Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Ported Exile Sub Box Build - '05 VLX


Big_Moose_Wakesetter

Recommended Posts

Okay so I've spent the last couple of weeks reading a lot on sub box design and drawing something up for my '05 VLX. I've got a new Exile xi12 on the way from Brian and I got a used Exile xi1500.1 amp via ebay that was delivered yesterday. Almost everything I know about sub box design & tuning has been learned the past 2 weeks - I'm afraid I'll never finalize a box design and actually start building it!

I've decided to take a stab at a ported box and I think on-paper I have a rectangular box design (or two) that will fit under the steering wheel area and give me the right volume (Brian says 2.2-2.4 cu ft). I need to confirm with a cardboard mockup this weekend. I've got a few decisions that I'm having trouble with.

First, I've definitely read too much about tuning the box. I think I have a handle on how to calculate what my box would be tuned to, but I'm not sure what I should be targeting. I'm going ported for a little extra punch, but I don't want to sacrifice sound quality. Should I be shooting for 30hz, 33hz, 35hz? I need some suggestions on that.

Having trouble deciding between a round port or a slot port as well. On paper I think I have designs for both that will work (depending on tuning). First, I'm open to suggestions on one vs the other and whether or not I should be worried about flaring the ends if I go with a round PVC port (which looks like fun to try with a heat gun). I want to point the sub toward the driver, but I was considering porting it out to the right toward the hull. I can do that easily with a round port. I'll have to have a 90-degree bend in a slot port due to the length though, so I'm not sure if it's a good idea to have that port start close to the baffle. I guess I'm just looking for suggestions on whether or not to port straight out or towards the hull.

Also, Exile suggests a 4" dia, 14" round port. What's a good width for a slot port on this size box though? The height of the slot itself would be 14" to 15". I'm thinking 2" but I have no idea.

My remaining questions relate to box stiffness. If I go with a round port, I'm expecting the outside dimensions to be about 20" wide x 16" high x 20" wide. That should give me 2.46 ft^3 - accounting for a 4" round x 14" port but not the sub displacement or any bracing. It looks like I'm going to have to make a new kickplate because the stock one is at quite an angle (takes up too much volume to design the box around if I wanted to leave it). I'd like to be able to screw that new kickplate into the sub, but not glue it so I can remove it more easily. Therefore it wouldn't really work as a double-baffle. Should I be okay without a double-baffle on top of this?

That brings me to bracing. I'm thinking 1" hardwood dowels from Home Depot or maybe 2x2's here to keep it simple. Maybe one in the middle vertically and another in the middle horizontally. Are these overkill for a box this size? Should I be going with two instead? And should I also add one between the baffle and the back of the box?

And finally, most designs I've seen that use dowels appear to just glue them in. I was thinking I should pre-drill (and countersink) screws from outside the box into the center of each dowel or 2x2. Any reason not to do that?

Okay lots of questions in there. Thanks for any help! Here's to hoping I can just pick a design and get going soon...

Link to comment

Okay too many questions in that first post I guess! I think I've pretty much finalized my box design. I made a cardboard mockup last night and it fit.

I've got a new question that maybe someone can chime in on though. Is there any reason not to coat the interior or a ported box with truck bed liner to seal it from moisture? I'm thinking about having the outside of the box coated professionally with bed liner after being disappointed with how my amp rack came out when I did it myself (I think I used a Rustoleum spray can - it stayed way too rubbery).

I got a decent price from a local place that will coat it in Line-X (assuming I'm flexible and he does it when he also has a truck bed to do). Rather than using something like fiberglass resin on the inside of the box, I was going to have him do the inside as well. He said he'd so that at no additional cost. Would that be bad or the acoustics or is there any other reason why I shouldn't do it that way? Thanks!!!

Link to comment

Spraying the inside of the box will decrease volume, so you would need to account for that. If you are going to line-x the outside then not sure I'd line x the inside. If you are worried about moisture inside the box then I'd be more inclined to go with a sealed box, because that same moisture will be working on the driver. Make sure the port location will not be getting a direct shot of moisture (from chili dip, rain storm, spilled drink, shaking dog, etc.).

Link to comment

If you build the box out of 13 ply baltic birch instead of MDF, you'll have a lot better box structurally and it won't disintegrate if it gets a little wet. You can use a thinner resin, designed for fixing dry-rot, to seal the outside.

Link to comment
If you build the box out of 13 ply baltic birch instead of MDF, you'll have a lot better box structurally and it won't disintegrate if it gets a little wet. You can use a thinner resin, designed for fixing dry-rot, to seal the outside.

Thanks I've seen baltic birch suggested a number of times but I have no idea where to get it here in Syracuse, NY. Lowes & HD don't carry it and we don't have Menards here.

And any specifics on what type of resin you're suggesting?

