Notes on Mike Walsted's Miata's Sound System

This Miata came equipped with the Bose Sound system, consisting of head unit, cassette player, component speakers, and an amplifier. (Or is it amplifiers?) In the stock configuration, eight inch speakers are located in the lower door panels, with tweeters in the upper part of the door panels. Unfortunately, it turns out that my Miata's Bose Audio system has incredibly lousy sound quality. After reading a lot on the web, especially at , I realized that my lousy sounding system was not an exception, and began to research my options for better sound. As the parts of the Bose system are not real compatible with standard stereo components, it is usually recommended that the whole system be replaced at the same time if any part is replaced, with a few exceptions. This particular task is common among Miata owners, and is generally referred to as a Bosectomy, not to be confused with a stereotomy .

"How bad was the OEM BOSE system," you may ask? Well, I am by no means an audiophile or expert on sound, and have spent a lot of years working in and out of buildings relatively close to operating jet engines, but to me, things sounded different with the Bose system. Some people may like these differences, (such as music missing the midrange, harmonics, overtones, light harmonies, and such.) Other folks may say that high quality sound cannot be expected from a convertible, and it isn't the fault of the stereo. I disagree. To me, the stereo system didn't even sound good parked with the top up and engine off, and I doubt that it would to many others, either. For a couple of examples, the saxophone on Sade's Love Deluxe was barely audible most of the time with the Bose system, and often wasn't audible at all. Clare Torry's vocals sounded like she was singing in a different room with the door closed. I now know what Vanessa Carlton's A Thousand Miles sounds like without the piano. I have installed the Pioneer DEH-2800 in a friend's Miata with appropriate speakers, (just under $200 out the door for the stereo and speakers,) and it sounded good. Not audiophile good, but all of the notes were there and there wasn't a lot of unwanted noise. So, most of the sound quality deficiency was due to the sound system, not the car. Again, I am not an audiophile. I don't expect to be able to determine precisely where the guitar player was standing on stage and which string and fret combination was used for a given note. But I do expect to be able to hear that a guitar player showed up and is playing a guitar in the same auditorium or recording studio as the rest of the band, and be able to determine his relative location.

The age of the system may also have had a lot to do with the sound quality, as it has obviously affected the sound system's mechanical operation. For instance, when I first got the car, the head unit wouldn't play CDs. Then, after a lot of attempts, it got to the point where it would play CDs if I used a screwdriver to start the CD spinning, but the music sounded like it was coming from a stretched cassette tape. After many CD insertions and removals, the system cleared itself, and the CD player began operating without the stretched cassette sound. It still did not operate normally, however. The system would not read CDs when it is cold, and would skip very frequently. The AM radio would often switch to static for a few seconds, as if there is a loose internal wire.

Due to the overall deficiencies of the system, I did a little research on ways to replace the whole system at the same time for minimal cost, yet end up with a system that sounds pretty decent. At first, as a patch, I replaced the in-door tweeters with AuraSound extended range two-inch speakers, and this made a very noticeable improvement in the sound. Many of the previously missing notes became audible, although the weaknesses of the head unit (and a couple of local FM stations,) became more obvious, since the weaknesses were not masked as much by the speaker weaknesses. As the AuraSound speakers are performing better than the Bose, and are doing a satisfactory job, I left the AuraSound units in the tweeter spots, and put a set of speakers in the large openings when I did the Bosectomy. Although I could hear sound coming from the stock tweeters, they may have been damaged, and that may have been a factor in the lack of quality sound in the car before their replacement. Unfortunately, my soldering skills leave a lot to be desired, and I tried replacing the Aurasounds with these Peerless speakers, but broke one of the Peerless speakers in the process not realizing that they are a bit too deep to fit easily when I bought them. These Peerless speakers have received generally positive reviews, although at least one person says they sound kind of "tinny" in the Miata. The Peerless speakers I ended up buying have slightly better specifications.

After a lot of research, I chose a Kenwood Excelon KDC-X891 for the head unit for the Bosectomy, based on my desires for a rear USB input, RDS, and separate amp and antenna power leads so I can more likely avoid another $40 antenna mast replacement cost. The local smooth jazz station is available via HDRadio only, but no head unit offered integrated HDRadio and separate antenna and amplifier power controls. The USB input allows me to listen to music stored on a flash drive or USB MP3 player, which is helpful on my daily commute and on long trips, and my daughter can listen to her music if she remembers to bring her flash drive along. As the USB port is in the back, a hidden cable was ran to the center console, allowing a flash drive to be connected and stored out-of-sight. An auxillary input serves a similar purpose for a wider range of devices, but won't be able to supply power.

