Nissan GT-R Forum banner
1 - 20 of 223 Posts

560 Posts
Hi guys, moving onto a slightly different develepment program now with the GTR's front door speakers after developing the plug 'n' play subwoofer kit which is still being made and shipped (Sold here)

What I'm trying to achieve here is a new set of component door speakers which fit into the stock locations, sound great and don't cost much $$$. I also want to make the kit as easy to install as I can and with the minimal amount of effort for you or an installer. This includes having the ability to remove the kit and returning back to standard for you to sell on or move over to your new car. I will try to reuse screw holes, existing wiring, connectors where I can or at least explain some options on how to revert back should you need to cut any cables etc.

Anyone can visit their audio shop and blow $2500 on a custom made 3-way front door setup with dedicated amp, Audison Bit One etc and at this stage, all that equipment may be needed, but I want to try the development of a kit which give you the best bang for your buck. Is spending over $800 on a Bit One going to improve the sound THAT much?

Anyway, I will be taking it one step at a time. I'll be just replacing the speakers and running the stock Bose amp for a start. I'll then move onto fitting a new amp to drive the speakers and then move onto any processing or cleaning of signal should it be required.

I have only just started this project so my first purchase was the excellent Hertz HSK 163 3-Way Component sets. What I didn't want to do was try to compromise a few bucks by getting cheap speakers. These are world renound for their excellent sound and build quality, especially their bass response from the 6.5" driver. Another benefit is the use of a 3" midrange where most other use 4". This means that just a new adapter mount will allow them to sit perfectly into the OEM Bose speaker position.

I started by creating some new adapter rings for the 6" Bass and 3" midrange. These were fabricated out of MDF for a snug fit into the factory locations.


Here are some comparison pictures of the new Hertz and the old OEM Bose.





Next this to investigate was the tweeters. I first of all removed the tweeter trim and tried to design a new trim which would use the factory mounting points which could be covered in leathter / alcantara etc to look smooth. It was just too difficult to do.....not only that, If I managed to pull it off, I would have to do a mirror image for the drivers door.....and I wouldn't want to do lots of them for kits :headshake:

Here is my attempt anyway....notice from the side, it bows like the original mount. It just didn't work least i tried.



After that debacle, I decided to try to get the tweeters to fit the existing plastic mounts with mininal fuss and so that you can always revert them back to standard with the standard tweeters in.

Success..........notice the tweeters have some silver banding which you can just about see behind the OEM trim


Here are the tweeter comparisons.


So that is pretty much all I got done at the weekend. other thing.....I've managed to fit the new Hertz grill onto the doors with minimal fuss for anyone who wants a subtle way of showing upgraded speakers.


Next job is the first wiring up. I'll be tackling this over the next day or so. I'm having to do this development work in my evenings and weekend so sorry if it doesn't go as quick as some would like.

I'll report back with my next findings :thumbsup:


261 Posts
Can't wait to see this finalized!

560 Posts
Well, not really got as much done today as I'd hope. I had two orders in last night for sub box kits so I've been busy assembling, spraying etc.

Each time i went to do something on the door kits, something cropped up. First I didn't have any spade connectors so went to get some locally. Then realised that the mids need 0.5mm spades and the bass need 0.8mm spades :headshake: Went and got some door seal to provide a nice seal to the speakers back and front to resist rattles.

I got some sound deadening sheet and installed that in the backs of the doors although i'll probably do some more on the inner skin when everything is mounted.

I did some wiring up. It seems that there are two inputs that come into the doors from the bose amp under the seat. There is a dedicated bass cable for the 6.5" and another input for the mids and tweeters. The bose tweeters acually have a built in crossover (you can see the capacitor mounted on the side). Seeing as this is the case, for the first test which is just a simple door speaker replacement, I'm going to wire it up as follows :-

Hi-Pass input from the bose amp (which origianlly supplied to the mids and tweeters) will be sent to the input of the crossover on the Hertz
Low-Pass input from the bose amp (which origiinally supplied the bass speakers) will be sent direct to the 6.5" Hertz woofer.

The Output of the crossover will give me a seperate tweeter and midrange output which i will take to the corresponding Hertz speakers. If i didn't do it this way, the tweeters will be getting mid range and for one thing, that wouldn't sound right and secondly, it could blow it :nono:

I've managed to wire up and install the bass speakers by intercepting the blue and white wires which went to the original woofer. I've wired in and mounted the tweeter but I have run out of time now. I've just come in and its 21:20 here so running out of light. I need to sit down....ive been at it since 8am.

I will continue in the morning as I'm off again.

Couple of picture of the mess and the front door mounted tweeters and bass speakers :thumbsup:

Oh....I did turn the stereo on and so had sound coming out of the new hertz so thats something I suppose :clap:



Inside the Hertz crossover if anyone is interested :-


560 Posts
Okay, today's update.

Finally finished a door. Did it without a single drill hole :) Had to cut a cable to use for the input to the crossover as i don't have time to look for a connector at the moment.

Okay, it seems that the rumours of the Bose amp being "different" are well founded. What I have done is wired up the passenger door by simply replacing speakers. I've driven the 6.5" driver with the original cable which went from the Bose amp the old 6.5" Bose driver. The Input to the uppers (mid and tweeter) I have taken into the input of the Hertz crossover and then the Mid and tweeter is run off that crossover with the selectable +2db switch set (giving it the best chance I could).

First impressions is that its quieter, especially the midrange. What I did then was downloaded a series of test sounds from the web. Different frequencies - 200hz, 400hz, 600hz, 1khz, 2kzh, 4khz and 8khz. I also put a white noise test tone on the CD and used it in the car. I measured the db's coming out of the left and right seperately with the same tone and same volume so i could see what it was doing. It was 3 or 4db down on most tones. It is clearly down on db compared to the bose speakers.

The most likely cause of this is the amp running at 2 or 1 ohm and so with 4 ohm speakers on it, its under loading the amp and the volume is reduced. Its VERY difficult to measure impedance of speakers without oscilloscopes etc but its pretty clear, the Bose kit isn't normal car audio spec.

I have nearly finished fitting the drivers door now so in the morning, I'll put it together and see how it sounds. It was an unfair test asking an amp to drive 4ohm speakers on the left and 1 ohm on the right. Might even upset it so I will wait until I have put the drivers door back together so I'm running a complete Hertz setup and see what happens when i crank it up.

So, its looking likely the seat is coming out and I will have to look at a replacement for the Bose amp to deliver 4 ohm's.

I will update again tomorrow.

Couple of pics with the finished door with and without its cover on :-


1 - 20 of 223 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.