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Devastator an LTD02 hybrid design

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devastator
151K views 1K replies 83 participants last post by  Ryanosaur 
#1 · (Edited)
Who said big bass does not come in “smaller” packages? :D


THE MINI DEVASTATOR 40"x25.5"x24" FOUND HERE


NOTE: THERE IS A LARGER LFE VERSION FOUND HERE


SAF 184.03/18" PRO MORE FRIENDLY VERSION HERE


The design is a 6th order bandpass non flared horn contributed by @LTD02, a big thanks for his work on this project!

The design found its roots in an outdoor sub project that just so happened to play very nicely with the B&C 21DS115. The tune has been dropped slightly to aid with HT, still very capable at delivering music at high levels. More bracing has been added to endure the added pounding of a 21DS115 or similar sub. This design makes very efficient use of material, similar to a Marty sub in that respect. If you are wondering why so much mid bass, John Wick and for science :)


This is the near-field measurement layered over the top of the model. Driver is a 21DS115-8. A thanks goes out to Dan and John for getting this put together!








Current suitable driver list (Note: an Fs of close to 30Hz and a Qts of .3 or lower appear to be the predominating factors if a driver will work or not)

Alpine:
-SWS-15

B&C:
-21DS115
-21SW115
-21SW152
-18DS115
-18SW115
-18TBW100

Beyma:
-18PWB1000Fe
-18PW1400Fe

Dayton:
-PA460

Lavoce:
-SAN 214.50
-SAN 184.03
-SAF 184.03


Stereo Integrity:
-HST-15



Added bonus for me at least, the sub is nestled safely out of the reach of adventurous toddlers.

Dark gray - Devastator, light gray - ported enclosure
As you can see there are efficiency gains across a wide range 20 - 110Hz, (though I would probably cross at 80Hz to 100Hz) more efficiency in the upper mid bass range than the lower end. As John Madden would say in Madden 96, “That outta clean out the sinuses!”


Simulation based on the 21DS115







Can it be tuned lower?

Chrapladm
"And now that I think of it. Just leave the cabinet the way it is. If you want a lower tune plug a port. 2 ports is about 15.75hz roughly. When just plugging the end of the port that gives an extra 10 Liters roughly also. And because I know someone will ask, a single port is about 11hz tune. Doesnt look very good with the 15SWS.

So I would keep the cabinet the dimensions and just build yourself some small port plugs if you want. This is what I will be doing. No need to change cutlist or any dimensions
."


The enclosure is not all that large relative to a tapered horn design or a lot of other things around here :)





Just give me the darn cut list! Here it is! Do not forget to take a notch out of the front port braces leaving space for excursion. Two full sheets of MDF (97"x49") and five 2”x4”s are all that is required. If using plywood double check the dimensions of your material. MDF can also vary in size, if it is NOT 97x49 it is not fitting on two sheets of material.





















Assembly, we suggest building from the side, then from the front towards the back. Attach the front panel and top. Use lots of glue/loctite, this needs to be airtight.


















Brad suggestion, not scale.
































Attach the bracing assembly all as one unit. A lot of weight or some long screws might come in handy. If you want the hatch to sit flush, take the height of the gasket off of the 2x4s on the upper half of the bracing assembly.





Attach the back panel, add the sub, add the speaker terminal, attach wire and close the hatch. Next, test your neighbor's pain tolerance\structural integrity :)




Amp suggestion: An iNuke6000D/NX6000D will not have a problem driving two, one on each channel. The high pass filter should be set at 18Hz using the high shelf work around solution on the amp's DSP. There is not a preset filter for reducing the two peaks at the moment. The peaks should be around 20Hz and 70Hz. REW and the built in DSP will be able to clean up the peaks.



More detailed information is attached in the at the bottom of the post. This is a horn loaded design, making it airtight is crucial, use lots of glue/loctite.


Devastator

-John
 

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#14 ·
And any observations/measurements or impressions after testing when complete, even if only purely subjective.

Excellent design. @LTD02 is mad helpful to those on this forum.:)


"I forgot what the gasket tape suggestion is for the 21DS115, ..."

FWIW, gasket tape can be bought at hardware stores. Ace, Home Depot, etc.
 
#7 ·



:D


Make sure you build the hatch hole large enough to fit the driver through.

The cutlist will only work with MDF for anyone looking. You won't get two 24" panels out of plywood.


I'm curious to see a measurement once one of these is up and running. I wonder what if any benefit there would be to angle the panel in front of the driver to make this more similar to the skhorn.
 

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#13 ·
Make sure you build the hatch hole large enough to fit the driver through.

The cutlist will only work with MDF for anyone looking. You won't get two 24" panels out of plywood.


I'm curious to see a measurement once one of these is up and running. I wonder what if any benefit there would be to angle the panel in front of the driver to make this more similar to the skhorn.
with no other changes, reducing throat to about 1/2 the size of the exit has the effect of pushing the efficiency peak up in frequency. i kind of thought that it was good where it was, so i didn't change it. different shapes and lengths have various advantages and disadvantages.
 

