Basic Theory
In designing an accurate car stereo, there are some basic tenets that you need to be aware of. A car stereo attempts to reproduce the sound of a concert as accurately as possible. A human with perfect hearing can hear sounds within the 20 Hz to 20,000Hz range. In a good to excellent system, you should be able to close your eyes, and it will sound as if the lead singer is singing from an imaginary point, located about a foot or so in front of the center of your windshield. All of the other instruments should sound as if they are located in relation to the singer. I.e., if the lead guitar is to the right of the lead vocalist on stage, it should sound as if they are to the right in your car. This is commonly referred to as “staging” or “imaging” and is primarily a function of the tweeters and Mid-range speakers. Bass is non-directional, thus you can locate subwoofers pretty much anywhere space permits. If you are using ported enclosures, it is important to “corner load” the speaker, this refers to pointing the port into a corner of your car. This disperses the bass evenly through the car and helps reduce “port noise”. You will get better, tighter bass from a sealed subwoofer enclosure. The trade off is that it takes more amplifier wattage to power a sealed system to the same SPL (sound pressure level) as a ported enclosure.
Rear fill
These speakers are designed to reproduce the
“reflections” from the rear wall of the concert arena or hall; the sound
passes your ears on it’s way from the band, then reflects off the rear
wall to your ear. Rear fill speakers make your sound seem much more
lifelike. These speakers are largely unnecessary in the MR2, due to the
small size of the cabin. Rear fill is actually provided naturally by the
front speakers reflecting off the rear glass and roof of the MR2. If you
do choose to utilize these speakers, they should be powered at a very low
level in comparison to the rest of the system or you risk pulling the
sound stage toward the rear of the cabin.
Speakers and location
Tweeters-Designed to reproduce sound from 5,000Hz to 20,000Hz
Arguably the best location for the tweeters in an MR2 is surface or flush mounted in the kick panels, aimed upwards at the center of the roof. This provides an almost even distance from each tweeter to the driver’s ear, as opposed to the stock location, where the passenger side tweeter is nearly twice as far from the driver as the driver’s side tweeter. The stock tweeter placement results in the driver adjusting the balance control heavily toward the right side, with the net effect being that the passenger only gets to hear the tweeter on his side of the car. Another issue with mounting tweeters in the stock location is that this places the tweeters on a separate vertical plane from the midrange speakers which is a bad idea. The tweeter and midrange are designed to sound like one speaker when properly mounted on the same plane, or as near to it as possible.
Midrange-Designed to reproduce sound from ~100 Hz to 5,000Hz
Five and a quarter inch midrange speakers will bolt right into the stock door locations. Depending on the brand of speaker and their particular mounting pattern, you may have to drill some small mounting holes. Some six-inch midrange speakers will fit as well, but may need spacers in order to avoid impacting the power window mechanisms. The size of the speaker magnet is also a concern when mounting six-inch mids.
Subwoofers-Designed to reproduce sound from 20Hz to 80 or 100Hz
This is by far the most frequently asked question when it comes to MR2 car audio. The most common solution for both MKI and MKII installations seems to be the Southern Audio Service Bazooka System. People have installed one, or two, powered and non-powered (passive) and both 6.5 inch and 8 inch versions. To further confuse the issue, SAS makes 2 levels of each, the EL (read cheap) and the upscale RS version. The consensus would seem to be that the RS is by far the better alternative, budget permitting. The 6.5 inch bazookas will fit behind the seats of both versions of the MR2 with virtually NO impact on seat travel. They provide far more bass than the various OEM stereos produced by Toyota. They do have limitations however. The ports are tuned at 39Hz, which means that you will experience port noise during particularly low passages of music (Rap is the worst offender here) The majority of music is above 39Hz on the spectrum however, and these speakers do an admirable job of reproducing the frequencies within their design limitations and will reach fairly high SPL’s with a minimum of amplifier power. The downside in an MR2 is that you lose your storage space for the T-Tops (if you have them). Properly installed, crossed over, and adequately powered, these speakers will satisfy about 90% of car audio enthusiasts. The other 5% should probably look into custom subwoofer enclosures.
Source(Head unit)
FM Radio
FM is widely utilized by people for several reasons. It’s “free”. You
get to hear the latest music and make informed purchases. Variety. There
are many other reasons, which I won’t go into in this forum.
Downsides:
Reception-FM reception is highly variable, depending on distance from the
transmitter, power of said transmitter, and any obstacles between your car
and the transmitter i.e. buildings, mountains, etc. Musical Range: Even in
a high end receiver, FM is limited to approximately 16,000Hz, which means
you are effectively chopping the top 20% of your music off. (a good reason
to NOT install an add-on CD changer via an FM modulator) The signal to
noise (static or hiss) ratio is also very low, (higher is better) compared
to other sources.
Cassette
This format is falling increasingly by the wayside. Compact Disc has
largely replaced the cassette in many car stereo applications.
Pros:
You can record your own cassettes. They require minimal storage space.
Prerecorded music is widely available on cassette. They are relatively
inexpensive when compared with CD’s.
Cons: Musical range. While better
than FM, it is still near impossible to get a cassette player to reproduce
the full dynamic range (20Hz to 20Khz) accurately. The signal to noise
ratio is also better than FM, (around 65dB) but still falls far short of
compact disc.
