# Jon F's Dual 9.8 ft3 CSS SDX15 Ported Box Build



## Jon F

I'm working on a build of two CSS SDX15 subwoofer boxes for my almost-finished home theater. This is my first time building a speaker box. My previous sub was a Dayton Titanic 10" kit sub with a pre-assembled cabinet. I don't have much woodworking experience so I was a little nervous about screwing up something. So far, things seem to be going pretty well. :R

The plan is to use two 9.8 ft3 ported boxes tuned to ~18hz in my ~1200 ft3 home theater (11.5x13x8). I've already bought a Behringer EP2500 amp and a Reckhorn B-1 subsonic filter to use with the subs. I know that this setup is overkill :dizzy: in such a small room, but I like symmetry and two is almost always better than one. :dumbcrazy: I decided on a 6" PVC port for simplicity, as I was able to pick it up at a local plumbing supply place. With my intended box dimensions (28w x 25h x 32d), an 8" port would be impractical. Modeling shows that I could be on the high side for port speed, but I plan on flaring both ends and I don't think I'll ever run enough power through them to have port noise issues. Real world testing to come later. :whistling:

The box build has given me the opportunity to buy a few new toys, including a new Bosch dual-base router, a Jasper circle jig, and a Harbor Freight dust collection system. :spend: I already had a table saw but I added an extension table to it using scrap MDF. Add router bits, dust collection accessories, wood, the speakers, the amp, the subsonic filter, odds and ends, and it's been a tough month or two for the wallet. :spend: :dizzy: I guess someone has to keep the economy going. :joke:

At my current work rate I expect to be done in about a month, more or less. I have some unique ideas for finishing because of the intended placement near the front of the room under the screen. More about that later. 

Some pictures and updates to follow.


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## Jon F

The obligatory size-reference shot with the subs.









A sketchup of the box.









Another view of the sketchup of the box.









WinISD modeling. Remember that there will be two of these.









The FR graph.









Cone excursion at 600w with a 10hz ssf. I don't intend to ever run the sub this hard.









The dry-fitted box sitting atop the table saw. This gives you some idea of the scale. I was a little shocked at the size when I first did the dry-fit. Also a shot of my high-tech DIY extension table. I can rip to 36" wide now, though!









Another view of the dry-fitted box, with a tape measure for some scale.









Dry-fitted bracing. These will have different placement in the final box, as the port should be in the 18" range. I may shuffle the bracing arrangement around a little and use more poplar bracing on the back-half and MDF on the front half as port support.









The first port holes and front speaker holes cut.


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## Rodny Alvarez

Nice set up Jon!!!!:T




> Cone excursion at 600w with a 10hz ssf. I don't intend to ever run the sub this hard.


:rofl:


:bigsmile:


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## Mike P.

Looking good!


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## Jon F

Thanks guys! I'm really enjoying the project so far. I would have started a few weeks ago but I was doing some spring cleaning in the garage. I'm almost done reorganizing. I put a few things up on Craigslist and I've almost cleared out all the stuff that needs to be donated/sold/tossed. Added shelving and sorted all my stuff into bins. I also had to do a few modifications on the table saw to improve the dust collection capability. MDF dust was getting everywhere! :gah:


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## looneybomber

Is it too late to add bracing to that rear wall? Your side walls are very well braced, but I don't see anything on your rear.


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## SteveCallas

> Cone excursion at 600w with a 10hz ssf. I don't intend to ever run the sub this hard.


Plan on 1000 watts per sub as a worst case.....your usage and expectations will change a lot between now and a few months after the subs are done. You'll be listening louder than ever before, I can guarantee it :T


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## Jon F

looneybomber said:


> Is it too late to add bracing to that rear wall? Your side walls are very well braced, but I don't see anything on your rear.


I'm going to be running hardwood bracing front-to-back. I was just too lazy to model it.


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## Jon F

SteveCallas said:


> Plan on 1000 watts per sub as a worst case.....your usage and expectations will change a lot between now and a few months after the subs are done. You'll be listening louder than ever before, I can guarantee it :T


I don't doubt that I'll be listening louder than I was with my 10" Dayton. :heehee: If I bump the ssf to 12hz the excursion will be under control at maximum output of the EP2500. By then I should be getting structural issues. :hsd: At that point, the worst spec in my setup will be port speed at around 32.5 m/s.


