I found this site today and it looks like a lot of people around here know quite a bit about audio! Hopefully I can get some help / opinions here as I am about to design & build a new box for my car.

I have 2 Infinity 1230ws (4ohm) which I have to build a box for. This is going to be going into my own car, a 2000 Subaru Legacy. This vehicle does not have a fold down rear seat, just a "pass-through" centre armrest in the rear bench.

First things first, I'm planning on building a sealed box, 2.5 ft^3 as recommended by Infinity. My aim is more towards sq than spl.

As opposed to firing the subs to the rear of the car as they are traditionally done I thought of a way (or I think I did) to get all of the sound into the passenger compartment of the car.

My idea is to fire the woofers towards the back seat and force all of the pressure from the subs into the cabin through the lowered pass-through in the bench (I would always have this down except for the rare occasion in which I carry 4 passengers with me)

I would accomplish this by building a standard sealed enclosure and pointing it towards the seats, but build sort of an additional enclosure infront of the woofers which "contains" the bass except for a hole the size of the armrest, which would allow the sound pressure to travel into the cabin. This would be similar to a bandpass design except with a bigger airspace and a larger opening which is not a port.

Has anyone ever done anything like this before or have they seen it done? Is it even worth exploring? If not I guess I'll do the tradtional sealed and point backwards. I'll try to work out an actual design this evening and post it up so you can have a better idea of what I'm talking about.

Hopefully this is an acceptable first post, thanks in advance for any help.

 

Here's a dwg that I made up quick. I hope you can read it alright and understand what's going on.



Two benifet that I thought of associated with an encluse like this are 1) no damage to the sub by using the trunk (which I will be doing regularily), and 2) Theoretically there's no need to dynamat the trunk because there's no air movement in there.

Like I said, if you guys don't think it's going to be good then I'm just going to build a standard box to take up as little room as possible.

I'd like to hear what you think as I'd like to build the box this weekend.

Thanks.

 

I use a similar method of construction to this all the time and have had great success with it. What you are basically making is a funnel that channels all output into the cabin. I make my sub box with the front baffle sunken into the box by 1". I do this so that it is easy to attach the box to the funnel. I then take a 2" aluminum flat bar and attach it to the 1" lip on the box on all 4 mounting surfaces. Put the box in and press it into the funnel. Next reach through the funnel opening in the seat wall and screw the flatbar to the funnel. Attached good and solid and a invisible seam on the outside.

 

Cool thanks, I *think* I know what you mean by the flat bar and 1" inset baffle.

So this should work then. Will there be any type of port noise or is the "chamber" and the opening through the seat large enough that that won't happen? In the rear seat attached to the pass-through there is a fold down armrest for the rear seat occupants.

I was planning to try and keep it so that the armrest would remain for the rear seat occupants and removed the rest of the passthrough and cover it in grill-cloth so it just looks like the rear seat armrest is folded down for use, not the whole passthrough.

This would be much more stealthy installwise and comfortable for rear seat occupants (I often have 2 passengers). This way would allow for an opening through the rear seat of about 12" tall by 8" or so wide vs. the 9" by 15" of removing the armrest and passthrough all together. Would this restric the air movement from trunk to passenger compartment too much?

Another question about plexi... would the front face of my box be too big to make with plexi, so that from the trunk you can look into the box and see the front of the woofers? How much does that type of material usually cost and what should I look for? I've never used plexi before in a box design.

Thanks

 

That is a good size opening in the funnel. I highly doubt that it will add noise to the overall output of the drivers. I have never encountered noise in my systems. If you are going to use plexi or acrylic, use a minimum of 3/4" as it is not as strong as mdf is. Layer some foam tape onto the edges of the box to ensure a seal between the box and the plexi.

 

Ok thanks! I guess all there is left to do is try it! I might ditch the plexi though, MDF is stronger, it won't look like there's anything in the trunk.

I'll probably make a minor change to the design though... mount the subs traditionally instead of inverting. That way if I don't like the sound I can just flip the box around and point it backwards.

Unfortunately I don't have a surplus of $$ to use on box material to try different setups.

I have received a suggestion to build a ported enclosure for these particular woofers. Is it possible to build a ported box that sounds "tight"? (I like tighter bass) Or should I just stay with sealed.

I am not so much concerned with volume as I am smooth an clear bass response.

 

Leave it sealed unless you can get the ported box volume bang on and have the right port displacement. A sealed box is very forgiving as to tonal response, with this type of box I prefer a sealed enclosure but have had success with a ported box as well. My next on that I am doing in a 04 BMW convertable is a dual 10" sealed type.

 

Sealed for Sq is the way to go, as stated above if you dont have the port tuning just right you may miss out on some notes

 

Here's an update: Things ended up working out different for me. I traded my 2 1230Ws for 2 1030Ws which is what I really wanted in the first place but couldn't find.

I built to separate sealed enclosures (@0.75 ft^3 ea.) to face towards the rear of the trunk and to sit on either side of the rear seat pass through. The boxes are built to sit right against the back of the rear bench seat and I have positioned my two amps in the 2 rearmost corners of the trunk (behind the tail lamps).

After thinking about it this setup was the most practical for me. It took up the least amount of space, added the least amount of weight to the car, easily allows me to remove one of the boxes to fit my mom's wheelchair in the trunk if I have to, and keeps the rear seat passthrough unmodified and fully functional. It was also the cheapest, important for a guy still in school.

It took me all last weekend to decide where I was going to put the amps, build the supports, design and build the boxes. Everything is roughed in right now and I pretty well have my whole trunk availible! So far I'm very happy with it. Nothing is carpeted yet. I have to put the backs on the boxes tonight as I sealed the front and side panels of the boxes last night.

This weekend is going to be busy... I have to carpet the boxes and amp supports, do all the wiring for my sub amp and new 4 ch, and install a pair of Infinity Reference 6.5" coaxs for the rears which I picked up to match my Reference components up front. Its jobs like this that makes me wish I had 2 sets of arms. Or at least a buddy who enjoys doing this stuff as much as I do lol.

My hope in the end is to have the cleanest sounding system I've ever had.

 

It sounds like you're on the right track.....

P.S. If you put where you are in your post, you might get a PM from someone who does enjoy doing this as much as you do....and has some time to spare to help you out......