Help! Weird behaving Amp and Speaker combo


New member
Username: Thuzmund

Albany, New York

Post Number: 1
Registered: Jan-13
I was given a integrated PA unit--the kind with power and speaker in one box. It even has a battery for portability! Cool! The old owner said the power would turn off, I took it all apart to look for loose connections or anything visually obvious. Checked out OK.

The speaker box has a subwoofer and a high-frequency tweeter. The tweeter has a connector allowing two sets of speaker wires. Only one was connected when I got it.

Here's the weird issue: If I connect that additional set of speaker wires, the amp light will glow very weakly and not turn on enough to produce any sound. If those same wires are not connected, the amp will turn on and produce sound.

1) Any idea what's going on?
2) I imagine that the second set of speaker wires has to do with a frequency splitter and leaving it disconnected will result in crappier sound (it seemed a bit low and muffled to me during voice testing). Does that sound about right?

Here is a pic of what I'm talking about:

I really appreciate any wisdom that's shared with this amateur musician!

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17688
Registered: May-04

Looking at the picture, my guess would be the connections on the driver are not the issue. The cables exiting from the crossover are your problem. Or, more appropriately, the fact you connected cables that weren't meant to be connected is your problem. The cables were disconnected when you received the speaker. That's not a reason to connect the cables. The rule of "just because you can doesn't mean you should" applies here. Overall, that's a pretty good rule to remember.

Is there a reason you can't contact the speaker's manufacturer? They could tell you more about the speakers than anyone on a forum might. Failing that, a repair shop that services the speaker brand might be helpful.

I'm going to guess the additional cables are for another portion of the crossover circuit. Mass production techniques today mean boards are built for multiple purposes and can be used in several different components. They are installed in many systems and connections are made which are correct for the specific application. So it's possible the crossover board is not specific to this speaker and it is used simply for cost reasons. It's cheaper to buy a generic board and not use all the connections than it is to purpose build a complete crossover for this specific speaker.

The additional cables coming from the board might be for a different crossover frequency, either to accommodate a midrange in another more expensive system in the manufacturer's line or to tailor the response of the crossover to another system. The additional connections at the tweeter itself are a red herring - lots of drivers have similar connections for different uses - and have nothing to do with your problem other than allowing someone not entirely sure of what they are doing to make a mistake.

By connecting both pairs of cables to one driver you've likely joined two circuit parts in a way they are not intended to be connected. You haven't created a shorted circuit path since the caps and coils in the crossover will tend to isolate the circuit from your mistake. But you've made life difficult for the amplifier. Under these conditions the protection circuitry in the amp is thrown into the voltage path and it does what it is meant to do, protect the amp from catastrophic failure. The amp will not power up until the connection has been removed.

If this guess is correct, you might want to look more closely at the crossover board and the point where these cables exit. The board could have some indication of why these cables exist. It might be labelled "mid" or with a specific frequency which would indicate their purpose. That would give you a bit more information as to their purpose.

But the fact the cables weren't connected when you acquired this speaker strongly suggest they are not intened to be connected in this speaker. The fact the amp won't power up when they are connected says that's a pretty safe assumption. The fact the speakers seem to operate as planned when the cables are disconnected make this an almost certainty. Why the amp would shut down for the previous owner is more likely to be the way he used the system - too loud for too long and the amp went into protection. That is another issue to be dealt with once you get the system up and running.

But, remembering that rule "just because you can doesn't mean you should" still applies here. First, you risk damaging the speaker system if you don't understand what you are doing when you poke around inside the cabinet. A dropped screwdriver can wreck the amp and not make for a good day for you. Second, and far more importantly, there is likely to be a label on the back panel of the speaker that states "No user serviceable parts inside". You know why that label is there? Liability laws. The manufacturer doesn't want to to kill yourself by sticking your hands where they shouldn't be. If you don't know why cables exist but you go ahead and connect them to any open point you can spot, it's also a good likelyhood you don't fully understand what you are doing in an electronic circuit. Just because you can doesn't mean you should have your hands inside a cabinet with an amplifier powered by 120 Volts and 15 amps of electricity that is waiting for the wrong move by someone who does not understand where not to stick their hands. Power supply caps store energy and they can still grab hold of you even after the amp has been shut down and unplugged for some time. That lable is there to warn you of the potential of danger and death. Quite literally, you could place your hand somewhere without thinking while looking around inside this amp and you would be fried in a very few seconds. Once 120V grabs you, you almost certainly have no ability to let loose of the AC voltage. I would strongly urge you not to poke around where you don't belong. If the system operates, let it do so without your further assistance. If the amp has problems, take it to a qualified repair shop and don't risk your life for the sake of a freeby speaker. Just because you can is not a good enough reason to say you should.


New member
Username: Thuzmund

Albany, New York

Post Number: 2
Registered: Jan-13
Thanks for the advice, Jan, and for a thorough and thoughtful response. It is illuminating to peer into your problem-solving steps.

I was able to make contact with the manufacturer, who sent me this, along with instructions on replacing the battery unit:

Your unit requires good batteries to function properly. The power cord supplies barely enough current to turn the unit on and charge the batteries.
When the batteries are worn out and the speaker is required to put out high levels of audio, the batteries will sag resulting the in the unit powering off. With the power switch in the off position, the charge indicator (top light ) should be flashing indicating fully charged batteries, however the battery monitoring circuit is actually measuring the charge voltage. If you disconnected the batteries with the power switch off, the light will still flash fully charged. Your unit needs two new batteries. They can be found locally since they are not proprietary (used in alarm systems and emergency lights ).

Your high frequency driver should only have two wires connected to it. Any additional speaker should be connected to the speaker out jacks.

Here for posterity and future tinkerers.
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