Hey all...Im looking at upgrading my stereo...not sure if Im gonna get a new head unit...but I want to put an amp and sub in. Can you guys post some pictures of your sub setups in convertibles. I saw some passenger side stealth boxes online. I dont think they are a sponsor, so i wont say their name...but what do you guys use???


thanks

Kurt

 

I might buy this box, and definitely would if I wasn't such a cheap bastard...

http://members.aol.com/jbslim003/myhomepage/sale.html

 

Does anyone have one of these systems in their car? Well other than Johnny B???

 

JB's system looks cool but I wish I could hear it in person to see what it sounds like.

 

me too.....or anyone's with a convertible......

 

Well I have just a 8 inch Kenwood powered Basstube in mine and with the top up it sounds great, with the top down don't expect much. Maybe if you had a couple of 12's back there but you'd be doing it more for others.

With the top up it sounds just about as good as it would in any other car. I had a MTX stealth box in my WS6 coupe and it thumped pretty good, everyone thought I had a couple of 12's back there

 

I got one of JB's boxes, it's worth every penny. I've modded mine a little bit and I'm also working on a solution for the bass being blocked when the top is down. Can't wait until it warms up a little to try it out.

JB is a little flexible in the making of the box, and will talk to him about my mods if they pan out. The basic idea of the box is the best execution imho for a vert. There is so little trunk space to start with I didn't want to lose any.

If you have a JB box or similar already this is what I'm working on:

- I have 4x RF Stage 1 8" subs in mine. As delivered it is only .18 cubic feet per sub. I modded up a divider from 1/2" stock to create a slot port about 4.5" long, and then blocked it half off. This drops the tuning frequency from around 200Hz down to around 80Hz. A big difference and it definitely shows in the sound. I consider this to be mandatory. Also since the tuning frequency is so much higher than normal it makes it pretty important to use an amp with a subsonic filter, fmods, or a head unit with a subsonic filter.
- Yuo can also have the box built for two subs and double the volume to 0.36 cuft per sub. If I wanted only accurate fill that'd probably be the way to go and then you could tune the box to 40-60Hz or whatever you want.
- The last thing I'm working on is a short slotted spacer for the top to rest on in the down position. The trunk cavity gets blocked almost 100% when the top is down. If you take your hands and pick it up off the shelf even a half inch it has room to get through again and picks up probably 6-10db in level, more like with the top up. Obviously this is very touchy, but I think it can be done with no risk to the top glass. I have to wait for it to warm up to tinker with though. Trust me if this all pans out I'll post plenty of pics.

 

Well, it warmed up enough around here that I got my setup pretty much dialed in.

- I picked up a Memphis Belle "Baby Belle" amp off eBay for $150. 55x4+400x1, and made a little amp rack with a flip lid so I can still recklessly toss **** in the trunk. Tonnaue cover still fits in the trunk just fine, with room left for a couple duffles and small bags.
- I have a JBslim box I added 4 plates to, which cut the slot sizes in half and created roughly a 5" long slotted port for each sub. Also added a couple handles, a terminal plate, and grilles from partsexpress.
- The box is loaded with 4 RF Stage 1 subs I got from Crutch for $160. Box is wired to 1 ohm.

As-is, it's pretty nice. It hits as hard as any sane person would require (enough to annoy the gf), and top-down you can still get very accurate and loud bass, but it is not booming like in a hatch, there is just not as much enforcement and the enclosure isn't ideal.

But, because the whole top is down the car's going to make a very nice portable stereo for outdoor stuff.

Top down driving, it becomes merely accurate bottom-end fill. Bass heads wouldn't be happy.

However, the subs are not getting enough power. If I could go back I think it would probably be pretty close or better to use just 2 subs and double the volume for each, allowing for enough room to tune the box down to about 50Hz and giving the subs the right amount of enclosure space. I think it'd hit really hard if I had say a full-size Memphis Belle with the 1000 watt D channel, but I don't want to mess with electrical upgrades so no more amps are in my future. I would really like to hear it with that level of power though. I'm sure it'd be killer.

The idea about using a slotted spacer to keep the top off the shelf floor a little, well, I didn't realize how hard the top glass is forced down when the top is fully dropped. So that idea is a no-go. Oh well. If you could limit the travel of the top hydraulics, then this might still be feasible, but I'm not going to mess with it.

All in all, I'm happy so far. No sacrifice in space, costs in line with a similar hatchback setup. I think it's a good solution, but I would really like to see/hear a convertible with two 6.5" or 8" tubes mounted on the shelf in the same area. I think you could get pretty comparable results with alot less work because the transmission line enclosures of the better-made tubes do such a good job making the most out of smaller subs.

Just something to consider if you're trying to avoid the battle ax approach. My top does not rattle. My trunk lid does not rattle. My car does not rattle.

 

looks good. have you thought about running a cheap fan and an air gap at each end of your flip down lid for cooling? Just a thought since your closing in that small space. I'd like to do something for mine. Probably upgrade the stock speakers. I'd like to add subs but I like my trunk space too. Thought about putting something in place of the rear seats, but again, I'm cheap and already have too many projects anyway.

 

i had one in mine that just sat in the trunk perfectly and i had a buddy fab it up and carpet it i will try to see if i have some pics

 

I just installed a box of my own design, sort of similar to johnnyB's, in my TA a couple days ago and it sounds great. Two high excursion (24mm peak to peak) 8" drivers in a ported box, tuned to 40Hz (in car responce goes quite a bit lower), with 100 watts per driver (drivers can take 150 to 200 watts each easily). My radio shack SPL meter regestered 118db with the top up, for comarison, it only regesters 100db without the subs. I know it isn't an accurate measuring device but it is good for getting a rough estimate of performance. With the top down it can be heard but not nearly as well as with the top up, which isn't too suprising really. I will get some pics up sometime, unfortunately my car got hit yesterday so it may be a while. I have some rough CAD drawings, if anyone is interested in building the design I could probibly be persuaded to clean up the drawings and write up some instructions with some tricks that make it pretty easy to build. It does require several angle cuts, and you will need a table saw, but it is only 6 pannels, anyway, if anyone wants more details let me know.

 

very cool...please email dwg files to jayofalltracks@yahoo.com.

 

oh and no need to clean them up by the way, I can do that part.

 

Nice writeup Todd, thanks.

Did you have a chance to notice any difference w/ the ports blocked vs. non-blocked? Just curious. Seems like the efficiency of the port would be somewhat proportional to, or at least limited by the port area. I should just get off my **** and go out to the garage and try it myself.

I've been thinking more about your idea of lengthening the port, and have come up w/ an idea I might try. Basically adding a panel behind the magnet that blocks 1/2 or more of the "wedge" towards the port, when combined w/ a 1/2 blocked port, it would create a zig-zag path between the sub and port. Also thinking about how to maximize use of both volumes for 2-sub applications using similar zig-zag path techniques to maximize port length.

 

I will clean them up a little this week to make things more clear for you, right now there are multiple versions and a lot of stray linework in the file, but don't worry, it will probibly still be a pretty ugly when I give it to you

Also I draft in microstation (.dgn), I can convert it to autocad (tell me what version you are running) or I can make a .PDF to avoid any conversion issues, whatever you want, let me know.

 

I run acad 2002 m6 and also have solidworks 05 at home and 05 or 06 at work, not sure, don't use it much. 2002 or earlier .dwg format would be perfect thanks.

 

Johnny,

If you build the box up for only 2 subs, with double volume, there should be more than enough room to make the port long enough to tune down to 60Hz or so. I don't know if I would go much lower than that for 8" subs, but I guess it depends on the subs/power/goals. I can say that you'd need to have some pretty high quality subs with alot of power behind them to make going for 40Hz sensible in this arrangement.

I'm not an expert on box design, and I know there are some "fine" aspects of port tuning that you'll need to consider. Pinching the port cross section off too much, or giving it too many sharp edges to flow around can introduce the risk of some port noise.

On top of that you have to consider keeping it as a very simple change, requiring the smallest amount of wood/cutting/ chance for mismatch. I'm not a carpenter and that's the main reason the single plate idea was attractive to me. Outside of just keeping the sub volume up, wood costs and mass down, it just starts getting really complicated to fab up.

If you set the box up for two subs, left one port out, and made the remaining port into a 7-8" long slot port with the "add a plate" method, I think you'd end up right around 60Hz, and it should work out really well.

In a four sub box, 80Hz is probably the lowest you are going to get. Adding more wood takes up valuable enclosure space, which is already at a premium.

Again, these are just my opinions. Given the arrangement of the car, and especially considering top-down, I just don't think it makes sense to target the box at anything less than around 60hz.

Mine could hit really hard with the right power. It's going to drive me nuts thinking about that over time.

Has anybody here ran a true 1000 watt class D amp on a factory charging system

 

i have 2 10's mounted flush facing up in the trunk where the t tops would usually go. it sounds great with the top up but when the tops down you cant hear the subs.

 

80hz? What the hell are you trying for, midbass? I would never tune ANY enclosure for a subwoofer any higher than 40hz, unless I was trying for a peak number.

In open air enviroments, bandpass enclosures are the best bet... but if you're trying to stuff them in the trunk, then vented is the way to go -- I just can't see tuning so high. You will likely be better off with SEALED if you cannot make the space for a properly tuned vented box.

Check out the Elemental Designs Eu-700's, they are only 6.5's and they deliver solid bass in a very small space. VERY small, and very loud for their size.

 

80hz is better than 200hz, which is where it started, and sealed won't work in this arrangement. Your points are valid but they don't apply to the box approach I am locked into right now.

Also 80hz isn't INSANE, it just isn't ideal. 8" subs are limited at the low end, and most of the music I listen to doesn't have a lot of content at 40Hz.