Enclosure help for Epic 12 - AVS Forum
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post #1 of 51 Old 04-24-2012, 11:34 AM - Thread Starter
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Hi all, I have searched for this driver here and have read through a few threads. But nothing appeared close to my size restraints. I am building this sub for a 2.1 setup movies and music, 75%music 25%movies.

So since this is going to be mainly for music, I have assumed a tuning frequency of around 24-25. I was looking into a slot ported design, or even round ports. Whichever will give me less port noise.

Talking to a friend he suggested a transmission line design, but not sure if my size constraints can fit this in. OK then here are my constraints, maximum external enclosure size can be 20x20x20 or 17hx17dx40w.

I was hoping for a front firing, front ported design. I will be using a pro power amp, so we dont need to figure in amp displacement. If anyone could me some ideas on bracing for a box they think will work, that would be great, this is my first ever build.

Thanks to everyone in advance for any help you are willing to offer.

Jim.
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post #2 of 51 Old 04-24-2012, 04:07 PM
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What about sealed? Ported may give you a bit more output but you lose subsonics, and the box is a bit harder to build. Epic looks decent in a small sealed box

Yellow is the epic-12 sealed in 1.6cuft (50 liter)
Pink is the epic-12 sealed in 3.25cuft (100 liter)

Both are with 500 watts in and you can see where excursion becomes a problem. The smaller box is less efficient, but can take the full 500 watts only exceeding xmax at the lowest frequencies.

http://i47.tinypic.com/2pshbeu.png
http://i48.tinypic.com/2ypnjn8.png

Others will chime in I'm sure.

Edit: I got the updated driver file for the epic, but it models nearly identical to the Audiopulse version anyways.
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post #3 of 51 Old 04-24-2012, 05:48 PM - Thread Starter
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Thanks for the input. I was considering going sealed, but how it rolls off so much down to 24 and already exceeds xmax at rated power, leaves me no room to eq the low end up. Or am I missing something here?


Would I best going with there 10 inch offering, considering Im more music orientated?
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post #4 of 51 Old 04-25-2012, 01:10 AM
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Quote:
Originally Posted by vwgti View Post

Thanks for the input. I was considering going sealed, but how it rolls off so much down to 24 and already exceeds xmax at rated power, leaves me no room to eq the low end up. Or am I missing something here?


Would I best going with there 10 inch offering, considering Im more music orientated?

No, the 12 is a better driver. if you have the room, always go for a larger sub.
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post #5 of 51 Old 04-25-2012, 08:53 AM
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Quote:
Originally Posted by vwgti View Post

Hi all, I have searched for this driver here and have read through a few threads. But nothing appeared close to my size restraints. I am building this sub for a 2.1 setup movies and music, 75%music 25%movies.

Since your primary need is for music acoustic suspension might be the better choice. The cabinet can be smaller, and the sound is often cleaner. By adding damping material you can improve things even further.

If you take yourself too seriously expect me to do the exact opposite
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post #6 of 51 Old 04-25-2012, 10:07 AM
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hi jim,

you are on the right track with the ported enclosure tuned to around 20hz. for the 25% of the time that you throw some movie stuff at it, it will be a lot more fun than a sealed enclosure by getting you almost 10db more spl around the tuning frequency.

one option is a slot ported enclosure as in the pic, a 2"x15" slot that is a total of ~45" long will tune a 4.0 cubic foot enclosure to ~20hz. i haven't worked out exactly how much volume your cab would have, but that is a back-of-the-envelope possibility.

you don't have to go crazy with bracing. a couple simple 2x2s running from the center of opposite panels is fine.

-----------------

"Since your primary need is for music acoustic suspension might be the better choice. The cabinet can be smaller, and the sound is often cleaner."

i think what gave ported cabs a bad rap was back in the early days of car audio when really cheap drivers were put in cabs with high tunings (40-50hz or so). as they got down into the tuning region, they didn't have the motor to provide any control and so sounded like arse.

most of the best speaker manufacturers employ ported designs in their top of the line speakers (revel, b&w, meyer, genelec, and so on...) and their primary emphasis is on sound quality. no question that for ultimate ht systems, sealed are better, but that is for different reasons, not sound quality of music.

it is time to start killing off the myths...
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post #7 of 51 Old 04-25-2012, 10:15 AM
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Quote:
Originally Posted by JimWilson View Post

Since your primary need is for music acoustic suspension might be the better choice. The cabinet can be smaller, and the sound is often cleaner. By adding damping material you can improve things even further.

