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  1. #21
    Join Date
    Nov 2009
    Location
    Stillwater, Oklahoma
    Posts
    309

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    I would assume that those are external dinemsions.

    We can assume it is likely built from 5/8ths material, or 3/4 material. At the dimensions provided, and assuming a perfect rectangular enclosure, that gives us a gross interior volume of somewhere between .59 and .61 cubic feet.

    Then, as you notice the baffle and the two sides, (vinyl covered) are inset, and it sort of appears that there is an angle to the enclosure; i.e. the top is shallower than the bottom. The scalloping in the inside back of the enclosure further points to the probability that this is an engled box. Both these points tell me that the enclosure might be as small as .5 cubic feet, maybe smaller. In my opinion, that is really too small for what you are looking to do.

    Another thing to point out. The scalloping on the inside back of the enclosure is there to provide extra mounting depth. If your subwoofer is deeper than the enclosure is, it will not fit.

    One more thing. 10-inch woofers are the worst of the group, (amongst 8's, 10's, 12's, and 15's) at having a very wide range of cutout dialeters. A 10" woofer can have a cutout diameter as small as 8-3/4 up to 9-1/8th as I recall from my history as a design engineer designing enclosures for other major brands. The enclosure you are looking at is probably a compromise in terms of its hole cutout. Make absolutely sure you center the woofer perfectly in the hole, or you will find some screws do not bite and/or you end up with leaks.

    You are only talking 20 bucks, so it is a cheap experiment, but $20.00 would go a long way towards buying material to build something that is exactly right for your woofer.

    If you can, take the time to find out if your woofer will fit prior to handing over the money.

    Phil
    Kicker

  2. #22
    Join Date
    May 2009
    Location
    Dallas, TX
    Posts
    880

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    cab,

    An automotive box probably won't last through the first season in a boat. The seams quickly fail although the vinyl and carpet coverings tend to conceal the failure for an additional season or two. There's no point in going with a sealed enclosure thats not sealed.

    Even if the woofer would fit depth wise, you need an additional inch of clearance for the vented pole piece to breath. Otherwise, you're introducing noise.

    My advice is to get past the fact that the box is so cheap and do it once the correct way and be finished with it.

    David
    Earmark Marine

  3. #23
    Join Date
    Apr 2007
    Location
    Las Vegas, Nevada
    Posts
    1,582

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    Cab
    I used this sub enclosure for my 10" Boston Acustic G3 Sub. I bought it at www.audioformz.com. It fits just on the other side of the foot rest on the driver side. I used a little poly cotton to fill the cavity. The bass is amazing. I also have the Kicker MX700.5 amp and could not be happier with the sound. I did set my freq. to 100 hz. Check uout my pictures of the install.

    Tazz

    Tazz 07' Moomba LSV --Kicker Marine Amps (MX700.5 & MX350.4) 6 polk DB651 speakers, 4 MB Quartz Marine Speakers, 10" Boston Acoustic Sub, Z-5 Cargo Rack, Custom Speaker/Light Bar, modified ballast system, Custom LED Rings
    Live life to the extreme and no less!!

  4. #24
    Join Date
    Dec 2006
    Location
    Tigard, Oregon
    Posts
    3,016

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    Quote Originally Posted by tazz3069 View Post
    Cab
    I used this sub enclosure for my 10" Boston Acustic G3 Sub. I bought it at www.audioformz.com. It fits just on the other side of the foot rest on the driver side. I used a little poly cotton to fill the cavity. The bass is amazing. I also have the Kicker MX700.5 amp and could not be happier with the sound. I did set my freq. to 100 hz. Check uout my pictures of the install.

    Tazz

    tazz,

    Those are some spendy enclosures. I'd rather build a custom one. Do you have the dual or single voice coil G3 (are you running it at 2 ohm or 4)?

    Thanks,

    Al
    Al

    2006 Mobius LSV

  5. #25
    Join Date
    Apr 2008
    Location
    California
    Posts
    2,840

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    Al, a sub does not need lots of space behind it, it's the volume that's what counts. Also all subs have a range to work within, example a lot will recommend .75cf but work just fine in the range of .60-1.0cf. Displacement is never given as all are different so i'm guessing around .80 or less displaced with the MoMo which is just fine. The .66cf is Polks optimum, but in a boat you'll never notice it. Well let's put it this way, 500% better than free air!

