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Discussion Starter · #1 · (Edited)
I've just completed day 1 in my first subwoofer build. It was a lot of research to get me to this point, so hopefully it comes out well. Enough babbling, let's get to the important part - the specs!

Driver: Tempest x2

Box design: Forward firing woofer, side firing slot port. It's designed to fit behind my to-be-constructed screen wall, so a flat box was critical (I only have about 13.5 inches of space behind the 2x4's that are to frame up the wall - to keep my screenwall to 18" from the existing walls. I'm trying to minimize the reduction in distance from my first row of seating. Use: 90% HT, 10% music.

Box size: 48" wide, 24" high, 13" deep (exterior). Surface mounted woofer (it's behind an AT wall - doesn't matter what it looks like). Net volume is approx. 5.85 cuft after bracing, port, and woofer.

Port size: 11.5" x 2.75" x 32 3/4" - tunes to 20-21hz depending on the end coefficient used for the port ("two free ends" in WinISD vs. ~2.2 from an article I read about square/slot ports - I'll try to find the link for the retentive folks). Anyhow, close enough.

Amp: Dayton 500w with 18hz 3rd order highpass.

Pictures: Where the *$#(!!! are the pictures you say? This thread is worthless without pictures you say??? :foottap: Alright, hold your horses, they're coming - but you'll have to wait until tonight. :bigsmile: Things to look forward to - almost everything - I mean it's nearly done. Nothing like attacking a project with "gazelle intensity"!

I don't plan on any fancy finishes - probably just wrapping it in some sort of cloth or car carpet or something - just so it's dark and nonreflective. - it's going behind the screenwall. And the amp is going in the equipment rack in the screen wall, so I don't even have to mount the amp in the box. Hey this is getting easier all the time.

I'm already chomping at the bit to get this thing fired up! I'm coming from a "massive" energy exl-s8 - so this should be a modest improvement. :yikes: My wife has seen the box, but not the woofer yet. Heh heh...

More to come!!!!

Best,
C.
 

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Pictures: Where the *$#(!!! are the pictures you say? This thread is worthless without pictures you say??? :foottap: Alright, hold your horses, they're coming - but you'll have to wait until tonight. :bigsmile: Things to look forward to - almost everything - I mean it's nearly done. Nothing like attacking a project with "gazelle intensity"!


More to come!!!!

Best,
C.
:foottap::flex::foottap:
 

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You will be able to post pictures now Christopher, You just did not have enough posts to do so yet but now you have over 5.
 

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Discussion Starter · #6 ·
It will by lying horizontally below the AT screen, pointed towards the seating. Approximately 2-3 inches in front of the woofer will be a black fabric covered (AT) panel that goes the length of the screen underneath, the same above the screen, and to the left and right of the screen. Behind the screen itself will be the center channel - I have enough width in the room to have the left and right mains outside of the screen, but behind fabric panels as well, to create one sleek look.

I'm going to start posting my theater room build thread over at AVSforum soon. I'll attach a link (if not prohibited?) when I get it started, so you can see the sub where it will be, as well as how it integrates into the whole picture.

It's location on the screenwall is below the screen, and to the right of center, but closer to the middle than the right main tower speaker. This seemed to be the optimum location for imaging and frequency linearity when I was testing with my current (and very different) subwoofer - by ear and REW.

Best,
C.
 

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Discussion Starter · #7 · (Edited)
PICTURES!

Here's the progress from day 1:

Here's the 2d plan from sketchup, with lots of on-the-fly calculations to clutter the margins.



And the resulting nice pile of parts, all cut up...


I built the box from the bottom up (or back forward as the case may be). You can see the slot port, and lots of bracing. It's not hard to see where the woofer is going to go. Oh, try ignore the mess in my shop.



Here's a better shot of the box as it stands, showing a little different view of the bracing and slot port.



Most of the bracing was cutout on the workmate with a sabre saw. When it came time to cut out the woofer hole, and considering I've never used my circle jig before, this seemed like the perfect opportunity to try it out! Holy cow, who'd have thought there were so many parts to it??? By the time I got it set up (it even had a dust port!), this is the contraption I ended up with!


It cut a nice clean hole, with hardly any dust - color me impressed! That being said, it would have been a lot faster just to use the sabre saw and a little sanding. But sometimes it's all about the journey. :bigsmile:

That's it for the first day of construction... MORE TO COME!

Oh, question: A small amount of polyfill (20%), bare wood, or glue some foam onto the internal walls -- why or why not? Thanks for your input and following of my build.

Best,
C.
 

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Looking good.....:T
 

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Discussion Starter · #11 · (Edited)
Thank you for the kind words about the build (and my garage/shop).

Regarding internal wall treatment -yea or nea? :dontknow:

I want to get the top on, but can't add foam to the walls afterward. From talking with Kevin, if the port reinforcement is too much, I can dampen that down with polyfill later by removing the woofer, but getting to the walls is not possible with such a flat box.

Best,
C.
 

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Discussion Starter · #12 ·
Oh, and for those that were wondering, here's a sneak peek at my plans for the theater room, compliments of my blossoming Sketchup work. You have no idea how many hours I've spent to get the drawing to this point - I nearly could have been done with the construction by now... Well, maybe not..



Here you can see the false wall - I made it somewhat translucent so you can see the speakers and woofer cabinet behind it. The center brown area is where the screen goes (I took it out so you could see the center channel behind). The size there is a 120" diag 16:9 screen - I may go 130" scope though, which would mask down to 105" 16:9 - movies are the primary use of this space. The brown walls on either side of the black fabric panels around the screen are going to be fabric panels, in the same fabric as the acoustic panels on the wall. The will give open access to a simple component rack on the right, and a very similar bookshelf type unit on the left for media storage (there are no doors, just an framed opening in the panel to freestanding shelves behind. Above the cabinets in the corners, I will likely do superchunk bass traps extending up to the ceiling (all hidden behind the false wall).

