July 26, 1998
By: Douglas Campbell (a.k.a. DC)

So, thinking about upgrading that stereo huh? Well, you’re not alone. As factory systems go, the Roadster’s isn’t too bad. In fact, it would probably sound great if it wasn’t in a ragtop. Unfortunately, it is. Most people who buy this car will be satisfied with this stereo. Some will perform a minor upgrade such as a speaker swap, etc. The rest of us are looking for something a little bit more substantial. So, where do we begin? Well, if you’ve ever read "The Art of War" you know that the very first rule in conflict resolution is "Know your enemy". So let’s take a look at the factory system in the M Roadster.

M Roadster Factory Sound System

• AM/FM/Cassette/CD Changer Controller Head Unit (made by Alpine)
• 6 Disc CD Changer (made by Alpine also)
• Factory amplifier
• 5.25" speakers in the kick panels
• 2" midranges in the doors
• 1’ tweeters in the doors
• 3" midranges behind the seats
• Two 5.25" "subwoofers"

1. With the top down and the car moving the stereo is pretty much useless.
2. The sound is muddy (lack of highs).
3. The maximum volume is inadequate.
4. The low frequency response is non-existent.

1. The head unit and changer although labeled as HK are actually made by Alpine.
2. The head unit has SSV and a weather band.
3. The factory equipment looks "stock", a great theft deterrent.
4. The front factory speaker locations are quite good (in terms of sound stage).

Upgrade #1 – The front speakers

GOOD – Replace the factory 5.25" midrange with an aftermarket 5.25" midrange. This size speaker is a drop-in replacement for the factory speaker – no modifications necessary. The MB QUART QM 130-TX3 are an excellent choice.

• Parts $130 - $150 for the pair
• Labor $25 - $40
• Benefit You will experience a cleaner, brighter sound with more usable volume.

BETTER – Replace the factory 5.25" midrange and the factory 1" tweeter with a good quality 5.25" component speaker set including crossover. The 5.25" speaker is a drop-in replacement as is the 1" tweeter. You will not use the crossover included with the speakers unless you are adding an aftermarket amplifier (see Best). The factory 2" midrange is left alone.

• Parts $175 - $225
• Labor $40 - $75
• Benefit More highs, better sound stage.

BEST - Replace the factory 5.25" midrange and the factory 1" tweeter with a good quality 6.5" component speaker set including crossover. I used Boston Acoustics 6.4 Pro’s. ($299, reg. $450)

The 6.5" Mid/Woofer will require minor modification of the kick panel to get it to fit. You’ve got 2 choices here. You can remove the plastic ring on the backside of the kick panel and mount the entire speaker behind it.

Or you can cut a round hole in the kick panel and mount the speaker through it.

The factory tweeter should be left in the factory location and disconnected. The factory 2" midrange should be removed and the aftermarket tweeter installed in its place using a simple bracket.

I suggest doing it this way rather than placing the tweeter in the factory tweeter location because you will experience better stereo imaging this way. It is kind of hard to explain why but I’ll try. You all probably know that the "sweet spot" is in the absolute middle of 2 speakers as opposed to being closer to one or the other. If the left speaker is 1 foot away from you and the right speaker is 3 feet away – that’s not so great because the right speaker is 3 times the distance away. But if the left speaker is 1.5 feet away and the right speaker is 3 feet away – that is much better because now the right speaker is only twice as far away. See what I mean? This is why I suggest using the factory location for the 2" midrange – it eats up some of the disparity. Finally, you will be using an aftermarket amplifier with this upgrade (see next section) and you will be using the passive crossovers supplied with the component speaker system.

• Parts $250 and up
• Labor $100 and up
• Benefit Excellent clarity and imaging, low end much improved over stock system by use of dual 6.5" mid/woofers instead of 5.25" midranges. HUGE IMPROVEMENT!!

Upgrade #2 – Aftermarket amplifier.
Note regarding any of the following options. Installing an aftermarket amplifier is pretty easy in this car. The battery is located in the trunk and so is the factory amplifier. I stuck the crossovers that came with my Boston 6.4’s in the factory amp location.

I temporarily mounted the ADS P840 amp to the carpet with Velcro pending my decision regarding subwoofers in the trunk.

GOOD – Use a decent 2-channel amplifier to feed your new front speakers. I recommend a minimum of 40 to 50 watts a channel – remember…this is a ragtop. This amp should be able to accept "high level" inputs from your factory head unit.

• Parts $199 and up
• Labor $50.
• Benefit Vastly improved volume and dynamic range.

BETTER – Use a multi channel (at least 5 or 6) to amplify your entire systems and bypass your factory amp entirely. 2 channels to your new front speakers, 2 channels to your factory rear speakers and 1 or 2 channels to the factory subs.

• Parts $249 and up
• Labor $50 - $75
• Benefit Increased rear fill and improved low end. BE CAREFUL not to overpower your subs!! While most speakers fail due to too small of an amplifier being driven into distortion (and the distorted signal destroying the speaker’s voice coil), speakers reproducing low frequencies can be "overdriven" with too much power, clean or otherwise.

BEST – High current/high power multichannel amplifier (or multiple amplifiers). I used the ADS p840 amplifier ($565, reg. $699 or so). This is an 8-channel amplifier with built-in electronic, adjustable crossovers rated at 8 x 40 watts.
I bridged 4 channels to create 2 channels at 120 watts/channel for my Boston Acoustic 6.4’s in the front. Using the electronic crossovers in the amp (as well as the passive crossovers supplied with the speakers) I restrict the frequency response of these speakers to 65HZ to 20KHZ. By removing the lowest frequencies from these speakers, I prevent damage to these speakers due to overdriving. This basically means I can crank the volume up to ear piercing levels without worrying about damaging the speakers. 2 channels (at 40 watts per channel) go to the factory rear speakers and the remaining 2 channels (at 40 watts per channel) go to the factory subs. The factory amplifier is being used as a paperweight on my workbench.

• Parts $399 and up
• Labor $75 and up
• Benefit With this combo (amp and front speakers) the sound stage and imaging is excellent and the volume is awesome. The only downside is that the fronts are so good that it makes the lack of real bass (20 HZ to 60HZ) all the more noticeable. Sighhhhhhhhhh…….

Upgrade #3 – How low can you go……

GOOD – Live with the improved low end from your new 6.5" front speakers.

• Parts $0
• Labor $0
• Benefit N/A

BETTER – A custom fiberglass enclosure in the passenger footwell with an 8" subwoofer. This will improve the low end substantially (if properly designed) but will obviously effect legroom for your passenger. JL AUDIO makes some very nice subwoofers, as does KICKER.

• Parts $150 - $200
• Labor $250 - $300
• Benefit Improved low frequency response. Your car won’t BOOM but you should have usable bass down to about 30 HZ.

BEST – Custom enclosure in the trunk firing into the cabin. This is the only way you will get truly mind-numbing bass response in the vehicle short of MAJOR reconstruction (i.e., modify kick panel to take 8" woofer, etc.). Be prepared to have your baby out of commission for a few days (minimum), tolerate moderate cutting to port the sound into the cabin (probably not a good idea for those who lease), the loss of half of your trunk and a hefty bill at the end (at least $800, more like $1200). If you can live with these costs, you will enjoy the BASS that the rest of us can only wish for.

• Parts $500 - $700
• Labor $300 - $500
• Benefit Truly awesome Bass!!

To be covered next time

Upgrade #4 – Rear Speakers

Upgrade #5 – Aftermarket Head Units