BRZ Stock Head Unit + Aftermarket Amp + 3-way Components question

[daforce007]

Has anyone installed 3-way components (powered by an aftermarket amplifier); while retaining the original head unit? If so, I want to know how you installed everything! My understanding of the system is as follows:

• The head unit lacks RCA outs.
• The head unit powers the mids and tweeters.
• The stock amp in the trunk powers the door speakers.

The plan is to:

• Install the aftermarket amp in the trunk, opposite of the stock amp.
• Replace the stock amp with a line output converter (bit-ten or lc7i)

How I *currently* plan to wire this up:

• Splice the existing mid & tweeter's speaker wire, to run it to the line output converter (LOC) in the trunk.
  • This signal should be the full-range, correct? so I could just ignore the wiring from the stock amp?
• Run RCAs from the LOC to the Amp, and run speaker wire back to the components up.

I was wondering:

• If someone has devised a more efficient installation?
• Where have folks installed passive crossovers?
  • Is there space around the dash?
  • Should I install them in the trunk and run all the wiring back to the front?

Any and all help would be appreciated!

[illmatic]

Didn't really read the details of your post, but this build uses the OEM fujitsu ten head unit.
http://forums.nasioc.com/forums/show...php?p=36481713

[2forme]

It's really difficult. The factory head unit has the crossover built into it. It powers the dash speakers directly while offloading the door speakers to the amp in the trunk. You're better off just getting an aftermarket head unit if you're dead set on using an amp with a 3 way setup.

On my install, I removed the stock amp, and put the crossovers there while putting the 5 channel amp opposite of th(both under the trunk "floor").

[ngabdala]

You want to add something like JL Cleansweep into the setup.

[michaelahess]

Actually it's very easy. This car is a piece of cake and the Nav unit works fine as there are NO crossovers built into it. See my link below for a partial build thread. Also got one on diymobileaudio.com

[daforce007]

Thanks for the input y'all. The spec sheet of the Audison Bit Ten states:

"Automatic de-equalization of signal fed into the high-level inputs (with supplied Test CD) if necessary. It can also be performed without the PC."

Knowing this, one could feed the door speaker's source (that is already being run to the stock amp) to the Bit Ten, and have it de-equalized to a full-range signal, correct? Or would I need to use the amplified signal from the stock amp?

[2forme]

Originally Posted by michaelahess

Actually it's very easy. This car is a piece of cake and the Nav unit works fine as there are NO crossovers built into it. See my link below for a partial build thread. Also got one on diymobileaudio.com

My experience was completely different. Are you sure you're talking about a BRZ? What is the model of your stock head unit?

[sure74]

Has anyone tested the stock amp inputs to see if they are full range? The head unit output only
has provisions for LF, RF, LR, RR. That leads me to believe that the inputs for the stock amp
are just split from the LF and RF with no processing (full range).

[michaelahess]

Originally Posted by 2forme

My experience was completely different. Are you sure you're talking about a BRZ? What is the model of your stock head unit?

Yup, limited. It's the Fuji 10 thing. Full range outputs out of the HU back at the amp for front channels. The rear speakers run off the HU and I don't use those, or the rear speakers.

Running a test tone through my amp directly and looking at my RTA then running through the HU, almost identical, for all intents and purposes.

I keep volume between 30-45, set gains so it covers the volumes I want. The unit may modify the curve at lower volumes, but I didn't check that.

Make sure your EQ is flat...

[michaelahess]

Originally Posted by sure74

Has anyone tested the stock amp inputs to see if they are full range? The head unit output only
has provisions for LF, RF, LR, RR. That leads me to believe that the inputs for the stock amp
are just split from the LF and RF with no processing (full range).

Input to the amps is full range. Rear is run of the HU.

[sure74]

Originally Posted by michaelahess

Input to the amps is full range. Rear is run of the HU.

So you can place the LOC where the stock amp is. Grab the front channel inputs from the stock
amp inputs and grab the rear channel inputs from the rear speaker locations. This will minimize
the wire needed to light up the LOC.

[michaelahess]

Originally Posted by sure74

So you can place the LOC where the stock amp is. Grab the front channel inputs from the stock
amp inputs and grab the rear channel inputs from the rear speaker locations. This will minimize
the wire needed to light up the LOC.

That's where I put my LOC, then I got a DSP, but it's still pulling from there.

My build thread links off the link below has some pics of it.

[JoeBoxer]

Can you tell what frequency response the stock speakers are seeing from the amp?

[vignesh]

Just to be clear, The front door speakers are powered by the stock amplifier right. The rest of the speakers in the car, the two speakers and tweeters on the dash and the rear speakers are all being powered by the head unit?. Right now i am running jbl p66s speakers in the doors and infinity reference speakers on the dash. The jbl's are 2ohms and have 55 watt rms. Does the stock amplifier have enough juice to power the jbl speakers?

I am thinking of getting the alpine power pack to boost the head unit's power output. the alpine power pack is good in that it can be tucked away behind the head unit, a much cleaner install.