Nismo audio upgrade- critique my planned setup

Originally Posted by 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.
slope directly affects phase, for every 6db/oct adjustmnet phase changes 90 degrees
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.
using a 18db/oct filter will change the phase of the drivers 270 degrees this is normally fixed by making sure the woofer and tweet are hooked up with opposite phase. that doesnt put the tweet on axis. A tweeter would faced up at the windshield would most likely need a -6db/oct attenuation to sound closer to on axis. Time alignment is a measure of the distance the speaker is from the reference point( your head in the drivers seat) not a measure of the distance between the tweeter and woofer
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.
what you did above is create a Zobel network that is normally used to counteract the difference in inductance between drivers( basic level matching) normally the woofers in the door are about 60 degrees of axis, Im assuming you compensated for that as well.
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.

Originally Posted by speedfreak28

Originally Posted by 2fast4thelaw

I had to heavily paraphrase to keep it from being a book but I will touch on your notes.

What i first was trying to say is I did not change the slope of the crossovers. Also Phase and slope only directly affect each other in simple passive crossovers without phase compensation. Any decent passive crossover will have phase compensation. In my Focal crossovers they compensated for that shift so I had to alter them.

Also since I have my own software I calculate time alignment by distance between tweeter and mid woofer becasue its a more stable constant since once the drivers are installed they will never move.

A Zobel network is already designed into the Focal passive crossovers because the Focal tweeters are actually 8 ohm and the woofer is 4 ohm. I altered the values in an attempt to undue the phase compensation that was designed into the crossover which put me exactly where I wanted to be at 270 degrees off-axis.

I left the mid woofers as they were (off-axis) as I only needed to alter the tweeters in my installation. I did this to keep it less complicated becasue I knew I could use my eq to blend them.

I wasnt using the EQX to tame individual speakers but to tame the peaks at each octave. I also first tune the system by my ear as what sounds best to me. I then record my settings as my reference point. If and when I have my car RTA'd for competition I can record those settings as a competition reference point so I can go back in forth. Perfectly flat is not always ideal for all music for everyday listening at least for my tastes.

Remember, there are a hundred ways to skin a cat. What I did made a big improvement and greatly enhanced my imaging and overal tonality of the system. If I could have in hindsight I would have used the 3-way Focal poly kev set and had even more improvement. I wanted to keep the stock appearence and that would have been nearly impossible.