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Discussion Starter #1
Hey folks. Quick background if you don't read the intros. I come here from... errrr... another forum :) seeking advice and guidance on my next sub build. I currently have 1 IXL 18.4 in a 2x2x4 simple but effective box powered by the popular EP2500 in my Cheap Seats Cinema. A friend of mine, and fellow shackster, titch-- is selling me his Atlas 15s so he can upgrade to some 18s. I don't have the room for IB, so I'm going to build some nice corner boxes at the sides of my screen.

Here's a rough Sketchup diagram of how I'm proposing it looks. Ignore the single 18 in there. So, one of these in each corner at the sides of the screen.



That's the basic design. The dimensions are not cast in stone. I have wiggle room on all dimensions but the height. Exactly how much wiggle room... I'd have to measure but it's safe to say probably 6 inches in all directions. I'd like to keep the angled face for some architectural appeal unless there's some sonic standing wave resonance 48th order bandpass thingy I don't know about.

So I guess what I'm looking for from the shack is guidance on how to properly use the modeling tools and get the best bang for my buck. I have lots of time since it's cold as hell in the Great White North right now and my garage isn't heated. I plan on starting the box builds in probably March or April. I've used WinISD beta a bit, but other than fiddling with port sizes and tuning, I really don't know what I'm doing or why I'm doing it. Recommendations on other tools and tricks of the trade are much appreciated and I firmly believe that a picture says a thousand words, so images are good. I'm relatively intelligent, but if things get too technical my brain may fall out, so feel free to talk to me as if I'm your slow cousin or an advanced 10-year-old. :R
 

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Elite Shackster
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Are you using one Atlas in each enclosure?

Looks like you've got enough room in that box for an LLT subwoofer. An LLT is a ported sub that is tuned very low. The result is the deepest, loudest and arguable cleanest bass of any design. A good write up of it can be found here.

There's a great users guide to WinISD here.

How are you planning to power them?
 

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A pair of Atlas 15's in 20 cu.ft. tuned to 18 hz looks good. With 600 watts input power the SPL is 117 db at 20 hz.

Atlas 15.JPG

I have a pair of Atlas 15's each in 10.5 cu.ft. tuned to 17.5 hz with two 4 inch flared ports 18 inches long. They are powered by 270 watt plate amps.

PC120006.JPG

PC120005.JPG

My HT in in the basement on a concrete floor. With the Atlas subs there wasn't much tactile effect. The solution was a pair of IXL-18's in 12 cu.ft. tuned to 16 hz. Placed against the back wall and combined with the Atlas 15's I'm now happy with the low end.

PC130001.JPG

PC130002.JPG
 

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Discussion Starter #6
Are you using one Atlas in each enclosure?

Looks like you've got enough room in that box for an LLT subwoofer. An LLT is a ported sub that is tuned very low. The result is the deepest, loudest and arguable cleanest bass of any design. A good write up of it can be found here.

There's a great users guide to WinISD here.

How are you planning to power them?
I'm planning on two subs on each side. Now, whether that's 2 subs in one enclosure or two enclosures stacked up or some other setup is up for debate. Thanks for the links, I'll be sure to give them a read. My current box is 16 cuft tuned to 17Hz I think. I plan on powering them with my EP2500, but the exact method of wiring is also what I'm here to learn. I have the single sub now in mono.
 

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That can be controlled with damping material applied to both ends of the cabinet.
An internal dimension of 84 inches will act as a 1/4 wavelength resonator at 40 Hz, which no damping material can suppress. The way to eliminate the standing wave is to make one end of the enclosure at an angle, so there are no parallel surfaces.
An LLT is a ported sub that is tuned very low. The result is the deepest, loudest and arguable cleanest bass of any design.
An enclosure of that size would be seriously outclassed in output by a folded horn of the same or even smaller volume. As for distortion, no direct radiator comes within spitting distance of a folded horn.
 

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Discussion Starter #8
Mike, that's an impressive setup. I will admit, I've seen some of those pics before while surfing around here. My theater is also in the basement, but I'm hoping the 4 Atlases will do the deed. The single IXL shakes the couch a bit on occasion :D

Eddie: I am also concerned about resonances but have been told a couple times that damping will help. However, would the problem go away completely with 2 enclosures stacked on top of one another? At this point I don't know which is the best way to go.

