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Planning and Design Phase
The planning and
design phase of any project is the most important. It is through the
processes which accompany this phase that makes the difference in a
successful project and a not so successful one. In order for me
 to determine what my
new system would be, I first had to identify what the existing system
was not. Before I begin I want to say that in no way am I saying that
Bose does not make a good product, in many cases and to most individuals
the factory Bose system is very adequate, but in my case having had
numerous aftermarket system in previous cars, not to mention investing a
lot of time and money in a fairly high-end home system adequacy does not
cut it.
Bose Premium Sound
System
The factory system in
the 2003 Infiniti M45, like many factory system was designed by Bose
Corporation. Taking many of the principals that aftermarket engineers
follow in designing the system Bose was able to design a pretty descent
system. The system is comprised of the standard
AM/FM stereo tuner, a 6-disc CD Changer and a Cassette player. In the
2003 models the cassette is mounted low in the dash and a 6-disc changer
is in the glove box, in 2004 this configuration flipped to have the
cassette in the glove box and a single slot-6-disc changer in the dash
location.  The latter is much more preferable to me, since I do not even
own a cassette to play. My particular vehicle being a 2003 however has
this configuration and it is one I can live with for now, but future
upgrades may included a swap. Both model years offer Satellite radio
options, either XM Radio, or Sirrus. My "M" came equipped with XM.
Like many newer cars,
the audio system and climate controls are are integrated into a dash
mounted LCD screen. The driver can scroll through multiply menus to
control both interior temperature, vehicle mechanical options and switch
audio sources. This sort of integration does make for a super clean dash
layout, however it is not very conducive to high-end aftermarket audio.
Later as we get into the design portion of our project and identify our
project requirements this will become an issue.
Following the source
units, the signal passes through a series of BUS Cables to a proprietary
Amplifier/ Processor mounted in the trunk. This unit is what powers the
seven speaker Bose system. The seven speakers in the Infiniti are said
to be four full range speakers, a pair of separate tweeters and a single
10-inch  subwoofer.
With a pair of tweeters mount in the front corners of the dash and two
pair of "full range" speakers in each of the four doors and an anemic
subwoofer in the rear deck the system is far from full range. To test
the factory system, I pulled out my trusty Laptop computer with RTA
software and condenser microphone and took a few measurements of the
system frequency response using pink noise. (Pink
noise in acoustics is noise in which there
is equal power per
octave). Human beings general can hear frequencies between 20 and 20,000
Hz, with our ability to hear higher frequencies dimensions in most cases
as we get older. Even though most modern music only utilizes a portion
of that range, generally between 80-18,000 Hz, it has been a common
measure of high quality sound to have a system that can at least
reproduce sounds in the full 20-20k spectrum, with the ability to
produce notes both lower and higher as an option. Even though very few
if any people can hear sounds below 20 Hz, the lower frequencies below;
say about 30Hz are usually felt instead of heard, while higher
frequencies above the 20k threshold can be attributed to better detail,
or an airy more open sound to some. Our measurements of the
Infiniti/Bose system showed a respectable response curve of about
30-19,000 Hz at low volume, however we noticed that as volume increased
the bass, or lower frequency notes started to roll-off. At full volume,
an ear piercing 112dB's we measures a frequency response of only
60-18,000 Hz. Why the difference? Well as we will again discuss later,
it seems that Bose has installed a compensation network into the mix. A
compensation network can be placed in a system for many reason, the most
common and it is my theory in this case, that it is more to protect the
speakers at higher volumes from being blown, than anything else. Another
factor that we noticed was that there was a preset EQ curve designed
into the system, one that users couldn't adjust so regardless of whether
you wanted more bass, or less you were stuck with what the Bose
engineers built-in. So much for buyers choice.
After evaluating the
factory system, our goals for this project became very evident. In order
to get the best possible sound in the M, we would need to by-pass the
factory speakers, and loose the Bose processor. But tradition tells us
that in order to get the best sound possible, we would need to replace
the factory head unit, which after much deliberation was something that
for cosmetic reasons we did not want to do.
System Requirements
So what are we trying
to do? The first thing is obvious, get the best possible sound
for our money we can. The second, and to me more important was to
maintain the factory integrity of the "M". This would prove to be
the biggest challenge of the project and ultimately require some
compromising. Following the requirements for Cosmetic Integrity, we also
wanted to use quality components, in our case it just so happened
that we had a number of pieces from a previous system which could be
migrated to the new car. This would help in two areas, cost and easy of
installation, since the speakers we already had would drop in with very
little modifications. The last criteria was easy of use, or what
I call the "wife-factor". Lets face it, it is something that we all face
at some point in our lives. Whether it is the "girlfriend-factor" or
"wife-factor" this concept at some point will steer how a project
such as this will go. In my case, having had to address this "factor" in
the design of our home theater, it wasn't a big deal, to others it can
be more stressful, but regardless. There is something very useful in
this type of negotiation.
