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  1. #11
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    Dec 2006
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    Quote Originally Posted by EarmarkMarine View Post
    cab,

    A bass boost is the last method to use in your particular situation where you've got an acoustic suspension woofer loaded into a free-air application that isn't even isolated front to rear. In fact, a bass boost will add to the problem rather than providing a solution. For now leave your crossover as is. And, take Phil's suggestion on experimenting with the phase.

    I see two different paths you could follow to improve your lows given what you have.

    If you're absolutely going to stay with your existing mounting configuration, instead of an enclosure, then you've got to convert to a real free-air sub. Sony, Kenwood, Clarion, Alpine, JL Audio and a few others make true free-air subs. JL Audio might make the best free-air sub but 200 watts is a little light for that model. The Alpine would do better with 200 watts. But your MOMO will not sound much better regardless of the steps you take as it is currently being used. Again, Phil is accurate in his assesment of the MOMO's parameters.

    As applied to free-air, the distant opening on the port side is a non-issue since the pathlength is so long. However, you would want to seal up the hole atop the hump which is very close to the sub. Total front to rear isolation is critical but only in close proximity (within several feet). Another issue is that the fiberglass hump is constructed with a very thin wall of fiberglass so this mounting surface could be reinforced to create a far more rigid baffle. This would provide a dramatic improvement over what you have now.

    Perhaps the best option is to position a side-firing small sealed enclosure over the top of the hump and extending toward the bow. This requires zero modification to the hump other than a carpeted cover panel over the existing opening. You could use your existing MOMO sub for the short term provided it hasn't become too fatigued from running it undamped. Eventually you could replace it with a 2-ohm woofer. This is an easy fit, especially in an '06.

    Currently your sub is in the bilge and all of your coaxials are in the coaming, so they do not share space and do not require further isolation. So you're good in that respect.

    David
    Earmark Marine
    David,

    Thanks for the response. If I go free air, is the JL Audio 10W3v3-2 the one I want? Since it's a 2 ohm sub, the Kicker will deliver 420w instead of 210w so will that be enough to adequately drive this sub? If I go the free air route, do I still have to seal the top hole and the hole below the footbox that leads to the under floor pipe/cable chase?

    Also, the footbox is actually stouter than you think - it's at least 1/2'" thick, maybe even 3/4" - it's not just thin fiberglass. I'll measure it the next time I remove the sub.

    Do you have a recommendation as far as some good songs to use for tuning/testing a stereo system? Something with a wide range of sounds and some good bass segments?

    Thanks,

    Al
    Last edited by cab13367; 01-05-2010 at 01:49 PM.
    Al

    2006 Mobius LSV

  2. #12
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    Dec 2006
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    Tigard, Oregon
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    Quote Originally Posted by philwsailz View Post
    The SKM10 is a good choice, since it is a water-proof, ready made sealed subwoofer system. It is not noticeable from the outside, but the front of the box is attached to the back of the box under and around the woofer with a bracing scheme that is molded-in during manufacturing. The result is a very rigid enclosure which is not typical of a typical "plastic" enclosure. If you have a place to put it, it could work well for you.


    I kind of like your option of attempting to seal the enclosure... It would be worth trying to figure out what volume you would end up with as a result though, just right there in that box. It might be too large, and it might be too small too, but if it were in the ballpark, it would not be too hardto do, and I kind of like how it looks now. I would pull the drop cloth out though... some sort of damping material will do a better job; pink fiberglass, or even some dacron polyester fiberfill... Your drop cloth is probablyt only reducing the net volume of the enclosure and not providing any damping.


    Keep us informed of your decisions, and I look forward to David's comments; he will have some ideas for you too...

    Phil
    Kicker
    Phil,

    I'll remove the drop cloth and see how it sounds. I think you're right, ultimately, sealing the footbox is probably my best bet. Then I can use the equipment I have and will have the clean look I like. I do plan to install a heater in the boat though and the water lines will have to run through the underfloor pipe chase, thru the footbox, and out the hole on top so I need to do that first before I seal it with the expanding foam.

