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  1. #21
    Join Date
    May 2009
    Location
    Dallas, TX
    Posts
    880

    Default

    bbyquist,

    I noticed you mentioned the JL Audio HD900/5 for your in-boat needs. Keep in mind that this model is ideal for four highpass speakers but definitely not six. Since its biased specifically for 4-ohms it will drop to 75 watts at 2-ohms and any inequity in front and rear channels will affect the power supply voltage on the highpass section which in turn affects the output of the other two channels. So only use this amplifier for a sub and four with all four satellites being an equal 4-ohm load only. Don't get me wrong. I think the JL HD900/5 is the industry's most sophisticated amplifier as long as you abide by this one restriction. If you are going to run a sub and six coaxials then look into the JL Audio XD600/1 and XD600/6 combination pertaining to subwoofers. Under the driver's helm console is the preferred location. Surface area in a marine environment is the most leverage you've got and there's no better way to maximize your effective surface area than going bass-reflex. We've done single 10-inch systems that would literally flex the hull and disassemble the dash so you can definitely get it done with the right 10-inch sub correctly executed.

    Here is where to start in determining which size is right for you. A bass-reflex 10-inch enclosure will usually consitute 2.25 cu. ft. external displacement including port volume and stock. Its usually 3 cu. ft. for a 12-inch enclosure at minimum. If you build a bass-reflex enclosure that is too small it will tune too high. You can remodel the alignment to tune it where you want it within limits but several sacrifices will result including a.) an under-damped alignment that is super loud and peaky but compromises a linear response and tonal construction, b.) a noisy port, c.) a small port volume that is overdriven by the woofer's collective surface area and excursion resulting in limited power handling, plus another couple of abberations!

    So the best size of woofer is the one that is truely optimized in the enclosure that best fits your available space. Your starting point is to determine in concise measurements how much space you are willing to give up in consideration of leg/foot room and other enfringments. Once you've arrived at that volume your enclosure type and size will dictate the best woofer option. This way you're guaranteed to get the best available performance. Its an objective method that beats forcing the enclosure to fit the woofer (putting the cart before the horse so to speak).

    David
    Earmark Marine

  2. #22
    Join Date
    Apr 2010
    Location
    Eastern Washington
    Posts
    97

    Default

    David,
    Thanks so much for the input on the jl hd900/5. I really thought I had found the amp I needed, but I guess I'll keep looking. I would have just made a really expensive mistake if it weren't for advice like this.

    While I am definitely on a budget with this project, I'm not planning on doing it twice. So I will ensure that I use an enclosure that is designed both for the marine environment and for the sub that goes in it.

    This is good stuff guys, keep it coming before I do something stupid!
    2007 Mobius LS

  3. #23
    Join Date
    Dec 2006
    Location
    Tigard, Oregon
    Posts
    3,016

    Default

    I'm running a JL M6600 6 channel amp to 6 Polk cabin speakers and the Kicker ZX700.5 to run 4 tower speakers and the sub. I've got a DVC 4 ohm sub so the Kicker is delivering 420W rms @ 2 ohms to the sub. Sounds great.
    Al

    2006 Mobius LSV

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