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IXFE

Rip & replace factory subwoofer + enclosure...

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IXFE
Posted (edited)

Context is everything, so before I get into the project allow me to give some background as I believe it will help folks see how I’ve arrived here...

When the new Malibu/WS system launched in the Fall of 2016 probably the most skepticism surrounded the enclosure.  Many questioned the material selection (3/4” HDPE), construction method (screwed but not glued), and worried about its size and whether or not it would adequately seal. For a trip down memory lane, here’s that link.  The enclosure discussion starts on page 2 (as you’d expect, some of the “specs” given have proven to be wrong now that we have our hands on these systems for a few years, but it’s still a good read)...

I had my first system with this subwoofer in it last year in my 2018 23 LSV. And while I wasn’t particularly impressed with the volume or the sound coming from the sub it seemed adequate and doing anything about it was not a priority for me last year. In short, it was “just okay” for me. However, I had buddies who were not pleased with their copies of the sub, and we started talking about what it would take to make them better... so my wheels started turning.

This year I once again ordered the factory sub for my 2019 25 LSV. You probably wonder why.  My thinking at the time was that I had decent luck with the same sub last year, and I figured this year I could make a few minor improvements to take that factory sub to the next level. Plus I really like the look of the factory billet grill (which looks even better with an LED light mounted behind it), and I didn’t relish the idea of cutting fiberglass under the helm to get my own box in there. 

Earlier this year a thread popped up on the subject titled “Factory Sub Enhancements” where you can read about other folks (now 2.5 years later) maybe not so thrilled with the factory sub.

In that thread I explained my approach for this new boat (which at the time I hadn’t taken delivery yet). My plan was made under the assumption that my 2019 sub would be just like my 2018 sub, which I thought was “okay” but could use some help. In short, I said:

1) Replace factory driver 

 2) Add some polyfill to the enclosure

3) Replace factory cabin/sub amp

4) Tune to my liking 

As you see, I had no plan and zero desire to tackle a new box. Been there done that, and seems like a nightmare in these new two-piece boats. So I figured I could “work around” that.  

DISCLAIMER: I realize many here are happy with their factory sub, and that’s great. “There is nothing either good or bad, but thinking makes it so.” In other words, it’s all relative to your expectations. I’m not here to malign the factory sub or system. Just had some time this morning so figured I’d share what I’m up to.

To be continued...

(pic of my 2018 sub for reference)

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Edited by IXFE

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IXFE
Posted (edited)

Now let’s level set on the baseline... exactly what makes up the factory sub?

AMPLIFIER: Having pulled the factory cabin + sub amp and replaced it already, I can say with certainty that it’s the OEM version of the Wetsounds Syn DX 6 (it even fits perfectly in a regular Syn DX 6 box, see pic below). Channels 1-4 power the cabin while channels 5-6 are bridged to power the sub. We will never know exactly how it’s tuned, but I think we can all agree it’s set up very conservatively (and for good reasons I completely understand).

SUBWOOFER: The driver itself is a Wetsounds Revo 12 HP v2.  This is a single voice coil, 4 ohm driver rated for 500 watts RMS and retails for $399.  Interestingly, wetsounds website still lists v1 of this sub and shows it as “out of stock.”  At some point I’d expect them to flip the site to v2. 

ENCLOSURE: The box is a perfect rectangle with all 90 degree angles. I have verified that the EXTERNAL dimensions are 15” HIGH x 17.5” WIDE x 9” DEEP.  At one point in the 2017 thread linked above it was stated with certainty that the factory enclosure was 1/2” HDPE.  This was false. Wetsounds later came in and corrected the record saying it was 3/4” HDPE.  I have verified it’s 3/4”.  Also, the HDPE is both heavy, and dense (i.e. hard to cut through). That makes the INTERNAL dimensions 13.5” HIGH x 16” WIDE x 7.5” DEEP.  That yields a GROSS volume of 0.938 cubic feet and a NET volume of 0.867 cubic feet (assuming the woofer displaces 0.071). The walls are held together by 32 stainless steel screws (1.5”). I also found a few staples.

For what it’s worth, the Wetsounds manual  for the Revo 12 calls for a 1.1 cu. ft. box, glued and screwed with an additional bead of silicon to ensure air tightness.  Not sure why both Malibu and Wetsounds completely ignored these specs when developing the factory box.

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Edited by IXFE

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IXFE

A few more details on the enclosure. It’s secured to the floor with two lag screws and washers. It also has three strips of thin, black foam underneath. 

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IXFE

At this point you’re probably wondering why I scrapped my original plan to keep the factory box. Simple... my box was installed in such a way that the front/top edge of it was resting against the backside of the helm fiberglass wall. This created a vibration every time the sub would hit. It became even more problematic once I swapped out the factory amp and started sending more power to the sub. It just sounded terrible. I  also had reason to believe that there was an air leak somewhere. 

