New helm subwoofer encloser design help for malibu 247

[David]

Draggin,

You can run the identical size of box and port as another woofer of the same size, but it's not likely the best match.

Each woofer will have a set of specifications called Thiele/Small parameters. Those specs will determine the ideal box size and tuning frequency for that particular woofer.

[Draggin Nutz]

Thanks David! I will go by the requirements and figure in an areo port by the total inches it suggests for port size area, but I do no count the either flared end in to the length correct?

I am doing a 1" thick Plexiglass window with LEDs and mirror lining inside the box. Also gonna try my hand at etching an emblem that will be lighted with different color LEDs. Should be fun.....

[rjones]

Draggin, check the specs from the manufacturer of your sub and they should provide a spec sheet that gives you the optimal cubic feet for sealed/ported enclosures. Like David said, yes you could mimic my box build but it probably wouldn't be optimal for your subwoofer.

On another note......box is coming together slowly but surely.

[David]

Draggin,

You must include a portion of the Aero port flares and they have a calculator for this.

Here's the tricky part with an Aero port. You need to find the right diameter and they really don't have enough size options because they jump from a 4" to 6".

For the Sd of a 15" sub, the ideal port surface area would be 25 sq.in. The absolute minimum would be 14 sq.in.

A larger port diameter makes for a longer port and creates more displacement. That can be a challenge, especially with such a large woofer and box going in a limited space.

Too small of a port reduces port efficiency at higher output levels and invites noise (chuffing).

Radiusing the port entrance and exit is just about as effective as an Aero port. It makes for a great visual but that entire flare is not necessary to obtain a reduction in turbulence. Something as simple as a wood ring can allow you to use a larger roundover, although this wouldn't be needed with a 1" baffle. So in case the Aero port is not the right fit, keep your options open with PVC or a rectangular port since you are dealing with some restrictions.

[David]

rjones,

That's really going to be a nice box.

Compound angles give me a terrible headache.

[Draggin Nutz]

Thanks guys, things sure have changed since I was playing with this stuff in the early 90's.... Digital age.

Box is wicked Jones!

[rjones]

Here is another update of my box build. Put it off for a few weeks and realized memorial is under a month away now! Put it into high gear and got alot accomplished today! I hope to get it rhino lined/Line-X'd next week. Here are some progression pics of my build up to this far.

Let's just say the compound angles on this box made me about pull my hair out! I am proud to say I actually used a hand power saw for this whole build and didn't touch my table saw.

New Amp to send the power for this hungry 15" XXX. Hifonics Brutus 2400.1!

Here is the sub mocked up. I am still trying to decide on my port and I am leaning towards doing a slot port on the left side of the box. I wanted to do the port above the sub but there isn't enough room to make the port I would need. An aeroport would be the easiest way to go obviously but I really like the look of a nice slot port. Thoughts?

[shawndoggy]

excellent work!

I'm a fan of the precision port because you can correct/adjust the tuning to address mistakes (or just make changes). with a slot port you are committed.

But I don't have near the precision that you do in the build, so my issues with a slot may not be your issues.

[rjones]

Thanks Shawn! That is a good point on the tuning...all you have to do with the precision ports is adjust your length of the port and bam, you've got a new Hz! I like the idea of having the ability to change tuning if I think it's tuned to high or low.

Gonna think on the port design and decide in the next day or two which route I wanna go.

[Bawshogg]

I am gonna say you are need a 6" aero AT LEAST to avoid port noise with that sub. It moves ALOT of air.

[rjones]

I am gonna say you are need a 6" aero AT LEAST to avoid port noise with that sub. It moves ALOT of air.

Ya for sure.....from the calculator on the Precision Ports site, I would need a 6" port with 13.96 inches of port length. I am super excited to get this sub running though because I had an old school pre 2005 model 15" XXX that I was running 2500 watts to with an old orion 2500d that absolutely banged! These newer models supposedly cant handle as much power but have better SQ.

[MLA]

Given that the enclosure is 90% complete without the port being part of the design, I think the round ABS port might be the way to go. Once concern, will you have room next to the woofer for the flange of a 6" port?

[rjones]

Ok I am in the final stages of box and need a little guidance from you all.....I've decided I am going to do a slot port on this left wall of my enclosure. The height I have to work with is 13.5" so my question is; should I do a slot that uses the whole height on the left wall with skinnier port or would it be best to to do a smaller height but wider port? Obviously it would be much easier to do a port the whole height of the wall because all I would need to cut is one piece for my port length instead of 3 to make the rectangle. Thanks for any suggestions!

-Random thought......I was wondering if the angled back piece of box is an issue with creating port noise since that is where the sound waves will be exiting?

Edited May 6, 2015 by rjones

[IXFE]

I did exactly what you are proposing... I decided late in the game to go with a slot port. Like you I had 13.5" of height to play with and I decided to use all of it. So my slot is only 1" wide, but it's 10.75" deep. The math works our to 38hz with a 1.75 cu ft (net) box, which is right where I'm at. Your math will obviously be different.

