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Head Unit - 2 Amps - Sub - Wiring Help needed

post #1 of 27
4/30/12 at 6:54am
Thread Starter 
Hi guys. Recently upgraded some car audio for my Z-28, and I need to get under there and rewire a bunch of stuff, so I want to install this properly with shrink wrap, etc. I have little knowledge of car audio beyond basic sppeakers and amps and never installed a sub before.
List of gear:

Head Unit:
SOny Xplod CDX-GT550UI [User Manual] [Wiring/Install Manual]

Amplifiers:
Rockford Fosgate P8004 - 4 Ch [Manual]
Legacy LA220 - 2-ch bridgeable (2X75 or 1X150 W RMS)

Speakers:
Sony Xplod 6X9 (2) -Rear
Kenwood 4" (2) -Front

Sub: Alpine Type-S 12" [Specs]

My first guess is to use the Legacy in bridged mode to power the Sub, and the RF to power both front and rear speakers but how to I wire everything? The rear of the head unit has no 'dedicated' sub out, but rather a Rear/Sub Out, so I think you have to tell it in the setup, which mode to be in. (??).

So do I use the high level output from the head unit, and split them (one pair to sub amp, and one pair to speaker amp) or a combination of high & low level (RCA outputs), or what? Thanks for any help.
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post #2 of 27
4/30/12 at 8:32am
You have an enormous amount of power on tap. Especially for the front speakers you have. Here is what I would do.


Do not change the head unit's 2nd rca outs to sub. Leave them full range.

run the two sets of RCA's from the head unit to the Rockford fosgate.

Power the front speakers off the pair of front outputs. Set the high pass crossover between 100 and 200. Err on the side of caution and start at 200 hertz. turn the gain all the way down.

the rear channels you bridge to your subwoofer. set low pass crossover at 80 hertz.

the RCA pass through on the rockford amp should feed the legacy amplifier. Run it stereo to the 6X9's. IF the legacy has crossover functionality, turn on the highpass and set it to 80 hertz or up.

Adjust gains and crossover points to get best sound in your vehicle

This set up should yield ~100 watts to each front speaker
~75 watts to each rear speaker

~400 watts to the sub

Obviously, by keeping the gains on minimum with the front speakers you are reducing the chance of the front speakers ever getting max power and blowing them. This is a good thing. I would hate to se you blow the front drivers.

Hope this helps
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post #3 of 27
4/30/12 at 9:19am
Thread Starter 
I added the other picture of the Legacy with the XO knob. I believe it is only a LOW pass filter though.

Quote:
Originally Posted by cubdenno View Post

Do not change the head unit's 2nd rca outs to sub. Leave them full range.

Ok. No problem there.

Quote:


run the two sets of RCA's from the head unit to the Rockford fosgate.

Yup, front & rear. Still following.

Quote:


Power the front speakers off the pair of front outputs. Set the high pass crossover between 100 and 200. Err on the side of caution and start at 200 hertz. turn the gain all the way down.

Yep. Only allow higher freqs to the small fronts. so far so good.

Quote:


the rear channels you bridge to your subwoofer. set low pass crossover at 80 hertz.

This is where ya lost me...

Quote:


the RCA pass through on the rockford amp should feed the legacy amplifier. Run it stereo to the 6X9's. IF the legacy has crossover functionality, turn on the highpass and set it to 80 hertz or up.

XO of Legacy is "on/off" and I believe it is low-pass only. This is why I was thinking of using the RF for the front & rears because of the HP filter for both, and the Legacy for the sub.

So what about running all speakers off the RF amp (2 X RCA from HU), and using the pass thru from the RF amp to the Legacy for the Sub via RCA as well?
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post #4 of 27
4/30/12 at 10:08am
That will work as well.

I just looked up the legacy amp. And as you said, only low pass. So yep, run the 4 speakers inside the cabin off the fosgate and power the sub with the Legacy. I see the legacy is rated at 300 bridged. Just make sure the final DCR of the sub is not lower than 4 ohm. Otherwise you run the risk of smoking the amp.

Should work fine. Nice the fosgate hass the RCA pas through. You don't have sub level control but if you set it all up correctly, it will not be necessary.

