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NSX OEM Stereo System - 101

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28 January 2002
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Saskatchewan, Canada
Over time, there have been many threads about the NSX sound system; why isn't it working?; how can I fix it?; how can I upgrade it; etc. There is some content in the Wiki about it but some of it is dated and doesn't deal with some of the things that are available today so I had intended to write an updated Wiki article about it. However, since the Wiki is currently locked down, I thought I'd use the same approach as Yinzer did recently on his "buyer information" thread, and create a thread dedicated to the Stereo System. At least, that way I can add to it over time and point to other related threads. Disclaimer: I'm not a guru stereo installer but I did graduate as an electronics engineer a few decades ago; have gone through the amp refurb route; and relatively recently converted to an aftermarket setup, so I have some practical knowledge which I wrote about and which appeared in an issue of NSX Driver.
All comments welcome.

How It’s Designed

The NSX OEM stereo system was designed by BOSE and follows their standard design of a central head unit (which has no amplifier functions) and a number of individual speaker enclosures (which consist of a speaker and integrated amp). BOSE claims that the benefit of this design is that they can individually tune each speaker/amp combination to its location and the individual acoustics of the vehicle. The downside is that it is more difficult to enhance or replace with aftermarket components.

In the NSX, there are 3 speaker/amp enclosures and they are located in each door, and one in the passenger footwell where it is part of the subwoofer enclosure. There is actually a fourth speaker which centrally mounted between the seats near the armrest which serves as the only ‘rear’ speaker. It does not have an integrated amp but is driven by the amp in the subwoofer enclosure.

Note that the NSX stereo system only has two channels (L and R) and the amp in the subwoofer enclosure merges the two channels and sends the lower frequencies to the sub and the higher frequencies to the center channel. The speakers only have a single low impedance (one or two ohm) speaker (no separate tweeter/midrange) and it is presumed that any crossover circuitry is built into the associated amp. Because the speaker wiring only has to carry low level ‘line out’ signals, it is not large diameter and may not be capable of carrying the heavier currents in upgraded systems where the wiring must not only carry the larger voltages of speaker outputs but also the higher wattage levels of newer aftermarket amps. The BOSE design also means that the amps in the speaker enclosures need +12V/Gnd wiring (part of the NSX wiring harness) that isn’t required for centralized amp designs.

My Sound System Sounds Like Crap – What’s Wrong
In 90%+ of the cases, the problem is with some of the electronic components in the amps called capacitors which fail due to heat or other factors. If you were to open up an amp, there are many of these capacitors and failed ones typically bulge and/or leak out onto the circuit boards. The result is that they are no longer able to perform their electronic function and there is typically a loss of certain frequencies (maybe most) and/or a hissing noise or lack of volume. Note that in nearly all cases, the bad sound is due to the amps and not the speakers which rarely need replacing.
The good news is that there are a number of companies (including NSXPrime user BrianK) who can refurbish the amps by replacing the defective capacitors for about $100 each. This should restore the system to the same level of quality as it left the factory with. For some people this is sufficient but others feel the original sound volume/quality is inadequate by today’s standards and insist on upgrading or replacing it.
In a very, very small number of cases, the head unit can be the cause of problems and it can be rebuilt as well (it has circuits with capacitors too). Unfortunately, there is no reliable way of telling if the problems are with the head unit but from past history, you’re better off to first fix the door and sub amps first before sending the head unit out. You can use the head controls to throw all the audio to the left or right door to see if there’s a difference but after a while, we have all faced this problem and if you’re doing one amp, you might as well do them all. If there is absolutely no sound from the center speaker, the sub amp is probably toast. If you have issues with AM but not FM (or vice-versa), it’s probably an issue with the power antenna. If you have an OEM CD changer in the trunk but you can’t get any CD’s to play, that’s a whole other topic for discussion.
If you do plan to send out the amps for refurbishing, there are good instructions on how to do this in the NSX Wiki at: http://nsxprime.com/wiki/Bose_RR

What Are My Upgrade Options?
This depends on why you’re wanting to upgrade. The reasons are typically as follows:
1. Keep the stock head unit but add an iPod/MP3 player interface
2. Keep the stock head unit but migrate to a better, more reliable amp
3. Replace the head unit with a double DIN one with video/GPS/etc and integrated amp

1. Keep the stock head unit but add an iPod/MP3 player interface
If you have an existing OEM CD changer in your trunk, this is a great solution whether it is still working or not. The original changer did not support CDs with MP3 on them so a number of people successfully upgraded to Alpine S634 models which served the purpose for the times but moving to an iPod/iPhone/MP3 player interface is the way to go today. Science of Speed sells one that plugs into the existing CD changer wiring and provides a connector that you can install in the armrest, ashtray location, or wherever. This unit allows some minor control via the head unit but playlists, folder display, etc has to be done by the iPod/iPhone/MP3 Player.