I suppose I could have asked for a fix under warranty, but why?  All they’d do is reposition an already flawed box. At that point I decided the box was irrecoverable. 

So disassembly began... 

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IXFE

First step is to remove the grill and woofer. Easy enough. But when you remove the woofer you will likely find that not all eight screws are used to hold it in place. Mine was missing the bottom screw almost certainly because of the fiberglass lip directly in front of it. 

Also, when you remove the woofer you’ll find a thin, rubber gasket behind it. If you’ve installed a sub before you’re familiar with this gasket. But what surprised me is the back of the factory woofer has two recessed notches in it. That’s obviously by design, but I couldn’t help but wonder if the thin gasket was enough to seal the woofer to the box with those voids. Curious if anybody knows what they’re for.  My guess is to accommodate wiring for an LED wire ring. 

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IXFE
Posted (edited)

Now the fun begins... getting the factory box out. This was more challenging than I imagined.

The challenge here is the fact I was trying to avoid cutting any fiberglass. That meant at 15” tall and 17.5” wide, the factory box had to be broken apart to get through one of the two openings: Helm (12.5” HIGH x 14.5” WIDE) or Bow (13” HIGH x 12” WIDE).  Be advised that these measurements may vary slightly from one boat to another. Also, if you’re willing to cut fiberglass either of these openings can be enlarged slightly without having to abandon the billet sub grill or the plastic bow storage insert.  I just didn’t want to unless absolutely necessary. 

NOTE: Even though you see a pic above with the lag screws removed from the floor of the factory box, I didn’t actually remove those screws until later. It’s better to leave the box secure so it’s not sliding all over the place while you’re trying to cut it. 

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Edited by IXFE

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IXFE
Posted (edited)

After temporarily removing the big air vent hose to make more room in there, I attacked the deconstruction of the box with a plan... The 15” height seemed to be the constraint; if I could lop a few inches off the top, I could slide it out of either hole. 

The challenge is working through those small openings and fitting your tools into a cramped space. There’s a lot of stuff down there you don’t want to destroy. For that reason I decided against using a sawsall. 

Instead I started with a multi-tool, a jig saw, and my trusty drill / impact combo. 

First thing I did was remove the speaker wire terminal... easy enough!

You’d like to think you can just take all the screws out and it will all just fall apart. Nope. You can only access a handful of the 32 screws. I took a few out before deciding this wasn’t going to be that easy.

You’d also like to think that sticking a multi-tool into each seam will make quick work of it. Nope.  You can’t access all the seams and the multi-tool is slow, especially when it gets to the screws hiding inside.

Working from the bow side, I drilled a few holes and went to work with the jig saw on the top of the box. That worked better, but the jig saw is a little tall so it can’t reach everywhere in there. 

After an hour I’d taken three big pieces out of the top (pics below), but was getting frustrated...

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Edited by IXFE

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IXFE

This was a good start but it took way too long.  I was frustrated so I took a break... for a WEEK!

I studied that last pic a bunch wondering how I could get the rest of the top off. I decided I needed something that could cut that thick, heavy plastic a bunch faster. The answer for me was a grinder with a thin cutting wheel. 

So here’s the plan I hatched...

1: grinder from inside 
2: grinder from backside 
3: grinder from inside
4-5: multi tool, start from front moving toward box corners, finish from inside. 

The front of the box (ie baffle) is soooo close to the fiberglass that I was afraid to use the grinder there. 

In truth cuts 4 & 5 ended up being grinder from the front (starting at sub cutout and moving outward) until I got close to the fiberglass. Then I inserted the multi tool (much slower) and did the rest of the way to the corner. 

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IXFE
Posted (edited)

More pics of the actual process described above...

Pic 1: wear long sleeves when you use the the grinder or plan on getting peppered with hot, black dust. I also marked the cuts with tape to try to make sure they all met at the same place  

Pics 2 & 3: cut 1 from the diagram above 

Pic 4: cut 2 from the diagram above

Pic 5: multi tool working on cut 4

 

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Edited by IXFE

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IXFE
Posted (edited)

You’ll get to a point where you can’t connect the cuts at the front corners. They’re basically blind corners and they’re right up against the fiberglass helm wall. So I finally decided to unscrew the box hoping I could rotate it enough to reveal those corners and finish the cuts. It worked as planned! 

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Edited by IXFE

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IXFE
Posted (edited)

After 2.5 hours, now the satisfying part! 

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Edited by IXFE

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IXFE

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IXFE
Posted (edited)

Now we start designing the new box!  I have to admit, I did some snooping around in there and took some measurements BEFORE taking the grinder to the factory box. I didn’t want to go to all that work only to realize that there was a GOOD reason the factory box is so small. I came to the conclusion that there was room for  a slightly bigger box on the floor inside the helm (both in width and depth).   

