Post by benttop (Steve) on Jan 28, 2008 9:01:40 GMT -7
Yes you can as long as you obey the output impedance of the amp. If I'm not mistaken, you have an 8 ohm output there. The speaker in your amp then is most assuredly an 8 ohm speaker. Now you have a problem, because to get an 8 ohm load on the amp, you need either two 16 ohm speakers in parallel or two 4 ohm speakers in series. That's not going to be very convenient with a combo if you intend to use the built in speaker.
Assuming you resolve that issue, you would need to use a Y cable between your Airbrake and your speakers to connect them all together. So it would be Amp > Airbrake > Y Cable > speakers.
If you are set on using the speaker in your combo, and you must add external speakers, you've really only got a couple of possibilities. One possibility is to add three more 8 ohm speakers and get your Y cable(s) made up so that you get a series/parallel network resulting in 8 ohms total load. This won't be a very friendly setup to say the least, but it is not difficult to do.
One other possibility is the Weber Impedance matcher product. It is called the Z-Matcher (taweber.powweb.com/store/zmatch.htm). That thing lets you match your 8 ohm amp to any impedance speakers, and it has the added advantage of having two speaker jacks. So you could then go Amp > Airbrake > Z-Matcher > speakers.
benttop - I'm not too sure you are correct - If I understand the situation jcv wants to use an Airbrake and an ext cab. If that is the case, and the airbrake is on the output of the amp and then splits to the internal speaker and the ext cab the combined impedance of the speakers shouldn't make a difference as the airbrake becomes the impedance load the amp sees. I had a question similar and called The Doc and that was my understanding of the situation.
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Post by benttop (Steve) on Feb 14, 2008 6:44:11 GMT -7
Hmmm. Well if that's so, it would be useful to have a chart of what impedances are allowed on the output side. Because obviously you couldn't put zero ohms there, and I doubt you'd want 100 ohms there either. Somewhere in between would be the allowed range. I confess I do not know what it would be. Might be I need to do an experiment here....