Altering a valve guitar amp for bass usage.

ESBlonde

You say 'spread' of the bass, I already presumed it played like butter ;-).
The lower frequencies of a bass guitar are not directional so for punter out in the room it is largely irrelevent to them with the exception of those pressed up against the edge of he stage in front of the bass cab or guitar cab who would have an unbalanced soundscape. In a short but narrow room (playing accross it) that might be an issue but otherwise I'd be more concerned the guitar was spreading and not beaming horribly.

Rocker

When I plugged the speaker into the 'speaker out' on the Markbass, I discovered that this action switches off the internal Markbass speakers, diverting all the output to the external speaker.  And the sound from the external speaker was a bit peaky and bright for my taste, without being much louder.  Unplugging the external speaker gave me back the sound I like so that theory has been tested and found wanting.  So the solution now is to use the Markbass as it is and take a DI out to the PA system.  This way we get bass and others can hear it too!

Thanks to all for your contributions.  Great to have near instant access to so much technical knowledge.  Take a bow lads.

ICBM

Rocker said:

When I plugged the speaker into the 'speaker out' on the Markbass, I discovered that this action switches off the internal Markbass speakers, diverting all the output to the external speaker.

It seems a bit counterproductive to do it like that. The usual point of an extension cabinet is to give more volume, both by lowering the total load impedance and increasing the power output, and producing more air movement.

Rocker said:

So the solution now is to use the Markbass as it is and take a DI out to the PA system.  This way we get bass and others can hear it too!

Definitely the best solution given this, unless you want to go back to Plan A and use the Nolan to drive the extra cab.