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Thread: What to do with 2241H's

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  1. #1
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    What to do with 2241H's

    So one evening after a nice margarita and in a moment of idle boredom, I bought a pair of used JBL 2241H's off the interwebz. It was so impulsive, I was thinking 2245's and didn't notice the single digit was off. My thought was to build some house shaking 2-ways with large horn up top. Upon unboxing them in my living room, not only did I realize I goofed on the model, but also just how HOOGE 18" woofers are. I have 240Ti's as my main speakers, and often have 2-3 pair arrayed for comparing, but these 18's absolutely dwarf the LE14's.

    What really killed the project is that JBL recommends a 10 CF enclosure for these, and I know I've been lucky so far but the wife will never approve that size cabinet as a permanent fixture in the living room. So they've been hibernating in the basement for 2 years.

    My question is: can I stuff these into smaller enclosures as a compromise? I know it would not be optimum, but using the woofers would seem to be better than not using them. At 98 dB efficiency, they would seem to be a perfect mate to a CD and horn, and would move a heck load of air.

    Thanks for any suggestions and input
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  2. #2
    Dang. Amateur speakerdave's Avatar
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    I think the short answer is probably not, when I recall that the 2245, designed for what you want to do, needs 8 cu ft with BX63a for equalization to get there.

    The one slim slim chance might be to employ Rod Elliot's extended base active equalization or Linkwitz's updated idea of a mirror compensation circuit for in-room response, given the measurement and technical capacity. The extended base idea is to house a woofer with unsubwooferlike higher native resonance, good power handling and excursability in a very small sealed enclosure so that operation is entirely below system resonance, and increase drive by 12dB per octave going down.

    I know that 4313b has experimented with this idea using a 2242, a similar driver but more capable in key ways, and leaving out the compensation circuit to see what might happen with just room gain.

    Limitations and risks of this idea: 1) It takes a very small box to raise the resonance to the top of the normal subwoofer range, so that true usefulness may be below 50 or even 40 Hz. 2) IMO the cones in most large woofers would not be built to behave pistonically under the pressures created in this kind of environment with severe drive, so output before garbage may be unexpectedly limited. Number two would be even more of a risk using a woofer cone that has led a wild life in SR.

    If I had, like, you, waked up in the company of woofers with the wrong name, sending them on down the road would look easier and more likely to succeed than trying to make them change their names.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  3. #3
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    The 2241 will do fine in a 9ft3 enclosure (look at the JBL 4641 subwoofer system).

    http://www.jblpro.com/www/products/c...1#.XBk_LVVKiHs

  4. #4
    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by sguttag View Post
    The 2241 will do fine in a 9ft3 enclosure (look at the JBL 4641 subwoofer system).

    http://www.jblpro.com/www/products/c...1#.XBk_LVVKiHs

    I understood him to to mean he needed to go small.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  5. #5
    Senior Member RMC's Avatar
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    Hi Sablotny,

    RE: "What really killed the project is that JBL recommends a 10 CF enclosure for these..."

    Well there's hope for you and convincing your wife. Happy wife, happy life! I seem to have learned that over 30 something years...

    The 10 cu.ft. box shown with Fb 30 hz in the data sheets (12/95 and 04/08) is an example given for low frequency extention with an F3 in the 30s.

    However, in both versions of the data sheet, the recommended box volume for this driver is given at 5-12 cu.ft. Therefore no need to keep them hibernating in the basement any longer. You can still make something worthwhile with them, even if not necessarily optimal LF wise... Naturally you'll need to sacrifice some deeper bass but you already know that.

    RE: "At 98 dB efficiency..." Btw that sensitivity number was measured at 100-500 hz, not 50-500 hz like some other LF drivers from JBL. A tiny red flag re VLF output.

    Just checked in Winspeakerz speaker design software to see if the 2241H is already in the data base (quicker), and it is so I'll be back shortly with a few quick modelings/suggestions for you. Gotta go now wife says lunch ready... Regards,

    Richard

    EDIT: I understood the same as Speakerdave, i.e. to go smaller...