If the ported sub is well designed it will sound perfectly "clean"...

Anyway, Your 17x17x40 cabinet looks very nice for a "musical" ported epic 12. Before you do proceed with a ported build, make sure you get something like a MiniDSP, you need a high pass filter for movies or your sub will bottom out.

Place a 1.5" x 15.5" wide x 33" long slot port in the above cabinet. Place a window brace at least every 10" along the length, tie the braces closest to the front and back into those panels with dowels (front) or another shelf brace (rear). Line all the walls with foam (mattress pad), and the very rear of the cabinet behind the end of the port, densely stuff with poly-fill (dont block the port opening. Take a round over bit to both ends of the port.

This will get you a very nice 19hz box that can easily take 500 watts with an 18hz high pass filter.
LL


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post #8 of 51 Old 04-25-2012, 10:39 AM
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jay, why the suggestion for 1.5" when there is plenty of room for a 2" port? wouldn't an even longer and larger port would be better based on air velocity?

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post #9 of 51 Old 04-25-2012, 10:46 AM
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Quote:
Originally Posted by LTD02 View Post

jay, why the suggestion for 1.5" when there is plenty of room for a 2" port? wouldn't an even longer and larger port would be better based on air velocity?

I'm showing increasing the size even to 1.75" increases the length to 40" (2", 45"). Just for the simplicity of a single straight port, as air velocity with the 1.5" port only hits 20 m/s with 500 watts and an 18hz HPF.


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post #10 of 51 Old 04-25-2012, 10:54 AM
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he only has 17" of total depth, so with a front port, he will need at least one bend.

then he has another total of 40" of width with which to work. that gives roughly 50" or so before hitting a second bend.

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post #11 of 51 Old 04-25-2012, 11:05 AM
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I was basing the port off of running side to side width wise. I guess if the ends are blocked(?) that wouldn't work anyway. Either way, he'll have a pretty nice ported sub from that size box.


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post #12 of 51 Old 04-25-2012, 11:09 AM
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Quote:
Originally Posted by Jay1 View Post

If the ported sub is well designed it will sound perfectly "clean"...

The group delay often eliminates bass reflex subs for me, which is why I tend towards acoustic suspension. Both designs have their pluses and minus, but even with that my preference has always been sealed.

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post #13 of 51 Old 04-25-2012, 11:21 AM
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Group delay only rises significantly near tuning. A low tuned ported sub can actually have lower group delay from 30hz up then a sealed box. Here's an identical driver in large and low ported vs mid Q sealed. Going low Q (large) with the sealed box will match the ported. As we've been trying to elude, well designed is well designed, you cant generalize ported vs sealed when you're not talking about mass market subs.
LL


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post #14 of 51 Old 04-25-2012, 11:53 AM
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group delay is largely a change in frequency response.

to the extent that a ported cab has a flatter response, it will as jay points out have a lower group delay. group delay is much more a matter of your crossover filters than the cab design.

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post #15 of 51 Old 04-25-2012, 12:17 PM
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Quote:
Originally Posted by Jay1 View Post

As we've been trying to elude, well designed is well designed, you cant generalize ported vs sealed when you're not talking about mass market subs.

I tend to disagree; I don't feel you can make a blanket statement, but think you can indeed generalize. Based upon what my ears have heard in the past I'm very comfortable with my assessment. YMMV of course.

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post #16 of 51 Old 04-25-2012, 03:25 PM - Thread Starter
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Wow, thanks so much for all the great info. So with my 17x17x40 enclosure, should net me 15.5x15.5x38.5 internally. So either the 2 inch or 1.5 inch will work, with one bend along the backside of the cabinet. Which size port is likely to produce the least chuffing?
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post #17 of 51 Old 04-25-2012, 04:10 PM
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Quote:
Originally Posted by vwgti View Post

Wow, thanks so much for all the great info. So with my 17x17x40 enclosure, should net me 15.5x15.5x38.5 internally. So either the 2 inch or 1.5 inch will work, with one bend along the backside of the cabinet. Which size port is likely to produce the least chuffing?

