My first sonosub. (1 Viewer)

[Brent_S]

Sam,

reread my suggestion for the DVC12. It was a ported cabinet: 3ft^3 box tuned to 20hz. Anything that nets (box - port/driver/bracing) between 2.75 and 3.2 ft^3 tuned to 20hz is pretty much the same. There's less than 1db difference in max output across that range at 20hz...bigger is louder. The actual dimensions to get the necessary box volume are a matter of taste.

The ideal sealed cabinet for the DVC12 is more like 1.75 ft^3. It should sound quite nice in 3 ft^3 sealed, but you can push it *just* past max excursion with 240 watts at frequencies below 30hz. At 1.75 ft^3, it should handle everything the SA-240 can put out...almost a perfect match. Build the ported box and plug the port(s) to experiment with the sound. You may like the sealed better for music and ported for HT...just watch out for bottoming when you go sealed; you're still good for 98db@20hz, 105db@30hz before any room gain. There's usually less content below 30hz in music (depending on genre) than action movies which will also help protect the sealed design from over excursion if you only go sealed for music.

I haven't done the math, but have seen lots of projects that use the DVC12 downfiring.

wbs

 

[SamNavy]

I wonder how I missed that... well, better late than never, thanks Brent. One last question and I think I'll have it.
I finished the box today. After some trimming and fitting, it ended up 20x19x19.5, which works out to 3.37cuft. After the bracing and driver subtraction, I think I'll end up at about 3.1. I've decided to go with front firing and placing the port(s) also on the front. Now... about those port(s)...
If I'm working winISD correctly, assuming 20hz tuning and a 2" diameter port:
1 port= 5.3"
2ports= 12.2"
Does that mean if I go with two ports, they both need to be 12.2", or do I make each one 6.1"?
I've got plenty or room to go with 2 at that lenght. Aesthetically, I like the look of two ports, but a single would be simpler. Whaddya think?

 

[Robert_J]

That means 2 ports, each 12.2" long. Just like it says. Also, two 2" ports don't have as much port area as a single 3" port so you will still be under-ported.

-Robert

 

[Brent_S]

Listen to Robert...you're way under ported at 2". Even a single 3" starts to exceed the general air velocity recommendations at max output, but would probably be acceptable 99% of the time. Two 3" or one 4" port makes air velocity a non-issue. 2@3" gives you roughly the same port velocity as 1@4", but the 4" port actually consumes a little less cabinet volume.

Both 2@3" or 1@4" will require an elbow to stay within your cabinet dimensions. I've read the correction factor for using elbows somewhere, but now I can't find it...best advice is to determine the average length of the path through the elbow (inner is shorter than outer) and find the widest radius 90 degree elbow you can to smooth the airflow as much as possible. SV uses elbows in some of their models so don't worry about it limiting performance if you decide to go that route.

In addition to elbows, the port works equally well if it extends outside of the cabinet. Depending on your decor and room placement, this might be an option if you can hide the port by facing it towards a wall.

For the math, 2.9 ft^3 needs a 4"x26.15" port for a 20hz tuning. That port consumes .19 ft^3 if my math is correct (not counting wall thickness of the port). Using your calculations of 3.1 ft^3 after driver/bracing but before adding ports, you're pretty much right on the money.

Now, if you want to simplify things like port noise and bending ports lengths and you have a $45 left in the budget. You can replace those ports with AE Speakers PR15-1050 passive radiator: http://yellow.mynethost.com/~bv12636...667424f0cb5dc3
As shipped, it will tune your 3 ft^3 (3.1 - .1 for the PR)box to 17hz. The overall response numbers match the 1@4" ported box with 1db or so. The biggest problem there might be actually getting the PR shipped...there have been some reports around the DIY forums of iffy shipping times from AE...never done busines with them myself. Parts Express sells a PR based on the DVC15 for $80 that you could tune with additional weight.

wbs

 

[SamNavy]

I'm on my way down to Home Depot now for some port material. I'm going to go with a 4" port and mount the opening below and offset to one side of the driver to avoid my bracing. A section of pipe, long elbow, and street elbow should do it. Then she's all ready to be "finished", just waiting for the driver...

Well, just got back from HD where I changed my mind and bought material for 2 3" ports... and now that I'm at home, I've decided to go with 4" again... HD is only about 5 mins away, lucky me! I guess that's why they call it DIY!
Off again...