ibf150

I was supposed to finish my cardboard templates today and start cutting wood BUT I went to the New Orleans Red Dress Run and you know when you pay $70 wear a dress roam the streets and can drink all the beer in the world for free awesome doesn't have a killswitch. Tomorrow is the day though that I will work on it for sure.

officermartinez

Free beer.. 'nuff said! ..lol. Well, my parts should arrive in the next few days. I am going to sell my polk audio db 571 speakers and my rear seat f 150 subwoofer box. That box was made by a company called subthump. Looks like I won't need it anymore now that I've got six 15's replacing it.. hehe. If you're interested in it, holler at me.

Guinness68

So... This is very naive perhaps, but this is what i was thinking with the dimensions provided. Make 6 enclosures. bottom row (3) would be cubes. Top row would be a wedge of some sort.

At first I was thinking I'd go 20" deep, but when I calculated Vb for the cube, I couldn't go 20". 15" woofer is someone limiting. So, I found that 14.1" is the depth that works. I'm not accounting for the driver displacement, but it could be considered part of the .03 cuft.

My two cents... keep the change

officermartinez

OK! First off, I want to thank you Guinness68 for taking some time out of your day to work on this.. I just got off the phone with Polk Audio (spoke to Matt). We discussed your box design and he liked it but he cautioned a little about not keeping every chamber uniformed. Your design definitely works but as one of their master installers, he said he would just fire ALL (6) subs forward. I asked about down firing (3) of the 15's and forward firing the other (3) 15's. Even though all (6) chambers would be equal and uniformed, firing them in opposite directions @ 90 degrees may cause unwanted cancellation inside the cab. If I am going to down fire (3), I should down fire all (6). Just food for thought. I know I am clumsy and I can totally see me jacking up a forward facing sub.. haha!

So, I guess (3) 15's on top, (3) 15's on bottom. Still undecided about the direction that would best suit me: Forward firing or down firing. I do know that each chamber will be:



It was explained to me that Polk engineers / developers took the speaker driver displacement into consideration when making their airspace recommendations (one less thing to worry about). He did say that 1.5 cu ft is the perfect size box but mentioned that I might want to add exactly 1 lb of polyfill per sub.

Guinness68

I agree. I wouldn't put them out of phase like that... down and then forward. My design was forward on the bottom and angled (forward) up top.

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The Vb of each box was the same, but the master installer didn't like that the boxes weren't the exact same dimensions? Interesting.

If that's the case, then your cube or mine, and six of them. All facing forward. Put a grill on the fronts so you don't accidentally jam your elbow into one of the subs (10" away from the front seat, by the way)

One reason for Polyfill is to trick the sub into thinking it's in a bigger box than it actually is. I'd ask, if there's no physical constrictions on Vb, how big should you go?

Have you played with box size in WinISD?

officermartinez

Been goofing around and have a "design" in mind. This type of design eliminates the risk of me directly hitting any of the (6) forward firing subs. The dimensions can still be "tweaked" a bit but they are more or less within spec (that's called a disclaimer in case I am WAY off on my measurements.. haha)! Since I have had extremely good results running my (4) 10's in a down fire position, it sort of solves the two birds with one stone. I do understand that the floor of a vehicle is generally more enforced than any other side of a vehicle. This should help in the deflection of sound waves instead of energy loss into a non reinforced / dampened side panel. It's not much of an issue with a pair of 8's or 10's but multiple 15's, it's a big factor to consider.

The particular Polk Audio 15's that I will be using, the MM1540, has a mounting depth of only 4 5/8". That's small compared to many of the 15's offered on the market today. Planning for a blown sub, all I need to have is about 5 - 6 inches between the floor of the truck. The 7" chamber on the diagram should also be plenty of room to swap out a blown subwoofer (if that should occur).

officermartinez

I think the Polk installer was probably thinking more in the terms of ease of the build. That's the tone that I gathered. He didn't hate or disagree with the overall design. I think he was just trying to simplify it.

As for the polyfill, this is what I was told. This 15" sub uses the same basket structure and magnet as their 10" sub. Its' personality is more like a 10" sub vs a traditional 15" sub. The polyfill I am told, will slow it down 'ever-so-slightly' and fine tune it to go a tiny bit deeper. He said it's not necessary but I would probably prefer to have it in there. He was very specific about 1 lb only.. no more no less.

Guinness68

Firing it down.. you won't be able to see it. I would want to see those drivers jump.

Also... in your scratch design, you're missing inches off the floor. if you went 7", like on row2, you'd be about 40" high. Too high?

Interesting comments about the 15" behaving like a 10". I would infer that means it is crisp, tight, responsive.

officermartinez

Well that's true. I just pulled 7 inches out of the air. Figured it would give me TONS of room to work with. The enclosures can be tweaked still. I have up to 20 inches to work with front the rear of my seats towards the rear window / bulkhead.

Crisp, tight and responsive is good.

officermartinez

OK.. Plugging in the numbers, if I used 20", from the back of my front seats towards the back window and the numbers that I have in my diagrams, I come up with your original # of 1.53 cu ft