  6. #6
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    I think these are about 6 cu ft.


  7. #7
    Senior Member RMC's Avatar
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    Hi Sablotny,

    A few notes to start with.

    As promised I did four modelings in Winspeakerz using the 2241H in 5, 6, 7 and 8 cu.ft. targeting relatively flat response (< 1 db ripple) also trying to avoid long vents like 14.6 & 18.8" I got in some modelings if I took a larger area port which may complicate the builder's work when too long. The vent diameters given here still meet and exceed JBL's min. rule of one-third the driver's diameter (one-third of 18" being 6" and my two 5" vents are equal in area to a single 7" vent). I also gave 2 X 6" vents info when length was more acceptable (< 12").

    I avoided tuning each box (Fb) below driver's free air resonance (Fs 35 hz), as a precaution only. Tuning at 35 hz for all boxes also minimized the amount of ripple in response. The software showed with all the boxes here none of them exceeded 7mm of cone travel at 600W!, the rated Xmax for this driver being 7.62 mm.

    Remember that all box volumes given are NET, therefore you'll need to account for (add) space taken by driver (JBL: 18" = 0.3 cu.ft.), good bracing and vents. This increases the gross cabinet size that your wife will eventually see in the living room...

    * 5 cu.ft., Fb 35 hz, F3 48 hz, ripple + 0.7 db @ 100 hz, Sv min. 41 sq. in., 2 X 5" vents (39.3 sq. in.), Lv 12.2"

    * 6 cu.ft., Fb 35 hz, F3 46 hz, ripple + 0.4 db @ 90 hz, Sv min. 41 sq. in., 2 X 5" vents (39.3 sq. in.), Lv 9.3"

    * 7 cu.ft., Fb 35 hz, F3 43 hz, ripple + 0.25 db @ 95 hz, Sv min. 41 sq. in., 2 X 5" vents (39.3 sq. in.), Lv 7.2" or as another vent option 2 X 6" (56.5 sq. in.), Lv 11.7"

    * 8 cu.ft, Fb 35 hz, F3 39 hz, ripple + 0.15 db @ 90 hz, Sv min. 41 sq. in., 2 X 5" vents (39.3 sq. in.), Lv 5.7" or as another vent option 2 X 6" (56.5 sq. in.), Lv 9.4"

    Its up to you now to decide what you can "sell" and live with in terms of box size vs LF performance. Regards

    Richard

    Edit: Modelings done assuming 2 Pi placement and box loss factor QL 7 which may be a little too optimistic, depending on box size chosen.

  8. #8
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    If your intent is to build a 2-way, I think you are better off with the 2241 rather than the 2245. You will get better integration at the horn as well as better definition in the bass. You give up a bit of deep bass, but eq can take care of that.

    The 2241 even goes higher with better articulation than the 2235, let alone the 2245.

  9. #9
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    Wow - Thanks

    Thanks so much for all of the very informative replies. Playing around in AutoCAD, I think a 5-6 CF cabinet including vents & braces might just work. I will spend some time checking out Winspeaker as well.

  10. #10
    Senior Member RMC's Avatar
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    Hi Toddalin and Sablotny,

    RE Lee's fairy tale, the usual crap, no time to waste on that: he sure hasn't read nor understood post # 22.

    I think the purpose of this site is to share info and provide help whenever possible and within the means of everyone (provider and "client").

    Some folks here seem to be quite fast on the trigger, driver wise (i.e. kill it). If I can help Sablotny make an acceptable LF box, not necessarily ideal in view of constraints, I will though the "jury" may think otherwise. Trying first to "salvage or rescue" the drivers seems important, as he won't get reimbursed for these = money down the drain. Also important when its JBL drivers being discussed on a JBL stuff related site, and the member has requested suggestions to make things work. Dumping or scraping them he can do all by himself, he doesn't really need help for that.

