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Discussion Starter · #1 · (Edited)
After lots of great advice from Mike P. and many others on this thread: http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/23124-looking-driver-general-sub-advice.html , I finally started my build a couple weeks ago. Here is a summary:

Dayton RSS390HF-4 15" Reference HF Subwoofer
Room dimensions: 15'x20'
Music/HT: 50/50
Amp: Bash 300W plate amp
Sub volume: 8.56 cubic ft.
Dimensions: 1’-11”W x 2’H x 3’D
Tune: 18 Hz

Front firing, both driver and 2 4” ports, due to end table design and no other exposed sides.

For ease of construction I will use plywood (3/4"). This will allow me to use simple, strong butt joints. The second phase of this project will be adding false legs and apron and a top to make it into an end table. The front will have black speaker cloth hanging between the legs. Therefore, no part of this box will show, so I plan on simply gluing and screwing it together, only using clamps for alignment and wherever screws are impractical. I offset the two halves of the horizontal brace to facilitate screwing. The use of screws should allow me to complete this with fewer pauses to wait for glue to set.

I have line level wires running to the sub (behind the drywall), and my A/V receiver has a low level sub amp output, so I am planning on putting the Bash amp in my A/V cabinet, rather than in the sub. I found a nice plate amp enclosure design on eBay that I will copy.
 

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Discussion Starter · #2 · (Edited)
Here are two pics after my first build day (well, partial day -- I have kids!). The inside front is routed and has t-nuts installed and is glued to the bottom. I started on the vertical divider. I routed half the depth of the driver hole at the required diameter (14") and then reduced the diameter to about 13 3/4" for the rest to provide more wood to support the mounting T-nuts. After test fitting the driver and marking the mounting hole locations, I drilled for the T-nuts and pounded them in. I drilled the holes 1/4" and then larger from the back to T-nut depth. I think I should have just drilled all the way through with the larger bit, because it is a little difficult to get the cap screws to thread properly, since they fit tightly in the holes. I found that threading them from the back of the t-nuts and screwing them in until they are though the front leaves threads in the wood that then make threading from the front easier. Larger holes would have been simpler though.


 

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Discussion Starter · #3 ·
Second build day

Started the second day by skeletonizing the vertical brace and then gluing it and screwing it to the front and bottom. The advantage of a paint grade build is that I don't have to mess around with dadoes or biscuits. Instead of being careful with dado placement though, I have to use alignment aids. I simply clamped the cross braces and horizontal braces to the bottom and front and tapped things with a mallet until they lined up, drilled pilot holes, and then glued and screwed. I am using 2" coarse drywall screws. Although they are brittle, their threads have great holding power, and once the glue is dry, they won't really be doing anything. After gluing and screwing, I removed the alignment aids and wiped the glue off of them.



I then clamped one pair of bottom cross braces in place, lining them up with the help of a 6" machinist's square. I drew pencil lines on the bottom and vertical brace on both sides of the cross braces to help re-align them after glue application. That worked reasonably well, except that the glue squeeze out tended to cover up the lines. I drilled pilot holes (the full depth of the screws), un-clamped, applied glue, re-clamped and re-aligned, and screwed them in place. BTW, I was taught by a master cabinetmaker to apply a bead of glue down the length of an edge and then spread it with my finger to fully cover the edge. Don't rely on the squeeze to do the spreading for you. I know there are glue applicators with built in rollers that probably work well too, but my finger has always worked for me. :T



As the pictures show, I offset the cross braces to allow easier drilling. That worked out well. I also made the braces on one side taller than the other, so I could do the same thing with the horizontal braces. The next pic shows the horizontal braces in progress. I used the same radius for the circular cutouts in the bracing that I used for the larger part of the driver cutout (7"), but set the center back about 3/4" from the fronts of the braces to get the desired clearance. For the horizontal braces I screwed them down to a scrap of MDF with a scrap of plywood in between to align them and provide something to nail the pivot into. This pic shows that done along with skeleton layout and holes at the cutout corners.



A cabinetmaker trick is to mark pieces during dry fitting to ensure correct positioning later. You can see one of these marks at the front edge of the horizontal brace on the right. I drew two sides of a triangle on the brace and the same thing on the front where it meets. You can put matching letters inside the triangles or use different symbols at different mating points. I think I just drew a line on the other brace. It's not foolproof, but can help a fool avoid mistakes.
 

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Discussion Starter · #4 ·
Second build day continued

Here is a picture of the horizontal braces glued and screwed in place:



One advantage of using screws is that you need fewer clamps. A bigger advantage is that glue ups are much less stressful, because you are only gluing one piece at a time. That can lead to fewer mistakes. Any mistakes made will also tend to be less disastrous, because you aren't dealing with a multitude of pieces and clamps. It works out well for my design, because I am building a paint grade box that will then be disguised as/covered with an end table. However, it seems that the internal parts of any build could be done this way, since none of it is visible. Then, the outer parts could be glued and clamped over the bracing. In any case, I would recommend plywood over MDF for internal bracing as it is stronger and glues up stronger. It is way better for screwing, as MDF tends to delaminate.

