Ok, for all the purists out they who would think I am committing a cardinal sin for cutting hole’s in my parcel shelf look away now ! So I really don’t think fitting 2x 6 x 9 good quality speaker is such a bad thing if the grills are plain and black on a black shelf who’s going to pay much attention to them and if they weren’t meant to have them why have the cut-outs underneath to be able to fit them ! Seems to me they should have been there from the start and also the new speakers will look far better than the surface mounted boxy speakers that someone else had installed. It started with me fitting a new modern but period looking head unit that has dab radio /cd/ sd card/aux/usb,Bluetooth hands free. So you have to upgrade your speakers otherwise what is the point . Has anyone else done this and had a good result ? I own 2x series 1 XJ6’s but they are to be enjoyed so I think you can move away a bit from bone stock cars, I don’t know if many of you out there know that the Series 1 XJ6 ( actually was initially called the XJ4 ) was intended to have wire wheels and people on here bang on about keeping steel wheels on the car as it was intended! Have they actually seen or googled XJ4 pictures showing William Lyons intended to have wire wheels but budget’s cut them out . But that’s another story
I fitted speakers to my 71 and also to my current 73. IIRC the 71 had cutouts (round?) and the 73 had a stamped recess (also round) but you had to saw the metal out. Get plain speakers with big magnets (not 2 or 3-way) and you will have lots of bass.
Here’s a story about the 71 (purchased around 1983). I was a car audio fan (in my mid twenties) so virtually the first thing I did was fit rear deck speakers). I got the job done and was very pleased with their sound. The car, parked outside, underwent its first rain episode under my ownership that night. Turns out that the rear windscreen gasket leaked a bit–both speaker cones were filled with water, and ruined of course. Pretty funny in retrospect. Tweeters help too–small enclosures on the dash pad, right next to the A-pillars.
Don’t know how old you are but now days in the US people fill up their boots with giant speakers/enclosures that pump hundreds of watts of sound, mostly bass. I had a student who did that with his BMW.
Mark,
go for it, i did it in my xj & sounds great, i’m a big believer in the general saying " it’s your car you can do what ever you want" …& the XJ29 was the LWB
Mark, I did the same to my S. It has pressings in the shelf with removable covers. I think it was normal by that time, most manufacturers were making provision for after-market audio upgrades.
Because the sound attenuation material was stuck across the whole shelf and was more than 50 years old, it took some chipping to clear it away. I was lucky to find some ex-Daimler speaker grilles that matched the ones in the console. They have expanded aluminium mesh which required strengthening (two crossed and arched straps of galvanised steel) to prevent them inverting if something was dumped on them. I also added some fine fabric to keep dust from settling on the cones.
If you recess the speakers and use flat black satin black speaker grilles it really isn’t very noticeable against the black vinyl rear shelf. Done this to one of my cars with a similar period looking DAB/BT/FM radio and very happy with the solution.
I seem to recall there was a period option for a multiple stereo speaker upgrade which presumably would have used those rear parcel cutouts.
But in my '70 XJ I have the full 1970 period sound effect with original radio and a single speaker in the dash, which crackles each time I go over a bump. I use a separate cigar lighter plugin BT adapter which lets me use phone sound and take calls.
Thanks everyone for all your comments I am probably trying to convince myself that this a necessary and although I can appreciate other owners wanting to keep their cars totally original I think back in the day if these upgrades were available everyone would have chosen them ! Surely enhancing your driving experience is a good thing !
Hi Mark,
If I was you, I would install four mid-bass speakers and tweeters in the four doors instead, they are perfect speaker boxes.
Some food for thought
Sure, Mark - but I would not consider rear speaker’s 100 decibels enhancing my driving experience - and certainly not as a rear seat passenger…
Frank
xj6 85 Sov Europe (UK/NZ)
Hi Frank , slight exaggeration 100 decibels ! You are aware that modern stereos have settings to place the sound where you want it and also a volume control 
To go back to the original post, I don’t think you are committing a cardinal sin putting speakers on rear parcel shelf.
Firstly since the factory has provided cutouts for exactly that purpose and secondly because ‘stereo speaker system’ was, I believe, a catalogued original option which would surely have used exactly those cutouts.
Totally agree Bertie ! I actually didn’t agree with the earlier comment of putting speakers in all 4 doors would be better as door speakers generally are not as good a quality and you would be cutting out all 4 panels which would be more noticeable and harder to go back to original if ever needed !
The only outstanding mystery then, is to understand the correct factory / dealer front speaker positioning for the ‘Stereo system’ since the single central dash speaker by itself would not do the trick
Yeah, front dash speaker complete waste of time ! But the door speaker space is only around 4" clear space if you have electric windows which mine is as the motor takes up the space . So, getting hold of good quality 4" speakers that are not too deep a fitting is not easy . Just upgrading the sound system has created so much work and the car looks like a restoration project now with the dash out door cards off back seats out and parcel shelf out 
I suppose if you want to make an omelette you got to break some eggs .
Easy. Your car. Install the speakers.
My car is powered by a 94 Cadillac engine and transmission. Looks like it belongs. runs and drives just fine. I liked the csar as i bought it with the DOHc and h BW66…
CHJ
You cannot place the sound where there are no loudspeakers, Mark - it’s odd that ‘surround’ sound ideal is not mentioned; to balance the rear speakers…
Frank
xj6 85 Sov Europe (UK/NZ)
Hi,
I fitted retro looking Blaupunkt ”Satellite” spekers to the rear shelf using the (unused) rear seatbelt mounting points and fabricated a base plate for the speakers in my period Surround Stereo system in the 1975 XJ6C. The main unit is a 1975 Audiovox Quadraphonic 8-track FM unit, but in order to not overstess the amp I fitted a modern Sony 4-channel amp and all four Blaupunkt speakers have been refurbished by a company called Youngtimerradio GmbH in Germany.
In my opinion the door speakers are sitting too low to give a clear sound, and also the coupé has no rear doors. BUT it has the factory original wires for both the rear door lockimg solenoids (incl. relays) and rear door speakers which I used for the satellite speakers.
Cheers!
Ps. Here: https://www.youngtimerradio.de/
A bit like this, but with a black mesh: Blaupunkt Kugellautsprecher, Einzelstück
My car only had 2 big bulky surface mounted speakers on the parcel shelf which sounded like a cheap speaker in a tin can ! I am in the middle of fitting 2x 6x9 JBL flat fitting using the original cut out location and 4" JBL in the front doors all the speakers have plain black mesh and I have changed the JBL logos for small leaping Jaguar logos. The head unit is a classic period look but with all mod cons and 4x 75watt RMS , so everything should blend in and although it may not be the perfect sound it should way better than I had and the big bonus I get to listen to dab radio which I prefer and also have hands free for my phone on all 4 speakers .with the amount of time it takes to strip everything down to fit properly it’s also worth sound deadening around the speaker areas to improve he quality as best you can ! So yes, I have put a lot of thought into the project and appreciate everyone’s opinion as that’s were all ideas grow . The first plan was to fit a radiomobile stereo 8 track with period speakers but even if you get one that works how long will it last and who actually listens to 8 track tapes anymore so perfect intentions just doesn’t meet the needs for modern day living so you have to find a happy compromise.