Our “Miazda”
2008 PHRT MX-5 Touring

UPDATE: THIS CAR IS NOW FOR SALE. CLICK HERE FOR DETAILS.

When my wife and I test drove a MX-5 GT several months ago, I wasn’t very thrilled with the audio system despite the dealer touting the Bose name on the head unit. I figured that a Touring model would be a better choice for us and since I knew the audio system was going to have to be replaced sooner or later and the heated leather seats would be of little interest.

So we purchased a Touring model with PRHT without giving much thought to the audio side of the car. On the ride home, I knew “sooner or later” would be much sooner. The sound in the Touring version of the car was absolutely pitiful. There was too much midrange and almost no bass. My favorite CD’s sounded so bad, I couldn’t stand to listen to them at even low volume levels.

My opinion has always been that most factory head units can process good quality sound but they are rarely paired with good speakers and adequate power. My thoughts on this proved to be right (in my opinion) with the Touring MX-5. Here’s what I did and why.

Decisions, Decisions

The factory head unit in the Touring has two features that I really like. The first is the steering wheel control. I love this feature and I didn’t want to lose it. I know there are adapters for most steering wheels to allow continued use with non-factory head units but these units are plagued with a “delay” problem that I knew would annoy the bejesus out of me everyday. The other feature I’ve grown to appreciate is the auto sound level control (ASL) which lowers the volume of the stereo when the car slows down or comes to a stop. I didn’t want to lose this feature either.

So I opted to keep the factory head unit and power new speakers from an Alpine F250 which accepts speaker-level inputs from the head unit (no line level converter needed). This is an affordable amp with a good reputation that powers the speakers perfectly. I figured that I had two options for using the four channels of this amp.

1. Power the fronts on channels 1 and 2. Power the rears on channels 3 and 4.
2. Power the fronts on channels 1 and 2. Power the rears from the head unit and save channels 3 and 4 to be bridged for a future subwoofer upgrade.

I went with the first option figuring that if I ever wanted add a sub, I could rewire the rears to power off the head unit very easily from the trunk (where my amp is located).

I’m a big fan of Polk car audio and bookshelf speakers. Their larger home theater speakers are nice too but I prefer Boston Acoustics for that kind of use. The car audio Polks have a nice array of sound without being too tinny or boomy. They sit just in the middle with crisp highs and punchy lows. For this installation, I chose their DB6501 component speakers for the fronts and DB351’s for the rear fill. I bought these sound-unheard (like sight-unseen) knowing that my previous history with Polk’s has always been good. I have owned Diamond Audio speakers and MB Quarts in the past. The Diamonds did not impress. The MB’s were too expensive for what they offered in terms of sound quality.

Alpine MRP-F250

Polk DB6501

Polk DB351

Knowing I would be removing most of the car's interior to run a lot of wire to the trunk, I decided to use this opportunity to install a significant amount of sound deadening material throughout the cockpit and trunk. I opted for RAAMmat BXT and its companion, Ensolite.

I’ve never been too impressed by the effects of adding sound deadening but I suspect that is largely because I never used enough of it or I used it in cars that didn’t really need it to begin with. But using such a substantial amount of deadening in such a little car has indeed made a noticeable difference. How noticeable? Let me describe it like this...

• Previously, my wife and I found it necessary to raise our voices (even with the radio off) to maintain a conversation on certain road types. With the sound deadening, we can maintain conversation at lower-than-normal volume levels regardless of the road surface.
• The stereo can now be heard at a low volume while driving. This is nice because it means we can have the stereo on and speak to each other without having to lower the volume when one of us has something to say. In other words, we can leave the radio low enough that we can hear it but we can still talk to each other without having to raise our voices.
• The doors open and close with the sound of a high-end Lexus. It’s quite a satisfying sound.
• With the PRHT up, the exhaust note is somewhat attenuated but you still hear it when you lay into the pedal. Without the auditory demand for attention from the exhaust, I now hear more engine sound which is pretty cool and is no doubt part of the experience of driving this car.

