#1753240 - 05/18/07 01:15 AM
Hlep with speaker problem?
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RefuseWinst
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Registered: 05/18/07
Posts: 2
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I was looking around online for some help with the problem I'm having, but couldn't find any info. Hopefully someone here can help out...
A few years back I bought a Fender M-80 160 watt bass head and an old Peavey cabinet. I don't know what the model number is (or if there even is one) of the cabinet, but it's an old cabinet with a rear-facing speaker. It's designed for an 18" speaker, but the person that sold it to me had replaced it with a 15".
At the time I bought the equipment, I wasn't playing with anyone, and it ended up sitting in a garage for a couple years. At the beginning of the year I started playing in a band again and got it out. Before long the head stopped working. I replaced it about 3 or 4 weeks ago with a brand new 700 watt Peavey tour series. Because of the design of the cabinet making it difficult to get at the actual speaker, I foolishly procrastinated checking the wattage of the speaker in the cabinet. I played with this setup for a few weeks without any problems.... that is, until tonight. At the beginning of our third song, my sound just dropped out. Nothing. I did the usual run-through of checking all the leads, pedals, etc. Nothing. At this point I was starting to think it was the new head... well, it's under warranty at least. But just to check I ran our PA to my cabinet to see if I got a signal from the speaker. I didn't.
I started pulling the cabinet apart to get to the speaker. As soon as I pulled off the panel to access the speaker, a puff of relatively thick smoke billowed out from where the speaker sits, and there was the distinctive smell that something had burned. I pulled the speaker itself out and inpected it, but it looked fine and I couldn't find any black or burned areas on the surface. I also checked the input jack just to be sure and it looked fine. All connections checked out. It seems that the speaker itself had apparently burned out on the inside somewhere.
I'm going to buy a replacement speaker before our next practice, but I'm wondering if anyone can tell me what caused this, so I can avoid it happening again. When I got to the speaker, I saw that it was 4 ohms and 600 watts. My amp is 700 watts, the speaker output says 4 ohm minimum, and I had both pre- and post-gain just under 5 (halfway) when it burned up.
Any ideas or suggestions? I have to admit I don't know a whole lot about this kind of stuff, but I thought a speaker would just blow (or at worse cause damage to the amp) instead of the actual speaker burning out!
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#1753745 - 05/18/07 06:42 PM
Re: Hlep with speaker problem?
[Re: RefuseWinst]
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GeoffB
MP Hall of Fame Member
Registered: 11/05/04
Posts: 7285
Loc: UK East Midlands via Scotland
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Sounds like your voice-coil melted.
Happens.
G.
_________________________
"When the power of love overcomes the love of power the World will know Peace": Jimi Hendrix
Frank M:Back in the day you could have a trio with two people.
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#1754608 - 05/21/07 12:03 AM
Re: Hlep with speaker problem?
[Re: GeoffB]
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RefuseWinst
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Registered: 05/18/07
Posts: 2
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I got the same answer on another forum too, that's probably it. Thanks! I ordered an 800 watt 18" 8ohm Eminence yesterday. Hopefully that will do that trick. I don't think the head was damaged.
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#1756674 - 05/24/07 08:23 PM
Re: Hlep with speaker problem?
[Re: RefuseWinst]
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paully
Platinum Member
Registered: 05/25/04
Posts: 1062
Loc: Northern New Jersey
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A speaker is a lot like a transformer, in that it has insulated wire coiled to form an electro-magnet. What actually happens is the speaker coil gets current from the amp on each cycle. The magnet repidly pulls the paper cone to a new location, then releases it when the current reduces.. resulting in sound. The by-product of this current draw is heat. This is normal. You can actually burn your hand by touching the magnet of a speaker that has been cranked.
Over time, the heat can cause the winding wires' insulation to become hard and brittle. Eventually the insulation can break down and short to the next winding. When that happens, the speaker draws even more current, because the the impedance drops(due to the shorts), and things get even hotter. Eventually there is a total meltdown. Smoke(the insulation burning) and/or a break in the wire(no sound) is the usual outcome.
FWIW, the new 8 ohm speaker should work fine, and it won't draw the full rated 4 ohm power of your amp. It should last a long time.
Good luck, Paul
_________________________
WUDAYAKNOW.. For the first time in my life, I'm wrong again!!
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