What year Z28?
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post #5 of 27
4/30/12 at 10:30am
Thread Starter 
Quote:
Originally Posted by cubdenno View Post

That will work as well.

I just looked up the legacy amp. And as you said, only low pass. So yep, run the 4 speakers inside the cabin off the fosgate and power the sub with the Legacy. I see the legacy is rated at 300 bridged. Just make sure the final DCR of the sub is not lower than 4 ohm. Otherwise you run the risk of smoking the amp.

Should work fine. Nice the fosgate hass the RCA pas through. You don't have sub level control but if you set it all up correctly, it will not be necessary.

What year Z28?

Thanks. Not sure how to check the "final DCR of the sub is not lower than 4 ohm" though. According to the specs, it is 4 ohm impedance....

Sub level control is possible in the Sony head unit, but obviously not in this wiring configuration.

It's an '81 Z28. Pic:
LL
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post #6 of 27
4/30/12 at 10:35am
DCR

direct coil resistance.

Not sure if your sub was a single/dual/quad coil variety and what the coils rated resistance was. If it is a single 4 ohm coil you are fine.

Nice car. Did a couple of systems in them in my youth!
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post #7 of 27
4/30/12 at 10:40am
Thread Starter 
Thanks man. Hoping new components and rewiring will reduce the dreaded engine noise as well.

Sub specs are:
12" subwoofer with dual 4-ohm voice coils
Impedance 4 ohms
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post #8 of 27
4/30/12 at 11:43am
Quote:
Originally Posted by caper_1 View Post

Thanks man. Hoping new components and rewiring will reduce the dreaded engine noise as well.

Sub specs are:
12" subwoofer with dual 4-ohm voice coils
Impedance 4 ohms

You sir are going to have issues. Either you wire that sub stereo for 75 watts per coil

or parallel for a 2 ohm DCR and you smoke the amp in all likelyhood

or wire series for an 8 ohm DCR and 150 watts to the sub
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post #9 of 27
4/30/12 at 12:26pm
Thread Starter 
Hmmm, not sure how to do any of those. Here is a manual on the Alpine sub. The sub is the SWS-1243D, which would be the top 2 'examples' in the PDF [HERE]
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post #10 of 27
4/30/12 at 12:41pm
Thread Starter 
From the manual:

Quote:


Mono Amp System:
Lhe LA220 amp is bridgeable from a 2 ch amp to a one ch amp. The ideal speaker impedance for optimum operation is 4 ohms. The amp will provide stable operation when operated between 2 and 8 ohms loads. The min recommended speaker load is 2 ohms for each channel in normal operation.
When operating in the bridged mode the min recommended speaker load is 4 ohms for each bridged channel. Operation of the amp below this imp. load can damage both the amp and the speaker

What exactly does that mean in comparison to the driver specs?
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post #11 of 27
4/30/12 at 9:56pm
Just got in from a business dinner. And by business it was a bunch of co-workers drinking beer at BWW. I have class tomorrow for work. If I answer it will most likely be Wednesday.

Lhe LA220 amp is bridgeable from a 2 ch amp to a one ch amp. The ideal speaker impedance for optimum operation is 4 ohms.

The amp will provide stable operation when operated between 2 and 8 ohms loads. This is stereo operation. Or left AND right channels


The min recommended speaker load is 2 ohms for each channel in normal operation.

When operating in the bridged mode the min recommended speaker load is 4 ohms for each bridged channel. This is bridged mono. DO NOT GO UNDER 4 OHMS DCR!!!

Operation of the amp below this imp. load can damage both the amp and the speaker


So what that means is that you can wire that sub 3 ways.

Stereo: You wire each coil to a seperate channel of the amp. Yields 75 watts to each coil. Amp "sees" a 4 ohm load on each channel

Parallel: you bridge amp and wire each coil to the appropriate terminal. Positive (+) to positive and negative (-) to negative. Yields a 2 ohm load. This will smoke your amp. [Example two in alpine manual]

