SuperBee
965 posts
Feb 28, 2013
2:59 AM
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My epiphone amps have multiple speaker jacks, but all different impedence. i.e. 4, 8, 16
Can I use more than 1 of these at a time, without (ahem) impeding the performance of the amp?
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5F6H
1562 posts
Feb 28, 2013
3:10 AM
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Theoretically "yes", but in the real world, without a bunch of math, "NO!". Don't do it, even if you figured it out, the risk of an absent minded moment & potential damage is too high.
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SuperBee
967 posts
Feb 28, 2013
3:17 AM
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Glad I asked. Thanks.
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Rick Davis
1362 posts
Feb 28, 2013
7:23 AM
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Mark, as always, is correct. Don't do it.
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-Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
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tmf714
1519 posts
Feb 28, 2013
7:37 AM
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Wiring Multiple Cabinets
Sometimes, it's inevitable that we need to run multiple cabs of different impedances. Well, here's how you figure out how to solve that problem.
EXAMPLE:
The amp has 4, 8, and 16 ohm taps.
Cabinet A = 8 ohms
Cabinet B = 16 ohms
In this case,
1/8 +1/16 = 3/16
Divide the back number by the front number to get the impedance.
16/3 = 5.33
You would want to run both cabinets from the 4 ohm taps, or daisy chain them if (2) 4 ohms taps aren't available. Remember, it's safe to run a slightly higher mismatch.
...And just as a reference
(2) 8 ohm cabs = 4 ohms
(2) 4 ohms cabs = 2 ohms - *typically unsafe*
(2) 16 ohms cabs = 8 ohms
(1) 8 ohm cab + (1) 4 ohm cab = 2.66 ohms - *typically unsafe*
(1) 4 ohm cab + (1) 16 ohm cab = 3.2 ohms - *somewhat unsafe*
The two above examples would typically be unsafe to run at, although, the very bottom example would be better to run, since it's closer to 4 ohms. This would get by in a pinch on some occasions.
[disclaimer]
The information provided above is a general reference. In some circumstances, it may not be appropriate to mismatch impedances. Use common sense, and consult the manufacturer if possible. If you are in doubt, the safest bet is to find a cab that has a nominal rating of that of your amp. I am not responsible for damages caused from mismatching impedances.
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5F6H
1565 posts
Feb 28, 2013
7:51 AM
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TMF714 your post is not relevant to using multiple speaker taps at the same time, it deals with mixing cabs whilst using one speaker tap at a time.
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HawkeyeKane
1518 posts
Feb 28, 2013
12:05 PM
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Not to hijack, but I have a related question.
I have my Alamo, which runs an 8-ohm 15" speaker. I also have a Univox single 15" bass cabinet, which is a 4-ohm speaker. What, if anything, could I do to run the two off the Alamo at the same time besides getting a Z-Matcher?
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Hawkeye Kane
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5F6H
1568 posts
Feb 28, 2013
12:39 PM
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Well, it won't be convenient to wire the speakers in seperate cabs, in series, for 12ohms. In parallel they will be 2.67ohms total load, a bad mismatch (you will incur a faster rate of tube wear & possibly a failure in a very short time) for your 8ohm tranny.
Replace the speakers with 16ohm items and run one with a 100% mismatch, or 2 at 8ohms total in parallel, or Z matcher as you say.
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5F6H
1569 posts
Feb 28, 2013
12:39 PM
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Well, it won't be convenient to wire the speakers in seperate cabs, in series, for 12ohms. In parallel they will be 2.67ohms total load, a bad mismatch (you will incur a faster rate of tube wear & possibly a failure in a very short time) for your 8ohm tranny.
Replace the speakers with 16ohm items and run one with a 100% mismatch, or 2 at 8ohms total in parallel, or Z matcher as you say.
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timeistight
1142 posts
Feb 28, 2013
2:18 PM
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If you you do run the together, be aware that the 4 ohm speaker will get twice as much power as the 8 ohm speaker.
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Playing music... it's a privilege.
Kim Wilson
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