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Thread: 2012H enclosure size?

  1. #16
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Miss Orchid
    Even now we are designing and building your precious JBL speakers.
    Listen to the Zilchster now, hon:

    You'd be better served concentrating on toilets, first.

    [And running water to flush 'em.... ]

    ALSO:

    Sex is NOT a function.

    [As with ALL matters occidental, seek appropriate guidance from The Rolling Stones in thiis.... ]

  2. #17
    Senior Member spkrman57's Avatar
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    Miss Orchids style makes me think of someone from this forum..

    Someone who no longer posts with us anymore under the same name.

    I might be wrong also!!!!!


    If it is the same - it is okay with me.


    Ron

  3. #18
    Member Miss Orchid's Avatar
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    Listen to the Zilchster now, hon:

    Please excuse me, zilch is all that I understood from your post.
    2012H's working ok now?

  4. #19
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    The part about China taking over the world economy sounds likely if we do not stop shopping at Wallmart. And I think something is fishy in Ohio as well. Welcome back

  5. #20
    Administrator Mr. Widget's Avatar
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    Too late.... didn't you see BooBoo's post... Walmart's already off on their next conquest. Soon they'll be touting:

    "The Cheapest Junk in the Solar System."

    Widget

  6. #21
    Senior Member GordonW's Avatar
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    Quote Originally Posted by Miss Orchid
    There are JBL systems with Qtc numbers much lower than 0.5 and JBL thought that was beneficial. The readers of this forum are urged to examine group delay figures for sealed systems and vented systems in a variety of box sizes, and in the case of vented systems, a variety of tunings. Sealed boxes can be too small and can decrease power handling capacity due to thermal issues.
    There are cases where low Qtc numbers in a sealed box are beneficial. A driver with a pronounced rising response, is not usually one of those situations. It will aggravate the rising response, by "sloping downward" the bottom end response near box resonance.

    As for power handling- if that's an issue, then do what JBL did in other cases- use a METAL enclosure, or something similar.

    Also, it is a fundamental fact of physics that a damping Q of less than .5, will cause delay, in the sense that it will prevent the initial rise of a signal from reaching full amplitude initially. This will, in any practical context, result in a "dulling" of transients... a "slowing" of the percieved response of the driver.

    Quote Originally Posted by Miss Orchid
    Also of interest might be the use of sealed boxes as two poles of a high pass filter.
    That is exactly what I was implying above. A sealed box rolloff plus a second-order highpass crossover, can be combined to act as a 4th order highpass composite "acoustic filter". If the crossover is set at the box resonance, then the resultant response will have an effective Q of the PRODUCT of the Qs of the two "filters (the box response plus the crossover) multiplied together.

    In fact, if the active crossover is state-variable (ie, you can change the Q of the highpass crossover), RAISING the Q of that section a bit, will "EQ" the bottom end of the driver upward, without having to do it in the DSP EQ section. Might result in a lessening of the "digital clip" that was alluded to...

    My suggestion for filter tuning, would be to put the speaker in a box that would give a Qtc of between .8 and .9 (.25 to .3 cubic feet), and dial in a Qtc in a second-order highpass filter, of about .9 or so. This would result in a composite 4th order filter with a Q of between .72 and .81 or so. A very subtle boost of the bottom end, and not very much consequence in group delay. Higher slopes should not be necessary, since in the box described, the driver can handle full acoustic power at the box resonance frequency... with a higher-than-second-order highpass composite response, the driver excursion will DECREASE STEADILY below resonance, so there should be no acoustic power handling issues, whatsoever.

    Regards,
    Gordon.

  7. #22
    Member Miss Orchid's Avatar
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    Splendid points GordonW.

    There are cases where low Qtc numbers in a sealed box are beneficial.

    I do like that statement.

    Also, it is a fundamental fact of physics that a damping Q of less than .5, will cause delay, in the sense that it will prevent the initial rise of a signal from reaching full amplitude initially. This will, in any practical context, result in a "dulling" of transients... a "slowing" of the percieved response of the driver.

    Yes. There were certain cases where the overall performance desired resulted in Qtc values lower than 0.5 and any dulling of transients was deemed sufficiently inconsequential during extended listening evaluations. The products were put into production and brought to market.

    But I digress, this is specifically about the 2012H. Hopefully stevem and Baron030 find all this information helpful. Thank you GordonW.

