converting a 4 ohm speaker into an 8 ohm speaker???

Mr Mustache · Post by **Mr Mustache** » Sun May 18, 2008 8:28 pm

can it be done? i see different people on line saying yes it can be done and other people saying no it can't

here is my problem. i have my Alamo Fury 115 combo amp, and i blew my 8 ohm speaker, now i have a free 4 ohm replacement speaker from a co worker.

some places online say i can add a 4ohm resistor in line between the speaker and amp and it should work fine without blowing up the amp.

but then i found things like this

Incidentally, you CANNOT make a 4 ohm speaker into an 8 ohm speaker by wiring a 4 ohm resistor in series with it (I once saw someone trying to do just this at Radio Shack). This will make the amplifier happier, since as far as it is concerned it has an 8 ohm load (which is easier to drive). However, resistors dissipate energy, they DO NOT generate sound. Wiring a 4 ohm resistor in series with a 4 ohm speaker will halve the amount of power which reaches the speaker (it will also degrade the damping factor, which won't hurt anything but it can degrade the sound quality!). Since amplifier power is relatively expensive, it would be extremely foolish to "throw away" half of it by wiring a resistor into the speaker's electrical path! Again, if you have 4 ohm speakers, you cannot change them into 8 ohm speakers... get an amplifier that is capable of driving 4 ohm systems!
Is an 8 ohm speaker really 8 ohms?

from this site http://www.rocketroberts.com/techart/spkr.htm

so will it effect the sound quality of a guitar amp, that i'm going to running with the volume at 10?

... so can i do it, should i do it? ?

Post by **Mike** » Sun May 18, 2008 8:54 pm

The quote is correct. All you'd be doing is just halfing the power. Get the right ohmage speaker.

Bacchus · Post by **Bacchus** » Sun May 18, 2008 8:56 pm

I was talking to my flatmate, who is a second year electrical engineer student, and he mentioned something about resistance not being the same as impedance.

I was confused.

Justin J · Post by **Justin J** » Sun May 18, 2008 9:05 pm

BacchusPaul wrote:I was talking to my flatmate, who is a second year electrical engineer student, and he mentioned something about resistance not being the same as impedance.

he's right. if you measure the resistance of a speaker with a multimeter you will not get the same number as the rated impedance.

Mr Mustache · Post by **Mr Mustache** » Sun May 18, 2008 9:29 pm

cool thanks dudes... you guys got my trust

Post by **Mike** » Sun May 18, 2008 9:37 pm

BacchusPaul wrote:I was talking to my flatmate, who is a second year electrical engineer student, and he mentioned something about resistance not being the same as impedance.

I was confused.

He's correct. Impedance is a frequency dependant quality.

Bacchus · Post by **Bacchus** » Sun May 18, 2008 9:45 pm

Mike wrote:
BacchusPaul wrote:I was talking to my flatmate, who is a second year electrical engineer student, and he mentioned something about resistance not being the same as impedance.

I was confused.
He's correct. Impedance is a frequency dependant quality.

We were talking about my tone at the gig the other night, with the four ohm cab.
I think I nodded something vague about lower impedance makes my tone nice and open, and then politely ducked out of the conversation nodding my head.

Post by **Mike** » Sun May 18, 2008 9:49 pm

The best thing to do is to match impedance. Then you're getting the "most" out of your amp because it's communicating 100% with your cabinet.

LimpDickCheney · Post by **LimpDickCheney** » Mon May 19, 2008 1:31 am

Replace the voice coil... but if you are going to do that you might as well get a different speaker.

NickS · Post by **NickS** » Mon May 19, 2008 8:33 am

Can you check to see whther the transformer has other output taps?