Connecting 2 sets of speakers to a tube amp

You could always wire the speakers in series instead of parallel.

Marty (Viridian), note that the speakers are different models, one being rated at 4 ohms and the other at 8 ohms. Series connection of different models will usually result in significant sonic degradation.

How the voltage and power being output by the amp at a given frequency at a given time will divide up between the two speakers depends on the relation between the impedances of the speakers at that frequency. Therefore the frequency response of each speaker will be affected in an arbitrary manner by how the impedance of the other speaker varies as a function of frequency.

Another factor that might also be an issue with a series connection is that the 8 ohm speaker will receive considerably more power overall than the 4 ohm speaker. Based on the oversimplified assumption that the impedances of the two speakers are purely resistive and correspond to their 4 and 8 ohm nominal ratings, the 8 ohm speaker would receive twice as much power as the 4 ohm speaker.

Regards,
-- Al

Al, absolutely correct, and those are the issues that result in us generally not seeing series connected speakers, even of the same impedance, in high fidelity applications, but it's certainly worth a try as it is the only solution that will present a high enough load to the driving amp. There should be no danger in trying and it will only take a few minutes to find out the bad news, LOL!

Skoda:

let me know how you like the pre-out to a second preamp setup. I am sure you will love it. You can set the relative volume of the backfill speakers with the volume of the second amp... and none of the problems that were listed by other posters is an issue. Again... let me know how you like it.

My system at 2 channel/4 speakers for a total of 22K outperforms (or equals) ANY 2 channel/2 speaker system for 40K. No exaggeration. the 2 channel/4 speaker route is an unbeatable performance-to-cost upgrade. Enjoy.