Pac lp7-2 on alpine sub wires adjustment.

[rotwiler]

Just installed 2 12s and 1000 watt rms amp. Used the LP7-2, worked perfect. Only thing I am confused about is the gain setting on the lp7-2. I read somewhere the Alpine sub wires put out around 8 volts max, my Amp has up to 8 volt input. Do I turn the lp7-2 all the way to right and then adjust my amp gains? Instructions were kind of confusing, said turn up and listen for distortion and back off a little with radio on 3/4. I never hear any distortion all the way up, so I put the lp7-2 1/2 way until I figure this out.

 

[rotwiler]

System sounds good, but I am for sure not getting all of the 1,000 watts, I don't want to turn anything up much until I can get gain correct and the LOC setting right. I did notice once you pass around 30 on the 8.4AN volume, the bass really doesn't increase much, probably a safety feature in oem amp for sub. So right now I just need to know how to figure how much to turn up the LP7-2, instructions for old school say turn up till you hear distortion then back off a little at 3/4 max volume, but even with the LOC all the way turned up, I hear no distortion. Once I can get this right, I can set gains using a volt meter.

 

[adrianp89]

I usually leave LOC gains as they come out of the box, then set my sub gain accordingly. If any issues then I will mess with the LOC gain.

 

[Spud2388]

Keep the gains on the loc low and try to set it with a ddm. If the amp gains aren’t too high and you can reach the required voltage with a test tone, then you’re good. If not, turn the gain on the loc up some and try again. I try not to raise the gains on anything higher than half way, so a combination of a little of both will be okay.

 

[Witch]

What type 0of voltage does the LOC put out ?

You could pitch it and grab an LC2i

it has a clip light built in, plus Accu Basb that helps eliminate roll off

 

[rotwiler]

Up to 8v should be achievable by manual. My amp also says 8v preamp Circuitry. I do like that audiocontrol LC2i, but the PAC lp7-2 seems to work very well, just need settings correct. Over the years I never really used loc's, so this is pretty new to me, always went aftermarket hu. If I connect a meter to the rca outs of the loc, do I just set meter to volts and try to get close to 8 at 3/4 volume ?

 

[Witch]

8 volts is a **** ton of voltage

you will hardly have to turn your gain up at all

An AmpPro only puts out 5v and the DSR1 only 4v and those you just have to crack the gains on the amp

If you have a shop local to you that has an SMD dd1 or an O scope should be able to set them up perfect if you don't want to leave anything on the table


Edit:

Just read you want to trey to match the input voltage of the amp, you could call the amp manufacture and get that voltage if not in the paperwork that came with it

https://www.carid.com/images/pac/amplifiers/pdf/lp72-installation-instructions.pdf

 

[ChrisM101]

Ok un hook RCA cables from LP7 to amp, Turn up a bassy track to 3/4 volume, set lp7 gain to minimum. test each RCA output with a voltmeter, if you want 8 volts adjust it to that.

These factory radios are really clean in their output as i think they back off after about 29 as you seem to have noticed.

Now as far as the amps go. A true 1000W amp with proper wire gauge and a clean source will produce the power without turning the gain up high. Most old amps did fine with 2 volt input.

your amp in most cases has a clipping indicator. plug in your RCAs again and adjust the gain on a bass heavy track until you see the clipping indicated, back off until it no longer flashes. Thats it.

Also Id recommend setting the bass boost or anything like that to off on the amp, and also setting the bass level on the receiver to 0.

Low pass on the amp should be about 120hz and below. Most people tell you 80 and below, but I prefer 100-120 or below on a sealed box.

ETA: make sure your wiring for the sub is at the proper ohm load?
1000w amp probably only makes it a true 1000w at 1 or 2 ohms.
If its one and you accidentally wired it for 4 youre probably getting about 300 W

 

[rotwiler]

Using 2 dvc 2ohm subs and wired them to 2ohm final load, will turn up low pass, is down low now and test output volt at at the lp7-2 rca outputs, then I can move on once I get that done. Need to do the big 3 upgrade also, noticing headlights flicker some when volume is up some.