Link to comment

Thanks I've seen baltic birch suggested a number of times but I have no idea where to get it here in Syracuse, NY. Lowes & HD don't carry it and we don't have Menards here.

And any specifics on what type of resin you're suggesting?

Look for nice finish grade 3/4" plywood, Make sure there are lots of layers in it. It probably doesn't matter if its poplar, birch, cherry, etc because that is just the veneer on the top, unless it is really a specialty plywood and the plys are made of a special species of wood. Compare it to an ACX grade, or tongue and groove subfloor grade and you will see those have much fewer layers (plys) than a finish grade plywood used for furniture and cabinets. Lowes, HD, or your local lumber yard should have it. Lowes here even sells it in 2x4 and 4x4 cut sheets.

Ditto what robtr8 says about not using MDF/particle board.

Edited by MalibuTime
Link to comment

Google "hardwoods in Syracuse, NY" and Lakeshore Hardwoods pops up. Looks like they have Baltic Birch. I built my boat's box out of MDO. You might also see if there is a Woodcrafter or Rockler nearby.

As for resin, Google "wood rot epoxy". One of the above retailers should have something. I use Abatron.

If you haven't met Kreg pocket screws yet, check them out. Can make building casegoods a lot easier.

In terms of box design, I sub it out to this nut job: http://pwkdesigns.com I specify driver, wattage and application and he sends back a very detailed set of buildable plans. Even if you don't buy plans, his video's are very informative on box building.

Edited by robtr8
Link to comment

Thanks for the replies and suggestions! I'll definitely check out the videos on pwkdesigns.com and I'm going to make some calls today to see if I can't find some decent plywood around here. I'd been tentative planning to use some birch plywood from HD but that sounds like a poor choice from what I've read.

I do have a pocket hole jig already and I love it, but I was under the impression that it was a bad idea to use that on a sub box (in addition to glue of course) because the screws would be coming out through the edges of the plywood. I thought that'd be likely to split it. Am I mistaken on that?

Whatever wood I end up going with, can anyone else elaborate on whether or not it'd be a bad idea to coat the inside of the box with bed liner and why? I can probably account for the slight volume decrease by adjusting my port length so I'm not terribly worried about that. I'll go with a resin if the bed liner's going to degrade the sound or something, but since I can have the inside of the box coated with bed liner for free (if I do the outside) it'd be cheaper and easier and easier than a resin.

Edited by Big_Moose_Wakesetter
Link to comment

B_M_W,

I see no acoustic or other reason to not have the interior coated with spray-on bedliner also, especially if you account for the small offset in displacement. The only issue I see is that it will be hard to get coverage on the back side of the baffle surface without first brushing it in by hand.

You still have a raw paper cone on the interior side of a vented enclosure. It's going to be important that when you store your boat under a cover that the carpet and bilge are dry.

Link to comment
Why not make the box out of 3/4" polymer? This is what was used for my Xi12d ported enclosure. It's really pounds too!

20140620_201831_zpsglon29g6.jpg


I love the idea, but did you have to get that from a plastics shop or something? There aren't many places like that nearby that I'm aware of.
Never mind - I was just re-looking at the thread on your recent build. Lots of awesome work in there and fantastic info in the thread. Much appreciated! I actually just got that same Milennia bluetooth adaptor last week as a result of reading that thread. I was pretty impressed with the sounds quality the only time I've been out with it so far.

I know that you had a shop build the box for you. It'd be great to build the box like that myself, but from the looks of it a 4' by 4' sheet of 3/4" HDPE is pretty pricey. If I can get my hands on some of that for a reasonable price though I'll be all over it!

B_M_W,
I see no acoustic or other reason to not have the interior coated with spray-on bedliner also, especially if you account for the small offset in displacement. The only issue I see is that it will be hard to get coverage on the back side of the baffle surface without first brushing it in by hand.
You still have a raw paper cone on the interior side of a vented enclosure. It's going to be important that when you store your boat under a cover that the carpet and bilge are dry.


And thanks so much David! I know you know your stuff REALLY well so that alleviates any concerns I had about bed liner impacting the sound quality. I can see your concern about the back side of the baffle. That could be tough to reach with a spray gun - I already had the same concern. I'll have to chat about it with the guy to see what he thinks.

Thanks again for the help!!!

Edited by Big_Moose_Wakesetter
Link to comment

The only issue I see is that it will be hard to get coverage on the back side of the baffle surface without first brushing it in by hand.

Build the box a smarter way: leave a rear panel off to spray the back of the baffle. Then once the back is on come in from the front and spray the rest.

You haven't been retired that long have you? :Tease3:

edit: Usually takes more planning than that to get all the port walls done properly.

Edited by jk13
Link to comment

Build the box a smarter way: leave a rear panel off to spray the back of the baffle. Then once the back is on come in from the front and spray the rest.

