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Thread: JBL Woofer Questions. Education badly needed.

  1. #1
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    JBL Woofer Questions. Education badly needed.

    Second thread started today. Sorry for the bother, but I may not have the luxury of a lot of time to accomplish some goals I have.

    I want to build some speakers with JBL parts. I have some ideas about what the end-'product' would look like, but would like to focus my education on woofers, for the present. My questions will reveal my great level of ignorance, which I voluntarily admit -- up front. So, here goes:

    1. I have seen the 4350s. They are beautiful -- and big. My speakers will need to be smaller. Maybe not a lot smaller, but nevertheless smaller. SO, for an optimum bass solution, my first question is this: Are 2 woofers better than one? Ok, more specifically: Will 2 12" woofers 'bring it' better than one 15"? Will two 15s outperform one 18" monster? The question is simple: Which will sound better? I suspect the answer is rather complex.

    2. Cabinet volumes: I can infer from the LH website data, the 'applied' cabinet volumes and porting for a number of different woofer models -as used through the years. Is this a good source for info?

    3. Possible incredibly stupid question: If two woofers are used in a cabinet, with proven JBL cabinet volumes and porting, should the chambers for each woofer be totally separate and isolated? Or ... is it advisable to acoustically connect the two chambers with ports, etc.?

    I know all of this includes questions about 'which specific woofers' and crossovers, and a lot of other considerations, but I have to start somewhere. The cabinet size is a very real constraint, so I feel the woofers are a good place to start.

    Thank you,

    Greg

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    Senior Member ivica's Avatar
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    Quote Originally Posted by cgregory4 View Post
    ......

    1. I have seen the 4350s. They are beautiful -- and big. My speakers will need to be smaller. Maybe not a lot smaller, but nevertheless smaller. SO, for an optimum bass solution, my first question is this: Are 2 woofers better than one? Ok, more specifically: Will 2 12" woofers 'bring it' better than one 15"? Will two 15s outperform one 18" monster? The question is simple: Which will sound better? I suspect the answer is rather complex.

    2. Cabinet volumes: I can infer from the LH website data, the 'applied' cabinet volumes and porting for a number of different woofer models -as used through the years. Is this a good source for info?

    3. Possible incredibly stupid question: If two woofers are used in a cabinet, with proven JBL cabinet volumes and porting, should the chambers for each woofer be totally separate and isolated? Or ... is it advisable to acoustically connect the two chambers with ports, etc.?

    .....

    Greg
    Hi Greg,

    1. 18-ich if possible (my opinion)
    2. 300 Lit (10-12 cbf) if possible
    3. if different tuning prefer, then two boxes (isolated chambers), but as known 4350/55 use single chamber.

    regards
    ivica

  3. #3
    Senior Member Mostlydiy's Avatar
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    Hi Greg,

    I would say that it mostly depends on your room and your music preferences. Small room, small speaker, big room, big speaker. Bass heavy music bigger woofer etc.

    I think you could go a long way with a good two way speaker. A good horn/driver and a good 12"/15" woofer and you are all set. The big JBL 4 way systems are intriguing but constructing them yourself is a pain. The currently best JBL speakers are two way(ok, they are 3 way but the UHF arent really needed if you ask me), Everest, M2, K2 etc

    /Mostly

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    Since this is partly related, what do you guys think about a system where you'd use a TAD 4002 together with four 2235h? The 4002 would do 600-1kHz and up, while the first pair of 2235h would do 300-1kHz and the last two 300 and down.

    If you had to pick a driver to work in a two way system with 4002, what other driver would you use (and why, with no regard to the room)?

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    Senior Member Mostlydiy's Avatar
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    Sorry for hijack but I think a single 1601 would do the trick. The tad 2402 are highly regarded. There are the Rey Audio speakers though with MTM configuration.

    /Mostly

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    Administrator Robh3606's Avatar
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    Well without knowing your cabinet size it is very difficult to even discuss the woofers. Different woofers work best in defined sizes and tuning. If you need good LF response in a compact design it's hard to go wrong with LE-14's. The -2 or -3 from the Arrays would be a very good choice if you can find a pair. Any of the other woofers with similar LF response are going to need significantly bigger cabinets. You can do quite nicely in under 4 cubic ft with them.

    Rob
    "I could be arguing in my spare time"

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    Great advice on the LE- --14s!

    Quote Originally Posted by Robh3606 View Post
    Well without knowing your cabinet size it is very difficult to even discuss the woofers. Different woofers work best in defined sizes and tuning. If you need good LF response in a compact design it's hard to go wrong with LE-14's. The -2 or -3 from the Arrays would be a very good choice if you can find a pair. Any of the other woofers with similar LF response are going to need significantly bigger cabinets. You can do quite nicely in under 4 cubic ft with them.

