I was reading through some of the posts in this SQ forum, and i noticed that on (some) headunits you can use the 3 sets of rcas all for the front, with the front channel used for tweeters, rear channel used for mid range, and sub/non-fade for mid bass...

What i'm wondering is with a setup like that... how do you control the rear channel? where is it connected to? and same with the sub?

I'm a total SQ n00bie so play nice please

The only heads that can do active front plus subs have 4 preouts, not 3. Im 99% sure the posts you are referring to are active 2-way's plus sub. So highs, mids and lows. There are heaps of decks out there now that can do this. Either that or highs, mids, midbass then daisy-chain to a sub.

The only way you can do active 4-way with 3 preouts is by using the deck in combo with the source. Highs/mids out of one then split to two amps and use onboard Xovers, the midbass and sub. Or you can get outboard processors. The Alpine H701 will allow active 3-way plus sub, and if you know what you are doing, you can get rears of it as well. Otherwise, the Alpine F#1 processors (old and new) will do a full 3-way active front, sub and rears whilst shining yours shoes too!!

And most people on here dont have rears. Those that do tend to run them off the decks onboard amp (eg, the crapp 50x4 guff). Those that run rears off amps require external processors.

alpine has bass engine pro.

it allows you to do a 3way setup

front tweeters + mids + midbass or sub

if you wanted a 4 way setup with front tweeters, mids, midbass and then sub you would have to use the midbass output y split it between the midbass and subs and use the internal x-overs in the amps.

for a 3 way plus rear you would have to do something tricky to make it work or use a outboard processor like a alpine h701 (4 front (mids, tweeters x L+R), 2 rear (L+R), 2 subs or sub + centre channel).

Options.



Alpine 9855,9853,9965,9833,9835,9815

all offer 2 way front active + midbass or Sub..

No rear operation (unless it's not active)



Eclipse CD7000, 8455,8454,8053

same again (slightly better at this than the alpine, better x/over function and ALOT better PEQ. Similar time alignment operation, better SQ than all the Alpines Except the 9965E which has better PEQ And Similar X/over functions.)



Processors.


Alpine PXA-H701 ($899, must have either RUX-C701, or processor control head unit)


2 Way front Active

Rear output (single out)

Subwoofer

Center (or Stereo subwoofer out)



The Rear channel can be bandpassed,

so you can run

3 way front active

+ Sub + centre or Stereo Subs



Eclipse DCU-105 ($899 + AVX5000 $999 or AVN7000 N/A in Australia)



3 way front Active,

Rear output (single out but can be bandpassed.)

Subwoofer Out

Centre Speaker out or Stereo Subwoofer out.



Juls

One trick with a 3-way source is to use a 4-channel amplifier for the front speakers that also has a pass thru RCA output that sums the front and rear inputs, as this will then arive at a full range signal for a further amplifier for rear fill. Many pass thru RCAs are only derived from one pair of inputs however.

pioneers high units also have a feature for three way active front stage.
best way to get around using a sub is running your xovers outboard as suggested.