2. Keep the stock head unit but migrate to a better, more reliable amp
This option is going to cost more (probably $500+) and will require more DIY effort because you need to replace the distributed amp BOSE design with a central amp. In addition to the cost, there is the issue of where to put the amp, and the associated issues of how to provide sufficient power to it; how/where to best run audio and speaker cabling; etc.

Although people have installed amps in the glove compartment (loss of storage space and heat issues) and in the trunk (more difficult and longer audio cable and speaker wire runs but close to power and ground connections), the easiest place is probably behind the drivers seat if you can stand to lose a bit of legroom. Behind the passenger seat might also be a location but the passenger legroom is already somewhat compromised because of the sub in the footwell. With the introduction of much smaller Class D amps, people have also suggested locating them under the seats but this space is extremely limited and I’m not aware of anyone actually doing this.

One of the benefits of locating the amp behind the drives seat is that it is not very difficult to run the amp power cable through a grommet in the firewall behind the driver’s left shoulder and into the engine compartment where it can be easily connected to the electrical block where you would also jump start the car. There are also a number of convenient locations to ground the amp on the inside of the firewall where most of the cars other electrical components are installed. This results in very short runs for both the power and ground connections as well as all of the amp audio connections which are easily run through the center console to the head unit and to the speakers.

Note that Science of Speed also sells wiring harnesses for both OEM and non-OEM applications which can simplify the wiring. This allows you to access the Left and Right channel line-out connections from the head unit and use them as line-in inputs to the new amp. The new amp speaker outputs can then be sent back to the wiring harness where they would travel over OEM wiring to the doors. However, because these are speaker-level, not line-level, you have to open up the door enclosures, bypass the BOSE amps, and connect directly to the speakers which is relatively easy to do. Alternatively, you can just replace the existing speakers with newer better ones. SOS sells replacement mounting kits which can be substituted for the OEM enclosures.

Re-working the sub can be a similar process. You could keep the existing BOSE amp/sub combo but most people will want to have the new amp drive it as well. Although the sub is small, it generates decent base if driven by a good amp try it before spending money on a replacement. You can always replace it easily later if you use the new amp to drive it now. In order to do so, you will need an amp with more than just the 2 channels for the doors but you can easily find 4 and 5 channel models where the extra channel(s) can be bridged or directly drive a sub. Ideally, they will also allow the option to internally bridge the L/R inputs to the extra amps but that’s not difficult to do if they don’t. As with the door enclosures, you’ll need to bypass the BOSE amp.

One issue with this approach is that, as was mentioned earlier, the OEM wiring to the doors is limited in it’s power handling capabilities so don’t try to put a gazillion watts through them. Also, if you do use the existing BOSE speakers, remember that they are very low impedence so turn the amp volume WAY down before testing them otherwise you may be replacing them soon. I also used the OEM sub but instead of using the factory wiring, I ran heavier speaker cable to the amp in case I choose to replace the sub in the future.

3. Replace the head unit with a double DIN one with video/GPS/etc and integrated amp
If you choose to go this way, the electronics piece may be simpler if the new head unit contains an integrated amplifier function. You’ll have the problem of where to get adequate power but you won’t have worry about where to put it and the cable runs will be much shorter. However, you will still need to bypass the BOSE amps in the doors and at the sub and have some of the same issues as in #2. The other more significant issue is in getting an acceptable double DIN replacement for the center console and getting the installation to look good and not have a lot of glare. Also, have a close look at the existing console design which narrows as it goes back so something you think may work on the face of the console may not have enough clearance for the deeper part of the unit.

