Mesa 2: 90 4ohm speaker outputs / impedance.

[MihcaelWithersOne]

Hi Guys

I have owned a Mesa Boogie 2:90 for quite a well and Iam struggling to find clarity in the manual on which configurations / combinations of speakers are safe / allowed, so I thought I would come and talk to the experts at Boogie board!

I currently have the amp connected in a stereo configuration using a Marshall 1936 2x12 (G12-T75s) cabinet. The stated impedance of the cabinet is 16ohms a side when run in stereo. So I have:

The Channel A 8ohm output going into the left side of the cabinet (16ohm).
The Channel B 8ohm output going into the right side of the cabinet (16ohm).

This creates what I understand to be a "safe" mismatch of impedance, although Ive read it drives the amp a little harder and affects the tone slightly.

I am asking this question as Iam just about to wire up my new cabinet which is a 4x12 cabinet with G12K-100s which have a nominal impedance of 8ohm. I have a choice of either wiring the cabinet in a stereo configuration where I have 2 speakers wired in parallel giving me 4ohms per side. Or I should wire them in series creating 16ohms per side.

I am pretty sure that I should wire the speakers for 4ohms and use 1 4ohm output on each channel. However iam unsure if this is safe. The manual makes some noise about

"Use two eight ohm cabinets into the two four ohm jacks"

.

Can anyone clarify or give me some good advice on this?

Thanks

Mike

 

[Triaxstasy]

Here´s an excerpt from the 2:50 manual (IIRC) on "Speaker impedance matching and hook-up guide".
Very helpful read concerning your question....

 

[Jackie]

Yeah 8ohms into 16 ohms is a safe mismatch.

I would suggest wiring them in parallel for 4 ohms per side. The 2:90 doesn't have a 16ohm jack and to me 8ohms output to 8ohms cab sounds the best (or in other words, no mismatch).

I think that statement in the manual refers to a multiple cab setup which is A way, but not THE (only) way to set up using 4 ohms. Later it says

Use one four ohm cabinet into one four ohm jack

Just like it says

Two sixteen ohm cabinets into a "y" cable works even better in the eight ohm jack

(the reason for the Y cable is that there is only one 8 ohm jack)

So you should be safe with 4 ohms per side.