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Thread: Acoustic (Air) Suspension

  1. #16
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    So Zilch I was just wondering how much the tone of you l100's in that picture changed because blocking the port seems like a very easy thing to do and I am bored enough to try it. I know I'll lose some efficiency but it shouldn't be that big of a deal. I think it would from what has been described change the bass from a thump to more of a roll. Also I won't damage my midrange by putting all that pressure on it will I?

  2. #17
    Administrator Robh3606's Avatar
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    Also I won't damage my midrange by putting all that pressure on it will I?
    No the midrange is in a subenclosure.

    Rob

  3. #18
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    Now I just need to figure out how plug the port. I wonder if that metal thingy Zilch has would work for the intake of the port inside of the cabinet? If not I can always stick it on the outside and call it a "boutique" tweeter.

  4. #19
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    Quote Originally Posted by SETriode
    I know I'll lose some efficiency but it shouldn't be that big of a deal.
    If what's shown in the BB6P simulation (and my measurements) is correct, what you lose is not bass efficiency, but rather, the entirety of the anomalous "bump" from 50 - 400 Hz, to which L100's boominess is largely attributable.

    Many L100 lovers would miss that artificial bass coloration initially, but with time, perhaps, appreciate the more natural bass and improved transient response. You can see that the low bass frequency response remains essentially the same, which is my experience listening to the L88s nearfield. I suspect I could actually put them next to a wall now, to extend the bass response via boundary effect, without them booming me to death.

    What's stunning is the difference in behavior of the cone. It's loose and floppy with the port open. Once you plug the port, the effect of the enclosed air "cushion" is immediately apparent in the stiffness of the suspension.

    The port in my L100s is 2.75", and the 3" plug type shown required a bit of filing of the rear metal disk to get it to fit, so a little effort may be required. It's a $3.49 plumbers' test plug from the hardware store. The L88 ports are 3", so no problem there, just pop it in and tighten. You'll be listening to the difference in a matter of minutes, in either case....

  5. #20
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by SETriode
    Now I just need to figure out how plug the port. I wonder if that metal thingy Zilch has would work for the intake of the port inside of the cabinet? If not I can always stick it on the outside and call it a "boutique" tweeter.
    With proper handling, you can enjoy the benefit of MANY six-packs from your pals as they try to induce you to disclose the secret of your new L100 tuning.

    Occasionally go over and tweak the wingnut while they're listening.

    "THERE, that's MUCH better now, don't you think?"

  6. #21
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    Zilch, you could up the wager from 6'ers to cases by using an inflatable test plug instead of compression (found only at wholesale suppliers). An added bonus is the much wider range of ports a single plug will cover (balloons also work in a pinch as temps). No need for a compressor, an old football pump and adapter, or a bicycle pump, works fine. The reaction from observers is....what you'd expect.

    The reduced excursions you note can have a big effect on driver longevity, not to mention reduced distortion by keeping things within their range of linear response. Excursion becomes less of a factor for max response, as coil burnout takes its place as the limiting factor.

  7. #22
    Senior Member Hoerninger's Avatar
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    Quote Originally Posted by moldyoldy
    The reduced excursions you note can have a big effect on driver longevity, not to mention reduced distortion by keeping things within their range of linear response. Excursion becomes less of a factor for max response, as coil burnout takes its place as the limiting factor.
    At another place in this forum Steve mentioned Tom Danleys recording of July 4th fireworks:
    Quote Originally Posted by Steve Schell
    It's unbelievable!
    And a great task for closed boxes.

    ____________
    Peter

  8. #23
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    Ahh that is a drain plug! I recognized it vaguely but was drawing a bit of blank. Later tonight I think I'll pull one of my woofers out and measure the opening to the port on the inside so i can keep my l100s lookin pretty especially once my 104h-2 midranges arrive. Should i also go out and grab some acoustistuff for the cabinet? I think last time i looked in there it was pretty spartan.

    Ooooo this weekend is gonna be sweet with my new amp and "new" l100's!!!

  9. #24
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    Quote Originally Posted by SETriode
    Later tonight I think I'll pull one of my woofers out and measure the opening to the port on the inside so i can keep my l100s lookin pretty especially once my 104h-2 midranges arrive
    Closing the port at the front recovers the duct volume into the box, even though it stays in place. This will provide a bit more bass extension than plugging it inside the box.

    Quote Originally Posted by SETriode
    Should i also go out and grab some acoustistuff for the cabinet?
    I haven't completed my damping determinations, but they're sounding a bit "boxy" with just the stock insulation in there.

    Maybe you try different fills and help us out with that part.

    [If they sound like poo, remember it'll take four to six weeks for them to break in.... ]

  10. #25
    Senior Member Phil H's Avatar
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    Zilch,
    I was curious if the black woofer in the L88 has a folical with a model number. Was there a 123A without the -1 or -3?

  11. #26
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Phil H
    Was there a 123A without the -1 or -3?
    Well, I don't remember now, but I'll be opening it up again to change the damping in the next day or so, and will make a point of documenting that; it's important.

    The nearfield bass response of the two woofers is a bit different, so I'm thinking of measuring a bunch of them in the same box, too. I have four 123As and two 2213s here somewhere, I think. Also want to measure some D123s.

    That's more like something for the weekend. It'll be interesting to see what WT2 says about all of them. Gotta take out all the insulation and measure the interior dimensions precisely to get it right.

    [It's tough pullin' them outta L100s.... ]

  12. #27
    Senior Member duaneage's Avatar
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    A friend of mine showed me his L88Plus speakers and thought they were the best thing he ever heard. I shoved a rubber ball into each port and he remarked that the bass was " all gone".

    After a few songs and a little more volume he began to agree that they sounded better. Repositioning them against a wall increased the low bass output a little and they did handle more power that way. The rubber balls remained.

    Zilch has proven that using a driver different than what it's T/S parameters suggest may be a good marketing trick but in the end it's better to do it right. I wonder if the world wide supply of drain plugs will be affected by this. Might be a good time to stock up.

  13. #28
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    Well i didn't make it to the hardware store tonight, so i decided to stuff a rolled up towel into the port on my l100 and wow it is sooooooooooooooooooooooooooooooooooooooooooooooooo oooooo much better. these things are actually listenable now!

  14. #29
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    Think i might have found an alternative to the towels, rubber balls or metal drain stoppers. Think it would stay in there or get shot out at listener level?

    http://cgi.ebay.com/ws/eBayISAPI.dll...MESE:IT&ih=013
    More

  15. #30
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    The plumbers' test plug is rubber, actually. The metal plates squeeze a thick rubber washer when the wingnut is tightened to make a secure seal.

    Wingnut in the way? Replace with a hexnut and a shorter carriage bolt.

    [Cheaper than that stopper, too.... ]

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