    If you don't want to make a custom box then you can use this one with precations taken to protect it. Need more back space? Look at the box, it has a lip running around it that looks to around 3/4". I would "glue & screw" a 3/4" face to it of plywood or mdf. That gives you more back space behind the magnet. Coat the box with two layers of resin for waterproofing and add small rubber feet to the bottom for support.

    The shape of the box is fine, in fact the more obtuse angles the better as i understand it. A perfect square box supposedly reflects the sound waves back on themselves cancelling some out.

    Make a facia board out of hardboard or plexi running across the whole area like Newty did, carpet it and use velcro to hold it to the box face hiding all but the sub. It will also give you a surface to extend your heater outlet to.

    My two cents
    Last edited by Razzman; 01-11-2010 at 10:35 AM.
    2007 Mobius LSV

  6. #26
    Join Date
    Apr 2008
    Location
    California
    Posts
    2,840

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    Btw and no offense to our pros! My brother in law has an automotive box in his boat which we resin coated real good inside and out. He almost sank the boat back in July with water 1' deep in the boat. The box survived believe it or not and is still in use!
    2007 Mobius LSV

  7. #27
    Join Date
    Dec 2006
    Location
    Tigard, Oregon
    Posts
    3,016

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    All,

    Thanks for all your posts. I decided not to get the box pictured but instead, bought a similarly shaped box (rectangular but deeper at the bottom than at the top) but is deeper and not as wide. I bought it from the same guy for cheap - it's used but in great shape and well made. It's currently got a 4" port on the side but I am removing that and making it a sealed enclosure. I will also seal it really well inside with silicone sealant at all the seams. There is at least 1" of air space between the the magnet and the back of the box and the opening is perfectly sized so that all 8 mounting screws bite solidly into the mdf (for a good, tight seal).

    The gross volume of the box is 0.87CF. Polk says to deduct 0.10CF for the volume displaced by the sub so I'm at 0.77CF vs the 0.66CF recommended for this sub. It's easy enough for me to glue and screw a couple of measured pieces of 2x4's inside the box to get right at 0.66CF - should I do this or is 0.77CF just fine?

    I am going to mount this box upside down and screw it to the face of the footbox to minimize the room it takes up. If this ends up sounding good, I will at some point build a custom box, one that is properly coated against the elements but I will probably go with a 2 ohm 12" sub.

    I'll let you know how it sounds once I get it done and will post up some pics.

    Thanks,

    Al
    Al

    2006 Mobius LSV

  8. #28
    Join Date
    Nov 2009
    Location
    Stillwater, Oklahoma
    Posts
    309

    Default

    .77 cu ft should be okay for you. That is within 20% of recommended volume. It will play a tiny bit lower, although you probably will not hear it, and the total Q will be slightly lower than in the .66 box, but again, you will not be able to notice it.

    When you go to build the custom box, consider a void-free 3/4" 13-ply plywood instead of any material manufactured from dust and resin, i.e. do not use MDF or particle board.

    The acoustic benefits that are real for MDF are more for the higher frequency midrange and "tweeter" frequencies found in full-range home cabinets. This is due to two things. MDF is a very damped material, i.e. it doesn't "ring" like other wood materials. Additionally, its damping and resonance are uniform from board to board, and therefore the use of MDF in home cabinets results in repeatable predictable results when compared with hard woods or other solid materials, which can have varying densities and resonances.

    The wavelengths associated with subwoofer enclosures are too long to develop any standing waves or resonances that can be attributed to the material alone, so a high-quality plywood is fine acoustically. It has the added benefit of being dimensionally stable with varying humidity levels.

    No matter how well you coat an MDF enclosure, (Sorry Razz) it will eventally be compromised somehow. The "crack in the armor" will allow water to get in, and the MDF material will swell. From here it is a downhill battle as the swelling will cause more cracking of whatever protective coating you put on, and more cracking will cause more moisture intrusion.... It is a vicious cycle once it has begun. I restore wooden boats occasionally as a hobby and can attest to the good behavior plywood can have under water. You will never catch me using MDF in a boat for anything.

    Finally, car audio companies use MDF for their subwoofers because it is cheap, it is easily milled, and it is a material that "folks around speakers" have been familiar with for a very long time. To me those are not good reasons to use it in a boat.

    Keep us posted!

    Phil
    Kicker
    Last edited by philwsailz; 01-11-2010 at 04:41 PM.

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