SI HT18 D4 16cuft 15hz build - Page 2

With a protective highpass at 15hz air velocity peaks a little above 30m/s with 1000 watts, I feel that is an acceptable velocity number. Keeping the first port resonance well above the subwoofers bandwidth to minimize any detrimental effects from said resonance was also a goal, in this case is comes out to be just about 340 Hz.


Some very cool custom parts arrived for these yesterday, but no teasers until I get to the point when I can install them.

Today I started laying out and installing the bracing on the first enclosure. I also marked the driver mounting hole positions and drilled some holes for the hex drive wood inserts that will be used to mount the drivers.






I got most of the bracing glued in on this one tonight. I still have 4 more of those horizontal braces to glue in and another 4 braces that will run lengthwise to both cut and glue.




Edited by mtg90 - 2/16/13 at 8:39am

Thanks Brian, the basic design shape was zheka's idea though it does share the recessed driver baffle with yours.

You’re very welcome Gene. The L-shaped bracing makes it easier to glue the braces together and also keeps them strait as the plywood had a tendency to warp when cut into such thin strips. I feel like this style of bracing installed much faster then the bracing I did on mine.

So over the week I finished up the bracing for both subs.






I also installed some t-nuts for the rubber feet that will get put on later. I glued them in using hot glue, my favorite glue BTW, I've even assembled am entire enclosure using only hot melt glue I will use Teflon on the bolts for an air tight seal.




I also made the cutouts for the terminals. They are going to be dual binding post terminal cups so the coil wiring configuration can be switched just by moving the jumpers around.




Yesterday I got around to putting some dampening material in. These huge boxes almost used up the rest of my denim. I placed it around the middle of the enclosure vs. the walls as that is where it should be most effective at killing any unwanted midrange resonances/harmonics.




Then I glued on the last panels, and finished up for that day.





I also found someone else who likes them.




I had to install some doors at my grandmother’s today so half the day was used up doing that but I did manage to flush trim and apply some filler in a few spots that needed it.




I'll have to see if I can get to the first coat of duratex tomorrow.

Thanks BA,

Actually the switch does nothing, the coils can be wired in different configurations (series, parallel or each coil separate) by changing the how the jumpers are positioned. That terminal cup just costs half as much as the normal bi-amp cups.
http://www.parts-express.com/pe/showdetl.cfm?partnumber=269-080

Although a series/parallel coil selector could be setup with a DPDT switch but you loose the option of driving each coil on its own.

I am unsure if I will leave that little switch in there or pull it out and tape the hole.


I really hope not.
Edited by mtg90 - 2/23/13 at 10:22pm

I had originally planed on using strait 2.5" wide strips of plywood but after cutting them I decided it would be too hard to attach them to each other where they cross, also some were warped a little bit which makes it even harder. I ripped each one into a 1.5" and 7/8" strip then glued them together to make the L-shape. It worked out really well in the end although I did had 100+ pieces of bracing to glue together

I am working on applying the second coat of duratex now, I am worried if there will be enough for three coats so I am taking my time trying to get the second one looking really good. I'll get some pictures up later today.

The duratex on this one is finished I still need get one more coat on the top and a side on the other cab. I should be able to get that done, install the rest of the hardware/drivers tomorrow and get some pictures of the finished cabs up.

I will say duratex is one of the harder finished to apply without getting roller lines in the finish. You can see some faint ones on the top and side in the photo; I don't think I have to technique mastered just yet. I do like how quickly and tuff it dries though.

I would use duratex only if I wanted the durability it offers or the texture/covering ability without needing primer.

My two 10cuft subs I just used some cheap black latex paint from Menards ($15 a gallon) and I think they turned out great. I put three coats on those two enclosures and used about 1/4 the gallon, though the finish is not nearly as durable as the duratex and I needed to use primer.

Primer: Zinsser FastPrime 2, Water Base Primer This stuff works great on MDF only needs one coat then sanding and its ready for paint.
Paint: Lucite Interior Acrylic Latex Satin Paint The guy in the paint department added three times the black pigment recommended as it is more of a dark gray normally.

I also like Rust-Oleum’s latex paint which seems more durable then the cheap latex but the largers size I have found it in is quarts. Rust-Oleum Painter's Touch Multi-Purpose Flat Black

Their oil based flat black is even better then the latex for durability but it is more of a mess to clean up. Rust-Oleum Professional High Performance-Flat Black Low VOC

One other I want to try is this stuff: Conco Interior Exterior Flat Acrylic Water Base Paint But my other black latex will last me a while.

They are done











Here is a close mic response of one as well:

Thanks guys, I only tried one out for a little bit last night and not even setup correctly or anything just sitting in the middle of the floor. Your could feel your pant legs flapping from 6' away during the mech scene on Terminator Salvation and that was with one channel of my old Sony receiver for power.

The pair with some decent power should be awesome.


I think where I had the mic positioned (between port and driver) may have amplified those notches there, I took some more measurements further back and they smooth out quite a bit. There may be some internal reflection/cancellation happening but I am sure placement in the room will have more of an effect on the overall FR.

This is at 6", 1', 2', and 3'