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Thread: 4412 Enclosure Volume and Speaker Alignment

  1. #1
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    4412 Enclosure Volume and Speaker Alignment

    Good evening guys, first post for me here and I hope its not to much to ask.
    As a lot of new members Iím sure, Iíve lurked around a long time.óso long I can no longer find all the info Iím searching for.
    A while back I picked up some 4412s(my first experience with JBL tat wasn't a concert or a wedding) and absolutely am impressed with them.
    I listen to them in the horizontal position with the ports to the inside.
    They are matched up to and all Audio Research setup with an M&K sub.
    That being said, they need new cabs.
    So before I undertake the challenge, I have a round of questions I feel should be run by the experts here firstóIíve spent at least two weeks researching, so if a question has been answered here, please excuse me as my key words may have not been correct.

    1. My first query involves confusion with regards to the cabinet volume.
    Iíve found that the 4412 and 120Ti share almost the same cabinet volume.
    The free speaker software Iíve plugged the JBL T/S Parameters into (parameters from the JBL archive and similar numbers from a post I read on here) for the 128H, show a 1.7ish ft^3 enclosure and the JBL archive calls out an even larger enclosure at 2.5ft^3 for this woofer.
    Both enclosures are larger than what is used in the 4412 and 120Ti.
    Is there a reason for the smaller enclosure of the 4412 and 120Ti than JBL recommends?
    In the groups opinion, if I went to a larger enclosure volume, would there be a conflict with reusing the oval JBL port from the 4412?

    2. My second.
    I have ZERO problems with the horizontal design of the 4412óI actually kind of like the lookóbut out of curiosity, if I changed midrange and tweeter alignment to vertical, as in the T120Ti, does the crossover design need modification?
    To best find an answer to this, Iíve used the 4410 for a research model as it was designed both horizontal like the 4412 and vertical like the 120Ti.
    I can't completely confirm the crossover is the same for both configurations of the 4410, but if they are the same, am I then wrong to assume itís a relatively safe bet the 4412 can have the woofer, midrange and tweeter aligned similarly as the 120Ti?

    I hope this all makes sense to you guys, and appreciate any feedback.
    I wish I could reciprocate, but unless this turns into a finish carpentry forum, Iím a student here.

  2. #2
    Senior Member DavidF's Avatar
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    My second home-brew enclosure system used both the 128H (L112) and 128H-1 (4412 and 120Ti) in a variety of combinations.

    I don't have the enclosure any longer so I can only base my response on my pretty-close recollection.

    The cabinet was floor standing with a tapered front baffle about 16" wide. The net internal volume was targeted for 2.5 cu ft but it came out a little larger. Probably 2.7. I used heavy bracing and I never went to the trouble to be exact in determining the net volume. Instead I relied on varying the port length to tune the cabinets to 29 Hz. I really don't recall the port length but safe to say it was usually between 6 and 7.5 inches (4 inch PVC pipe).

    The drivers were vertically aligned with the tweet and mid offset the vertical mid line by 2 or 3 inches (mirrored). I would not expect the vertical alignment v. the original alignment for the 4412 to give you any concern. It may actually be a better alignment overall. The drivers on the 4412 were arrayed that way to allow the speakers to fit over a recording console or similar application. This allowed for better perspective for near-field monitoring.

    I never tried a smaller volume for the 128H woofers. I found the 2.5+ enclosure quite good in bass quality and extension. A bit more extension a la the L150A may be desirable but I was going for a more flat/over-damped alignment. The more compact system like the 120Ti or 4412 likely has a bit more "fuff" in the bass response-not as tight or extended- but still works very nicely.

    Finally, I would not count on reusing the oem vent from the 4412 in an enclosure of any different size.
    David F
    San Jose

  3. #3
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    Thank you you for the response

    Quote Originally Posted by DavidF View Post

    Finally, I would not count on reusing the oem vent from the 4412 in an enclosure of any different size.
    This could be the deciding factor in box size then--I wanted to reuse the plate holding the tweeter and mid controls and the built in port tube.

    I will do some research on port tube volume and see how the port tube changes with enclosure volume.

    I have a lot of respect for the speaker designers and sound of the 4412 and not sure I want to ruin that by over complicating things--which I have a tendency to do.

    FWIW, I have access to a CNC machine and opporator--I share space with a machine shop--i am concidering a cool looking stacked plywood enclosure, but I know almost ZERO about designing port tubes and crossovers so staying close to original box volume might be best.

  4. #4
    Senior Member Doctor_Electron's Avatar
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    "Damn the technicalities. Full speed ahead!"

    Quote Originally Posted by ltngstruckfirst View Post
    I wanted to reuse the plate holding the tweeter and mid controls and the built in port tube.
    First, welcome aboard.

    If you are building new enclosures you could use the original 4412 port / L-pad assembly and add another port, on the back of the enclosure or wherever its location suits your design.

    I'm pretty sure a larger box for the 128H-1 12 inch would have a larger port than that of the 4412 box, so you could divide the required port volume of Pi x radius squared x length between the original and new ones.

    If imaging and soundstage are important to you, a vertical driver alignment will be much better than the "clustered" arraingement of 4412.

    I have had the 4410's (vertical) since 1986 and got a pair of 4412's in 2007. I tried all sorts of positioning schemes to get acceptable imaging from my 4412's, to no avail.

    Finally I simply re-routed the openings of the 4410 cabs for the 128H-1's which now give the great imaging of the 4410's vertical alignment and the IMO superior bass performance with the larger woofer.

    It took about 10 minutes per cab of routing once the requisite measurements were done.

    BTW the 4412's do need more amp power than the 4410's for reasons I can't explain, considering their similar published sensitivities.

    Best of luck with your project. You can gain enough practical knowledge about porting with some research and the excellent advice of the mavens, guru's, and just plain joes frequenting this wonderful website.
    Last edited by Doctor_Electron; 04-29-2016 at 03:27 PM. Reason: Forgot greeting, rude.

  5. #5
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    Thank you Dr E!
    Very valuable feedback in your post also.
    Although I've seen it 1Mx, the thought of a second port never crossed my mind, not even earlier today when I was trolling the DIY M2 thread...lol
    This why it's important to talk things out.
    So, based on two great replies, and concidering this is my first plunge into an adventure of this magnitude, and I want to get it done, at this point it looks like:
    1. Stick with the same-ish internal cabinet volume.
    2. Reuse the original crossover and original port.
    3. Go with a vertical driver alignment.
    4. Do my best to design a well braced, cool looking enclosure.
    Im meeting with the CNC guy Monday or Tuesday, so I will be drafting up a template over the weekend.

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