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Thread: Altec 416-8A enclosure design

  1. #1
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    Question Altec 416-8A enclosure design

    I'm currently trying to design an enclosure for the 416-8A, and experiencing some challenges.

    First, I can not find any T/S parameters for this speaker. I can find them for the 416-8B (incorrect in original documentation, and correct numbers derived in the 1980's found here: http://alteclansingunofficial.nlenet...ele-Small.html). The problem is that the 416-8A is different than the 416-8B (their free air resonance frequencies are 25Hz and 24Hz, respectively).

    Second, I don't know what kind of port size I need for an arbitrary sized cabinet. I'm trying to alter a 612C cabinet slightly to increase the volume to >= 7.25 cu ft (7 cu ft when removing the 0.25 cu ft the speaker displaces). I've read that the 416-A/B/C/Z requires at least 7 cu ft to become effective. The official Altec literature says ~14 sq inch port for a 612C (source: http://alteclansingunofficial.nlene...letters/AN-5_CustomizingAltecLFEnclosures.pdf), but that seems really small. I've also read that Altec literature can be incorrect and/or contradict itself. How do you calculate the "optimal" port size, or at least the minimum port size?

    Does anyone have any advice, experience, or documentation that could help my project?

    Additional context: I want a multi-genre speaker system for a large, rectangular room (17 x 45 ft - 765 sq ft with 12 ft ceilings). I'm putting custom horns on top (outside of the enclosure) that will crossover at 800Hz. Will play jazz/classical/soul via vinyl, but also use for regular listening like hip hop, pop, etc.

    Thank you!

  2. #2
    Member Greg_M's Avatar
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    Download WinISD (free) and play with it.

  3. #3
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    Quote Originally Posted by Greg_M View Post
    Download WinISD (free) and play with it.
    I may be mistaken, but using WinISD would assume that the software has the Altec 416-8A (highly unlikely given the lack of information on this driver), or that I have the T/S parameters to manually enter into the software (I don't). I could use something like DATS to measure the T/S parameters, but I would have no way of knowing if those are representative of a well functioning example of the 416-8A. I could end up designing a cabinet for a damaged/flawed speaker, rather than the model I am designing the cabinet for.

    Furthermore, when using WinISD, what output(s) from a cabinet design should I be optimizing for?

    Disclaimer: this is my first project and I'm learning/doing all this stuff for the first time

  4. #4
    Senior Member RMC's Avatar
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    Hi Konsl,

    You worry about a one hz difference in Fs, wow. This is probably even less than the manufacturing tolerance for each of those two drivers with regards to Fs. I wouldn't be deprived of a single second of sleep for such difference...

    Port area of about 14 sq.in. is just a little larger than a 4" tube inside dia. So go with a 5" internal dia. tube and that's it, you're in business. Nothing wrong with going larger, such as 6" vent, if cabinet space permits, however these old drivers are not high power capability (30W), rather high efficiency/sensitivity. So maybe you don't really need a 6" vent.

    JBL's own rule of thumb for port size is 1/3 the woofer diameter, so 15" driver = 5" vent.

    You mention a 7 cu.ft. cabinet but no box tuning frequency. Presumably you have driver Fs as box tuning frequency in mind as was frequently the case in the old days? Regards,

    Richard

  5. #5
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    konsl,

    Here's an interesting blog to read ( click the pic ) ;



    Of note; the author of the blog was able to find a lot of satisfaction with an enclosure that's about 1/2 the volume that you'll be using ( iow; I think you are on the right track to sonic fulfillment ).

    Also ( IMHO ); you're sweating details that are pretty trivial in the large picture ( as Richard said ).

    I would recommend testing your own woofers to get an idea of their relative motor strength compared to stock ( iow; get the TS Parameters for them ).



    Make a Test Jig and then use something like REW or LIMP to get the parameters.

    As mentioned, use winISD to see what sort of woofer/box alignment you'll get when using different box taunings.

    Once again ( the author ) got respectable bass out of a tiny box ( once room/corner gain kicked in ).




  6. #6
    Senior Member Sootshe's Avatar
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    Hi Konsi,

    Here's some plans & info from some old Altec literature that may be useful.

    Or you could go with the Altec Model 19 cabs. If you want the original plans for them PM me & I can email them to you.

    Regards.
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