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## nab9524

How is your build coming along? I am contemplating building one of these as well, so I am curious to see how it turns out. I have a similar size room, but will one build one in a slightly smaller box.


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## Jon F

nab9524 said:


> How is your build coming along? I am contemplating building one of these as well, so I am curious to see how it turns out. I have a similar size room, but will one build one in a slightly smaller box.


I cut a bunch of the hardwood bracing but other than that haven't had time to make much progress. It's kind of a slow build, and I figure I won't be done for about 4 weeks. Also, I ordered a new jigsaw to cut the MDF bracing so I'm waiting for that to show up as well. I'll update the thread once I start cutting the bracing and gluing the box up.


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## Jon F

Well finally an update. A week-long vacation and a busy time at work has kept me from getting done but I've been able to make some progress. I managed to finish the bracing for one of the subs. 

This is the test fit of the SDX15 in the front baffle. Basset-approved. :bigsmile:









A little more detail of the bracing arrangement:









I also cut and applied the foam lining:









And more of the foam:









For the first box, I still need to finish the inside and outside port flares, attach the binding posts, drill out the driver mounting holes and install the T-nuts, and glue it all up. I think I'll be able to finish that up this weekend and then I can get started on the second box, which I hope will go a little faster.


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## its_bacon12

That looks outstanding.

I'm very jealous


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## tcarcio

Those are going to be monsters.....:T


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## SteveCallas

That's probably the most impressive bracing I have ever seen. Nicely done :hail:


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## Jon F

Wow, thanks everyone! Time to get back to work!


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## Jon F

Update time! Made some progress over the weekend. 

The obligatory clamps everywhere pictures:


















You just can't have enough clamps. :R I'll probably pick a few more of the longer ones up for the second box to make my life a little easier. 

Here's a little detail of the front of the port. The flaring was done with a 3/4" roundover bit. The rear of the port got the same treatment:









There is a lot of finish work to complete on the box, including trimming off some edges with the router, sanding, painting, etc. But while I finish the second box I figured it couldn't hurt to use the first one. :devil:

Here's where it will sit, more or less. It's really impossible to get the feel of the scale from a picture. In the room, it looks enormous. Two is going to be borderline hilarious. :gulp: 


















The sub sounds great! It's pretty incredible how much air it is able to move at about 15hz. I do have a bit of a hum problem that I have to get sorted out, but it's nice to feel that the construction came out well enough to actually work. Because I've had a chance to test it a little, I feel a lot more confident about starting the second box.

My unscientific impression is that the box has very flat response at the listening location. Compared to the 10" Dayton I was using before, there seem to be much smaller fluctuations in the response curve. I won't do any serious testing and tweaking until I get the second box finished and in place.

Thanks to everyone so far for the help and support! :T


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## Ricci

Looking great. Nice work on the execution of the enclosure. 2 of those aught to provide a very nice low end anchor for your HT. What are you going to do for a finish? Nearly everyone seems to have to battle the dreaded hum issue.


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## FNG212

Very nice craftsmenship.

Did you keep records of a cut list?

If you did it again, would you increase the port to 8"?


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## Jon F

FNG212 said:


> Very nice craftsmenship.
> 
> Did you keep records of a cut list?
> 
> If you did it again, would you increase the port to 8"?


Thanks! I didn't keep a cutlist but I still have a second box to build, so I've got all the pieces disassembled. The size is very specific for my location, though, so I'd recommend following whatever needs you have size-wise and building the box to your own specification.

I haven't spent too much time with the sub because of my work schedule, but so far I haven't noticed any port noise, even on a 15hz test tone. An 8" port would have required an elbow in my box which would have added some complexity. After I finish the second box, I'll be doing some more serious testing and equalizing and I can give you a better idea of whether the port was too small or not.


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## Jon F

Ricci said:


> Looking great. Nice work on the execution of the enclosure. 2 of those aught to provide a very nice low end anchor for your HT. What are you going to do for a finish? Nearly everyone seems to have to battle the dreaded hum issue.


Thanks! I'll be easing the corners and then painting the box black. I haven't decided whether to use a speaker grill or not yet. The top and sides are likely to be covered in fabric to minimize reflections from the screen. No firm plans yet, though.


