| 924/944/968 Stereo FAQ by Walter Spector | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Most of the following information has been gleaned from personal experience in my '86 944. Additional information on differing models and features would be most appreciated. Please send additions and corrections to wws@sgi.com. Factory OptionsAs all 924/944s have a DIN head in the centre console, why not simply note this and then discuss additions? Shorter and sweeter, IMHO of course. Also it seems to me to be worthwhile to divide things up simply between "all 924, 924S, and early dash-style 944" - a fairly simple group WRT speaker placement and so on - versus later 944s, sub divided as needed. 77-82 924The factory provided a location for a DIN-sized head unit in the center console. There is a center dash speaker location for use with mono radios. Cars delivered with stereo radios typically had a pair of speakers installed in the quarter panels on either side of the rear seat. According to Cotton (ref 1), Panasonic units were used in early 924s in the U.K. I am speculating that these were installed by dealers. (Were stereos in U.S. cars also dealer installed? What factory-supplied systems have people found?) 83-forward 924, 924S, 944 to 85/1As with the 77-82 cars, the factory provided a location for a DIN-sized head unit in the center console. There is a center dash speaker location (which is usually empty). The antenna is mounted in the driver's side fender. According to Cotton (Ref 1), starting in 1983 all cars were delivered with 4 speakers: a 4x6" speaker in each door, and a 4x6" speaker in each rear quarter panel on either side of the rear seat. An external fader control was located in the console for front/rear balance. The electronics and speakers were typically made by Blaupunkt and antennas were made by Hirschmann. This seems to vary by country. The Blaupunkt Monterey SQR 23 radio with cassette seems especially common in the U.S. (What other factory-supplied systems have people found?) 85/2-forward 944, 4-speaker systemThere is space for a DIN-sized stereo with provisions for a DIN-sized equalizer in the center console. As with the earlier cars, each door has a 4x6" speaker and there are a pair of 4x6" speakers in the rear quarters. An external fader control was provided for speaker balance. The electronics and speakers were typically Blaupunkt. A typical U.S. 944 came with a Blaupunkt Monterey SQR 23 radio with cassette. The two front 4x6" speakers were Blaupunkt "whizzer cone" speakers and the rear speakers were 4x6" Blaupunkt coaxial speakers. An in-glass windshield active antenna system, using a Fuba preamp, replaced the fender mounted antenna of prior years. 85/2-forward 944, M490 10-speaker systemThis system consists of a better quality head unit with an equalizer in dash. Each door contains 3 speakers - a 5-1/2" woofer and a 4" midrange mounted under the armrest with a small tweeter mounted above the power window controls. Each rear quarter contains 2 speakers - a 6 1/2" woofer and a nn" midrange. The electronics and speakers were again typically Blaupunkt. However the final year or two of the 944, and in the 968, head units carried a Porsche logo and were manufactured by Alpine. Factory head unitsI've uncovered references to at least the following factory stereos: AM/FM/Cassette - 2 audio channels
AM/FM/Cassette - 4 audio channels
AM/FM/CD - 4 audio channels
Note to readers: Please help me complete the above table and following descriptions! Blaupunkt Monterey SQR 23 (U.S. 944 '85 to '86)The Monterey is a digitally tuned AM/FM stereo radio with a built-in cassette player. The AM section also supports 'long wave' reception which is not used in the U.S. The cassette player supports Dolby B encoded tapes. The two built-in power amplifiers in the Monterey are rated at 9-10 watts output (RMS) each - at unspecified distortion into a 2 ohm load. When this level of power is divided between the front and rear speakers by the fader, less than 4 watts per speaker is available. Blaupunkt Lexington SQR 45 (U.S. 944 with 10 speaker option)The Lexington is a digitally tuned AM/FM stereo with built-in cassette player. The cassette player supports Dolby B encoded tapes. There are four power amplifiers, however only the front two are used. The speaker level outputs are connected to a graphic equalizer located below the head unit. Graphic equalizer/boosters (M494??)A graphic equalizer/power booster is provided with the high-end 10-speaker systems. This is either a Blaupunkt BEA-80 or BEA-108. The equalizer/booster takes it's input from the two front channel speaker outputs of the head unit (the head unit's rear channel outputs are not used). The unit then contains four power amplifiers to drive each of the four speaker positions. So front/rear balance is controlled at the equalizer, rather than using the head unit or a seperate fader control. Note that the interface between the head unit and equalizer is at speaker