 

[rotwiler]

Well I went out and connected a volt meter, still couldn't get it set right. I put the rca connected to a multimeter and was only able to get 1.9volts with the lp7-2 turned up all the way, then I took rca out and connected to the other channel on the lp7-2 and couldn't get any # to show on volt meter. Removed and put back in other side, back to 1.9. Checked wires all was good, so I removed one rca at a time when music was playing and was still getting output from amp even with only 1 plugged in so there has to be output on both rca's, so not sure it won't register on one when not going into amp. The bass sounds good, just some odd things I can't explain with trying to setup the loc. I may just get a audiocontrol, this lp7-2 is pretty cheaply made.

 

[Witch]

LC2i is an epic LOC and reasonable and a clip light

 

[rotwiler]

Thanks, will buy one, I even removed back of the lp7-2(snaps on easy) even the chips looked odd, had missing coating on them, might have 1 bad chip. I didn't expect 1.9v maxed out, still odd its only showing volts on 1 channel. The wiring to the alpine sub has 4 wires, I connected the left 2 wires black to - and white to + on right set same thing to the loc. I looked online to make sure was right, but not much info. I know factory uses odd non standard colors sometimes.

 

[Witch]

You will really like the LC2i

It cleans and boosts your signal and has Accu Bass that helps alleviate bass roll off from the factory system

the clip light is just icing on the cake . . . .

 

[ChrisM101]

Thanks, will buy one, I even removed back of the lp7-2(snaps on easy) even the chips looked odd, had missing coating on them, might have 1 bad chip. I didn't expect 1.9v maxed out, still odd its only showing volts on 1 channel. The wiring to the alpine sub has 4 wires, I connected the left 2 wires black to - and white to + on right set same thing to the loc. I looked online to make sure was right, but not much info. I know factory uses odd non standard colors sometimes.

Wait , wait , wait... youre tapping wires for the sub from the factory alpine system?
You need to tap the rear door speakers, or before the factory amp.

No telling what signal processing is done on whats going to the Sub.

 

[TomT]

The signal going to the factory sub for the Alpine system is known to be less than full range. That’s because the crap factory sub just can’t handle it.

The cleanest (although expensive) way to get a quality signal is with the PAC AmpPro 4. It will give you an RCA sub out and eliminate the need for a LOC.

 

[tylerlewis_89]

Wait , wait , wait... youre tapping wires for the sub from the factory alpine system?
You need to tap the rear door speakers, or before the factory amp.

No telling what signal processing is done on whats going to the Sub.

I just discovered this issue with my install this morning sounds good at any thing below 20 soon as you turn it up sounds distorted and was popping. Will the back door speakers work? I’m currently going to the fronts as I understood they are a true full range?


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[adrianp89]

I just discovered this issue with my install this morning sounds good at any thing below 20 soon as you turn it up sounds distorted and was popping. Will the back door speakers work? I’m currently going to the fronts as I understood they are a true full range?


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Going to the sub is 100% perfectly fine. You do not gain anything by going to to front or rears, in fact you lose signal. This has already been proven based on RTA measurements.

Sounds like the speakers are clipping and you are pushing it past it's limit. What is your gain? Is your amp signal set for low or high?

 

[Witch]

If not getting an AmpPro or a DSR1 just grab the signal at the sub
With the LC2i you will hardly need any gain at all

 

[adrianp89]

I think some you guys own stock in The lc2i lol

 

[rotwiler]

Well I have the pac and honestly it is so so, yes I get bass, but volts coming out if it is low and can smell a faint burning plastic smell, so I went with the audio control and for like $30 difference, Excellent build quality(metal) and option to add in bass past the point the factory amp cuts bass, is worth it. I will install it tonight or in morning and update any change I notice. I probably have one of the cheapest upgraded factory systems you could do and actually sounds good. Around $600 total for box, 2 12s, 1,000 watt amp, rear door jbls, front dash jbls and misc things like butyl sound deadening and closed cell foam. $260 was for amp, subs and install kit. $130 for the dash and rear doors, some were open box discounted. $20 noico butyl, $7 closed cell foam, so $417, plus the fiberglass custom box and loc. So right at $600.