Stereo Autopsy part 1....

[KG's Supra24]

Bam



HA! He can provide much more help than myself.

[wotan2525]

Dang!! Those drawings are AWESOME. I've got a prebuilt 2x12" ported enclosure that I had to remove the helm and drivers seat to get in. Super big pain in the ass. It moves around and it takes up ALL of the foot-room. If I ever get a "new" boat, I'll be doing it this way.

[Salty87]

you guys have this covered very well...all i have to add is that you can get a grill for pretty cheap to protect the woofer. fingers could still get through but no feet or anything wider than an inch or so. i have something similar to this, less than $10 at amazon...

[dusty2221]

End result

[pctarmor]

Great info, thanks a ton. Is yours ported on the lower right side to the rear? The WS sub is supposed to be at 1.4cuft (net) with a 3" round double ended flared port tuned to
around 29hz-36hz according to the WS rep.

[KG's Supra24]

Ours are sealed. Ported is going to get more difficult, both with size and construction.

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[dusty2221]

No, mine is just a sealed box. I'm not near technical enough to understand all that is behind a proper set up a ported box. 2 guys that could give you excellent advice that frequent this forum are David from Earmark Marine and another guy that goes by the user name of Wylietunes.

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[Wylietunes]

The tuned frequency of the ported enclosure is determined by the port's opening and length, along with the enclosures volume. Every sub has an ideal tuning frequency, which is mostly driven by the subs T/S parameters. One can tune above or below the ideal Hz for personal preference though.

For the XS-12, its ideal is 25Hz. When I build a ported enclosure, I construct the port as part of the actual enclosure, rather then use a round port assembly with sectional lengths. In this case, the space consumed my the port structure, needs to be subtracted from the gross volume of the enclosure, leaving the net. This is why a ported enclosure is more work then a simple sealed. Adjusting the volume of the box, effects the tuning Hz, readjusting the port length and it effects the net volume for the woofer, etc, etc, etc. All of this, while trying to work within a given space of a particular shape.

Now, something I learned today, about the new HT-1 amp. It does not have an adjustable sub-sonic (or infrasonic) filter. It has an internal fixed sub-sonic, and im awaiting confirmation as to what its set to. In an ideal ported enclosure setup, you will want to set the amp's subsonic filter to just below the enclosures tuned frequency. The set the floor so we are not reproducing notes below that set point. Simon @ Wet Sounds and I are putting our heads together on whats the best course of action with this particular pairing. I'll update when I have more. A sealed enclosure my be the ideal enclosure in this particular situation, which would greatly simplify the DIY install.

[EarmarkMarine]

Here's a bit of info. Hope this helps. In establishing what enclosure will fit, consider that most air suspension 12" subs with a relatively low 'Q' will require a 1.25 net internal displacement after subtracting the woofer volume which translates to about 1.75 cu.ft. external (which should be your starting point).
A bass-reflex (ported) enclosure for the same 12" driver will require a bare minimum of a 2.75 cu.ft. external displacement. That's approaching a 60 percent increase. And, as your box shape becomes more complex those dimensions will slightly increase. You really can't manipulate the bass-reflex alignment too far away from this base minimum model, despite what a computer box program may say, because it just won't sound very good.
So if you can get that 2.75 and you are satisfied with the remaining leg/foot room then you're golden.
Additionally, no matter what you coat or seal your enclosure with, you have to elevate it off the soul so that it won't wick up the moisture and provides for drainage and evaporation. Besides, who wants to create mold & mildew trap by placing an enclosure on top of the carpeted sole.
Never, ever, use a pre-built automotive box in a boat, especially the ones using the cheaper MDF from China. The seams will fail during the first season although the carpet wrap may conceal the damage for several years.
Those are a few of the basics. It's all done now except for the hard work.

David
Earmark Marine

[EarmarkMarine]

Pertaining to the subsonic filter conversation....
If you have a low Fs woofer to begin with and you tune the bass-reflex enclosure 'just' above the Fs, then there really isn't enough program material at sufficient amplitude down in that region to compromise the subwoofer. Leave any bass boast off and keep the lowpass crossover at least 1.5 octaves above the sub/enclosure tuning frequency. Easy does it on the artificial synthesized bass.
You will be fine. The problem really comes into play when someone tunes the bass-reflex sub/enclosure much higher for pure SPL and leaves the sub driver especially vulnerable below the well-damped tuning frequency.

David
Earmark Marine