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#9 ·
The red circle is showing brads coming in at an angle to hold the panel in place. You can't come at it flush due to the brace on the other side.



I forgot what the gasket tape suggestion is for the 21DS115, I have a lot left over from the first sub project. I picked it up on Parts Express.
 
#11 ·
To speed up assembly I picked up a brad nailer cheap. Brads and Premium Loctite 3X is what I am planning on using for assembly after conversing with John. Drilling and counter sinking takes a lot of time. I did that on my first sub :)
 
#25 ·
OSB flexes much more than Arauco or Baltic Birch ply does. If you use that, make sure you use extra bracing. And it is more brittle as Trimlock noted.

Personally I would look at a different material for a sub build of this size.
 
#105 ·
might be worth noting that this cab doesn't really work with the 460HO and UM18 drivers. they just give a huge narrow peak around 70hz. not a smooth response at all. will have to find something else for those drivers. :)

So..... What you working on for the RS460? Do tell......:D:D:D


And thank you for all your great contributions to this group.



Juju
 
#34 ·
What are your collective thoughts on the pluses and minuses of this design versus a full marty? The marty has one advantage that I know of -- you can buy an off the shelf box that's easy to put together. The devastator has its own advantage -- it hides the driver, which will protect it from teenagers running around my theater room.
 
#35 ·
What are you thinking of loading the full Marty with? I pushed the Stormbreaker a bit for practicing some music. It is nuts, but I am mostly in this for driver concealment. The added sensitivity and potential for cranking music to another level is just icing on the cake :)
 
#36 · (Edited)
If I were to buy full marty flat packs, I think I'd load them with UM 18-22s. I've also looked at building ported cabinets for B&C drivers, but this one caught my eye because, as you said, it protects the drivers. As a layperson, I don't really understand the trade offs associated with one choice versus another. For example, this design is tuned to 19 Hz. Does that create performance trade offs versus a design tuned at 17? These are all just hypothetical numbers with no real world meaning to me. And I certainly don't have the time or money to build three or four different designs to test them out. ;)
 
#37 · (Edited)

This calculated 1w1m on the Devastator





Calculated 1w1m on the UM18 full Marty


On the bottom end the sensitivity is fairly close and the curve down to 10hz is close. Once we start heading north of 20hz the Devastator finds all sorts of efficiency. What this translates to in the HT setting will be slam factor. The UM18 will need something to assist it in the mid bass if you want to feel gunshots in the chest. The Devastator will have mid bass to the point it needs to be settled down. If you dump 2000 watts into each one, both will be close to 120db at 20hz. At 50Hz the UM will be around 120db with 2000 watts, but the Devastator will be close to 130db at 50Hz with 2000 watts.
 

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#39 ·
A UM puffing magic smoke from attempting to push mid bass has happened. If you do a UM you will want to do something for handling mid bass, like a 31Hz tuned VBSS.
 
#41 ·
I would appreciate guidance on three more topics if I haven't worn out my welcome yet with my subwoofer ignorance: (1) How do you mount the speaker? Do you just screw it in from the back? Do you need gasket tape between the wood and the front of the speaker's rim? (2) How much do you need to shave off the panel in front of the driver to allow room for excursion? (3) How do you recommend powering a pair of these?
 
#42 ·
It will be from the back. I am going to cut 8 2in chunks of 2x4 and glue them to the front of the baffle. That will give the #8 screws something to dig into that will not go anywhere. The front braces might get in the way a little bit, but that can be worked around. The B&C has a rubbery material on the front side of the flange, it should make for a good seal against the MDF. I was going to run that past John though before I mounted it... If you took an 1 1/4 plus the 3/4 from the MDF would give you 50mm of travel to the braces, an inch off the braces would be 44mm. The sub would have other problems if pushed that far :) A jigsaw will do just fine for cutting the MDF off the front braces. An iNuke or NX 6000DSP will have no issue powering a pair of these 4 Ohm or 8 Ohm :)
 
#43 ·
Has anyone completed one of these yet?

I could use some opinions. I have 4 PA460s and was planning on building 2 VBSS under my fronts and 2 near-field behind the couch but now I am tempted to build 4 of these Devastators. I have knee walls (mini attics) on each side of my home on the 2nd floor. I could make 4 cutouts in the living room ceiling, lay them facing down into the room, and cover the holes with some vent covers.

I have 2x6 plus plaster so it is about a 7" path through the ceiling joists into the living room. Will this change the tune or sound?

I know this will limit my placement but it will be a huge bonus hiding them out of sight since this is our living room/kitchen. Please let me know what you think.
 
#44 ·
I have not seen a build for one just yet. I know a few members were talking about building in January once the holiday madness subsides. My build is looking like May, potentially later. The 7 inch path could lower the tuning, depending how close the boundaries are to the vent. For a slot port design like a Marty with the floor as a boundary on one side the tune goes down very little, a hertz or so. Having at least two boundaries near the vent, the effect would probably be more, not sure how much more. You could always build one and make a smaller mock up of the joists/ceiling. Then measure the results without destroying the house. That would be the scientific way :) I would not recommend hammering holes in the ceiling first then asking questions later...
 
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