    Rob
    Rob,

    Thank you for the reply. You are absolutely addressing part of my questions, which seem to be sorta confusing as I reflect on them.

    Interesting. I squirreled away a nice set of LE-14s for possible use on a 'project'. However, let me ask you for some additional input. I want my woofers to dictate the smaller cabinets, so your comments on the enclosure requirements for the LE-14s are incredibly pertinent. Let's say I am willing to ante up for another set -- so two 14s in each enclosure. This would result in a significantly smaller cabinet, right? Not a 4355 ... but not bad -- and at half the weight? With the correct enclosure and the proper porting, I am assuming two LE-14s would sound as good as a much larger driver as well. Is this a reasonable expectation/approach?

    Since I have you 'on the phone' please let me ask about another possibility. I am not about to actually do this -- I don't think -- but maybe the illustration will reveal my questions, more clearly. I have 4 empty 4425 cabinets in my garage. I believe the 2214H sounds great in that system in that cabinet. So, what if I glued/screwed 2 together, with holes in the interior dividing walls -- installing two 2214Hs and a 'baby cheek'. I guess, with the correct crossover design, I would have a 'baby' 4435, with an even smaller cabinet than with the 14s. If I added a 2420 driver with horn and lens in the middle, left the 'baby cheek' on one side, and plugged in a 2405 on the other, what would I have? With the right crossover, might I have a nice sounding 4-way in a fairly small enclosure? Or ... an abomination? The woofers, mids, highs, and ultra-highs might all be different drivers than what I suggested in my silly example. However, would it be possible to achieve 85% of a 4355 sound in half the space/weight? That is my reasoning for approaching the project from a 'woofers up' perspective.

    Or ... am I just pissing into a stiff west Texas wind?

    Again ... thank you.

    Greg

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    Senior Member honkytonkwillie's Avatar
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    Regarding woofer size and enclosure volumes, "Bigger is better" is a very, very, rough characterization of things that are often considered "good to have". Each woofer model has it's own specific electrical and mechanical parameters that help in determining which enclosure will work "best" for a given performance goal.

    There's lots of loudspeaker design software available, much of it free, which can assist with enclosure design. One of my favorites is WinISD which contains a database of drivers, but you can add your own.

    Two woofers in the same cabinet are fine, so long as they are playing the same signal, in phase. However, dividing the cabinet into separate enclosures has the benefit of stiffening the cabinet by reducing the length of unsupported panels, thus reducing cabinet resonances.
    I control the treble.
    I control the bass.

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    Good points!

    Quote Originally Posted by honkytonkwillie View Post
    Regarding woofer size and enclosure volumes, "Bigger is better" is a very, very, rough characterization of things that are often considered "good to have". Each woofer model has it's own specific electrical and mechanical parameters that help in determining which enclosure will work "best" for a given performance goal.

    Two woofers in the same cabinet are fine, so long as they are playing the same signal, in phase. However, dividing the cabinet into separate enclosures has the benefit of stiffening the cabinet by reducing the length of unsupported panels, thus reducing cabinet resonances.
    Willie,

    Thank you for the helpful response. You mention 2 topics that were part of my original thread post.

    1. Please allow me to refer back to my 'silly' example of two 4425 cabinets attached side-by-side. Both woofers would 'see' a stiffened internal brace between the two drivers -- in fact, twice the thickness of that original internal surface. Since the internal bracing would be enhanced anyway, is there an advantage to porting between the two woofer chambers?

    2. By using a 'known', proven, effective volume for each woofer, a new enclosure does not need to be designed and built from the ground up -- although obviously highly modified. Going a step further into the absurd, what if the center double wall of the enclosure was milled to the shape of a driver plus horn? Done properly, maybe slightly above the centerline of the enclosure, I don't think much stiffness nor cabinet volume would be affected. What do you think?

    3. What remains is the specification of high and ultra-high transducers that have minimal impact on cabinet volume -- not a difficult task, do you think?

    Willie, I'm not suggesting the 4425 cabinet design is 'sacred'. An L96, L100, L200 (even a 4313b mini ), and others could be combined for more bass, different drivers, and some decent 3-way/4-way speakers. Throw in some older frequency divider networks and crossover considerations might be handled without too many obstacles. The 'bottom line' for me is that JBL engineers did the designs for different enclosures a long time ago, based primarily on the woofers specified. The hard work is done. I see woofers, mids, horns, etc., increasingly on eBay. What is happening to the cabinets? They are probably in dumpsters. What a shame -- the parts are worth more than the whole.

    I am trying in this thread to learn more about dual woofer considerations. This might open up more possibilities for JBL projects.

    This is not a new concept within JBL itself. No less a legend than '4313B' himself referred to the link http://www.lansingheritage.org/image...omp/page07.jpg back in a thread in 2008. Apparently the options to experiment were encouraged within JBL at earlier times. I just wish I could find a similar 'call out' for the 434X series!

