Series wired external speaker with combo

[fingerbun]

What advantages come from a series-wired external speaker, and how can I best take advantage of that?

Background I have a Roland CB100 that I use for smaller gigs. I want to add an external speaker to it. From forum searches I have learned that the external speaker jack is wired in series rather than parallel, and because of this adding an external speaker will improve tone but not volume.

Why would an amp be designed that way? I'm sure the good folk at Roland knew what they were doing, and every other aspect of the Cube's design is very good imo. It just seems like a counter-intuitive design decision.

[will33]

The internal speaker is already at the amp limit as far as low impedance, trying to get the most out of the combo by itself. In order to add speakers, they have to be wired in series so the impedance increases and does not blow the amp. You'll still get more overall output by adding speakers, just not as much as if you increased speakers and power.

[billfitzmaurice]

Originally Posted by fingerbun

What advantages come from a series-wired external speaker

There are none. You only do so if you have to, because the internal speaker is already at the amp's minimum load impedance.

It just seems like a counter-intuitive design decision.

Agreed.

[fingerbun]

OK, so I have decided to add the extra speaker anyway. Others who have done it say I will get a fuller tone, though not a noticeable increase in volume.

I am going to reverse-engineer the cabinet from the Cube's measurements, and I have the same driver that's in the cube. Anything else I should consider, and any tricks for making sure the speakers are in phase without opening up the combo?

And what should be the theoretical change in volume?

[JimmyM]

Battery test...touch pos to pos and neg to neg, and look at what direction the speakers move. They should both move outward if they're in phase.

[fingerbun]

Originally Posted by JimmyM

Battery test...touch pos to pos and neg to neg, and look at what direction the speakers move. They should both move outward if they're in phase.

But how do I do that to the in-combo speaker without dismantling?

[JimmyM]

Hook up a speaker cable and expose the wires on the other end.

[fingerbun]

Originally Posted by JimmyM

Hook up a speaker cable and expose the wires on the other end.

Blush. I knew that