Series: Amp is bridged again . take the negative from coil one and run a single speaker wire to the positive of coil two. Then amp positive connects to coil one positive and amp negative connects to coil two negative. Yields an 8 ohm load sub "sees" 150 watts or about the same as stereo. [Example one in manual]
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post #12 of 27
5/1/12 at 4:34am
Thread Starter 
OK thanks dude. No rush. So in the end, it is still "do-able" with the eqipment that I already have... that's what I was hoping for. I will have to pull the sub form the box, because I think there are only 2 leads coming out of it, and god only knows what theprevious owner has rigged up in there...
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post #13 of 27
5/3/12 at 5:36am
Thread Starter 
ok, I pulled the sub to see what they had going on previous to me. Here are the photos. Is this the right way, considering the amp I will be using (the LA220)?:
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post #14 of 27
5/3/12 at 7:02am
Quote:
Originally Posted by caper_1 View Post

ok, I pulled the sub to see what they had going on previous to me. Here are the photos. Is this the right way, considering the amp I will be using (the LA220)?:

No. That looks like parallel wiring.
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post #15 of 27
5/3/12 at 7:39am
The inside black and red posts shouls be connected together.

outside black to amp negative

Outside red to amp positive

inside black to inside red.

Should yield 8 ohm load.
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post #16 of 27
5/3/12 at 7:58am
Thread Starter 
so like this then? But why wouldn't I wire to the amp as bridged (+, +) ? see attachment in first post LA220.jpg :

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post #17 of 27
5/3/12 at 1:24pm
Quote:
Originally Posted by caper_1 View Post

so like this then? But why wouldn't I wire to the amp as bridged (+, +) ? see attachment in first post LA220.jpg :

For the pic of the sub, yes that is correct.

For pic of amplifier,

Look at the terminals shown. next to the word bridged is a "+" and a "-"

That is for bridged mono operation. Wiring the sub in the way you have shown (coils in series) will provide your amp an 8 ohm load which is safe for that particular amplifier.
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post #18 of 27
5/3/12 at 1:55pm
Thread Starter 
Yeah, I saw that after I posted; either way, it is the OUTSIDE terminals on the amp for bridged. So I should be good to go now, and can order up the necessary cables and wires to make all the runs. I thank you, sir, for all your time and help!! I didn't realize there were 4 subwoofer terminals for dual VC drivers I am glad I posted here to make sure everything I was going to do was ok !!!
So in summary, front(HU) to front (RF amp) and rear(HU) to rear(RF amp). Then pass through of RF-amp to the LA220 amp. Then as above, the sub leads to the outside terminals of the LA amp (bridged mode) and the sub jumper as pictured (one jumper on 2 middle terminals). Set high pass only on the RF amp as required for speaker size (front/rear) and low pass ~80-100 on the sub amp...
A few more questions on cables:
Where can I get cheap high voltage wire? Monoprice has good RCA and speaker wire prices, but no high voltage cabling.
Also, I am guessing I should run a 2 or 4 gauge line from the batt (+) to the inside of the car and use a 1:4 distribution block to power the HU and 2 amps. I will have an in-line fuse near the battery. I googled for images of 2 gauge wire (for car audio), and I am a little confused, because I think I bought a negative battery terminal that was like 2 gauge and it is huge!!
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post #19 of 27
5/7/12 at 8:50am
Quote:
Originally Posted by caper_1 View Post

Yeah, I saw that after I posted; either way, it is the OUTSIDE terminals on the amp for bridged. So I should be good to go now, and can order up the necessary cables and wires to make all the runs. I thank you, sir, for all your time and help!! I didn't realize there were 4 subwoofer terminals for dual VC drivers I am glad I posted here to make sure everything I was going to do was ok !!!
So in summary, front(HU) to front (RF amp) and rear(HU) to rear(RF amp). Then pass through of RF-amp to the LA220 amp. Then as above, the sub leads to the outside terminals of the LA amp (bridged mode) and the sub jumper as pictured (one jumper on 2 middle terminals). Set high pass only on the RF amp as required for speaker size (front/rear) and low pass ~80-100 on the sub amp...
A few more questions on cables:
Where can I get cheap high voltage wire? Monoprice has good RCA and speaker wire prices, but no high voltage cabling.
Also, I am guessing I should run a 2 or 4 gauge line from the batt (+) to the inside of the car and use a 1:4 distribution block to power the HU and 2 amps. I will have an in-line fuse near the battery. I googled for images of 2 gauge wire (for car audio), and I am a little confused, because I think I bought a negative battery terminal that was like 2 gauge and it is huge!!

