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Discussion Starter #1
I've been wanting to build a Devastator for some time now. Recently @chadsmith013 was kind enough to hook me up with a couple LaVoce SAN214.5 21s. These will be the first step in a complete renovation of my theater. The plan is to build a false wall with a 110" 2.35:1 Spandex AT screen. 1099 LCR, two Devastators and two HS24s in 18ft^3 tuned to 17Hz. Two Crowsons and a sealed HS24 will be nearfield. I won't be going over the top with the finish on any of these builds. Just some simple DuraTex.
 

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Discussion Starter #2
I was able to get all the cuts made Friday after work, right before the storms rolled in. This is my first Devastator build, so assembly was challenging. I started assembly from the top and worked my way from the front to the back. This turned out to be completely wrong. I was still able to get it finished Saturday, but it was a PITA. I started the second one from the bottom and worked my way out from the baffle to the back. Once the back section was complete, I worked out from the baffle to the front. This turned out to be much easier and faster. I finished the second one Sunday with enough time left in the day to get the first one loaded with the driver and setup in the theater. I'll hold my impressions until they are both in the theater with EQ. The pictures are in the order of assembly.
 

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i am nice like that
 

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Wow!
 
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Discussion Starter #6
Ok, the 99s will have stands soon enough, calm down. Eventually the Mystery Box will be gone and all the AV gear will be in a closet. The Devastators sound pretty good. There's one song in particular that these things really wake up on. @Red Five told me they wouldn't play well with my sealed 24s, he wasn't wrong. I didn't even attempt to EQ them, just delay. I might get started on the ported cabinets for the 24s this weekend. Before I pull them out of their cabinets, I'll put them on the front wall and do some REW measurements and play a few of my demo songs. A few friends want to know how a Devastator will compare to a sealed 24.
 

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Ok, the 99s will have stands soon enough, calm down. Eventually the Mystery Box will be gone and all the AV gear will be in a closet. The Devastators sound pretty good. There's one song in particular that these things really wake up on. @Red Five told me they wouldn't play well with my sealed 24s, he wasn't wrong. I didn't even attempt to EQ them, just delay. I might get started on the ported cabinets for the 24s this weekend. Before I pull them out of their cabinets, I'll put them on the front wall and do some REW measurements and play a few of my demo songs. A few friends want to know how a Devastator will compare to a sealed 24.
Just got fun you could see if an BW 10Hz 8th order HPF on the sealed and a BW 20Hz 2nd order HPF on the Devs get a positive summation. Each room will will create different challenges. The goal is getting the woofers to be in phase on the bottom end vs out of phase and cancelling each other out. Sealed does not have a phase shift like a BR sub.
 

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Just got fun you could see if an BW 10Hz 8th order HPF on the sealed and a BW 2nd order HPF on the Devs get a positive summation. Each room will will create different challenges. The goal is getting the woofers to be in phase on the bottom end vs out of phase and cancelling each other out. Sealed does not have a phase shift like a BR sub.

I had to also use a very steep lpf on the sealed IIRC. Its in my mini dev build.
Not ideal, but might work.

Chris
 

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Tarp, do you have the side panel pillows installed? The standing waves are 60" of height are getting really close to the pass band on these.
 

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Discussion Starter #10
Tarp, do you have the side panel pillows installed? The standing waves are 60" of height are getting really close to the pass band on these.
I put some poly fill in the lower section.
 

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Should help. Once its ready, give it a close-mic to check for nasty resonance issues if possible.

Chris
Do you still have Jared's graph without the pillows?
 

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Dual 21" BMD Shallow HCR build

Do you still have Jared's graph without the pillows?



No pillow and one pillow (poorly placed) are Jareds. Two pillows is mine. Don’t worry about the choppiness of his measurements, not sure what was going on there.
Just notice the severe resonance at 110hz, and how pillows mitigate it.

Chris
 

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Discussion Starter #14
Those HP filters helped a lot. My crossover range still looks like a heart attack, but that's probably something I'll just have to live with.
 

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Discussion Starter #16

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Discussion Starter #17
The original design was a full subwoofer. My 24s can handle the ULF duty so I asked @Red Five if he could come up with a mod to the cabinet that would make it an MBM. He came up with a very simple solution. Basically just shorten the front chamber. Then I opened the section of the front chamber that was blocked off so that it's volume became part of the rear chamber. The way in which I decided to go about turned out to be more of a PITA than I expected. I will be doing the second cabinet differently. I plan on cutting out the lower section, installing the plugs. Cut out the holes to the rear chamber, then glue on a new outer panel. I'll just have to be careful not to damage the front rails when I pull off the front panel.
 

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The original design was a full subwoofer. My 24s can handle the ULF duty so I asked @Red Five if he could come up with a mod to the cabinet that would make it an MBM. He came up with a very simple solution. Basically just shorten the front chamber. Then I opened the section of the front chamber that was blocked off so that it's volume became part of the rear chamber. The way in which I decided to go about turned out to be more of a PITA than I expected. I will be doing the second cabinet differently. I plan on cutting out the lower section, installing the plugs. Cut out the holes to the rear chamber, then glue on a new outer panel. I'll just have to be careful not to damage the front rails when I pull off the front panel.
It's a tough modification, but you pulled it off!
 

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Discussion Starter #19
This way was much easier. It took four hours on the first cabinet, but only 1.5 hours on the second one.
 

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Discussion Starter #20
Painted and ready for some REW sweeps. Soon, the Mystery Box in the center will be gone. The Devastators will be moved to the center flanking the center channel. Then two very large cabinets will fill the rest of the wall. They will be 18ft^3 net tuned to 17Hz. The main chamber will house an HS24 and a secondary chamber will have the 1099s in them. When it's finished, it will look like a ported 24 next to a 1099 on a speaker stand. Then the entire wall will be covered in spandex panels.
 

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