lean Audio to go in it.

Hope you're feeling strong .

MattBanshee

ICBM said:

MattBanshee said:

Got the cab, looked inside and it had an Ashdown Blueline speaker inside, marked as 200W 8ohm. I expect that maybe they have underrated the cab slightly (150W) to account for unreliability?

Probably.

MattBanshee said:

Anyway, I ordered a 400W Eminence Delta from Lean Audio to go in it.

Hope you're feeling strong .

It'll probably still weigh less than my Marshall 1x15 with Sidewinder, but will actually fit in the boot of my car!

MattBanshee

The Delta 12A has arrived; silly question - it has a rubbery plastic sleeve over the edge of the magnet. Do I need to remove it or leave it on?

ICBM

If it’s a closed-back cab you can save a tiny bit of weight by removing it, if you want. If it’s open-back I would leave it on, it protects the magnet from being chipped if you put anything in the cab.

MattBanshee

Thanks; it is a closed back cab bit tbh the weight is so minimal I'Il leave it on. Thanks!