Anyone willing to design a box?

[Doug McCambridge 4]

Received my 2 fi BL 12s yesterday, I'm very satisfied with em but I believe they will get a lot louder in a different box design, I currently have a 34w x 15h x 20d "maximum size box that'll fit" with a slotted port on each side of the subs, I'm unsure on length of port its been 3 months since I built it, believe im tuned around 34hz, I'm running 2 1500's strapped "1ohm per amp" n 2 yellow tops, anyone willing to design a box that's no bigger then the dimensions above as far as tuning I'm thinkin 32hz I listen to rap music n demo with decafs any help is highly appreciated

[altoncustomtech 773]

You're running right down at the low end of Fi's recommended space for those subs with those dimensions.  I'm calculating you can get a hair over 3cuft NET volume with a 3.5" wide port tuned to 32hz.

 

The problem is that's NO WHERE near enough port are for those subs and not have major issues with port noise.  Without more space to work with you're going to have an issue.  I recently helped a guy with a design for a pair of XCON twelves that the final dimensions ended up being 14.75" H x 38" W x 32" D with 5.25cuft NET volume and ~100sqin of port area (7.5" W x 13.25" H) and it still slides into his trunk.  While it still wasn't completely optimal but it is far closer than the limitations you're trying to stay within.

 

Out of idle curiosity, what is limiting the enlcosure to those dimensions?  Do you think that maybe a little creativity could possibly yield a little more space to work with?

[Doug McCambridge 4]

Trunk space is pretty tight I can't go any higher 15 is max, width 36 is max, my max depth "could be" 32 would prefer no deeper then 25 due to limited space of amp location but if I need to move them its not that big of a deal id prefer to have the subs at best performance

Edited width just measured everything to its max

Edited April 23, 2013 by douglas12107

[altoncustomtech 773]

Going to 25" on the depth helps, but it's still not near perfect and even at 32" doesn't quite get to what I'd consider using myself.

 

However, I know I'm not using near optimal port area for my Q's and don't suffer any ill effects that cause issues for our listening habits.  Output may suffer, there is probably port compression present, and I'm sure it makes audible noise when the subs are pushed hard, but it's not easily noticed.  However the pair are rarely pushed to the limit as the output is more than enough for our regular listening habits.  When we do decide to push them hard the ensuing results border on the impossible to detect any issues with response as trim panels, body panels, and everything else that can move becomes a cacophony of noise accompanying bass too loud to listen to properly in the first place.  If anyone has ears sensitive enough to hear the negative effects of what the smaller than optimal port does to the response of those subs, it wouldn't be that sensitive for long.   

 

 

My point is, I made the decision to live with the results of having my enclosure designed the way it is and as yet I'm not unhappy with the results and I don't think you'd have any real issues with what can be designed inside those dimensions (including the 25" depth) that would negatively impact your listening pleasure from the subs.  If a person can give up all the necessary space for a perfectly optimal enclosure, then by all means do so, otherwise this hobby is all about compromise and more times than not the compromise is easily lived with for most people.

[Doug McCambridge 4]

1 Fi BL 12 for optimal performance is 2.4cu.ft at 32hz according to the posts for box recomendations with my measurements I have net volume 7.9cubes without port how wouldn't that be a big enough box? Wouldnt 4.8cubes tunes at 32hz be optimal? I'm no box expert, how big of a difference does the port area/port area per foot make? What's recommended? I know the bl's call for 2-16 square inches of vent area per cubic foot of volume, can't I achieve that with my measurements and still have enough NET volume?

[AXEHAMMER 16]

Not sure on the exact design part douglas, but you are in good hands with Alton HE KNOWS HIS SHIT. He will take care of you, just work with him and communicate. I couldn't be any happier with the box he designed for me for my 15 xcons.

