Good sounding audio in a 993 Installation, Sub Woofers vs DSP, adding an Aux. Input and aftermarket radio head options.

Replace the car audio speakers - If they have not already been replaced. The 993 audio systems in these cars are now over 25 years old.

Aftermarket Coaxial speakers.

By now, speaker cones are dried out, have lost their rigidity, and can even exhibit rips. The exact vintage replacement speaker components are readily available through the Porsche dealer parts network; however, in my opinion, a refresh with even low-cost modern aftermarket components is an improvement over the original stock drivers.

To avoid cutting the speaker wires in the door, a wiring harness plug pigtail is available from Crutchfield:

Speaker wiring harness plug 

For the non-premium system, a direct door speaker replacement involves just four screws. If your original speakers are just attached to the door card so the mounting screws do not go all the way through to the inner door steel panel, consider drilling new mounting holes in the steel and using some sheet metal screws to mount the replacement speakers. This will avoid vibration sounds and also make removing the speakers or door cards when servicing the door easier going forward. Also, depending on the shape of the speaker frame involved, some will allow you to use a slightly larger speaker in the door, potentially improving low-frequency response. Using an extension ring, available in various depths, when mounting the speaker, can also allow for the use of a larger speaker.

Here is a pin-out list for radio head connections to the car's wiring harness.

For the Premium system, as in my car, I jettisoned the bass reflex boxes

Door Speaker Bass Reflex Box

under the door speaker covers and initially replaced them with 5-1/2” two-way aftermarket speakers in the door card speaker holes in conjunction with one-inch deep extension rings. The extension rings move the speaker out, closer to the grill on the original carpeted OEM speaker cover.

Speaker
Extension Rings

I would not recommend the least expensive aftermarket speakers, as they use a simple capacitor as a crossover and can sound rather harsh. The difference in cost between these and slightly better ones can be as little as $30. An alternative is to just install a woofer in the door and use it in conjunction with an aftermarket hi-low signal split passive cross-over and a new tweeter up by the window in the existing tweeter housing position or behind the carpeted premium sound door speaker covers. I found reusing the existing tweeter to be a bit harsh-sounding. In my car, I covered up the new stuff with the existing padded OEM Premium speaker cover. It looks stock and sounds much better.

Original OEM Premium Door Speaker Cover

For the rear original Premium Sound speakers, getting an original raw speaker component is done through a dealer. Online Sunnyside Porsche Parts seems to have good pricing on original speaker replacement parts with the original driver's attachment holes that line up with the original housing frame. I chose to instead replace the internal rear raw speaker drivers with 

generic aftermarket 4” coaxial ones and disconnected 

the existing tweeters. I had to drill speaker mounting

Original rear deck Hi-Fi option speakers.

holes in the existing rectangular assemblies to mount the new raw speakers. Remounted to the rear deck, the assembly looks original to the car. Much like the OE speakers, this rear speaker setup really adds only mid-high tones due to the acoustic limitations of the rear deck mounting position.

The Premium sound system has a bi-amplification setup for the door speakers, where one amp powers each woofer and another powers the combined midrange and tweeter speakers. On the face of it, this arrangement is a very high-end approach to car audio even today. The problem is that the stock Nokia power amp is so undersized that it renders this approach moot.

The original Nokia amp also had an option for a Digital Signal Processor (DSP) 

Nokia DSP
Control

control panel located in one of the door pockets, a radically hi-tech item for its day. It was a very rare option whose value was questionable due to the low power output of the Nokia system.

To really make a Premium System upgrade sing discard the bi-amplification approach and replace the original Nokia power amp under the seat with a more powerful aftermarket one.

Original Nokia Amp.

A 4X75-Watt RMS per channel amp is good and easily fits completely under the seat; 4X150-Watt or more RMS is a lot better. More power does not translate directly into louder music, but it does significantly reduce distortion, improving clarity at moderate volume levels. With all the engine sounds we have come to love in our 993 cabins, having a system that can overtake these sounds and still provide good clarity is a big plus. 

If I was to do it again I would use all the available space under the seat for a bigger two-channel amp powering the door speakers only and use any amp internal to the head or a second physically compact smaller power amp under the dash for the back as the back speakers really don't add much to the sound do to the limitations of their placement in the car.

Some really high-power amplifiers are packaged in a width that easily fits under

Alpine brand 
aftermarket amp.

n the passenger seat from left to right and can be placed so the amp's body extends rearward into the back seat footwell. It can then be hidden under the carpet pad. The only limitation in amplifier size is the available space under the passenger seat extending rearward, unless one wants to go to the complexity of relocating the power amp to the frunk.

