4 cubic feet, tuned to 22 Hz, port area >= 64in^2

[emilimo701 10+ year member]

The problem is that this calls for a really long port. I'm talking 80+ inches.

I have a Legacy wagon, so I have a decent amount of space to work with, but I'd like to keep the box height low enough so that I can still use the retractable cargo cover for the purpose of preventing theft.

The 15" Axis has an xmax of 30mm which calls for sufficient port area, which further increases the length of the port.

My original design had one slotted vent (16" x 4") wrapping around 3 sides plus a quarter of the front side, inside the box, which the subwoofer and port both front facing. I can post a drawing, or a picture of the box set up ready to be glued and screwed.

I think I got some of the measurements wrong so might have to scrap it.

I was thinking of designing a new one, with dual slotted ports (one of each side), and making things simpler with no 45 degree angles in the port (just 90/180 corners).

My question to the experiences box designers would be, how would you go about this is a client wanted a really low tuning frequency, where your options for space are kind of limited?

Maybe I will have to choice but to make the box height higher, and make the sub side-facing? I'd like easy and logical access to the wiring terminals.

Click to read more...

 

[RangerDangerV2 5,000+ posts]

first off why would you tune that low?? if you want to play low build a fourth order or a t line. also why would you do dual ports? just do one, more efficiency and a lot easier.

 

[RangerDangerV2 5,000+ posts]

and if you are low on space you need to do a smaller port, but for really low extension go with a t line or and 8th order.

 

[Kangaroux 5,000+ posts]

That low of a tuning for a ported box is a waste of time. Do a 4th order bandpass tuned to ~35hz if you want that kind of low end. My box is tuned to 40hz (it's a 4th order) and I can play down to 18hz and still have some authority, and I can play up to 55-60hz before it starts to roll off too much.

 

[RangerDangerV2 5,000+ posts]

That low of a tuning for a ported box is a waste of time. Do a 4th order bandpass tuned to ~35hz if you want that kind of low end. My box is tuned to 40hz (it's a 4th order) and I can play down to 18hz and still have some authority, and I can play up to 55-60hz before it starts to roll off too much.

same for me... only I have a simple ported box... I can play from 18-50 with authority but any lower or higher and it is meh.... 27hz seems to be the peak because it absolutely murders your hold that though remix... and your never enough chopped and screwed version...

 

[Falcons 5,000+ posts]

what about i cook by oj da juiceman??

 

[RangerDangerV2 5,000+ posts]

what about i cook by oj da juiceman??

dont have that but I can absolutely murder midget slowed...

 

[hispls 5,000+ posts]

This is why TC sounds pushed the passive radiators.

I would agree that tuning that low is pointless unless you're trying to **** off whales. I ran 15" TC-2000's tuned at 28hz and they played plenty well down to 20. This was when I was running 5.1 surround and watched a lot more movies and I never ran out of bottom end for sound effects.

I strongly suspect if these subs performed well in bandpass alignments it would have been mentioned on the old TC forums (which I can't for the life of me recall anyone ever saying was a great idea). Really you'll probably find more people who know what they're talking about with that sub on HT forums.

Any way you work it your port is going to be very long. Don't even think of doing 2 ports since they would be impractically narrow. Any way you can fold it would be about as good as the next I think, though the least number of turns/angles in it the better.

 

[emilimo701 10+ year member]

I'm tuning at 22 Hz based on the specs of the sub, and what I want to get out of the system. I can hear the 20 Hz tone in "Put On" by young jeezy and kanye, so i'm kind of using that as my reference. Right now with the Axis in a sealed box, i'm not getting the output I want. It's about 16db down at 20Hz, and that simply is not cutting it. I want that 20Hz tone to slam with the same authority as the others. If I find out that such a lot tuning isn't necessary, I'll rebuild a new box tuned higher. But right now my goal for the enclosure is firm: 4-4.2 cubic feet tuned to 22Hz. I don't so much want high SPL in the 40-50 Hz range; rather, a flat response with a graceful rolloff. Maybe I won't end up liking it, but I want to at least give it a try, for curiosity's sake if not anything else.

I've done the simulations in WinISD, and have used another online resource that has corroborated the measurements of WinISD.

Any way you work it your port is going to be very long. Don't even think of doing 2 ports since they would be impractically narrow. Any way you can fold it would be about as good as the next I think, though the least number of turns/angles in it the better.

Right, I have seen recommendations that a rectangular port should not have a ratio higher than 1:8 and have even seen 1:5 as the max. The design I have right now is one rectangular port: 16" x 4". The annoying thing is that it wraps almost all the way around the box, unless I want to incorporate 180 degree turns into the port design.

The benefit to using dual slotted ports (besides the aesthetics) would be that I would be able to locate the wire terminals conveniently in the back of the box without have to route them through the port space. Also, this would mean that the subwoofer would be able to be front-facing and centered.

I was thinking of decreasing the height of the box and going with a 15.5" x 2.25" port on each side. Eh?

 

[emilimo701 10+ year member]

This is more of an experiment and learning experience than a box I see myself using long term.

 

[RangerDangerV2 5,000+ posts]

you dont have to tune that low to play that low. Im tuned to about 37 and I can play down to 18 with authority.

 

---------- Post added at 02:55 PM ---------- Previous post was at 02:55 PM ----------

 

This is more of an experiment and learning experience than a box I see myself using long term.

if you are experimenting go with aeros or a removable port to get the desired response

 

[chillin 10+ year member]

Why dont you use an aero port or sono tube and use elbows inside the box or have some of it outside the box?

Edit: Ranger beat me

 

[emilimo701 10+ year member]

Why dont you use an aero port or sono tube and use elbows inside the box or have some of it outside the box?
Edit: Ranger beat me

I had considered that.

What is a good source of said sono tubes?

 

[Kangaroux 5,000+ posts]

I'm tuning at 22 Hz based on the specs of the sub, and what I want to get out of the system. I can hear the 20 Hz tone in "Put On" by young jeezy and kanye, so i'm kind of using that as my reference

Is that the slowed version or the original? The original is at 28hz. It's hard to actually hear 20hz clearly, it takes a lot of cone area to pick up a note that low.

 

[emilimo701 10+ year member]

Is that the slowed version or the original? The original is at 28hz. It's hard to actually hear 20hz clearly, it takes a lot of cone area to pick up a note that low.

Ah! You might be right actually. My bad. I'll have to go check again in audacity, I think it's listed on some website as well. But yeah 28 Hz sounds right...