Other Considerations
This is the first version of this thread and doesn’t yet include some other issues people may have with the existing OEM sound system such as:
Options to connect various phones/players
Here's the 'condensed version' (but still huge thread) on iPod/iPad adapters: http://www.nsxprime.com/forum/showt...for-your-oem-NSX-Stereo-the-condensed-version

Here's one for Android: http://www.nsxprime.com/forum/showthread.php/164577-Android-Phone-to-OEM-Stereo

Here's one for Bluetooth: http://www.nsxprime.com/forum/showt...uetooth-audio-gadget-for-those-with-mp3-jacks

Here's one for AUX input: http://www.nsxprime.com/forum/showthread.php/142287-AUX-Input-for-OEM-Acura-Bose-Radio

• Ability to add equalizer and/or crossovers
• Sub upgrade options

• Other sound system issues such as:
o Display orange tint/brightness issues
o Antenna issues
o Loose/worn head unit knobs
• Soundproofing - try this thread on Dynamat: http://www.nsxprime.com/forum/showthread.php/151989-please-share-dynamat-door-install-pics
• OEM head unit connectors

Here's probably the original "Double Din" thread - lots of pages: http://www.nsxprime.com/forum/showthread.php/64651-Double-DIN-video-head-unit-thread

Builds/Inspiration:
1. http://www.nsxprime.com/forum/showthread.php/161234-check-out-this-center-dash
2. http://www.nsxprime.com/forum/showthread.php/161990-Pioneer-in-dash-double-dins
3. http://www.nsxprime.com/forum/showt...tion-amp-Double-Din-Modification-Lots-of-pics!

Center Console Replacement Options (not exhaustive - just some links I've squirrelled away)
:
1. http://www.nsxprime.com/forum/showthread.php/173522-Carbon-Fiber-Center-Console
2. http://www.nsxprime.com/forum/showthread.php/177941-Just-a-tease-Full-carbon-console-double-din
 
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Great thread. Are questions allowed? Or is this just an information only thread?

If questions are allowed, then I have one for you guys. When the system sounds like crap, is there a definitive way to tell if it's the amp(s) or the head unit before removal of anything? I'd hate to rip out my amps, send them in, only to find out it's really the head unit. What's also interesting is that based on threads I've read on this subject, crappy sound pointed to a malfunctioning head unit first.

What's the general consensus when the stereo sounds good for the day after being reconnected to the battery, but the next day and the day after that, the sound quality continues to deteriorate. Then, imagine disconnecting the battery again for those days I don't drive the NSX...but when I connect the battery again, the process starts over where the quality goes from very good to bad.
 
At some point could you touch on the issue of the changer not working properly? Mine will play some of the cds and skips over others. Thanks Ian.
 
Actually the NSx radio is 4 channel but the other 2 go to the sub. I know this because before I got a new OEM radio one of my channels were bad, so I swapped the rear for the front so I could have sound again.
this was only a temp solution but it did work. behind the radio is the location I used to just tap the other wire

other than that your write up is dead on.
 
Actually the NSx radio is 4 channel but the other 2 go to the sub. I know this because before I got a new OEM radio one of my channels were bad, so I swapped the rear for the front so I could have sound again.
this was only a temp solution but it did work. behind the radio is the location I used to just tap the other wire.
Shawn, I've gone over the wiring diagrams and there are 2 channels that go to the sub amp but there is no mention of whether they are separate from the door channels or not. The fact that the amp wiring is separate from the door wiring justifies the use of separate pins on the head connector .. but it has always bothered me that they run two channels to the sub amp. The sub amp clearly needs to merge the channels since there is only one center speaker and one sub. But it seems like an odd design to me to merge the channels in the sub amp when they could just as easily merge the channels in the head unit and just use two wires to the sub amp instead of 4. I'm not convinced that the fact you fixed your problem by swapping output pins proves that they're separate .. there could have been a pin or internal connection problem ... but if the channels are separate, it would make sense. However, in the central amp conversion scenario, it would be easy to run the sub amp channels from the head unit to the new sub amp instead of just bridging the door amp inputs to the sub amp inputs.

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Great thread. Are questions allowed? Or is this just an information only thread?
All questions/comments are welcome. If they result in any corrections/additions to the above, I will edit it so it improves over time.

