subwoofer power hogging

Hey guys, need some help here. I'm currently running 2 Alpine SWR-1242D 12' subs in a ported box, the subs are rated for 4 ohms. I have a Kenwood 1800 watt KAC-9103D mono amp driving them. When they 'hit' they both sound great! Ok, now the problem. Sometimes they both 'hit', sometimes not. When I turn the power on/off the head unit, this can 'change' the bass response (seems like on the left side) which is odd in and of itself. Both subs are working, but when they don't 'hit', it sounds like just ONE of the subs is doing most of the work. (the right sub). Sounds like it might be happening on the left side only. Sometimes I can hear the bass decrease in the left sub as run the HU for a while, sometime I can hear the bass increase in that same left side as well, sometime they BOTh hit well for a while, but if I leave the HU off for a while then turn it back on...same issue. I've also checked the wiring inside the box and all is good there ;-) I've replaced EVERY component, including the head unit, amp, pre-outs, and speaker wire...EVERYTHING...SAME problem. The ONLY thing I can think of, is that I have them wired correctly (according to Alpine's diagram), but INDEPENDENT of each other, in other words, I have BOTH a left and right terminal input on the box, and have each sub wired directly to the amp but not DIRECTLY to each other within the box...should that make the difference? I hope so...because I've run out of options here ;-( Thanks to whoever responds!

Make sure that you are experiencing the problem while listening to the same recording-song. If the problem exists only on certain songs you may be experiencing problems that only sound like one sub is dropping out. If the output is actually dropping when driven hard and then returning to normal after you shut down and restart the system I would suspect that your amplifiers power supply is being over taxed. That can happen because either your subs are presenting to low of a load or the amplifier is being starved for power. I suspect that your amp might not be getting full power at the input terminals. Check your ground, power cable size, fuse holder connections, battery connections, and check for corrosion both at the connections and in the wire ends. Has your system always done this or have you just recently installed it or changed something? Also as long as the subs are wired correctly it dose not mater where the connections are grouped together (in the box or at the amp). If you suspect that the problem might be in the signal getting to the amp from the head unit, then wire your two subs in series temporarily. If the problem goes away you have narrowed it down to the amps power supply being over taxed. Recheck your power wiring

Changed the car battery. Problem appears to be solved. I'll have to give it a few days to make sure. This issue had been getting progressively worse since the install, so no it wasn't always like this. The old battery was starting to corrode, and the 4 gauge wire I had connected to it was not a prime connection to begin with. Do you suggest I also change the terminal plugs as well? I cleaned them out as best I could. Also, will my system KILL my new battery as well at some point? Like I said, I pretty much swapped out ALL my components only to find out that I just needed a new car battery!!!...don't I feel like a dope ;-(

I would check your wiring...both subs should be getting the same signal

Ok...here's the deal now. Alternator has NOW been replaced as well. It was practically 'dead'...only kicking out like 20-30 amps...Owch!I've also re-grounded my amps and cap DIRECTLY to the chassis in the trunk...now difference. Issue remains the same..BETTER now that I have the new alternator, but base still 'weakens' on one side as the system is driven for a while. When I first turn on the system, It sounds GREAT for the first few minutes...then the issues!Thinking of attacking (replacing) the ground wire the the battery now. Would that make any difference. I've already changed the terminal to the battery, but not the ground wire to the chassis itself.I also noticed that the new battery is now starting is showing signs of corrosion on the positive terminal? Any idea why? I still think that I'm over taxing my battery somehow...HELP!!Ok...here's the deal now. Alternator has NOW been replaced as well. It was practically 'dead'...only kicking out like 20-30 amps...Owch!

Back once again. OK. Same problems (sort of). Made some changes...BUT What I noticed over the summer, is that while driving at a higher RPM, (highway) the system sounded GREAT..BUT...city or night driving had a NOTICEABLE difference in bass response...no surprise. I'm assuming it is because of the extra draw on the alternator...whatever. SO...The first thing I did was change the car battery's GROUND cable with a 2 Gauge Ground cable found in most auto part stores. In my car, this cable grounds in 2 places (2000 Nissan Maxima)...(1) to the chassis, and (2)to the engine block. After doing this however, the bass response seemed to get much, much WORSE not better, and actually seemed to change the frequency output of the amp/subs somewhat (very weird!) Now I'm starting to get wizED off! So thinking it could STILL be the the battery, I upgraded THAT to a yellow top Optima...BIG difference in power output, but bass continues to 'sound' different... and sub amp seems to fluctuate it's output to the subs...it just does it with more 'juice' now... Guy at my local car audio store seems to think that my amp might be bad...so I'm beginning to address that possibility, as the Kenwood sub amp cannot seem to replicate the power output to the subs every time I turn the system on/off. Also noticed the lights 'flicker' a bit on a 'bassy' track...where before (I upgraded the ground cable) they didn't...that I noticed. The other 200 watt amp (powering 2 sets of Infinity separates) sounds just FINE...BUT it also has no real bass demands, either, as I have the freq. tuned to eliminate most bass to the separates.. I've also checked all 3 grounds in the trunk...No problems there either Still have the cap installed as well... Could the amp be bad somehow?? Only had it since May '07... Paul Anyone have any ideas now??