B.M.D. - Beast Mode Devastator - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 124 Old 07-15-2019, 06:16 AM - Thread Starter
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B.M.D. - Beast Mode Devastator

Another version of the Devastator that is geared for 20Hz to 80Hz, it should hit with a lot of authority in that range. Response rolls off around 70Hz, integration with higher crossovers should still be possible, but not as ideal. The additional height allows for a long front chamber which pushes the response of the resonator down a bit. Also the rear chamber gets added volume which helps pick up the low end. I tuned it a little higher since I would rather have the added SPL vs the extension. I can add port lengthening information if anyone is interested pushing the tune down. For this design a pillow should be added between the braces just below the sub woofer since the 48 inch mark has been breached by more than a little Power handling on the B&C 21DS115-8 is around 1625 watts (91 volts) which pushes excursion to its max and port velocity to 25m/s. 8.25 inches added to the port brings the tune down a bit under 19Hz if you want the added extension. Graph attached on the bottom of the post.












BMD vs Devastator 1w1m


BMD vs Stormbreaker (11cuft, 18Hz tune) 1w1m


BMD 91volts into 5.1 Ohms 19Hz 3rd order HPF pushing 20mm of excursion over under tune






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Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
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Last edited by Red Five; 07-17-2019 at 01:17 PM.
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post #2 of 124 Old 07-15-2019, 06:17 AM - Thread Starter
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Exclamation

This is the LaVoce SAN214.50 vs the B&C 21DS115-8 at 1w1m.

Dayton PA460 vs B&C 21DS115-8 1w1m



Alternate bracing structure using waste material














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Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
7.1.4 | Yamaha A3070 | Crown XLS 1502 | iNuke 3000 DSP | 2x Aphex 124A | 2x Bic EV15 | 7x Bic FH6 LCR | 2x Bic FH65-B | Epson 5010e | 120" DIY AT Screen

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post #3 of 124 Old 07-15-2019, 07:50 AM
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B.M.D. Plywood Dimensions

Dimensions have been verified using FreeCad along with @Red Five . This assumes the thickness of 0.688" plywood however the difference of dimensions are also included which should make it very easy to convert to any plywood dimension you wish.

Left Side of the attachment are the original dimensions. Right side is the converted dimensions.
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post #4 of 124 Old 07-15-2019, 07:56 AM - Thread Starter
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Quote:
Originally Posted by superkyle View Post
Outstanding work. Design looks outstanding. Looks like I will be building two of these


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Looking forward to seeing some pictures

Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
7.1.4 | Yamaha A3070 | Crown XLS 1502 | iNuke 3000 DSP | 2x Aphex 124A | 2x Bic EV15 | 7x Bic FH6 LCR | 2x Bic FH65-B | Epson 5010e | 120" DIY AT Screen

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post #5 of 124 Old 07-15-2019, 09:23 AM
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Looking forward to seeing some pictures


Will do a build thread for sure


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post #6 of 124 Old 07-15-2019, 09:24 AM - Thread Starter
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Originally Posted by superkyle View Post
Will do a build thread for sure


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I added a lower tune version. Graph is attached on the bottom of the OP. 8.25 inches to the port brings it down a little under 19Hz.

Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
7.1.4 | Yamaha A3070 | Crown XLS 1502 | iNuke 3000 DSP | 2x Aphex 124A | 2x Bic EV15 | 7x Bic FH6 LCR | 2x Bic FH65-B | Epson 5010e | 120" DIY AT Screen
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post #7 of 124 Old 07-15-2019, 09:30 AM
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B.M.D. - Beast Mode Devastator

Quote:
Originally Posted by Red Five View Post
I added a lower tune version. Graph is attached on the bottom of the OP. 8.25 inches to the port brings it down a little under 19Hz.


Yeah I think since I’m building two of them that may be the way to go. Capture as much low end as I can. I don’t think I’ll be left wanting on the 20+Hz range with either lol


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post #8 of 124 Old 07-15-2019, 09:36 AM - Thread Starter
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Quote:
Originally Posted by superkyle View Post
Yeah I think since I’m building two of them that may be the way to go. Capture as much low end as I can. I don’t think I’ll be left wanting on the 20+Hz range with either lol


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If you are on a suspended floor I would say go for the extension. I am on a slab of concrete, chasing low frequencies requires stupid amounts of displacement to make it really worth it.

Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
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post #9 of 124 Old 07-18-2019, 05:35 AM - Thread Starter
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@superkyle


There is still more fine detail work left, but this is roughly what MDF bracing will look like. It saves 28.1 liters of displacement and uses a good amount of scrap material vs picking up additional wood. Tune then comes in at 19.8Hz and adds a slight bit more SPL down low.