Take It Off !

1. We lowered the PRHT and put the windows in the full up position.
2. Then we removed the negative battery wire and taped over the terminal just in case the wire slipped and made contact.
3. Next the seats were taken out. To do this we removed the four bolts that hold the seats to the car frame. We folded the seats forward in the “anti-recline” position and pressed backwards on the head rest to allow easy access to the connector underneath. The driver seat can be removed completely from the car with no problem but the passenger seatbelt is attached to the seat so it can only be moved out to the side of the car (still attached by the seatbelt).
4. The sill plates pop off easily. After that we removed the center console area starting with the plastic snap-on piece behind the cup holders. There are two screws under this piece that must be removed. Next we found a screw under a cover plate on the front cup holder in the console arm rest. That plate pops out easily. We finished up the console removal by popping out the coin tray in front of the shifter. This was a bit nerve racking since it was secured with some very strong clips. Under the tray are two small screws that hold the front of the shifter console in place. We unscrewed the shift lever knob and popped the e-brake boot bracket off the console starting at the back side of the bracket. The boot slips off/over the e-brake handle with no problem. We later learned that it is much easier to remove the shifter console if you put the car in neutral first (with the e-brake engaged).
5. Next we removed the windscreen between the two headrests. Again, this was a bit nerve racking since it is held in place with some strong clips.
6. Removing the roll bar covers came next. There was just a few snap on clips here so this was no problem.
7. The back panel is easy to remove at this point. It’s all snaps. No screws.
8. We then removed the rest of the door sill plates and the front kick panels. We also removed the dead pedal at this time which is held in place with a single 10mm nut.
9. The last thing to come out of the cockpit was the carpet. We did not actually remove it. Instead we rolled it up toward the center console while we worked on applying the sound deadening to the floor pans. A couple of spring clamps held the carpet out of the way.
10. The door panels were then removed. This process was not as difficult as I thought it would be. There are tutorials on the Miata.net forums that discuss this. Do a search!
11. We then removed the trunk plastics and carpet. This is an easy process that really needs no explaining.

Random Shot 1

Random Shot 2

Time to Kill (Kill Unwanted Sound with Deadener)

1. RAAMmat was applied to the outer-most door side skin and Ensolite was applied by spraying it with contact spray and quickly sticking it to the deadener. We did not spray the contact adhesive directly onto the RAAMmat. At first, this seemed like a mistake but within an hour or so, the Ensolite had a good bond to the RAAMmat.
2. We also applied the deadener and Ensolite to the door beams inside.
3. The inner-close side of the doors is not easy to attach deadener so we pieced together as much of that as possible.
4. Then we applied the Ensolite to the door before we re-attached the plastic door part that holds the speaker and keeps the door wires in position.
5. The cockpit floor was given two layers of deadener. All other areas inside got one layer including the back wall and the transmission tunnel. This is also a great time to cover the "black hole" near the driver seat.
6. Ensolite was then attached to all deadener inside the cockpit.
7. We then began applying deadener in the trunk. We put one layer all around and a second layer on the sunken part of the trunk bay. In fact, that sunken area really could have used 3 or 4 layers but I was about to run out of deadener so we had stop there.
8. There is also a metal bracket in the trunk on the driver side. It covers the fuel pipe that directs fuel from the filler door to the fuel tank. We covered that piece with deadener.
9. The "shelf" that sits under the retracted hard top was also covered with deadening material. This was done after the car was re-assembled. To get to the shelf, we put the top up but stopped the closure process before the automated hatch cover (whatever that thing is called) started to move back down. This allowed access to the carpeted area below and behind the the are where the hard top stows.
   

