ZX400 causing lights to dim

Kaptain · Post by **Kaptain** » Sun Jan 25, 2009 2:55 pm

What I got:
Pioneer Avic-Z2
Stock speakers
PG ZX400Ti 2ohms briddged
Eclipse SW8102DVC 10" sub (4ohmx4ohm)
Installed in a 2007 new body style Silverado

I have read enough threads on dimming headlights to make my eyes hurt and my head pound, and I still cant resolve this issue.

I have had this system installed in an 03 and an 05 silverado in the past with no problems. With the exception of an Eclipse head unit.

Power and ground to the back seat are supplied by PG 4gauge wire.

What I have done so far to fix this problem:
First, my silverado has an alternator rated for 140amps so I upgraded the 8ga wire from the alt to the battery with 4ga. I also added a new ground from the battery to the body of the pickup. Problem not solved.

Next, Installed a new Interstate battery. Still not solved.

Next, I unhooked the negative 4ga ground from the amp and did a continuity test from the battery to see if my ground at the amp was good, it was solid

Next, I tried add an additional battery in parallel, this did not solve the problem but it may have helped a tiny bit. It was hard to tell the difference.

Next, at this point I have been willing to try any idea so I started to think that I reset reset my sensitivity settings on the amp, maybe I was pushing the amp harder than I needed.???... So thanks to this phorum I correctly adjusted the sensitivity of my amp. With the sub gain at the headunit at it's lowest setting, the LPL all the way up, I acheived 37.5 VAC at the amp while playing a 60hz sine tone. Bass gain was left all the way down. Poped in a different song and turned it up, still dimming.

Now I have a few more idea's to try. First is to add a line driver to the Z2 head unit since it only puts out 2 volts and in the past my eclipse units put out 8. I dont know if this will fix the problem but I ordered one anyway. It will be here next week.
Last idea is to get a battery isolator and add the second battery, however this will be a pain in the rear and I really don't think it will solve the problem.

To sum it up, do you think the line driver may fix this problem? I could add additional wire from the engine block to the firewall, however GM used a fairly large ground so I don't think it will be necessary.

I really hate to post this question since I have found many posts all over the web, I just cant seem to nail down this problem.

Oh, and when I say the headlights dim, they only dim enough to drive a person crazy at night. I have checked my voltage and it never drops below 13.3volts on a good bass note.

Am I forgetting anything?

Grim0013 · Post by **Grim0013** » Sun Jan 25, 2009 4:31 pm

If you've got 4 AWG wiring, that should be adequate, and 140A should also be adequate if you're just running that one amp. Before tossing a bunch more money on another battery, there are a few cheaper things to try. Adding a ground wire to the alt may help, instead of relying on it being grounded through it's mounting bracket. Next up, you can get a PG 1 farad cap for like, $60. I know a cap is considered by many to be a band-aid when it comes to fixing dimming, but in certain circumstances (like already having proper wiring in place) it makes sense. I would try that if you still have dimming with your wiring completely upgraded. I really don't think you would need a higher capacity alternator with that amp, given that you have a 140A unit already, and I definitely think adding a second battery is a total waste for such a moderate system.

thedeal7235 · Post by **thedeal7235** » Sun Jan 25, 2009 5:11 pm

PG ZX400Ti 2ohms briddged

also noticed ur saying 2ohm bridged?, if thats the case, that mAY be ur problem; yes that amp will work at 2ohm bridged, but current limited? how do u have the sub wired?i noticed it says 4ohm, but is it svc, or dvc???? i just checked the specs and it doesnt state this, but if u look at the old original(white) zx series, their manuels state that if u bridge 2ohm current is limited, hope this helps-

thedeal7235 · Post by **thedeal7235** » Sun Jan 25, 2009 5:31 pm

i just wanted to add that i have an audi (stock alternator is 150amp), and i run a zx475ti, ti600.2, and rsd 1200.1, and ive never had the headlights dim, and i have a voltage display that varies(bass notes hitting), from 14.1-13.2 volts) i hope more people can chime in to help out, the more i think about it, it seems like u have the bases covered on wiring/ and upgrade gauge sizes-my opinion is as ive stated, check and make sure ur bridging that amp to 4ohm bridged and not 2ohm bridged, all i can think of??????

Post by **stipud** » Sun Jan 25, 2009 5:35 pm

37.5v AC at 2 ohms is 700 watts, trying to squeeze out of a 400 watt amp.

You might want to try sqrt(400 watts * 2 ohms) = 28 volts, or a hair more.

The amp is 4 ohm optimized however, so your efficiency is going to be lower than normal running at 2 ohms. You might also want to try running it at 8 ohms... you might be surprised how loud it is at that impedance, and it will be much easier on your electrical system.

thedeal7235 · Post by **thedeal7235** » Sun Jan 25, 2009 5:38 pm

so, was I on the right path, if he is running it bridged 2ohm? ti manuel doesnt state this, but the old zx do-btw the google formula is a life saver stipud!!!( never had any issues since using it, i use to tune via ears, at 39, i MUST have some deafness by now-

Post by **Jacampb2** » Sun Jan 25, 2009 5:39 pm

Give this a shot if you have time. Check the voltage drop at the headlight connector while the bass is causing the dimming. You may find a significant voltage drop there. If so, you can upgrade the wiring to the lights. I know it is a PITA, but if you are not noticing a significant drop at the amp, and the lights are dimming, you are going to find there is a decent size drop at the lights. I can *probably* dig up headlight wiring diagrams for that truck if you need them.

