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Blowing Speakers


73 P Bass

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Let me start off by saying, yes, I did a search.

I've blown two speakers in two different cabinets in the past 4 months.

I have a SWR 350 head that I usually use with either a SWR Goliath Jr. III (4 ohms 350w), or an Avatar B210 (4 ohms 600w). Rarely I'll uses both together (the head is rated at 450w @ 2 ohms).

Both times I was not pushing the amp, and for that matter I usually try avoiding lighting up the pre-amp, or limiter light. I know it is widely believed you should "over-power" cabinets, although SWR's website says the contrary.

I've been fortunate that both cabinets were under warranty, but I don't want to push my luck.

Could something be wrong with the amp? Is there some kind of service that needs to be done? Or am I just having some bad luck with speakers?

"Start listening to music!".

-Jeremy C

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Wish I could help you better, but this is that long distance amp technician thing all over again. Is there nobody nearby you can trust to diagnose with actual test equipment and an educated ear?

 

I'll tell you this: I haven't blown a speaker in ANYTHING for many years in spite of usually having up to 3dB or moe more power (DOUBLE) than the cabinet(s) being driven. But I am very aware always what type of signals are going through the gear as far as transients, freq response, etc and typically have speakers with pretty high honest RMS ratings. I can also usually hear flakiness in gear farther up the signal chain.

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Since I'm not very far into big cabs and heads with my bass I have to relate to my stereo knowledge. My speakers are rated at 250w @ 8 ohms. My stereo is rated at 100w RMS @ 8 ohms. Your speakers, which essentially the same as a cab, should be able not just to handle the max RMS power, but the peak power also. And peak is what will kill you.

 

The actually amount of amperage running through the cabs is inversely proportional to the resistance of the speakers. Which is why it's so important as to whether or not you're connecting the speakers in parallel or series. Series gives you higher resistance and therby lower amperage.

 

Of course.... I may remember this all wrong. :)

 

David

"Life's journey is not to arrive at the grave safely in a well preserved body,

but rather to skid in sideways, totally worn out, shouting "&$%^, what a ride". - Doug Berlin

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if i read this right, your amp is 350 watts and your cabs are rated for 600. It seems your keeping your gain down (don't go over half) and don't turn your volume up over 3/4 (and this still may be pushing it)

 

You could be clipping the speaker, which is not too good for it, and will blow it. This happens when the speaker needs more power than the amp can deliver and causes it to distort the signal, damaging your speaker. This will blow speakers.

 

The chances of this happening are even greater if you have active pickups on your bass, and crank any of them all the way up.

 

You may just need more power! (hey, any excuse to get GASy :) )

Check out my work in progress.
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I think there's probably something wrong with your amp. If you're not clipping the power amp (in which case the limiter would come on) and you're not extremely boosting the lows (are you?) then there's no reason your speakers shouldn't be fine with that much power.

 

There's no such thing as 'underpowering' - the damage is caused by asking an amp to deliver more volume than it's capable of, so it ends up clipping and putting out up to twice its rated power (whilst also losing its damping power so failing pull the cones back when its pushed them forwards) which thus overpowers the speaker.

 

This tends to happen when using underpowered amps, hence the misnomer 'underpowering'.

 

Alex

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As a general rule...

 

Having considerably more amplifier power on tap than your speakers are rated for, is actually a much safer scenario than having less amp than the rated speaker power handling. It's not power or power peaks that usually damage your speakers. It's almost always the squared-off wave form signals created by amplifier 'clipping'. And with a two ohm load, your amp's output gain doesn't have to be cranked up very much to approach clipping in a gig situation.

 

There is one other rare problem you may be experiencing...

 

Sometimes an amp can develop the kind of problems which produce huge subsonic bursts. I have seen this several times with high-power stereo equipment, but never actually with a bass amp. The effect of these subsonics is to cause the speaker cone to move forward suddenly to the point of over-excursion.

 

Most likely your problem is simply lack of power, however. Time to move up to an amp in the 700 watt range.

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Not neccessarily needing a bigger amp {though I think that my rig says what I think about this ; } Hard to say without being at the gigs.

 

It's entirely possible to have a defective component or two (even an intermittent one) that at opportune moments does the bad thang to the cabs. That's why it's a lot smarter to find and get to know someone in the local area with tech cred and honesty and GET THEE HENCE!

 

Here's one of the things that get jettisoned in heads or combos that REAL power amps always have: POWER and LOAD PROTECTION. Real power amps besides having better specs in every regard also do a lot to prevent speaker damage.

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If you're overdriving the final you'll get clipping. This can fry your amp and you'll definitely hear it. Massive distortion. Hopefully you're not introducing distortion so that you can hear the amp distort. :)

 

This usually happens when you want louder and the amp doesn't have anything left.

 

If you pour more into the speakers then they can handle you can damage the speakers and when they fail you can fry your amp because of the impedance change.

 

However if you're blowing speakers and not trying to knock down walls then it does sound likely that the amp is at fault.

 

David

"Life's journey is not to arrive at the grave safely in a well preserved body,

but rather to skid in sideways, totally worn out, shouting "&$%^, what a ride". - Doug Berlin

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