Stereo Project Write Up

XJ-S
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IIRC, Jaguar actually put a small coil in the + lead of each rear speaker. Some people call it a “choke”. Basically it serves as a simple passive crossover, causing the high frequencies to taper off at -6db per octave. Apparently Jag didn’t think high frequencies coming from back there sounded right either.

(FWIW we know that an octave is 8 notes - do re mi fa…etc… In terms of frequencies, each doubling of the Hz, or frequency, is one octave. So it’s one octave from 100-200hz, and one octave from 1000-2000, and one octave from 10,000-20,000. I always found that interesting, but maybe I am just a nerd.)

As I commented previously, just my opinion, tweeters in that location don’t sound right to me, moves the sound stage back, when I really want it forward.

This stuff is all personal taste, there isn’t really a “right” answer. The right answer is what sounds good to you, the owner.

Edit: This also may be a little different in a convertible. Top down / soft top might tend to dampen the rear highs a bit to where they would not be as noticeable.

Edit #2: I am guessing the facelift cars must have different front speaker arrangements - a 6.5" won’t fit in the doors of my 89 without some significant cutting. Stock was 5" which is an odd size in the US, I bumped to 5 1/4.

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After driving the car a bit and getting some good listening hours on the stereo, I knew I wouldn’t be totally happy until I got some tweeters upfront, I wanted to brighten the high-end a little bit and move the soundstage forward.
I decided the best place for them in my car would be in the a-pillar, which is a bit tricky, but in the end I think it came out pretty nice.
I chose Rockford 1” soft dome. Nothing bigger would fit, and I don’t care for the sound of hard done or metal tweeters.
Rockford Fosgate T1T-S Power 1"… https://www.amazon.com/dp/B0035R8S9U?ref=ppx_pop_mob_ap_share

First order of business is a 1 3/4” hole in the trim. In my car with the motor mouse seatbelts the a-pillar trim is injection molded and is one piece all the way back to the b-pillar.

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Word to the wise, there is a piece of sheet metal inside the trim right at this point. It has a 90d bend in it. If you catch the edge with the hole saw it will rip the end off your trim.

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Now I needed some spacer rings to match the curve on the trim to the tweeter, and to angle the tweeter like I wanted. A 1 1/2” pvc tee made the ultimate sacrifice.

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After some careful work with a drum sander in the drillpress we have a good fit to the trim.

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I did the drivers side first and found that sheetmetal piece. Gonna have to do a little repair on the vinyl to hide my screw up. Not the end of the world.

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Now need to listen a bit more to dial things in, but initial results are what I had hoped for.

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One more pic from the top. You can see how the spacer ring fits. The slice I took in the bandsaw pic above was attempt 1, not enough of a wedge. I cut a thicker wedge then put the curves in with the drum sander.

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Nice work Bob - can you give a short removal step outline for taking the molding off - I want to run some wires up through the A post area and have been holding off until I get a good description of the removal so I do not ruin it - Tex.

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@Adna_Terry_II I believe this only applies to cars with the motor mouse seatbelts, a.k.a. passive restraint.
Starting from the front, believe it or not, there is sort of a bead molded in to the back of the molding that snaps into sort of a channel on the a-pillar and up along the roof line. If you start gently prying at the base of the a pillar, where it meets the dash, the whole thing just kind of peels out. Work your way back along the roof line.
There are 3 small J shaped spring clips that will probably pop off and fall out as you remove the molding along the roof line. I never did figure out exactly where those went, but they seemed to be un-necessary to firmly re-attach the molding when I re-installed.
Working your way to the rear, as soon as you pass the B pillar, where the seatbelt comes out, there are two spring clips similar to what you would find on the door panels. One immediately behind the seatbelt exit, and another at the very rear. Those gently pull straight out, toward the centerline of the car, although they’re pretty stiff, and they may tear loose.

There is a sheet metal strip molded into the back of the trim that holds the head of these two spring clips, it’s only held in because the vinyl was molded around it, and that’s what could tear loose. It’s not the end of the world, i used Loctite vinyl repair glue to repair the one of mine that came loose. I just needed to reattach the sheet metal strip to the back of the interior trim piece.

To re-install I started from the rear, lining up the two spring clips, pushed them in, then lined up the channel and give it gentle smacks with my fist as I worked my way forward.

