ohm and head unit question

[sean123019]

I am trying to run a 2 ohm system and can not find any information on headunits. I got my amp which i thought was the last piece of my system. After wiring everything the the sub and the speakers cut out at around 40% volume. Did a little research and the headunit says it's speaker impehdance is only 4-8 ohms. I have 2 pioneer premier subs capable of 2 ohm, (can post more specs if it's necessary) and a pioneer mono 2 channel 2 ohm capable amp (again can provide more specs). Only one sub is wired to the amp, the other just sits pretty in the box atm. Now my question, is the headunit the problem in this case. I ran the same sytem in 4 ohms off a different amp and it worked fine. Also the power wire to the amp is 4 ga where as the ground is 6 ga, could that be the problem now since im running a more powerful amp? I have not been able to find a 2 ohm capable headunit so is there some fancy way i have to wire the headunit for 2 ohms? I never found any mention of checking the impehdance on the headunit from reading many articles, only to match the rms and impehdance of the subs and amp. Hopefully one of the smart people here has all the answeres for me .

[01bonne]

You could be starving your amp for power when you crank your system. I had the same problem and had to add a second battery. Here's a diagram to wire your system to 2 ohms http://www.the12volt.com/caraudio/woofe ... p?Q=2&I=22

[sean123019]

The link you posted was for wiring the speakers which i know are wired correctly, is adding a second battery the only solution? Currently only running 1200w with 1 farad cap, I wouldn't think a second battery would be needed after a big 3 upgrade.

[01bonne]

No its not the only solution, it was MY solution to the same problem.

[Bugsi]

The impedance load rating of your head unit is a rating for driving speakers directly from the head unit. If you're using an amplifier to drive your low-impedance speakers then the head unit rating doesn't come into play. The amplifier is a high-impedance load to the head unit, so no, the head unit will not generaly be the cause of your cutoff, unless the head unit has failed in some manner, such as putting out DC voltage on its outputs.

Your cutoff is more likely to be either an input overvoltage protection, or it could be an overcurrent protection, or it could be a circuit failure in the amplifier. Addressing these in order:

Input overload can occur if you have the input trim on the amp too high, and if your head unit output produces high voltage output on the order of 4 to 8 volts peak-to-peak, where some amplifiers are looking for 1 or 2 volts peak to peak. You'd need to check the input voltage handling of the amplifier, and compare to what your head unit puts out. Ideally you'd put an oscilloscope on the output of the head unit to measure the peak to peak voltage when playing a sinewave test tone from a test CD. If you drive the input buffer of the amplifier into clipping, the overvoltage protection circuit can kick in.

If your speaker is presenting too low of an impedance, it will look just like a short circuit to the amplifier. The amp will try to sink very large currents from your battery. Your battery and wiring will either provide the required current, or it will fail and provide less. If it fails and provides less, you'll get voltage sag, and that can kick a cutoff in your amp. If it can provide the current, the amp might kick an overcurrent protection. This would happen if you have a wiring short, or a shorted sub voicecoil.

Finally, when amps fail, they will often fail in a portion of one of their protection circuits. If the protection circuits kick in when everything else is normal, it usually indicates a failure and you'd want to get the amp tested or replaced. The trick here is being confident that everything else is normal. You often won't know that for certain unless you pull the amp and test it with some other "known to be good" testbed.

So it is remotely possible that it could be a head unit problem, but not as likely as something with the amp, the sub, or the wiring to both.

-Mark