#1
So the speaker on my guitar amp blew out and I started using a 12 in speaker from a home stereo system as my speaker. Will this damage the speaker since it's not designed for the guitar frequencies? Thanks.
#2
Yep. It was not designed as an instrument speaker and will likely be killed. It is also probably pretty quiet as stereo speakers usually have a much lower sensitivity. Exceptions are JBL, Altec, EV and Klipsch which used very high quality speakers that were nearly indestructible.
"Your sound is in your hands as much as anything. It's the way you pick, and the way you hold the guitar, more than it is the amp or the guitar you use." -- Stevie Ray Vaughan

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#3
Your fine, it just might not sound the best.

What type of amp is it, you might find a used or even new guitar speaker that will work better for fairly cheap.
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#4
It really all depends on the amp,

I'm assuming here we are talking a little 10-15-20 watt combo into a fairly large (10" +) Stereo speaker like they were in the 80's, you will probably be okay, as long as it matches the impedance (usually 8 ohms), and you don't crank the amp up.

If it's high wattage, don't be surprised if the voice coil melts and it stops working.

If it's a tube amp....you're in for a lot of trouble....
- could burn out the transformer(s) due to excessive load trying to drive that speaker
- an impedance mismatch is bad for the amp and possibly the speaker too
- tube amps hit their maximum power rating pretty early on, you could be pounding a 15 watt 8ohm with a force for 16 ohms @ 100 Watts.
- I have heard of failing speakers catching fire, I'm pretty sure a Tube amp could induce that in some third hand Kennwood 12" high wattage speakers with the right amp
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#5
I'm using a 12" from a Pioneer CS-R 590 speaker tower. My amp is a cheap 20 watt solid state. I made sure the ohms were the same as the amp's previous speaker. Both are 8 ohms. I don't crank up the volume at home but I would like to have that ability if I ever wanted to jam with friends.
#6
I am an electronics engineer and have been playing guitar for years. Hi-Fi amps and speakers have been a hobby of mine and I have made my own guitar amps and speakers that have also served me well. Yes at times I have fed my guitar through a hi-fi amp and speakers.

In response to your question several things occur to me.


1. Power ratings for loudspeakers and amplifiers are notoriously hard to compare and therefore match safely. You can talk about rms continuous sine-wave power ratings or you can talk about peak power ratings and instantaneous music-power ratings and give the same amplifier or speaker a wide range of different ratings. You can talk about power output for a given maximum level of distortion and then an amplifier may well be able to deliver more power than you realize at a higher distortion level just by turning up the volume. Thus you cannot decide reliably whether your amp will damage your speakers based on power ratings especially those produced by different manufacturers. It is a guide however and provided your speaker is rated to handle significantly more than the amp. then likely you will be OK. (For other readers remember that if you connect a speaker with a lower impedance say 4ohm across an amp designed for 8 ohm it will deliver more power than rated.)
2. Our hearing is logarithmic not linear, so a few watts into a small speaker (think practice amp) can sound quite loud, and a 100W amp will only sound twice as loud as a 10W one (given an equally efficient loudspeaker in each case). Thus when you practice or play at a gig with others in a large hall you may easily turn up the volume to a power setting that will damage the speaker without realising.
3. Hi Fi speakers have mid-range and tweeter units and guitar amps and speakers don't usually as far as I am aware. Digital sound effect units probably have lot of high frequency content and especially if you turn the treble up you might not be doing your ears any good at high volume settings through a hi-fi speaker .
4. Much of the value of a guitar amplifier is in the distortion that it adds. Hence the eternal battle of tubes vs solid state etc. Hi fi speakers are designed to introduce as little distortion as possible. On guitar amps the voice coils are often driven beyond the linear region of the magnetic field and this is one way that valued distortion is introduced and the voice coils are designed to take rough treatment. You may not be satisfied with the sound from a hi fi amp.

My best guess is that provided you keep the volume turned down eg for home practice you will be OK, but since you burned out your guitar amp. speaker it might not be wise to risk it! I would not recommend using the set up at a band practice or gig.

Why not buy a 12 inch speaker and put it in a box made with with 3/4 ply or particle board with a hole in the back. Size the box like a typical guitar amp, the dimensions are not critical and put a grill of some sort over the cone to protect it. Alternatively pickup a discarded hi-fi speaker on garbage day and you won't care if it burns out!
#7
Thank you for the explanation. I did build my own box, actually. The 12" speaker sounds fine to me. It came out of a 3 way speaker system so the tweeter and mid range drivers are separate from the 12" speaker. I guess I'll get a real guitar speaker eventually. But for now, practice level is fine for me.
#8
So I was just looking at an Eminence 12" 75 watt speaker. Now assuming the impedence is the same, the higher the rated wattage on the speaker the louder I can go on my amp without blowing the speaker right?
#9
Quote by !..!_Rock_!..!
So I was just looking at an Eminence 12" 75 watt speaker. Now assuming the impedence is the same, the higher the rated wattage on the speaker the louder I can go on my amp without blowing the speaker right?

kinda. the wattage is how much power the speaker can take with out failing not how loud it can get, the loudness of a speaker is measured in sensitivity (dB). But yes you can turn your amp up without fear of blowing your speaker.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
Last edited by Robbgnarly at Aug 15, 2014,
#10
Instrument/PA speakers usually have heavier magnets. They are not as efficient as home audio speakers because most have the windings around the core magnets through which the current flows and make the speaker cone move longer than the range of transverse motion. Home speakers have fewer windings to maximize the use of the power going to them. Basically like Mad-Mike says you're instrument amp at high volume will push more current through fewer windings and either melt the wires or push the core through the speaker cone, breaking it.