While researching stereos, I did learn a few things that others may find helpful:

I looked at a lot of speakers, and as at least one person reported good results with Lanzar VX830 speakers, that is the direction I took. (DLS Performance 428 speakers and Blaupunkt GTx803 speakers also appear to be a drop-in fit for those willing to spend more.) I was originally leaning toward replacing the stock Bose 8 inch speakers with Pioneer TS-MR2040 8-inch marine speakers, and leave the AuraSound extended range two-inch speakers in the tweeter openings, connecting each of the speakers to a separate channel. This combination of speakers would have covered my hearing range well, and handle the power levels that I expected, at a reasonable price. Depending upon which web site is referenced, the Pioneer speakers require a 7 1/4" to 7 3/8" cut-out, but the cut-out in my doors seems to be 7 3/8" high and only 7 1/8" wide. This could have been worked around. Unfortunately, at the time I was unable to verify that the bolt spacing was correct. I later located the manual online, and now wonder if the grills can be easily separated from the speaker. I would really have preferred the Kenwood KFC-2089IE speakers, but I could not find a local source. Consequently, the Jensen 368s were installed at first, and the Lanzar VX830 speakers were installed when they arrived.

As far as the installation of other speakers, speaker sizes other than 8 inch round would require an adapter plate to fit. Madisound has several speakers that would work in the tweeter opening, if others are interested. Most of them have a relatively low sensitivity, however. If it weren't for their depth, the Peerless 830983 2" Full Range 4 ohm speakers might have been the best substitute for the Bose tweeters, especially since the quick-disconnects would make them easier to install than the AuraSound speakers that are currently installed, and to me, sound slightly better. Madisound now carries a version of the Aurasound speakers with quick disconnects, and they may be the easiest solution, since their size allows them to easily fit in place of the original tweeters, while the Peerless speakers are a bit too deep to fit easily.

When I was younger, I had the opportunity to find out what frequencies I can hear. The lowest end of my hearing is around 50Hz, and the upper end is around 16kHz, so I prefer speakers that cover that entire range with excess on both ends. The set of Jensen JPS368 speakers that was sitting on a shelf in my garage has a bottom frequency range near my hearing threshold, which may explain why I was not real happy with the bass response from these speakers, and thus why they were not used in the car for very long.

Why did I consider the sound system upgrade important enough to spend hours researching systems and writing and re-writing a web page about my thoughts instead of just buying and installing the appropriate system and being done with it? First, I like to document my work so that others can learn from my mistakes. Additionally, I spend about 35 hours each month in my car driving to and from work. I don't plan on doing multiple stereo installations (like I did on my last vehicle), just a possible speaker upgrade if I ever find eight-inch marine speakers I like better, and replacing the speakers in the tweeter openings again since my last soldering attempt did not bode well for the left speaker. Listening to traffic reports during rush hours allowed me to minimize the time I spend sitting in traffic, keeping the number of hours I spent in the car closer to 35 than to 45 or 55. Listening to decent music when I am not driving during rush hour is relaxing. If anyone in the Dallas/Fort Worth area implements RDS Traffic Announcements, I'll be able to listen to relaxing music and get the traffic information when something occurs, making my commute that much better. (It looks like Clear Channel is already offering a subscription RDS traffic service using Audiovox TMC, which seems to be aimed more toward GPS units than car stereos).

After a year and a half with the Kenwood / Lanzar set-up, I stumbled across another set up which looks like it may work a lot better for those who would prefer a double-din head unit and better known speakers. Midwest Electronics now has the Blaupunkt New Jersey MP68, a double-din head unit in black with many desireable features, including RDS, Bluetooth, and speed-dependent volume control. They also carry Blaupunkt GTx803 speakers, which should be a direct fit in NB Miatas. I have no direct experience with Blaupunkt components or Midwest Electronics, but this may be the ideal one-stop solution for those considering a bosectomy and desiring USB and AUX ports on the front of the unit.

For those considering purchasing an RDS-TA/TP capable head unit for use in the Dallas/Fort Worth Metroplex, as far as I can tell, nobody in the Dallas/Fort Worth area supports RDS traffic announcements/information, or emergency information. If I am incorrect, please email me and I will update this page.

The lack of RDS/TA in my area has me contemplating receiver capable of utilizing RDS/TMC data. If my work schedule changes in such a way that traffic information becomes more important, I will probably eventually install a Kenwood DNX-5140 in-dash navigation double-din head unit and GTM10 Traffic Receiver. The DNX-5140 supports WAV files, has a rear USB input, and other features I feel are important that many head units lack. The main drawback to the installation of a DNX-5140 is the cost.

Feel free to email me at if you have any suggestions.