laney cub12 extension speaker option

midlifecrisis

firstly, happy to have found this site, use to read the MR one before it closed.

My laney cub 12r combo has a speaker  output which disconnects the internal speaker when plugged in. I want to ad another output jack probably on the back grill, that allows the internal and external speaker to be used together, should be simple I think but need guidance on what type of jack socket and wiring configuration needed. I understand the ohm issues and want to wire in series, ie two 8 ohm speakers to make 16 ohms which the amp can handle.

ta

midlifecrisis

 

ICBM

You need a switching jack, like this:

http://www.newoldsounds.com/ebay/J-CL-102.JPG

Connect it in the return path between the negative terminal of the speaker and the ground of the amp - not in the positive connection as this could cause a short if for any unusual reason it comes into contact with anything grounded.

You need to connect the ground contact of the jack to the amp's ground, the tip contact of the jack to the speaker negative wire, and use the switches in the jack to bypass the jack when no cable is in it - connect two wires in an 'x' across the four terminals (not touching each other) so the two switches are in parallel, which will improve reliability… you want to avoid an open circuit if the jack switch ever doesn't make perfect contact, so having two helps.

Switching in the speaker path (especially using jack contacts) isn't really an ideal thing to do anyway, but at the fairly low power this amp is, and if you use both switch contacts, it's not too risky.

midlifecrisis

thanks for that,  something to try over the weekend if I can get the jack.