Constant-on primary power for the power amp can be picked up under the seat. In my case, I added a fused heavy power wire directly from the car battery with the reasoning that an amp where all the channels combined pull a bit over 300 watts MAX, any current limitations of the existing power wire may translate into reduced amplifier performance, negating some of the advantages of the amplifier. Having now, years later, thought about it for a while, adding a dedicated power wire was probably overkill, as amplifiers really run most of the time at a small fraction of their maximum output and only experience full output for a few milliseconds at a time.

If you want to avoid butchering the existing wiring harness or are not handy with a soldering iron, Tore's website, bergvillfx.com, offers all sorts of hard-to-find 993-specific wiring harness adapters for audio upgrade projects. Crutchfield can also be a source for certain hard-to-find wiring harness adapters. Also, here is a wiring harness kit at Discount Audio for replacing the Nokia amp without cutting any wires. If all else fails, eBay is my go-to source of last resort for hard-to-find wiring harness connectors. 

In my case, I cut off the original speaker frame's wiring harness sockets, making them into wiring harness adapters, avoiding cutting and soldering new terminations to the original speaker wiring harness in the doors. Similar to this, pre-made adapters are also available from Crutchfield and others.  This page offers audio wiring details for the 993.

The wiring diagram in the 993 Shop manual is clear and concise as to how the existing speakers are wired, making it easy to tap new speakers or a replacement power amp into the existing wiring harness. The upgrade can cost less than $100 using four inexpensive two-way speakers, or the sky is the limit through Best Buy, Crutchfield, or other suppliers, depending on what level of sound quality you desire.

Car Seat removal – See: how to remove front seats without drama

To Sub-Woof or not, that is the question -- Getting clear sound and good bass response in a 993 audio system can be a challenge. As discussed above, even the original Premium Sound System is grossly underpowered. I put a 75-Watt X 4-channel Alpine power amp under the seat, powering all four speaker positions

Having replaced the OE door speakers earlier and having lived with some nice two-way coaxial speakers in the doors for a while, I was looking for ways to improve the smoothness of the bass sounds from the speakers. 

Some have worked up very creative ways to add a subwoofer housing to smooth the bass. In all these cases, one has to give up cabin space.

The 993 doesn’t have much cabin space, to begin with, so I looked into other options. I ended up replacing the door coaxial speakers with a two-way speaker system where the woofer is screwed directly to the door’s speaker hole in the door card and had a stated frequency response of 35 Hz (doubtful) and a separate tweeter mounted next to it behind the original Premium Sound carpeted speaker box cover. I then added a Soundstream BX10X Digital Bass Reconstruction Processor DSP  for about $60 new on eBay to the power amp under the seat.

The BX10X is not an equalizer in the conventional sense. It recreates low-frequency harmonics lost in a 911 cabin space and sounds great! For general pop music and things such as acoustic guitar, it causes the bass to feel much smoother, eliminating the boxed-in-like sound inherent in door-mounted speakers. I feel that for general listening, it eliminates the need for a subwoofer while transforming the sound for the better.

My initial experience with music with a hard beat was that the BX10X easily overdrives the 75-watt RMS per channel amps, causing distortion. Having had it in the car for a while, I have now set my 10-year-old Alpine radio’s bass control center frequency from 100 Hz to 50 Hz and control the BX10X level using the standard bass control on the radio, and found overdrive distortion to not be a big issue.

If your goal is to have powerful thumping, low-rider worthy bass, this solution is not for you; most likely, a much larger power amp of greater than 150 Watts RMS per channel in conjunction with the BX10X or a separately powered subwoofer enclosure would be the ticket. Some newer head units incorporate features similar to the BX10X, eliminating the need for this extra box.

Adding  an auxiliary analog audio input for Bluetooth or satellite radio to your stock radio head:

Using an FM modulator or cassette adapter to create an analog auxiliary input for a file player, Bluetooth, or satellite radio can significantly diminish the quality of the sound produced. Depending on the quality of your audio source, the best way to maximize sound quality is to have a direct analog audio input.

The Porsche CR210/CDR210 radios were not manufactured with a simple rear panel connection for auxiliary analog audio input. They can be modified as a DIY project for those who work with electronics, or the radio can be sent to the Becker service center in New Jersey to be modified at a very reasonable price.

Porsche Radios CR220 / CDR220 have back-panel connections for a CD changer, which also allows the selection of an auxiliary input when not using a CD changer. There are connectivity options from the Becker service center for these units as well.

Continental-branded radios:

Continental brand radio heads are quite popular for replacement units in the 993/964 Porsche. The primary attraction is that they have a front panel that looks somewhat period-correct for these cars. 

Here is the  Continental radio product line as of 2022:

https://productimageserver.com/literature/brochure/94436BR.pdf

It seems their radio heads do not offer line-level outputs to directly attach a power amplifier.

