Which speaker outputs for extension cab???

Hey guys,

I have a Lonestar clasic (series 1) 2*12 combo. I have a 2*12 extension cab with 2 * v30 celestions which is wired to 4ohms. Which speaker outputs should I use to power both the speakers in the combo (which I believe to be 8ohms) and the speakers in the extension cab?

Any help would be greatly appreciated!

You can't run the ext. at 4 ohms along with the combo's speakers. It's to low. It could damage your amp. Only by itself. Most likely you have 2 V-30's @ 8 ohms each wired in parallel. Rewire them in series and you'll have 16 ohms. Now you can plug it in the 8 ohm jack and the combo's speakers in the 4 ohm jack. The manual covers all this.
http://www.mesaboogie.com/manuals/Lonestar.pdf

I have the same rig you have. The Mesa guys made it simple and idiot proof.
use the two 4 ohm outputs.
move the combo's speaker lead from the 8 ohm output to one of the 4 ohm outputs and plug the ext cab into the other
4ohm output. Use a speaker cable, not a guitar cable.

Telemaster said:

I have the same rig you have. The Mesa guys made it simple and idiot proof.
use the two 4 ohm outputs.
move the combo's speaker lead from the 8 ohm output to one of the 4 ohm outputs and plug the ext cab into the other
4ohm output. Use a speaker cable, not a guitar cable.

Click to expand...

Actually, plan-x is right. 8 and 4 ohm isn't a safe mismatch. See in the manual. This would lead to a load less than 4 ohm, which is not healthy for the amp and reduces tube life dramatically. 8 ohm and 8 ohm works (4 total), 8 and 16 ohm works (6 ohm total), 16 and 16 ohm works (8 ohm total), etc, but anything under a total of 4 ohm isn't good. Even for Mesas.

8 + 4 in parallel = 2.67 ohms. Marginally safe, at best.
(2 ohms is the absolute minimum.)
16 + 8 in parallel = 5.33 ohms. Safer.

Lads, I just sent this thread to my rep at Mesa and this was his reply:

Q:"am I correct in using the two 4 ohm outputs …one to the combo speakers and one to the ext cab?"

"A: You are correct. The 4 ohm taps are the way to go when adding an extension cab."

like I said, they made it easy for everyone who would otherwise over think it.

disconnect the right angle speaker lead to the combo's 2 x 12's from the 8 ohm input and move it to one of the
4 ohm inputs, then plug the extension cab into the other 4 ohm input.

There are two 4 ohm taps on the back of the amp....that's what they are there for.

Did you mention to the mesa dude the ohms of the ext. at 4. Or that the manual has several configuration illustrations, none of which include a 4/8 combination. You can see it in the link I posted in the 2nd post of this thread. Pg. 29, 2nd paragraph Says: MESA/Boogie amplifiers can handle 4 and 8 ohms effectively. Never run below 4 ohms in a tube amplifier unless you are absolutely certain that the system can handle it properly; this can cause damage to the Output transformer. A few amplifiers can handle 2 ohms effectively without damaging them ( for example the MESA’S Bass 400+ ). You can always have a higher resistance ( 16 ohms, for example ) without damaging results, but too low of a resistance will likely cause problems.

I bet that dude won't go on record saying that. That's like running a car @ 7000rpm. Sure, a car can do it, but for how long and at what cost.

Guitar amps usually can only handle down to 4. Only certain bass amps can handle down to 2. Usually a dual amp(stereo) bridged.

MrMark III is absolutely correct with his math.
8 + 4 in parallel = 2.67 ohms. Marginally safe, at best.
(2 ohms is the absolute minimum.)
16 + 8 in parallel = 5.33 ohms. Safer.

Here is a link with a speaker ohm calculater. http://www.about-guitar-amps.com/speaker_ohms_calculator.html

I am not trying to offend anyone here. I just want to make it clear to the original poster. For the money I paid for my LSC, I'm not going against the manual on this one, or common practice of tube amps. I won't run it lower than 4 ohms comblned.

hey Plan-x...after checking the manual that makes a lot of sense. But I'm getting mind boggled now. I just spoke with one of the techs at Mesa about my particular amp. He confirmed that the two 4 ohm outputs on the back of the amp should be use to connect an ext cab, as they normally configure the ext cabs to match the combo amp, just as I outlined previously. He said the wiring at the ext cab input is parallel so it matches up to the load on the combo cab speakers.
But here's the glitch in this for me: Unless my brain, gray hair, and tired eyes are mistaken, which they certainly could be, my ext cab has a label on the back that says 4 ohms next to the input jack. My custom order form states that the speakers in my cab were supposed to be "C90's -16 ohm (8 ohm total)" - which, wired parallel, would match my 8 ohm combo speakers to the ext cab I ordered.
He said Mesa usually doesn't even make 4 ohm cabs and he can't figure out where a 4 ohm input label even came from since they normally don't have labels for that. So I'm going to take a look at my ext cab speakers tonight to make sure they are rated to match the combo cabs speakers.....argh. All I can say is, I hooked it up like they told me to and it sounds great... even though there is some confusion. Man, my brain hurts!

ok, sorry, my bad.
my cabs are both 8 ohm cabs...I misread the original thread and didn't catch the 4 ohm
mention well enough for it to filter thru my tiny musician brain... I am not worthy of this thread...not worthy...not worthy....

I didn't know squat until I got this pig 4 years ago. I was using SS amps, and modellers. The Boogie manual is very informative. So's the internet.

I learned along the way that you can use an ohm meter or multimeter to figure out the ohms of a cab without even opening it up. Just plug the speaker cable to the cab and place the meter leads on the tip and sleeve of the other end of the cable. +/- doesn't matter. It should read a little below the actual speaker cab rating. Maybe 6-8 ohms for an 8 ohm cab. And 2-4 ohms for a 4 ohm cab.

Cool. I've gotta give that a shot and see what the reading is.
Have had my LSC for 4 yrs now...and the ext cab for only a few weeks.
I used an SS amp for a long time...(a Lab Series L7)...
Before that I had an old Gibson amp...it ended up getting loaded
onto another band's truck at a show we did a few years back while we were loading in and they were loading out....bummer.