Rear Wall Matted

Cockpit Matted

Driver Door Ensolite Finished

Passenger Inside Door Matted and Ready for Ensolite

Passenger Door Ensolite Finished

Trunk Almost Completely Matted

Trunk Matting Details

Speaker "Fun"

• The rear speakers were not a perfect fit at first. I used an air powered die grinder to expand the factory speaker bracket holes by 3/16”. This was time consuming because the bracket holes are rolled back so it was quite a bit of initial metal to remove. After that, mounting the rear speakers was no problem.
• The front speakers are components. I used ¼” thick clear acrylic because it was readily available. The other nice thing is that it is clear so you can see exactly where the speaker hole needs to be cut out.
• I sealed the back side of the acrylic with closed cell foam tape (vacuum chucking tape; see below). Polk says it is critical to seal this opening as well as possible to get the best bass response.
• The tweeters were mounted in the stock location by using the factory tweeter mounts. I popped out the tiny factory speakers and attached the plastic housing to my wood lathe. Cutting out a perfect circle to fit the Polk tweeter cradle was no problem. This could also be done with a Dremel rotary tool.

Rear Speakers Mounted

Completed Woofer

Driver Door Wired

Lathe Jig for Mounting DB351's with Factory Tweeter Plate

Woofer Adapter w/ Gasket Tape (aka Chuck Tape)

Wire Everywhere!

• We ran two wires from each speaker location back to the trunk. One of these wires would feed the amp with the factory speaker sound. The other wire powered the new speaker from the amp.
• The crossovers were installed inside the door because there was absolutely no way to get 2 sets of 14 gauge wire through Mazda’s insanity-inducing connectors under the rubber boot between the door and the car A-pillar. More about this in a minute.
• We fed all of the speaker wires to the trunk by keeping them in the center of the back wall. Even with the roof down, the wires went under the factory padding with no problem. We did have to cut out a hole in the back wall of the trunk to get all of these wires through.
• With all of these wires in place, the only two wires left were the amp power wire and the remote turn-on wire. The amp wire was brought through the firewall at the hood release grommet. We had to create a hole in the grommet with an awl. After that, the wire pulled through easily. The amp wire was run across the floor pan towards the transmission tunnel. We used the sound deadener to adhere the wire to the side of the tunnel and from there we routed it back to the trunk. Again we kept it near the center (left to right) of the car but about 4 inches away from the speaker wires. Before we pulled the final part of the amp wire through, we wrapped it with foil tape to minimize electrical interference with the speaker wires.
• In the engine compartment, we ran the amp wire to the battery as shown here.
• The remote turn-on wire was run along the same path to the trunk as the amp wire but it was started at the cockpit fuse box. We used an "Add-a-Circuit" to connect the remote wire to the radio fuse.

The Hard Part – How Many Times Did I Say “We’re Screwed”?

1. There is a black rubber boot that hides the wires coming out of the A-pillar section of the car going into the door. Under the boot is a plastic connector. This thing is a nightmare and a royal pain in the rear. To remove it, we needed to pop the connector assembly (while the female and male parts were attached) from the car frame. Then we had to open the blue bridle on the harness to separate the two parts of the connection. This would be easy if there were more than 3 cubic inches of space to work in. There is less, I assure you.
2. To make room for the 14 gauge speaker wire, we used a Dremel tool and a small deburring bit to open up several unused sections inside both the male and female side of the harness. This takes a steady hand and keen eye. This is not for the faint of heart. The area we cut out of the harness are different on the driver side than on the passenger side. The driver side was a bit harder to do because the pins on that harness are more evenly spaced apart than the other side.
3. There was a lot of plastic dust from the previous operation so we vacuumed the areas thoroughly and blew-out the connectors with compressed air.
4. Then we made a note of the factory speaker wire going to the factory speaker. I clipped the wire on the inside harness and pulled it back into the cockpit. This is the wire that would feed the sound to the amp.
5. We slid the new speaker wire up through the opening in the A-pillar and pulled it through the holes we cut in the harness pieces. From there we snaked it through the rubber boot to the new speaker. It’s very easy to do this if you lube the wire with some liquid hand soap first.
6. We attached the male and female connectors together and prepared to reinsert the harness into the A-pillar.
7. At this point, “We're screwed” was said about a dozen times. Why? Because the freagin’ harness is nearly impossible to get back into the A-pillar hole. It took a lot of coaxing, a lot of prayer, a lot of screaming, and a lot of luck. The problem is that the factory hole is only about 1/100” larger than the harness and the harness has to be inserted straight in. It will not go in at an angle no matter what. Keep in mind that you only have 3 cubic inches to fit your fingers and this giant harness into. If the car had more than 600 miles on it when we did this work, I might have considered taking the door off its hinges to this. It would not have been pretty.
8. After a well-deserved sigh of relief when the harness made it into the opening, we snapped the harness into the A-pillar but the battle had just begun. Getting the rubber boot fully wrapped around the plastic harness is an exercise in patience. The boot has to be attached before the harness is fully snapped back into the hole. Figure on 20 minutes minimum to get this done unless you have miracle fingers.
9. Once the boot is on, you can snap the harness fully into the A-piller hole.
10. Then we attached the crossovers to the door panel with screws, lock washers, nuts, and thread locker. I used the chucking tape on the edges of the crossovers (where they contact the door) to prevent rattling.