A small nuisance when using a smartphone for hands-free phone calls. It has been reported that with the Continental CDD 7416, there is a delay where the unit clips the first few seconds of a call when initiated. The workaround is to have some music on in the background on the unit.

Power Amp Adapters:

Using a speaker-to-line level adapter to attach a power amp to almost any head that does not allow for a direct power amp connection introduces noise and distortion. This distortion in most cases will be 

well above the threshold where one will be able to hear it and/or will cause listening fatigue at volumes high enough to cover the engine sounds in our cars.

For this reason, if one has any notion to add a power amp sometime in the future, the Continental radios are not the head units to consider. Specifications change over time, so if you are planning to replace your radio, head check the specifications of the head you are considering, as Continental-branded units may offer power amp connectivity in the future.

The Blaupunkt Bremen SQR 46 DAB Radio Head:

This radio head has become quite popular as an aftermarket replacement for the 993/964. It is a good bit more expensive than some of the Continental offerings, it does look somewhat period correct for a 993/964, and most importantly, it does have RCA-style line-level outputs to directly attach an external power amp. If you envision adding a power amp at any time in the future, this is a popular unit to consider.

The Blaupunkt Frankfurt RCM 82 DAB is a newer product with updated functionality.

A partial list of features & updates includes:

• The newer Bluetooth version 5.x is supported, making for more reliable music streaming connections.
• It is able to play audio files in the lossless FLAC format.
• It does not support the pre-2012 30-pin Apple devices; however, it works with newer devices with the Lightning connector via a front or rear USB port.
• It carries forward the 4-channel RCA plug preamp outputs and a usable 24 watts RMS per channel speaker output.

More on Blaupunkt car audio products can be found here:

https://blaupunkt.com/automotive/incar-entertainment/autoradio/

The Pioneer new SXT-C10PS will be available in October 2025 and can be used with or without an external power amp.
Here is a list of announced features:

• Retro-style cosmetics  

• Bult-in Bluetooth® (HFP, A2DP, AVRCP 1.5)  

• Built-in DAB+ Digital Radio (Digital Radio Tick Mark Approved) / FM         Radio  

• RGB multi-colour illumination  

• Front USB 2.0 port for smartphone connectivity (1.5 A maximum current capability)  

• Front AUX input                                                                                                                                          • 13-Band Graphic Equaliser (GEQ)  • Manual Time Alignment / High Pass Filters (HPF) / Low Pass         Filters (LPF)  

• 3 x RCA Pre-Outs (Front / Rear / Subwoofer)  • MOSFET 50 W x 4  

• 3-Way Network Mode or Standard Mode 

• Memory Back-Up for short/long-term storage.  

• Removable fascia panel for added security.  

• 12H / 24H Clock • Installability to suit most vehicles(4)  

 

The Porsche Classic Communication Management (PCCM) head. 

It looks good in the dash and has a lot of functionality.

However, it is expensive and its placement is low in the dash, making it a poor substitute for a cell phone using Google Maps/Apple, on a smartphone up high near the clock in a phone mount. One may be better off using one's phone with a phone mount and a Bluetooth modification or adapter. 

8/20/2025  I updated my radio head for music streaming through my smartphone.

Alpine UTE-73BT

• I installed the Alpine UTE-73BT single-DIN radio head for digital media (no CD or other Mechanical drive)
• https://www.alpine-usa.com/product/ute-73bt
• Great for use in a 911 cabin where all controls & mapping remain on the phone in a cradle near the clock, where the hands-free calls and audio are played through the radio head using Bluetooth.
  
• If you are replacing an older Alpine unit, such as a CDA-9856, it is likely that the plug connections used for the old head can be used with this unit without modification.
  
• The unit has parametric equalization and something called a "Bass Engine' that makes it ideal for external subwoofer connections or a DSP bass reconstruction processor (active harmonic recovery) system for smoother bass reproduction. 
• The sound quality from Amazon's music streaming service is not as good on this unit as the Apple MP-4 I-Pod player wire attached to the Alpine CDA-9856 it replaced. So it is unclear to me if the slightly lower sound quality is inherent in the unit or a byproduct of the differences in the quality of the music sources.

8/13/2025 Recently, I tried installing an inexpensive CarPlay

The CLP4A US Digital radio head

 and an Android-compatible touchscreen radio/digital media head as an upgrade to my old Alpine radio head; the results were disappointing at best. I immediately replaced it with the Alpine UTE-73BT discussed above.

Here is the review:
https://993servicerepair.blogspot.com/2022/09/review-of-inexpensive-touch-screen.html

In any event, whatever head/speaker or amp combinations you are considering, here is a page with the needed wiring information to get things installed.

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