Your summary looks correct.

As for power wire, I have used most of the major brands in various installs.

Kicker: Best flexibility I have found .Expensive though

Stinger: Prolly same cable as the kicker. The kicker still felt better to me though.

KnuKonceptz: Best performance/price for a now mainstream brand. Good internet sales/shipping experience

Darvex.com. Great place to order from

Sonicelectronix.com: great ordering experience

Millionbuy.com: great experience.

I have used at least 7 of these wiring kits in various installs

http://millionbuy.com/scoe3200.html

It's not 1 gauge but prolly 2. Flexibility is acceptable. Comes literally with everything except a ground distro block (this is not needed. I just like to do it) and the price is good. Just an option.
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post #20 of 27
5/7/12 at 11:09am
Thread Starter 
thanks for all that. I will look into shipments to Canada. Most likely buy locally however. Will start the wiring this week. What amperage should I use for an inline fuse on the distro block? I have a 30 already. Can buy another.

EDIT: This is my guess: RF amp = 400W; LA 150W (RMS) which is 550 rms (550/10 = 55). I am guessing I will go with a 60 amp fuse to allow for any peaks higher than the rms values to prevent inadvertent fuse blows.
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post #21 of 27
5/17/12 at 4:58am
Thread Starter 
Speaker polarity?? I was re-wiring everything last night, and noticed that the terminals on the speakers don't have +/- on them. How do I connect the speaker wire from the amps properly ??
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post #22 of 27
5/17/12 at 7:01am
Quote:
Originally Posted by caper_1 View Post

Speaker polarity?? I was re-wiring everything last night, and noticed that the terminals on the speakers don't have +/- on them. How do I connect the speaker wire from the amps properly ??

U use a triple A battery.

Touch positive battery end to one of the terminals and negative battery end to other terminal. If speaker moves out (away from magnet) you know which is positive. If cone moves in, you have polarity reversed.

Like anything, be careful. prolly not going to damage a woofer. But Ierr on the side of caution with smaller speakers and just pop them to see movement.
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post #23 of 27
5/17/12 at 6:13pm
Thread Starter 
I didn't do the battery trick, but someone else told me the positive post is on the left most of the time, if they are side by side. (which they are). I guess I could do the battery test just to be sure. I did however finally get all the connections made and did a dry run today... WOW!!! is all I have to say. relieving the 6X9's of bass duty really improved the sound, and with the added 12" sub, kick drum and bass notes... weeeeeeeee ! Tight fit for the RF amp though, holy crap it is big once you try to put it somewhere!!! Same for the sub box, was BARELY able to squeeze it on the trunk. I have the woofer facing upward, basically in between the 2 6X9's. Not much clearance there, so I am not sure if that takes away from the performance much. I used a ratcheting tie-down to keep it in place
By the way, I went with a KnuKoncepts order. Got 4 gauge main power line to a 1-4 distro block, 8 gauge power lines off that. a 60 amp fuse near battery. ring terminals (which didn't have hole large enough to fit a battery post...had to drill it out). 5 meter RCA cable with REM lead for rear sub. Some speaker wire. Great experience from them. That is one HUGE power wire though, and I was VERY surprise at how flexible it is!! It is like a limp noodle. Very impressed with this installation gear.
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post #24 of 27
5/18/12 at 6:55am
Awesome!!!!!

Noise issues? I remember that you had some.
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post #25 of 27
5/18/12 at 8:47am
Thread Starter 
haven't started it yet. Just put the oil in after I posted the photos. Going to do that this afternoon and take it for the first drive of the year Thanks again for ALL your help. It sounds amazing...
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post #26 of 27
5/18/12 at 1:37pm
Thread Starter 
great news. No ground loop noise (alternator whine) !! Musta been the deck that was shot. I know the FM tuner on it was also broke. 12 yrs old, finally packed it in. Now I just have to fine tune everything (crossovers, levels, fade, eq, etc etc)...
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post #27 of 27
6/23/12 at 4:20pm
Thread Starter 
The position in the trunk as depicted was bad for bass. I don't think there was enough space for the driver and port to breathe. I turned it 90 degrees and pulled it back toward the rear and it made a huge difference in bass output in the driver's seat..
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