...miserably failed.
Soundproofing can do a lot of good but hardware must help. And that kind of wooping 4W woofer and tiny little tweeter...just did not have enough life in them.
I wouldn't blame it on the speakers entirely. I hooked up a 100W RMS DLS MS6 car speaker to the output. I know for a fact that this speakers supports a lot of bass. However, At full bass and treble the sound was not good either.
A little progress had been made however. If the box started to distort at 2/3 volume, now it distorts at 1/2 of volume.
Here are some pics too:

i was thinking about soundproofing some of my boxes but as you said its not made effect im rethinking would putting a wad of rockwool insulation in the back have a different effect from the flashband stuff you used as we used to used it in our hifi speakers years ago to try and give it a richer deeper sound

It-s always worth a try.Worked on the Tecsonic as it was big and the speakers were not that bad. This is special car insonorisant. The rockwool will not give extra strenght to the box, and the hifi speakers, as they used to be made of wood, did not need extra strength.
When knocked, the soundproof speakers now go "thud thud" and before they go "click click"

Ah, something i forgot about the D8734:

Even if the speakers have 8 screw holes, 4 of them were empty. You can fill them with PC unit screws. Also, the speakers hold some kind of protection (a resistor) you can easily cut off as it-s not really needed and takes out sound.

hi ya mate i havent got the same stereo as you but was going to do it to some of my other boxes thanks for the tips atb daz

i bought my 8734 in 1994,and i have still got it but i have'nt used it for along time..i've had lots of 8734s since the 80s,in one sence they have nice looks and some good features,but on the bad side they dont sound that great,after half volume the sound distorts to hell and the tone changes and goes flat..the actual speakers are quite good quality,i tried mine on another box and they sound really good..
i spoke to a russian guy on another stereo forum that used to work in a repair shop,he said its the amp in these that are to blame for the bad sound,he said that the same audio chips was used in tv's,very poor..

iv'e had that box before too, and in my opinion, the d8614 sounds way better than it, and it's only half the size of the 8734

I agree, i have a d8614 and, being more compact, sounds better. I suspect however that they have the same speakers, so maybe I will open the d8614 out of curiosity as soon as possible and get back on that.

ye get bak to us on that one NEVONE, would love to know the outcome

I gotta say NevOne that having just recently picked one of these up that I love it and it has a really great sound to it, very similar to the 8614 if not with a touch more bass. Great box indeed.

As promised, i-ve opened my d8614 and took a look. Really easy to open, just 8 screws holding it.

...and what a suprise...the same belgian 4w speakers, and the same tweeters.
They even did not bother to put all the screws on them.

TIP. if your D8614 rattles, get 8 pc case screws and finish the job Philips did not. Put back the missing screws. I guess they did not put them there in the first place in order to cut costs.

Well, here are some pics.
P.S. Now listening to the '14, it kinda sounds better that his big brother...

great pics NEVONE, thanks for the verdict too, just as i suspected, the 8614 on top