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## FNG212

Very nice craftsmenship.

Did you keep records of a cut list?

If you did it again, would you increase the port to 8"?


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## Jon F

I finished the second box last week, and now both subs are essentially done. The subs got a basic coat of flat black paint and then we covered the top and both sides with the same type of black velvet used on the masking system for the screen. Because the subs are right underneath the screen I was worried about reflections even with a flat paint, and the velvet is much better about reflections. The finish isn't perfect but I still don't know whether I will be using a grill or not, so it may not even matter. Overall I am extremely happy with how they turned out aesthetically. I'm waiting to pick up a new receiver with Audyssey to do any EQing and will just set the basic levels with HD Basics in the meantime. I'll update the thread after I do adjustments. First impression is that the second sub added a lot of volume.

Please excuse the fingerprints and uncombed velvet nap.


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## Fabricator

nice ...........:hsd:

let me ask you. the holes in the driver, and the holes in the trim ring. did they line up ?

did you use the humongous gasket ?


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## Jon F

Fabricator said:


> nice ...........:hsd:
> 
> let me ask you. the holes in the driver, and the holes in the trim ring. did they line up ?
> 
> did you use the humongous gasket ?


The holes lined up almost perfectly. Certainly good enough for the small screws I used to hold the speakers in. I didn't use the huge gasket because my girlfriend threw it away! :rolleyesno: I just used a speaker gasket kit from parts express.


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## Fabricator

lucky you. i have 2 sd12's. the holes don't line up  . the driver holes are larger diameter . caused me issues. i didn't use small screws, i used larger allen head bolts.


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## Jon F

I know the SDX15 has to be drilled out to accept the 1/4" allen screws that many people use to mount their speakers. I took a chance on wood screws. If they pull out, I can always add T-nuts later without too much trouble.


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## Fabricator

yeah, i had to drill mine out, no big deal. its just the holes didn't line up. i can post a pic, if you wish (this is your thread).

i tried the nuts from parts express. the one that press into the wood from the back side. i had issues. 
i went to HD and got the ones that screw in, worked tons better ! ymmv


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## Sonnie

Very nice and clean work Jon... impressive!

Have you broken out REW yet and measured your response?


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## Jon F

Thanks, Sonnie! I haven't gotten around to doing any measuring yet, but I'll update the thread once I get around to it. All I've done so far is set the level of the sub using my Radio Shack SPL meter and the pink noise tests from HD Basics.


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## looneybomber

Wow, nice bracing! Oh, and yours came with a gasket? Mine didn't, but I also bought mine around 2yrs ago so maybe they weren't included then. I just use PE gasket tape.


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## Jon F

Thanks! Yeah, each speaker came with a huge gasket about an inch thick. I don't know whether it would have worked or not, but I used PE gasket tape too.


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## Scaper

Jon F said:


> Thanks! Yeah, each speaker came with a huge gasket about an inch thick. I don't know whether it would have worked or not, but I used PE gasket tape too.


Are you sure that was a 1" thick gasket? Could it have been part of the packaging?


Just curious, are you going to try standing those big boys up in the corners to see how the response changes? They look like they'd fit and it would be interesting to see how much difference it would be.


Nice build by the way. Those drivers are massive.


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## Creative Sound

Hi,

That is part of the packaging. We added that because there was a weakness there if the box was dropped exactly in the "wrong" place.

Bob
Creative Sound Solutions


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## Jon F

Scaper said:


> Just curious, are you going to try standing those big boys up in the corners to see how the response changes? They look like they'd fit and it would be interesting to see how much difference it would be.


There is no room for them to move anywhere else. The corners have bass traps and the front speakers are less than a foot from the wall. The subs were designed to fit exactly where they are. I hope they equalize well, because they have nowhere else to go. 



Creative Sound said:


> That is part of the packaging. We added that because there was a weakness there if the box was dropped exactly in the "wrong" place.


That makes sense. I only saw the ring once for a few seconds as I unpacked the drivers and then they were tossed later in the day. I thought I read somewhere else that they were the gaskets but maybe I'm misremembering.


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## Fabricator

i said they were gaskets. seems i was mistaken. but, they look like they would be good gaskets


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