Sanity check on plans before starting UXL-18 Build - AVS Forum
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post #1 of 43 Old 05-20-2013, 09:24 PM - Thread Starter
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Hey everyone, if you frequent this form you may have noticed the advice threads I've posted getting ready for my UXL-18 build.

The speaker will be here in a few weeks and I since you guys have way more knowledge on this stuff, I wanted to show you all my plans and see if anything seemed wrong.

Dimensions
The sub will be 25w x 25h x 30d and made with 3/4" mdf with the speaker flush mounted (well, recessed 3/4").

Ports
It will use four 3" diameter x 44" long ports, made from 3" pvc, with precision port internal and external flare. I'm not really a fan of the external precision port flares but I tried making my own and it didn't go so well. I could always swap them out in the future.

The internal volume with all the bracing is 7.55 cubic feet. (7.613 cubic feet with just the main vertical ones).

Tune
With the 7.55 cubic feet volume and port specs winisd shows I should be able to go with a 16hz tune

Design
This is the basic layout for the sub:

*The only thing I've decided to change from this is making the front and back piece 25x25 (instead of 23.5x25) so that the screws for the ports will be the front piece. I'm also going to make the interior bracing 24x24 and slot them into 1/4 dados.







This was my idea for some horizontal bracing. This is the only part of the design I haven't completely hammered out: The tricky part is keeping the 3" clearance around the interior ports.



Power:
I'm planning on using an EP4000 amp. I would love to get a QSC RMX1450 but it's a good 200 bucks more expensive and the only real bad thing I've heard about the ep4000 is it's a copy of the RMX1450 and the fan is loud (which seems pretty easy to fix).

Veneer
I'm going to veneer it with some 10 mil white ash. I was planning on doing 3/4" rounded edges on the top and bottom sides but veneering would be so much easier if I didn't.

Finish
Either way, I'm going to be painting it black lacquer (trying to get the typical black ash finish). I'm going to build a small paint booth but I wasn't planning on using any fans and just going with a suit and respirator but should I look into exhausts? I didn't think it would be necessary for something this small
Applcation will be via the heat glue method, coating the box and veneer and using a clothing iron to heat the glue and trimming with a flush trim router.
Starting with a light 240 grit sanding before painting
Everything will be diluted with 10-15% thinner
two light coats of black #40 sheen lacquer primer sprayed with a HVLP gun.
two light coats of #40 sheen, semi-gloss black
single coat of #40 sheen clear (maybe 2 depending on how much grain I want to see)

Feet
Nothing fancy, I'm gonna go with 4 of the dayton audio 1-3/8 hard rubber feet. Would 4 be enough or should I go with more?

**I'm going to be using ez-lock nuts + bolts for everything so that the speaker, front port flares, terminal and feet are removable

I'm going to build a two dimensional rotating jig so i can paint all 6 sides at once. It will basically look like a U shape with horizontal arms that mount to the box so it can spin along one axis. I'm then going to put it on a dolly so I can spin it along the other axis

Anyone see any holes in the plan?
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post #2 of 43 Old 05-22-2013, 04:58 PM
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I see lots of holes in you plans - but they are mostly for ports by the look of it. If you are building a ported UXL-18 then like most of us here you need an insanity check (to see if your plans are insane enough).

There are others more knowledgeable on here than I - but...

The EP4000 is a copy of the RMX2450 and as such is much more powerful than the RMX1450. Stick with the EP4000.

I would round the sharp internal corners of the odd shaped holes in the vertical braces for increased strength. At least a 3" radius if not more.

I haven't modelled the design so assume you have checked max port velocity & excursion limits and have some kind of EQ/HPF sorted too.

My 2c
Phil
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post #3 of 43 Old 05-22-2013, 08:04 PM
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Why four ports? Can you not achieve a 16hz tune with just one port?
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post #4 of 43 Old 05-22-2013, 10:33 PM - Thread Starter
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Avgass had me worried a bit in with that first sentence hah. I thought the EP4000 was a copy of the RMX1450, not the RXM2450, so that settles that one.