Later,
Jason

Kaptain · Post by **Kaptain** » Sun Jan 25, 2009 7:02 pm

My eclipse SW8102 is a dual voice coil sub wired in parellel and bridged to the amp creating a 2ohm load.

It just seems strange to me that not only did it this setup work in my last two pickups, it also worked well in my 86 Monte Carlo that had a 100 amp alternator. Ya it ate a few alternators but I didnt have any dimming problems.

I will try grounding the alternator first. I will also try wiring the sub to the amp at 4 ohms stereo and see what kind of results I get.

If I wire it to 8ohms bridged how much power will the amp be putting out?

No one chimed in about the line driver. I ordered a TLD22, do I really need it?

thedeal7235 · Post by **thedeal7235** » Sun Jan 25, 2009 7:22 pm

ive always used line drivers, to help get good signal to my amps, but dont know, espicially if ur @ 2ohms if thatll fix the dimming light problems, unless ur putting the sensitivity higher than it should be- but u used the DMM method for tuning, so i think try what ur talking about, and the sub @ 4ohms, and see how that goes; imho, a line driver is always a great idea, oh, and as stipud mentioned google sqrt(4*400) for ur dmm setting at 4ohms

thedeal7235 · Post by **thedeal7235** » Sun Jan 25, 2009 7:25 pm

oops mayb do the 4 0hm stereo sqrt@(4*200)? , that is if its wired stereo to the amp, if bridged at amp 4ohms then obviously sqrt(4*400)

thedeal7235 · Post by **thedeal7235** » Sun Jan 25, 2009 7:37 pm

sqrt , if u kept it 2ohms bridged would be 28.28, or the sqrt (4*400)=40 for true 4ohm bridged, or the sqrt(4*200)=28.28-see how similiar that is to the 4ohm stereo, its the same, but the 38, like stipud said, the amp was(is trying to produce 700 watts-which, inho, would make the most sense why the lights dimming-good luck, and let us know the results-

Post by **stipud** » Mon Jan 26, 2009 7:22 am

Kaptain wrote:I will also try wiring the sub to the amp at 4 ohms stereo and see what kind of results I get.

If I wire it to 8ohms bridged how much power will the amp be putting out?

4 ohms stereo and 8 ohms bridged are one and the same. If you have a mono RCA signal it would be safe to run as stereo, but if not, bridge it, otherwise you may have issues. You would get 200-300 watts at that impedance, which is less than 3 decibels shy of full 400-500 watt power. The amp will be running much cooler, so it should even sound better.

square root(200 watts * 8 ohms) = 40 volts
square root(400 watts * 4 ohms) = 40 volts

So you see the gains would be at the same position here for both 4 and 8 ohms. Only issue is that the amp doesn't keep producing more power as you drop the load below 4 ohms. If you stayed at 40 volts at 2 ohms, the amp would try to produce 800 watts, which will definitely cause your lights to dim as the amp clips. The formula works both ways:

40 volts ^ 2
-------------- = 800 watts
2 ohms

Assuming you gain matched your linedriver it to the same voltage, you will still have the same issue. A linedriver is used to increase your RCA voltage, which reduces background hiss.

So you can try lowering your gains first sqrt(400*2) = 28 volts

If that doesn't work, try 8 ohms and 40 volts.

Kaptain · Post by **Kaptain** » Mon Jan 26, 2009 12:42 pm

Ok I don't know if I am doing this wrong or not so correct me please.

On my head unit I don't know where 80% is, i never turn it up to that level so I ran the 60Hz sine and turned up the volume to 30 which gave me 2 volts at the rca's with everything flat. From there I hooked the amp back up and adjusted the gain to 40VAC. Then continued to hook the sub back up in an 8 ohm load. 40VAC=sqrt(200 watts * 8 ohms)
Oh and the LPL was up all the way and bass gain was down all the way.

With this setup everything works good, no dimming. However I never mentioned that 98% of the time I listen to heavy metal and I like punchy bass. Well with this configuration it's not there. If I play something like Black Eye Peas, or my wifes music Pink it sounds great.

Should I turn up the bass gain on the amp to get it the way I want or leave it alone? The manual says to use it sparingly. I noticed that the 40VAC goes up when I turn it up the bass gain and from what I have learned this is what we are trying to avoid.

Suggestions?

Post by **stipud** » Mon Jan 26, 2009 12:57 pm

I suggest you put your LPL somewhere you can accurately replicate on your knob... e.g. 50%... mark it with a line if you have to... then set your gains there. That way you can increase the gains a bit more on quieter songs. Only catch is you have to turn it back down on louder music, or you risk clipping the amp.

Kaptain · Post by **Kaptain** » Mon Jan 26, 2009 1:05 pm

stipud wrote:I suggest you put your LPL somewhere you can accurately replicate on your knob... e.g. 50%... mark it with a line if you have to... then set your gains there. That way you can increase the gains a bit more on quieter songs. Only catch is you have to turn it back down on louder music, or you risk clipping the amp.

That's how I usually did it in the past.
I will try that.