Here are some more pics after horizontal brace installation:



And after the addition of the upper cross braces:




I used the word "foolproof" before. Unfortunately, nothing is foolproof. I made the outer parts of my braces about 2" wide and the internal parts about 1" wide, since the internal parts join to other parts that reenforce them, and the outside needs to be strong to brace the outer parts. Well, I was rushing at the end of the day and installed the last set of cross braces upside down. I didn't notice when I was dry fitting them, nor after they were glued in. It was only about an hour later when I took the pictures that I saw my mistake. At that point it would have been pretty destructive to tear the joints apart, and the bracing still seems pretty substantial, so I decided to leave them alone.

All in all, I'm pretty happy with how this has gone. I can't wait to hear it! I ordered the amp a few days ago, and that will be here before the speaker is done. I made some more progress over the weekend, adding the ports. I'll post about that tomorrow.

Cheers!
 

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Really nice build, and very nicely planned. I think despite the vented design, I'd still caulk the enclosure against extra leaks, but other than that, this thing looks perfect!

Tom
 

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I agree with Tom on the sealing of the enclosure situation. If the box is not completely sealed besides the port. It can ultimately change your tuning freq. a bit. Looks great so far though.
 

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Discussion Starter · #10 · (Edited)
Thanks, guys. It seems like the joints are air tight, since there is a bead of glue squeeze out, but I will probably caulk the seams I can get to. Caulking all of the last side may be just about impossible.

I'm working from home today, but I can hear the speaker calling me. May have to take a little leave to work on it!

Here are some more progress pics. I found some videos online with instruction on flaring a PVC port by softening the end with a heat gun and pressing it over the bottom of a metal mixing bowl to flare it. I liked the idea of not having to glue on a dissimilar material. It worked out pretty well. I did it outside to reduce the breathing of toxic fumes.





The inside ends of the ports will be raised so that they are not too close to anything inside the cabinet. To avoid aiming them down into the carpet, I also bent them in the middle. That worked okay, except the PVC tended to buckle on the inside of the bend. The first one buckled out, which wasn't so bad, but the second one wanted to buckle in. I fought it by pushing it out with a piece of wood. They came out okay, but next time I will follow lsiberian's advice and just miter and glue the angles.



As you can see from that last pic, the ports are exiting near the rear cross braces. Mistake #3 (and counting). I probably should have moved that back cross braces towards the front, so that the ports would exit beyond them. Oh well, maybe next build. I hacked out some of those braces to provide more clearance. I used a sawsall for the cuts and a belt sander to round over the edges. The pristine beauty is gone, but nobody will know, except for all of you.

The ports are all caulked in. They seem solid. I don't know if I should provide support for the ends to eliminate any vibration. They are very solid, but...


 

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You can never be too over the top with making sure the joints are sealed. There's always one pesky leak. Looking great so far

Jason
 

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Discussion Starter · #12 ·
Thanks, Jason. I will follow your advice.

My amp just came. Feels like Christmas. Definitely going to be hard to not work on the speaker and amp enclosure today, since I'm working from home.
 

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Discussion Starter · #15 · (Edited)
Thanks for the compliments. Here is the youtube video of the method that I used (not my video):

It does not result in flares with a perfect radius in the cross section, but I think it is good enough to eliminate chuffing, and I only did it for the internal flares. I will round over the second layer of plywood for the external flares. If you want something prettier, here are a couple of links to folks who built a radiused mold to use instead of a mixing bowl. The second one really shows off the result:
http://www.subwoofer-builder.com/flares-25mm.htm
http://www.hilberink.nl/codehans/tannoy7.htm

I made sure to buy Schedule 40 drain pipe, since it has a lower melting point than pipe made for higher pressure.
 

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Discussion Starter · #18 ·
Re: tstewart's RSS390HF-4 with Bashttp://www.hometheatershack.com/forums/images/editor/menupop.gifh 300 Sub Build



I got my sub to a working state over a year ago, but neglected to finish up the thread. This shot shows the sides, back, and top already glued and screwed together. As I explained earlier in the thread, I intend to turn this into a coffee table by adding legs, apron, and top over this box, and to paint the parts of this that will show between the legs black. I planned also to hang some speaker cloth a few inches in front of front (this is front-firing). It will be sandwiched between walls and a couch, so the other parts won't really show. My plan has changed, but more on that later.

This shot shows that the sides, back and top have been glued and screwed on. Beautiful spackle job too. Here I am gluing the front on over the front baffle. I decided not to screw on the front, since it would get more attention than the sides. I just glued and clamped it. I don't remember if I used a few pin nails to keep it from sliding around. I used spring clamps around the speaker and bar clamps around the outside. Before I glued it on, I thoroughly sanded the circle around the driver, put on some spackle and sanded again to get it smooth for later painting. The pic below shows that after I unclamped it. I later cleaned out the glue squeeze out. You can also see that I had cut the holes for the ports a little small. A later pic will show the ports after routing around the inside of it.

 

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Discussion Starter · #19 ·


In these pics you can see how the ports looked after I routed them flush and then rounded them over and sanded. After seeing how nice it looked, I decided I would stain it a lighter color to show off the wood grain. You can also see pillow I stuffed in one side. I wasn't sure if it would be better or worse with it, so I hedged my bets and just did one side.
 

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I'm thinking very hard about building two of these. What I haven't seen is your impression of the sound. I currently have one dual opposed sealed box with the RSS390HFs in them and was considering a duplicate one to eliminate some cancellation problems in my room. But, I mainly use the subs for HT LFE. My B&W 804s carry most of the Stereo music signal and I use the Sub for just a little bass extension when in the Stereo High Fidelity listening mode. What is your opinion with this design considering my application description?
 
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