8 ohm speaker/4 ohm amp

[JB_From_Hell]

I've got an old Peavey Audition 20 practice amp, sans speaker. On the back, it's labeled "12 Watts, 7 V RMS, 4 Ohms".

I don't really want to put a bunch of money into it, so the speaker is gonna be second-hand. Unfortunately, I haven't ran across any 4 ohm speakers. I have seen some 8's, however. Is there any way to safely hook it up, besides two 8's in parallel?

 

[Smilemon]

Re: 8 ohm speaker/4 ohm amp

get an 8 ohm resistor and run it in parallel with the speaker.

 

[Smilemon]

Re: 8 ohm speaker/4 ohm amp

A beefy resistor that is. not some half watt carbon comp one.

 

[Smilemon]

Re: 8 ohm speaker/4 ohm amp

600 posts! yay

 

[JB_From_Hell]

Re: 8 ohm speaker/4 ohm amp

get an 8 ohm resistor and run it in parallel with the speaker.

Well, the only problem there is that speakers are measured in impedance, which is a measure of both AC & DC, so I'm thinking the resistor thing wouldn't exactly work.

 

[Smilemon]

Re: 8 ohm speaker/4 ohm amp

Hmm, i didn't know that, my uncle could never really explain impedance to me even though hes an electrician... is the amp a solid state amp? It can probably handle the speaker if it is...

 

[JB_From_Hell]

Re: 8 ohm speaker/4 ohm amp

Yeah, it's solid state. I'm an EE student, but we haven't really gotten into impedance yet. I do know that the circuit does not see a resistor the same as a speaker, though.

What I'm thinking is that if the speaker is rated higher than the amp, it should keep the amp from working to it's full potential. If the speaker was rated LOWER than the amp, that's when I'd have trouble. I'd prefer to do it correctly, though, and I'm definitely not above making it a 2X12 practice amp

 

[ksmith63]

Re: 8 ohm speaker/4 ohm amp

impedance is pretty much resistance so you could do the resistor thing OR since the amp is at a lower resistance than the speaker you could just run it normally with the 8 ohm load. think of more resistance as less heat drawn from the amplifier. this is why amps get into trouble running lower impedance speakers, they draw too much current and over heat.

 

[Smilemon]

Re: 8 ohm speaker/4 ohm amp

my style would be to just put it together with the one speaker and if it doesnt work try two speakers later... or pitch it.

 

[marvar]

Re: 8 ohm speaker/4 ohm amp

Don't worry about it- it's a solid state amp- there is no output transformer to blow- you won't be hurting a thing- you just won't have quite as much power/loudness. It will actually be less stress on your output transistors.
SS amps are very forgiving when it comes to speaker impedence, as long as you don't go lower than the rating of 4 ohm load.

 

[Virtual Kevorkian]

Re: 8 ohm speaker/4 ohm amp

4 ohm amp into 8 ohm speaker is fine, and even more so in your case since it's an SS amp.

 

[JB_From_Hell]

Re: 8 ohm speaker/4 ohm amp

Excellent. Thanks everybody.