What ohmage speakers for tweaker ext cab?

[andyplf1]

Advice needed here please....
I have a Tweaker 15 & 112x cabinet which is just fine for small pubs and clubs. However, we're doing some bigger venues this summer and there's no guarantee of a good pa that i can be mic'd into. I'm planning to make another extension cabinet myself with 2 x 10'' Jensens P10r's in it to give a bit more oomph. What ohmage speakers do i buy? The 112x is a 16ohm cab, do i get more 16ohm speakers and connect to the other socket in the back of the amp? What ohmage would i put the switch on the back of the amp at? This seems a bit of a minefield to a non-techy such as me!
Before anyone asks, i'm going for 10'' speakers as my favorite guitar sounds were all done using 10's. (Mainly Pete Townshend's old Bandmaster and currently his Vibro-King and also a lot of early 70s Stones was done on a Champ which i know is actually 8'') but i feel small may be better than big - for once!)
Any sensible advice would be appreciated.

 

[shimmilou]

The speaker jacks on the back of the Twkr are in parallel, the main jack must be used first. I assume that the main jack is a shorting jack to protect the amp if a speaker isn't plugged in, that's why it has to be used first if only one speaker cab is used.

One option would be to use two 8 ohm Jensen P10R, wired in series to give 16 ohms for the 2x12 cab. Using both the 1x12 (16 ohms), and 2x10 (16 ohms), together in this case would give 8 ohms total, set the selector switch to 8 ohms if you want to match the impedance. Using the 16 ohm position in this case would also be fine, and might even sound better than the 8 ohm position. Obviously, you can use the 2x12 by itself and set the selector to 16 for a match.

If you want to wire the Jensens in parallel (different sound than series), use two 16 ohm speakers to get 8 ohms for the 2x12 cab. Using both the 1x12 (16 ohms) and 2x10 (8 ohms) in this case gives a total of 5.3 ohms, which is close enough to select either the 8 ohm or 4 ohm switch position, 4 being closest to matched, but the 8 will probably sound better.

Sometimes, an impedance mismatch can sound better/different, and a 2 to 1 mismatch is no problem for the amp. You will get the most power out of the amp with a matched impedance, but not necessarily the best sound. I have tried 1x12 @ 8 ohms, a 1x12 @ 16 ohms, a 2x12 @ 16 ohms, all using the 16 ohm output of my 40. To me, the 8 ohm 1x12 cab sounded more clear, articulate and touch sensitive, while the 16 ohm 2x12 cab was much warmer and beefier. All sound great, just differences in response and loudness.