Sub Placement

[EchelonMike]

Hey Crew,

I am getting ready to clean up my boat stereo set-up. The previous owner mounted a 4ch Sony 600w amp under the dash, and has it powered by the power distribution block under the dash. From what I have read here, that is less than ideal.

At the same time I am going to install my sub that has been on my garage shelf for the past few years. It is a Kicker 10" solo baric in a Kicker ported enclosure. I just bought a Kicker 500.1 amp to power it. My plan is to install both amps next to the batteries under the rear facing observers seat, with proper power feeds, and re-run the RCAs and speaker wires.

Is this location ok for a sub? My boat is an XTI so my other option is to mount it all in the huge storage locker next to the engine. But that storage sees a lot more moisture Than the observer seat area, and would require a longer run to get the amps fed from the battery.

Thoughts/suggestions before I start? Since I am adding a sub I will have follow-up questions regarding setting all the crossovers...if there are starting point recommendations for that, feel free to give me a baseline. The boat has 6 in boat speakers - all 6.5" infinitys. The tower has one pair of 6.5" kicker two ways. All 8 are powered by the Sony 4ch amp @ 2ohm load.

Thanks, Crew!

-- Mike

[David]

Mike,

The port side observer's locker is definitely the best location for the amplifiers. It keeps the primary power cables very short and there is plenty of space against the hull surface and forward against the bow mold. Easy to install, tune and diagnose if needed. Yes, there is some moisture in there. Keep the bilge as empty as possible. If you see condensation, especially when undercover, there are a number of steps you can take to minimize this.

Acoustically, mounting the sub/enclosure underneath the driver's dash is best by a country mile. This is your best shot at direct radiation. Every other option, namely in storage lockers, will be a compromise in output (working your sub and sub amplifier much harder) plus a major compromise in bass sound quality (little to no midbass transients and very poor tonal construction). The rear storage compartment next to the engine is about the worst place to locate a subwoofer.

[robtr8]

I apologize if I'm taking this too literally but when you say "under" the observes seat I hope what you actually mean is "behind" the observers seat in the storage compartment. Look up "amp rack" in this forum for ideas. There is also a ton of good info by David and others on correctly wiring the amps. Just need to dig a little.

If your Kicker is an L5, I can email you my PWK Designs box plan that will fit under the dash (probably, fits under mine). The existing Kicker box is probably too long and is made out of MDF which won't like the marine environment over the long term.

Oops, my bad, you have a 10". Never mind.

Edited September 26, 2013 by robtr8

[tccombs]

Mike,

The port side observer's locker is definitely the best location for the amplifiers. It keeps the primary power cables very short and there is plenty of space against the hull surface and forward against the bow mold. Easy to install, tune and diagnose if needed. Yes, there is some moisture in there. Keep the bilge as empty as possible. If you see condensation, especially when undercover, there are a number of steps you can take to minimize this.

Acoustically, mounting the sub/enclosure underneath the driver's dash is best by a country mile. This is your best shot at direct radiation. Every other option, namely in storage lockers, will be a compromise in output (working your sub and sub amplifier much harder) plus a major compromise in bass sound quality (little to no midbass transients and very poor tonal construction). The rear storage compartment next to the engine is about the worst place to locate a subwoofer.

David, mine is under the drivers side dash and pointed towards the driver.. But i have heard that pointing it down or towards the Hull might be better. Your thoughts?

[David]

David, mine is under the drivers side dash and pointed towards the driver.. But i have heard that pointing it down or towards the Hull might be better. Your thoughts?

tc,

It's a trade-off with subtle pros and cons for both approaches. Here are some general principles to follow.

Direct radiating, unobstructed and pointing at your knees, gives you the best midbass attack and your best chance of having a coherent phase response with your coaxials.

Aiming at the hull (sidefiring) adds the benefit of extra loading from the reinforcing planes, which consist of the boundaries created by the under helm cavity. Every boundary (against wall, floor, corner of two walls, corner of three surfaces) each adds +3 dB of output. But the plane dimensions of the under helm cavity are not extented so this nets you a rock solid 3 dB increase in output at the lower registers. Not bad since that is the equivalent of doubling your amplifier power with double the woofer excursion. That's an easy gain just for rotating your woofer orientation. However, the caveat is that the volume (space) of the under helm cavity stores, delays and releases energy resulting in a little compression/filtering of the upper midbass transients and introduces a little phase rotation.

