Ported 12" Dayton Subwoofer, help

[russforrest]

I am looking to possibly replace my NHT Classic 12 Subwoofer with something of my own making. I am thinking of using the Dayton Reference HF 12" as the subwoofer for the application. I would really like to go with a ported design and I think that a box 17"w, 18"h, and 22"d should work but I would like to know how many and how large of ports should go in the box.

I had looked on a website that did the calculations and it said that 2 - 3" ports, both 13.75 inches long would do it but I wanted some other opinions or calculations to verify/discredit this calculation. If this is wrong, what would you guys recommend?

I am looking at using either the O Audio 300 watt BASH amp or the BASH 300 watt amp on PE to power the driver. This amp has been knocked for air leaks in a sealed application but since I am looking at ported I thought it would be ok.

Below are links to the equipment I was looking at:
Dayton Reference HF 12 - http://www.parts-express.com/pe/show...number=295-464

BASH 300 Watt Amp - http://www.parts-express.com/pe/show...number=300-750

O Audio 300 Watt BASH Amp - http://www.oaudio.com/300W_SUBAMP.html

This should be enough power for this application right? Also, any other design tips would be appreciated.

One other thing, if my calculations were off and this driver won't work with this setup please let me know.

[brent_s]

You're probably going to need a slightly bigger box. Your dimensions produce a box with internal gross volume of 3 ft^3 using .75" material. When you model a subwoofer, the software is using net volume...gross internal air - driver/bracing/port. You treat the port as a solid cylinder. Otherwise, the 315HF-4 looks good in 3-4 ft^3 tuned around 20Hz, IMO. I run a pair in 3.5 ft^3 net (each) tuned to 17Hz...using a slot port, external dimensions end up around 17.5" x 16" x 32".

Either BASH300 should be fine, the OAudio version is identical except for variable phase instead of fixed...P-E version works fine in a sealed alignment, IME.

Try to go with the equivalent of a 4" port (flared preferred). A quick and easy port calculator can be found here. To tune 3 ft^3 to 20Hz, you'll need a 4"x26" port...that's .24 ft^3 by itself.

-Brent

[russforrest]

volume

So if I Increased the depth to 26" my calculations show a volume of 4.6 cubic feet before port and displacement. That should be enough to get a subwoofer and one or two bracers in the box with the port correct?

[russforrest]

sorry, that is the external, the internal is 3.515 cubic feet after the 1.5" on front baffle so the subwoofer can be flush mounted. Does that sound right?

[russforrest]

one more calculation

I did one more round of calculations and based on an interior box volume of 3.94 I should be able to use a single 4" port 18" long to tune to 20 hz. Can anyone verify this math? This would make the exterior of the box 19.5h, 19w, and 26d based on 1.5" front baffle for flush mounting. The internal volume would be slightly more with a 1.25" front baffle, still for flush mounting.

[russforrest]

sorry I keep posting, but if I wanted to constrain the box dimensions a little and go with a box that was 17w, 19h, and 24d would tuning it with a 3" port at 14" be roughly 20hz? The reason I ask is because I was measuring my available space and that is just about all the larger I could get in the space I have for the subwoofer. That takes into account being a few inches from the back wall and about 2 feet from the side wall, the sweet spot for my room.

[brent_s]

sorry I keep posting, but if I wanted to constrain the box dimensions a little and go with a box that was 17w, 19h, and 24d would tuning it with a 3" port at 14" be roughly 20hz? The reason I ask is because I was measuring my available space and that is just about all the larger I could get in the space I have for the subwoofer. That takes into account being a few inches from the back wall and about 2 feet from the side wall, the sweet spot for my room.

The numbers add up pretty well. 3.25 ft^3 gross, .15 ft^3 for the driver, .08 ft^3 for the port, add a piece or two of R-13 to compensate for the bracing and you should have 3 ft^3 tuned to 20Hz.

However, the 3" port is significant compromise. Depending on how loud you listen, you're at a fairly significant risk for port noise due to the high air velocity produced by the smaller port.

Can you handle a 20" cube? I love the RS subs (have a pair of 315HF-4s in my theater room, sealed 315HO in my living room), but you might be a good candidate for Bob's Trio12/APR15 kit. The same cabinet design & PR could be used with the 315HF as well, although I prefer to mount drivers vertically instead of horizontal. A PR works like a port, except it doesn't consume much internal cabinet volume and no port noise, but it adds cost.

-Brent