The Infamous Boot

Driver Door Harness A

Driver Door Harness B

Re-Assemble The Car and Build the Amp Holder

1. Before the panels were re-attached to the car, we checked for any wires that might rattle against the panels and wrapped them with chuck tape.
2. The process of reassembling the car was a piece of cake. It took two of us about 90 minutes. The extra height from the deadener made only a slight impact on the front seat bolt hole alignment. So we attached them loosely first, then attached the back side bolts. The rest of the panels re-attached with no problem from the extra thickness of the deadener.
3. We did have to cut some of the hard foam block on the door panel to allow room for the crossover.
4. After the cockpit was reassembled, we started putting the trunk back together but left out the forward-most part of the plastic panels so we could figure out how to mount the amp.
5. This wasn’t as difficult as I though it would be since the amp is so small. The amp is basically held in place with a stack of ¾” thick plywood pieces which were cut approximately 5” x 6”. Each was painted flat black. Then we assembled one to the other starting with one on the back side of the plastic panel for rigidity.
6. Before attaching this final piece, we cut away some of the trunk plastic to bring the speaker wires through. Another set of holes was cut in the plastic panel behind the amp mount for the power, ground, and remote wire.
7. The top piece of the stack was cut much larger to match the shape of the amp. We screwed this piece onto the stack and then attached the panel to the trunk interior.
8. After that, it was just a matter of attaching and wiring the amp.

"Rigidity" Piece on Back of Trunk Panel

Amp Mount Plywood Layers

Amp Mount Cut to Fit Alpine F250

Door Foam Cut Out

Amp Attached and Wired

Take a Breath, Take a Ride

The moment of truth was uneventful… thankfully. Everything came on perfect. The amp powered up and the speakers began to sing. I popped in Rush’s Snakes and Arrows CD and cranked it up. It was wonderful. My assistant with this install is no Rush fan but even he admitted that the CD sounded outstanding.

Worth It?

Sound Deadening: Yes. Especially if you are bothered by road noise or frequently carry on a conversion inside a closed PRHT.

Front Speakers: Definitely worth every penny. Good highs, excellent coverage, and nice punchy bass hits. The low frequencies of these speakers will take several weeks to show up. There is supposedly a kind of break-in period for many car speakers before the truly audible bass comes out. I’ll wait patiently.

Rear Speakers: There is a lot of talk about the insignificance of rear speakers. I strongly disagree. They provide a great fill that eliminates the sense of direction in the front/back sound. With the rears faded off through the head unit, the sound is noticeably front-oriented. I prefer to be surrounded by sound and the rear speakers do this nicely.

