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What is the OEM CD Changer?
Can I Use A Regular Alpine CD Changer?Yes, but you must use an adapter cable for it to sound right. It is physically possible to plug the Alpine units directly into the wiring since the are both standard DIN adapters, but there is a change in the wiring (pins 2 and 4 are switched) which causes the sound to be out of phase if you simply plug the Alpine unit unto the existing cabling. A common adapter cable is Precision Interface Electronics (PIE), part #ACUALP, available at any major car stereo dealer which handles Alpine equipment. For more information on the wiring change, see the DIY - Sound System section of the FAQ. [SS - 99/9/13] This switching of wires was not a mistake by Honda but rather an intentional alteration in an attempt to keep out aftermarketers. Same goes for the non-din-standard stereo unit itself. Pretty much all car manufacturers do this.
[BZA - 99/9/13] I picked [the PEI adapter cable] up at Circuit City for $29.95
What About Installation?The factory Acura CD changer comes with a mounting kit that allows it to tilt out for loading discs and then fold back into the corner on the side of the trunk. Most aftermarket changes don't come with this bracket. You simply need to drill a few holes in the mounting bracket to use it with any of the newer Alpine changers. Most people just use a fixed mounting position, but the bracket is cooler. See the DIY / Sound System section for more installation suggestions and tips.
Which CD Changers Are OEM Compatible?[RL, DS] The factory stereo is Bose AM/FM stereo cassette with an optional trunk-mounted CD changer. The car is pre-wired for the changer. The OEM CD changer is an Alpine unit relabeled to say NSX and costing over $1,000 from Acura. Many other Apline units can be used with the factory system, all for less than half the price and often with better features. Acura used the Alpine 5960 as the OEM mechanism for its changers from 1992-1994. The Alpine S600 was used in 1995, and the promptly discontinued and replaced with the Alpine S601. (The only real difference between these mechanisms is spin rate and disc transfer rate.) In accordance with an agreement with other auto manufacturers that get a thrill out of charging $1000 for a $350 CD changer, Alpine changed the DIN connector on the OEM unit from the factory units. Solution is simple... from your car-audio shop of choice, purchase a DIN cable adapter, and you're done. [SS - 99/9/13] Any M-Bus 6 disc Alpine can be controlled by the NSX head unit. The dual mode Ai-Net/MBus CHA-S6x4 series are controllable, but need to be used in M-Bus mode - there is a switch on the unit. Also needed for the CHA-S6x4 series is the Ai-Net to M-Bus Adaptor cable $10.
Model numbers known to work include:
[BZA - 99/9/12] I purchased [an Alpine CHM-S620] today and installed it in my '91. I paid $254.99 at Circuit City. I purchased the M-bus version of the CHM-620 so I did not need another cable. BTW: The Acura OEM CD magazine is not compatible with the Alpine CHM-620 magazines.
[DJS] Acura used the Alpine 5960 as the OEM mechanism for its changers from 1992-1994. The Alpine S600 was used in 1995, and the promptly discontinued and replaced with the Alpine S601. (The only real difference between these mechanisms is spin rate and disc transfer rate.) In accordance with an agreement with other auto manufacturers that get a thrill out of charging $1000 for a $350 CD changer, Alpine changed the DIN connector on the OEM unit from the factory units. Solution is simple... from your car-audio shop of choice, purchase a DIN cable adapter, and you're done.
[TM] Acura were bastards on the 97 models, and I had to go to a FM CD changer from
Clarion (it was cheaper than the Alpine, but seemed identical in quality, as the line
adapter for 97+ NSX was quoted to me at around $400, whereas older cars just needed the
cheap DIN adapter. In retrospect I should have got the factory CD changer. I always get
[SS - 99/9/13] Any M-Bus 6 disc Alpine is controllable by the NSX head. The dual mode Ai-Net/MBus CHA-S6x4 series are controllable, but need to be used in M-Bus mode, there is a switch on the unit. Also needed for the CHA-S6x4 series is the Ai-Net to M-Bus Adaptor cable $10.
[BZA - 99/9/13] I would suggest that the following be added to the FAQ: I, and at least one other NSXer, assumed that all the discussions about DIN adapters for CD changers had to do with the physical arrangements of the pins. More explicitly, we thought it was something like the male end has a different number and/or arrangement of pins than the corresponding female connector on the factory CD changer wiring harness. When the Alpine CHM-620 plugged right in, we assumed we were home free without the adapter. Wrong! You need a part from Peripheral Electronics Inc. (PEI), part #ACUALP. I picked it up at Circuit City for $29.95. This corrects the speakers out-of-phase situation (the real DIN adapter problem). The big difference is apparent in the low-end. I did an A-B test with Dream Theater's Lines in the Sand. The difference in the bass frequencies is night and day. I purchased the M-bus version of the CHM-620 so I did not need another cable. BTW: The Acura OEM CD magazine is not compatible with the Alpine CHM-620 magazines.
