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Thread: Recommended Enclosure for a 2240H as HT Sub?

  1. #16
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    Quote Originally Posted by toddalin View Post
    Just use WinISD and look at the optimum cabinet size and tuning for that woofer. I'm pretty sure thet 2240 is listed in their library. Then look at the largest cabinet that you are willing to accept, let the program select the optimum tuning, and compare that with the optimum size/tuning to see if it's an acceptable alternative. Everything is a compromise of one sort or another. WinISD is free to download. BTW, other than the 2245 for a bit deeper bass, WinISD says that the 2241 is the best alternative and that's what I use..., based on WinISD. The 2241 gives up little in the way of deep bass to the 2245, but has as much more "texture" and volume and can use/will produce better results a smaller cabinet than the 2245. It also gives up some power handling and volume to the 2242, but provides a deeper bass in a smaller cabinet.
    That's good info, thank you. I want to mate subs to a pair of Yorkville U15. I don't want to go bigger than 5'. Is there a Mac alternative?

  2. #17
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    WinISD says 2240H optimum box is 75.4 litres tuned to 53.3 Hz. You would use two ports .102m in diameter and 150.1 mm long. 2241H optimum box is 302.9 litres tuned to 35.31 Hz. You would use two ports .102m in diameter and 52.8 mm long. 2245H optimum box is 218.3 litres tuned to 30.16 Hz. You would use two ports .102m in diameter and 167.7 mm long.

  3. #18
    Senior Member RMC's Avatar
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    RE I want to mate subs to a pair of Yorkville U15. I don't want to go bigger than 5'. Is there a Mac alternative?

    I don't think Win ISD has Mac capability, neither Winspeakerz that i used here since 2240 is in the database.

    Its unlikely you will improve your VLF situation with the 2240 in a 5 cu.ft. box and being flat. That Yorkville cab has an F3 at 50 hz (see pic attached) and the reasonably flat response i could get from modeling 2240 (see other pic) gave about the same F3 as the Yorkville U15 and similar to Todd's F3.

    One may always downtune the box with consequences attached, or use a boost/cut filter or simply EQ.

    However the vent sizes i got from the software are different than Todd's results. I'll post my vents data tomorrow night, as well as other comments, since i have to go now.

    Richard
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    Thanks so much, guys. Doesn't look like a smaller cab would change things with that 15" in the U15. But is there a way to cheat a little bit by coupling the 18" to the floor? I mean facing the driver down and tuning the distance/gap to the floor? Or a secondary baffle in front of the driver but still at the floor as I would not want to excite the floor. btw, I don't have 2240s on hand but do have 2245s and 2269s.

  5. #20
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    You can "cheat" using eq. But you would want a steep cut-off at the bottom end to keep from continually bottoming out the cone due to over-excursion.

  6. #21
    Senior Member maxwedge's Avatar
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    2240 vs 2245

    Bassbox 6 Pro simulated 2245 vs 2240 in 9 cf box and ports optimized for drivers. The 2245 data is measured from my own drivers w/original cones and the 2240 from the data base. Orange is the 2245 and is clearly superior in the low end. I also have 2242s but to me the 2245s sound a lot better in my stereo/HT. IMO, I wouldn't waste time with the 2240s unless you already have them or aren't going to spend much $ on them.

  7. #22
    Senior Member maxwedge's Avatar
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    That's probably not what you wanted to know, or already know it, but I also modeled the 2240 in a smaller box and it was worse.

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    That is a beautiful curve on the 2245. I just can't live with an 8' cab..or two. Anyway, I think I've hijacked Cerondipity's thread long enough.

  9. #24
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    I agree with Todd's low-cut filter suggestion. I tend to forget about these, my gear is often older analog having built-in high-pass of one form or another, that i don't really worry about it. As for the "optimum box" i can't recall ever using one suggested. Optimum as per softwares often means max. flat, i.e. most number of observations (dots) on a straight line, but the rest of the curve might not look good at all when seeing the global picture. Not the go to for me, because usually not the best outcome in my view or for my needs.

    Low Qts woofers (2240: 0.23 is low) aren't naturals in digging deep. They have other assets but not deep bass capability. They're optimized for high piston band sensitivity at the expense of deep bass according to Eargle. While real subwoofer drivers are optimized for VLF at the expense of efficiency... The 3-4 db difference involved here matters.

    As posted before i modeled the 2240H in a 5 cu.ft. box (Gasfan's wish of no larger than 5 cf), and then played with the box tuning to see what i could get out of this with a reasonably flat response. Best scenario in my view was Fb 50 hz, since lower tunings gave a droopy LF response... I tend to consider +/- 1 db as flat. On my graph the bottom red line is Xmax (1 W here) and the upper red one is Xmec (mechanical limit before damage).

    Most speaker softwares already factor in 2 Pi cabinet placement in their woofer modelings, e.g. box directly on the floor (not on a base, a stand or a dolley).

    There's an easy way to salvage the 2240H's lack of VLF output even in reasonable size cabs. Its to use floor and back wall (two boundaries) or corner placement (three boundaries) which increases VLF output. This is FREE additional LF "horsepower" courtesy of room gain. In such case one may have to equalize downwards with a tone control or an EQ, and the nice part is this might free some amplifier power on the low end, therefore minimizing risk of amp clipping or driver distortion.

    In terms of vent size, JBL's older guidance was to use a port of at least 1/3 the size of the woofer, so 6" tube for 18" woofer (or multiple with equivalent area). More recent JBL standards are even more demanding in view of ever increasing driver input powers.

    The initial vent size suggested by Winspeakerz was 2 X 6" (3X5" about the same), that's two big holes in a cab! May seem like crazy but Physicist and Engineer John Murphy who designed the software is closer to modern vent requirements than some others. That's based on driver power and vent air velocity to prevent port choking at high drive. Since the 2240 is an older 300W woofer its unlikely to see 1-2 KW powers. This opens the door to a vent compromise.

    As shown on data below my graph the software minimum recommended vent area is 44.6 sq. in for the driver/cab i modeled. Pics: 2X4" (equivalent to 1X5.66") is tight, 3X4" somewhat better, 2X5" getting a bit closer to target, 3X5" exceed the min. requirement. If i was in those shoes, and considering the circumstances here i'd probably want to go at the very least for 1X6" tube (older JBL rule), or preferably the 2X5" (equivalent to 1X7") in case i beat on it a little...

    Richard
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  11. #26
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    Quote Originally Posted by gasfan View Post
    That is a beautiful curve on the 2245. I just can't live with an 8' cab..or two. Anyway, I think I've hijacked Cerondipity's thread long enough.
    Sorry to continue with the hijacking...

    It is a beautiful curve and it sounds great too! They are not super powerful beasts like the 2242. In domestic use they are fantastic if you can accommodate the space. Unfortunately that is not always possible.


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