I am planning on rounding all the internal edges with a 1/8" roundover bit I was just too lazy to model it. I'm not exactly sure what you mean about rounding the corners with a 3" radius for the vertical braces?

Here are some of the winisd graphs.

*Does this look good for the magnitude? I'm not exactly sure if you want something smoother or something flatter, or what you are looking for here for that matter.




Also, Marty I didn't think this would be possible with 1 port. I've gotta be missing something. Messing with the winisd model setting it to 1 3" port it says it would be 8 inches. Everything else seems the same, but the port velocity and 1st port resonance go way up.
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post #5 of 43 Old 05-24-2013, 02:07 PM
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Sorry for late reply. Not sure how to explain it better. The braces which the ports pass through have 4 non-circular cutouts. Where there is a sharp internal corner on one of these cutouts there will be a relatively weak spot in your brace. Try to leave a bit more material at each of those points by cutting a curved shape.

FRM looks good. Judging from the cone excursion and port velocity it looks like you haven't inserted enough system input power. You will need to change this figure to circa 2000 watts for a bridged ep4000.
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post #6 of 43 Old 05-24-2013, 05:11 PM - Thread Starter
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Ok, that makes sense. I don't think I was going to cut it that close anyway since it would be nearly impossible.

I'll take a look at updating the specs in winisd.

Thanks!
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post #7 of 43 Old 05-27-2013, 09:17 PM - Thread Starter
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Hey Avg, is this what you were talking about?

Edit: do you think I should do the same on the interior 4 circles on the other brace? Do you think I need horizontal bracing throughout the box or just the extra around the front should be good?


Here are the new graphs with the power set to 2000 watts:


Velocity here is in fps
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post #8 of 43 Old 05-28-2013, 01:36 AM
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Yup - sort-of - but you missed a spot...



Yes you should do it everywhere there is a sharp internal corner in any brace cut-out. Lots stronger for not much more material.

Port velocity is a little high but given that's at max output maybe not the end of the world. You aren't actually driving it to max excursion above tune with 2kw which is a little surprising.

Also - the excursion plot shows just how much you will need a high pass filter at about 12-14Hz but you can experiment with common HPFs in the EQ/filter tab to give you a guide on what might be appropriate.
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post #9 of 43 Old 05-29-2013, 12:16 AM
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You are way better off doing a single large port rather than 4 small ones, two ports would even be better than that. The big thing that winisd does not show is laminar flow through the ports, instead, it provides a very crude port velocity spec which, in the grand scheme of things, can be a poor indication of port noise when other factors need to be considered.
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post #10 of 43 Old 06-01-2013, 06:44 PM - Thread Starter
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Thanks for the info army. Edit: Looking into laminar flow, is your concern what the effects would be using 4 ports since it increases that changes of different port velocity?

Everyone I've checked with though said the ports should be ok. I prefer the look of round ports to square ones and I looked at using three 4 inchs port and with an outside flare (~7.25 inch diameter), it won't fit on the front of a 25x25 box with this driver.

I'm gonna try and get an updated final design done within the next few days (using the current plans as of now).
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post #11 of 43 Old 06-14-2013, 03:25 PM - Thread Starter
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Finally got a chance to update the design a bit. I'm still on the fence about whether to triple layer the battle. I'm planning on doing one layer of 3/4" mdf and one or two layers of 3/4" plywood.

This is the rear bracing (I feel like it may be a bit restrictive)

Layout for the sides

Layout for the top/bottom


I decided to just go with 4 strips of mdf running the entire length of the sub for some horizontal bracing. I'm also going to round over all the edges it would just take way too long to model up.


Still waiting to hear back on when my driver will get shipped
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post #12 of 43 Old 06-14-2013, 09:47 PM
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That rear brace seems like a lot of work with little benefit. Your ability to tie opposing panels together is limited by the 2" or so pieces you have at 12, 3, 6 and 9 o'clock. That big center section does nothing to add strength or rigidity to the cabinet. If you like that design you could just make a cross in the middle of the brace without all the extra stuff and holes. This would be just as strong and allow for more airflow.

