Q. Hi, I have run my problem by everyone I know with an electronics background, and nobody can help. I have a 400 watt Jensen 4ch. amp pushing two 10" Rockford Fosgate HLC subs. I've had the system installed for about three months. For the first month, everything worked fine. But about two months ago, the sound would randomly cut out. I have watched the amp, and the power light is always on, and the emblem doesn't stop glowing, so I'm guessing it still has power. Sometimes the sound turns on and off when I go over bumps, but it also goes off sometimes when I'm parked, or at a stop light. I have checked all my connections, and they are all solid. Any suggestions are appreciated.
Chris DiChiara
Via the Internet
A. Dealing with intermittent problems is always an exercise in frustration, especially when a professional installer is hunting the problem in a customer's vehicle. You have the benefit of always being around when the problem reveals itself, but that is offset by the liability of not having the troubleshooting skills that the pro possesses.
While your message focuses on your amplifier and subs, I suspect the problem is not there. Since your amplifier's indicator light remains on, you're probably right in assuming that the connection to the battery is likely not being affected. There is a possibility that a very brief interruption is causing the amp to cycle too quickly for the indicator light to reset, but I'd put that at the bottom of the list.
The two paths that you can follow in this instance are either a product fault or a connection or cable fault. If you have no clear symptom pattern that would lead you to highly suspect a component, you will need to use a process of elimination. Hopefully the problem occurs often enough that you don't have to wait weeks to determine if a course of action yielded results.
You haven't provided a complete list of your system components or how they are connected, so we'll assume that sound cuts out only on the subs when the problem occurs. Divide your system at the point where you can separate the problem area from the functional area. In a typical system, that would be where the system divides into different signals for different amplifiers. In your specific system, it would be at the input of the electronic crossover or dividing network.
Temporarily run your subs with a full range signal from before the dividing network. This will likely require a "Y" adapter unless you have a set of preamp connections that are available. It won't sound very good, but the purpose is to see if the problem occurs when bypassing the dividing network. If the problem is gone, your dividing network or crossover has an internal fault. If the problem is still present, you have eliminated everything upstream from and including the dividing network. Substitute preamp cables and speaker cables and finally the amplifier until you localize the problem.
Q. I have a question. I have Infinity Kappa speakers in place of all my factory speakers. I was playing around with the balance and fader and I noticed something weird. When I fade the music to the back and all on the rear left speaker, all I get is higher frequencies. The back right though seems to work all right. But then when I have them both playing music, they both work fine. I have a Pioneer tape deck, but I don't think that has anything to do with it. I was also wondering if it could be that I'm running my JL subs bridged. My owner's manual for my amp says that if you bridge the subs you will use the right gain on the amp and not the left. Could this be why my mid-ranges don't work the same when they're faded side to side? I have no idea what it is so I'd appreciate some advice. Thanks.
Ryan Ewers
Via the Internet
A. The most likely cause would be a two-way speaker that has a bad woofer, so I would triple check that before you move on. One of the easiest ways to check is to swap speaker wires between the two rear speakers. If the problem moves to the other speaker, then it is not a speaker fault.
If your rear speakers are sharing the output of the amplifier with the subwoofer, then you can have interesting effects occur when you play with the balance control depending on the amplifier used. Most notably, your subwoofer output can diminish, creating the illusion that the Kappa's woofer is not working on one side of the vehicle. This can affect a variety of "mixed mono" capable amplifiers and is fairly normal, providing everything works well in the center balance position.
Q. Hello. I hope I'm not bothering you, but a friend of mine told me that you could answer a technical question for me. Here goes: I bought two of the Alpine 10" Type R Dual Voice Coil subs (SWS-1040D). The impedance is 4 ohm + 4 ohm (obviously!). A technician told me that I MUST wire up both sides of the voice coil, in parallel or series, making it a 2-ohm or 8-ohm speaker, respectively. Is this true? I can't just wire up only one side? I want a 4-ohm speaker! Please let me know if you think the technician is wrong. Any help you'd give me will be highly appreciated.
Thank you!
Respectively,
David Derr, Faithful Reader
Via the Internet
A. There are two contexts for this question. The minor context is technical and the major context is functional. The technician is technically wrong on the minor point of insisting that both coils MUST be connected, but is correct on the much more important broad topic of why you MUST connect both coils for functional reasons.
If you were to connect only one set of coils per speaker, your amplifier would encounter a load of 4 ohms, as you wanted. Nothing would blow up, or shut down or cause any other problems. In contrast, leaving one wheel off of a motorcycle is definitely a problem. The only real opportunity for a problem is if your unused coil connections were to short-out or contact chassis metal.
The major topic is "why would you ever use only one coil of a dual voice coil woofer?" You likely don't need a 4-ohm speaker since almost every amplifier made for at least the past three years can easily handle a 2-ohm load without a problem. You haven't specified what amplifier you are using, but I would bet it was designed to function properly at 2 ohms. In addition, by not using both coils, you are depriving yourself of the maximum performance that a dual voice coil subwoofer can provide.
Also with a dual voice coil speaker you can connect all four coils in a series parallel arrangement that provides 4 ohms. This resulting load can be connected to a bridged amplifier with great results.
The flexibility of dual voice coil speakers also allows you to add another pair of the same woofers later, and use the same amplifier now connected in stereo at 4 ohms per channel. As you continue to build your system, you can add a second amplifier, bridge both of them and gain the benefit of increasing your system performance one economical step at a time.