level. Distortion is introduced due to extra amplification stages, compared to a quality aftermarket head unit using low-level interfacing to an equalizer. To mitigate this distortion, attention to setting the gain levels of the equalizer and the head unit is important. (What is the difference between a BEA-80 and BEA-108? What are the per channel power ratings of these units? How many channels of equalization do they provide?) Stereo Replacement TipsRadio removalBlaupunkt radios can be pulled from the dash with a pair of U-shaped wire tools that fit into the small holes in the corners of the unit. Though most any car audio store will have these tools, they can also be fashioned from a bit of coat hanger wire. Power connectorsCrutchfield can provide adapter harnesses to avoid the need to cut up your wiring. An explanatory note about who Crutchfield are (I know, I used to live in the US, but many international readers might get lost here). What alternatives can we dig up between us? List members tend to be keen on home-brew solutions - can we come up with some directions?) This is an area where some simple ASCII art or a URL to a helpful listers' Web site might not go amiss. The six pin connector commonly used in mid-80s cars (e.g., came with the Monterey) has two large pins and four smaller ones:
Surely a source of supply or order no etc. for these would be useful as it is such a specialised item? A second set of power connectors are provided for the optional equalizer/amplifier:
Fuse box access (85/2 944 on, 968)Access to the underside of the fuse box for wiring in new circuits:
Fader ControlA console-mounted front/rear fader control was provided with two-channel stereos. Since most quality stereos now have four audio channels with built-in fader controls the external fader control is useless. Unplug the fader from the speaker wires, then plug the new stereo straight into the speaker wires. If you remove the fader control, you can obtain a blank filler from Porsche - part number 944.613.257.00 for 85/2-forward cars. Speaker connectorsPorsche uses 2-pin DIN plugs for the speaker wires. Most new stereos will only supply pigtails (wire with no connector) for connection to the speaker wires. To avoid cutting up the OEM plugs, buy a few DIN sockets and solder the pigtails to the sockets. Then just plug the new stereo straight into the wiring harness. Certainly UK readers can get these at "Tandy" (local name for Radio Shack chain) or "Maplins" (well known electronics mail order house). Or would a "suppliers" annexe be more practical, as this stuff get voluminous quite quickly and doesn't aid understanding IYSWIM. One source of 2-pin DIN sockets is Metra - who make a variety of car stereo interfacing products. The Metra 70-1693 contains a pair of 2-pin DIN sockets. If your new stereo has 4 audio channels, and you are bypassing the OEM fader control (or equalizer), you would need two of these Metra adapters. The Metra DIN sockets are stocked or can be ordered by most car stereo shops. Crutchfield is a good second source for 2-pin DIN sockets. A third source is Halted Specialties in Sunnyvale, California. Unfortunately, Radio Shack does not stock 2-pin DIN parts. The schematic in the Haynes manual for speaker wires is incorrect for later cars. The colors used for the various speakers are:
CD ChangersTo my knowledge, the factory has never supplied external CD changers for the 924/944/968 series. So custom mounting will be necessary. The most common location to mount a changer is in one of the rear cargo cubbies. Some 6-CD changers are small enough that they could actually fit in the front glove compartment. Power AmplifiersTo my knowledge, the factory has never supplied external power amplifiers for the 924/944/968 series. So custom mounting will be necessary. The most common location to mount external amplifiers is in one of the rear cargo cubbies. Other possible locations include the spare tire well, under the passenger seat, and under the dash. Not much room in these latter locations... Perhaps a list of components known to work? A warning that not all of them will work in odd (i.e. non-horizontal) attitudes would be worthwhile, I think. Speaker Replacement TipsDoor Speakers (4 speaker systems)The doors are usually provided with 4x6" oval cutouts with "European metric" style mounting. Worth noting somewhere that DIN stands for "Deutsches Institut für Normung". It just means "German Industry Standard" and is popular in Europe. The factory 4x6 are Blaupunkt full-range "whizzer-cone" speakers with a paper cone and foam surround. There is a rubber shield protecting the rear of the speaker from moisture. The paper cones on these speakers are very soft, so break up easily at high volumes. The foam surrounds provide very little excursion, which also contributes to poor sound at volume. The Xmax (maximum linear excursion) of these speakers must be very small. Also the foam surrounds become brittle with age and crack - further