Sealed Slot-Loaded Subwoofer enclosures?

[chuyler1]

Some JL's newer stealth boxes use a sealed slot-loaded design. I'm curious as to how this would work with a single sub in the corner of my P5 hatch.

Does anyone know how to go about designing one? I'd like to try one with a 8" W7. Since the sub is about as deep as it is wide, I was thinking facing it downward would be the best way to conserve space. However, I can't find any info on this type of box design.

 

[got wake?]

sealed slot loaded? do you mean ported/vented slot loaded? the port/vent rather than being round, is usually rectangular in shape, hence the slot name. this is typically don't to allow for easier building of longer ports, to keep the SQ high, and port noise low i use winISD pro for my box designs:
www.linearteam.org

 

[chuyler1]

nope, i mean sealed-slotted. but the slot, i'm asuming works just like a vented slotted enclosure.

I know there is a sealed-slot-loaded design using two woofers firing toward each other that adds 3-4db. w/o increasing xmax because the woofers become front-loaded by firing toward each other.

 

[got wake?]

it seems as though the slot works like a downfiring sealed enclosure, except it helps to direct the sound waves, so you don't have 4 different sound waves reflecting in your car. 1st mp3 would probably know more about these boxes i found these:
http://www.jlaudio.com/stealthbox/maxima.html#
http://www.jlaudio.com/stealthbox/accord.html#
http://www.jlaudio.com/stealthbox/blazer.html#

 

[chuyler1]

Yeah, those are them...I want to make my own for the P5. But I don't know what kind of calculations are involved (eg. area of the slot opening).

It is a popular design with home speakers and subwoofers as well.

 

[got wake?]

i'd just make sure the volume of the slot is at least the volume of the displacement of the sub maybe 1.5 times as much. the figure for ports to the back of the box is 1.5 times, so the slot would probably be similar in figuring air movement.

 

[chuyler1]

yeah, if I don't get any more info I'm going to try for an 8" woofer:
8"/2 = 4 = r
pi*r^2 = 50 (cu inches)

so an opening of 5x10", or 4x12" should do the trick. However that seems a little big compared to the stealth boxes and other slot-loaded enclosures I have seen.

 

[got wake?]

yeah, if I don't get any more info I'm going to try for an 8" woofer:
8"/2 = 4 = r
pi*r^2 = 50 (cu inches)

so an opening of 5x10", or 4x12" should do the trick. However that seems a little big compared to the stealth boxes and other slot-loaded enclosures I have seen.

ya know, there's got to be a formula for figuring it. you just calculated the surface area, and bring up a good point about the area and length of the slot. it's a specific for ported boxes for tuning, so i'd imagine it'd be pretty specific for a slotted sealed box, too. if i find anything, i'll post it

 

[chuyler1]

thanks. i did several google searches on it but I didn't come up with much. I know there is a speaker enclosure forum out there somewhere...i just can't seem to find it.

 

[1sty]

Last I heard the stealth boxes that are slot loaded have a redicoulus level of math behind them. I never got the equation or anything though.
I will look into it.

 

[chuyler1]

Thanks. Just post here if you find anything out.

 

[DrummingFrenzy]

Hey guys, I'm new to the scene here. Hey chuyler1 are you going for SPL or SQ? If you're looking to really save space you could always go an isobaric enclosure. They're complicated to build due to the difficulty of getting the woofers exactly in phase with each other, but they save a lot of space.

 

[DrummingFrenzy]

well I had a picture of one, but it didn't show. Let's try this again.

 

[1sty]

Isobaric is by far the least effecient box design and given sub depth usualy consumes more space then a sealed boxs airspace.

 

[chuyler1]

I'm going for "space saving convenience".

In other words, I bought my P5 with the intent to use the rear hatch. However, I also want some bass back there. I have build several boxes before and worked with fiberglass and I'm looking for solution that will give me the most bass out of the least space. (hey that rhymed)

Anyway, a slot-loaded design is still a sealed enclosure and it increases the efficency of the woofer by "loading" both the front and rear of the woofer similar to a 4th order bandpass enclosure. The result is that the woofer can play louder w/o increasing excursion. I'm not an acoustical engineer but that is what I have compiled online.

I'd be perfectly happy with a plain run-of-the mill sealed enclosure but that means the woofer will be exposed to the items in my rear hatch. I can make a grill and stuff, but to do it right, it will take up more valuable space. Having the woofer fire downward gives me the opportunity to take advantage of vertical space.

I noticed Q-Form is now selling a down-firing prefab box that has a spot for a small amp. There must be some rule of thumb about how to design one of these boxes.

 

[chuyler1]

Hey guys, I'm new to the scene here. Hey chuyler1 are you going for SPL or SQ? If you're looking to really save space you could always go an isobaric enclosure. They're complicated to build due to the difficulty of getting the woofers exactly in phase with each other, but they save a lot of space.

Some more comments...

As 1st stated, Isobarik doesn't really save space. Second, If I'm happy with one sub, why would I want two, for the price of two that put out the SPL of a little more than 1.

Do you see SPL monsters using isobarik designs? I don't. Do you see SQ professionals using isobarik designs? Again, I don't.

This design is a relic of times when subwoofer motor structures could not handle high pressure and high power. Two motors pushing the same air was necessary to obtain high SPL. That is no longer the case with todays 2000 watt subwoofers that have 3" excursions.

 

[DrummingFrenzy]

Thanks for the input 1st MP3. I'm still learning about the design of enclosures and I've heard that isobaric enclosures take less space. Glad to know I've heard wrong. I'm looking to do the exact same thing you are chuyler1. As in I still want to preserve my space in the back. I'm going more for SQ though. When you say downward firing do you mean mounted on the ceiling? I think that I'm going to pull out my spare and mount my amps and everything down there. That way I don't take up room in my hatch.

 

[1sty]

Hold on a link is on the way

 

[1sty]

Here ya go:
http://www.jlaudio.com/tutorials/isobarik/index.html

JL sums it up pretty good.
Clikcing the box type at the bottom will link to that types page.

 

[chuyler1]

Downfiring as in the woofer faces the floor and the box is raised 2-3" off the floor, closed off on 3 sides creating a "slot" in the front from which the sound comes. Check out some of JL's prefab boxes and you'll see what I mean. Its common in suv and truck enclosures that fit under the rear seat.