When the system sounds like crap, is there a definitive way to tell if it's the amp(s) or the head unit before removal of anything? .. What's also interesting is that based on threads I've read on this subject, crappy sound pointed to a malfunctioning head unit first.
As I tried to convey above, there is little you can do to definitively prove whether it's head unit or door without taking something apart, although as I have suggested, you might be able to tell if one door speaker is bad and the other is fine. But you are dead wrong that head unit is the highest probability. It's the reverse .. probably 90%+ of the time it's the door amps. Briank repairs both and I'm sure he can confirm that he sees way more door amp/sub amp units than head units.

What's the general consensus when the stereo sounds good for the day after being reconnected to the battery, but the next day and the day after that, the sound quality continues to deteriorate. Then, imagine disconnecting the battery again for those days I don't drive the NSX...but when I connect the battery again, the process starts over where the quality goes from very good to bad.
Unfortunately, electrolytic capacitors don't just quit working .. they typically bulge and slowly leak their internal chemicals and charge carrying abilities over time. This results in a gradual loss of frequencies over time until you don't hear anything (other than maybe a hiss). The leaked chemicals also usually end up on the circuit board and can thus affect the workings of the amp circuits in a gazillion unpredictable ways, none of which are good.

I can't think of a rational explanation for why your loss of quality would have anything to do with disconnecting the battery. When you turn off the car, you're essentially disconnecting the sound system from the battery anyway .. unless someone has messed with the wiring or if the amp relay is stuck. The amps are connected to +12/Bat via the amp relay but only on command from the head unit. I could believe that the sound deteriorates after you start the car and drive around for a while, which is likely caused by the capacitors heating up and changing their internal electrical properties. But the battery disconnect makes no sense.

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At some point could you touch on the issue of the changer not working properly? Mine will play some of the cds and skips over others. Thanks Ian.
I'll add it to the list .. not sure I have any quick suggestions though other than moving the CDs around in the changer to see if it follows the CD or not. I seem to recall that there was an adjustment on the carrier to make it less susceptible to vibration but I can't remember if that was on the OEM unit or the S634 that I replaced it with. As I mentioned in the piece, if you have the OEM changer, it only played standard CDs .. I'm not even sure it would play ones you burned .. or ones burned on rewritable media...and would definitely not do ones with .mp3 files ... they had to be .cda files.

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At some point could you touch on the issue of the changer not working properly? Mine will play some of the cds and skips over others. Thanks Ian.
In addition to my earlier comments, you might try the suggestions under "Adjusting The CD Player" on this Wiki page: http://nsxprime.com/wiki/Speakers
 
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Thanks for putting this together!

I recently took out my Bose amplifiers to repair them but had no luck. It's possible that I simply did the repair wrong but I noticed that one of the caps had exploded and the Bose IC was burnt/melted before the repair. You mentioned that the caps gradually deteriorate until no longer working but I'm wondering if there's potentially one step beyond that. If the amps are run continuously after deteriorating could this cause the larger failure I saw and damage the IC? If so then that might be decent incentive to have the boards repaired when they fail rather than delaying things.
 
well I did what I did and it worked LOL I will go look at an old radio I have anyway just to verify

if you send you amps to bose they only fix the popped resistors not the other ones that will pop eventually due to age. ( bose make me :mad: )

send to BRIANK he replaces all of them.
 
I recently took out my Bose amplifiers to repair them but had no luck. It's possible that I simply did the repair wrong but I noticed that one of the caps had exploded and the Bose IC was burnt/melted before the repair. You mentioned that the caps gradually deteriorate until no longer working but I'm wondering if there's potentially one step beyond that. If the amps are run continuously after deteriorating could this cause the larger failure I saw and damage the IC? If so then that might be decent incentive to have the boards repaired when they fail rather than delaying things.
Unfortunately, there's no way to predict how or when a capacitor will fail .. and in your case, I suspect the way it failed may have caused an internal short and, as a result, some overheating. Briank could comment on how common this is with the rebuilds he sees but I believe that damage to the circuit board is pretty rare. I don't know if you tried to replace them yourself or not but unless you have some soldering skills; a desoldering tool; and the correct heat soldering iron, you can easily cause additional problems. Some circuit boards have circuit patterns on both side and you need to make sure that the solder makes a connection on both sides. And since you can't really visually tell if a capacitor has started to fail or not, it's best to replace all of them at the same time.
 
I pretty much tried everything you touched on Ian. Made sure all CDs were original, not burned. (that's illegal you know) Moved them around, tried different ones etc. The discs that won't play are always in the same slots. It's not a vibration issue as the problem exists if the car is moving or stationary.
 