Compact Disc
The CD is by far the most prevalent source for audiophiles everywhere.
The dynamic range exceeds the human range of hearing (typically 5Hz to
25Khz) Signal to noise ratio is VERY good, typically 90 or 95dB, compared
to cassette’s 60dB. There are high-end head units with 100dB, 105dB and
even 110dB signal to noise ratios. CD’s are far more durable than
cassettes, you get instant track access (no rewinding or fast forwarding)
and prerecorded music is widely available for this format.
Cons: until
recently, you could not record your own CD’s, thus you were at the mercy
of the recording studio as to what songs were available on what disc. The
advent of the CDR/W (Compact Disc Record/Re Write) may soon reduce or
eliminate this disadvantage. MD (mini disc) does a much better job of
filling this shortcoming.
Crossovers
Passive
This type of crossover is primarily used in component speaker systems, between the midrange and the tweeter. This is what is known as a “high pass” application. It typically allows only frequencies above 5Khz through to the tweeter. This prevents the tweeters from distorting and possibly blowing as they try to reproduce frequencies below their design parameters.
Active
This type of crossover goes in line downstream of the head unit, upstream of the amplifier. It typically has both low and high pass crossovers. The low pass sends the bass frequencies to the subwoofer amplifier; the high pass sends everything else to the midrange/tweeter amplifier. With the crossover points set correctly, it can minimize or eliminate distortion created by speakers getting signals they are not designed to reproduce. This is a critical component in a properly set up system. Many modern amplifiers come with integrated variable crossovers built in. Especially the multi-channel amps (4 or more channels)
Amplifiers Car amplifiers may be the least understood component of the car stereo installation. With manufacturers like Jensen and Kraco and various other department store brands making wild claims of 150 watts per channel x 2 for $99 or some such nonsense, it’s easy to fall into their trap. When you purchase an amplifier, you truly do get what you pay for. False advertising? No. What they are not telling you is that it is “Peak Power”, not continuous. They are also not putting in bold print that there is 5% distortion at that power level, versus the .5% or lower that is the maximum distortion acceptable without compromising your sound quality. Once again, you also have to compare the signal to noise ratio. A good amplifier should be well over 85dB, the higher, the better. Otherwise you just wasted all of the money you spent getting a CD player and great speakers, not to mention that you’ll probably blow the speakers with all of the distortion the amp is putting out. There is an increasing trend among mid to high-end amplifier manufacturers to underrate the power output of their amplifiers. The reason they do this is to allow us to compete in a lower class with their products. For example: my MTX Blue Thunder Pro 504 is rated at 55 watts continuous power x 4 channels at .1% total harmonic distortion at 14.4 volts. The amplifier tests out on the bench at 80 Watts x 4 with the above specs. This allows me to compete in the under 300 watts category, even though the actual output of the amp is 320 watts. You may never compete, but this numbers game still works to your benefit, you will pay for fewer watts than you actually get.
MINIDISC (contributed by Dane Miller)
Minidisc is a relatively new format that has only recently become affordable to the general public. Since it's introduction it has been used mainly by audiophiles and in professional environments due to the post-recording editing abilities that it allows. The discs are only 2.5" square and will hold various lengths of music recordings like a cassette (60 min., 74 min., etc.). The discs are scratchproof, (unlike a CD) which makes it a really good format for the(mr2) automotive environment. Also car MD receivers almost always employ a buffer memory system to minimize the possibility of skipping.A Minidisc recording will offer the same digital sound quality as CD players and with the same instant track access that CD enthusiasts have grown accustomed to.The best known overall feature of the MD is infinite re-recordability, allowing the serious car stereo enthusiast to make their own mix MiniDiscs from any music source (CD, DAT, Cassette, LP, etc.) and remove/add songs at any time, and also do some serious editing.As of this writing, MD home recorders start right under $200 and the blank 74 minute discs are about $3, opening up a whole new world of possibilities to serious stereo enthusiasts and the general public alike!
Equalizers (contributed by Dane Miller) (passive)Graphic equalizers give the car stereo enthusiast more precise tone control over various frequencies. Although they are not 100% necessary for a good sound system, they allow the user to tweak the way the music is reproduced and help compensate for the car interior's shortcomings. Most equalizers on the market today incorporate high and low pass filters and level control for a subwoofer making it a cost-effective alternative to expensive multi-component setups.The best characteristic of the in dash equalizer is that it allows the user full system sound control from the driver's seat. Currently EQs are available in bare bones priced models that just"equalize" to very expensive versions adding popular features like DSP (Digital Sound Processing), BBE (forgot), parametric equalization, and the most popular: spectrum displays.
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| Custom Stereo Install | 8 Inch Sub in Factory Box | 8 Inch Sub Behind Passenger Seat |  |
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| Erlin Loving's custom amp install | Amps mounted in Front Trunk on custom Plexiglas Amp Rack | Closeup shot of custom amp mounting |  |
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Michael Maas' twin Rockford amps mounted on the firewall | Rockford Crossovers- picture courtesy of Michael Maas | Closeup shot of Michael Maas' sub |
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| Blue Thunder Pro 504 Amplifier | Blue Thunder Pro 504 Amplifier (Again) | 6.5 inch Bazookas |