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Old    Timmy! (timmyb)      Join Date: Apr 2007       02-16-2014, 6:05 PM Reply   
My buddy just picked up an '07 X45 and we are getting ready to build a box for his JL 12W7. We were thinking of putting it behind the drivers seat and removing the factory 10" JL and just leaving the grille on to vent the sound out. Does anyone have pics of their X45 sub installs? I found a couple of TeamTalk but not any W7's specifically. Is that factory 10" opening going to be enough of an opening or are we going to need to cut in another vent?
Old    156452 (WLF)      Join Date: Mar 2010       02-17-2014, 8:46 AM Reply   
My friend has a X45 and he actually put the sub box in the back passenger side locker and left the 10" from the factory hooked up. If it fits, I think that would be a great idea to do what you are talking about...I think the box built to JL specs they provide will be about 2" too tall, so if your buddy is willing to cut up the opening to allow it to just drop it, it would just fit under the seat.

As a side note, I have a 13W7 under the observer seat. It is definitely not optimal, but with a smaller boat (XStar) it was really my only option I had that wouldn't interfere with ballast bags.
Old    David (DavidAnalog)      Join Date: Sep 2013       02-17-2014, 9:48 AM Reply   
Quote:
Originally Posted by timmyb View Post
My buddy just picked up an '07 X45 and we are getting ready to build a box for his JL 12W7. We were thinking of putting it behind the drivers seat and removing the factory 10" JL and just leaving the grille on to vent the sound out. Does anyone have pics of their X45 sub installs? I found a couple of TeamTalk but not any W7's specifically. Is that factory 10" opening going to be enough of an opening or are we going to need to cut in another vent?
In a perfect acoustic world the subwoofer/enclosure baffle would be sealed airtight to the existing opening via a VERY shallow manifold. That way the woofer output would be direct-radiating and not into the seat console. Thus, you would avoid any losses. Also, if the existing opening was the same suface area of the woofer's Sd, then you wouldn't lose anything. The deeper the manifold the greater the loss and the greater the unwanted impact on the woofer's response.
Now, if the sub/enclosure rests in the seating console and plays freely into the air space within, then the dynamics change quite a bit. That air space, including the adjoining gunnel cavities, is huge. Therefore, that air space is very compliant. As a result, the vent as a ratio looks small in comparison, represents resistance, and there is little impetus for the bass radiation to flow through the vent. More of the radiation is lost into the console and gunnel than is funneled through the exterior vent. The expansive interior air space stores and releases energy which is delayed in time. Think of an echo....not long enough to be heard as an echo but long enough so that the direct radiation of the woofer and reflected radiation from the interior space is seriously out of phase. This acts to filter certain frequencies more than others, creates output losses making the sub and sub amp work harder to create the same output, and generally smears the bass tonal construction. You end up with a lot of boat shaking and tactile bass but less in the way of bass pitch accuracy and much less upper/transient/attacking bass. This bumpy response also makes it difficult to coherently and seamlessly splice the sub with the satellites.
Having explained the reality of this type of set up I also have to say that some boats give you little to no other option. So you are forced to take what the boat gives you. In that case you should expand the vent as large as possible. Usually you can elongate the vent horizontally and make a custom vent. It looks better and the boat doesn't look like swiss cheese.
Do not take polarity for granted. Experiement.
Old    Hate N Pain (hatepain)      Join Date: Aug 2006       02-17-2014, 10:05 AM Reply   
Here is a thread by Ben from Acme Tops and Tunes with some pics.

http://www.wakeworld.com/forum/showthread.php?p=1554637
Old    David (DavidAnalog)      Join Date: Sep 2013       02-17-2014, 10:23 AM Reply   
Ben's project is a great design example.
It appears that the front output of those two subs are sealed to the vent opening via a custom chamber (manifold). So they are benefiting from all of the subs output with very little loss. You want to avoid creating a clumsy bandpass so you want a small as possible front chamber/manifold and a large as possible vent.
Old    Timmy! (timmyb)      Join Date: Apr 2007       02-17-2014, 11:05 AM Reply   
So what you are saying, David, is that IF we seal the rest of the compartment off from the box and create an opening equal to the surface area of the woofer (and vent?) that we would be ok? I guess I would need to take the air space that is between the front of the woofer and the vent into consideration as well. The location we are looking at makes this pretty doable.

I saw that install with the Boston's, that's a little more extreme than what we were looking to do as we didn't want to relocate the electronics that are under the helm or it would be a slam dunk to put the box under there.
Old    David (DavidAnalog)      Join Date: Sep 2013       02-17-2014, 11:33 AM Reply   
[QUOTE=timmyb;1865126]So what you are saying, David, is that IF we seal the rest of the compartment off from the box and create an opening equal to the surface area of the woofer (and vent?) that we would be ok? I guess I would need to take the air space that is between the front of the woofer and the vent into consideration as well. The location we are looking at makes this pretty doable.

You can increase the size of the baffle side of the enclosure, creating a flange around the perimeter, in order to have a greater surface area to seal up against the backside of the console wall. Or, you can build a shallow connecting pan or manifold. One way or another, the woofer has to be either recessed into an extra deep baffle or set back with a pan/manifold so that the high roll surround and longer excursion have no chance of contacting the grill/vent.
Since the port mouth would be somewhat exposed, it would be a good idea to locate the port high and angle the port up slightly to retard water from entering the enclosure. Or two round PVC ports at the bottom and on each side of the woofer with elbows inside so water cannot enter. You can also angle the bottom of the manifold and/or drill a number of small drain holes in the bottom of the pan/manifold.
Look at the very shallow pan/manifold on the MasterCraft in the Earmark Marine gallery. Take that principle and Ben's design and find a version that works in your situation.

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