|
ABC (DCR) Box question
So I'm trying to design a box for my sub. But I ran upon a couple things that I don't know yet.
Is the net volume to be a 1/3 to 2/3 split of the optimum volume for a standard ported volume. Example: a regularily 1 cubic foot box gets split into .67 and .33 enclosures? Or make the total net volume 1.5 times the original size? so 1 cube and .5 cubes? Also, do the square inches of port get split from the optimum, or is it equaled? Example: 20 square inches of port for standard ported box gets split to ports of 10 square inches, or each port remains 20 square inches? I'm hoping that Dukk still frequents here as he'll likely know. Any info is appreciated. |
I got a few questions answered with some more googling. I now know that I need to split up the optimum size. This would mean the .67 to .33 volumes. I also found the following post by Dukk
And that's where I think you f'd up. The basic vented box design is to include TWO vents and then you cut THREE. If one does the design tuning with a single vent it will be tuned much too high (vents too short). I'm thinking that it is supposed to be with two of the optimum ports. |
OK,
I'm already getting sick of this and I really need a drink. I'm beginning to think that with the REAL box size I'm going for along with the ammount of port area I want, not to mention the dimension limitations that I have to work with that this might be impossible. |
4 Attachment(s)
Alright,
my 3:45 in the morning first drafts. The large section will work out to 10.33 cubic feet after port, sub and a soon to be sized up gargantuan brace. This brace will be approx 12x27 rectangle. This side "I believe" will be tuned to 30.13 hz. I figure there's going to be some ****in up with the ports being that the're all different pathways but we'll see. In theory there should be a peak at 60.26 hz as well. Second chamber is 5.165 cubic feet after port displacements. Port is smaller than what I aimed for at 156 square inches with 80.75 inches of length. Overall dimensions are 84" long, 48" wide, 21" tall. Sub and ports all face forward. Anyone with experience with these boxes please chime in. Kirby. Attachment 19377 Attachment 19378 Attachment 19379 Attachment 19380 |
I think you are going to have way too much port turbulance with this design and its not going to sound right. I have found that with abc boxes you are better of using round ports. they sound amazing but you have to be very precise with the port lengths. You would probably have a better sound if you used smaller round ports that are straight than these rectangle vents with so many angles. Obviously larger vents are desirable, but the length becomes unusable. So a comprimise is necessary. Port noise is not that noticeable in these types of boxes because of the amazing response and punchiness of the second tuning. I would advise trying to design the box in a way that you can use straight round or rectangle vents even if the vents have to suffer a reduced area that might induce a bit of port noise. These boxes are amazing, but everything has to be exact.
|
lol, looks like I shoulda hit the site last nite ;) Weekends in the summer are busy for me.
You figure the maximum vented volume for the woofer. You take this volume and divide it 2/3, 1/3. You then model the enclosure to have TWO vents. You need to have enough port area for EACH vent though and that is where things get tricky if you have a smallish enclosure and a large displacment woofer. If using rectangular vents you would make each vent half the area you used to model the tuning. What you have sketched up there is more like some kind of hybrid transmission line box. If you're game, give it a go - it might work out! :thumbsup: |
So looking at the design that I've done it will not work as I took the ideal, and made the second chamber half of what that was.
I'm still not 100% on the ports though. I design it as a normal ported enclosure with two ports. Are both of these ports to be the optimum port size? Example, my current box is 10 cubes with 200 square inches of port. would I then design it with two ports at 200 square inches each? then cut that in half for the ABC box. so each port is 100 square inches? If you're cool with it Dukk, I'd like to possibly see an example, or even get you to do a design for me if possible. I will have no problem paying for this to be done either. |
I did find another example as well.
The goal with this box project was to construct an ABC box for two 6.5" TangBand W6-1139SC Subwoofers. The first thing to do was plug the T/S parameters into WinISD and seek for a max flat alignment via a ported box. After some time playing around with the numbers, I decided on 1.2 ft^3 tuned at 37hz with (2) 7 in^2 of port area, 20.69" long each. Next thing to do was divide the volume into two chambers: one big chamber, 66.7% of the total volume which comes out at (0.8 ft^3) and one small, 33.3% of the total volume (0.4 ft^3). These two chambers should each have their own (7 in^2, 20.69" long) port venting to the outside, and at the same time one more identical port connecting the two chamber inside the enclosure. The three situations where simulated in WinISD... the big and small chambers came out tuned to 32.0hz and 45.3hz respectively. These tuning frequencies were kind of pre-meditated since I already knew my amp has a "bass boost" centered at 45hz, and so I wanted the upper tuning frequency to be close to that point in case it was used. Since this is one of the enclosure's tuning frequency, engaging it shouldn't violently increase speaker's excursion as it usually does. We'll see... With this design the port is a total of 14 square inches to 1.2 cubic feet. This brings me to the conclusion that the two ports get divided |
| All times are GMT -5. The time now is 07:35 AM. |
© 2024 MH Sub I, LLC dba Internet Brands