    Phil, David,

    Thanks a bunch for your input. It's so generous of you to share your knowledge with me and others on this forum. You guys are the best.

    Al
    Al

    2006 Mobius LSV

  3. #13
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    Dec 2006
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    Tigard, Oregon
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    Quote Originally Posted by jmvotto View Post
    Al, I am following along closley and this is great info from you experts out there. Phil, David and Brian.

    We have a very similar system ( (jl m6600, polk db651 and the polk momo sub)so i am axious how it turns out. I went to my local audio place that does high end auto, boat and home. they carry JL and Alpine.


    i asked them about a free air sub for the boat and they steered me to the BA G3( tazz has this in an enclosure) They recomended this over both the Jl and the Alpine.

    Al, we can split the Buy one get one free for slight over 100.00 below.


    http://www.crutchfield.com/p_065G310...ures_and_specs

    http://mobile.bostonacoustics.com/ca...product_id=404
    Joe,

    I thought you were happy with the bass out of your system? I thought maybe your footbox is better sealed than mine.

    If I buy another sub, it will be a 2 ohm sub to get more output out of the amp. Also, I've looked at that Boston sub but the fact that it has a foam surround (instead of more durable rubber) is a show stopper for me. Don't know why they spec'd such a nice sub with a foam surround.

    Thanks anyway,

    Al
    Al

    2006 Mobius LSV

  4. #14
    Join Date
    Jan 2008
    Location
    Keuka Lake, NY
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    Al,

    I am happy but this thread certainly has me thinking??

    then the Jl is probably the sub for you.


    David,

    What is the song on the youtube video on the 2009 super air nautique? i love that video.

    When i get enough cash i be upgrading to the HLCD, hopefully you''l be able to ship to western NY.
    Last edited by jmvotto; 01-05-2010 at 02:50 PM.
    A Day at the Lake...Priceless
    A Day in Powder...Endless


    Joe V
    2012 Möbius XLV~ Loaded & Exiled
    2007 Outback V ~ sold

  5. #15
    Join Date
    May 2009
    Location
    Dallas, TX
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    cab,

    Acoustic suspension for a sealed box woofer is a fixed relationship. So you can't approximate it with a quasi-sealed or aperiodic enclosure and have predictable results. Go with free-air (infinite baffle) or acoustic suspension (small sealed). One or the other. But no combination or mixing your schemes.

    The JL Audio 10w3v4-2 is not a free-air sub and should not be used in your floor. Its just for enclosures whether sealed or bass-reflex. The appropriate JL sub is the M10IB5-SG-TB and its only avaiable in 4-ohms.

    If you are 'free-air' it means an infinite and unobstructed volume of air (the entire bilge for example). A free-air 10-inch sub usually requires a 3 cu. ft. enclosure or larger so that the woofer's 'Q' is unchanged which is the basic qualifier for free air. You cannot have too large of an enclosure. However, it should be sealed or isolated front to rear by a 1/8 wavelength 'to' and 1/8 wavelength 'from' the nearest large opening, for a total round-the-world path equal to a 1/4 wavelength of the lowest frequency you're expecting to reproduce, which would be approaching the woofer's free-air resonsance. And the resonance is higher on a free-air driver. From this you can deduce that a.) the hole in the top of the starboard hump must be sealed and b.) the hole in the port hump or other distant openings do not matter.

    In contrast, if you go sealed then it should be at or close to the optimum displacement (averages .65 internal net on most 10-inch drivers) and that means absolutely air tight in the strictest interpretation.

    David
    Earmark Marine

  6. #16
    Join Date
    Nov 2009
    Location
    Stillwater, Oklahoma
    Posts
    313

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    Quote Originally Posted by EarmarkMarine View Post
    cab,

    Acoustic suspension for a sealed box woofer is a fixed relationship. So you can't approximate it with a quasi-sealed or aperiodic enclosure and have predictable results. Go with free-air (infinite baffle) or acoustic suspension (small sealed). One or the other. But no combination or mixing your schemes.

    The JL Audio 10w3v4-2 is not a free-air sub and should not be used in your floor. Its just for enclosures whether sealed or bass-reflex. The appropriate JL sub is the M10IB5-SG-TB and its only avaiable in 4-ohms.

