When I messed up, I ran an 8 ohm Taurus amp, from Poland, so here in the EU that's a thing. I'm gonna try 2 thing tomorrow. Running a new speaker cable on the Markbass and take my 2 amps to a cab I know for sure works, to make sure both my amps are in order. Then I can isolate the problem. If it's the cab, then it's a matter of finding out, what the hell went wrong.
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I messed up.
- Thread starter FunkyDane
- Start date
When I messed up, I ran an 8 ohm Taurus amp, from Poland, so here in the EU that's a thing. I'm gonna try 2 thing tomorrow. Running a new speaker cable on the Markbass and take my 2 amps to a cab I know for sure works, to make sure both my amps are in order. Then I can isolate the problem. If it's the cab, then it's a matter of finding out, what the hell went wrong.
This is all very confusing. No offense meant, but I don't think you fully understand ohms and loads.
As other have pointed out, 2 4ohm cabs will result in a 2ohm load. A 4ohm load is achieved by 1 4ohm cab or 2 8ohm cabs. The main concern with using mismatched load is damaging the head, not the cab.
I would be asking what head you were using and if it is capable of running down at 4 ohms, but since you said the head isn't damaged, it doesn't really matter.
Even if you blew the speakers (which it sounds like you didn't), you'd still get some sound out of them, it just wouldn't be good. I would assume that something got disconnected in the cab. Open up the panel on the back and look at your connections. Or, try a different speaker (NOT instrument) cable.
All of the amps currently made by Taurus are stable down to 4 ohms per their website.
All 4 of the Taurus amps on their website are fully capable of running at 4 ohms. So when you plugged in a single 4 ohm cab, you were running the amp at 4 ohms, which would be no problem.
I looked on Taurus' website. Every amp there says it goes down to 4 ohms.
Great. Thanks. So I can rule out a "burnt" cab. I'm side eyeing my speaker-cable now, who is the new suspect in this drama.
If using Speakon connectors, make sure to rotate the connector to lock it in, because if you don't, they won't work (from experience).
Thanks for the patience and help everybody. I know what to try now. Later.
A 4ohm cab and 8ohm head would likely damage the head far before damaging the cab. You were never dealing with a damaged cab unless you played at too high of volume, but than can happen even with matched impedances. Unlikely in this scenario anyway as the cab can handle up to 800 watts and the most powerful Taurus amp puts out 500. Possible, but not likely unless you were diming everything and really playing hard.
Some people successfully run impedance mismatches on old Marshall 100W heads. Some eventually gank their output transformer. Overall I think the transformers in old Fenders are considered a bit more robust.
I wouldn't assume everything is the same in the bass world. Tube bass amps are often significantly more powerful than tube guitar amps. I have some amps that are rated for over 400W. These tend to run the tubes pretty hard, and running an impedance mismatch further increases the stress on the tubes.
The general rule is the load can be one order lower than the amp expects. Most old Fender tube amps are set up so one matching cab provides the expected load. Running two cabs shows the amp half the expected impedance. I tried running two cabs on my old Fender Twin Reverb, and I thought it degraded the sound significantly.
IMHO, it's better to actually find out what is best for the amp. Mesa tube amps are claimed safe when the impedance is one order higher than the amp expects, I.E. the opposite of the so called general rule. Also the Mesa and Prodigy in particular run the tubes pretty hard and were discontinued because tubes were not holding up. While the manual says it's safe to run an impedance mismatch one order higher than expected, I think the best practice is to show these amps the expected load.
For reference, a cabinet with too low of an impedance is likely to put the amp into a shutdown/protection mode, assuming it has one, as opposed to burning up the cabinet. That will usually only happen if you overpower it.
It is possible the amp is faulty and developed enough DC offset on the output to damage the speaker. I don't think this is very likely though.
I think a faulty cable is more likely, or perhaps something random and coincidental, like a connection came loose inside the cab.
Get a regular 1/4 instrument cable and plug it into the speaker cabinet. Using a known good 9V battery, touch the tip to one side and the sleeve to the other, if the speakers jump out or in, then cabinet is fine and you have an amp or cable problem. If they don’t move, double check the battery and start checking connections to find where it’s lost.
Bonus tip: check to make sure all the speakers move in the same direction. Not uncommon for one or more to be backwards if someone had been in there before. If one is backwards, reverse the connections at the speaker.
Extra bonus advice: if it’s an amp problem, find a good tech. Not knowing what you’re doing inside an amp can be deadly.
Bonus tip: check to make sure all the speakers move in the same direction. Not uncommon for one or more to be backwards if someone had been in there before. If one is backwards, reverse the connections at the speaker.
Extra bonus advice: if it’s an amp problem, find a good tech. Not knowing what you’re doing inside an amp can be deadly.
2 pages of explaining impedance but nobody explaining troubleshooting.
You need to isolate the problem. Setup a head, cab, and cable that are working. Play and make sure the rig works. Now switch in your cab and see if it works. If not, you have an issue with the cab. More than likely something inside came disconnected. Open it up and look for any obvious wires hanging around loose.
You need to isolate the problem. Setup a head, cab, and cable that are working. Play and make sure the rig works. Now switch in your cab and see if it works. If not, you have an issue with the cab. More than likely something inside came disconnected. Open it up and look for any obvious wires hanging around loose.
Yes, sounds like a cable/plug issue.
Be very careful.
“testing” a bad speaker cable by just plugging it in is NOT a good idea. You are better off testing it with a meter or just setting that cable aside and using a different cable until you figure it out.
Any accidental touching of the two speaker wire conductors, in the cable or plug, while the amp is on will damage the amp.
Be very careful.
“testing” a bad speaker cable by just plugging it in is NOT a good idea. You are better off testing it with a meter or just setting that cable aside and using a different cable until you figure it out.
Any accidental touching of the two speaker wire conductors, in the cable or plug, while the amp is on will damage the amp.
Yeah, Fender guitar amps and powerful solid state bass amps are probably apples to oranges. Thanks for the clarification.
