The Steel Guitar Forum

I am the happy owner of an original Session 400 head.


It's been my understanding that it wants to see a 4-ohm speaker load.


I would like to try it with my new Phil Jones Bass C2 cabinet, which is 8-ohms.


Can any harm come to either the amp or the cabinet by so doing?

Solid state amps usually list a minumun impedance, in your case 4 ohms. Higher impedance won't kill the amp, even an open, but expect reduced power.

Thank you, Bill.

Hi Jack,

Bill is right, it would not hurt the amp. Tube amps are not as forgiving, though, so be careful with them.

Anyway, the formula is "voltage squared divided by resistance = wattage". Double the resistance therefore halves the wattage.

However: that opens up hooking up another 8 ohm speaker in parallel, which would half the resistace, not only giving the right impedance (4 ohms), but also doubling wattage AND the speaker area, too.

Full speed ahead! .........Pat.

Thanks, Pat.

So, in a nutshell, I could hook my Peavey to the Phil Jones 8-ohm cab and my 8-ohm Greg's Pro Audio cab housing an Eminence Double-T 12, creating a 4-ohm load. And everything would be copacetic, since that's what the Session wants to see in the first place?

Hi Jack.

Yes, you can hook up 2 speakers and get your 4 ohm load. Although I did suggest it, there are more variables than just getting the right impedance.

It may sound good through one speaker, but not the other. The speakers may be out of phase and weaken the sound instead of enforcing it, so it's not a one answer covers all.

It really goes back to what Bill had brought out: Your amp can handle an 8 ohm load without you having to worry about it. An 8 ohm load is less work for a solid state amp than a 4 ohm load. If this one speaker satifies your gigging volume requirement, then you can leave it as is.

......Pat

The labeling on the back panel should say "4 ohm minimum" -- anything above that is fine.

Paralleling 2x 8 ohm speakers mostly works except if one cabinet is more efficient than the other, then that speaker will be louder.