Interesting Findings about BRZ Audio Output
 

My goal is to build the ultimate sub $300 system. I'm not focused on "the best" rather on upgrading from stock to more of the sound I like and adding the least possible amount of weight.

To that end I'm keeping the factory head unit and looking for unprocessed output. Based on testing the three different outputs here's what I found:

Front Speaker Output: Unmodified - full range signal
Door Speaker Output: Bass boosted - full range signal
Rear Speaker Output: Unmodified - High passed signal

I tested by connecting to full range speakers and subwoofers, using music material that I am familiar with.

I plan on running only a 6.5" components set and a single 8"sub, so I will be feeding that signal from the front dash speaker output only

There already a sub output for the optional factory sub. This link provides the pinout http://www.ft86club.com/forums/showp...1&postcount=22

Watch out for rattling

Did you test the door speaker signal before or after the amp? I am unsure how it could be bass boosted before the amp, because as I understand it, its functionally the same signal. If the signal feeding the amplifier is in fact not bass boosted you do not have to use the head unit outputs to feed the sub, instead they can be tapped in the trunk.

This is a possible weight and ease of install saving for you.

+! Dyno mat is your friend :D

It's the amp
 

The signal going into the amp is not boosted. It's the same as the dash speaker signal.

That's what I was hoping as I tapped the lines feeding the amplifier (as well as the amplifier power for a line out). I haven't noticed it to be a bass boosted signal at all, and imagined the amp had to be the source of the bass boost.

I always thought/assumed that the amp was the source as well.

The amp is removed and I'm work straight from the wires feeding it.

Using the same exact speaker and the same music, I noticed much more bottom end on line that feeds into the amp than the one that goes into the dash speakers.

I also hooked them up directly to the sub. The dash line plays some bass, the rear speaker line plays almost no bass, and the amp in line plays a lot of bass.

I haven't completed the install yet, been busy listening to my new exhaust =)

If there's any other methodology I should try, let me know and I'll probably get to it this weekend

You may want to use some meter other than your ears. I am not sure how that line could have more bass. It doesn't make sense unless there is a hidden and unknown crossover.

Can you describe your exact test setup? I am currently unsure of your testing procedure. Are you using a line out convertor attached to each set of lines which is then feeding the same amplifier and speaker? Where exactly are you getting your feed for each line (aka the physical location of the wire, this is important for finding where the crossover is)?

The only thing I can think of would be that the base signal from the headend has increased bass, then the splitter has some sort of crossover in it blocking bass to factory speakers and a similar setup in line with the rear speakers. If that's not the case, then I don't know how this is actually possible...

Ok page 322 of the Brz Electrical wiring diagram shows that the signal to factory amp is wired in parallel with the front speakers. If you disconnect the factory amp and connect an after market amp to the door speakers, you will notice that the bass is clearer. I believe that the factory amp has a cheap non adjustable bass booster. The dash and rear speakers because if their size has a passive bass blocker or crossover soldered to the speakers themselves. I will post pictures later.
The factory amp harness is the same as the head unit. You can easily rearrange the pins to add an aftermarket amp without cutting the wires. If you want a subwoofer I would disconnect the factory amp and install a 3 channel amp for the door speakers and the subwoofer

Harness for amp
 

Here is the harness for the amp

What color wires go to the door speakers? purple/green or white/grey?

Does anyone think it will be ok to use an amp with a high level input and use the speaker wires coming from the head unit to feed the signal?

yes that would be fine to use the highlevel in as long as your amp supports it.

Quick question for you guys please..

Is the bottleneck in the BRZ factory audio system the speakers or the amp? Or both?

I've had good luck before (on other cars) either adding an amp to the stock speakers or swapping out the stock speakers using the same amp. I use to be an installer to pay off college bills so i'm familiar.. just hoping to hear feedback from you guys who may have already gone down this path.

Thanks much!