v8 Miata Forum - Home of the v8 Miata Conversion - Sound system blueprint for Nb Miata

Hi All,

I just hought that I would share some experiences that I have had recently in putting in a new sound systems into my NB. I did a fair amount of research before I settled on my final setup and it has turned out extremely well. So if you are keen to put in a new sound platform into your Miata/MX5 then this can work extremely well. It is by no means the best, the baddest, loudest etc. but it provides an excellent level of clarity, balance (hi, mid and low frequencies) and power.

The head unit is a Pioneer DEH80PRS - Wow! what a great deck once you get used to using the interface (its not straight forward initially but makes sense after a bit of use). Has one of the cleanest output signals out there. Which means that at full volume it puts out a totally clip free signal. Sweet! On top of that it allows full flexibility to adjust all the frequency crossover points for hi, mid and low pass filters. This means that you can use this head unit in Network Mode or fully active mode. This means that you do NOT need any passive crossovers in your system. Check it out online for more technical details.

I ran this deck in Network Mode and I turned off the internal amp.

The amplifiers I used were the Rockford Fosgate amplifiers: I used the T400x4ad (4 x 100 RMS) to drive the tweeters and mid range component speakers on separate channels and a T400x2ad bridged (1 x 400rms) to drive the subwoofer. I used these amplifiers because they are very small and have a lot of power for their size. There is precious little space in the car to mount them so this setup works very vert well. I mounted the amplifiers in the trunk. I mounted one on the car in between the two trunk hinges on the sloped part of the body, just above the boot liner trim in the middle. And the subwoofer amp I mounted directly to the subwoofer enclosure box for easy removal as a single unit.

The component speakers in the doors are the Pioneer Z series TS-Z65CH. These are a Hi Res Audio certified speaker which sounds very clean. I like them a lot. I did NOT use the passive crossover that came with them as I am using the head unit to finely control the crossover points. I tried it with the supplied passive crossover from pioneer but the sound was very ordinary. Once I put the passive crossovers in the trash and I ran each speaker to a separate channel on Network mode directly off the DEH80PRs everything went musically WoW!

The subwoofer I used was the TS-Z10LS4 which is 10" subwoofer that also a Hi Res certified subwoofer. I mounted the subwoofer in a premade subwoofer enclosure box in the trunk (the enclosure is made by HiFi Sound connection, which I bought from ebay). The enclosure is quite well made and it sits on the drivers side (for LHD cars) in the trunk. Now many have said online during my research, that a subwoofer in the boot of a Miata is useless as the cabin in sealed off to the trunk with the metal cover. Now there likely is truth to that statement, but I decided to take a punt as the Miata suffers terribly from a lack of low frequency response in its audio performance. The door speakers just cant deliver enough bass without distorting. From my experiences so far, I can safely say that the subwoofer performance I have now has far exceeded my expectations. You can hear all the low frequencies very nicely indeed. The sound is bassy without being thumpy...it provides enough bass to round out the music beautifully. I also lined the inside of the subwoofer box with sound absorbing self adhesive foam.

There is a slight reduction in trunk space by using this method but the enclosure sits quite nicely to the side and is not very intrusive at all. I designed the wiring in way that allows me to simply quickly unplug the box and remove it in under 20 secs if I needed the slightly greater trunk space.

I used WiredWorld Luna RCA interconnect cables (these are great!) to connect the Head unit to the amplifiers. These were 3m long cables and needed to be high quality to not get any losses or noise. The Luna cables are excellent for this and they are unidirectional, i.e. sound is better when wired the correct way.

For speaker cables I ran heavy gage OFC cables from the trunk to the doors. Hardest part was removing the wiring plug from the doors and body and drilling through the centre of it to pass each of the 2 speaker cables through it. I drilled a 10mm hole initially and then filed them out and eventually passed them through. Its tricky to do as there is only JUST enough room to put a drill through it and pass the cables through AND you can barely get your hand in the space to wiggle the connector out. Be prepared to be frustrated! This took a bit of time but the addition of proper thick gauge OFC cables means you get the best possible signal quality to the speakers.

I also finished off the speaker installs in the doors with a custom made MDF mounting adapter to the NB miata doors with their weird 8 inch hole setup, I then mounted the speakers to the mdf adapter. I also added Roadkill fast foam rings to seal it to the door trim and the MDF adapter.

I also used 4 AWG wire to power the amps with 60 A fuses on the positive lines.

Tuning the system once installed took a bit of time to get it just how I like it but..overall I am super happy with it now. It has a lot of power but with complete clarity.

So if you have a MX5/Miata I can strongly recommend this setup. Some key learnings were:

1) Subwoofer in trunk works great!
2) DEH8PRS Head unit is a gem, get one!
3) Speakers became alive once I went to full network mode setup
4) Amps have a lot of power for their size (a little bigger than your hand size..they are tiny but grunty!
5) Tuning it to your car and your liking will take a little bit of time...but well worth it
6) DEH80PRS interface and settings take a bit of getting used to, but will reward you if you persist
7) Use good RCA interconnects and speaker cables
8) Very little room behind head unit for 3 x pairs of RCA interconnects to fit. Head unit may not seat properly as a result..be prepared for mods :)
9) Crossover Settings Subwoofer LPF 125Hz, Mid HPF at 125Hz and Mid Low Pass at 4K, Hi over 4K
10) Solder a 15-22 microfarad 100V capacitor to the positive tweeter lead to avoid killing it with a bad frequency setting on the head unit...as it is not protected by a passive crossover in Network mode.

Hope that helps you get your Miata audio setup sounding sweet !

Cheers
Engineer