Ok, just a thought.

How about using the rear tailgate of your Polo as a sub enclosure?

I know it's not exactly going to be acoustically perfect, but with an MDF or plywood panel in place of the standard plastic trim, some bituminous damping on the sheet metal and plenty of wadding stuffed in I reckon you'd have a pretty decent sealed enclosure with plenty of volume (i.e. litres rather than decibels) for most 8" subs. It should be easy enough to feed the wiring through the top of the tailgate near the hinges (alongside cables for wiper etc.). You wouldn't lose any boot space and potential thieves would be none the wiser.

Has anyone tried this? If there's any interest maybe we could get some baffles made up as a group buy (PhilJ?)

Land Rover Discoverys have subs in the tailgate. There are 2 6.5" (I know they aren't big, but they give out a fair bass shove and are properly amped) behind a mesh grill. There isn't really much sound deadening around the tailgate, and they are mounted in a plastic enclosure.

As I said, don't be put off by their small size, they do a good job. You could probably drop in a pair of 8" subs into the Polo tailgate, but the problem I can see is the boot latch doesn't really hold the tailgate tight. There is still a bit of movement in the seals.

Discuss?

That's interesting... thanks for the reply! My gut feeling is that a single 8" would work really well in an enclosure of this size, although I'm sure that you could get really good bass from a pair of 6.5inchers, too. The advantage with a single 8" would primarily be lower cost, and weight. It would probably be easier for the amplifier to drive, too. Plus I've got a stack of really nice old stock Morel and Macrom 8" subs here ...

But...I don't see how the tailgate seals are going to be particularly critical. Are you concerned that this will mean the speaker enclosure is not being properly sealed or are you just thinking about the tailgate physically rattling about at high SPLS?

I was thinking more of the tailgate acting as a separate entity to the car. So you might not feel the bass, the seals could absorb it all. Purely hypothetical though. The Disco tailgate is huge, and side mounted on some pretty heavy duty hinges. I just get the feeling the Polo tailgate isn't so securely attached. Not too sure though.

An 8" sub on it's own probably wouldn't really be a cause for concern though. I'm definately interested in seeing how you get on with any more preliminary research or whatever. I can't be giving up my boot space

I was thinking more of the tailgate acting as a separate entity to the car. So you might not feel the bass, the seals could absorb it all.

I see what you're getting at, but in practice the seals would absorb very little of the bass, if any. Besides - you want the bass to reach you through the air - not through the car. If the car's body is vibrating excessively, it will resonate at certain frequencies giving boomy, muddy bass - not what you want if you're into good sound. In fact I'd say there's a theoretical advantage to having the tailgate isolated from the rest of the car as it may cut down unwanted resonances to some extent.

I'm definately interested in seeing how you get on with any more preliminary research or whatever.

Cool. I think the first thing to work out would be the volume of the tailgate door as this will give an idea of the kind of response you can expect from a given driver. If anyone can help here I'd be grateful!

I can't be giving up my boot space

Me neither! The boot is one of the things I love best about my squareback!

Edited 26 May, 200719 yr by yellowstripe

I see what you're getting at, but in practice the seals would absorb very little of the bass, if any. Besides - you want the bass to reach you through the air - not through the car. If the car's body is vibrating excessively, it will resonate at certain frequencies giving boomy, muddy bass - not what you want if you're into good sound. In fact I'd say there's a theoretical advantage to having the tailgate isolated from the rest of the car as it may cut down unwanted resonances to some extent.

Hadn't thought of it that way. Definately interested now. Are you down for the doorpod groupbuy?

Are you down for the doorpod groupbuy?

Yes. Looking forward to trying them out, but pretty sure the enclosure will be too small for proper bass...

Is your mk3 a squareback or a coupe? I wonder if the panel/cutout is different inside the tailgate.

what about mounting a sub in the rear seat somehow? or is that a stupid suggestion. I need to lose my sub it whores my boot at the mo! Except I love the bass it gives... :(

Is your mk3 a squareback or a coupe? I wonder if the panel/cutout is different inside the tailgate.

Tis a square.

what about mounting a sub in the rear seat somehow? or is that a stupid suggestion. I need to lose my sub it whores my boot at the mo! Except I love the bass it gives... :(

I've read a story in redline (haha) about someone who had a sub under the rear seat and it set the car on fire, but providing you wire it properly and keep the amp cool there isn't any reason why it should get too hot.

i think you'd struggle to seal it and if you can't seal it it'll leak air and sound pants

how about the rear quarter panels, they would be harder to seal than the tailgate, but there is a lot more room

i think you'd struggle to seal it and if you can't seal it it'll leak air and sound pants

That would be the challenge. We'd need to work out the volume needed as well. I think I'll have a look at the Discovery's tailgate sub system to see how it's sealed.

how about the rear quarter panels, they would be harder to seal than the tailgate, but there is a lot more room

That's something else worth considering, but I think the actual metalwork of the quarter panels would rattle a lot more than the tailgate, even with sound deadening. Worth looking into.

yellowstripe, you've definately opened something up here!

My thoughts up to now...

Rear seat mounting - the issue here is the sub needs to be mounted in an enclosure. The rear seat isn't a box, it's a metal panel with a cushion stuck to it. You can get good results from drivers mounted on a single sheet, but for bass reproduction the sheet would need to be very big (bigger than the car itself...) plus in practical terms it would be very difficult to mount the sub here, there isn't exactly loads of space. So in short, seat mounting ain't gonna work.