Guiding Principles:
-
Sound
Quality
-
OEM
Integrity
-
Quality/
Brand components
-
Easy of
Use
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Equipment Selection
In many designs this and the next phase of a system
build-up maybe flip-flopped. In my case since I already had a number of
the components it made it easy. The hardest part of the process was
figuring out how to get the signal from the head-unit to the speakers,
if we removed the Bose Amps,
 speakers
and processors. The original plan called for using what is called a Line
Output Converters. An LOC takes the high-level speaker outputs from a
unit that doesn't have standard audio outputs and converts that signal
into a type that can be universally understood by equipment in the
aftermarket. Sort of an international translator for audio signals.
LOC's have been used in Car audio for years and they are a proven
technology, however the problem with them is that when you take the
high-level speaker outputs and convert them to the preferred low-level
needed to drive an aftermarket amplifier, it introduced other problems.
The most prevalent being "noise" and noise in a high-end system is a
no-no. Many installers get around this issue by using a combination of
active equalization and filter circuits to clean up the sound, but since
this is all done after a digital signal from say a Compact disc has been
converted to analog the signal still suffers. Enter JL Audio.... JL
Audio for many years did one thing really well, and that was
manufacturer subwoofers. In the mid-90's they moved into Full range
speakers and more recently into Amplifiers and other car audio
equipment. With a reputation for producing quality equipment and a
commitment to their dealers to combat the on going battle between the
OEM and aftermarket audio manufacturers,
 they
created the CleanSweep. The CleanSweep is a new product which takes the
high-level signal from just about any head-unit on the market and
through built-in processing in the digital, not analog domain adjust
that signal to be perfectly flat, in essence bi-passing any factory
compensation or adjustments in sound. This flat signal would need to be
in turn equalized before you could get great sound, but the CleanSweep
basically gives installers a "clean-slat" to design a system from with
no interference from an OEM designer. Now you can design your sound the
way you want it.
With the decision to use the CleanSweep made, the
rest of the system was pretty simple. I generally live by the saying
that there is not one manufacturer of electronics that makes great
equipment all the way across the board. One may be really good at
speakers, the other at head units. Generally I live by this and go with
the best in each cate gory, however I have always been a big fan of MB
Quart speakers. An generally feel their products are top-notch, not to
mention I already had a couple pair of their speakers and a pair of
their new amplifiers in my shop. The M45 has speaker cut-outs and used
6.5-inch drivers in each of the four doors. I already had a pair of
Quart's Reference series 6.5's and a pair of their 6x8's that I had
installed in my Mazda Miata. The rear deck of the Infiniti has a cutout
for a 10-inch subwoofer, unfortunately calling this 2-inch thick Frisbee
a subwoofer is a major stretch. Luckily I already had one of Quart's top
end Premium line 10-inchers laying around making this truly a factory
upgrade installation. With the reference mid-range and hi-range
speakers, as well as the premium subwoofer our new frequency range
should be in the neighborhood of 20-over 20k Hz, the quart Tweeters are
capable of producing sounds all the way up to 32,000 HZ.
Next on the list of required components are the
amplifiers. Shortly after being acquired by Rockford Corporation, MB
Quart USA introduced a pair of lines of amplifiers. The High-end
Q-Series and the more mainstream series, Reference. To compliment the
Reference Line Speakers, I went with the Reference amplifiers. In this
installation a single Reference 4200, 100watts x 4channel amplifier for
the mid's and hi's and a Reference 1000, 400 watt amplifier for the
subwoofer. This setup will be more than ample for our needs and should
provide for both our #1 and #3 guiding principle. The last portion of
the equipment list is the most important, and one which requires the
most amount of flexibility. The equalizer in any system is what can make
or break you, in our case we wanted to have the maximum adjustability,
in the least amount of space. Even though it's design is a bit dated,
the Precision Power DEQ-230, 1/3rd octave Equalizer I also had laying
around will serve us well.
System Design
This portion of the process was pretty simple, due
to pre-existing cut outs in the doors and rear deck for speakers and the
fact that we are working on a sedan the only place for equipment would
be the trunk.
Day 1: Installation
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