My 1987 Porsche 928 S4, 5 speed - Sound System Page


 
 

Sound System Upgrade

My first disappointment, and I do understand that this car was not build for audiophile's musical experience, was flatness of the sound.  Once I have noticed that stock ITT speakers had cone frames were made out of plastic - that was it.   So, once I was sure I could not live with that I started putting the concept together.  Since I was not about to spend $4,000 to $6,000 for installation, in addition to $2,000 for the system, I had to try to undertake this task on my own.

This is the final result

 

 

Foam cover with black carpet

 

 

Cutouts for amplifiers cooling

 

Top plywood panels wrapped in black leatherette

 

 

Quarter-turn fasteners used to secure upper panels to the rack

 

The pages linked below show the details on what system consists of and how it was built.   It took me 2 years what would have taken Unique Whips (Speed Channel) two days.  But I know I had more fun.


Construction steps:

 

 


 


Other 928 Sound Systems:

 



Exhaustive List Of Car Audio Manufacturers:

 

 



Sound System Components


With advise of Kirk Neal (of Ampmanaudio - unfortunately not in business any more), I have selected the following system components:

  • CDT Audio Professional HD-642 3-Way System for the front (6.5" Mid-base, 4" Mid-range, 1" tweeter and 60dB "Phase Perfect" cross-over),

3-way system
  •  


  • CDT-6 (replaced by HD-6) 6.5" mid-base speakers are used for rear fill,

rear fill speaker
 

 

  • Old Eclipse 56050 (2000 model - company is out of business) 6 CD in-dash changer (GREAT SOUND BUT VERY UNRELIABLE - FAILED AFTER LESS THAN 2 YEARS (AND PRESENTLY OUT OF BUSINESS), - 1ST CD LASER FAILED, THEN REMOTE WOULD NOT TURN AMPS OFF - SCRAPPED AND REPLACED WITH TEMP JVC FOR TESTING OF HD RADIO - SEE BELOW):

 

Changer Mechanism

 

 

 

 

ECLIPSE COMMANDER Ready

ESN (ECLIPSE Security Network)

Equalizer/DSP Sound Processor Control (optional)

6 in-dash CD Changer with Daisy Chain linking

8-times over sampling digital filter & dual 1-bit D/A converter

CD Text-Ready  

Integrated Optics Pick-Up Unit

Digital Servo System (DSS)

Enhanced error-correction capability

The ECLIPSE Memory Buffer

Highly Balanced Oil Damper

High Quality Film Capacitor

ECLIPSE STARTUNER IV

24 Station Presets (18FM/6AM) & Preset Scan

High-Voltage (5V) & Low-Impedance (55 Ohms) Output

ASM (Auto Station Memory)

Free-Flow Signal Circuit

Copper-Shielded Chassis

Audiophile Components

Independent Bass/Mid/Treble Memory for Each Source

3 Pairs of RCA Pre-Amp Outputs

Non-Fading RCA Pre-Out Terminals for Subwoofer

NOB (No Ordinary Button) Rotary Volume Encoder

High-Visibility VF Display

ECLIPSE LAN Advanced Data Link System

 

Remote

 

 

 

Power Output: 200W Max. (50W X 4),20X 4 (RMS)

Built-In HD Radio Tuner with Multi-Cast Capability

 Ready For I-pod *

Sat Radio Ready

MP3/WMA Compatible with ID3/WMA Tag

CD/CD-R/CD-RW Compatible

DiAS Digital Tuner

Digital 7-Band iEQ

Gold-Plated Front and Rear Line Output Terminals

Gold Plated Subwoofer Output Terminals with Level/Frequency

Control Rotary Encoder Multi-Control

2.5 V output level for front and rear; 2.0 V for subwoofer

Wireless Remote Control

         * Using KD-PD100 I-pod Adapter

 

Remote

 

 

Unfortunately, this is $160 unit vs. over $800 Eclipse for a reason:

  1. Subwoofer control range is limited (8 steps vs. 20 of Eclipse),

  2. Illumination colors are not selectable (as in newest Eclipse designs and some of Kenwood's),

  3. No treble/bass controls at main knob (this is the same problem with very high end Kenwood units) - one has to use EQ to change those frequencies (4 step operation - not doable while driving),

  4. 2.5 V output level, vs. 5 V of Eclipse, makes this unit more susceptible to an alternator noise,

  5. Key problem:  HD radio is great ONLY when unit locks on to HD signal - which is hardly ever.  The technology as is - is not capable of maintaining HD signal within the FM signal range (HD signal is superimposed on FM waves and decoded by HD tuner).  Refer to this blog for latest on this troubled design.

