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Thread: Ways to imitate a larger box

  1. #1
    Founding Member earthtodan's Avatar
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    Ways to imitate a larger box

    I have a little challenge. I'm trying to install a pair of Fountek FR89EX full ranges in my kick panels, and there is just enough room for the speaker. I am planning to make a fiberglass enclosure for it out of HyperFiber. It wants a 1/2 liter enclosure (about the size of a pint glass) and there is room for about 1/4 of that.

    So I was thinking, if I made a flexible surface on the back of the enclosure using some less rigid material, would the speaker "see" a larger box? The idea is to give it less damping. If there is no merit to this idea, what are my options?

  2. #2
    Founding Member earthtodan's Avatar
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    For visual reference, here is where the speaker is going to sit.



    And here is the limiting factor, the mess of wiring harnesses (only on the driver's side).


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    I wouldn't do that, though this thread is older and you may have already.

    One thing that MIGHT be worth a shot is activated charcoal. KEF has done some interesting work with that. (Google "KEF ACE.") Though in the same breath it's worth noting that they don't use it on their better speakers, and they don't use it in their new super-slim speakers either.

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    Founding Member earthtodan's Avatar
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    I haven't done anything yet. I made a pass at fiberglass with epoxy resin and it didn't come out very well, and other than that I've been too busy to get anything done. Why do you think it's a bad idea?

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    Devil's Advocate Adam_MSS's Avatar
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    I don't think any idea is "bad" but I think this one might present a moving target. By adding a flexible surface you introduce a lot of unknowns into the equation. The closest analogy I can think of to using a flexible surface is the use of a passive radiator. If you look at passive radiator designs you'll see that there are a lot of well defined parameters being evaluated to arrive at the desired damping, resonance, etc..

    You might want to look into an aperiodic alignment where a resistive membrane allows passage of air. ErinH has a lot of successful experience with that approach. I'd definitely pursue heavy fiber fill to help increase the effective volume of the enclosure.
    You don't use science to show that you're right, you use science to become right. - R.Munroe

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  6. #6
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    Aperiodic is the way to go if I were building. Homemade, and the whole panel would get filled with poly during assembly (between the kickpanel smooshed up into the wiring) just to try to soak up any minor backwave that does propagate from behind the panel.

    After that, it's tuning.

    IMO (get ready for an opinion here) your staging will be forever narrow as heck if you crossfire your midranges down low. I would try to toe them out a little bit. Check out labcoat's kickpanels. Awesome job, I think his design could be modified for your car. (you would not lose your deadpedal at all)

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    Quote Originally Posted by Adam View Post
    You might want to look into an aperiodic alignment where a resistive membrane allows passage of air. ErinH has a lot of successful experience with that approach. I'd definitely pursue heavy fiber fill to help increase the effective volume of the enclosure.
    This is what I'd suggest as well. Aperiodic is never an optimal solution, but it's a great compromise for situations like you have. It can be difficult to find the right material that will provide the right damping without choking the driver.
    Just because you don't understand the data doesn't mean it's not relevant.

  8. #8
    Tester Extraordinaire ErinH's Avatar
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    AP is the route I'd go as well. You lose efficiency (and, iirc, these drivers don't have high sensitivity to start with), but if you have the power to make it up and the patience to experiment with fill amount/material (density) it's worth a shot at the least.

    If you want to go the AP route the VERY FIRST THING I SUGGEST BUYING IS:
    Dayton Audio WT3 Woofer Tester
    Your ears: The best tools you have... and they're free, too!

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    Quote Originally Posted by Whiterabbit View Post
    IMO (get ready for an opinion here) your staging will be forever narrow as heck if you crossfire your midranges down low. I would try to toe them out a little bit. Check out labcoat's kickpanels. Awesome job, I think his design could be modified for your car. (you would not lose your deadpedal at all)
    Not mine I think you mean khail19 kicks it can be fond here or some were on another site.

    R-

  10. #10
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    wow, I missed that one by a long shot. Thank you for the correction. khail's kickpanels are exactly what I was referring to.

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