    Greg

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    You once had working 4425s, and now you have empty cabinets? please throw em on a pallet and ship them to me please!! But I see your point - yes, two individual cabinets will be stiffer than a single, but placing the mids/tweeters etc becomes chore. Unless they sit on top, in a separate box, with the 4425 boxes upside down?

    As for 2 woofers...for example two LE14As should work well in anything from 4 to 8 cubic feet volume. Optimum is someplace near 3.5 cu feet each, tuned to around 30Hz - lots of advice on this subject in past threads. So yes, a pair of them in a 7 cu feet cabinet is smaller than a 4350, but possibly bigger than a 4344. The 2 14"ers will have more cone area than a single 15 - maybe about the same as single 18 - BUT that doesn't mean it will work better than a single 18. I've thought of this a lot actually, and having 8 LE14As hanging around I spend a lot of time thinking about how to use them (and 'mini' 4350s have come to mind...). In the end I concluded that JBL spent lots of time, effort and most importantly educated thinking/listening/designing before producing the 43XX monitors that I can't reproduce. Maybe you should just build a 4344 or 4345 clone?

    You should also research the "helper woofer" concept as used in the 4435 and the current Everest. There has been plenty of discussion here about how this is done, and the crossover networks are available to study. BTW, the 4435 and 4350 dual woofers allowed those systems to reach extremely high SPLs with low distortion - I don't know the exact numbers but the charts are here somewhere... we're talking "hearing loss" levels of SPL at very low distortion levels!

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    Quote Originally Posted by tomee View Post
    You once had working 4425s, and now you have empty cabinets? please throw em on a pallet and ship them to me please!! But I see your point - yes, two individual cabinets will be stiffer than a single, but placing the mids/tweeters etc becomes chore. Unless they sit on top, in a separate box, with the 4425 boxes upside down?

    As for 2 woofers...for example two LE14As should work well in anything from 4 to 8 cubic feet volume. Optimum is someplace near 3.5 cu feet each, tuned to around 30Hz - lots of advice on this subject in past threads. So yes, a pair of them in a 7 cu feet cabinet is smaller than a 4350, but possibly bigger than a 4344. The 2 14"ers will have more cone area than a single 15 - maybe about the same as single 18 - BUT that doesn't mean it will work better than a single 18. I've thought of this a lot actually, and having 8 LE14As hanging around I spend a lot of time thinking about how to use them (and 'mini' 4350s have come to mind...). In the end I concluded that JBL spent lots of time, effort and most importantly educated thinking/listening/designing before producing the 43XX monitors that I can't reproduce. Maybe you should just build a 4344 or 4345 clone?
    tomee,

    Not to worry. I 'rescued' 6 4425s out of New York and paid outrageous shipping to have them sent to Texas. They were going to be 'parted out'. I saved them. I'm one of the 'good guys' who will pay to save a speaker!

    The woofer surrounds were completely gone. I'm in the process of paying to have all the 2214Hs fixed. The tweeters I've tested have been OK, but really dirty. The cabinets -- I'm refinishing.

    Your second paragraph may be the 'clincher', and I may come to the same conclusion. BUT, the fact that no one has directly addressed in any detail all 3 of my questions, makes me think that maybe not many LH members have pondered something like your statement, "The 2 14"ers will have more cone area than a single 15 - maybe about the same as single 18 - BUT that doesn't mean it will work better than a single 18." BUT, what if it does? The only way to find out is to try. However, at the end of the day, I do agree the JBL folks were absolutely without equal, wrt design and build. However, I also think that in the 60s and 70s they were a lot more open to various combinations than we seem to be today -- both in their 'custom' speaker enhancements and their 'kits', as well.

    I hate that I got sucked into this JBL vortex! Different drivers with different horns with different adapters with different voice coils with different cones with different frequency dividers with different dome materials with different .............!!!!!!!!!!!!!!!!!

    But, as you can see it doesn't bother me ...............bother me...................bother me.................bother me.

    Greg

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    Senior Member SEAWOLF97's Avatar
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    Quote Originally Posted by cgregory4 View Post
    "The 2 14"ers will have more cone area than a single 15 - maybe about the same as single 18
    Greg
    My handy/dandy calculator shows (assuming size is as spec'ed)

    14 incher has 153.938 in2 ,
    so 2 of 'em abt 308

    18 has 254.469 in2
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    just wait a couple minutes!”

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    Senior Member 1audiohack's Avatar
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    Hi Greg;

    I have been around this topic a bit and here's my take, while I listen to a pair of 4435's I might add.

    Q1, Are two woofers better than one?

