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Go Back   WakeWorld > >> Boats, Accessories & Tow Vehicles Archive > Archive through May 29, 2009

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Old    Charlie (biggc1)      Join Date: May 2009       05-02-2009, 4:10 PM Reply   
I have 2 12" L7 that I want to put under the console but the area is only about 22" wide. If I did subs down port facing out toward driver would this work good?

I know in some cars subs up port back works real well.
Old    Mike (calvolson)      Join Date: Mar 2009       05-03-2009, 9:49 AM Reply   
Give us a little more info on what you're thinking. My unimaginative brain is having a hard time visualizing what you are describing.
There are a lot of different sub box configurations that work very well.
Old    Charlie (biggc1)      Join Date: May 2009       05-03-2009, 10:16 AM Reply   
Here is a crude drawing. The outside line is basically the space underneath the console area.


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Old    Scott (snafu077)      Join Date: Nov 2008       05-03-2009, 10:33 AM Reply   
Do you have the right amount of air space under the wheel for two vented subs? I can only fit one vented 12 most of the time? You can down fire the woffer just leave about 3-4" off the ground for loading.

Another thought is to fire the sub to the right and put the port on the left. both ways well work just fine.
Old    Mike (calvolson)      Join Date: Mar 2009       05-03-2009, 10:37 AM Reply   
That will work fine just make sure you can keep in spec with the cubic ft volume requirements for those badboys. In case you didn't know a port isn't simply a hole in the box. It needs length to it. The volume of the port is also a factor when tuning a box/sub, just as the overall volume of the box. Like the vent on these ones http://www.wakeworld.com/MB/Discus/messages/3183/689999.html?1241242600 Really long vent on those guys. Biggest concern with yours is if you have enough space.
Old    Scott (snafu077)      Join Date: Nov 2008       05-03-2009, 10:42 AM Reply   
Not sure the boat you have but you well need over 4 cu ft plus port displacement if you want to do both L7.
Old    Charlie (biggc1)      Join Date: May 2009       05-03-2009, 11:21 AM Reply   
I haven't calculated port volume or length yet but I have about 7.5 cubes to work with and the port can be up to 30" deep.

After sub and port displacement I think I will have enough for 2 but I wanted to hear some opinions on weather the box design would work before I did some more calculations. What is a good tuning frequency for a boat?

It is an older boat, 86 Supra Sunsport.
Old    882001 (882001)      Join Date: Nov 2003       05-03-2009, 12:19 PM Reply   
I ported my L5 @ 32/33 sounds awsome
Old    Charlie (biggc1)      Join Date: May 2009       05-03-2009, 1:12 PM Reply   
If yours is a 12 do you know what your volume is?
Old    882001 (882001)      Join Date: Nov 2003       05-03-2009, 2:29 PM Reply   
2.57 cf
Old    882001 (882001)      Join Date: Nov 2003       05-03-2009, 3:07 PM Reply   
http://www.reaudio.com/speaker_box/LPort_Box_Calc.html
Old    Earmark Marine (david_e_m)      Join Date: Jul 2008       05-04-2009, 10:39 AM Reply   
Charlie,

A 3/4-inch gap off the deck won't cut it. That will change the driver's 'Q', accelerate the air speed and choke down the woofer's output. If the downfiring woofer exhausts in an omnidirectional pattern then you can get by with a little less than would be necessary when forcing the woofer's output through a confined and directional path. I would elevate the surround of a 12-inch woofer 2 1/2-inches off the sole. Make sure that you maintain a woofer exhaust path that is no less than the collective surface area of both drivers.

Since you don't have the width to position the woofers side-by-side I'm assuming that one woofer would be mounted behind the other. This means that the rear-mounted woofer is more loaded than the front woofer which is bad when both share the same enclosure. The forces exerted on the two woofers are different not to mention the different force applied to the enclosure internal air mass. Also, the rear woofer would serve to load the front woofer via the exhaust path.

You might narrow the enclosure width in order to side fire both woofers to opposite sides with a 2 1/2-inch minimum gap per each side. This provides a more symmetrical loading and places both drivers in identical distance, phase and pressure in respect to the port.

When you place two drivers and a port within a helm console structure you're loading into a more rigid air mass versus open air. This will mis-align the bass reflex tuning somewhat and may raise the tuning frequency. I would add 5 to 10% port length to offset this. While tuning a bit higher can be advantageous for more output in a boat, I'm more concerned with the unloading effect below the tuning frequency. Along these same lines I would definitely add a 30Hz subsonic filter to protect your woofers in this type of loading scenario. Versus a car, you shouldn't detect an audible difference in a towboat but its cheap insurance for any bass-reflex system.
Old    Charlie (biggc1)      Join Date: May 2009       05-04-2009, 11:05 AM Reply   
WOW! Hmmmm I am not sure what to do now. Would it be better to just use 1 sub.
Old    Earmark Marine (david_e_m)      Join Date: Jul 2008       05-04-2009, 12:12 PM Reply   
Charlie,

Two subs would be awesome if you've got enough displacement. Ported requires considerably more than sealed.

Phil with Kicker can tell you precisely what frequency to tune your subs, the total displacement and port size.

Weigh all your options once you know what sealed and ported volumes are. Add in the volume of the materials and port volume and see what kind of excess space is available. Your boat should dictate one or two subs, sealed or ported.

David
Earmark Marine

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