[CWI - 99/8/13] Recounting from personal experience, the DIN cable runs from the back of the head unit to through the middle console, through the firewall, and through the left side of the trunk eventually meeting the changer in the right side of the trunk. The pin is switched within this wire. If you are mouting the changer in the glovebox (like I did) it is easiest to remove the stock DIN cable, and replace it with the one supplied with the unit. No fuss with buying an adaptor.
[JN - 2000/3/4] Installed in a '99 car. A little under two hours. A little fiddling to make the Alpine bracket match the factory bracket, but otherwise plug and play.: Acura bracket $90
[TD - 2000/3/18] After the run around by some uninformed Circuit City/Good Guys employees I finally got my changer [for a '99 NSX]. Pretty straightforward installation. I decided not to drill any holes, or mess with the bracket and I attached it with velcro to the floor of the trunk. It is easily removable if you need more cargo space and the discs do not skip, not even around a turn at high gs. It works perfectly. Here is what I got: Alpine CHM-S620 CD Changer $249 both available at The Good Guys. Installation of course was free.
What Is The Frequency Response Of The OEM System?
I made some measurements that may be of interest to anyone making after-market audio enhancements to his NSX. In summary, the head unit supplied with the NSX provides what is commonly known as "loudness compensation." This is a bass boost that gets progressively stronger as the volume is turned *down*. In home audio the conventional "reason" (excuse?) for this is compensation for the Fletcher-Munson curve, which is a measurement of human hearing sensitivity that shows sensitivity to bass falling off as volume decreases. This "feature" is defeatable on any reasonably high-quality home audio unit. In an automobile there may be an additional motive, namely that the spectrum of background (mostly road) noise in the car is dominated by low frequency energy. Thus, if the stereo volume is comparable to or slightly above the background noise you may need bass boost to provide subjectively flat response in the presence of large amounts of low-frequency noise. On the other hand, when the volume is *way* up, such that the signal to background-noise ratio becomes significant, the designers may have felt the bass boost was not needed. Or they simply observed that the power-amp/speaker system wouldn't be able to provide it without distortion. Who knows? Disregarding for the moment whether or not this compensation is a good thing, here is the frequency response of the CD-player/head unit output (i.e. before the power amps, which may contain equalization of their own). Measurements are dBV (i.e. decibels re 1 VAC). All measurements taken using Denon Audio Technical CD, 38C39-7147, and a Ballantine VTVM known to be flat over the audio frequency range, and monitored on an oscilloscope. The column headings are the volume control position as "o'clock" i.e. 9:00
means the white tick mark is straight to the left, and 12:00 means it's straight up.
Boost@40Hz: 14 14.5 6 1 So, what we have here is a head unit that adds substantial but variable bass boost until you get the volume *really* cranked up. The frequency of peak compensation appears to have a period of about 35 mS, i.e. ~30 Hz. (I have no easy way to measure that with a frequency counter). A prize to the first person who tells me how to disable this loudness compensation inside the head unit. This is not a quiz; I don't know the answer, but I wish I did. The first idea that springs to my mind is assume that the volume control has a "third" (and/or fourth) variable resistance that controls the "loudness compensation", find it, and substitute an appropriate fixed resistance, i.e. that which corresponds to a "high volume" setting. For this we need to disassemble the head unit, which I have done partially in the past. But not yet to the point where I exposed the volume control potentiometer terminals. Hmmmm. [TM] Short of actually disabling this loudness compensation "feature," you can install aftermarket speakers, amp and crossover with level. Set crossover level for low input sensitivity. This causes you to turn the volume control to a higher level (eg 12-1 o'clock) where there is less loudness compensation.
Bass[TME] For bass, I used Aura Bass Shakers mounted under each seat. These things are absolutely wicked and don't take up any space in the NSX (yay!) They're sort of like the center part of a speaker without the cone and they're attached to the bottom of the seats. I had the car a few days before it got balanced and the bass was incredible, though I eventually had it toned down to normal levels. It still kicks on bass-heavy music though.
Sound ProofingDynamatYou can buy this stuff very cheaply as peel and stick waterproofing /roofing membrane for approx $50 for a 100' roll (sizes may vary) This is what dynamat was/is before relabelling it also comes in several thicknesses and densities , so find a roofing materials wholesaler and ask away. Be advised however that this will NOT work as well as the adverts claim.
Ice Guard is a roofing material to prevent frost buildup. It happens to be much the same construction as Dynamat at a fraction of the cost, and supposedly works just as well. Contact a roofing contractor for pricing and supply (in warmer climates, they've probably never heard of it). |
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