Suggest you take pictures of the fit and gaps at the B pillar, and where the a pillar trim intersects the dash, because unless you know exactly what they look like before you take them apart, it may not be intuitive how good of a fit you should expect on reinstall.

I hope this helps. It’s a lot more complicated to try to describe than it is to actually do.
Bob

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Well Bob, thanks for the details - I do not have the seat belt that slides along the door, on my 1991 pre-facelift coupe, but just the same, I would venture a guess that for the most part, your details will help me, especially the reminder to take pics before removing anything - Tex

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Another tweak. Probably the last one. I was still not quite happy with the stage, my rear speakers are 6” 2-way Polks. Having a tweeter behind you is never a good idea, I don’t know what I was thinking when I did that several years ago.

One solution is a different speaker. The other solution is to install a passive low-pass crossover in the positive wire to the speakers to taper off the high frequencies.

Basic passive crossovers can be built in 6dB, 12dB and 18dB per octave. So, if I install a 6dB low pass crossover, sized for say 900 Hz, at 1800 Hz the sound above 900 will be 6dB quieter, double again to 3600 Hz, it’s another 6dB quieter for a total of 12 dB, and so on.

For low-pass applications like this, I like the 6dB crossover, it’s a more gentle taper. It just sounds better to me. For tweeters and certain mid range applications, where I’m building a high pass crossover I might go 12 or 18 dB.

All of these crossovers are various combinations of capacitors and coils.

Here is a table for the cap and coil values for 6dB crossovers.

Coil sizes are measured in milli-Henrys or mH. For my 4 ohm speakers, 800hz low pass is .82mH and 1000hz is .62mH. I’m wanting to taper the sound starting at about 900hZ. Which is a frequency I very scientifically selected by listening to various tones and frequencies and going “yeah that sounds about right”.

SO, we buy a couple of .75mH coils and put one in series with the positive wire on each rear speaker. For me it was easier to hang them on the back of the amp board, the other option is to pull the speakers and put them right at the speaker.

This change really pushed the stage forward, and I had to fiddle around with the EQ settings in the deck quite a bit bit to get it back to where I liked it, but at this point I’m quite pleased with things.

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2 Likes
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Hello Bob, I’ve just seen this great post of yours and I much appreciate to see somebody who’s an enthusiast with serious improvements to his special ride and to get to see details of the given project here, in this great J-L venue.

I own a 1994 XJS convertible (BRG) to which I’ve applied several mods and improvements in just about every category, which of course, includes the sound system and I’m thinking of, perhaps, doing here something similar to what you’ve done. Maybe we can get more Jag guys to go for it…

Reinaldo
Oceanside, CA

1 Like
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Thanks @Reinaldo! Let’s see some pics! When I did this post, I learned that there are more stereo enthusiasts on this site than I expected. @Aristides for one done some cool stuff to his XJ6 as well as his XJS.

1 Like
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Cool, I’ll keep checking.

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Veekay,
Did you bolt down the subwoofer, or is it just sitting brhind the seat?
Im pretty much duplicating your setup with the Alpine amp, JBL 620 speakers, and the Kenwood subwoofer. I also replaced the rear speakers with a pair of midranges.

Thanks
Jon

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Just sitting behind the seat. It’s perfectly sized to get pinned by the passengers seat and the rear seat when the passenger seat is moved all the way back. It will not move. I applied some Velcro tape to the bottom, but it’s not needed at all.

I couldn’t be happier with the result of the subwoofer. After playing around with the setting for awhile, I enjoy it at 50% volume using the knob it comes with.

On my head unit, I set the subwoofer cutoff at 63Hz.

Only problem I have now is when playing music (too) loudly, the midrange/tweeters cut out, but the sub still plays. This happens only at high sounding parts on songs being played loudly. Something is sending the Alpine amp to protect mode during those parts. I wonder if I ran a power feed directly from the battery, if that would resolved that? But then, of course, that might eliminate the need for the conveniently small amp.

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Thanks for the info. That’s what i thought you’d done, but wanted to check.

Jon

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hello
probably more like 63Hz (63MHz is far out of human ear capabilities) : :innocent:

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Yes, of course. 63Hz, I just edited/fixed it. Thanks.