Amplifier: That’s a given. I wouldn’t even try to power these speakers with the factory head unit. This little Alpine unit was perfect for this audio project.

Total Time: 65 hours (split between two people; I could probably do this in 1/3 of the time if I had to do it again)

Lessons Learned

• We found the best way to keep track of the screws for the car was to poke them into a piece of cardboard and then write its location under the screw.
• We learned that it is much easy to remove and install the shifter console if you put the car in neutral first (with the e-brake engaged).
• When removed, the passenger side seat will stay attached to the car via the seat belt. Be sure to cover the seat belt area where it contacts car body to prevent scratching.
• The Polk crossover can enhance or attenuate the tweeters by 3 decibels. I’ve found the best sound by setting the crossovers to use the -3 setting (attenuate).
• You will break some of the white plastic snap-on clips when removing the door panels. Get some. You will definitely need them.

After a while, the only decent sound I got was when my Ipod was attached. The bass still wasnt where I wanted it. I tried a powered sub in the trunk. I don't remember the model but it was the larger of the two available Blaupunkt units. The sub sound was awful. The bass seemed to come and go with nothing dynamic reaching my ears so I returned it. I still think this was a well-made subwoofer but it just didn’t work for me. I now know why. Keep reading.

Not being satisfied, I decided it was time to get a new head unit. I opted for the Alpine IDA-x100. This unit gets great reviews and it’s mostly black. The newer version, which uses the same firmware, has some silver/chrome parts which might not look as good with the black NC dash. Best Buy was closing this “older” model and I managed to get one of the last ones for $199. I also bought the companion PXA-H100 on Ebay for $99. This add-on device allows some extra EQ features and reduces the wiring behind the H/U. One thing that should be mentioned is that it’s a shame the Alpine forces you to buy this addon just to get more sound adjustment. However, with this addon, all of the line level audio is passed through a single proprietary wire from the H/U to the addon box. This greatly reduces the amount of wire behind the H/U. I put the addon box under the passenger seat and ran RCA audio cables from there to the amp in the trunk. Six foot audio cables were the perfect size for this.

I bought a wiring harness and Metra dash kit from Crutchfield. The Metra kit is a fine match for the OEM dash plastic but in it, the head unit sits too far back to look good. After much deliberation with Crutchfield, they sent me a GM dash kit (part #120 99-2001) that had a plastic spacer with it. I had to cut out the center supports with a Dremel tool but the spacers brought the H/U out by 3/8” and now it looks much better.

So how's it sound? Oh... so much better. The bass pounds my left leg now. The Polk's are doing what they were meant to do. I doubt I'll need a sub now. I generally listen to classic and day-to-day rock like Rush, Police, Rush, Eagles, Rush, Nickelback, and Rush. For this kind of music, the system is near perfect for me.

I also installed a PAC steering wheeling adaptor for the Alpine unit. As others have mentioned, there is a very annoying delay from the wheel to the H/U now. Instead of just clicking the steering wheel volume up or down, you have to hold it a bit longer. Multiple quick-clicks of the steering wheel buttons do nothing. It definitely has a learning curve for the timing of the button presses to get the H/U to do what you want. Overall, I prefer this annoyance over not having any wheel control at all.

I theorized about why the new H/U has better bass and then researched it on a few websites. I was right. The factory H/U does not pass most low end bass frequencies. So no matter how good your aftermarket speakers are, they will not produce a good medium to low bass because the factory H/U filters it out. The difference between the factory H/U and the Alpine H/U is night and day in terms of bass. I’ve also learned that there are audio devices that can be wired into the factory system that restore the bass frequencies but they are as expensive as the head unit.

One last thing… Alpine offers a special microphone and software package which creates a parametric EQ setting by sending sounds through the speakers (using a laptop computer) and measuring the frequencies returned through the microphone. I got suckered into buying and found it to be a waste of money for this particular car and audio set up.