Back on topic with woofer cabinet construction, I will likely add dense foam (like that on the Aurelux subdude) to the bottom of the cabinet, to attempt to isolate the vibration from the floor, as this is on the second story... :gulp:

Best,
C.
 

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Thank you for the kind words about the build (and my garage/shop).

Regarding internal wall treatment -yea or nea? :dontknow:

I want to get the top on, but can't add foam to the walls afterward. From talking with Kevin, if the port reinforcement is too much, I can dampen that down with polyfill later by removing the woofer, but getting to the walls is not possible with such a flat box.

Best,
C.

I asked this same question in three different threads and got zero answers.

From researching, the general consensus is "try it and see what works for you".
 

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One observation If I may. Since you dont need the horizontal orientation of a normal center, it would be wise to orient it vertically for better off axis response.

The room looks good and the box is shaping up nicely. Sorry Im not of much help with your fill question.
 

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I asked this same question in three different threads and got zero answers.

From researching, the general consensus is "try it and see what works for you".
The general consensus on internal treatments is a little more complicated, but for a sub, you've got your answer.

Internal acoustic treatments are either surface absorber or volume dampers. Surface treatments absorb reflections, with even thick layers (2") having little effect below 250Hz. Therefore, subwoofer internal coatings tend to be structural - damping box resonances - rather than acoustic.

However, sub performance can be greatly affected by the amount of fill in the volume of the box. If present, you can't block the port, obviously, but you can modify how the box as a hole resonates. That's a personal choice, thus the advice...

Have fun,
Frank
 

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Awesome explination, Frank! That's about what I summed up myself after staring at my overlarge box for a while. I know bass traps need to be a certain distance from the wall to work on the 1/4 wave, and I can't imagine how a little egg crate glued to the walls does anything. Egg crate foam also doesn't have the mass to damp (not dampen, I don't want a wet speaker! LOL) the panel resonations. So I just went with some polyfill pillows and 3" thickness of acoustic rockwool about 2' off the "back" panel of my box...I figured that was the best I could do considering.
 

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Discussion Starter · #17 ·
Thank you for the input and explanation!

I'll be just using polyfill for now, and will be able to adjust the volume of that later depending on the response and any tweaking that I need to do after testing.

Regarding the center, I'm going to try it both ways - horizontal and vertical. I know that the off axis response should be better vertically, but for some reason during some VERY brief listening, it sounded better horizontally. I'll give more feedback on that when I get to that stage.

Not too much progress - it's been caulked, the top is on/glued up. I'm getting ready to wire, attach the woofer, and get it covered. That's all that's left on the sub. :sn:

I had serious thoughts on scrapping the screenwall and going with a regular ol' corner placed sub - requiring scrapping this project and starting over on the box. I thought that might be the overall easier, faster, yet still asthetically acceptable approach. Ha. My moment of lucidity came when my wife started talking about me doing an equipment rack built into the wall (the other side of which is the attic). The thoughts of tearing out wall, studs, crippling, forming a fully insulated, accessible rack closet with rerouted power and ventilation.... :rolleyesno: well, that was enough to snap me back to reality and strengthen my resolve to press on with my current direction. I'll take the fabric covered frames, thank you very much. :T

Best,
C.
 

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Discussion Starter · #18 · (Edited)
Re: Simple Screenwall Slot-port Tempest build - finished!

The sub is finished! Sorry I've been remiss on my duties to report my progress. Port is painted, it's carpeted, and the driver is installed.

I drank the koolaid and used t-nuts and hex socket head screws for the driver. I originally bought regular 10-24 screws and some wood screws and the heads were too big to get through the plastic flange around the driver. The socket heads were a snug fit down, but cleared much more easily than the other screws. I went one step further and added a touch of epoxy around the base of the t-nuts when I installed them, and used an f-clamp to squish them into place. Worked great.

Per discussions with Kevin, I used about 20% polyfill, and lugged the cabinet upstairs to the media room, huffing and puffing as I went. I left the driver out for the move, so I could reach into the cabinet with both arms to help carry it. :R

Got the driver installed in the media room, wired it up, and ran Audessey to calibrate the whole system. Set the amp to about "3", and it was perfect.

Fired up the system with music and it sounded really nice - perhaps a bit heavy on bass, but not bad. I think that has more to do with the recordings themselves than anything else - classical (even high output Telarc digital stuff) sounded pretty balanced.

The great part? HT. Wow. Let me say that again, WOW !!! :hsd: Really - the sub is amazing. Rich deep bass, effortless. I started listening to a bunch of different movies, and the smile kept getting wider on my face. It not only added to the high LFE portions of the movies, but everything sounded richer and fuller. Very very nice, and very smoth (definately not 1 noteish).

I ran REW just to see what was going on, and except for my room modes, it's got a nice curve. Audessey boosted the 10-25 hz region even more, creating a substantial house curve. I'll try to post those graphs here, along with the finished pictures. I'm a little concerned that the Audessey curve will stress the amp and make it clip, but so far there's no sign of that.

Next stop is finishing off the room. I just got the linacoustic yesterday, and that will be going up soon, so I can get the screen wall together.

Thanks again for everyone's help, especially Kevin. It's been fun and informative looking at all the builds here and at AVS -- this is such an amazing resource.
 

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Re: Simple Screenwall Slot-port Tempest build - finished!

I like your box design. Deep, narrow with plenty of port area. Nice job....

Kevin Haskins
Exodus Audio
 
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