2013 Mercedes Benz SLK 350 (R172) - 12" Spare Tire well install

[SLKSonic]

Hi everyone.

I'm a bass head, always have been and always will be. I find the R172's lack of low end disturbing, so I plan on doing something about it. I don't expect to shake the earth but it would be nice to fill in the sound.

I researched the passenger footwell sub installs. Those are pretty cool, but not enough bass for me, I don't think. I've considered replacing the 8" woofers in the doors but that would look ridiculous for anything other than a 2.5" shallow mount subwoofer, which, lets be real... probably wouldn't get as much bass as even the footwell sub mods. I considered altering the door panel and replacing that sub as well, but it would look really bad. At one point, I mocked up a box to try and fit behind the seats... no dice. And finally, I have no idea what's behind the wall... so cutting is not an option.

That leaves the trunk.

I've found some nice prefab boxes that will fit under the parcel shelf in the trunk. Even a ready made kit that would fit. These would take up a lot of trunk space, though. So far, they're my second strongest option. So, what about the spare tire well? Apparently the spare tire is useless without additional gear, so why not remove it and use that amazing space as a sub box? I could even mount an amp in there, plexiglass windows and some nerdy LED lights. Let's try that.

I'm thinking I have two options, but I haven't been out there to look in the trunk for a good while yet so I'm just shooting in the dark here. It's 1am and I don't feel like pulling my car apart.

1) Wood floor. This would require precise measurement and some serious wood work to pull off. The results would be the best, though, I think.
2) Metal floor. This could potentially be accomplished by using vertical pieces of MDF adhered to the metal trunk floor. Dynamat the inside for better sound absorption.

Sealed vs Ported
I'm thinking with this amount of space, a sealed box would be best. Plus, given the sound has to travel to the middle of the car before it's heard, the tight response of a sealed box would sound best.

Speaker Size
I'd love to do a 12"... but I don't think I'd have space. I could probably have a solid 10" sub and it would sound great, especially with what they can do these days with subs.

That's it, really... I may take some measurements, do some mocks, sketch some ideas... only time will tell. My father in law has been a carpenter for 40+ years, so I should be able to enlist his help to pull this off. Wish me luck!

P.S. DJ Magic Mike told me there's no way I can put any decent bass in an SLK. He's a fellow droptop Mercedes owner (SL) as well, but I feel I need to prove him wrong.

 

[huberoy123]

Hi everyone.

I'm a bass head, always have been and always will be. I find the R172's lack of low end disturbing, so I plan on doing something about it. I don't expect to shake the earth but it would be nice to fill in the sound.

I researched the passenger footwell sub installs. Those are pretty cool, but not enough bass for me, I don't think. I've considered replacing the 8" woofers in the doors but that would look ridiculous for anything other than a 2.5" shallow mount subwoofer, which, lets be real... probably wouldn't get as much bass as even the footwell sub mods. I considered altering the door panel and replacing that sub as well, but it would look really bad. At one point, I mocked up a box to try and fit behind the seats... no dice. And finally, I have no idea what's behind the wall... so cutting is not an option.

That leaves the trunk.

I've found some nice prefab boxes that will fit under the parcel shelf in the trunk. Even a ready made kit that would fit. These would take up a lot of trunk space, though. So far, they're my second strongest option. So, what about the spare tire well? Apparently the spare tire is useless without additional gear, so why not remove it and use that amazing space as a sub box? I could even mount an amp in there, plexiglass windows and some nerdy LED lights. Let's try that.

I'm thinking I have two options, but I haven't been out there to look in the trunk for a good while yet so I'm just shooting in the dark here. It's 1am and I don't feel like pulling my car apart.

1) Wood floor. This would require precise measurement and some serious wood work to pull off. The results would be the best, though, I think.
2) Metal floor. This could potentially be accomplished by using vertical pieces of MDF adhered to the metal trunk floor. Dynamat the inside for better sound absorption.

Sealed vs Ported
I'm thinking with this amount of space, a sealed box would be best. Plus, given the sound has to travel to the middle of the car before it's heard, the tight response of a sealed box would sound best.

Speaker Size
I'd love to do a 12"... but I don't think I'd have space. I could probably have a solid 10" sub and it would sound great, especially with what they can do these days with subs.

