4 ohm and 8 ohm speakers simultaneously on a tube amp?

[fourxjake]

I have an Consonance opera tube amp. The amp uses KT88s in a push pull final stage with transformer output configuration. The amp has speaker connections for 4 ohm and 8 ohm but only a common negative for each channel. I was wondering if I could connect 4 speakers, two on each channel utilizing both + connections and the single common negative. I have both 8 ohm and 4 ohm speakers.

Thanks for your help - Jake

[mjtab]

Let me ramble a bit and throw out some thoughts for you to ponder.

Typically the 4 a 8 ohm taps are to optimize your speakers to the amp. Some find better results using some speakers connected to a tube amp using different taps than the speaker nominal ohm rating. Speaker ratings can vary quite drastically w/ some speakers so this could be why better results are obtained with the incorrect output tap.

As far as using two sets of speakers the impedance will drop to half what one speaker will offer. Can your amp safely drive 2 ohm or less speakers? My AES (Cary) tube amp was safe driving 1 ohm speakers, and only had one set of output taps per channel that any impedance speaker could be used. I suppose if you bi-wire one set of speakers it might seem to be the same on, but the woofers of each speaker is really what is interacting w/ the amps current draw, not the tweeter.

I'd feel more comfortable if both your speakers were an easy to drive 8 ohm, like Klipsch Heritage or vintage Altecs, but still unlikely to hook them up. To be safe I would avoid it and spare the agony of damaging the output transformers of your amp.

[Mr Peabody]

I would check your manual or with manufacturer, I'm pretty sure you should not use both at the same time. It wouldn't be a benefit any way as likely each set of speaker would have different sensitivity which would make one pair play louder than another, not to mention the summing and cancelling of frequencies messing up your response. No matter how you set them up you would also be near impossible to get proper imaging.

Actually with a common ground it sounds like the speakers would be in series with each other which would sum the impedance.

Why were you wanting to hook two pair of speakers up? Maybe we can find another option that might help you.

[Hyfi]

What about a little Niles switch?