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Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
7.1.4 | Yamaha A3070 | Crown XLS 1502 | iNuke 3000 DSP | 2x Aphex 124A | 2x Bic EV15 | 7x Bic FH6 LCR | 2x Bic FH65-B | Epson 5010e | 120" DIY AT Screen
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post #10 of 124 Old 07-18-2019, 05:45 AM
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Nice that’s basically 1 ft3 saved with same dimensions. Did you end up deciding to keep it the same size? Waiting on the final dimensions before going through and calculating and posting up the conversion to using plywood.


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post #11 of 124 Old 07-18-2019, 06:18 AM
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Quote:
Originally Posted by superkyle View Post
Nice that’s basically 1 ft3 saved with same dimensions. Did you end up deciding to keep it the same size? Waiting on the final dimensions before going through and calculating and posting up the conversion to using plywood.


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I’ll be waiting for this^^^^^. I am planning on using Baltic birch to build my 2.
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post #12 of 124 Old 07-18-2019, 06:24 AM - Thread Starter
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If I took an inch off it would be down to 346 liters vs the 414 liters, so I think leaving it at 28 inches deep is a good option. Especially if permission is already there

I am out and about I have to look at the notes, math seems off.

Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
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post #13 of 124 Old 07-18-2019, 07:01 AM - Thread Starter
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I made a typo in the unit converter 21 liters of added displacement, so about .75cuft. An inch off will take it down to 379.7 liters vs the 407.5liters. There would be a few liters added on due to shorter bracing, but this will be in the ballpark. What do you guys think? Once I get down to 24 inches deep things really go down on the low end lol.

@superkyle @Purenv


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Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
7.1.4 | Yamaha A3070 | Crown XLS 1502 | iNuke 3000 DSP | 2x Aphex 124A | 2x Bic EV15 | 7x Bic FH6 LCR | 2x Bic FH65-B | Epson 5010e | 120" DIY AT Screen

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post #14 of 124 Old 07-18-2019, 09:43 AM - Thread Starter
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Quote:
Originally Posted by superkyle View Post
Nice that’s basically 1 ft3 saved with same dimensions. Did you end up deciding to keep it the same size? Waiting on the final dimensions before going through and calculating and posting up the conversion to using plywood.


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Quote:
Originally Posted by Purenv View Post
I’ll be waiting for this^^^^^. I am planning on using Baltic birch to build my 2.

Post two is updated with MDF bracing cut list. Depth remains at 28". Does anyone want to double check my numbers?

Stormbreaker | Wisconsin Home Theater Meet Thread | The Devastator Index
You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
7.1.4 | Yamaha A3070 | Crown XLS 1502 | iNuke 3000 DSP | 2x Aphex 124A | 2x Bic EV15 | 7x Bic FH6 LCR | 2x Bic FH65-B | Epson 5010e | 120" DIY AT Screen
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Quote:
Originally Posted by Red Five View Post
@superkyle


There is still more fine detail work left, but this is roughly what MDF bracing will look like. It saves 28.1 liters of displacement and uses a good amount of scrap material vs picking up additional wood. Tune then comes in at 19.8Hz and adds a slight bit more SPL down low.




Love the new design, somehow seems a lot easier to build from this pic. Don’t cut the low end off too much. As you said chasing extension isn’t worth it in your situation, I’m still a fan of reaching for powerful 20Hz content in large rooms and hard floors.

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B.M.D. - Beast Mode Devastator

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post #17 of 124 Old 07-18-2019, 11:27 AM
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B.M.D. - Beast Mode Devastator

Been tied up at work but loving the new design. I’ll compare the numbers when I convert them to plywood measurements like I did before.

Edit: I see the difference now have to zoom in haha.

Yeah permission was key. Now that I have it I want as much low end as possible while maintaining the mid bass. I’m thrilled with the new design.

Never tried window bracing so may have some questions but I plan to document everything in a build thread as how this goes together can seem a bit tricky. Kreg jig for the win!

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post #18 of 124 Old 07-18-2019, 11:49 AM - Thread Starter
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I have to make one adjustment on the upper frame brace, I forgot that one is shorter.

All you do is mark 2 inches lines around the diameter and then two lines 11.25" from the outside edges. That will leave 2 inches of material in the center of the frame. Then cut down the boxes with a jig saw.

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You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
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post #19 of 124 Old 07-18-2019, 12:18 PM
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Quote:
Originally Posted by Purenv View Post
I’ll be waiting for this^^^^^. I am planning on using Baltic birch to build my 2.


Good someone that is going to build it with me that can check my numbers haha


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post #20 of 124 Old 07-18-2019, 12:19 PM
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Quote:
Originally Posted by Red Five View Post
I have to make one adjustment on the upper frame brace, I forgot that one is shorter.

All you do is mark 2 inches lines around the diameter and then two lines 11.25" from the outside edges. That will leave 2 inches of material in the center of the frame. Then cut down the boxes with a jig saw.