You haven't been retired that long have you? :Tease3:

edit: Usually takes more planning than that to get all the port walls done properly.

Ha thanks that's kind of what I was thinking myself.

All this talk about spraying makes me want to use the Earlex HVLP I got this winter. Is there anything that'a good for sealing the wood that I can spray with a low-power gun like that? Polycrylic maybe?

Link to comment
  • 3 weeks later...

This box build is taking me way longer than I'd hoped...my primary delays are due to my very limited opportunities to use my router. My 5-month old is on her way to bed when I get home from work every day and she doesn't sleep so well with the router screaming in the basement...

The build is going well though. I got some 4" PVC from HD and was able to flare the end of my port (the end inside the box) using a heat gun and a metal bowl (thanks YouTube). I've got a coupler that I'll use so that I can tweak the port length if necessary.

I found some Baltic birch plywood (really nice stuff compared to what you find at HD) and assembled the box with pocket screws first to make sure everything looked good...used the router to flush-trim some sides, etc. Three quick questions I was hoping to get some help with:

I've disassembled the box so I can add some Tightbond III to to every joint. I'll re-assemble it with the pocket screws, then caulk the inside seams with All of the pocket holes are inside the box. Should I fill those with some wood filler or the plugs that Kreg makes or is theat totally unnecessary?

I've got some fiberglass resin ready to go to seal the wood as well. Would I be better off putting that on each board while the box is disassembled so that I can get the edges or just pit it on the inside and outside of the box after I reassemble it?

And finally, should I pick up some 12 gauge speaker wire to run to the sub or is 14 gauge plenty? I already have 14ga run from my previous sub. Again, I'm powering an Exile xi12d with their xi1500.1 amp. The amp will be mounted in the observer's compartment so the speaker wire runs from there over to the driver's footwell.

Thanks as always for any help!

Link to comment
  • 2 weeks later...

Okay no answers to those last questions so I'll tempt you all with some progress photos! My build is going slow, but last night I finally got the un-finishes box into the garage for some testing. I was promptly reprimanded by the wife, who said "I just got the baby to sleep and all the glasses in the house are shaking" so I'd say it was a success!

- Box is built from 3/4" Baltic Birch and secured with pocket screws on the inside and Titebond III. The top and baffle haven't been glued yet to let me continue to tinker. Haven't caulked yet either but the seams are nice and smooth so it's pretty close to airtight as-is.

1045CCC4-6C61-45C7-A41B-D6EAF9BE674A_zps

D0AB9D55-4AB4-4A69-BF36-D072F14AFE7F_zps

70BE7E9E-F596-48AA-8ACF-87497CD8A957_zps

4B9334B5-253C-43E0-9999-8C784CA93468_zps

-Dimensions are 21"x16"x16" before the double-baffle, which adds 3/4 to the depth. If you look closely you'll notice my one screwup so far. In my haste to get get done with the router quickly (I get yelled at for the noise), I rounded the corners of the front face, or 'inner baffle.' Thankfully it doesn't look too bad in my opinion and will ultimately be behind a new kick plate (I think at least).

- The port is 4" schedule 40 PVC from HD. I flared both ends with a heat gun and metal bowl. The hole in the outer baffle fits the O.D. of the tube and a coupler is set into the inner baffle, so I have 2 separate flared PVC tubes right now.

I'm trying to finalize my tuning/port length before I glue the top & baffle, caulk, fiberglass resin, and paint. I'm basically at my max port length right now and (as you can see) the port is protruding out the front a bit far so I'll take an inch or so off of that (it looks like less when the sub grill is on). I can also shorten up the internal piece of the port.

Before I do that, I thought I'd ask for opinions on what frequency to tune to. I get a kick out of a sub that hits hard (cleanly) but that'll be very occasional so I'm looking for some balance as well. I hooked my phone up to the amp and used a test tone generator to manually try and determine what I'm currently tuned to (based on what frequency results in the least vibration in the sub). I came yo with between 29 & 30, which lines up with my calculations.

Again, this is my first box build and all of my 'experience' with tuning is read (recently), not actual experience. I'm thinking about adding a 2nd coupler to my port tube inside the box to allow me to leave the flared ends alone and vary the length of in-between. That way I can tinker with it in the future and not be locked into whatever I decide on now, but I'm not sure I want to add that and potentially disrupt the airflow.

Okay monster post, but hopefully it's useful to some people in the future. I'm open to any suggestions/criticism/praise(?)! And my one question probably got lost - what recommendations do you guys have on a target tuning frequency? Right now I can shorten my port to go to anything higher than 29Hz. I was thinking maybe 32 or 33. I'd be curious to hear the output difference at say 35, but unless I use another coupler as described I can't go back down from there once I shorten the port.

Thanks as always!

Edited by Big_Moose_Wakesetter
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...