Thanks for the responses guys. I'll go do some reading.
 

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Discussion Starter #9
An internal dimension of 84 inches will act as a 1/4 wavelength resonator at 40 Hz, which no damping material can suppress. The way to eliminate the standing wave is to make one end of the enclosure at an angle, so there are no parallel surfaces.
Sounds simple enough. I can easily tilt the base or top surface to create an angle.

An enclosure of that size would be seriously outclassed in output by a folded horn of the same or even smaller volume. As for distortion, no direct radiator comes within spitting distance of a folded horn.
Can your average or even better than average DIY'er build a folded horn? Also, the box volume isn't cast in stone I can increase or decrease as needed. I realize that there isn't a smoking gun here too. One box won't be able to hit 5Hz AND 130dB. Low usually sacrifices output... output usually sacrifices depth. And then there's the sub parameters in the mix too. At least I think that's what I've read.:scratchhead:
 

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Can your average or even better than average DIY'er build a folded horn?
There are folded horns designed for ease of assembly. The vast majority of those who've done them were first time builders.
One box won't be able to hit 5Hz AND 130dB.
True. Whether there's any point in 5 Hz response is a matter of opinion. It's not mine.
 

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I originally had sonotubes that were 78 inches tall. There were no resonance issues with a foot of fiberglass insulation stuffed at the port end. With your cabinets being 6 inches taller and square instead of round maybe that changes things somehow, according to Bill's statement.
I'd have to see your design to render an opinion, but that tube would have had a resonant mode at 45 Hz or so, and 45 Hz will go through a foot of fiberglass as if there's nothing there. But depending on the rest of the design topology that resonance might not have been either noticeable or detrimental. A long vented tube is after all the basis for a MLTL.
 

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Discussion Starter #13
With your cabinets being 6 inches taller and square instead of round maybe that changes things somehow, according to Bill's statement.
Don't forget that the enclosures are not cubic. They'll be triangular, or more accurately, pentagonal.

Whether there's any point in 5 Hz response is a matter of opinion. It's not mine.

I don't think there's any point in 5Hz either. I was just trying to use two extremes. But I probably should have said 230dB at 5Hz :bigsmile:
 

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Eddie: I am also concerned about resonances but have been told a couple times that damping will help. However, would the problem go away completely with 2 enclosures stacked on top of one another? At this point I don't know which is the best way to go.
Sorry, I don't know the answer to that. Though I wouldn't think so.
I just mentioned it so you didn't spend too much time considering the project without realizing some of the downsides to it.
 

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Elite Shackster
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Eddie: I am also concerned about resonances but have been told a couple times that damping will help. However, would the problem go away completely with 2 enclosures stacked on top of one another? At this point I don't know which is the best way to go.
Splitting the enclosures would increase the resonant mode by 2X. Boxnotes is free and will tell you what resonant frequencies could become an issue. With a standard 80hz crossover you're pretty safe down to about 120hz.

4 atlas's?! Should be impressive! Do you have the T/S parameters handy?
 

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Discussion Starter #16
Splitting the enclosures would increase the resonant mode by 2X. Boxnotes is free and will tell you what resonant frequencies could become an issue. With a standard 80hz crossover you're pretty safe down to about 120hz.

4 atlas's?! Should be impressive! Do you have the T/S parameters handy?
Thanks for the boxnotes link. I'm hoping 4 15s will be impressive. :yes: I found some T/S parms on another forum (via Google search). But... they list a Low, Mid and High QTS. Absolutely no idea what's for what.
 

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The Atlas subs have 2 voice coils, one with gold colored terminals and one with silver colored terminals. You apply power to the silver terminals, NEVER the gold ones. You control the Qts of the sub by closing, leaving open, or wiring in a 1.5 ohm resistor to the gold colored terminals.
 

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Discussion Starter #18
Cool... playing with WinISD is fun. I've got a 22 cu/ft box, tuned to 18.5Hz. The original pic I posted above from Sketchup had the volume wrong. It's a bit over 22 cu/ft, not 20 and change. I started to look at the port airspeed graphs and had to throw in 3 6-inch ports just over 25 inches long to get it under the recommended 20-25 m/s.

I put the T/S parameters in for the Low Qts settings. I have to brush up on my wiring math so I can figure out how much power I'll be feeding these guys with my EP2500 with various wiring configurations.
 
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