    Right from the start Sablotny admitted having made a mistake when ordering the drivers, and that there are concerns from spouse about box size. Fine for me, that's part of real life and of the challenge of working with constraints, like taking whats there.

    I'm much more interested in trying to help him out of the ditch than making thumb up or down on the equipment. This is why I modeled a number of 2241H boxes for him so that he can assess the impact and help him make a choice.

    Seems to me this site has an elitist tendency in its approaches. Looks like "audio snobbery", and it reminds me of what another member wrote in another thread not long ago about members giving too much importance to perfection and their reference system than really helping the younger generation or newbies who come here for help and know mostly MP3 sound on ear buds. Can't remember his Avatar and exact words but its something along these lines here.

    2241H is basically a sound reinforcement driver (not really for sub), with all that comes with it, instead of a home hi-fi or a control room monitor driver (though tech sheet tries to salvage the latter aspect). These are different ball games. One emphasizes linearity and deeper bass, the other sensitivity and spl output at the expense of the former items.

    I take it as it is trying to provide something helpful to the member, like Toddalin, rather than focus on what he should own or puchased, which would mean dumping working drivers he spent money on, plus spending more on others that fellows here won't pay for. Then lets try to make these work.

    Sure doing it this way requires more time and effort. But I think that discarding the drivers doesn't really help him at all, it just means "you purchased the wrong thing" i.e. appears blaming vs helping him out.

    Going back to the following, plus his stated context, its my guidance: "My question is: can I stuff these into smaller enclosures as a compromise? I know it would not be optimum, but using the woofers would seem to be better than not using them." He knows its not best but still better than nothing.

    If the bass is deficient, then he can start with 2-3 boundary box placement to help increase VLF output, that is free bass boost, saving some EQ and associated amp power requirement.

    So I support Toddalin's approach, which is also mine here, to try to make something with the drivers instead of nothing. I see this as more useful, relevant and cost-effective in the circumstances. We agree on the end result for somewhat different reasons, but some are complementary. Regards,

    Richard

  11. #11
    Senior Member Ian Mackenzie's Avatar
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    Subject to building a real enclosure for subjective assessment the OP may like the D.B. Keele 6th order boosted alignment with the 2241 woofer.

    A bass reflex enclosure of 7cu ft 3 with 1 inch of fibre glass lining yields an f3 of 29 hertz (see curser window box readout) with the tuning of Fb = 26 and boost of 26 hertz (Q=2).

    At full power the output is 128 db AT 26 hertz and 124 db at 40 hertz.

    A large JBL 2384 wave guide and a suitable driver could be used down to a crossover frequency of 630 hertz. Theis wave guide is regarded as being particularly impressive from diy user reports.

    The 2241H has a maximum recommended crossover frequency of 800 hertz

    The boost for the woofer, horn and crossover for a bi amp system (for friendly diy ) can be applied with a DSP loudspeaker management system such as from DBX.
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  12. #12
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by toddalin View Post
    ...The 2241 even goes higher with better articulation than the 2235, let alone the 2245.
    This is going to seem rude and that is not the intent but,,, that’s a series of typo’s right?

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  13. #13
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    Quote Originally Posted by 1audiohack View Post
    This is going to seem rude and that is not the intent but,,, that’s a series of typo’s right?

    Barry.

    No, look at the specs and listen to the both of them side-by-side for hours on end.

  14. #14
    Senior Member Lee in Montreal's Avatar
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    For a sub, get a 2245 and cross it around 50Hz.

    2241 are worthless in my very humble opinion. No bass and too much mids.

  15. #15
    Senior Member RMC's Avatar
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    Hi toddalin,

    I'm fully supportive of your approach since you entered the thread, regardless of the curves in post # 21 and some other things, since it tries to make something acceptable with what the "customer" HAS, instead of what he DOESN'T. Sablotny is in a particular situation which requires more help than simply the dump/replace driver approach...

    I'll be back with more on my reasoning here and consequently why I support what you do. Keep the approach and position! There's two of us. Regards,

    Richard

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