SS amp speaker impedence Q

[daz]

What are the sound and reliability ramifications of running a solid state amp thats designed for a 8 ohm speaker with a 16? How about a 4?

[Chuck H]

It should be safe at 16 but will only produce half power. If it's not designed to handle a 4 ohm load it may cause the amp to over dissipate. Think of it this way, a SS amp will try it's best to put the same AC voltage onto any load you plug it into. If you use ohms law it's easy to see where this $h!ts the bed when the voltage is constant but you change the load as far as actual watts go.

[Leo_Gnardo]

What are the sound and reliability ramifications of running a solid state amp thats designed for a 8 ohm speaker with a 16? How about a 4?

No problem running a 16 instead of 8 ohm. Solid state - you're asking for half the output current, therefore your output transistors heat up half as much. You get less power, otherwise should be sonically identical.

4 ohms, now we're making the output transistors heat up double. You may be able to get away with it at low volumes, but when you ask for big power, bound to run into trouble. Also remember, speaker "nominal" impedance is just a sort of average of real speaker impedance over a range of frequencies, and for some frequencies that curve dips BELOW the nominal impedance. So when you hit that "magic note" your amp's really looking at 3 or maybe 2 ohms, kaboom time for your amp.

One of our correspondents mentioned a week or so back "smart PA operators don't load down the amps to their most extreme spec. If the amp says it can run 2 ohm loads, don't load it with less than 4." Something like that. Excellent advice.

[daz]

Thanks guys, thats what i needed.

[Mick Bailey]

Also additional complexities if the amp uses mixed-mode feedback with a current-sense resistor in series with the speaker.

[Chuck H]

Also additional complexities if the amp uses mixed-mode feedback with a current-sense resistor in series with the speaker.

That's a good point.

I seriously hope any guitar amp builder that allows for the speaker to be accessed via a standard jack has the good sense to NOT complicate the issue of possible mismatched load impedances. Then again, designing circuits and understanding the nature of the end user can (but shouldn't) be two different things.

[Leo_Gnardo]

I seriously hope any guitar amp builder that allows for the speaker to be accessed via a standard jack has the good sense to NOT complicate the issue of possible mismatched load impedances. Then again, designing circuits and understanding the nature of the end user can (but shouldn't) be two different things.

Tech: You know, this amp is rated to be used with 8 ohm speakers only.

Crustomer: Yeah, all my speakers are 8 ohms.

Tech: You only use one at a time, right?

Crustomer: Heck no, I got about thirty-one hooked up.

Tech: (smacks forehead with palm as he falls over.)

[g1]

"I don't care how many hohms, I just want the more watts!".

[Leo_Gnardo]

"I don't care how many hohms, I just want the more watts!".

Ahnd mo' bayuss awn awll freequencies mon! (In growly voice wit' t'ick Jahmaican ak-sent.)

[g1]

Yah mon, maximum beesss at ahl frequencies! (with lots of RE301 on that vocal)

[Enzo]

Could be worse, I know the Italian Pastafarians play Ragu music...