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Thread: JbL 8 cubic feet enclosures

  1. #1
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    JbL 8 cubic feet enclosures

    Does anyone tried to build one of these enclosures in the past or does anyone use them to share his experience?Name:  SmartSelect_20210106-163050_Gallery.jpg
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  2. #2
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    Built lots of them ... in the late 70s - early 80s Whats your question?

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    Quote Originally Posted by Riley Casey View Post
    Built lots of them ... in the late 70s - early 80s Whats your question?
    How does they sound? With the correct drivers of course! Any photos?? Did you veneer them ?

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    They sounded great with dual 2220s and others with K140s. I painted them grey and trucked them around the countryside using them for concerts. Probably not much help in answering your questions but these were JBLs stock answer for years in low frequency cabinets for small spaces. I'd expect they are a much better solution for low frequency enclosures for small room listening than 4560s.

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    Hi Soulman,

    The plans that you show are pretty old, i'd say around 1975, based on the drivers mentioned. The latest such plans JBL published as far as i know was in 1979, with some more recent drivers (still old ones though). I have a paper copy of those with four different 8 cu.ft. enclosures with driver(s) mentioned on each (as in yours).

    I would have to take pictures of these plans for you. I'll be back later tonight, no time now, with a picture for each. That should help and give you a little more enclosure flexibility. Regards,

    Richard

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    Quote Originally Posted by RMC View Post
    Hi Soulman,

    The plans that you show are pretty old, i'd say around 1975, based on the drivers mentioned. The latest such plans JBL published as far as i know was in 1979, with some more recent drivers (still old ones though). I have a paper copy of those with four different 8 cu.ft. enclosures with driver(s) mentioned on each (as in yours).

    I would have to take pictures of these plans for you. I'll be back later tonight, no time now, with a picture for each. That should help and give you a little more enclosure flexibility. Regards,

    Richard
    That would help! Thank u!

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    Hi Soulman,

    As promised attached you'll find four other 8 cu.ft. cab drawings from JBL (1979).

    I noted a typo on two of those plans.

    First, on drawing for K 151 height is shown as 34", but the description at the bottom mentions 36". I don't know which is right or wrong, but at 34"H it would give 7.55 cu.ft. and at 36" it gives 8 cu.ft., and its called an 8 cu.ft. box...

    Second, on drawing for K145/3-way system a cutout for 2405 is shown, but in the description at the bottom the tweeter options indicated are 2402 & 2407. I assume 2407 might be a typo, should be 2405?

    The 2220A is not mentioned for the 8 cu.ft. double woofer box. I assume because at the time its Xmax was limited to 2 mm, but later increased to 3 mm with the H version.

    The two proper box size influencers: Qts and Vas. Well Vas is the same for 2220, 2205 and K140. And 2220 Qts is relatively close to those of K140 and 2205 mentioned in the double woofer drawing. I think you previously shown having some K140. Anyway, the 2220 may be an acceptable option (described by Riley), even though its Qts is a little lower (primarily designed for high efficiency horn loading instead of strong vented bass cab. It can still work). Regards,

    Richard

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    Quote Originally Posted by RMC View Post
    Hi Soulman,

    As promised attached you'll find four other 8 cu.ft. cab drawings from JBL (1979).

    I noted a typo on two of those plans.

    First, on drawing for K 151 height is shown as 34", but the description at the bottom mentions 36". I don't know which is right or wrong, but at 34"H it would give 7.55 cu.ft. and at 36" it gives 8 cu.ft., and its called an 8 cu.ft. box...

    Second, on drawing for K145/3-way system a cutout for 2405 is shown, but in the description at the bottom the tweeter options indicated are 2402 & 2407. I assume 2407 might be a typo, should be 2405?

    The 2220A is not mentioned for the 8 cu.ft. double woofer box. I assume because at the time its Xmax was limited to 2 mm, but later increased to 3 mm with the H version.

    The two proper box size influencers: Qts and Vas. Well Vas is the same for 2220, 2205 and K140. And 2220 Qts is relatively close to those of K140 and 2205 mentioned in the double woofer drawing. I think you previously shown having some K140. Anyway, the 2220 may be an acceptable option (described by Riley), even though its Qts is a little lower (primarily designed for high efficiency horn loading instead of strong vented bass cab. It can still work). Regards,

    Richard

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    Thank you for the plans! I think i would prefer the one 15" woofer models cause i need to have some spares in case of failure!

