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Amp speaker questio...
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Amp speaker question?

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Noble Member
Joined: 17 years ago
Posts: 1882
Topic starter  

There are 2 different scenarios for a "broken" speaker.

1) electrical failure - if you have an ohm meter (or multi-meter) you can measure the resistance of the speaker coil. It should be 4 or 8 ohms (more-or-less) If it's blown, there should be infinite resistance (an open circuit)

2) mechanical damage - visually inspect the edges of the cone for damage. Also GENTLY place your fingers on the cone evenly around the edges of the center dome, and GENTLY push a small amount. Listen to see if the voice coil is scraping on the slot in the magnet. If you hear a slight "fingernails on the chalkboard" kind of noise, you have a failed speaker.

Replacing the speaker isn't that difficult a job if you are experienced using tools.
If you aren't, then skip everything I have said, and take it to a shop.

I wrapped a newspaper ’round my head
So I looked like I was deep

Wes Inman
Illustrious Member
Joined: 19 years ago
Posts: 5582

Look on the back of the speakers. The most important thing is to match the impedence or ohms. Most speakers are wired in parallel, but not always, sometimes they are wired in series.

You also have to know your amp's minimum ohm operation. If the back of your amp says, "40 watts @ 8 ohms minimum" or something similar, this tells you the minimum impedence. You do not want to go under this number. If your amp is designed to run at 8 ohms and you put a lower impedence load like 4 ohms it can cause the amp to overheat. Ohms is a measure of resistance. The lower the ohms, the lower the resistance which means more current flow through the amp. Too much current is kinda like turning your amp into a toaster. Don't do that.

Most guitar speakers are 8 ohms and 16 ohms, occasionally 4 ohms.

Wired parallel:

Two 16 ohms speakers= 8 ohms total load
Two 8 ohms speakers= 4 ohms total load
Two 4 ohms speakers= 2 ohms load (this load is very doubtful)

Wired series:

Two 16 ohms speakers= 32 ohms total load (very doubtful)
Two 8 ohms speakers= 16 ohms total load
Two 4 ohms speakers= 8 ohms total load

So, you want to replace the blown speaker with a speaker that matches the ohms or impedence, this is the most important factor. You can use two different model speakers in a combo amp, but it is probably best to get an exact match if possible.

This may sound like a funny analogy, but your speakers impedence is kinda like the exhaust and muffler system on your car. Your exhaust system on your car does more than just keep the engine quiet. It also transfers heat from the engine cooling it, and it pushes back on the engine creating compression and power.

Your speakers are kinda the same. If your speakers total impedence or ohms is too low, then too much current flows through the amp which causes it to overheat. When you match speaker impedence to the amp it operates at it's best. When you use too much impedence (like 16 ohms on an amp designed to operate at 8 ohms), this will rob your amp of power. It is kinda like driving with your foot on the brake pedal.

Hope that helped.

If you know something better than Rock and Roll, I'd like to hear it - Jerry Lee Lewis

Illustrious Member
Joined: 21 years ago
Posts: 5108

Who would've guessed that q-tips could solve amp problems??? :D

Well we all shine on--like the moon and the stars and the sun.
-- John Lennon