[michaelddd]

This is my fourth "decent attempt" at designing a ported box for a UXL-18. There were other attempts, but I dare not post their laughable WinISD graphs here.

I downsized from 16 to 12CF. I lost about [email protected], but other than that, everything else looks better, especially port velocity and cone excursion. 1st PR is 142Hz.
Same 15Hz tune, same modeled with 2,200 watts, same 24db/oct bandpass of 14Hz/80Hz.

Please have a look at the attached screenshots and share your thoughts with me. If your thoughts are "Stop messing with WinISD and start making sawdust!" trust me; I'm with you on that. Thanks.

 

[More is Better]

Lower the high pass so that the bottom excursion hump hits xmax. 10 or 12ish


Then put it in a bigger box so that you can get more port area while keeping the length the same.


A bigger box will let the higher hz excursion hump come up too. That helps with cooling when you use the same power to move the cone farther.




You aren't using the bottom end gain that a ported design gives you.


The spl curve looks more sealed box than ported low shelf.


I'll whip something up in winisd for you to compare to.

 

[More is Better]

what are your goals?


how many uxl's are you getting?

 

[DavidK442]

Your design looks good to me. 12 cubic feet internal ported results in a 16-17 cubic feet external box.
Compromising a couple db on the low end to keep box size manageable was a good decision.
As ^ said, you could drop the high pass filter 1 or 2 more hertz and still be within XMAX, though the benefit will be pretty minimal.

 

[michaelddd]

Thank you for all the advice. I'm not very good with tuning/designing...I know the basics of WinISD and how to come up with something that doesn't totally stink. But AFA getting that last 20% or so goes, I need a lot of practice.

I will have two UXL-18s, in separate but identical ported boxes in a 3,300CF room. I plan on putting both boxes behind a screen wall. Each sub will be powered by it's own QSC RMX2450a (bridged 4-ohm load). Each amp will be on it's own dedicated 20-amp circuit. They won't be wanting for power.

My goals? Loud and low. I want to feel that slam when things blow up. Nearfield boxes are not in the plan right now.

I will lower the highpass a HZ or two and see what that looks like. I want to keep the drivers protected though. I don't want to risk blowing a driver just to get down to 13Hz instead of "just 15Hz."

BTW, when you start a new WinISD project have to choose b/t "Superboom box" and -3 low shelf an others. Which one am I supposed to choose? Does it matter if you're going to set all the values for box/port size manually?

Thanks again.

 

[More is Better]

Here is what I would do, especially if you are only getting 1 uxl.


With your model, you are getting a beastly driver and then neutering it by only using about 1/2 its potential.


This is twice the box size, but it's outputting more than 2 drivers can in your model down low. In addition there is more cone excursion across the board, which helps with cooling the VC.


2db or more everywhere
3db at 20hz
7db at 15hz
8db everywhere below 15hz


25cuft net. about 30cuft gross 3.5 cuft for port and driver. about 2'x3'x5' external
14.5hz tune...just so the port tube came out to 48"
12"x48" round sonotube or quickrete port...Round will flow more air than a slot port. Use a 2"-3" roundover at both ends. like this: http://www.subwoofer-builder.com/ring.htm
2000W, I'm assuming you are bridging an inuke3000, set the limiter just below max output and it won't clip till you send it grossly large signals.
Air velocity is 1m/s higher than yours, but the round port can flow more air than the slot port.




Red line is your model
Blue is mine

 

[More is Better]

BTW, when you start a new WinISD project have to choose b/t "Superboom box" and -3 low shelf an others. Which one am I supposed to choose? Does it matter if you're going to set all the values for box/port size manually?

Thanks again.

I would choose -3 or -6 low shelf as a starting point. It won't set the port size for you, just box size and tuning freq.


Room gain should start to help out in most rooms on the low end so it's ok to let the low end droop 3-6db at 10-15hz. Ideally keep the model flat and if you get room gain you have a fatter sub sonic low end.

 

[More is Better]

To learn what effect things have in winisd, make copies of your project and leave 1 as a control and change properties on the other ones. You have to click on the copied project even though it comes up highlighted to select it.

 

[michaelddd]

@More is Better: Thanks very much for modeling that box. I definitely don't want to neuter the driver. I will have quite a bit of room behind the screen wall, so box size isn't really a limitation. I've never built a box bigger than about 8CF before, so this is new territory for me.

Your model wipes the floor with mine, especially under 20Hz. Glad I haven't cut any wood yet. I'm glad we have this awesome, FREE tool called WinISD to play with, but I'm approaching that "paralysis by analysis" point. I know there is no free lunch when it comes to subwoofer design. I just want to do this once, do it right and be very happy w/the results. I've tried to cover the bases. Great driver? Check. Plenty of power? Check. Properly designed cab? And here I am. And we move onward, through the fog! D

 

[More is Better]

@More is Better: Thanks very much for modeling that box. I definitely don't want to neuter the driver. I will have quite a bit of room behind the screen wall, so box size isn't really a limitation. I've never built a box bigger than about 8CF before, so this is new territory for me.

