Impedance question

Just try the other tsp.  You are not going to hurt either the amp or speaker.  I don’t know about the specific impedance curve of your speakers, but generally speaking, the 4 ohm tap would minimize frequency response changes from speaker impedance interactions, but at the expense of reduced power delivery to the speaker.

By the way, i had a similar setup many years ago—the 1+1’s with a pair of Kinergetics subwoofers.  But, back the I did not run tube amps.  This was a nice sounding setup.

Hey there!

In the case of multi-way speakers, so long as you have a low and high pass filter the impedances are not in parallel. However, if you only have a high pass filter and the 12" woofer is full range then the impedance above the cap cut off F will be in parallel, though the woofer also will have inductance that rises and may make this better than it would be otherwise.

Consider at least a single inductor on the woofer to help things along.

I often find it useful to use XSim crossover simulator to answer questions like this one when in doubt.  It's free and easy to use.

I take it that the subwoofer is a passive subwoofer?  It still would be the case that you could try any of the taps to hear the result and not worry about harming anything.  The supposedly wrong tap often sounds the best.

Okay, thank you all for your responses. I'll try the 4 ohm taps and let you know what I hear.

Happy listening.

Hello musicfan2349.  Feel free to experiment with the taps feeding your subwoofer. A tube amp doesn't much care what it drives. The transformer protects the amp, even from short circuits. A speaker changes impedence with frequency, air loading, and cabliing. Try everything and don't worry. You can even try the 4 ohm tap for the - and the 8 ohm tap for the +. Use what sounds best. The thing that a tube amp with an output transformer dislikes in an open circuit - no speaker on its output terminals. Give it a load and it will be happy. Happy listening!

Thanks much @boomerbillone !