Well,since I've got the day off I decided to tackle the job of installing an aftermarket stereo in my '88 Jag. Aside from the quirky wiring setup that Jaguar uses for their sound system all seems somewhat straight forward. I can't seem to locate which wire controls the power antenna. According to the wiring diagrams it says it's either green/black or just green but I get nothing when my unit is turned on. I know my power antenna works because it functioned just before I removed the factory stereo. Any tips on which wire it might be? Also,I was thinking of wiring the sub speakers to the radio sub outputs. Has anyone done this or do you just wire them in as your rear speakers? Happy New Years Everyone!

 

Happy New Year to you and yours as well, 95Leaper!

I follow so many threads that I can't keep track of which car you're working on from your long list of Jaguars (!), but if it's the '88 XJ40, Figure 28 of the the '88 XJ Electrical Guide shows the radio connects to the CPU via a Light Green wire with Black tracer line (LGB), and the CPU connects to the antenna up relay via a White wire with Green tracer line (WG), and to the down relay via a White wire with Black tracer line (WB).

My assumption is that the CPU has a logic circuit so that when it receives power on the LGB wire it raises the antenna, and when the power is removed it lowers the antenna, but the schematics don't explain the operation.

If the schematic you have is incorrect, you can download the 1988 XJ Electrical Guide at the link below courtesy of our member Gus at jagrepair.com:

http://www.jagrepair.com/images/Elec...Electrical.pdf

Cheers,

Don

 

Thanks Don,it turned out that the signaling wire coming out of the radio was the wrong wire,failing to signal power to the antenna. Got that one all figured out but now I've got another issue. I managed to wire up the system as such : Left Front and Left Rear Door Speakers to Radio Left Front Circuit / Right Front and Right Rear Door Speakers to Radio Right Front Circuit / Rear Subs to the corresponding right and left circuits. The issue I'm having is that as I turn up the volume past a certain level,power to the stereo cuts out momentarily then will resume and cut out again,etc,until I lower the volume to a certain level. Could the power from the stereo be overloading the system? It's a typical Sony 52watts x 4 CD player stereo that I've had laying around for about 7 years.

 

My first thought is that perhaps a protection circuit in the head unit is engaging to protect against excessive current flow. Is it possible the impedance of the subs or other speakers is lower than specified for the head unit?

Another possibility could be that the electrolytic filter capacitor in the power supply is failing due to age and has lost some or all of its capacity, resulting in momentary loss of current through the power transistors when amplifying large waveforms. Is there any hum from the speakers?

Cheers,

Don

 

I suspect one of the rear bass speakers may be bad or possibly shorted. I guess I'll start by unplugging each speaker and see if there's any difference. From what I've researched it either a poor power supply (like you suggested),a bad speaker,or a discrepancy in the ohms. My guess is I've got a bad speaker because i does sound like it's weak compared to the others. Has anyone here replaced/updated their speakers and what size did you go with. I have an 88 VDP and according to what it's supposed to have is 4" speakers in the doors and under the rear seat wells. It also said 5 1/4" speakers will fit in the rear well area as a replacement speaker. Should I just use regular 5 1/4" speakers or a 5 1/4" subwoofer for the wells?

 

A 5-1/4" speaker is just that, a 5-1/4" speaker.

There is not really such a thing as a 5-1/4" subwoofer or a 5-1/4" tweeter for that matter, although the speaker selected for upper ranges wouldn't need to move as much air as the low range so it could be stiffer I suppose ...

The way a 5-1/4" speaker becomes a subwoofer or even a midrange/tweeter is through the use of filtering, or frequency suppression.

If the driver (speaker) is to be used as a woofer, a coil is added to the circuit to choke off the upper frequencies ...usually in combination with a tuned or ported enclosure.

For maximum efficiency, the internal volume of the enclosure must equal the volume of the free-air resonance of the speaker cone. This would be impossible in the Jag unless you installed an engineered enclosure to house the driver. This is often why you see subwoofers being sold as in-trunk units, already housed in boxes that are tuned to the speaker specs.

In the case of using the same 5-1/4" speaker as a midrange/tweeter, capacitor(s) would be added to the circuit to filter out the low frequencies.

Design and implementation of these coil and capacitor filters (aka crossovers) and the values of the components used are never an off-the-shelf or one-size-fits-all solution - there's quite a lot of math involved to achieve the best results - it isn't easy to compute for the average room environment, let alone a car interior!

So just but some all-range 5-1/4" speakers (I'd buy ones with added whizzer cones) and accept the available room you have in the rear - fit them with a nice foam gasket, button it all up and you'll be fine. You can also add some fibre batting inside the enclosure to "fool" the speaker into thinking it has a larger enclosure than it really does, but make sure it can't rattle loose or touch the back of the cone.