Your model wipes the floor with mine, especially under 20Hz. Glad I haven't cut any wood yet. I'm glad we have this awesome, FREE tool called WinISD to play with, but I'm approaching that "paralysis by analysis" point. I know there is no free lunch when it comes to subwoofer design. I just want to do this once, do it right and be very happy w/the results. I've tried to cover the bases. Great driver? Check. Plenty of power? Check. Properly designed cab? And here I am. And we move onward, through the fog! D

Like you said it's easy to get to 80%, but that last 20% that you can have for only $50 in wood can be hard to figure out.


I just got done building a 35.6cuft gross box. 325lbs without drivers 525lbs with. http://www.avsforum.com/forum/155-diy-speakers-subs/1917921-16-x-12-sealed-sub-cabinet.html If I had to I could manage the build myself for all but flipping the box to put the last panel on. You will definitely want a helper to move it when finished.


I can come up with box dimensions and a cut list if you want.
Are you building with plywood or mdf?
Do you have any max dimensions? How much room is behind your screen?


As far as tools:
An air nailer is nice but not necessary.
Besides that all that you really need is a skill saw, a router, and some clamps and a straight edge.


Off the top of my head, about 3'wide 2'deep 5' tall with the woofer mounted firing left or right near the bottom on the 2' side, port tube coming out the top going down to behind the driver. Pillows stuffed against the top and bottom of the box to kill the resonance from the 5' dimension. Maybe line the rest with egg crate foam if you want.

 

[michaelddd]

I've got plenty of tools. Not much skill, but I have tools. I've built horn loaded subs before but that was following a plan. This is different as I'm attempting to design my own box...and I suck. LOL!


I should have about 36" behind the screen. Not what I wanted, but I have to build the wall out to cover a door to a mechanical room. Door cannot be moved, unfortunately. Still not sure on the depth or overall form factor I'll be going with. It's unlikely but one sub may wind up out in the viewing area someplace. A rectangular box/form factor that I could possibly put a seat cushion on and make it a bench (or a table) is a better idea than a big, flat square that stands upright. This is my problem to figure out, and I will. But first I need to get my cubic foot need sorted out. I'm still playing with WinISD and 20-ish CF boxes.

 

[michaelddd]

OK, Version #5

OK, I think I'm getting a little better at this. I have moved up to 20CF net (HUGE box before all the displacement is factored in!) and this is as big as I'm willing to go. Go big or stay home, right? Remember; I'm going to have two of these monsters.


Modeled with 2200 watts, 12Hz/80Hz 24db/oct bandpass. I have a nice low end shelf now. Cone excursion is RIGHT AT XMAX. I think Port Velocity is OK. Just not sure about the vent. Go higher but narrower? Lower but wider? Dunno. Thoughts? Thank you!

 

[notnyt]

OK, I think I'm getting a little better at this. I have moved up to 20CF net (HUGE box before all the displacement is factored in!) and this is as big as I'm willing to go. Go big or stay home, right? Remember; I'm going to have two of these monsters.


Modeled with 2200 watts, 12Hz/80Hz 24db/oct bandpass. I have a nice low end shelf now. Cone excursion is RIGHT AT XMAX. I think Port Velocity is OK. Just not sure about the vent. Go higher but narrower? Lower but wider? Dunno. Thoughts? Thank you!

It's good. You can go with a smaller box though if you need to. When I was modeling these, two worked nicely in a 27cf box.

 

[Jay1]

Low end peaking says your box is slightly over sized. You should decrease volume until there's a flat line from the mid 20hz range down to the knee, shown as just above 118 db on your graph.

 

[michaelddd]

Thanks guys. I have no problem making it smaller. 20CF is bigger than I wanted. What port velocity am I aiming for? I have read 17m/s is the "standard for max" but I cant' get near that without the 1st PR dropping below 100Hz.

 

[Jay1]

I wouldnt stress too much over that. Your velocity is only an "issue" at infrasonic frequencies with maximum output. Either way dropping box volume to 16 ft3 and using a port with 500 cm2 of cross area will do the trick

 

[notnyt]

I've generally kept the port velocity at maximum power to under 28 m/s with good success. Lower is optimal, but then you lower the port resonance by making the port larger. It's all a tradeoff.

 

[LTD02]

^^ +1

 

[michaelddd]

Thanks again, everyone. Especially for the detailed description of what my SPL chart should look like, why it looks like it does and the info on port velocity. VERY helpful info for me.