The bigger question was could I design something to fit through either of the two openings?  And is there enough room in there to rotate it into place?  Those questions can’t really be answered until the factory box is gone (or some fool takes the plunge first). 

So the parameters were...

VOLUME: 1.196 (gross) and 1.125 (net) assuming 0.071 (driver displacement). I got these specs from JL Audio for their 12” W3 4ohm woofer. Why JL?  Simply put, because I’m bored and want to see why so many people love JL subwoofers.

DIMENSIONS: since my plan was to go through the bow access hole and rotate into position, my box couldn’t be any taller than 13” or any deeper than 12”. But there’s a catch! I learned there was indeed a reason Malibu only went 9” deep on their box. There’s actually room to go deeper; the issue is (as always) on the hull side where the floor starts to move inward with the contour of the bow (pic 2). So you can pick up volume with a deeper box, but it can’t be deeper along the entire width of the box (pic 3).

Pic 1: New JL sub in the house!  As you can see I was also doing some styrofoam modeling (more on that later)  

Pic 2: View of starboard side of the factory box (from above). The blue line roughly estimates where the floor is no longer flat. 

Pic 3: View is the back of the factory box (from above). The blue line roughly estimates where the floor is no longer flat. The green line is where you can bump out the back of the box to get more volume. 

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Edited by IXFE

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IXFE
Posted (edited)

So here’s what I came up with and built out of styrofoam (pic 1 & 2). By my calculations, this design using 3/4 birch (which actually measures out to 11/16” thick) yields a volume of 1.119 cubic feet (net of 0.071 driver). 

When I first tried to get it through the bow hole it got stuck (pic 3). To go this route I would either need to expand that opening (not ideal) or make the box smaller (not willing to compromise). 

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Edited by IXFE

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IXFE
Posted (edited)

So I decided to try it through the hole under the helm.  Flip it sideways and it slid through and rotated into place EASY!

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Edited by IXFE

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IXFE

A couple of things I learned from that styrofoam box going through the helm...

1) since the hole is 14.5” wide and my box is only 13” tall, I could go taller and still get through. So I decided to trade off some height for width. More height is better so less woofer is behind the fiberglass lip. Also, less width (even though there’s plenty of floor space for more) would make the box rotation (upward) easier when getting the box into place  

2) when I looked at the notch (second to last pic above), I realized there’s room to make the notch only 2” instead of 4”.

Making these two adjustments I came up with this FINAL design...

Internal volume is a perfect 1.126 (net). 

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IXFE

So anyway, time for me to stop yapping and start building. 

Stay tuned...

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shawndoggy

Good stuff!  Did you have to special order the ply?  I can only find full of voids veneer around here, when trying to source “Baltic birch” ply. 

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ahopkinsVTX

Great stuff! Love that multi tool right? Will be interesting to see your review of the JL sub. 

 

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IXFE
Posted (edited)
2 hours ago, shawndoggy said:

Good stuff!  Did you have to special order the ply?  I can only find full of voids veneer around here, when trying to source “Baltic birch” ply. 

I found those 2x4 “project sheets” at the local Home Depot. I stood there in the aisle debating birch vs mdf, but chose the birch mainly due to weight.  I was concerned about not being able to rotate an excessively heavy box into position. 

Edited by IXFE

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onewake09
2 hours ago, shawndoggy said:

Good stuff!  Did you have to special order the ply?  I can only find full of voids veneer around here, when trying to source “Baltic birch” ply. 

That’s not Baltic birch. Usually Baltic birch comes in 5x5 sheets. If you have a woodcraft near you they have it. Or some really nice lumber yards can get it. A good place to look is company’s that sell to cabinet shops. A lot of shops use it for draw box sides and bottoms. 

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IXFE
4 minutes ago, onewake09 said:

That’s not Baltic birch. Usually Baltic birch comes in 5x5 sheets. If you have a woodcraft near you they have it. Or some really nice lumber yards can get it. A good place to look is company’s that sell to cabinet shops. A lot of shops use it for draw box sides and bottoms. 

I never claimed it was “baltic” birch. 

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Eagleboy99

Regular birch plywood is a good substitute for this job.  BTW, maybe I missed it, but are you going to glass the sub box?

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IXFE
9 minutes ago, Eagleboy99 said:

Regular birch plywood is a good substitute for this job.  BTW, maybe I missed it, but are you going to glass the sub box?

Haven’t decided yet. Was thinking LineX

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Eagleboy99

Interesting...  I just finished off some floor battens for my Zodiac - 9mm Baltic Birch (LOL) - sealed and painted with Interlux polyurethane paint.  That stuff ROCKS!

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