Q I have a MTX Thunderform custom enclosure in my 1994 Chevrolet extended cab. At a volume of 13 the bass hits fine, but is not very loud. When I turn the volume up, the power light on my amp flashes and the bass cuts in and out. Why is it doing this, and how do I solve it?SteveVia the Internet
A Although you haven't revealed what amplifier you have, the problem is common enough that I can venture a pretty good assessment. Bass cutting in and out is one thing, but the notable symptom here is that the power light on the amplifier flashes. This almost always indicates a power supply problem resulting from the installation. In most cases it can be traced to either a faulty ground lead or faulty power wiring. Confirm that you have the right gauge of wire and that all the connections are secure.
If the problem persists, check the voltage at the amplifier with a digital multimeter. It would be a good idea to find one with a Minimum/Maximum function that will record the lowest voltage that the amplifier receives. If bass notes cause the voltage to briefly fall below 11 volts, you are outside of the operating window for the amplifier. If your wiring is adequate, you may have a charging system problem developing. See your local installer for a solution.
Q First off, I love your magazine. My problem is with my sub bass. I have three Soundstream SPL 10" dual voice coil subs, running off a Soundstream 702. The subs' voice coils are wired for 8 ohms, and all three subs are parallel wired together, with the 702 in mono. I get low output from my subs; when I turn up the volume, the amplifier's clip indicators light up and the output is cut off until I turn the volume down.
The 702s inputs are set to 5 volts, while my Alpine audio processor (ERA-G320) only puts out 4 volts. My amp has been sent out for repair three times now, as the internal resistor keeps burning out. They are sending me a new amp rather then repair it again. The shop I go to insists that the problem was simply a faulty amp, but I suspect something else. Could the impedance be too low for the amp to handle? Also I asked around to different shops, and one suggested that the subs wiring might be too close together, causing them to arc, and shorting out my amp? Could this be the cause? Thanks for your time, keep up the good work.Any help would be greatly appreciatedSteve PappVia the Internet
A First off, here is a warning: the individual who thinks that the sub wiring is "arcing" because it is too close together is probably not an installer. Arcing is a function of high voltage, and would only occur at voltages well over 250 volts AC, even on cheap "lamp cord" speaker wire. If you were achieving voltages this high into your 1.3-ohm speaker array (3-8 ohm dual voice coil subs in parallel) you would be developing power in the range of 23,400 watts! The only way you could expect to see arcing is if you wound your sub wiring around your spark plugs several times. Find a knowledgeable installer.
Although the Soundstream Rubicon 702 is listed in the 1999 Car Audio and Electronics magazine directory edition as being, 1 ohm stable, I don't like to see any amplifier run that close to the "red line" unless it is a "mission specific" "arc welder" of an amplifier, destined for competition type usage. When any system or vehicle operating parameter shifts, there is an increased likelihood that an amplifier will simply "blow a gasket" (enough use of clichs for you?). You should consider reconfiguring your subs into a series-parallel arrangement that will be centered within your power band instead of at the edge.
If your regular shop is a Soundstream dealer and feels that your particular amp is faulty, that may be the case. Having a manufacturer that will replace a repeat failure with a new unit exemplifies both a quality manufacturer and a quality product. The best course of action is to see what happens with the new amplifier installed.