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    36" is the correct dimension. I know because a pair of the cabinets stacked put the horn on top at eye level with me. We used the 2220s because they matched the 2220s we used in the 4560s at the time not because JBL recommended them for those enclosures. We almost always used the boxes with 2220s as the mid bass in a three way system with 18s below and 2441s above. My recommendations are always based on using JBL speakers to entertain hundreds or thousands of people at inordinately loud volumes. Use a grain of salt when making choices for living room listening. I chimed in on the thread solely because the OP was already listening to 4560s at home and I knew there are better solutions for getting that 1970s sound. The lighter weight, curved coned 2220 make for a much better sounding mid bass driver crossing directly into a compression driver in my experience IF someone is bound and determined to use a 15 rather than a smaller cone driver. It certainly doesn't have the bass extension to work down to the low end of a full range playback system. In my living room I use a 12" cone between the 15 and the compression driver. I just don't think metal diaphragm compression drivers sound good when used below 1000 hz. Thats my superstition. To each his or her own.

    Quote Originally Posted by RMC View Post
    Hi Soulman,
    ...
    First, on drawing for K 151 height is shown as 34", but the description at the bottom mentions 36". I don't know which is right or wrong, but at 34"H it would give 7.55 cu.ft. and at 36" it gives 8 cu.ft., and its called an 8 cu.ft. box...

    ...

    The 2220A is not mentioned for the 8 cu.ft. double woofer box. I assume because at the time its Xmax was limited to 2 mm, but later increased to 3 mm with the H version.

    The two proper box size influencers: Qts and Vas. Well Vas is the same for 2220, 2205 and K140. And 2220 Qts is relatively close to those of K140 and 2205 mentioned in the double woofer drawing. I think you previously shown having some K140. Anyway, the 2220 may be an acceptable option (described by Riley), even though its Qts is a little lower (primarily designed for high efficiency horn loading instead of strong vented bass cab. It can still work). Regards,

    Richard

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  10. #10
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    Hi soulman,

    RE "I think i would prefer the one 15" woofer models cause i need to have some spares in case of failure!"

    Except for K145 & K151 plans, i think an 8 cu.ft. box is too large for the kind of drivers we are talking about here since their Qts is too low for them to fill the shoes correctly. This would lead to a pretty droopy LF response.

    A one 15" box makes sense as long as its not too large. For e.g. i have a similar plan, not shown, for one 2205 in 5 cu.ft. box. This is somewhat too large cab for the driver, i don't support it. Better to take the double woofer 8 cu.ft. box plan and divide it by two, leading to a 4 cu.ft. box, that's more appropriate size wise for a 2205, K140 or 2220 (the latter being pretty stretched already). You won't get very deep bass, say about 45hz, but this ain't a cab problem, its rather a low Qts driver issue, not really intended for very deep bass at higher volume.

    One can certainly try whatever he wants, being his gear and money. Any driver/box combo will produce sound, the main question is how appropriate will it be. Some combinations are definitely better than others.

    As an example, looking at JBL's Enclosure Guide suggesting various box size/tuning for drivers is interesting (not exhaustive). For the 2220: 1.5 cu.ft. tuned to 80hz for midrange or guitar; 3 cu.ft. tuned to 40 hz for full-range or MI bass. No larger boxes mentioned for deeper bass. No wonder, its very low Qts means in the bass range it would run out of steam pretty fast. Doesn't mean its a bad driver, but simply not designed for that purpose.

    For 2205, E140, etc., the Enclosure Guide suggests 4 cu.ft. box tuned to 40 hz, personnaly i prefer tuning at 45-50 hz, for flatter bass and less downtuning which requires more effort from the woofer.

    I've modeled in Winspeakerz two scenarios for 2220 in a vented box, as well as a scenario with three options with 2205/K140. That software doesn't have in its data base the K140, but instead has the E140 on which driver Qts was further reduced compared to K140. Since the latter has the exact same Fs, Qts and Vas parameter values as the 2205H (the three basic parameters required to model a speaker's LF response), then LF curves shown for 2205 are the same as for K140. All simulations done with standard QL 7 and half-space loading (one boundary, like cab on the floor).

    1rst pic, 2220, 3 cu.ft. box tuned to 40hz (as suggested by JBL). As can be seen this is quite a LF drop (-9 db or so @ 50hz). Not much bass in there compared to mid level. Would definitely need a 2nd boundary (floor + wall) or even a 3rd one (corner placement) to get some bass out of it, meaning at a comparable level with the mid.

    2nd pic, 2220, 1.5 cu.ft. box tuned to 80 hz (also suggested by JBL). Much flatter LF response but can almost forget bass below 80-90 hz. With that box the shoe fits way better though. Also confirms driver limited LF capabilities (low bass use), plus woofer more appropriate for horn loading.

    3rd pic, 2205H/K140, 4 cu.ft. box initially tuned to 40 hz (as suggested by JBL for both drivers). The box volume remains constant at 4 cu.ft. but have varied box tuning (Fb): lower curve 40hz, middle curve 45hz and top curve 50hz. All three curves are better here than for 2220 LF wise. Personnaly i prefer the top one, closer to being flat. Moreover, it has a gentle dip centered around 90 hz, making mid bass sound little less evident, which suits me fine, as i don't like mid bassy sound... Note the use of the E140 would be a little worst bass wise due to its even lower Qts. Regards,

    Richard

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