 

Conclusions: 

  1. HD idea is great, but it does not work reliably.  HD unit has 20-20,000 Hz frequency response and is superior to 40-15,000 Hz range of conventional FM broadcast.  When unit locks on HD signal, I can hear clear and significant frequency range expansion on both ends.  Base becomes deeper and there is no static noise. 

  2. Multicasting stations are great.  On the same FM setting, one can select two or more alternate broadcasts!  Again,  depending on station transmitter proximity, 20 - 30 seconds after tuning in, for stations located 20 miles away in clear no obstruction path, ,those secondary broadcasts will typically drop off completely - silence.  Only on primary broadcasts, units reverts to FM when HD signal is lost.

  3. In present state of technology it is only reliable in a very limited range as supported by referenced above blog and my experience. 

  4. Only when transmission/tuner design changes will be made, HD would have proven to be a superior way to listen to a free car radio, however to be fully appreciated it must be listened to high end sound system.

  5. If HD is not your thing,  then Kenwood (4V) or Alpine (4 V) should be great choices.  If one needs 5V outputs, only Pioneer and Sony can offer such head units. 

  6. If you want no mechanical rotating parts for greater reliability - then Kenwood KIV series unit is for you!

  7. If You want a subscription service and do not mind drilling hole in the roof for external antenna - than clearly Satellite Radio is for you.  I want to have clean looking roof, that is why I am reluctant to get it. Also, paying extra $10/moths does not appeal to me too much.

 

  • My current 2-DIN Receiver with 5V output signal level: Kenwood Excelon DNX995S with NAV and Bluetooth:

    • To make it fit the the trim panel around stick shift was shortened and clock was eliminated.

    • The factory receiver bezel was used for now - with future custom frame to be made to make smooth transition to the center console trim.

 

 

 

 

Specifications

0.4kW

0.6kW

     Maximum Power

 

 

Power into 1 Ohm   

365 W x 2

440 W x 2

Power into 2 Ohms

200 W x 2 200 x 2

    RMS Power into 4 Ohms

70 W x2 95 W x2

RMS power in Tri Mode

70 x 2 + 140 W

95 x 2 + 180 W

    Distortion at nominal power

0.08% THD 0.08% THD

    Signal to noise ratio

98 dB unwtd. 96 dB unwtd.

    Low pass cross-over

40-180 Hz, 24dB/oct. 40-180 Hz, 24dB/oct.

    Frequency range

12Hz - 20 kHz (-1dB) 12Hz - 20 kHz (-1dB)

    Input sensitivity range

0.1 - 5 V 0.1 - 5 V

    Dimensions

150 x 300 x 53 mm 150 x 300 x 53 mm

    Weight

2.4 kG 2.5 kG

 

 

 

Specifications

Q2751

     Rated Power

 

Power into 2 Ohm   

450 W

Power into 4 Ohms

274 W

    Distortion at nominal power

0.05% THD

    High pass cross-over (subsonic)

7 - 42 Hz, 24 dB/oct.

    Low pass cross-over

38 -195 Hz, 24dB/oct.

    Frequency range

7 Hz - 200 Hz (-6dB)

    Input sensitivity

9 V

    Damping factor @ 20 Hz

500

    Bass boost (variable)

 0 to + 18 dB/Fo 43 Hz

    Phase response

Lagging 10° @ 20 k Hz

    High pass cross-over (line out)

7 - 42 Hz, 24 dB/oct.

    Dimensions

232 x 260 x 73 mm

 

 




honeycomb viewcut-away view






  • Audio Control 24XS electronic cross-over for separation between subwoofer and rear woofers (discontinued: this is current cross over)
  •  
    • With DNX995S internal High-pass crossover, this unit is not kept in for aesthetical reasons, whereas the Kenwood unit provides required separation between rear woofers and subwoofer.
hi-pass cross-over

 
 
 
 
  • Yellow Top D34/78 Optima battery is one of the best for car audio systems.  Which is better - there are split opinions.  I should be able to tell after 4 years and few complete discharges.  Positive cable clumps under the car had to be loosened to reach batter "+" post.  Battery box covered had to be insulated from battery posts since battery height leaves no clearance between posts and the box cover.  I have used back adhesive rubber sheet from McMaster to accomplish that.

 

Source Link Source Link Source Link Source Link Source Link Source Link Manufacturer: Zed Audio

Part Numbers for all Stinger interconnects/blocks/cables Part Numbers are shown in the links shown above and in the  System schematic diagram

 

 

 

 

 

 


 


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