I have two Kicker comp VR 12" subs on a Soundstream VGA 1600.2, and a four channel Soundstream VGA 640.4 which runs four infiniti kappa 5x7 giving them 80w RMS. At certain volumes, the kappas cut off and to get them to come back on, I turn the volume down. What is the problem? They are not all that loud when they cut off and they only do it when on the CD player, not the tuner. If the I have the volume up to about 20 on the HU and I am listening to the CD player they cut out. With the tuner, I can turn the volume up higher an they wont cut out. The tuner is an alpine CDA 9847. I dont think it is the HU or the amp as the amp is never hot and the protection light is not on. HELP.
First try checking the voltage going to that amp at the cutoff volume. Make sure it's not dipping much lower than 12 volts. If that's OK then try hooking your sub amp to your front or rear outputs to see if it is the head unit. Try the same with hooking the sub output to the 640.4, just don't forget to change your crossover point.
-------------
My wife will never understand why, lucky for her!
...and make sure the 5x7's are crossed over at the amp through a high pass filter.
Also check your ground, I have seen a few cases where a poor ground connection has caused this. When you turn the tuner on, it will pull ground through the antenna(reason for not shutting off on tuner).
Make sure you have good connections to a bare chassis.
-------------
To me it sounds like a head unit issue.
-------------
Top Secret, I can tell you but then my wife will kill me.