Tempest Box Project Begins

[Chris Tsutsui]

I am about to purchase the materials necessary to start my Tempest project. It will be an Adire Alignment enclosure with a 15" tempest.
214L cabinet (37.5"H, 22"W, 22"D on 4" legs)
tuned to 15.4 hz
3" flared ports with 11" long center tube
Matches 2nd order roll-off with
Q = 0.577
Fc 20HZ within 0.5db down to 11hz
Group Delay near 17ms at 20hz
I am open for any suggestions that will save money and would like any thoughts/concerns.
Parts Express 250 Watt plate amp$135.90 + S&H
15" Tempest$150 shipped
PE round speaker terminal $4
17ft EFX-2 RCA interconnect FREE (old car audio IC, will use one side for sub's mono)
Dayton 12ft RCA IC $11.70 -- If the EFX cable sounds bad, I'll buy this. Hopefully the low quality EFX cable only distorts the highs and won't affect the lows.
PE 3" flared port tube kit I'll need 2 of these kits = $24.60 + S&H. Can I just get the flared ends somewhere?
12 gauge home depot speaker wire0.47 per ft, to connect driver to plate amp.
Question: Do I wire the amp parallel to the 2 terminals on the driver? Will this produce 4 ohms so my amp can output 250 watts instead of 150?
$312.45 total items + shipping
$80 = 2 x maple laminated 3/4" MDF sheets (4x8')
$7 for some Spray on over coat
Total costs: $400
The cost of nails/screws/glue/biscuits/solder/caulk is free. I will build it with my friend who is a professional contractor at his shop. He wanted to cut the edges of the maple laminate at 45 degrees and join the planes together using biscuits (wood oval discs that fit in slots) and glue. He said the outside will have no nails, but if I want, he can use countersunk screws and maple plugs to hide the screws.
We will turn out some sold maple legs on a lathe from some scrap wood and not use speaker spikes. I might add the spikes later if I'm not satisfied. The HT room is about 11' by 12' on the 2nd floor of my house so things are gonna shake anyways.
I was going to use 64oz of R-12 fiberglass insulation on the inside of the box but am afraid it will cause a health hazard due to the vents. I will probably NOT use any, and will add it later when I want to spend the $40 on 5lbs of acousta-stuf.
That about does it for the parts I'm ordering. I'll be able to take many pics and post results on my website once I get started. Thanks

 

[Kerry Hackney]

Do I wire the amp parallel to the 2 terminals on the driver? Will this produce 4 ohms so my amp can output 250 watts instead of 150?

Yes..
As for stuffing: I used a polyfill product from a local fabric store. IIRC it took 8 bags and costs about $3-4 per bag. No itch, and it works fine. Mountain Mist is one brand that is particularly fine/soft and seems to work well for me as a stuffing material. I don't remember ever seeing flared ends seperately. I used the ones from Madisound as well as the terminal cups. Not saying you should the PE ones will be fine.
As for the sub, you're gonna love it. Whoever or whatever is downstairs from your HT may not.. but you're gonna love it..

 

[Patrick Sun]

Why not use a single flared 4" port? (But you should really go larger (like 6" wide)).

 

[Jeffrey_S]

Chris,

Glad to see you've begun. I should have my Adire Alignment up and running this weekend. I can hardly wait.

I was wondering if you are mounting the plate amp into the cabinet? If you did you wouldn't need the terminal cup. I e-mailed Dan Wiggins about my concern that mounting the amp might affect the structural integrity of the cabinet. He assured me that it wouldn't so I cut a notch in the rear "brace A" and made a hole in the back panel of the sub. Of course, keeping the amp outside the sub has its advantages. It will make it easier to try other amps and to upgrade your amp in the future.

I look forward to seeing some pics as construction begins.

Jeff

 

[Chris Tsutsui]

I havn't seen a place that sells 6" flared ports. When I was playing with the Adire program it showed a big difference between flared and non flared. I have decided to go with the recommended dual 3" flared cause it had some good results.

Jeffrey, excellent point I have been building nothing but car audio boxes and forgot that the plate amp will mount on the box. Therefore no need for a speaker terminal.

However, I do like the idea of having the speaker terminal on the box so I can also use it in my SUV as a sub. The box will be lying on its side but I don't think it will harm the downfiring driver. It would be fun to cruise with the windows down having a tempest set off car alarms. Cons for the HT are the plate amp would be ugly on a shelf and the quality would be reduced due to the longer speaker wire and terminal.

Some fellow art students and I have come up with a few forms for the enclosure. I am always up for challenges and don't want a typical cube shape. My contractor buddy said they can steam to make bends in MDF. This opened up a new realm of possibilities for a unique design but I have been leaning towards a geometric form. I'll post some sketches on my site for input later tonight.