I still don't get the consistent sound I want. With the top up (I have a PRHT) the acoustics are usable and I can get close to a good sound. Top down is a different story. The acoustics with the top down are ever-changing. Cars around you, wind noise, tire sound, etc all effect it. I tweak the EQ until I have it near-perfect but as soon as I get on the road, everything changes. If I tweak it while driving, everything changes if I get up to speed. Then at a red light, it  changes again and sounds awful.

Here are a few things worth mentioning.

1. Dont expect to get good sub bass sound. For the amount of space that subwoofer takes up, you get very little in return. I currently use a Bazooka in the trunk but I've found that I get acceptable bass just from the Polk speakers I have if I tweak the EQ a bit. Keep in mind that Polk speakers seem to take forever to develop their full bass sound.
   
2. If you keep the factory head unit, know that it will not pass a lot of the low frequency sounds to after market speakers. The factory HU is designed to protect the lame factory speakers from low end distortion. The factory head unit used with aftermarket speakers is almost waste unless you invest in a bass-rebuilder. Crutchfield has them but they are as pricey as a new head unit.
   
3. Dont expect flawless "full time" sound. It just wont happen in a convertible.
   
4. For me, the best sound source comes from my Ipod with the "Rock" EQ setting.
   
5. The PAC device for controlling an after-market stereo with you steering wheel is awful. The time lag is unacceptable to me. And it wont work with Alpine head units at night if you have the dimmer wire attached (the wire that dims the stereo display when the head lights are on). When you turn on the head lights, the wheel control stops working. I worked with PAC Audio for so long to try to remedy this, that by the time they concluded that it couldn't be resolved, it was too late for me to return it to the store.
   
6. The Alpine HU I have is impossible to read during the day.
   
7. If your factory HU is the kind that lowers/raises the volume based on the speed you are driving... you may find that you miss this option if you switch to an aftermarket HU. There will be other trade offs of convenience for sound.
   
8. I recently added a mesh blocker and the cabin is much more quiet at speed now and this has help me find a good and consistent setting with my EQ.

If I had to do it all over again, I would keep my factory HU and use the Alpine amp to power the speakers. But I would have invested in the bass-rebuilder module so that Polk speakers can deliver the best bass. This would have allowed me to keep the simplicity and convenience of the factory HU and steering wheel control and not give up the sound.

Sources

Polk DB6501 Component Speakers (Ebay - $115)
Polk DB351 Speakers (Crutchfield - $60)
Alpine IDA-x100 Head Unit (Best Buy - $200)
Alpine PXA-H100 Imprint Sound Manager (Ebay - $100)
Alpine MRP-F250 Amp (Crutchfield - $150)
Metra Dash Kit (Crutchfield - $15)
Wiring Harness (Crutchfield - $8)
200 Feet of 14 gauge wire (Lowes - $50)
Add-a-Circuit (Pep Boys - $10)
Four yards of Ensolite (Raamaudio.com - $24)
Two can of spray adhesive (Raamaudio.com - $8)
62 Square feet of RAAMmat BXT (Raamaudio.com - $120)
Monster 250 watt amp kit with 8 gauge wire and 30 amp fuse (Amazon - $27)
6 Disposable razor knives (Dollar Store - $1)
14 Replacement door clips part# GJ6A-68-AB1 (Mazda dealer - $.75 each)*
Crimp connectors (Lowes - $5)
Adhesive foil duct tape (Lowes - $7)
¼” Thick acrylic for front speaker mounts (Lowes - $14)
5 Rolls of vacuum chucking tape (VeneerSupplies.com - $3.25)**

* We used Heritage Mazda in Bel Air, MD for the door clips. They are not my first choice for service or sales but the parts guy there (Scott Hurley) is very cool to work with.

** VeneerSupplies.com is a business owned by my wife and I. We sell this chucking tape for a completely different use but it is excellent for wrapping wires to prevent them from banging around on hard surfaces.

If you have any questions about my install or any of the parts I used here, feel free to contact me.