JL 10W7 Sub Build... Please help a newbie with his first sub build!

[Audiophile1178]

I used to be really big into car audio and have a few 10" subs that aren't being used so I figured that I'd put them to use. I want to use two JL 10W7's for my home theater sub build. I know that 10" subs aren't the greatest for HT but I think they'll do fine if put into the proper box. Also, I live in a condo so if I go for crazy bass then I think my adjoining neighbors will kill me. Here's the rundown:

I'm basing this build off of this. Scroll down to the bottom on the second page.

Specifications:

Room: 12'(Deep) x 16'(Width) with 8' ceilings with wide opening to dining room which is next to it.

-I want to have one sub on each end of the room (16' Width part of room) standing next to my boston acoustics VR3 towers.
-I want sub box to be no higher than 40" (to match VR3's height) ~16" wide and ~22" deep (Can change the width and depth a little).
-Both subs will be powered by a Crown XLS 2500 Class D Pro Amp (775w x 2 @ 4 Ohms, 1200w x 2 @ 2 Ohms)
-I talked to Crown and they stated that the amp has a 24db per octave roll-off at 20Hz so I don't think that I'll need a subsonic filter to protect the sub from overexcursion.

Questions:

1. I modeled the 10W7 in WinISD and came up with 3.6^3 ft. box tuned to 21Hz with a 6" flared port measuring 43.5". I'm thinking the crown will put out ~900watts each @ 3 Ohms to each sub but did the model with 775watts rating. I did a 20Hz HPF filter and an 80Hz LPF filter. The 20Hz filter is the roll-off from the crown amp (from what they told me) and the 80Hz is from my processor. Can someone verify that I did this correctly. You can see the filter settings in the pictures.

2. Do I have to worry about over excursion with this sub?

3. Can I make the whole build out of 3/4 inch mdf and then put another layer of 3/4 inch birch plywood over the mdf for a nice finishing touch so that I can stain it and put a nice lacquer over the stain? I don't know if gluing the two different materials together will work out ok.

4. I know that i'm going to have to do bracing but don't know how to go about it and how to calculate the space used by bracing, as well
as, the 6" flared port.

5. Do you use polyfill or any type of deadening material in a ported enclosure or is that only for sealed enclosures?

6. I'm looking at a single 6" flared precision sound port for this build since it's the biggest that they make. Will just the one port be ok? How do I mount it to the box since there's no screw holes and how can I get the 43" length that I need with the 90 degree bend since precision sound port doesn't make any 90 degree bends? Is the port velocity ok with this build?

7. What would be a good height to put the sub at? Does it matter? I'm thinking that the box is going to be 40" high x 16" wide x 21" deep.

Thank you everybody! I know that it's a lot but I want to get this beast built!

BTW, on the bottom of the first page that' i'm basing my build off of there's a WinISD file for this driver that you can download and modify if needed. Just make a note that there's a highpass crossover setting in the EQ/Filter section that i'm not sure is the correct setting for me.



Here's the pictures of winisd project (You can look at the bottom of each pic in the project section to see the box, port, filters, signal, etc. settings):

 

[Audiophile1178]

One other thing... If I'm aiming for 3.6^3 ft how much bigger do it need to make the box to acomidate the displacement of port, sub and braces? I know that the sub displacement is .09^3 ft. I know the displacement of the bracing depends on how much bracing is being done but I don't know how much bracing I need to do or how to go about it. If I go with with 3/4" birch plywood and double it up making it 1.5" thick do I need to do a lot of bracing?


Thank you in advance to anybody that responds!

BTW, I tried to modify my original post but once I put the pictures in there's no button to edit the post anymore... I don't know what that's about...

 

[annunaki]

Overall it looks to be a pretty sound design. It appears you have looked at most all the variables needed.

2. Over excursion: You may have some concern only during very large peaks in output but it is not likely to be a real issue. Remember that you really only need about 500 watts rms to extract full potential from these drivers. The headroom you have on tap is perfect however and I do not think it will be of much concern for you.

3. Yes, you can build out of 3/4 mdf and cover in birch. Rather than a direct laminate of the mdf however, I would suggest the addition of a constraint damping layer. This will render the enclusure acoustically inert when executed properly. You will want to add some window style bracing that locks all 6 panels together in some fashion. For ideas you can look at some of the build threads in my signature.

4. Calculate bracing displacement by first figuring the volume of each piece of wood that is used to make the braces. Then subtract the volume of the pieces you cut out of the brace material.

5. I would put some deadening material inside the enclosure primarily behind the woofer. I would not cover more than 50% of the interior surfaces with material such as rock wool, mineral wool sheets, or acoustical foam.

6. A 6" flared port looks to be ok here. Personally, I like my designs not to exceed 17m/s vent velocity with the amount of power I have planned for the build. Vent compression begins to set in after this point. However, in your case, and under normal conditions, 22m/s looks to be more of a worst case scenario. I would back your power input down to 500 watts and see what it looks like. My guess is it will come in under 17m/s. I would also be shocked if you would be listening to music or movies with over 700 watts of continuous input power so I think you are fine here.

7. The height is not going to be of huge consequence. If it will cause you personal worry then I suggest some in room testing prior to executing your build to determine the best height at your planned placement locations. Otherwise do not worry about it, looking at your planned design.


Overall these should perform really well in your space. If they are well constructed, they should impress.