Rear quarter panels - there's no reason why this couldn't work well in theory, but personally I reckon the rear hatch is a better bet. The main reason is that the sub itself needs as ridgid and acoustically dead a mounting position as possible. The hardboard panels on the rear quarters aren't really up to the job, and fabricating something better will be tricky as you're looking at a large and awkwardly shaped panel. The tailgate on the other side has a nice flat, roughly square area that could be covered with MDF or ply quite easily.

Sealing it - sealed, or "infinite baffle" enclosures do not have to be 100% hermetically sealed. (In fact this is undesirable as atmospheric changes will make the sub behave like a barometer...) What you're looking for is a reasonable acoustic seal. The advantage with the tailgate over the quarter panels here IMHO is that you can get to everything, so if you want to make sure it's properly sealed it should be reasonably acheivable. With the quarter panels, tracing air leaks will be much harder. In acoustic terms, leaks outside the body of the car (most importantly on the other side of the tailgate seal) will be less critical than those inside the car as the listener will be acoustically isolated from these leaks anyway. However, depending on the stiffness (or lack of it) of the woofer's suspension it may be desirable to have a proper physical seal to help keep the driver under control. In practice though most woofers for car use will have a fairly stiff suspension to allow them to give a decent response in ported, free air, or simply not properly sealed applications.

Has anyone tried to work out the volume of any of the cavities in question?

Edited 27 May, 200719 yr by yellowstripe

Does anyone have a spare tailgate? Would I be stupid to suggest placing the tailgate down, pouring water in until it's full, then draining it and measuring the amount you managed to pour in? I don't know.

I'm going out to the car to pop some trim off and have a look. I'll take a ruler for a rough estimate as well

Ok, there really isn't a lot of room in there at all is there! I didn't bother measuring I just popped the tailgate trim off and went "oh shit".

Ok, seeing as my last idea was shit (was expecting that) this may be the same!! What's the harm in brainstorming anyway..

Parcel shelf box?! Basically fabricate a sealed box under a strengthened parcel shelf and done stealth shelf style.. Problems I can see; Extra weight on parcel shelf supports, large box may be needed depending on sub, its a shit idea anyway.

I'm still into the tailgate idea actually. A pair of 6.5s would probably go alright. I might pull the sub/amp setup out my disco and see what sort of room there is.

Keep your thoughts on the tailgate. The setup might stick out an inch, maybe 2, but that's still a shit load less space lost than having a box in the boot.

Hmm the parcel shelf could be interesting. I wonder how you'd go about properly attaching the tailgate to the mounts though?

Parcel shelf box?! Basically fabricate a sealed box under a strengthened parcel shelf and done stealth shelf style..

Sounds like hard work... shelf mounts are really weak too. Plus I don't really see how this saves space. Your ideas aren't shit though...as you say brainstorming these things is always a good idea. I've been racking my brains to think of where I can hide a sub and so far I'm convinced the tailgate idea's a goodun - bass with the seats folded down and a full load is what I want! The spare wheel well could be good too, but I'm not sure I want to travel with no spare...

Would I be stupid to suggest placing the tailgate down, pouring water in until it's full, then draining it and measuring the amount you managed to pour in? I don't know.

That's got to be the best way to work out the volume accurately as long as you don't mind filling your tailgate with water. Does anyone have a spare tailgate they don't mind trying this with?

Ok, there really isn't a lot of room in there at all is there! I didn't bother measuring I just popped the tailgate trim off and went "oh shit".

Is it really that bad? Give me an estimate... I reckon 10-20 litres would be more than enough for a single 8". I've got a bit of software that will work out the projected response for a given subwoofer (or 2) in an enclosure of a given size.

Edited 27 May, 200719 yr by yellowstripe

It's not good. The plate recess and number plate recess take up all the space in the middle, and either side of that there is about 6-7" square and 2" deep spaces. 2" would probably be enough mounting depth for a 6.5" woofer, and it's about the right width/height. Still very intrigued though.

As for somebody with a spare tailgate, I think there's a few people on here I could PM.

The rear quarter panels are vented along the sills,to allow condensation out. Tailgate idea is cool. There's gotta be a couple of litres in the window surround,and depth would be assisted with a thick mdf panel. Spray the inside of the tailgate with dry-type stone chip protection to reduce tinniness and it shouldnt be too bad. Maybe use some 6x9s with the tweeters disconnected.

I think you'd struggle to mount 6x9s in the tailgate without spacing them out a long way. Which could be a good idea anyway, as it would give more volume. Definately need to work out the volume of the tailgate.

In a mk3 your gonna have a problem gettin a decent volume, a bigger more refined car (deeper tailgate) could work, as he said about discos.

Are you saying the Polo is unrefined

You could be right, but with the right woofer, plenty of power and a little bit of low frequency boost at the right point I still reckon you could get decent results. The enclosure should still be bigger than the door pods and for those of us who need a boot it could still prove worthwhile...

In a mk3 your gonna have a problem gettin a decent volume, a bigger more refined car (deeper tailgate) could work, as he said about discos.

The rear quarter panels are vented along the sills,to allow condensation out. Tailgate idea is cool.

Thanks!

There's gotta be a couple of litres in the window surround,and depth would be assisted with a thick mdf panel. Spray the inside of the tailgate with dry-type stone chip protection to reduce tinniness and it shouldnt be too bad. Maybe use some 6x9s with the tweeters disconnected.

I'm sure there's more than a couple of litres in there, but I have to admit I haven't really had a proper look...just peeked behind the panel. These sound like good ideas, especially the stone chip. Not sure 6x9s will be the best bet, but nice idea. I'm sure you could get a couple of slim 8s in there, especially with a deep baffle to bring them forward a little. Again, we need to work out the volume and do a bit of research to find out what woofers will work best. I might even be able to work out a group buy on something.....