You really wont have to worry about chuffing from either size, but larger will of course have better airflow. The smaller port will however net you more low end gain, because your internal volume will be larger due to the port taking up less space.


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post #18 of 51 Old 04-25-2012, 05:01 PM - Thread Starter
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Sounds good Jay, think Ill go with the smaller port, since Ill have to factor in bracing displacement.
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post #19 of 51 Old 04-25-2012, 08:57 PM
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"You really wont have to worry about chuffing from either size"

i disagree. based on air velocity and empirical studies of audible chuffing, the 2" might have some audible chuffing and the 1.5" definitely will as you approach max spl.

http://www.subwoofer-builder.com/flare-testing.htm

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post #20 of 51 Old 04-25-2012, 09:14 PM
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Those results are for round ports, and the limit of chuffing varied by port size and roundover. The 4" diameter 3/4" radius ports didn't chuff @20hz until 20 m/s, the velocity achieved by the sub I spec'd at max output.

The cross area of a 4" round port is 81 cm2. The cross are of the 1.5" x 15.5" port is 150 cm2 (should have higher air speed before chuffing, based on the test results scaling).

It think it will be fine, as long as OP has a 3/4" round over


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post #21 of 51 Old 04-25-2012, 09:50 PM - Thread Starter
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Unfortunately no router or round over here. I have a circular saw, a chop saw, a jig saw.

But heres what someone else came up with for me, it seems rather complicated to build , but would this be better than a traditional ported design?
LL
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post #22 of 51 Old 04-25-2012, 09:52 PM
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here you go

http://www.amazon.com/MLCS-8656-4-In...5&sr=1-1-fkmr2


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post #23 of 51 Old 04-25-2012, 09:56 PM - Thread Starter
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Yeah but thats $28 plus the price of a router, lol. All my budget is getting sunk into the amp driver and sheet of mdf, maybe Ill call around some buddies see if they have a router.
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post #24 of 51 Old 04-25-2012, 10:07 PM
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"The 4" diameter 3/4" radius ports didn't chuff @20hz until 20 m/s, the velocity achieved by the sub I spec'd at max output."

not sure where that number comes from.

here is the table.

103 mm is 4 inches. 30 mm is more than inch roundover, but i wanted to give you the benefit of the doubt.

chuffing was detected at 9.6 meters/second.

it can also be seen that the results for a 6" diameter port, which has a large cross sectional area than your suggestion chuffs at 10.7 m/s at 20hz.

last, a round port is better for minimizing chuffing. rectangular/slot ports will be worse, so one should be more conservative in specifying a design with them.


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post #25 of 51 Old 04-25-2012, 10:09 PM
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Ah I misread the flare size for some reason thought 75mm as .75". OP shouldn't even bother with a slot port as he dosent have a router.


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post #26 of 51 Old 04-25-2012, 10:13 PM - Thread Starter
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Now everyones making me scared, lol. I have no idea what to do now. I talked to Parts Express tech, and they recommended my 20cubed enclosure with dual 3 inch ports at 19inches each.

Ive emailed thilo at tc sounds, Ill let you know what I find out.
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post #27 of 51 Old 04-25-2012, 10:16 PM
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"OP shouldn't even bother with a slot port as he dosent have a router."

why? there are a ton of successful slot ported enclosures with no roundovers.

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post #28 of 51 Old 04-25-2012, 10:20 PM
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The radius makes the biggest difference to chuffing according to that chart


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post #29 of 51 Old 04-25-2012, 10:20 PM
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"Now everyones making me scared, lol."

go back up to post #6. ignore the rest. :-)

"Ive emailed thilo at tc sounds, Ill let you know what I find out."

no need to waste his time with something as simple as a ported cabinet for your driver. this really isn't a complicated project.

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post #30 of 51 Old 04-25-2012, 10:29 PM
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"The radius makes the biggest difference to chuffing according to that chart"

that is part of the equation. the other part is the cross sectional area which, more or less, sets the air velocity.

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