I humbly request advice for my next wall

[Polar-bass]

Allright, I have been lurking around and reading here for a few years. Now it is time to rebuild again and I Need some Inputs from the infinite combined wisdom of SMD.

I currently have a C-pillar wall with 4 15s (woofers are pretty damn similar to American bass, but named differently from my importer). I am running them on a good 3,5K each. I have a decent electrical with a mechman 220alt, 4 odessey 2150s and two 1750s under Hood. A second alt would pretty f... expensive since nobody here (in Norway) dares to build me a dual alt bracket.

So I want to get louder, I did manage 151.9 with very limited testing, at around 31Hz with current Setup on Music, some small gains could have been made with further testing, but I wanna rebuild anyway!

The Goal is a daily ground pounder with more or less current amps and electrical that will Play Music well down to high 20s.

The car is a 2006 Mitsubishi Pajero with only the two front seats. I can do up to 23 cubic feet with a C-pillar wall. But there is a but, I can't fit four 18s in a baffle because of the rear "wheel-shapes" poking up. However I am a real sucker for cone-area! That leaves me a couple of Options:

- three 18s (and run them on 3 out of my 4 amps)

- two 21s, now will the IA DPs handle 7k rms each??? I have some doubts here.

- 6 to 8 12s, this is probably more expensive.

- do the crazy Option of walling it between the C and B-pillar. This could be done by lining the baffle up with a Separation between the two Windows that make up the window part of the rear doors. this will certainly make sealing it completely much more difficult. It would not be directly up against glass. What it would give me is bigger baffle area, so 4 18s would then be possible.

If this is all too confusing I will post explanatory pics. Let me know any thoughts on size, number and possibly brand of woofers for the Setup.

[hispls]

You really think you have enough box volume for 4 18's? Bear in mind 6 15's is the same cone area and if you like your 15's two more of those isn't a big investment as opposed to replacing everything.

You never mentioned what amp(s) you have, but no single sub would take a real 7KW for very long. Mechanically they'd probably hang but the coils would melt quickly.

Have you considered doing a W or V shaped wall to fit more cone area? How about port area? Will you have adequate room for a port after all those woofers are up?

To clarify, you have 20+ cubic feet now or if you bring it up to behind the front seats?

[RooTxBeeR]

You could grab 2 more 15's make it a clamshell, 3 on each side.

[Polar-bass]

Thanks for quick Response!

hispls:

Not sure if I agree that 6 15s will give the same cone area as 4 18s, by my quick calculations the 15s will be just slightly more ( I might be wrong here). Of course adding two 15s is cheapest, I could run them on three of the amps. Or buy two more amps which makes it the most expensive alternative.

The amps I run are 3500 rms @ 1 ohm. I guess not quite as good as soundqubed's 3500.1s. They are branded from the importer so I cannot say for sure which other brand might buy their amps from the same factory. They look very much like crecendos but state somewhat higher output in their specs (but at 14,4v instead of 13, I think we can say they are pretty much the same.

About the DP 21s handling up to 7K, sure not many Subs can take that for a Long time, but who Plays full tilt all the time? I am currently running over twice the recommended power to my 15s without Problems. I was more curious if anyone had any good or bad experience with those massive Subs? Not too many builds, and even fewer with numbers.

Clarification: I will have 22-23 cubic feet by rebuilding and walling at C-pillar, current Shell is around 20 cubic feet.

And yes I have of course taken desired port area into consideration when debating my Options. I am Shooting for 350 to 400 sq in port.

RooTxBeer:

I have considered a clam and some "semi clam" with horizontally divided V-shaped parts of baffle where subs are mounted, and the port in centre without that V-shape. This is complicated and even worse if the outer Shell is not more or less square I am afraid. - I have only the experience of one flat wall build so far. A true clamshell seems pretty tough.

Something like THIS build, which I saw here on the forum some time ago, i believe it was a sedan:

Any thoughts on the crazy idea of walling between C and B pillars?

Due to some exotic tax limitations the vehicle doesnt have anything except front seats, the rest is a cargo area. The cabin is divided at B-pillar by a steel "grid-wall" (does not have any Impact on Sound) which cannot be removed without paying an arm and a kidneys worth of tax. Therefore a true B-pillar wall is sadly not an Option.

[Polar-bass]

Let me show you a couple of pictures of the current setup to illustrate what the possibilities and limitations are.

[Polar-bass]

Hi again. Not too much response here unfortunately. I have finally decided to run 6 15s, a semi-clam, horisontally divided with port top. This gives me enough baffle area for all woofers. Additionally I'll be able to modify the port easier, and hopefully make a changable port solution. It will be ran on just three amps initially, and if it sounds nice, but underpowered I'll double up on power in future. After studying tons of builds here, I do start to realize that power isn't everything. If the build is very good, it should do better numbers than my last, even with a little less power. Even if I don't manage to get close to a 155, I think the top port and cone area should provide some nasty demo abilities ...

And there will be a build log in a few weeks.

[goldeneye4564]

what are you tuning the box to

[Polar-bass]

what are you tuning the box to

Haven't gotten that far but right now the plan is a port for 30-32 daily music, which worked very well on the last build (I am guessing the vehicle also peaks somewhere around low 30s). Then I want to be able to change to a port with a tuning around 45. Only did one competition ever, it was ESPL. The shit we had to play had bass around high 40s, so if I ever want to do it again i'll need to play in that range too. I was actually beaten by a bunch of kids with Alpine type R's using less than 2K of power - slightly embarrasing, but my system would rape theirs and eat them for breakfast playing decaf.

Edit: it should be added that I don't dare to do a true clam with port middle right now. I just don't know how to calculate the port when it is placed in between two "declining" surfaces. I assume it will have an impact on port length one way or another. Any thoughts on this?

[hispls]

Just moving the wall up closer in itself will gain, removing volume of air you're trying to pressurize will gain. In theory if you could just pick your wall up and move it up behind the back seats (sealed off of course), you'd gain 4-5dB ish.

With 6 subs (12 coils) you have the option of running 1, 2, 3, 4, or even 6 or 12 amps.... assuming they'll drive whatever you can get those coils into. Don't be ashamed to run one amp to 3 coils if they're all closely gain matched.

Keep in mind, most b-pillar walls don't do much actual box behind that anyway.... that area is generally all amp rack and batteries, so just working between B and C pillar with the box should be fine IMO. I think the 15's are a good move. The big woofers can sound great if you have a big enough box, but thermal limitations are hard. Think of a 12" woofer on 1000W and a 21" woofer on 1000W. Which one is pumping more air through the coil for cooling? The 12 by a long shot. I've noticed significant difference in thermal handling between even 15 and 18" woofers with the same motor and coil on the same amp both in adequate sized boxes!

Lastly, If you break a 21" woofer what's a recone going to cost you? I'm betting you can recone the AB clones you have for under 100$ a pop if you break one.

[Polar-bass]

Yeah, about that wiring! I realize I made a stupid mistake.

The 4 Subs I have are D2. Which means if I run 3 amps I end up with a 0.5, 2 or 4ohm load on each amp, can't do that. Exactly how do I wire 3 voicecoils to ONE amp? I assume each amp will end up seeing .7ohms right? Sounds like I'd be better off with two more amps, or rethinking the whole rebuild. Shit.

Anyway thanks for bringing this to my Attention though.