Yes... good, basic thread here. Your "16 ohm" cab is still wired in "series" at the moment. Just rewire said cab into the "parallel" configuration to show a more-or-less-value of "4 ohms" . Just simply and very carefully join the two positives together, then the two negatives together. That being said, ..VERIFY ... then verify again with your new multimeter. Whenever I check a cab that someone is absolutely depending on ME to get it right, I'll write up a label with the ohms rating I found, date it.. and apply it right next to the output jack.
Ok, I got it done and checked it. Read 3.6, = 4 ohms.
I started by looking at the jack on the cab and making sure which wire was positive (tip), and which was negative (sleeve). Then I wired it as you said.
+ from jack to + terminal speaker 1, + terminal speaker 1 to + terminal speaker 2
- from jack to - terminal speaker 1, - terminal speaker 1 to - terminal speaker 2
Checked it at the jack(3.6), then put it back together, and then double checked again after plugging in a speaker cable. Same reading, 3.6. Voila, 4 ohm cab !
Made sure the extension speaker jack was working on the amp, then cut the - lead to the internal speaker so the amp would see only the 4 ohm load from the extension cab.
Last thing I need to do is disconnect the second speaker jack on the back of the cab since I won't need it and plug it with a Hearos.
Good tip on the label ! I'll do that. Cab impedance/watts, speaker brand/impedance/model #/watts rating.
I'll also put a large label on top of the amp next to the switches to prevent power up without a load, since the internal is now disconnected. (it's an old tube amp) The fuse is right next to the power switch, so I'll remove it each time I turn the amp off. Then I know I won't forget to plug in a cab before I power up. I'll Velcro a fuse box w/a spare to the top of the amp next to the label.
Something like-
Power up
1-connect extension cab/verify cable plugged in all the way
2-standby on
3-volume control down
4-replace fuse
5-power on
6-wait 1 minute, then turn standby off
Power down
1-power switch off, let amp cool down a few mins.
2-remove fuse and place in box
3-volume controls down
4-standby on
5-leave ext. cab connected unless moving/transporting amp
The amp has a polarity switch that is no longer operable because the amp has been upgraded to a 3 prong cord. I may wind up putting a switch in it's place to turn engage/disengage the internal speaker.