Doesn’t sound bad at all. I’ve got all the tools and no reason to rush so should go together without any issues. Just got to get the dimensions correct


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post #21 of 124 Old 07-18-2019, 12:37 PM
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Another version of the Devastator that is geared for 20Hz to 80Hz, it should hit with a lot of authority in that range. Response rolls off around 70Hz, integration with higher crossovers should still be possible, but not as ideal. The additional height allows for a long front chamber which pushes the response of the resonator down a bit. Also the rear chamber gets added volume which helps pick up the low end. I tuned it a little higher since I would rather have the added SPL vs the extension. I can add port lengthening information if anyone is interested pushing the tune down. For this design a pillow should be added between the braces just below the sub woofer since the 48 inch mark has been breached by more than a little Power handling on the B&C 21DS115-8 is around 1625 watts (91 volts) which pushes excursion to its max and port velocity to 25m/s. 8.25 inches added to the port brings the tune down a bit under 19Hz if you want the added extension. Graph attached on the bottom of the post.












BMD vs Devastator 1w1m


BMD vs Stormbreaker (11cuft, 18Hz tune) 1w1m


BMD 91volts into 5.1 Ohms 19Hz 3rd order HPF pushing 20mm of excursion over under tune






Can a cab exist with max of 20"depth, 24 width and flexible height , I would definitely go for the build as I just received my 21s today.
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post #22 of 124 Old 07-18-2019, 12:44 PM
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Can a cab exist with max of 20"depth, 24 width and flexible height , I would definitely go for the build as I just received my 21s today.


So I originally was looking for something similar and decided on this build. Basically when you change things up to those dimensions you lose a lot of efficiency and a ton of output. A couple inches hopefully won’t be too bad bc the output is on another level!


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post #23 of 124 Old 07-18-2019, 12:56 PM - Thread Starter
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Can a cab exist with max of 20"depth, 24 width and flexible height , I would definitely go for the build as I just received my 21s today.

I would have to play with it, but the resonator needs to be about 225in2, that would be 10 inches deep on 25.5in wide and the driver is 10 inches deep, so that would be 20 inches right there not counting cabinet material. When the resonator gets less cross sectional area the response flattens out and it becomes less efficient. Minimum is around 25.5in wide and 24in deep with that width.

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post #24 of 124 Old 07-18-2019, 01:25 PM
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Where I stand is my jbl 4722 are 18" depth so I will projecting 2" more just by going 20". So I always try to get the cab a max of 18" to not waste even a few inches.
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post #25 of 124 Old 07-18-2019, 01:33 PM
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EDIT: Dimensions Verified using FreeCAD. New image updated to reflect accurate Plywood Cutlist.

Note: This assumes the standard thickness of 0.688" that is the nominal thickness of Arauco Plywood. Ensure your plywood is the same nominal thickness else corrections to your cut list will be required.
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Always destroying exergy!

Last edited by superkyle; 07-21-2019 at 08:16 AM.
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post #26 of 124 Old 07-18-2019, 01:34 PM
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I would have to play with it, but the resonator needs to be about 225in2, that would be 10 inches deep on 25.5in wide and the driver is 10 inches deep, so that would be 20 inches right there not counting cabinet material. When the resonator gets less cross sectional area the response flattens out and it becomes less efficient. Minimum is around 25.5in wide and 24in deep with that width.
Those dimensions are workable in my seutp, but how does it compare with original cab and if I happen a build basic ported sub that LTD02 designed here
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post #27 of 124 Old 07-18-2019, 01:47 PM
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Does something like this work ?
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post #28 of 124 Old 07-18-2019, 02:44 PM - Thread Starter
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Does something like this work ?
I will take a look later when I get a chance concerning the comparison. That would be a traditional 6th order parallel band pass, but it would not work the same way in which a Devastator does. The front chamber is a quarter wave resonator, not a Helmholtz resonator. The length and diameter effects the response, not the port length and volume, at least on the mid and upper end of the response.

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You can always turn it down, but you can only turn it up so much (before you run out of power, excursion or structural integrity).
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post #29 of 124 Old 07-18-2019, 03:00 PM
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Quote:
Originally Posted by Red Five View Post
I will take a look later when I get a chance concerning the comparison. That would be a traditional 6th order parallel band pass, but it would not work the same way in which a Devastator does. The front chamber is a quarter wave resonator, not a Helmholtz resonator. The length and diameter effects the response, not the port length and volume, at least on the mid and upper end of the response.
Understood. thanks!
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post #30 of 124 Old 07-18-2019, 03:38 PM
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Can a cab exist with max of 20"depth, 24 width and flexible height , I would definitely go for the build as I just received my 21s today.

Depending on what type of design you’re looking for, my recent slim slot port build with a 21” driver is only 16” deep x 24” wide x 72” long, adding another 4” depth if going to 20”, and I bet you could shave a foot or two off the length. It’s 10cu ft net.

https://www.avsforum.com/forum/155-d...n214-50-a.html
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