    If you are 'free-air' it means an infinite and unobstructed volume of air (the entire bilge for example). A free-air 10-inch sub usually requires a 3 cu. ft. enclosure or larger so that the woofer's 'Q' is unchanged which is the basic qualifier for free air. You cannot have too large of an enclosure. However, it should be sealed or isolated front to rear by a 1/8 wavelength 'to' and 1/8 wavelength 'from' the nearest large opening, for a total round-the-world path equal to a 1/4 wavelength of the lowest frequency you're expecting to reproduce, which would be approaching the woofer's free-air resonsance. And the resonance is higher on a free-air driver. From this you can deduce that a.) the hole in the top of the starboard hump must be sealed and b.) the hole in the port hump or other distant openings do not matter.

    In contrast, if you go sealed then it should be at or close to the optimum displacement (averages .65 internal net on most 10-inch drivers) and that means absolutely air tight in the strictest interpretation.

    David
    Earmark Marine
    ^^^X2^^^

    Well put David!!!

    Phil
    Kicker

  7. #17
    Join Date
    May 2009
    Location
    Dallas, TX
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    880

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    jmvotto,

    We're happy to ship anywhere in the states.

    As for the music in the video, I had to ask someone. I'm more of the technical and application spokesman.

    I believe the artist is 'Akon', the album is 'freedom' and the song is 'keep you much longer'.

    David
    Earmark Marine

  8. #18
    Join Date
    Jul 2008
    Location
    Des Moines, IA
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    I really don't think you'll be happy with a free air sub. In my opinion free air subs are throwing good money after bad. If you're going to upgrade, I'd recommend either 1.) a small sealed enclosure and put it on the other side (or on top of) of the drivers footwell (simplest option) or 2.) cutting out some of the front of the footwell and inserting a sealed enclosure with a larger front panel that covers the face of the existing footwell. (harder to do, and even harder to describe, ill see if i can put together a quick diagram.) Again, this is just my opinion as I've yet to hear a free air sub that would make me happy.

  9. #19
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    Dec 2006
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    Tigard, Oregon
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    So it appears that even if I decide to go "free air" I still have to seal up two of the three holes in the footbox - the one on top and the one under/in front of the woofer than leads to the pipe/cable chase under the floor of the boat. And I have to invest in a free air subwoofer.

    So I got to thinking about pre-fabbed sealed enclosures and ran across an ad in the local craigslist for the sealed enclosure below, brand new, for $20. Apparently, he bought a stock of them at a closeout somewhere. I checked the dimensions and it will fit just fine under the dash - I can just screw it directly to the face of the footbox. It's not too deep so it won't take up a lot of the room down there. I know that it's not water proof but this is more of an experiment, to see how my sub would sound in a sealed enclosure and I'm only spending $20. The dimensions are stated as 20.25"W x 13.88"H x 5.88"D but I don't know if that is interior or exterior. If interior, then the interior volume is 0.96CF which is 50% more than the recommended volume of 0.66CF for my sub. I supposed I can just screw in a few lenghts of 2x4 inside the box to get to the desired volume. BTW, does the recommended volume of 0.66CF include the volume displaced by the sub or not?

    So Phil and David, do you think this enclosure would work okay with my sub? Is the shallow rectangular shape a concern vs a square box shape? Should I reduce it's volume a bit or just try it as is? My sub has a top mount depth of 5-1/2" so it should fit depth wise.

    If it turns out that the sub sounds worlds better in a sealed enclosure, then I may have to build a custom one after all.

    Thanks,

    Al


    Al

    2006 Mobius LSV

  10. #20
    Join Date
    Jul 2008
    Location
    Des Moines, IA
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    Top mount depth for your sub is 5 3/4", and I'd bet the stated box dimensions are external measurements. So if it fits it will be very very close. Ideally you'd have an inch or more behind the magnet, so I'd keep looking. Also the recommended sealed box volume of .66 does not include the sub displacement. Good luck, I think you'll be amazed by the sealed box improvement over factory.

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