rectoverb - correct ohm connection with 2 speaker cabs

[musicmasterguitarist]

i am playing a mesa rectoverb.

i put it in a head. it was a combo originally.
and now enables to use it with a variety of speaker cabs.

if i wanted to run 2 cabs with mismatched ohms..
( 1x12mesa is 8 ohms) the other (2x12marshall is 4 ohms..or
2 speakers in stereo are 8 ohm each)

which hookups on the amp would i use?

the amp has 1- 8 ohm, and 2 - 4 ohm outs.

technically, what would happen if i ran the 1x12mesa with the 8ohm outand the 2x12 speakers using the 2 - 4 ohm outs...
i think that i need the adaptor/converter right?


the manual indicates some examples so
i will check that out again to do it correctly.
but if someone has done before...
thanks

 

[domct203]

The 2X12 Cab run in stereo ( 8 ohm X 2 ) into the two 4 ohm tap on the amp is correct, but adding the 8 ohm 1X12 into the 8 ohm jack is going to really lower the total impedence to the amp. Mesa's are tough so you may be OK, just watch the amp and if you hear any 'puttering' or 'motorboat' sounds stop using the 1X12.

A better option would be to re-wire the Marshall 2X12 to be 16 ohms mono. Then you would plug the 16 ohm 2X12 into the 8 ohm jack, and the 1X12 8 ohm cab into the 4 ohm jack. This configuration whould provide a 'correct' impedence match.

Dom

 

[nomad100hd]

If you ran the 4Ω in the 4Ω jack and the 8Ω in the 8Ω jack at the same time, the amp will see half the nominal impedance. What you need is to run the 8Ω in the 16Ω jack and the 4Ω in the 8Ω jack. If you have those which i think you said you didn't.

Now if you run half power aka with 2 power tubes instead of 4 your basically turn the 8Ω into a 16Ω jack and the 4Ω into an 8Ω jack.

All that being said with most tubes amps running a miss match of 2:1 or 1:2 usually wont hurt anything. Maybe wear out your power tubes quicker, but they where out anyways. Some amps are designed with a mismatch.

 

[nomad100hd]

i agree with musicmasterguitarist rewire the marshall cab and then there no impedance issue. Right now mono it's wired parallel, so you need it wired in series.

 

[musicmasterguitarist]

the marshall cab - 1933 or 36? 2x12

in mono jack 4ohms

in stereo (2x12) 2 ins are 8ohm each spr

1x12 8ohm mesa combo

i guess i prefer to keep the head running 1 type speaker.
if i utilize the use of another cab i will contemplate
running stereo for blended tones.
that works great!

 

[nomad100hd]

I'm confused.... mixing speakers can give you really cool tones!

You can't run stereo with a mono head amp so i'm confused by how you going to run stereo. With the Marshall cab wired the way it is you can plug in the mesa 1x12 and one twelve from the marshall cab in stereo mode. This will cause the amp to see a 4Ω load. If you plug in the other speaker which adds another 8Ω in parallel your load will drop to 2.6Ω. If you just run one speaker from the marshall it might sound odd. I had a buddy do that with a cab and the other speaker acted as a passive radiator and the tone wasn't very desirable.