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81SNS
01-31-2012, 10:18 AM
I am down to installing a subwoofer, does anyone have any pro's or con's in a boat application? I think I can squeeze a 10" in under the dash, and a sealed box will take up less room, but I didnt know if it would be worth the extra room for a ported?

EarmarkMarine
01-31-2012, 12:36 PM
81,
Most contemporary woofers have parameters that are suitable for either sealed (air or acoustic suspension) or ported (bass-reflex) enclosures.
On the average a 10-inch woofer would require a sealed enclosure with 'external' dimensions of 12"x12"x12".
On average a 10-inch woofer would require a bass-reflex enclosure with 'external' dimensions of 16"x16"x16".
The bass-reflex version would deliver 3 dB extra output over the bottom octave of usable bass and have bass extension that reaches 9 Hz lower before the half power point. The extra deep bass extension before roll-off is very audible and the extra 3 dB of output is equivalent to doubling your amplifier power. So bass-reflex has alot of extra acoustic leverage.
Using a well designed bass-reflex alignment that is well damped and linear (versus a one-note resonator for the sole purpose of maximum peak output) will essentially sound equal in sound quality to the right sealed design. But in the context of an open boat environment the best sounding subwoofer is the one where its limits and the amplifier limits are not exposed. This is usually going to be the more responsive bass-reflex system.

David
Earmark Marine

agarabaghi
01-31-2012, 12:44 PM
What he said. I went through a lot of boxes and setups and so far the single ported 10" sub sounds the best.

81SNS
01-31-2012, 01:59 PM
OK one more thing, as I understand it, the sound coming from the sub isnt "directional" so if I put it under the dash firing toward the drivers feet basically would this be ok, or should I try and mount it higher up under the dash and have the sub firing at the floor?

agarabaghi
01-31-2012, 02:43 PM
staging makes a pretty big difference in boats, you will have to talk to someone with the same boat, or just try different positions.

EarmarkMarine
01-31-2012, 03:36 PM
81,
Correct, the longer waveforms of the lowest frequencies are non-directional. At the very top of a subwoofer's range and were it overlaps with the in-boat coaxials you will sense some slight directionality in the attack or the transients. What is far more impactful within the realm of a subwoofer is the surrounding planes and loading environment whether it is direct radiating into the cockpit or radiating from within a locker, helm console or other compartment. The results are very predictable but it can get to be a very in depth explanation. Here is a couple of short and simple guidelines:
Reducing the woofer's radiating surface area by TOO tight of a downfiring scenario reduces its output.
Mounting the woofer close to surrounding planes will reinforce the bass.
Placing a woofer in the corner or at one extreme of the cockpit will produce more output.
A woofer/enclosure mounted in a large compartment and venting its radiation through a small surface area opening will reduce the output and change the tonal balance of the woofer providing less in the way of articulation.
Subs when heard alone are rather indiscriminant sounding anyway. Much of the pitch accuracy comes from the midbass produced by the in-boat coaxials. Their installation environment and system tuning is equally important if you want bass with sound quality.

David
Earmark Marine

vrsc
01-31-2012, 03:46 PM
David, great info

1redTA
01-31-2012, 04:31 PM
David, what would be your placement and type of a sub for a stars and stripes? Bandpass on the port side under the dash behind the observer seat?

81SNS
01-31-2012, 05:32 PM
David, what would be your placement and type of a sub for a stars and stripes? Bandpass on the port side under the dash behind the observer seat?
1red, I think you and I are thinking on using the same place, putting it in the opening behind the observers seat, I am thinking on putting it there firing at the drivers feet.

Jeff d
01-31-2012, 05:52 PM
Something on the more practical side to think about with the ported vs. sealed debate is moisture. If you're using a non-marine subwoofer you're probably safer with a sealed enclosure to protect the motor of the woofer.

You didn't mention if this was a DIY build or not. A ported enclosures require more precision to build. Dimensions must be exact and cuts must be precise or you can affect the frequency that it's tuned to. So, if you're planning to whip this out with a drill and circular saw I'd build a sealed enclosure. On the other hand if you're experienced with wood working and have access to a table saw, router, etc then you're equipped to build a proper ported enclosure.

EarmarkMarine
01-31-2012, 06:46 PM
Personally I think the execution of any enclosure is equally important. If you have a sealed enclosure with a leak the size of two pin heads the sound of the woofer will immediately change and the woofer mechanical suspension (interior spider and exterior surround) will soon fatique which will lead to a premature speaker failure.
We have a very detailed enclosure building draft for those who are a DIYer. But as mentioned above there is no point to a DIY project unless you have the correct tools.
I like a bandpass enclosure for the right application. A well-damped bandpass can give you a 6 dB increase (equivalent to four times the amplifier power) versus a sealed enclosure with a linear response over a maximum of 1.5 octaves. So it can sound good if designed and executed correctly. But a bandpass is infinitely more complex than a bass-reflex and has earned a reputation as a single-note boom box due to generally poor execution. We only use a select few woofers and a select few proven designs for bandpass enclosures.
I am not familiar with the interior of the 'stars and stripes' model so I can't make a recommendation for what the ideal sub solution might be without a few definitions and dimensions. I can tell you this... we already have charted in advance all the various woofer sizes from 8" to 15" with singles and multiples in a variety of enclosure types so we can predict the performance for any given size of external enclsoure displacement. While cone surface area in an open boat generally rules the largest woofer does not always win.

David
Earmark Marine

David