That's it, really... I may take some measurements, do some mocks, sketch some ideas... only time will tell. My father in law has been a carpenter for 40+ years, so I should be able to enlist his help to pull this off. Wish me luck!

P.S. DJ Magic Mike told me there's no way I can put any decent bass in an SLK. He's a fellow droptop Mercedes owner (SL) as well, but I feel I need to prove him wrong.

DJ Mike may have a point. Not much space in the SL. I have Clarion speakers SRG6833C in my upper doors to complement 6.5" speakers in the lower doors, and 2 -12" subs in the trunk. The Clarions do a really good job with the bass, in my opinion. Look up the specs. Let us know how you make out with your project. Good luck.

 

[hispls]

Using the spare tire well for a subwoofer enclosure is for stealth/show, not so much for sound.

Drawbacks include cost of building it up (fiberglass is expensive and you'll need it to optimize your airspace). Carpentry will definitely require a good cabinet making tool selection to cut precise small pieces, and that's just not the optimum location for a subwoofer in a trunk. You're also quite limited on space and adding a port may not be physically possible, though if your sub performs well in a sealed box this is a non issue.

Really though at the end of the day the biggest battle is just trying to get the sound up out of the trunk and to your listening position, trunks are just awful for this. To really optimize you must completely seal off the trunk from the cabin and have the sound injected into the cabin side somehow. Best option is a bandpass box ported up the rear deak or through the ski hole in the back seats or similar. If you have a sub that works well in a sealed box you can get similar response with bandpass and port the sound directly into the cabin, if you know a good carpenter building that wouldn't be all that hard.

 

[SLKSonic]

Using the spare tire well for a subwoofer enclosure is for stealth/show, not so much for sound.

Yeah, it's primarily because I didn't want to surrender a ton of my limited trunk space. Beyond that, the tire that comes with the SLK is a "space saver tire", aka deflated. Most of them didn't come with a pump or jack/tools. I found out mine did after taking it apart but I still don't care much about a spare. But it really comes back to the fact that I'd like to save some space.

Drawbacks include cost of building it up (fiberglass is expensive and you'll need it to optimize your airspace). Carpentry will definitely require a good cabinet making tool selection to cut precise small pieces, and that's just not the optimum location for a subwoofer in a trunk. You're also quite limited on space and adding a port may not be physically possible, though if your sub performs well in a sealed box this is a non issue.

Really though at the end of the day the biggest battle is just trying to get the sound up out of the trunk and to your listening position, trunks are just awful for this. To really optimize you must completely seal off the trunk from the cabin and have the sound injected into the cabin side somehow. Best option is a bandpass box ported up the rear deak or through the ski hole in the back seats or similar. If you have a sub that works well in a sealed box you can get similar response with bandpass and port the sound directly into the cabin, if you know a good carpenter building that wouldn't be all that hard.

Oddly enough, my trunk passes through to my cabin via the "rear deck". The SLK stores the roof in the trunk (which also limits space when the top is down). I may have a vibrating flap to worry about, but I'll cross that bridge when I get there.

My father in law has been a master carpenter for 40+ years (he's built houses used in movies, etc) and has agreed to help out.

There may be an opportunity to port through the back wall, as well. I've heard rumors of it being done.

 

[SLKSonic]

Let me propose a different idea.

First off, my goal is to have a little more than bottom fill in my sound. I would like to have some solid low end bass. That said...

In the passenger footwell, there's a decent piece of styrofoam under the carpet, and behind that is a steel plate and a small void where some SLK owners place a powered sub... the kind meant to go under seats. When it's all back together, there's no loss of passenger foot space. Since this car is a world car, that space is for the pedal assembly on RHD variants of the car.

I'm not sure how big the space is, but I can check. I wonder if it would be possible to squeeze a small cabinet under the carpet and remove the steel plate? And skip the trunk altogether? It would be about 12x10x4 if my guess is correct.

There are already 8" woofers in the door (With like 2.4" total height), driven by the factory amp. They sound okay. I thought about upgrading those but there just isn't enough space inside the baffle.

