Peavy Classic 30 - Extension Speaker

[mscan25]

I have a Peavy Classic 30 with a few mods that really sounds terrific. I've been thinking about getting a 2x12 speaker cabinet that will work well with it for mid-sized clubs.

The speaker in the C30 is a 16 ohm speaker. Also, there's a '16 ohm minimum load' message printed on the back of the amp. I've heard two different stories on what the ohm rating of the cabinet should be. One person says an 8 ohm cabinet will work, while another says only use a 16 ohm cabinet.

I have found a 2x12 cabinet with two 16 ohm speakers wired in parallel which makes the cabinet 8 ohms. So the question is, is it safe to use this cabinet or do i need to get a 16 ohm cabinet. Anybody up on this stuff??

Thanks,
-Mark

[dobrota]

C30 extension Speaker

Speaker inside C30 is 16 Ohm but output for cabinet is 8 ohm (jack switch to other pin of output transformer, see schematics). This way is possible to use 8 ohm speaker inside C30, but it must be connected to jack for external cabinet, no to wire from chasis.
I use it for long time without any problems.
And some people say, that 8Ohm transformer output sounds better then 16Ohm :-)

[mscan25]

thanks dobrotha

So... i can purchase this 8 ohm cabinet, plug in and go without hurting the amp, and without having to make any modifications?

[Enzo]

Not quite.

The internal speaker is 16 ohms, everyone agrees.

When you plug ANYTHING into the extension speaker jack, it switches the amp over to 8 ohms. And by "anything," I mean a extension cab, or a unwired plug.

That 8 ohm result INCLUDES the internal speaker.

That means you are expected to use a 16 ohm extension cab. SInce 16 ohm cab plus 16 ohm internal speaker makes 8 ohms total.

Using an 8 ohm cab with the existing internal speaker results in a 5.33 ohm total load, which would then be connected to the 8 ohm tap. This is not likely to hurt a darn thing, but it isn;t "correct."

What I think dobrota was talking about is this: You can put an 8 ohm speaker in the amp and wire it to a plug. Then plug that into the extension jack. That way the amp is switched to 8 ohms and you have an 8 ohm speaker. When you do this, though, you can't use the original internal speaker wires. Tape them off so they don;t touch anything. But since that 8 ohm speaker is on the amp's 8 ohm tap, you cannot add an extension speaker that way.

Oh, well, there is one other way. You could mount an 8 ohm speaker inside the amp and connect the internal wires to it, then just shove a dummy plug into the external jack. That would switch the amp over to 8 ohms, and all would be happy.

So:
1. You could plug the 8 ohm cab into the extension jack and disconnect the internal speaker, and the load would be proper.

2. You could get a 16 ohm cab, plug it in the extension and keep the internal speaker and all will be happy.

or
3. You could indeed plug the 8 ohm cab in the extension, keep the internal speaker, and it ought to work fine even though the load is "wrong."