Hi Everyone,
I've got a pair of 16ohm Fane axiom AX10's currently in my musicman 210 sixtyfive. These were speakers which were in when I bought it, all 18 years ago. Normally these amps come with a pair of 8ohm 10" running at 4ohms. The extension speaker is in series (which is a musicman quirk). I want to be able to run the my 210RH cab which is a 4ohm with the amp - it should be able to do this with a safe mismatch anyway, but I'd prefer not to have the mismatch. Also, I'd like to run both cabs into my (newly acquired, still quite excited about this) Blue Angel using a Palmer cabmerger dongle.
I might be wrong, and I'd love someone to chime in with some better knowledge. But the way I understand it is I have a 4 ohm and an 8ohm speaker in series then the 4ohm speaker will be getting more amp umph than the 8 ohm. It might not be an issue, but this is partly my reasoning for doing the swap.
With that being said, all musicman cabs with two speakers were rated at 4ohm, and the single speaker options in cabs and combos were 8. So these amps were designed to run them both. So is there an issue with this?
Best
Richard
Comments
I probably wouldn't change anything, in fact - combined with the Palmer, the two different impedances give you more options to control the sound balance than if they're the same.
In parallel, 4 and 8 ohms gives 2.66 ohms, which is safe with the amp set to 4 (though again, avoid the Blue Angel at 4 in 6V6-only) and 2/3 of the power going to the 8.
The Blue Angel ideally needs to run into double the marked impedance in 6V6-only mode (this is in the handbook), but is safe at the marked impedance. I'm pretty sure this was done deliberately because a low mismatch is a characteristic of the overdriven sound of a Fender Deluxe Reverb, which seems to have been made like that by accident... either way, it means you’re probably better keeping an 8-ohm cab.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Just to clarify, when I'm on the 6v6's I'll be using the 4ohm tap into the 8ohm cab?
And the EL84 would be happy with using the 4ohm into the 8ohm as well as the 8ohm tap into the 8ohm cab?
Ideally you would connect the 8-ohm cab to the 4-ohm output and the 4-ohm cab to a 2-ohm output, but the amp doesn't have one, so I would connect both to the 4-ohm outputs, and just probably avoid cranking it too hard in 6V6-only mode. As a general rule of thumb if you can't match the combined impedance exactly it's best at one lower than the cabs for 6V6s, either direction for the EL84s, and one higher than the cab for Simul.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Impedance matching isn't quite as critical as it's often made out to be - up to a 2:1 mismatch in either direction is almost always safe, and definitely if you're not overdriving the power stage. At lower volumes even further out than that is fine, if you're not pushing the power stage hard then even 4:1 is safe.
There are only two really big things to make sure you don't do: never run a valve amp with no load, and never run a solid-state amp below its minimum impedance.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein