Contour Enthusiasts Group Archives Forums Modifications Audio Conversation w/ an ex installer of a shop

Ok, guys I think this is a good one here. I have been trying to do alot of research here into what type of subwoofers I want. As I was talking to another co worker (which yous to be an installer for a local shop. very good reputation)that has a Honda Accord with 2 15's JL's. I was explaining what type of design I wanted in my car and so he started looking in my trunk and he looked at me and said "you f***ing *******." Of course I said what the heck are you talking about he said "you have the most perfect car aside from a hatch back" now this might be old news to some but to me its new and good news to me . We in our Tours have that one port in the back dash that I guess was used for a subwoofer. Well, as for what he was telling me is that I can get 1 JL subwoofer 15(w3) and put in a bandpass box that is tuned with a bandwidth of 42-89hz and reverse the port sticking into the subwoofer hole in the back dash, that would create what we all know as a hatch back effect. The sound is hitting the back windshield and bouncing in to the cabin. Now that would eliminate most of the rattles in my trunk, But before i get started on this project does anyone have something like this set up and if not what are the thoughts of doing something like this do I have any gains or losses (of course my hearing IN THE LOSS)to this type of set up?, or instead of using a JL should I use a kicker xpl.

First, I don't recommend ported boxes in cars unless you are competing. In this example, below 42Hz, it will be very easy to excede the xmax of the drivers. I don't know what kind of music you listen to, but it's very possible if you like deep bass. Next, not only are band passes are hard to perfect with a retangle box, let alone trying to use a port size you already have.

As for sound bouncing off the rear window, bass doesn't bounce too much as the wavelengths are large. But, a port into the cabin would be a little bit louder.

I don't mean to discourage you, but it's a lot of work to get it sounding right. If your friend is willing to take the lead, go for it.

Aaron

I've thought about doing something like this using a pair of subs. I took some measurements and tried to sketch out some feasible enclosures. Here are the most likely problems you'll run into:

(1) Box design - It's not the easiest thing to put together a bandpass box that will sound good. You'll definately want to put a lot of thought into this, as hours and hours of work might be all for naught.

(2) Space - The actual logistics of the woofer placement will eat a ton of trunkspace unless you can get really creative. However, a single sub should be much easier as opposed to the pair that I was considering.

(3) Permanence - Are you even going to be able to access the spare tire with that sub enclosure in there (assuming you're planning on attaching it to the underside of the rear deck)?

Not to be discouraging either, but this project will need quite a bit of engineering and fabrication to surpass putting the sub in a sealed box in the trunk and loading one of the rear corners.

I'd suggest taking some measurements and see what kind of enclosure you can come up with that will work with either of those subs to see how feasible it is.

-C

I want to add that the so-called hatchback effect has more to do with the space in the car than bass bouncing off anything like trunk walls, windows etc. A typical hatch has somewhere on the order of 100-120 cu ft while mid sized cars have closer to 150 cu ft. What happens is the transfer function occurs at a higher freq.

As the others have said, bandpass boxes can be made to sound good, but it isn't easy.

by the way it has been proven over and over that as far as sound is concerned SUV's just cannot be beat. the sound waves reflect of the rear glass and amplify in doing so. maybe you mean that contours and hatchbacks are best as far as actual CARS are concerned...

mike

Really? Never heard this correlation before. How come so many cars win IASCA events?

I could see how a very large car or an SUV would have an inherent advantage in setting up a car to provide excellent imaging, but that would not have anything to do with reflecting sound off the rear glass. If you are talking about the best car for huge SPL, I personally don't think you can beat a hatchback (particularly an early 90s CRX and a 87-93 mustang, both of which exhibit cabin gain on the order of 30 dB.

You might lose the rattle from your trunk but now the back glass is going to rattle. I have 3 10's in an enclosed box firing forward and they make my glass rattle. I put a friend of mine's 2 15's (JL W-4 I believe)in my car and I think that I had to tighten everything down afterwards. My car is not suited for that much abuse. My 10's do enough.

Well I think JL has made it pretty easy for me at this point in there website they have the specs for this speaker in a bandpass box config. (for one only ) it shows the box being 17x16x31.0. Pretty big size. Access to the spare tire (heck who needs one....LOL ... I probably just jinks myself) I am going to try to make it with out it. No choice when you invade the trunk like that. I will be using a jbl 1200.1 amp. So if that is not a good idea should I just go with a sealed box facing into the cabin. would that be the best?

For best in-cabin bass response, you'll want to face your subs towards the back of the car. The bass waves will "load" in the corners and reinforce each other, or something like that. I'm no enginerd. But, it works.

IMO, you will slightly surpass a sealed enclosure in SPL (if the box turns out perfectly), but it probably won't sound as good.

ok first, my friend used to have this done in his 91 maxima. 2 JL 12w6's in a bandpass with a custom port through the rear deck. like everyone said, it has to be built exactly the right specs. To this day, my friends setup is one of the best I've ever heard. I watched the shop build the box and it was very difficult. It was so big that they had to build the second half of it while the first half was allready in the trunk. If you can't get it done right, i would say go for it; the results will speak for themselves.