Thanks to geeman, we spent today measuring exactly what goes on in the 2003.5 sedan's Bose system.

Couple of points (see pics on http://kward1.homestead.com/G35pics.html but 56k, forget it):

1)The door speakers in this car are NOT 2 ohm! They are 4 ohm and as such can be replaced with new aftermarket speakers IF you want them to play severely eq'd sound. (See pics)

2) The system doesn't measure as having sub-bass. Has a peak at 50 and drops hard below that. Also rolls off at about a 6dB/octave slope from 50 Hz all the way to 20K. Not flat at all - tilts.

The front door speakers start rolling off at about 65 Hz, with a bump from 65 to 100 Hz. They have a wide happy-face trough from about 120 Hz to about 10k, with a narrow spike EQ'd in at about 800.

3) The rear speakers are rolled off at about 120 Hz. They also have a wide trough and narrow spike, and the highs roll off too above 10k.

4) The sub seems to play 80 Hz and down, with like a 25-30 Hz highpass subsonic filter.

5) The HU output is flat (minus negligible auto-loudness at the bottom end of the volume range) and decent in output voltage. At full output no clipping of a 1kHz sine wave was observed.

SO bottom line is that the output of the Bose amp is a roller-coaster, sonically speaking, but the preouts are good quality.

As far as LOCs go, I'd try an amp with balanced inputs (DLS, xtant, JL) and not even USE a GLI. I'd expect amps that can't take balanced in (Diamond, for one) to be noisy as heck.

 

i just recently replaced my door speakers with Polk Audio db6500 components, and have a pair of JL Audio 10w3v2's running off a JL 500/1 in my trunk.

can i take the differential balanced output from the stock HU and connect that DIRECTLY to a JL 300/4 amp? i'm assuming you would just splice the line running from the HU to the Bose amp with RCA connectors and then go right to the amp?

 

That is what I have done Per el_duderino advice. My biggest difficult so far with setting up such a system (I am using a JL 500/5) is when I went to splice the speaker wires into RCAs. The RCA outer shielding that it uses for signal transmission was easy enough to connect a speaker wire to. The insulated inner wire that connects to the inner "pin" of the RCA plug was insanely small, and was virtually impossible to connect to any sort of speaker wire unless I soldered it - which I did, but I didn't feel confident in the connection. So I went over to Tweeter to see if they had some of those pre-made speaker-to-rca wires from JL, and the Tweeter people acted like I was a moron and sold me two generic line level converters. I was too tired to fight with them, and no one in the area seemed to have RCA wire that had a more substantial inner conductor, so I bought these. I'll fool with taking them out of the equation later.

 

I would do so in a heartbeat.

In fact, I kind of have. In the 2004 Acura TSX, the output is lower in amplitude, and I've connected a JL 300/4 directly with no problems, except that if I raised the gain very far I had noise. With more drive that should not be an issue.

 

The IXOS 500 series RCA "Y" work well. At a lower price, the DIrected Audio Silver Series have good size conductors for both sides.

This is where the twisted pair RCA's come in handy, because they have to use bigger conductors.

I use "Y" adapters to get what I want...

 

The output on 1/2 of the balanced signal was 1 V RMS and about 4V peak-to-peak (if you look close you can see this on the scope screen with the sine wave on it).

A true balanced signal is twice that - it uses two signals of that amplitude that are summed together within the Bose amp for noise-cancellation purposes.

But with balanced-"compatible" inputs, 1/2 the signal is just discarded and unused. So an aftermarket amp with balanced-compatible inputs should work fine.

I will bet $100 that the 05 HUs are identical in OP to the 03.5 HUs. And if you want to drive up and visit, I'll measure it for you. In fact, come on up and we'll do your install : )

 

Wow, super technical-dudes: what can the regular, no scientific-talk folks do to improve the sound in the Bose system? Can I just get replacement speakers at Circuit City and slap them into the doors (and tweeters for that corner in the door) and expect much better sound?

 

No.

How's that for technical? : )

What's your biggest beef with it? Bass, mids, highs, what?

(BTW, do you really want the trunk monkeys at Circuit City working on your car?)

 

When I turn up the volume, like at 20 or so, the sound gets distorted. It sounds almost as if the speakers are blown.

And no, I said I'd slap in those speakers. Circuit City monkeys are not allowed to touch my car...

 

Ok, so the problem is bad sound at 20 and up on the volume control.

Where's the bass setting on the radio when this happens?

Basically, my suspicion is that you're running out of power, and also asking the system to play more bass with your bass setting, and as a result the system's running out of power faster.

So if you put in better speakers, odds are they will be less efficient than the Bose speakers (almost ALL good quality speakers made of good materials are less efficient than the flimsy, lightweight Bose speakers). Then they won't be as loud. Then you'll turn it up farther, and run out of power faster, and have the same problem.

So in my considered and professional opinion, you need both a new 4-channel amp and a new set of speakers for your problem to be solved. You may not need a subwoofer, but you do need an amp.

But why not go somewhere that has good gear?

 

What are your bass settings? It should sound fine at 20. I run mine there all the time. I have treble at +3 and bass at 0. It is not distorted. I listen to some fairly bass heavy music but not a lot of hip-hop bass stuff.

 

Bass set to +3 and Treble +5

From everyone I hear, I guess changing speakers will do nothing to improve the overall performance, that I really need to change out the amp at the same time.

I'm just afraid that if I do that, if something happens - like the infamous CD changer skipping - Infiniti won't warranty the HU because I changed out to aftermarket parts.

 

Someone wanna sell & mail me some of these? No one sells these locally. I'd love to kill these two bulky LOC that require grounds...

 

Thanks for the measurements. I assume these were taken with bass/treble at 0/0? With the settings at +1 or +2, I'm sure you'd see some very poor spectrums. The EQ curve does look consistent with what I hear from music. Overboosted bass that does not extend very low, muddled mid-range, weak but tinny treble.