Lack of Subwoofer output

[sleeprae]

Okay, here is my setup: 1993 XLT w/factory alternator.
I purchased and installed the following:
1. Pyramid (POS, I know, was free) 800-watt amplifier powering 4 Pioneer TS-A6857 speakers
2. Kenwood KAC-929 1000-watt amplifier (460x1 bridged rated RMS output) powering (1) Kicker CompVR 12" subwoofer (Rated for 400-watts RMS)
3. JVC KD-SX980 MP3 HU
4. Harness kit/amp bypass for premium audio.

I replaced all the door speakers and installed the amp bypass. I have RCA Low-level inputs (coming from HU) going to my two amps, with the front channels split to divide the signal between the amps. The door speakers work and sound great - but the subwoofer seems to lack punch. The cone moves, and it makes sound, but it's not near as loud or powerful as the CompVR should.

Wiring: #4 wire going from the positive block next to the battery to a distribution block (Rated for 600-Amps) near the amps with 3 #8 wires coming out, 2 hooked to the Kenwood and 1 to the Pyramid. Fused at battery with a single 100-A fuse. One #8 ground wire per amp connected to the chassis plate below the factory cupholder (that is where the two amps are mounted). This cable is about 12" long.

Problem:
As I said, the subwoofer doesn't hit near as hard as it should. I suspect power wiring, but was hoping someone here could shed some insight as to where to look. I have a suspicion that I'm not getting enough power from the battery/alternator to the positive block thing mounted to the chassis next to the battery. When the bass does hit, the lights dim significantly.

Also, does anyone think that I should buy a new alternator? My estimate is that the two amps pull a combined 80 amps or so, maximum. I've read that Ford uses a 95-amp alternator stock. Can anyone confirm/deny? Thanks for all your help!

 

[Alec]

You may need a new alternator, but you may want to try installing a capacitor for the sub amp.

 

[white96x]

i agree-also, you should use the same gauge wire throughout.......if you used 4 awg from your battery, then should have also used 4awg for your amp power input as well as to ground it.

 

[flgatorz10]

Read all of this post!

If you ran 4 gauge wire from the battery to distribution block, then you'd be experiencing heavy dimming before the amp lost enough voltage to start losing "punch". I have a feeling that your gains aren't set properly. Play with them, but be careful, and listen for distortion.

The 1993 XLT came with a 95 amp, stock. Mine failed, and I replaced it with an alternator rated at 135 amps, though it's been tested to put out up to 150. The replacement cost $110, from an auto parts store, and I did the labor myself in under 15 minutes. I wouldn't have replaced it if it hadn't failed, altough the 95 amp stock replacement was $120. Made my decision easy.

I have a US Acoustics USX800D and a USX4065. Combined, these amps pull about 60 amps continuous. However, I used to have 2 Ultimate Sound (unreliable) amps, rated at a total of 2600 watts peak, and these supposedly pulled 100 amps. Even with these amps, I didn't experience dimming. I ran 4 guage wire, and had 2 batteries in the back, 18 inches from the amps. This defiently won't be necessary for you, but I'm making a point about the 4 guage wire. An added bonus...I've jumpstarted myself with those batteries.

White96X, not all amps accept 4 guage wire. Actually most don't. Yes, it is possible to cut some strands of 4 guage off to make it fit, but using a distribution block is cleaner, and easier to add lights/neons later.


Hope this helped....

 

[white96x]

Most high wattage amps DO accept 4awg wire, but you are right a distribution block would be easier if his amp rated at 1000 watts(it should accomodate 4awg wire) doesn't.

 

[Kevex]

Before you do anything, I would say play with the rca's some, like switch them from the 1 amp to your sub amp and see if you notice and difference. Do you have the fader set correctly on the HU? From what i read, you say that your'e using only one set of RCA's is that all thats on there?

 

[white96x]

correct me if i'm wrong but if his RCA's were bad he wouldn't be getting ANY sound out of his subs......

 

[flgatorz10]

White96X, I don't want to start an argument, but I do want to back up my point so I sound like I know what I'm talking about.

His amp is a Kenwood KAC-929. The Kenwood website does not give current draws, but assuming this is a class AB amplifier (least efficent design) this amp would have at least 50 % efficency. 460 watts/13VDC = 35 amps, at 100% efficency. So, that's 70 amps at 50% efficency. 15 feet of 8 gauge wire can handle 70 amps all day without heating. Also, the Kenwood website doesn't give fuse rating, but the picture shows 2 green (30 amp) fuses installed in the amp. So, this amp would draw 60 amps, max, still under what 8 guage can safely handle, so realistically, Kenwood probably wouldn't put connectors capable of 4 gauge on an amp that didn't need it.

Kenwood isn't a great brand for power amplifiers. I guess they're decent for the price, but I'd try US Acoustics, DEI, Orion, MTX, etc, especially for driving subs.

RCAs can be sut or shorted, and as the vehicle moves, the wires short, sometimes even standing still. I'd try hooking up a totally independent system to the amplifier, like a portable CD player or something, and see if the problem is there.

 

[Kevex]

possibly they weren't pushed completely together, not getting good contact, just a thought besides everyone telling him about the wire size and the alt. figured it could not hurt to check them with the RCA's run just to the sub instead of being split.

 

[white96x]

ya kevex-you make a good point-
back to the gator guy: i never questioned your knowledge of audio-you sound like you know what you're talking about-all i was saying was that all the high wattage output amps that i've dealt w/such as kicker and fosgate have all had 4awg compatible inputs, i honestly don't feel you should have to explain yourself to me or vise-versa b/c i know what the hell i am talking about too-i didn't go get the specs on his amp i was just making a point that most high output amps have 4awg and lower inputs.........

 

[boominXplorer]

go to a car audio store and order the audio control epic center. its about 220$ it will make a sub soud 3x better

 

[sleeprae]

Further study has led me to discard power as the source of my problems. Yes, the lights dim significantly when the bass hits, but the Kenwood has a power level indicator that I did not know of intially. The entire reason I am using it is that I was able to acquire it from my brother for $75. (He upgraded to a higher-end JL Audio amplifier) The Pyramid was free.

I have 4 RCA's coming from the back of the HU, the front two were initially split to both the Pyramid and the Kenwood, with the rear two going into CH3 and CH4 input on the Pyramid. I've since changed that to use the unsplit rear RCA's for input into the Kenwood (higher voltage signal - better quality output)

I also tried replacing the subwoofer speaker cable I had ran. This seemed to make a big impact. I wonder if the cable got damaged somehow when I snapped the plastic side rails back into place. I also tried hooking up a Kicker ZR360 amplifier to it to see if it made a difference - and it did sound cleaner, but when I hooked the Kenwood back up, it sounded nearly as good and as loud. I played with a bunch of settings and the like during the whole exercise, but now it's sounding about where I'd expect it to. I think at this time I will not purchase a new alternator, but I will try the .5 farad cap we have around here. Ultimately, I don't know what the problem was. It seems like every modification I made helped a little bit.

Flgatorz10 - I agree with your assessment that #8 wire is plenty. After kicking both amps hard for 30 minutes or so, the wires were not even warm. However, the plate I grounded to was a bit warm, so I may try running a cable from the battery negative terminal to that plate. I want to thank everybody for their input. If I have further problems (like when I remount the amplifiers - they're pulled out and exposed for purposes of convenience of working with them) I will not hesitate to ask again. Thanks!