The method I normally use is 2-3 inch strips around the outside of the brace and on the inside to make a shape like a pound sign # . This ties the panels together in more places and allow multiple wider/stiffer brace segments . I like baltic birch plywood for bracing as it is much stiffer than MDF and is supposed to make better (albeit more expensive) bracing. It is also lighter than MDF and isn't a bad thing in heavy sub builds.

Good luck!
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post #13 of 43 Old 06-14-2013, 10:08 PM - Thread Starter
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The holes in the rear brace (except for the center) are there to hold the ports (since all 4 curve back towards the front because they are so long). You can see these in the original picture.

I would need to find some other way to support them there as I'm not sure I'd want to leave them unsupported.

If I could I would run strips through the center but I can't since I need to keep the area around the internal flares open
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post #14 of 43 Old 06-14-2013, 10:19 PM
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Oops, sorry for not catching that. Ports do create all sorts of extra headaches. I am having to compromise on bracing myself in my current speaker build due to the ports. Good luck with the build.
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post #15 of 43 Old 06-15-2013, 12:00 AM
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Those braces are a whole lotta work for nothing. Making a simple window brace is just as good and will take half the time. Don't over think things here. Simple is generally better. I'd also go with either 1 big slot port or 2 smaller round ones. Simple brotha, keep it simple!

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post #16 of 43 Old 06-15-2013, 12:08 AM - Thread Starter
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Ya, I know it's gonna be a lot of work. I prefer the look of cylinder ports to slot ports.

I don't think I'd be able to get away with 2 round ports though.

How do people generally mount cylinder ports with a pipe anchor brace? I could do a window brace (which is way easier) but I haven't found a great method of mounting the ports, and a lot of the methods I've seen use holes cut in the bracing.
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post #17 of 43 Old 06-15-2013, 01:06 AM
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Here's a link to review of a highly-respected sub in a 7cf box that manages 16Hz:

http://www.hometheatershack.com/forums/speaker-subwoofer-reviews/64828-svs-pb13-ultra-subwoofer-review.html#ixzz2VgAlD18R

Pics show internal bracing with 3-3.5" ports.
Long sweep 90 deg. elbows make the turns.


Hope this helps in your plans,
sgibson

btw, nice sketch work!
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post #18 of 43 Old 06-15-2013, 03:23 PM - Thread Starter
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That sub was basically why I thought of building my own. I was looking at getting one and doing reviews at that point people started suggesting just building your own.

Checking out the bracing on that, they have some pretty close to the opening of the internal ports. I thought you wanted to leave a space around the port opening clear of any obstructions the side of the port So in this case, a 3 inch port opening would have nothing within 3 inches of it (creating kind of a dome)?
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post #19 of 43 Old 06-15-2013, 04:00 PM
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Quote:
Originally Posted by N8DOGG View Post

Those braces are a whole lotta work for nothing. Making a simple window brace is just as good and will take half the time. Don't over think things here. Simple is generally better. I'd also go with either 1 big slot port or 2 smaller round ones. Simple brotha, keep it simple!
+1. Any material that's within 6 inches of the cab corners is excess weight, cabinet volume reduction, material and work. So are surface mount spline braces. What you have there is a gussied up version of the picture below left. The picture below right works better, despite using less material:


Bill Fitzmaurice Loudspeaker Design

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post #20 of 43 Old 06-15-2013, 05:18 PM - Thread Starter
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I'm not purposefully trying to make it complicated, I swear tongue.gif

The front bracket has the large circular opening because it's close enough to the driver that the circle needs to be there for clearance of the magnet.

I'm not sure I'd be able to do the # bracket; I would still need some way to figure out how to brace the ports.

I could use some metal pipe straps but I'm not sure how secure they would be.

