Modding the Airbrake for two cabs

[west]

I am using 2 speaker enclosures with a 25 watt amp on stage. Can I jumper a second "speaker out" jack wired in parallel in the Airbrake without hurting anything, or do I need to build a second Airbrake?

[geetarpicker]

It's an impedance thing. I'm pretty sure the Airbrake is optimized for 8 ohms, but it's load on the amp can vary a bit due to the speakers themselves. When you add a second speaker jack in parallel your load will basically be cut in half, if you are running two cabs both of the same impedance. So, two 16 ohm cabs in parallel would net 8 ohms to the circuit which should be fine. Still, if I recall correctly the instructions that came with my factory built Dr.Z Airbrake suggested running some amps at 1/2 the speaker impedance, for example running the Airbrake with a 16 ohm load but setting the amp on 8 ohms. I will say my '68 Superbass plexi 100w was happier running with that offset as the tubes would red plate when running it "properly" matched.

What output impedance or impedances does your amp have?

[west]

I've got an impedance selector (4/8/16) on the back of the head. Total load for both of the cabs is 4 ohms