speaker ohm question

[Karma1]

I've got a 40 watt Marshall Valvestate VS 8040 combo amp with the stock 12" Celestion G12L. It's a four ohm speaker and I'd like to replace it with a Vintage 30, but I've only seen them in 8 or 16 ohm. Any problem using an 8 ohm instead of a 4 ohm speaker in a basically solid state amp?

[IBDBB]

So, i'd assume the output on the amp is 4ohms right?

You can use an 8ohm speaker in a 4ohm output, although it is not "recommended". IIRC, that gives your amp not as much a load as it wants. I just bought a crate v33212 that came with 2 16ohm speakers plugged into 2 8ohm outputs, so.....go figure.

I swapped them out for 8ohm speakers though.

 

Just don't use a 4ohm speaker in an 8ohm output. Your amp will not like you.

[mc5nrg]

In general how tube and solid state amps interact with and therir requirements regarding speaker impedance and matching ohms and output are different.

 

Usually SS amplifiers have a minimum impedance requirement that the amp wants to "see" or can safely drive. This will usually be listed as X ohm minimum. The amp will usually be able to put out its full rated power driving this "x" ohm minimum load, if its see a load below this figure it will usually fry.So you can safely sub a speaker with a higher impedance, however the power output of the amp will be lower. This is the general rule with SS power amps. There might be rare exceptions and the situation with tube amps is quite different.

[tlbonehead]

your amp will like it just fine. It just won't put out as much power at 8 ohms. But the V30 is probably more efficient so I doubt that there will be any volume loss.

[Karma1]

Thanks for the replies - much appreciated.

Sounds like the 8 ohm will work ok, although the amp is not that loud to begin with so I'd hate to loose any more volume. But I use a Mesa Boogie V-Twin tube preamp in front of it, which gives it a bit more juice.