 

Hi Larry,

I agree that there are no true 5-inch subwoofers or tweeters, though some companies will try to sell you a 5- or 6-inch subwoofer. 5-inch auto speakers tend to be designed for either full-range or woofer use, though some higher-end manufacturers offer midrange and midbass units as well. The Thiele/Small parameters of quality drivers vary greatly depending on the frequency range they are designed to reproduce and the type of enclosure they are to be mounted in (if any).

A nominal 5-inch woofer will have a different suspension and longer voice coil to allow greater cone excursion compared to a driver intended for midrange or full-range reproduction. Magnet size and dust cap/phase plug design are other obvious differences. Midrange and woofer design parameters will also vary significantly depending on whether they are intended for use in a sealed enclosure, ported enclosure, or an infinite baffle/free air installation.

Here are just a few examples grabbed from the Madisound site:

Morel 6" auto full-range coaxial driver (Fs 1124 Hz, Qts 1.82, Vas 15.35L, linear excursion +/- 0.25mm):
https://www.madisoundspeakerstore.co...l-integra-624/

Scanspeak 6.5" auto woofer (Fs 55Hz, Qts 0.48, Vas 17.9L, linear excursion +/- 4mm):
https://www.madisoundspeakerstore.co...e-woofer-each/


And for even more extreme differences in drivers, here are some specs of drivers designed for home use:

Fostex 5" Full-Range driver (Fs 65Hz, Qts 0.44, Vas 9.876L, linear excursion +/- 1.5 mm):
https://www.madisoundspeakerstore.co...alnico-magnet/

Scanspeak 5" Midrange (Fs 35Hz, Qts 0.23, Vas 23.8L, linear excursion +/- 3 mm):
https://www.madisoundspeakerstore.co...-5.5-midrange/

Scanspeak 5" Woofer (Fs 34Hz, Qts 0.23, Vas 20.0L, linear excursion +/- 9 mm):
https://www.madisoundspeakerstore.co...-woofer-4-ohm/


Cheers,

Don

 

Yes Don, woofers are basically air pumps - the greater the cone (piston) travel, the more air is moved and therefore the lower the bass frequency.

The main thing to keep in mind in any speaker installation is to isolate the front of the cone from the back. When a speaker cone moves, the in-phase front movement will be cancelled out by the back out-of-phase signal if the air from the back reaches the front. Putting speakers in a box is one way to prevent this happening.

Sometimes the speaker enclosure will feature a tube or "port" somewhere in the case. These "tuned" ports (a port with the same volume as the free-air resonance of the cone) use this out of phase rear signal to produce a parallel in-phase signal at the port mouth, which (in theory), doubles the virtual size of the woofer.

This is why so many sub-woofer installations feature a ported design. A 10" woofer with a correctly designed enclosure and port will pump twice the volume of air than the woofer alone, effectively giving you a 20" woofer. In some designs, a speaker lookalike, known as a "passive" radiator will produce a similar effect, using the out of phase air in the enclosure to radiate an in-phase signal equal to the compression produced by the active woofer.

It's been a long time since I designed and built audio systems but my reggae club dual 15" folded horn "crusher" enclosures of the early 1980's are legendary!! (at least in my own mind!!!)

Cheers

Larry

 

I would like to have experienced those!

I've also built or modified a number of speaker systems for auto, pro audio, guitar and hi-fi, including my own high-end home reference system using Dynaudio tweeters and Eton woofers, with 4th-order crossovers I optimized both by ear and instrument testing, and ported cabinets with mahogany veneer that I built from scratch. For those interested in designing their own systems, I highly recommend Vance Dickason's book as a good primer:





If you get really serious, a couple of other good ones are Joe D'Appolito's and Bob Bullock's:







Cheers,

Don

 

Well,I managed to install new speakers in the rear doors and rear wells so far. Tomorrow I plan on continuing with the front doors. So far I still seem to be having the issue with the radio cutting in and out when I turn up the volume to a certain level. Once I replace the front speakers the only issue left would be the power line not getting full power. Has anyone had this issue occur and what was your solution? I've installed many stereos over the years but never had a situation like this.

 

If the nominal impedance of the new speakers is appropriate for the head unit, another remaining suspect would be the head unit itself. Since it's been sitting around for 7 years, it is quite possible some of the internal components may have deteriorated. The electrolytic capacitor(s) in the power supply would be my first suspect(s). I've learned from experience to suspect any electrolytic that is more than 10 years old.

Another thing worth doing would be to test all the speaker circuits for a short circuit or resistance that is significantly lower than the other circuits. You can test with an ohmmeter at the head unit connectors ohmmeter. The resistance should be just a little higher than the speaker's DC resistance across its voice coil terminals, with the rear speaker circuits measuring a little higher than the fronts due to the increased length of wire.

Cheers,

Don