Nismo audio upgrade- critique my planned setup

2fast4thelaw

I apologize if I came off a bit negative, anyway this forum is about sharing information and this is a bit lengthy so here goes.

The problem with stock passives is they are designed primarily for having the mid and tweet close to each other and on the same baffle or panel. This largely why they get a bad rap especially if you are forced to put components in unconventioal places. Basically a car is an unconventional envornment for audio. In order to resolve these problems we have to re-design our passive crossover network and taylor it for our envoirnment.

Phase and crossover slope are 2 separate entities and in this case slope remains unchanged.

Now adjusting the phase is a whole other science. Car speakers are optimized to perform well off-axis (speakers that play indirectly) vs home speakers that are optimized for on-axis (pointing directly at you). No matter how good off-axis speakers are, they will still sound better on-axis.

What I try to do is put the tweeter on axis by adjusting the phase anywhere between 90 and 270 degrees. In doing so this will change the time alignment between the mid woofer and the tweeter. You can calculate your resistor values that you will need to correct the change in time alignment. Let’s say you have a lot of carpet in your car, then you want your time alignment to be quite advanced because of the non-reflective materials in the car. If you are reflecting off of glass then you need to go the other direction because of the reflective material.

Applying this to the Z:

I chose to use the stock location for my mid’s and tweets. What I did was roll my tweets 270 degrees off-axis by changing the values in the resistors on the passive crossover. (I will explain why I did this later) Since they are reflecting off of glass I used the lower settings on the crossover volume to cut a little output from them to compensate for the db gain from the reflection from the windshield.

In the Z, the distance between the tweets and mid’s are about 18 inches but again the fact that they reflect from the windshield made the phase invert. I not only had to flip the phase 180 degrees to put them back into phase, but I added an additional 90 degrees to make the illusion that they were in front of my face. This was a total of 270 degrees of phase adjustment.
In order to get my values I had to reverse engineer the Focal passive crossovers.

These crossovers are 3rd order Butterworth 18/db octave crossovers so they were not that complicated. I just punched in the component values in my software and then my software program spits back the values after I have it calculate the phase I want.

I just had to order some 1% tolerance resistors and capacitors of equal quality and replaced the components.

This still changed some behavior of the tweeter and mid woofer relationship but remember I have a 13 band parametric eq which fixed this problem and I was able to blend them perfectly, at least to my ears.

My imaging is dead on and dramatically better than it was just rolling with the stock passives.

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