[altoncustomtech 773]

7.9cuft?  How are you calculating this?  Even using the absolute MAX dimensions of 15 x 34 x 32 (13.5 x 32.5 x 30.5 internal dimensions assuming 3/4" MDF) I only get 7.74cuft and that's GROSS not NET.  I think you're not subtracting the thickness of the wood correctly or getting something off on the calculation in the first place.  GROSS volume includes subwoofer displacement (.36cuft in the case of the 12" BL's) and the displacement of the port itself.  The wood used to create the walls of the port also has to be calculated.

 

 

15 x 34 x 20 (13.5 x 32.5 x 18.5) only yields 4.69cuft GROSS to work with, 15 x 34 x 25 (13.5 x 32.5 x 23.5) only gets 5.96cuft.

[Doug McCambridge 4]

That's good to know, n I'm workin with him the best I can if only my trunk was bigger :/

Edit: using Torres calculator that's what its talkin me for net volume

Edited April 23, 2013 by douglas12107

[altoncustomtech 773]

The problem comes in with the port.  If you take a port that is 3.5" wide like I mentioned earlier it takes up ~1.22cuft of volume inside the enclosure.  To tune to 32hz it needs to be about 36.5" long, 3.5 x 13.5 x 36.5 comes to 1724.625cuin or just under 1cuft.  Then add the thickness of the wood at .75 x 13.5 x 36.5 which comes to 369.5625cuin or .21cuft which totals 1.21cuft taken up by the port itself.  So if you're working with your original dimensions of 15 x 34 x 20 the max volume you have to work with from the beginning is 4.69cuft, subtract the 1.22cuft and get 3.47 cuft left, then subtract the sub displacement of .36 and you get 3.11cuft NET volume.  

 

 

That's a quite basic rundown of how that's calculated and subject to change in accordance with the actual physical port length, bracing, baffles, flush mounting, etc.  

[altoncustomtech 773]

That's good to know, n I'm workin with him the best I can if only my trunk was bigger :/

Edit: using Torres calculator that's what its talkin me for net volume

 

I'm sorry but there's GOT to be a number getting put into that calculator wrong.  It's usually very close to correct.

[Doug McCambridge 4]

Alright, makes a little more sence, with that all said are you willing to sketch me out a box 15h x 36w x 32d tuned at 32hz if I had the trunk space I would go bigger but kinda impossible without a different veichle

[altoncustomtech 773]

Sure.  Are you certain you can slide in a box at those dimensions?  If you've not already tested it I would suggest doing so with a cardboard mach up box to test the fit first.  I'll go ahead and start on a design and drawing tho, no problem.

[Doug McCambridge 4]

I guarantee it'll fit but knock 1in of the depth so 15h x 36w x 31d

[J2phat4u 9]

Alton I am not thread stealing but was wondering what would you recommend for 4 FI BL fully loaded 12's as far as cubes, tuning? I have an SUV so I have space to work with.

[Doug McCambridge 4]

anyone willing to review this box sketchup? to big? to small? To much port area? for what im running, 2 1500rms strapped 2 D2 BL 12's 2 yellow tops HO alt. rap/decaf music lookin for at least 140db, pretty sure im over that right now but wont know for sure till metered next weekend previous box is tuned to high looking for better output/better lows as far as bracing i think im gonna use 2 ready rods 1 in each side dead center or just 1 all the way but will that mess with my port? im thinkin a 3/4in rod

 

[altoncustomtech 773]

Things have been a bit too hectic for me to get after helping with the design, and it looks to me like you don't need much help at all.  It looks really damn good from my initial looks at the numbers.  The only slight difference may come to the tuning, it could end up a tad higher than what you have it tuned to.  The reason for that is because for a center splitting port like that to tune properly half the port width (the 3.25") to the port length on each side/in each chamber, or at least from all the reading I've done and experience I've had with this style enclosure.  No matter what I don't think it's going to make near a big enough difference to worry about it.  I say build it and enjoy!

[Doug McCambridge 4]

Alright thanks, Alton I've also read about the whole port being half as in my design if its a little higher its fine I'm slightly under 32hz anyways