Official Value Buster Subwoofer System design info thread.
As the title implies this design allows you to get lots of bass from an inexpensive driver an easy to build enclosure with flexible tuning and allow for multiples to be powered from a single iNuke amp (or NX series which has replaced the iNukes).
The driver for this design is the Dayton PA460-8, an odd choice for a subwoofer design you might say. True, but with the right balance of enclosure, power and proper EQ it does amazingly well. Similar to the Magnum-12 woofer in the Flex-12 the PA460 is very efficient in the mid bass leading to very little thermal compression and great dynamics in that range. While it is a bit limited in terms of coil overhang it does have a very soft suspension and decent mechanical clearances so there is no trouble pushing it a bit at lower frequencies. I have done thorough testing with the iNuke 3000 and the driver stays safe even when driven hard below tuning with the DSP settings limiting any bad noises from either the driver or the amp when being pushed hard into the limiter as was demonstrated at ENG-399's where a pair was run at reference with the sub trim about 16dB hot.
The enclosure is a fairly straightforward ported box, approximately 6.25 cubic feet net internal. Measures 23.5" wide, 31.5" tall x 20" deep or 20.5" deep if you add an additional 1/2" baffle layer to flush mount the driver. If going with a single baffle layer and surface mounting the enclosure can be cut from a single 4x8' 3/4" sheet of MDF or plywood. Add a 2x4' sheet of 1/2" if you want to flush mount the drivers and ports which is how I built mine.
Here is the cultist for the enclosure without the additional 1/2" front baffle to flush mount the driver and ports. To flush mount the driver all you need to do is cut the outer diameter out of the 1/2" baffle and that will put it flush. Theoretically you could add the second baffle layer at any time without making a new box or adjusting the cuts on the inner baffle.
Note 30" x 2" piece should be cut into smaller pieces to fit between the side to side and top to bottom bracing, I just forgot the exact dimensions which making the cultist. It should be measured during assembly anyway to determine exact length of parts needed.
Here is a look at the bracing I used, feel free to add more or beef it up if you wish, but I found that to be adequate:
I used R-13 recycled denim/cotton insulation with a piece placed on top the port tubes below the driver that is held in by the brace and a couple pieces placed on the walls above and behind the driver leaving space above the ports for airflow. Fiberglass, polyfil or acoustic foam would also be suitable if similarly placed.
The design uses two of the 4" precision ports at full length (17") which makes things very easy. Using both at full length gives you a 20 Hz tuning, if one is plugged you get 15 Hz and if you remove the center extension tubes placing the flares end to end (5" length) you get a 31 Hz tune. If using 4" ports without large flares you would want them to be about 3.5-4" long to give you the 31Hz tune. You can use masking, duct or electrical tape to hold the precision ports together if you want to leave open the option of removing the port extension tube. The proximity of the internal port flare to the rear wall makes the effective port length longer then it would be otherwise which allows for the tuning to come in lower then what it looks like it should calculate out to. For this reason modification of the depth of the enclosure will change the port tuning, you can however change the height and width keeping if internal volume is kept the same or within 10%.
Slot Port Cabinet Options
If a slot port is desired you can build it with a full width slot port that is 1.5" high x 28" long to give you the 20Hz tune. If you add a brace down the middle it will also allow for both the 20hz tune with both halves of the port open or the 15hz tune if one of the halves was closed off.
If just the 15Hz tune is desired then the slot port can be 1" high, full width (22") and 32" long which reduces port velocity and compression compared to the 15Hz mode of the dual tune option. To visualize these adjustments to the below 3d model (showing the 20Hz option) you only need to change the internal slot port panels to 17.5" (from 17") and 14" (from 10") and the height to 1" (instead of 1.5").
If the 31Hz mode is desired build it can be 1.5" high x 8" long, so you only need a single 22" wide x 7.25" long panel to make the slot port.
The VBSS was intended to be used in conjunction with the iNuke/NX 1000DSP or 3000DSP amps. A 1000 can power up to two of these in bridged mode while the 3000 can drive four per channel for a total of eight. This allows you can get a lot of bass without spending big bucks and a rack filled with subwoofer amplifiers. Other amplifiers could be used but there would be a need for external DSP (settings provided) and you would loose the precise tuning of the limiter designed for the Inuke/NX series amps to get the most from the driver/amp combo.
Here is a look at the outdoor 2pi frequency response for the 15hz, 20hz and 31hz modes (with DSP):
Rough idea of the 2pi max output from a single enclosure powered by an iNuke/NX 3000.
Note in reality the 15hz mode does suffer from some port compression which will eat up a few dB near port tune at high output levels:
A zip file with the DSP settings for the iNuke amps is also attached.
*If you have a Behringer NX series amplifer with DSP just change the .arp file extension to .nxp to get them to load in the new software*