  8. #23
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    Quote Originally Posted by Alex Lancaster
    Venerated Miss Orchid:

    I think You may find a life companion (none of that marriage stuff) in Ohio, ask for Mr. Giskard.

    I think running over students and newspeople with tanks was invented in Mexico City in 1968, there might be earlier cases.

    Check your Czech history of the mid 1950s to see the true enlightenment that tank discipline brings to the unbridled spirit of optimism. Truly crushing the imbalanced liberty of foolish dreamers, the Chi is restored as the negative and positive energy of life is balanced and all aberrations are smoothed out.

    Talk about flattening out your response curve: apply this lesson to to your enclosure and even the most novel responder can be brought into perfect balance.
    Out.

  9. #24
    Member Miss Orchid's Avatar
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    Usurped

    Baron, I feel like I hijacked your thread! Sorry!

    The rest of us can now share in any potential blame?

  10. #25
    Senior Member spkrman57's Avatar
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    Okay..

    I'll take my share of the blame. This thread has proved to be very interesting.

    By the way, did anyone say something about a 2012???


    LOL


    Ron

  11. #26
    Senior Member Ian Mackenzie's Avatar
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    Sounds like the JBL data sheet gives away all the clues.

    My Hp Colour Laser printer has product of China stamped on it so the must be getting it right on the score. China has long been the prefered location for multinational manufacturers to globalise. What the lady in the flower pot forgot to mention is that technology and up skilling of the labour comes from outside, so there is a fair amount of control over what's going on over there.

    Unfortunately a quick search on another forum reveals illegal breaches of IP from US based manufactures by pirates in China.

    The Doctor

  12. #27
    Senior Member edgewound's Avatar
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    Well...this has been an interesting read. The usage of certain signature emoticons, as well as linguistics, is quite revealing. Maybe Wal-Mart will own China soon.

  13. #28
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    Related? Not meaning to hijack, but. . .

    I have a similar concern about the doghouse for a 2123H. Using BB6, I get results that indicate a similarly sized vented box is somewhat flatter than sealed. This seems "counter-intuitive". What am I doing wrong? Particulars are:

    Vented 10 x 16.2 x 6.2, two vents 2.5" D x .75" deep. Fb 89.54 Hz (Shown in red).

    Sealed (bb6 suggested) 9.7 x 15.7 x 6 Fb 212.2 (Shown in blue).

    Applicaton:A four way system with active 24 db x-over from 150 Hz to 1100 Hz.
    Attached Files Attached Files

  14. #29
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Baron030
    I happen to be building a version of Daniel's Ancient Audiophile's quest for the Ultimate Home System.

    Over the years many people have made reference to a Drew Daniels based or inspired system.... I always shake my head and wonder why. I would hazard to guess that virtually everyone who has made this statement never actually heard the Daniel's System. To pull off a system of that mass and magnitude and not have it sound significantly worse than the sum of it's parts is quite feat. A feat that Daniels was able to accomplish through significant effort aided by his significant skill.

    I suppose some people are drawn to it by it's sheer mass.... but today's array PA systems are significantly superior to the Grateful Dead "Wall of Sound" and have a much more cohesive sound. To build a version of the Daniels System and not end up with a smeared wall of sound is almost impossible. I have heard that Daniels himself recommends that people buy LSRs and subwoofers over attempting the "Daniels System."

    I am not saying that a scaled down system using some of Daniels' ideas isn't quite possibly a good idea, but to follow it part way without really knowing what you are doing, while quite possibly a real kick in the pants, be prepared to lower your audio expectations.

    Widget
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  15. #30
    Dang. Amateur speakerdave's Avatar
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    No response contour information

    This is the big shortcoming in Drew Daniels's system--no response tailoring information whatever. The early versions prescribe a pair of UREI 525 crossovers, but the later system uses some BGW amps with custom contour cards for the various drivers. Go figure. And he does not share the contour information with the reader. I looked at this myself before deciding that it was nothing but a small scale PA, probably a pretty good one, but I doubt it would be at all satisfactory for in-home use, as Widget says. Remember, his target audience is the dedicated crowd that has been listening to D130's with N2400's and 075's since 1957 and now have the leisure to spend some of their children's inheritance on a balls-out system. Drew's to be commended for recommending the LSR32. In fact he was fairly adamant about it; if I find the reference I will post it, but I confirm Widget--it's out there. If you want to make a home-brew large format JBL, study the studio monitor series, including the K2's, and pick one you can get the parts for and copy crossover information. Anything else is fraught with difficulties.

    David

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