Recommended Enclosure for a 2240H as HT Sub?

[cerondipity]

Went ahead and picked up a 2240 to get started- not too expensive and I know it can be later re-coned to a 2245 should I require something that goes lower. I like the Idea that the 2240 may be punchier and more dynamic- and do not see the need to go below 30hz and there is room loading to consider and we have a lot of glass windows/doors here...

Room size is roughly 22' x 16'. Main viewing/listening couch will be about center- 11'-12' from the screen.

Sub could go in front or behind of couch- probably a rear placement would have more room/out of the way.

I understand a ported 8 cu.ft. enclosure with a 6" port diameter is a good place to start.

Was also wondering if it makes sense to have the port down facing to load the floor? Would this room size really require two subs?

Any thoughts would be most welcome.

[more10]

Frequency range of the sub? Maximum size of the cabinet?

[Lee in Montreal]

You can build a 10cft out of a sheet of 4'x8' and add reinforcement with extra wood. That's roughly 24"x24"'x36"

I suggest you do your own test using a simulator. Move the Fs around until you get the curve you like.

You can tune the cabinet to 30Hz for low bass, or 34-40Hz for more audible bass ;-)

If your cabinet is 12" off the floor, sure you can postion the port downward, but honestly, there's no point. ;-)

Lee

[cerondipity]

You can build a 10cft out of a sheet of 4'x8' and add reinforcement with extra wood. That's roughly 24"x24"'x36"

I suggest you do your own test using a simulator. Move the Fs around until you get the curve you like.

You can tune the cabinet to 30Hz for low bass, or 34-40Hz for more audible bass ;-)

If your cabinet is 12" off the floor, sure you can postion the port downward, but honestly, there's no point. ;-)

Lee

I am inclined to a tuning compromise like 35hz- but I will await measurements based on the new HT speakers/placement.
Thanks Lee!

[Lee in Montreal]

10cft - Fs35Hz - 2 x 6" ports - 6" long
10cft - Fs35Hz - 1 x 6" port - 1.8" long

10cft - Fs30Hz - 2 x 6" ports - 12.5" long
10cft - Fs30Hz - 1 x 6" port - 4" long

You can confirm with a different software.

If tuning to 35Hz, then cone gets unloaded under that frequency, but you get more content above 35Hz.
Or you can tune to 30Hz to keep cone control in check, and slightly boost 35Hz region w/ eq

Personally I would tune the cabinet to the driver's Fs (30Hz) and boost 35Hz if necessary.

Lee

[spkrman57]

10cft - Fs35Hz - 2 x 6" ports - 6" long
10cft - Fs35Hz - 1 x 6" port - 1.8" long

10cft - Fs30Hz - 2 x 6" ports - 12.5" long
10cft - Fs30Hz - 1 x 6" port - 4" long

You can confirm with a different software.

If tuning to 35Hz, then cone gets unloaded under that frequency, but you get more content above 35Hz.
Or you can tune to 30Hz to keep cone control in check, and slightly boost 35Hz region w/ eq

Personally I would tune the cabinet to the driver's Fs (30Hz) and boost 35Hz if necessary.

Lee

You won't lose much doing the lower tuning and the 2240 will be happier. Now if you had 2242s!!!!!!!

Ron

[gasfan]

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.

[toddalin]

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.

[RMC]

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

[Val]

I went with 12 cubic feet for my 2245H. I love it.

http://www.audioheritage.org/vbullet...Woofer-Project

[RMC]

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

[gasfan]

So my question is, are there tunable ports available to tune the room?

[Robh3606]

So my question is, are there tunable ports available to tune the room?

What???

You can always temporarily install ports of any length. I have done that when I wasn't sure which box tuning I was going to use. I typically use double flared. You just change the spacer length between the inner and outer flare.

You would not be tuning the room just altering the box for a "better fit".

Debatable how well it will work.

Rob

[gasfan]

What??? You would not be tuning the room just altering the box for a "better fit". Rob

Yea, that's what I'm referring to. Thanks.

[toddalin]

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.