All the amps fail and the capacitors going bad is the most common cause. The sooner I get them the less work it takes. The capacitor leakage does makes a mess of the circuit board, eats through the traces and can also cause short circuits that will burn up components.
 
how can you tell if the center speaker is working? When i hold my ear near it i don't think i'm hearing anything,but i can't tell if the front speakers are drowning it out. it would help if there was a front/rear fader,but there isn't, which i guess makes sense since the center one is just kind of a fill-in.
 
If you can't hear it with your ear right by it its not working. Stick your head in the passenger foot well and see if the foot well speaker is working if its not that is your problems if it is working then the center speaker is more then likely unplugged.
 
If you can't hear it with your ear right by it its not working. Stick your head in the passenger foot well and see if the foot well speaker is working if its not that is your problems if it is working then the center speaker is more then likely unplugged.

thank brian,if it turns out it's unplugged,how do you plug it in?
 
Thanks for the detailed response Ian, much appreciated.

One source where I read what I mentioned, is here in the NSX section on Willman's Electronics website:
"Know that on 1991 - 1995 vehicles, your static and popping may be coming from the stereo head unit needing repaired. If you know that you have good amps and still have a sound problem then it will most likely be the stereo. If that is the case then the best thing to do is unplug the battery until you get a chance to remove the stereo. This removes the constant power (even with car ignition off) which will continue to short out the radio. These can get so bad that they aren't repairable so get the stereo out as soon as you can to improve the chances of the stereo being repairable."
 
All the amps fail and the capacitors going bad is the most common cause. The sooner I get them the less work it takes. The capacitor leakage does makes a mess of the circuit board, eats through the traces and can also cause short circuits that will burn up components.
Brian .. tks for chiming in. Can you comment, based on your repair experience, on how common head unit failure is comparable to amp failures .. ie. is it close to the 90% amps/10% head unit estimate I put out?

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The plug is at the speaker so you will have to take some stuff apart and get the pod off to check and connect it.
To expand on Brian's "take some stuff apart" comment .. the interior trim behind the seats has 4 pieces as I recall. The first one you'll want to take off is the top piece which runs the width of the car. IIRC, you pull toward you on the bottom in a couple of places to free it up. Then the lower section is three pieces .. one behind each seat which have to come off first before you can get to the center section which has the center speaker. I think I also had to remove the armrest/storage before I could get to one of the screws for the center section. Not terribly difficult .. but not everyone's cup of tee either.

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I've updated the original thread comments to include some links at the end that might be useful. They're not exhaustive .. it you have others, please share and I will add them to the first post.
 
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With an aftermarket head unit (w/built in amp), do you need to bypass the Bose sub amp to avoid frying it? This is assuming that the door speakers are replacements being driven by just the head unit.
 
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I searched the site a bit. Just wondering if it is possible to add just a sub amp and upgraded sub without too much hassle. I have an 8" XMAX phoenix gold sub and a phoenix gold titanium 400.2 collecting dust that I would like to add to the factory system and remove the factory sub and enclosure. I want to avoid hacking into the unmolested system if possible. Is this possible and still have the centre speaker still work properly
 
I searched the site a bit. Just wondering if it is possible to add just a sub amp and upgraded sub without too much hassle. I have an 8" XMAX phoenix gold sub and a phoenix gold titanium 400.2 collecting dust that I would like to add to the factory system and remove the factory sub and enclosure. I want to avoid hacking into the unmolested system if possible. Is this possible and still have the centre speaker still work properly

You can do anything you want but the stock sub is part of the foot well structure so removing it leaves the carpet unsupported and so you will have to restructure and modify to fit an after market speaker and find a place to mount the amp. The center speaker gets its signal from the stock amp so I am not sure how well it will work with a aftermarket amp. Also the stock amp takes both the left and right channels as input so I am not sure how you will do that with an aftermarket amp.
 
the stock sub is part of the foot well structure so removing it leaves the carpet unsupported
T_22* .. further to Brian's comment, there have been a few people on Prime who have offered alternate enclosures for larger subs .. but be careful because some ended up being slightly larger than stock and reduced the passenger footwell space. I believe that zetoolman built some ... and maybe angus as well. Here's a thread that might help: http://www.nsxprime.com/forum/showthread.php/161521-Sub-woofer-enclosure
 
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