sub in chrysler convertible

Hey guys,

I am really wanting to put a sub in my trunk with out losing all of my trunk space. Special considerations of the convertible are the solid wall behind the seat (leather) that prevents me from firing through the fabric. There is no place to fire up as in a sedan because there is a good 60 lbs of folded vinyl and glass and the situation is exacerbated when the parade boot is on the car. The top is down a whole lot more than it is up. I want to build a single reflex bandpass enclosure that will fit under the top well and between the wheelwells. I built one to fit in the corner between the wheel well and tail light (10 inch) and it sounds great with the top up, but not as good with the top down.

This may sound crazy but I want to know if anyone has experience with this. If I were to extend the port outside of the box (specs call for a 4" dia x 7") and through the back bulkhead, trimming the foam cushion down to the leather between the seats (4" diameter) and running the port to the leather fabric, would it fire through the leather?  Would the leather eventually deform? If the leather is a big problem, does anyone know of a place I could get a 3-4" grill that so that I could trim the leather, tuck it inside the port and cap it off with an attractive grill between the rear seatbacks, ala the rear speaker grills of the 1960s?

And as long as the port is the correct volume, does it matter if it extends outside of the box?

Any suggestions would be appreciated

there should be nothing blocking the movement of air around the port for a few inches at least.  air doesn't go through leather, so it would be in your best interest to make some other plans.  i have put subs in conv's before, and it definately does not sound as good with the top down.  but, none of the speakers sound good to the driver with the top down when compared with the top up.  all of the mechanical parts to the top sit right between the trunk and back seat and block any chance of good bass. i have never done this, but have you ever considered modifiying the interior speaker locations for something bigger and better?  you say you have a chrysler, and if you have a sebring or lebaron , i know the back locations are for 6x8's or 6x9's but can fit a whole lot more.  it would be cool to put some 8 inch speakers back there and components or coax in the front all off a nice 4 ch amp.  nice sound would be all around without losing truck space or losing your mind in the thinking/planning process

just a thought.

did you have anything else in mind?  because if you want anything in the trunk that will make a nice difference with the top down then you might need to take up some space.

someone else give me some advice on this though...from what i have seen in my experience, when the top is either up or down on conv.  they seem to rattle like hell.  about 8 out of the 10 i have seen have this prob.  and the 2 that didnt, had some nice setups in the trunk but the tuned all the way down "because they did not like the rattles"

what do you guys think?

let us know Keith of whatever you do and if it works out, cuz i love tearing up cars and seeing a good reaction.

good luck and have fun brotha

Thanks,  Audifive , for the reply. I didn't think I would be able to fire through the leather, which is why I was thinking about running the port through the seat and flush to the seating area. Being that it is a four seater -2000 Sebring JXi- there is a space between the areas where the rear passengers sit in the one piece rear seatback.

Here is the equipment I am using/have to put in

Stock Chrysler low-level out Head Unit that I will put RCAs on for the amps  /

Lanzar 600 watt 2 channel that will be bridged for the sub/

Lanzar 1400 watt 4 channel that will run the door and panel speakers/

Pioneer (6980?) 6x9 4way speakers front and rear

Pioneer WS 300 12" sub in single reflex bandpass box

My goal is not to shatter plate glass windows, but to be able to enjoy every kind of music that a 42yo likes, from punk to jazz to rap to blues and hear those low bass notes I hear on my home theater system. Have any of you listened to the bass that is in a Sinatra recording? Holy sh*te!

I am not opposed to cutting my car, but I don't want it highly noticeable. My priorities are functionality and appearance:, i.e., I still want room for luggage in the trunk and I don't want to broadcast to anyone that I have something in the car. I had to modify the doors to fit the Pioneer 6x9 four-ways in the doors because they are deeper than the stock Infinity (in name only) front speakers. The same model Pioneers fit great in the rear panels. The result is much better sound with the stock Infinity amp and Chrysler HU, but you don't notice any modification until you listen to it. You see, guys, I don't want someone cutting a 1000.00 top to steal a freaking 300.00 head unit. I stealth mounted a 6-disc changer upright in the console. The only obvious mods to my car are the B&M shifter and the fact it is lowered. I want to keep the thieves moving on to the next ride, where hopefully they will get caught and shot.

I have been playing with the calculator. I am told that port shape doesnt matter so long as the volume is correct- If the suggested 4"dia x 7" port gives me a volume of 87.92 cu in, can I get the same volume out of a 2" dia x 28' port?

Thanks againg everyone for the help

I agree with audifive's reasonings.  Add to that a couple of points:  it's not the volume of a port, but the combined port opening size and length that dictates tuning frequency.  A smaller opening requires a longer tube length.  Use WinISD or similar software to design a vented enclosure.  Second, allowing the port to open to the interior will not increase or improve the bass response.  If it were me, I'd let the sub frequencies travel through the car's body and provide the bottom end to some good midbass woofers ala audifive's suggestion.  Provide as much power and quality that you deem affordable for the project to the amp and subwoofer, build it so that it fires (along with the port opening) towards the rear of the car, and forget about trying to vent to the interior.  You'll feel those sub freqs if you've used the right components.  An amp with a dash-mounted sub controller would be a good idea for that car because of the big difference in sub volume top up to top down.  That would allow you to lower the sub bass response when the top is up.

You would probably regret cutting the car up to allow a small port opening.  I would definitely NOT do that.

Oh yes, include a fair amount of sound damping such as Dynamat in the project.  A well-damped trunk and doors will vastly improve the bass response.

http://www.carstereo.com/help2/Articles.cfm for some good calculators and general info.

Correction on this:  I meant to say that a larger opening requires a longer length, which is the opposite of keeping the volume the same.

yea i would definately ditch the bandpass box and build something if space is limited. 

on the other hand, if you dont mind cutting the leather and putting a port somewhere entering the cabin, then hopefully you dont mind more than 1 person in the back seat.  you will always have to remind them not to sit in front of the port if someone is on that side of the car where the port is.  if you dont care about the back seats, but are worried about theft, then just take out the back seats and make a box that fits back there, and buy some leather and build a simple cover to go over a box when you are somewhere with a risk of theft.  i have seen mdf boxes that have about a 2-3in gap between the speakers and a cover in the trunk that matches the factory carpet.  with a nice permanent mdf/leather coated cover mounted with some screws you will sacrifice only a little sound but it will make the whole thing stealth, sound good without dissapointment, and you wont have to worry about anyone stealing your stuff as much and/or blocking the port. 

i think its worth it if you are considering cutting stuff up and dealing with the frustrations of passengers interfering with your creatiion. 

have you had any new ideas yet keith?

im full of crazy ideas im just too lazy to ever make them happen...let us know whats going on...

Thanks everyone for your suggestions. I think I will go with the port coming through the rear bulkhead and terminating between the two seating areas in the rear. This still gives me the capacity to carry two small children (the only types of people that are ever in the back of the car). The rear seat of the Sebring convertible has a nice 6-7 inch wide area of non-seating no-man's land back there, so I really don't picture port interference being an issue.

To answer some questions:

Why bandpass? I want the bass ported into an area where there will be no interference and where I will not have to use visible dynamat. I am not interested in competition and therefor appearance is more important to me than true sound. If I do not use the trunk cavity to resonate the bassnote, then I do not have to worry about appearance issues with covering the inside of the trunklid with dynamat, though I will surely consider it for the inside of the doors. Regarding the doors, should I be covering the inside of the door skin, the inner  metal panel that the door trim panels attach to or both?

I honestly think that the single reflex band pass box built to the volume and port specs laid out by the speaker manufacturer will meet my needs, with the mid-bass being handled by the 6x9s. Both of my amps have remote bass adjustments and I will use them. I also have an MTX active crossover in the loop. I think this project is going to look and sound awesome. I will bench test the box before I cut the leather and I will try to put together pics of the project.

Thanks again for everyone's help. What an awesome resource this forum is. Keith

One more question y'all. Does the sound absorbing material only go into the sealed chamber (back of speaker frame or both sides (including ported chamber)? The diagram shows only on the sealed side, but it never hurts to ask.

Thanks Again! Keith