4th order wall alignment

[adulbrich 5,000+ posts]

Subs are getting shipped this week, and I need to decide on an enclosure for sure. I have 50 more yards of fiberglass coming. I currently have 5 gallons of resin, 25 feet of fiberglass cloth, a sheet of 4'x8' birch plywood, a few 2x4's, screws, and threaded 1" metal pipe. Going to buy 1 or two more sheets of birch and 50 2x4's soon.

I was really stuck on the design of the sealed chamber on the bottom with the ported chamber on top and a top port. Subs would be facing down with the motors up. Would look something like these pictures:

I'm also considering doing 4 of the subs on each side and putting the port in the middle like these pictures:

I know with a shared airspace, subs need less enclosure volume. Would separating them into two sealed chambers instead of one sealed chamber really make a difference on how much sealed volume they would need?

Would either design yield more/less cancellation?

Which would you guys choose and why?

Thanks!

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[dbjunior 10+ year member]

I like the second design. It would make working on and checking things much easier than trying to climb in a top port. I think it would be stronger of the port was also used for bracing.

 

[Papermaker85 5,000+ posts]

Subs are getting shipped this week, and I need to decide on an enclosure for sure. I have 50 more yards of fiberglass coming. I currently have 5 gallons of resin, 25 feet of fiberglass cloth, a sheet of 4'x8' birch plywood, a few 2x4's, screws, and threaded 1" metal pipe. Going to buy 1 or two more sheets of birch and 50 2x4's soon.
I was really stuck on the design of the sealed chamber on the bottom with the ported chamber on top and a top port. Subs would be facing down with the motors up. Would look something like these pictures:

I'm also considering doing 4 of the subs on each side and putting the port in the middle like these pictures:

I know with a shared airspace, subs need less enclosure volume. Would separating them into two sealed chambers instead of one sealed chamber really make a difference on how much sealed volume they would need?

Would either design yield more/less cancellation?

Which would you guys choose and why?

Thanks!

who told you share airspace needs to be less? that's strightup ********..cancellation in 4th is pretty uncommon. use as much port area as you can with creating any loading on the cones and you will be fine.. what i mean is the woofers should have at-least 2x there potential displacment between the cone and any other surface.

 

[Buck 5,000+ posts]

I don't think it matters a whole lot, as long as all the numbers are correct.

 

[adulbrich 5,000+ posts]

I like the second design. It would make working on and checking things much easier than trying to climb in a top port. I think it would be stronger of the port was also used for bracing.

I was going to put the front wall on last, after installing the subs, so it would be easy do do everything

who told you share airspace needs to be less? that's strightup ********..cancellation in 4th is pretty uncommon. use as much port area as you can with creating any loading on the cones and you will be fine.. what i mean is the woofers should have at-least 2x there potential displacment between the cone and any other surface.

Ok

I don't think it matters a whole lot, as long as all the numbers are correct.

Alright, thanks. That's what IAMSONIC said

 

[mlstrass 5,000+ posts]

You can build a little on the small side for sealed section and use polyfil if space is an issue. I prefer 2nd design or all subs on pass side of enclosure if you have room.

Plan on using a TL to dial in port opening as NO design software is ever close. Cancellation can be an issue with long/deep baffles but playing with phase can fix that and gain on the meter.

 

[adulbrich 5,000+ posts]

You can build a little on the small side for sealed section and use polyfil if space is an issue. I prefer 2nd design or all subs on pass side of enclosure if you have room.
Plan on using a TL to dial in port opening as NO design software is ever close. Cancellation can be an issue with long/deep baffles but playing with phase can fix that and gain on the meter.

Only thing is, I don't want to have the port behind the driver's seat because it would be obstructing the port

 

[Buck 5,000+ posts]

Only thing is, I don't want to have the port behind the driver's seat because it would be obstructing the port

I don't think it will matter much here, many people do it. Meter wise it should be louder, on one side at least.

 

[adulbrich 5,000+ posts]

I don't think it will matter much here, many people do it. Meter wise it should be louder, on one side at least.

I put the port behind the driver's seat with my DD 9918 Z's with the hope that it would be loudest on the passenger side.

No matter what I do, I can't make it loudest on the passenger side. Always loudest in the driver's seat. It's frustrating to say the least.

Any tips to make it loudest on the passenger side?

 

[Buck 5,000+ posts]

I put the port behind the driver's seat with my DD 9918 Z's with the hope that it would be loudest on the passenger side.
No matter what I do, I can't make it loudest on the passenger side. Always loudest in the driver's seat. It's frustrating to say the least.

Any tips to make it loudest on the passenger side?

Test it. I really don't know

 

[adulbrich 5,000+ posts]

Test it. I really don't know

I really don't want to re-build this a bunch of times to get it right. I was hoping somebody else could chime in with what worked for them.

With the Warden's, I tried a passenger side port. Still louder in the driver's seat //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[Papermaker85 5,000+ posts]

my advice. build a box for ONE.tweak it to find out the exact response you want. once you have the alignment and configuration you like and that does best in your cab then build the enclosure for them..

 

[adulbrich 5,000+ posts]

my advice. build a box for ONE.tweak it to find out the exact response you want. once you have the alignment and configuration you like and that does best in your cab then build the enclosure for them..

Basically one small 4th order for one sub and see what works best? I've heard that before, but the cabin airspace in my truck will be 50% smaller when I put the full-size 4th in and the resonant frequency would be drastically changed.

 

[Papermaker85 5,000+ posts]

Basically one small 4th order for one sub and see what works best? I've heard that before, but the cabin airspace in my truck will be 50% smaller when I put the full-size 4th in and the resonant frequency would be drastically changed.

Yes but your concern is how the driver responds to the box and cabin. The goal is to get the single driver to have the desired response and passband . Once you find the proper airspace tuning and fr it's going to be a matter of a couple hertz to correct the smaller cabin airspace. The shift in rolloff will be slightly sharper and resonance will be slightly higher. At that point you will only be adjust the port(tuning) instead of adjust everything and guessing.

 

[adulbrich 5,000+ posts]

You build the shell of the 4th... Then build the sealed side. Make it alittle bigger. Run a sweap and see where it peaks, Then u can shrink it and find the res freq u want. Then build loading wall and tune to res freq.

Yes but your concern is how the driver responds to the box and cabin. The goal is to get the single driver to have the desired response and passband . Once you find the proper airspace tuning and fr it's going to be a matter of a couple hertz to correct the smaller cabin airspace. The shift in rolloff will be slightly sharper and resonance will be slightly higher. At that point you will only be adjust the port(tuning) instead of adjust everything and guessing.

I'm making the sealed section 10-12 cubes and stuffing with polyfill. Can remove polyfill to effectively shrink the sealed side if need be.

Port will be adjustable/removable so it can be easily tweaked