If I could get some clic clamps (like these: http://www.savko.com/partlist.asp?pgid=5&ptid=21 ) that would help but those are 8-13 bucks a pop and I would probably need 8 (2 per port)

Even the ones grainger has are expensive.
http://www.grainger.com/Grainger/CADDY-Pipe-Clamp-1RVD1

I would still need some way to get the bracing around the ports anyway, so it may not end up being that much simpler.

I could go with the # bracket and run 3 vertical supports.

Let me try and design something with simpler bracing where the ports are supported by pipe clamps instead of the brackets
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post #21 of 43 Old 06-15-2013, 05:42 PM
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the ports are a little small for the driver/cab/power.
you will likely get some chuffing with unmasked low frequency content at high power.

run your winisd model. plop in 2000 watts. take a look at rear port air velocity.
around 20hz, 17 m/s is about where you will get some chuffing with decent flares.

all the crazy bracing and dadoing isn't required, but to each his own.

i see nothing in the plan for a high pass filter. that could be a problem.

run your winisd model. plop in 2000 watts. take a look at cone excursion blowing up under tuning.

if you are lucky, the electronic rolloff in your signal chain may help keep that under control,
but you might not be lucky. :-)

overall, that driver/amp/enclosure should perform about the same as the pb13u on the lower end
and perhaps a little better on the top end.

good luck with it.

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post #22 of 43 Old 06-15-2013, 06:33 PM - Thread Starter
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The xmax graph looks good at 2000 watts, the air velocity is something that could be an issue though.

At 20 hz, without a high pass filter the velocity is 24 m/s. It peaks at about 52 m/s at 14 hz or so.

With a butterworth highpass filter of order 2 with a 20hz cutoff the velocity is 17 m/s at 20hz with a peak of 23m/s at 16 hz or so. I'm not exactly sure the logistics of the high pass filter and how they work (and what their affect.

This is in winisd though so I'm not sure how the flared ends will affect those
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post #23 of 43 Old 06-15-2013, 07:16 PM - Thread Starter
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So it looks like I can do with the # bracket, I just need to find some way to brace the ports. Should the intersection points be rounded?

The last one is a top down view (ignore the dados, I left them in). I'm not sure if I'd be able to get any bracing perpendicular to those though.
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post #24 of 43 Old 06-15-2013, 07:49 PM
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Like this? The red bits in the corners would wedge/hold the port tubes into place. You could even make those sections completely round if you wanted.



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post #25 of 43 Old 06-15-2013, 07:52 PM - Thread Starter
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Well that was kinda the original plan (the pvc mounts being part of the bracing). At that point I feel like I'm getting closer to the original design though
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post #26 of 43 Old 06-15-2013, 07:55 PM
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It is similar to the original design, but should be stronger since you'd be using the # bracing. It should be simple/easy to make, and strong. I don't even think you'd need any extra bits like I show in the upper right corner. I think just having the extra bits of wood in the center for the tubes should be enough.
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post #27 of 43 Old 06-15-2013, 09:43 PM - Thread Starter
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Here is a pic of the original and # rear bracing overlaid. I'm not sure what would be a good way to get a hybrid of the two so it can support the braces.



This was my quick mockup of how to possible brace the center but I can see that being pretty weak. The top, bottom, left and right center pieces wouldn't need to be there, so it certainly would use less material, unless all the corners need to be rounded.
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post #28 of 43 Old 06-15-2013, 11:18 PM - Thread Starter
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Also, should I try and get some bracing perpendicular to these two or should these two be enough?
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post #29 of 43 Old 06-16-2013, 06:42 PM - Thread Starter
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Updated the bracing and kinda ended up with a hybrid of the two. I actually like the design, but man would it be a pain in the ass to implement. The one on the left is the rear one and the one on the right is the front one.

Edit: should I try rounding some of the corners to increase strength?
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post #30 of 43 Old 06-16-2013, 07:22 PM
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Edit: I'd get rid of the round portion on the front brace as well. Just make it a normal # shape.
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