 

[Chris Tsutsui]

Designs Link
I took a digital pic of a small sheet of paper I drew sketches. The drawings are letter labeled for reference. Sorry if they are too small on your screen resolution, I didn't want to fetch the scanner and it would take too long to draw these on autocad or paint.
I would like to have the ports firing towards the front. If it doesn't affect the sound that much I would rather have the ports be visible from the front.
Any criticism on the current designs? Could you post what designs you like best? I'd like input before I say which one I like. Oh, and I ordered my Tempest from acoustic-visions for $150 shipped. I couldn't find it anywhere cheaper.
Edit: Does the tempest work perfectly front firing? I saw a few projects with front firing tempests. I was under the impression the tempest is a downfiring only sub. If the ports shoot towards the front it won't affect sound will it?

 

[Patrick Sun]

With a 6" wide port, you don't need the flaring as you would with 3" wide ports. But it's easy to roundover the port opening if you like the flared look.

Some drivers are not suitable for downfiring operation. All drivers are suitable for frontfiring operation.

I am just about done with sub enclosure type B (from the sketches), and I would not enjoy building the non-box enclosures because the internal bracing pieces would be a nightmare to create.

 

[Kyle Richardson]

I like designs O, F, G or J. Like Patrick says, the Tempest can be front or down firing. The ports can fire in any direction you choose as long as they have some room at both ends of the tubes for air flow.

 

[Jeffrey_S]

Chris,

I agree with Pat about the problems that could arise regarding bracing. You might consider building a traditional box and then adding on some decorative elements to give you a shape of your choosing to get around any potential bracing problems. Of course, this would give you an even bigger and heavier cabinet.

Jeff

 

[Dustin B]

But if you are or are getting the help of a Norm wanna be, go for which ever one you like best.

 

[Chris Tsutsui]

At my design class I didn't get many innovative suggestions so I'll probably go with something along the lines of "O" and "F". (the ones I liked)

It will certainly be a one of a kind... I'll make a paper maquette to see if it looks ok in 3D, then start the process of calculations and bracing. I'll post a pic of the paper model and create it on autocad if I have the time.

Heh, I didn't know you were the same Kyle I emailed at Acoustic Visions.

Edit: After bringing the design into real space, I decided to go with a design not on the sketch board. The base is a 22" by 22" square, the top base is a 13" by 13" square, and the height is 41.723". The volume is 214L or 13,059.25 inches cubed. The shape is a frustum pyramid (chopped off top square base pyramid).

Well it's time to crank out some more numbers and find what angles to cut each piece. I'll have the blue prints ready tomorrow.

 

[Kerry Hackney]

Chris,
Are you gonna share the details of that cabinet.... PaLLEEAASSSE!!!!

 

[Kyle Richardson]

Sounds like a nice idea and the bracing should be pretty easy too as long as you can calculate the angles to cut the sides. AutoCAD or something equivalent should make that quite easy for you.
Keep us updated.
PS. Yep, I'm the one and only for better or worse

 

[Chris Tsutsui]

I chose a design
It is similar to the sketch letter "I" except not as tall. The volume is 214L for an adire alignment type enclosure. The bracing will be done the same way as recommended. All 4 sides are angled towards the center. The form is a slim pyramid with the top chopped off. (Oops I gotta recalculate and subtract the total bracing volume) Anyways the measurements will still be close, I might make the base 23" and raise the height a little to meet 214L.
I'm still self-learning autocad2002. I can make boxes in 3D but not a shape like this.
I should get the parts soon, I'll order the 3/4" MDF laminate (maple). One side will be high grade maple, the other will be lowest grade. (My contractor friend told me not to have just one side laminated.)
This shape should actually prove to be effective with the tapering top. Hopefully we'll be able to pull this off, it ain't no ordinary box

I'll keep u posted

 

[Jeffrey_S]

Chris,

I like that design alot! Take my advise and work out the ditails in a cad program even if there is a learning curve. It's fun and it saves you in the long run. Keep us all posted.

Jeff

 

[Blake Middleton]

Chris, if you need some help with AutoCAD, let me know. That's all I do all day!

I would not try to draw it as a solid if you want to accurately measure angles and such. Just draw plan and section views so you can dimension and take accurate measurements. If you draw a solid, AutoCAD won't let you snap to any 3d points, just the insertion point i believe.

 

[Chris Tsutsui]

Updated with Cad picture and links
I've finished calculations, I included one pic of a cad drawing. It was very helpful for finding the measurement numbers and placing the circle cut-outs.
In the CAD drawing there is a rectangular cut out in the bracing for the driver... There was a small triangle in the bottom right corner that I'll leave out, this should make up for the extra displacement the ports and wire take up. (3-4 cubic inches)
Well next week I should have all the parts, and next Sunday my friend and I will start bringing this baby to life. I can still change my mind for what laminated MDF to use.. Mohogany, white oak, maple, ebony, cherry, beech, or walnut come to mind. I will most likely go with maple because of the grain and color of a quality sheet. My second choice would probably be mohogany, then oak. Ebony would be absolutly amazing but the cost gets high with exotic woods.
"Watching a piece of furniture take form is like watching a child grow"