I've received mixed advice on whether 1" is too narrow or not. I used this calculator to get the size right.

http://www.the12volt.com/caraudio/boxcalcs.asp

I wish I could tell you how it sounds, but like you I'm not done yet. So here are some pics.

[rjones]

Awesome that is the feedback I was looking for and nice job on your box. I am ready to be done with mine to say the least lol. Hoping to get my port done this weekend and have it Lined next week. I still need to figure out my exact ft^3 but I am guessing it is around 3.8 after sub displacement and I am going to tune it around 33-34hz. This thing should get plenty loud with 2400 watts going to it :woot: :woot:

[nyryan2001]

Excellent work!

If a 6" port won't fit... You can do two 3-4" ports

[rjones]

Excellent work!

If a 6" port won't fit... You can do two 3-4" ports

I am either going to go with a 13.5" X 2" or a 13.5 x 2.5" slot port. I know with a slot I am commited to whatevert I tune it to but I really like the look of a slot as opposed to round aerports. I just need to make sure I do my due-diligence on the front end and get my slot wall cut to the right length. Hopefully it doesn't sound like doo doo after I am done!

[nyryan2001]

Go bigger than smaller.

If the tune is off you can shim it smaller. You can't easily shim it bigger.

[MLA]

If the tune is off, you would need to adjust the length of the port, right? Shimming the opening wont work, would it, you would need to "shim" the entire port length?

[rjones]

Yes the length of the port is what dictates the tune. I am more worried about port noise with the 2 inch port, which equals 2X13.5=27 inches of port area if I understand correctly?? I cut my slot to 2 inches this morning and now need to get my port length dialed in.

I cut a mock piece to 15" and it sounded ok with the sub

just sitting in the box but I think I need to shorten it up to somewhere around 12".

[David]

At the port/box tuning frequency the woofer will display the least amount of excursion. With a target frequency in mind and a tone generator (disc or app) you should be able to confirm the target.

[CRF-Rider]

Excellent wood working fellas!

IXFE, a few recommendations; assuming you have a router, I highly suggest putting a 3/4" roundover on your port. 1" is a bit narrow, the roundover will help eliminate any would be port noise aka chuffing. Since you went with a double baffle (excellent decision, btw) I'd go around that cutout with a router and rabbet to flush mount the sub. I use epoxy resin on boxes going in a boat, and since you're using MDF I'd consider it a requirement. US Composites has good resins at great prices.

rjones, that's a 15" xxx, correct? If you decide to go with a tube port, a 6" PSP port will serve you well. Unfortunately it doesn't look like the port will fit on the same plane as the sub. The outer diameter of the 6" PSP port flange is 9 1/4." What you could do is cut a 6" hole and have part of the port external from the box. The port does not have to be internal, in fact some people mount the entire port externally, albeit a bit silly looking. I'd also add some dowel rods for bracing, you'll want it with that monster sub. It's easier to get away with not adding bracing on slot ports because the port itself acts like a brace.

I made a post on WW a few years ago that may help you with port displacement, etc. http://www.wakeworld.com/forum/showthread.php?t=792943

One other thing, you mentioned getting it lined, I think the DIY herculiner is great, it's cheap too. If you don't mix it, it'll give you a nice shine too. Not something I'd want on my truck, but great for sub boxes. Here's a pic of one I built for a buddy with herculiner.

[rjones]

Thanks for the input CRF! Yes this is a 15" re audio XXX and it is certainly a big ole sub. I actually cut my slot port out this week and I am fine tuning my port length to get it where I want. I am not doing any internal bracing in the box. As you noted, the slot port actually helps brace the box a little bit and I am going to do a wood support off the bottom of the box to the subs magnet to help support alot of the weight. This is very important when you consider hitting wakes on a rough busy weekend and how much this sub weighs.

As for the lining, I am just going to one of our local after market trucks shops around here and let them spray it. I'd rather not mess with it and it wont take them long to spray the box down. I still need to round all of my corners and sand the box but here is where I am at with the enclosure.

Edited May 11, 2015 by rjones

[IXFE]

Excellent wood working fellas!

IXFE, a few recommendations; assuming you have a router, I highly suggest putting a 3/4" roundover on your port. 1" is a bit narrow, the roundover will help eliminate any would be port noise aka chuffing. Since you went with a double baffle (excellent decision, btw) I'd go around that cutout with a router and rabbet to flush mount the sub. I use epoxy resin on boxes going in a boat, and since you're using MDF I'd consider it a requirement. US Composites has good resins at great prices.

Thanks for your help, CRF. I actually did round the outside edges of the slot... not sure if you can see that from the pics I posted. Are you saying they should be even rounder??

[shawndoggy]

yeah IXFE, he's saying it with a BIG roundover bit.