Sub box placement
 

Im in the process of putting a new sub into the boat. The heater system in my generation sanger is largely mounted on the drivers side, and making a box to suit may be a bit of a nightmare. On the other hand i want to get the most out of the setup as possible.

Just wanting to get some first hand opinions on how much difference there is to be had by having a sub beneath the drivers feet vs in the passenger locker. That would be much more convenient as we dont often have much in there.

Have you guys built with mdf and then used a resin to seal, or gone straight with marine ply?

Cheers
Byron

I would definately make an attempt at getting it to fit under the helm. I had to move my heater all the way to the top of the wall and my box was huge and it fit with a 1/2" to spare. Could you extend the hoses and actually mount the heater to the sub box? In the passenger locker, it would be muffled and you may be better off just going with a free air sub under the helm.... I built my box out of mdf and coated every piece with resin before I put it togeather. You will probably get mixed opinions on that tho. Good luck and post some pics :D

Byron,
If all things are equal then the sub location under the driver's helm is direct radiating and wins by a country mile.
The passenger console can easily attenuate the bass by 5 or 6 dB which means it takes four times the power and four times the excursion to get the same output. The woofer and amplifier operating most conservatively always sounds the best. With a large enough enclosure and larger woofer(s) and enough amplifier power you can engineer enough leverage to overcome the passenger console. But it will always be more of a boat shaker than a musical bass maker. Also, the altered phase response of the bass radiation coming from the passenger console will make it hard to have any degree of coherency with the midbass from the coaxials.
I would prefer a 10" direct radiating from under the driver's side over a 12" concealed in the passenger locker. In the end you will have to take what the boat gives you. Don't place a larger woofer into a mismatched enclosure just to force fit it on the driver's side. If you have to accept the passenger side then venting that compartment with a grill of sorts that has an open surface area at least equal to the woofer's surface area helps a great deal. No one wants to turn their boat into swiss cheese but tiny vents are worthless.
A high grade (absence of voids) exterior birch ply, MDO, or Medex is ideal. All solvent based versus water soluable construction. All should be exterior sealed regardless. Polyester resin is okay. Epoxy resin or professionally applied bed liner is better. MDF will work fine with the proper steps. I place execution as more important than the actual material used. In every case, you must elevate the enclosure up off the sole with polymer or composite risers/pads to allow for drainage and evaporation. Any enclosure will eventually fail if you plant it down directly on the carpet not to mention the mildew and mold trap that is created.

David
Earmark Marine

Thanks for the advice.

Will have a go at remounting the heater and work from there.

By chance does anyone know of any good software for sub box design. I am going to use an old Momo MMC2124DVC sub to start with. It requires a sealed box of.88cu ft. but id rather a ported to help get the most of it while in the boat. Any idea also on size ported box would be appropriate.(it doesnt say)

REaudio.com has a good box builder on it. I'd make sure it won't damage the sub porting the box tho. You'll need to take off the displacement of the port and subwoofer to get your net volume of course.

Byron,
Computer software will allow you to take most any woofer in most any box and tune to a particular frequency. But that doesn't mean it will sound good. Some experience with specific woofers and enclosures helps. For that sub in a bass-reflex start with about 2.75 cu.ft. external displacement. That will help you determine whether that is going to work in your boat. Btw, that sub loves a ported enclosure and .88 net is too small for sealed despite what Polk claims.

David
Earmark Marine

I appreciate the advice David. Glad that you know the sub too. It will do the job until. It's replaced with something nastier. It has 500rms to it btw.

Do you have a dummy plan of a box that I could base mine on, in particular where to mount a port and basic build principles.

Thanks