contributing to poor sound. All cars, except the cabriolet, have a steel window track passing directly behind the speaker area. This causes a serious restriction in available speaker depth. With the usual flat "waffle" style speaker grille (part number 477.867.081), this limits the depth available for replacement speakers to about 1-5/8". Cabriolet owners are lucky - the smaller window allows the full depth of the door for speakers! I have heard of custom installs where 6.5" speaker have been installed. This obviously requires some trimming of metal and upholstery by the installer. A second style of 4x6 mounting was used in some later cars. This is a two-piece assembly consisting of a thick plastic frame and a snap-on grille. The grille area is made of metal with a plastic surround. Using this grille, it is possible to mount speakers as deep as about 2". (An Audax VE4X6F0 midrange speaker, which is 52 mm deep, barely fits.) The parts list for this later grille assembly is:
The JBL GTO-462d (the "D" is important) works like a charm. Beware 'speakers with tweeters that protrude too far in front of the main frame (true of an Infinity pair I tried) as the tweeter bit will distort the grille. Note that the bushings are important to space the frame out far enough from the door panel to allow the frames to snap on. Also note that the replacement speakers MUST be the European oval shape - not rectangular. The replacement speakers must also have a thin steel mounting frame like the OEM speaker - not a thick plastic one. The least expensive approach to mounting a deeper 4x6" speaker may be to make a simple spacer out of, say, 1/2" MDF and use the flat waffle grilles. Spacing the speaker much further out than this is not possible as part of the grille is covered by the dash when the door is closed. Not true for the 924S unless you go absolutely mad IMHO, there's lots of room available before the frame hits the dash. Door Speakers (10 speaker systems)The ten speaker system includes three speakers in each door. Two of these speakers, a 5 1/4" woofer and a 3 1/2" midrange, are mounted under the armrest. A small tweeter (1 5/8", 3/4" deep) is mounted higher in the door. These speakers are connected to a 3-way crossover network which is also located in the door. How deep can replacements for the woofer and midrange speakers be? Front center speaker (924 and early 944 only)In the early 1970s, when the 924 was first designed, mono radios were still quite common. So a single speaker was all that was needed. In most cars this location is now unused, though it might be usefully employed for specialized radio needs (e.g., amateur radio, scanners, or CB radio). One possibility is to use this location to improve the sound staging of a stereo system. In the book Ultimate Auto Sound (ref 2), there are ideas for implementing a center channel concept. The author even includes construction details for a simple center channel mixer and bandpass filter. Perhaps pointers to people who make simple low-power amplifier kits might be useful? I could easily do a block-diagram design for the adapter myself but coudn't do the detail work, unfortunately. Rear speakers (4 speaker systems)The rear speakers are located next to the rear seats in the side panels. Once again, these are Blaupunkt 4x6" speakers. The units in my '86 944 were actually coaxial speakers - paper cones again but with a rubberized cloth surround and larger magnets than the front speakers. Despite the coaxial design, they are not very good sounding speakers. (What other factory 4x6" have people found in there?) According to the Crutchfield catalog, the depth is restricted to 2". However this does not seem to be the case. At least 3" is available, allowing just about any aftermarket 4x6 to be used. Perhaps Crutchfield is thinking of the 924 - whose fenders do not bulge like the 944? Removing the side panels to get to the speakers is not difficult, but takes some time and especially care. Do not attempt it when you are tired or in a hurry! Here are the steps: Trivial, but the indenting is too deep. Too many exclaimation marks make things sound a bit breathless
Porsche saw fit to use glue in some places ... what kind should our intrepid DIY'er use ? Is it needed at all? Let the reader know one way or the other! :-) Are there any lubricants (e.g. glycerine) that might help? Discovering coaxes in the rear was a suprise to me. By any audiophile standards, the better speaker should be in front and a rear speaker simply provides 'fill'. Considering that both front and rear speakers have the same depth and cutout size, it seems likely that someone intended for the coaxes to be in front and the whizzers to be in the rear and somehow this got switched in production! Above is speculation (and applies to a possibly aberrant case) - is it needed? (Don't mean this rudely). Rear Speakers (10 speaker systems)There are two speakers in the rear. These are a 6 1/2" woofer and a small midrange. The speakers are easily accessed by removing the 8 screws surrounding the speaker frame. SubwoofersThe factory did not supply subwoofers so custom installs are necessary. Ideas which do not require cutting up the rear carpet:
Ideas which do require cutting up the rear carpet:
For several good and inexpensive ideas on subwoofer installations, see Ultimate Auto Sound (ref 2). AntennasAntennas (Part one - simple AM/FM reception)The 924 and early 944 typically have antennas mounted in the drivers side front fender. These are Hirschmann units and came in both manual and power versions. The Haynes manual (ref 4) has information on removal and replacement. Which isn't very good. Can a lister do better? Starting with the 85/2 944, an in-glass windshield 'active' antenna system was used. Under the dash, between the glove box and the passenger side fender, there is a small preamplifier - made by Fuba. This amplifier is powered by a lead which runs alongside the coax leading to the radio. It connects, through the wiring harness, to the 'power antenna' lead on the radio in order to get power whenever the radio is turned on. Last, on some very late 968s, a small roof-mounted antenna was used. This is mounted just in front of the hatchback. I believe it is also an 'active' Fuba-style antenna. When installing an aftermarket radio on a car with an active antenna system, it seems to be a common problem to forget to apply power to the preamplifier. The following are the most common symptoms:
Note that the preamp must be connected to a switched source to avoid running the battery down. Again, this is the 'power antenna' lead in the radio's wiring harness. Antennas (Part 2 - Advanced Topics)My 944 came with both the in-glass antenna and a Monterey radio with long-wave (LW) reception. Although LW is not used for broadcasting in the U.S., there are low-power aircraft and marine beacons. So some people without a life actually try to see how many of these beacons they can pick up. It turns out that the factory setup is quite deaf to LW with the in-glass antenna. I actually once parked about 50 feet from a maritime beacon and could not receive it! LW is important to many in Europe so this is important. Amateur radio operators may wonder about good places to install 'ham' antennas. One solution to the problem is to use the two ski-rack bolts which are under the upper side of the hatchback. A mount can be fashioned from a bit of aluminum and is strong enough to support usable VHF/UHF (e.g., 144 and 440 MHz) antennas. For amateur shortwave operation (and 11m CB radios), I've wondered how a magmount on the rear bumper would work. Using some copper shielding material to make a good ground connection to the chassis would be important for efficient operation! An article in the xxx 1998 issue of QST (Ref 6) has some ideas for making effective use of a magmount at these frequencies. Last, what if one wants to receive shortwave or longwave radio from the car, such as when using a car stereo like a Becker Mexico or similar Philips (and certain grey-market Sony) stereos? Attaching a small whip to a hatchback-side mount seems to work. One list member has successfully used the roof-mount active antenna from a 928 (part number 928.645.201.00) with the older and now-infamous Philips DC-777 radio. This roof antenna is also a Fuba-style unit. (Is this the same part as used in late 968's?) I'm sure there are kits about that let one use the rear window defogger wires as an antenna. I'll try to find a pointer. Certainly we should mention the possibility (IMHO). Strange NoisesAM radio reception is especially sensitive to a variety of noises around the car. Three common areas of noise are:
Raspy noise - check plug wires. Many porschelist members use Magnecor plug wires which are designed to both maintain peak engine performance and minimize electrical interference. Magnecor has an optional CN25 version of their wires which are especially designed for suppression at radio frequencies. (See Magnecor's site for more information than you ever wanted to know about plug wires. Some cool pictures of racing engines too!) Make sure the rotor/cap are in good condition. Make sure that good 'resistor' spark plugs are in use. Other areas to check for raspy noises include faulty fuel injectors, and improper bonding of the engine to the chassis. Of course if you have replaced your metal hood and fenders with carbon fiber parts, do not blame Porsche for poor shielding! High pitched whine - this is almost always caused by an alternator. Alternator problems seem rare on our cars. Individual repair parts are available, so total replacement of the alternator is not required. Clicks - caused by windshield wipers, turn signals, etc. If these are bothersome, try replacing the associated relay. Auto Audio (ref 5) has a nice chart for tracking down and solving noise problems. All fine, but there are a few things missing: References
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