Sidefiring is a great trade-off for a sealed 10", sealed 12" or bass-reflex 10". You want a great deal of distance between the output of the woofer & port and the adjacent surface, which is the hull. A minimum of 5" for a 10 and a minimum of 6" for a 12. Add at least 50% more clearance for bass-reflex. Plus, you must make sure that there is plenty of surface area around and over the top of the cover facade. But a bass-reflex 12" requires enough surface area as a matter of fitment, that it needs to be direct-radiating. A bass-reflex 12" is also robust enough that you really don't need the extra loading. So with all things considered, I recommend sidefiring for anything less than a bass-reflex 12-inch sub. Btw, you always want to load both the port and woofer in the same direction on the same side of the enclosure in this particular application.

Downfiring is typically sealed. Yes, you can take advantage of boundary loading and the expansive sole but if the woofer is too close to the sole, you reduce the radiating surface area along the path and actually reduce some of the gains that downloading would offer. A open field environment is very different from the enclosed & sealed cabin of a vehicle, which is extremely forgiving. No forgiveness in open air. The rule for an average excursion downfiring woofer would be for it to be elevated 2.625" from the peak of the surround to the sole for a 10-inch sub, and 3.125" of clearance from the peak of the surround to the sole for a 12-inch sub.

[tccombs]

WOW I'm not worthy...

Clearly you are an expert... Thank man that was way more infor than i ever expected. (still working on processing it all )

Maybe i should just drive my boat to your shop or house are in in Norcal by chance?

[David]

tc,

Dallas, Texas.

I used to be in the mobile electronics industry.

If you need installation you shouldn't have any trouble finding someone in your area. Once you make a decision on the approach, then it's not difficult to do any of these options.

If you get hung up on any of the concepts, just ask and I'll give that issue a more in depth explanation.

[EchelonMike]

Thanks, everyone, for the good info. Wonder if i could pull the sub and xover out of the stock kicker box and build one to fit under my dash. Do most go with a sealed box or a ported box?

[David]

Thanks, everyone, for the good info. Wonder if i could pull the sub and xover out of the stock kicker box and build one to fit under my dash. Do most go with a sealed box or a ported box?

There is normally no passive crossover in a stand alone sub enclosure.

Generally ported gives you more output in the most active part of the bass plus provides deeper bass extension before abrubtly rolling off. You can make ported sound like a one note SPL monster or have a well-damped, broad and smooth SQ response. Usually the packaged sub/enclosures are biased a little more for SPL. But a ported enclosure, as a tuned resonator, gets far more complex with more room for error. Sealed is much smaller, easier and predictable. But sealed is still a tuned circuit so you must have the ideal internal gross displacement. For a balanced sounding sealed enclosure, most shoot for a final system 'Q' (Qtc) of around 0.8. All this information is available from the manufacturer, Kicker. Your particular woofer really likes and goes deep in a small, sealed enclosure. However, since you are already used to the higher output of ported you might be dissappointed if you don't stay with that. You certainly can re-create your existing enclosure in another shape. You'll have to pay close attention to exterior wall and port wall thicknesses in the conversion. Every detail is important. A reasonable change in the enclosure shape shouldn't impact the sound.

[MLA]

Thanks, everyone, for the good info. Wonder if i could pull the sub and xover out of the stock kicker box and build one to fit under my dash. Do most go with a sealed box or a ported box?

Why not exchange the loaded enclosure for just the raw sub driver? That manufacturer offers almost all of their subs by themselves.

[EchelonMike]

Why not exchange the loaded enclosure for just the raw sub driver? That manufacturer offers almost all of their subs by themselves.

Just because I have it sitting on my shelf...but your approach is probably the better way to go.

Has anyone looked at an already-built enclosure that will sit nicely under the helm? Something like a Polk db 1212? I haven't measured but it is only about 18" wide and would sit there nicely. Put some small spikes on it to elevate it an inch off the carpet to keep moisture out from direct contact.

-- Mike

[MLA]

Just because I have it sitting on my shelf...but your approach is probably the better way to go.

Has anyone looked at an already-built enclosure that will sit nicely under the helm? Something like a Polk db 1212? I haven't measured but it is only about 18" wide and would sit there nicely. Put some small spikes on it to elevate it an inch off the carpet to keep moisture out from direct contact.

-- Mike

The db1212 loaded enclosure looks to be carpet covered MDF, same as you already have with the loaded Kicker sub enclosure.

[David]

Most pre-fabbed enclosures are made from three total pieces of water soluable MDF. The front, back, top and bottom are one piece that has a series of five V-cuts and two dado cuts. All wood is pre-carpeted before CNC cutting and assembly. The large piece (front/rear/top/bottom) is glued and folded around the two side pieces. Rarely is there a nail, staple or screw used in the construction. The seams fail quickly in a boat but the carpet covering may conceal the failure for several years. So regardless of which woofer you use, a boat deserves a marinized enclosure.