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ANOTHER Behringer Cutting Out Issue

CCtop

CCtop

Jan 8, 2012
107
44
#1
There's a 5 page thread on this somewhere here already, but it doesn't seem like the problem got solved. Here's my issue and the equipment I'm using:

Recently bought the Behringer Ultrabass head. Just got a 2nd Peavey headliner 410 for father's day.

I have my Ultrabass head running to the bottom 410 and then the bottom 410 hooked up with the 2nd parallel socket to the cab on top. So the wiring is going out of the Ultrabass into the bottom 410, then out of the bottom 410 into the top 410. Simple enough, no?

I AM using speaker cables, not instrument cables. And of course an instrument cable on my bass.

The Ultrabass puts out 180w at 8 ohms and 300w at 4 ohms. Since the cabs are 8ohms and connected to each other, then it should be the 300w at 4 ohms.

Now, here's the issue: Playing using one cab at 180w and 8ohms, everything is fine. As soon as I hook up the 2nd cab, the sound cuts out whenever I hit some hard notes. It'll cut out for like 3 seconds then come right back on. Then cut out again as soon as I play some notes a little louder. This will just continue.

The cabs are 800w each, but that shouldn't be an issue.

So, *** is going on?

Update: I just tried plugging into a 25amp outlet with nothing else in it and that is run directly to the electrical panel. Same problem.

I'm looking at dumping this head and getting an Acoustic B300HD. I'm wondering if the same thing may happen...
 
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#4
Sounds like the head is pooping out with lower impedance loads. Any amp will run hotter at lower impedances but it should handle 4ohm loads.

Only red flag is if your using parrallel jacks on your cabs to daisy chain. Thats totally fine.

Only concern is might be wiring issue or bad cable or jack in the cab or your chords.

Amp should be alright at 4 ohms.
Unless for some reason the cabs have been modded or changed by previous owner. Might say 8ohms but could be 4ohms. If it is for some reason . running both cabs would present a impedance to low and over heat it. Or since its cutting in and out. Could be loose intermittent wiring in the cab. Or a incorrectly bypassed tweeter which is causing problems.
 
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#6
From personal experience, I might question the cabinets. When I was in high school, my Dad bought me a really nice Kenwood stereo receiver and gave me a pair of vintage AR-2ax speakers. The receiver was rated for 8ohm per channel and the speakers were supposedly 8ohm cabinets. After about an hour, the receiver would shut down. After a couple trips to the repair shop, the tech asked us to bring in the speakers. It turned out that somehow the impedance of the speakers had dropped below the amplifier's capability.
 
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#7
Verify the impedance of each cabinet.

I have seen numerous repairs (and modifications) by folks who knew nothing about repairing speakers make a mess out of their cabinets because they took the advice of a self-proclaimed internet expert who was full of crap.

This is why protection circuits are designed into amps. There's always a possibility that the amp has a problem, but it's more likely the speaker IME.
 
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#11
Both are brand new cabs. Never modified. Here are the specs: https://assets.peavey.com/literature/specs/117420_10087.pdf

And here is the head: Invalid Link Removed

So far as I can tell, wiring the 2 cabs in parallel is giving me 4 ohms which the head should see and be putting out the 300w instead of the 180w at 8 ohms.

Btw, I just noticed that this head is a Class D. I have NO idea what that is.
 
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#12
Definety thermal protection kicking in.

A friend of mine bought a Berg...
Bass amp to run his Accorgan—-
An accordion type of instrument with the capability of producing bass notes with the left hand.
If he ran the bass too hard, thermal protection kicked in. I opened the amp and temporarily jumped out the thermal sensor— problem went away but I couldn’t leave the amp that way because it would self destruct.
The amp was not very ruggedly built.
With 2 cabs in parallel, you’re pulling twice the current.
Heat (watts) is a function of :
( current x current) x resistance
 
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#13
Slevage said:
Definety thermal protection kicking in.

A friend of mine bought a Berg...
Bass amp to run his Accorgan—-
An accordion type of instrument with the capability of producing bass notes with the left hand.
If he ran the bass too hard, thermal protection kicked in. I opened the amp and temporarily jumped out the thermal sensor— problem went away but I couldn’t leave the amp that way because it would self destruct.
The amp was not very ruggedly built.
With 2 cabs in parallel, you’re pulling twice the current.
Heat (watts) is a function of :
( current x current) x resistance
Click to expand...

I'll take your word for it. Now, is there a way to remedy this? I only have the amp at half volume. The gain and master knobs are both at 5.
 
#14
I really don't think it's thermal, it happens as soon as he connects the second cabinet. Thermal time constants are way longer.

It's possible that there is not enough over-current margin and something with the pairing of the cabinets is dropping it below the OC threshold.

Mistakes get made in manufacturing, it's possible that it's the amp but IME it's more likely the speaker.
 
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#15
agedhorse said:
I really don't think it's thermal, it happens as soon as he connects the second cabinet. Thermal time constants are way longer.

It's possible that there is not enough over-current margin and something with the pairing of the cabinets is dropping it below the OC threshold.

Mistakes get made in manufacturing, it's possible that it's the amp but IME it's more likely the speaker.
Click to expand...

No no! It happens when I start playing loudly and hit the strings more aggressively for that extra thunk. THEN it cuts out for like 2-3 seconds.
 
#17
Use good quality speaker cables. If you have a bad cable with 1/4” connectors for example, pushing the amp can short the cable at the connector. The amp sees a short and cuts out.

With a good cable, connect it to the cab. Measure the resistance at the end of the cable. Repeat with the other cabinet. See if the two measured resistances are more or less the same. If you are daisy chaining the two cabs, connect them and measure the resistance. See if it is as expected for a four ohm cabinet.
 
#18
I have no idea how to measure resistance...

Let me ask this: Take a look at the gear I linked below. How would YOU (meaning anyone here) wire it all together?

Head: [Invalid or Expired Link Removed]

Cab (x2): Invalid Link Removed
 
#19
agedhorse said:
2-3 seconds time constant is WAY too short to be a thermal event. (by a factor of at least 10)
Click to expand...
Yeah, my Ampeg would not cut out until playing for a while and then for like 15 - 20 seconds of silence at random intervals until I let it cool down. It had gain and master levels pushed relatively high also. Wouldn't ever do it with the 210 but I didn't generally play it with the master as high but with otherwise the same settings.
 
#20
I have that same amp head and I have run two 8 ohm cabinets and didn’t experience your issue. I did however have this problem with my Carvin 2x10 but, I cracked it open and found one the speaker wires had come off the terminal, I fix it and never had the cutting out issue again. IMO it sounds like a cabinet issue. Do you have anyway to test the head on two different brand 8 ohm cabinets? To find out if it is the head?
 
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