Speaker swap....

[Mike Kowalik]

Since my knowledge of electronics is not that great I have a question for those more experienced. What would happen if an 8 ohm speaker is put into an amp designed for a 4 ohm speaker? Would there be damage to the amp itself or only reduced output?

[Dennis Detweiler]

reduced output

[Dave Mudgett]

The answer to this question depends on what type of amp it is.

With a typical solid-state amp, using an 8 Ohm speaker in an amp designed for 4 Ohms will typically reduce the output some. There should be no worry about damage because, in fact, the amp will be running cooler with the higher impedance speaker. On the other hand, using a speaker of a lower impedance may be an issue - you should look at the amp's specs and look for something like 'minimum impedance' for the speaker.

With a tube amp, using an 8 Ohm speaker in an amp designed for 4 Ohms will generally reduce the output, and possibly be problematic for the amp due to increased flyback voltage to the output transformer. Some output transformers - e.g., in some vintage Fender tube amps and others - are over-designed and can handle this. Others - e.g., in some vintage Marshalls and others - really do not like mismatched speakers.

There are exceptions to most rules. I have had one vintage Fender amp whose output transformer blew when run with a mismatched speaker. When I took a look at the transformer, it became clear that it was not a typical over-designed transformer typified in the larger amps. I've never had the guts to run something like a classic Marshall with mismatched speakers, but I know players who have and it did not end well. If the amp is gonna be cranked, I really think it is smart to run any tube amp with speaker(s) matched to the specified nominal impedance. Probably not such a big deal if the amp is not going to be pushed.

The good thing with the classic Marshalls and other amps of their ilk is that they generally have an impedance selector, so different impedance speakers can be run. And with Fender and other similar designs, I see no reason to use a speaker of a different impedance than called for.

[Mike Kowalik]

The amp would be a Peavey LTD400......and the speaker would be a Wheelhouse 150 8 ohm....

[Nathan Pocock]

The Session/LTD 400 manual has the specs at the end: at 1% THD: 210 watts @ 4 ohms, 120 watts at 8 ohms.

[Mike Kowalik]

Thank you for that info.....exactly what I was looking for.