    Hell yeah! If ones good, two's got to be better right? In reality it depends, on many things but in short, and in my opinion, yes. This is based on the fact that I listen LOUD on occasion and woofers get dirty when you push them hard. Take the 4435 for example in comparison to the 4430, (which I also have here) are literally an order of magnitude cleaner in the lower octaves due to the shared duties of two woofers. Half of that due to the fact that the work done by each is halved and then is halved again from mutually coupling two coincident radiation sources in close proximity to one another. Cut the required excursion and you cut the distortion.

    Q1a, Will two 12's "bring it" better than one 15"?

    Depends on what bring it means to you. To me? I like well controlled drivers so if you compare apples to apples,,. Lets use 2206's, 2226's and 2241's here, the common part of these transducers is the motor assemblies, they are identical. If you do the math a pair of 15's have about 63 more inches of cone area than a single 18, and fully twice the motor force power. Which do you think will have more punch, or pop, or snap?

    Q2, Cabinet Volume?

    You just have to imagine that JBL, being a manufacturer of both cabinets and transducers, would pair them optimally or very closely at least. A good source for info? You bet.

    Q3, Two woofers in one cabinet, separated or not?

    For me this depends on how high you are going to use them. You need not worry about standing waves until the enclosure becomes acoustically large ie one half a wavelength at the highest frequency of interest. A sub enclosure crossed out at 80Hz needs no thought given to its internal dimensions until one of them reaches right about seven feet. This is a very nice gift from the science of small room acoustics, a degree of design freedom that is rare indeed in the world of acoustics. The problem comes at you fast however as at 1000Hz you only get about 6.75" so at some point you are going to have to deal with internal resonances. If I am going to run a pair of woofers up fairly high, I split the box with a divider, no ports, that is a variable that I see no reason to explore as I see no possible gain for the good.

    On the cabinet size vs driver thing, yeah you can put a driver like a 2241 in an oversize box and port tune it low and EQ it flat, but I have never been able to get them to sound really good doing that, that why JBL made 2245's. It has become apparent to me through much, much, much trial and testing that the more you have to force a design, the harder it is to get great sound form it. Use the right drivers for the job.

    I am all about taking the path that leads to knowledge. When you step out and do, you gain knowledge and experience and that first hand knowledge is power. But realize this, that even though you can surely figure this all out on your own, a good deal of time can be saved by searching and understanding successful designs that already exist. JBL has done a lot of this homework for you.

    Oh yeah, never listen to anyone on the internet!

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

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    Senior Member grumpy's Avatar
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    Especially those of us over 40!

    nice response

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    Senior Member honkytonkwillie's Avatar
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    Quote Originally Posted by cgregory4 View Post
    1. Please allow me to refer back to my 'silly' example of two 4425 cabinets attached side-by-side. Both woofers would 'see' a stiffened internal brace between the two drivers -- in fact, twice the thickness of that original internal surface. Since the internal bracing would be enhanced anyway, is there an advantage to porting between the two woofer chambers?
    Total isolation and separation of the two woofers isn't critical or necessary, but each still needs its required space available. That is, if a single woofer needs 3.5 cubic feet of cabinet space, a second identical woofer will need another 3.5 cubic feet. You would then simply build a 7 cubic foot enclosure. Bracing is important though, as panels can flex and resonate.

    Some very exotic and complicated multi-woofer/multi-chamber designs exist that employ porting between chambers, but the complexity/bang-for-the-buck ratio is very high. Save that for your second project.
    Quote Originally Posted by cgregory4 View Post
    2. By using a 'known', proven, effective volume for each woofer, a new enclosure does not need to be designed and built from the ground up -- although obviously highly modified. Going a step further into the absurd, what if the center double wall of the enclosure was milled to the shape of a driver plus horn? Done properly, maybe slightly above the centerline of the enclosure, I don't think much stiffness nor cabinet volume would be affected. What do you think?
    This part isn't as hard as you might think. In the Dark Ages of Loudspeaker design (pre Thiele-Small,) finding the best enclosure for a given speaker was much more of a dark art, fraught with trial and error and successive approximation. (I think so anyway, it was long before my time.) But these two guys get most of the credit for developing the necessary equations which allow you to take the specs of a given woofer and predict its response behavior in a given enclosure, with a given vent if desired. Loudspeaker design software takes these equations and makes it really easy to simulate speaker and cabinet designs, so you can very quickly determine the "best" enclosure. Just design bracing around any speakers that are in the way.
    Quote Originally Posted by cgregory4 View Post
    3. What remains is the specification of high and ultra-high transducers that have minimal impact on cabinet volume -- not a difficult task, do you think?
    Just estimate how much volume these elements take up and oversize the cabinet you eventually build.

    Edit: I began writing before audiohack's reply showed... hopefully our posts are complementary.
    Last edited by honkytonkwillie; 08-21-2014 at 10:31 PM. Reason: Added the Edit:
    I control the treble.
    I control the bass.

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