Here are some photos of the area from someone elses install. He opted to put his sub on top of the plate and cut out the foam. He said it sounds great and fill sin the sound, but he also doesn't have the upgraded stereo option in his car like mine does. It probably sounds like my stock 8" door speakers.

 

[SLKSonic]

Meanwhile... this guy installed a sealed JL 13.5" in his trunk and said it sounds phenomenal. There's a factory cover that goes right over top of this and you'd never know it was there. That may end up working better than a false floor with plexi windows

 

[1aespinoza]

this guy installed a sealed JL 13.5" in his trunk and said it sounds phenomenal

I can attest to the power output of this sub. It hits hard and sounds deep. It only requires a 0.8 cubic foot box. On top of that, I was only using a 750 watts amp on two of these bad boys and they sounded awesome.

 

[winkychevelle]

Meanwhile... this guy installed a sealed JL 13.5" in his trunk and said it sounds phenomenal. There's a factory cover that goes right over top of this and you'd never know it was there. That may end up working better than a false floor with plexi windows

View attachment 46161

You claim you want to spend 3-400 then post a picture of like 2 grand in gear alone. That sub is 599 alone.

Can it be done yea but your gon a struggle with such low budget. I would be looking at doing a custom box on the passenger side foot well with a shallow sub either the hertz or and alpine. But those are expensive.

 

[SLKSonic]

You claim you want to spend 3-400 then post a picture of like 2 grand in gear alone. That sub is 599 alone.

Can it be done yea but your gon a struggle with such low budget. I would be looking at doing a custom box on the passenger side foot well with a shallow sub either the hertz or and alpine. But those are expensive.

I was posting to show the install, not the price of the gear. The space is there, so that's good. And yes that JL is much more powerful than the baseline XTR setup I'm considering.

I'm planning on measuring the space in the passenger footwell to see if I can consider a Fosgate P300-12, a Fosgate P300-10 (or their "truck" variants... these would have to be mounted upside down) or even a Kicker HS10 or Cerwin Vega VPAS12. It would just come down to how much space I would lose, but a sub in the cabin would definitely sound better and the all-in-ones are more compact and cost efficient overall.

We'll see.

 

[winkychevelle]

I was posting to show the install, not the price of the gear. The space is there, so that's good. And yes that JL is much more powerful than the baseline XTR setup I'm considering.

I'm planning on measuring the space in the passenger footwell to see if I can consider a Fosgate P300-12, a Fosgate P300-10 (or their "truck" variants... these would have to be mounted upside down) or even a Kicker HS10 or Cerwin Vega VPAS12. It would just come down to how much space I would lose, but a sub in the cabin would definitely sound better and the all-in-ones are more compact and cost efficient overall.

We'll see.

Personal experience here the Rockford p300-12 was junk and really put out very little bass. I'd expect the 10 to be even more pitiful. I had 2 6.5subs in a ported box on 1000w that would destroy either of those Rockford enclosures in the same size box.

 

[hispls]

In the passenger footwell,

Excellent for good sound stage and imaging, don't expect it to move your mirrors or anything. Honestly with what you're trying to do just doing up the spare tire well would be best. It'll give you some low end whatever you do and from there if you absolutely have to have more bass you could always buy a more robust sub, inverse mount it and just brute force the job with more power.... the tradeoff being money and trunk space.

 

[SLKSonic]

Excellent for good sound stage and imaging, don't expect it to move your mirrors or anything. Honestly with what you're trying to do just doing up the spare tire well would be best. It'll give you some low end whatever you do and from there if you absolutely have to have more bass you could always buy a more robust sub, inverse mount it and just brute force the job with more power.... the tradeoff being money and trunk space.

Thanks. I'm gonna go with a ported 12. I more than doubled my budget for it and gonna go something midrange. I won't lose any trunk space, only the spare. If I end up only adding some low end, I'm okay with that. The woofers in the doors are nowhere near low enough to round out the sound.

 

[hispls]

In the passenger footwell,

Excellent for good sound stage and imaging, don't expect it to move your mirrors or anything. Honestly with what you're trying to do just doing up the spare tire well would be best. It'll give you some low end whatever you do and from there if you absolutely have to have more bass you could always buy a more robust sub, inverse mount it and just brute force the job with more power.... the tradeoff being money and trunk space.