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Discussion Starter #1 (Edited)
Well the time is here to let the dust fly! Well into the suction hose :cool: But I have procrastinated long enough and it's time to start acting! I can hear the "Amen's" already lol. This was only my third whole 2 day weekend since mid August as work and other obligations went crazy then in laws for Thanksgiving. I'm sure I will miss some points but I will do my best. The plan is to have these two ported subs up front behind the screen on either side of the JBL 4722 center channel and obviously the L&R 4722's on outside of the FTW cabs. It will essentially be a solid horizontal baffle all across behind a planned 12ft acoustically transparent screen. Of course a couple inches in between all enclosure wall whether it be speakers or subs.

First off I have to give credit where credit is due. Jon (LTD02) has designed these cabs. I know several AVS-ers who have had Jon's help and certainly he is great on the forums. So MUCH THANKS to Jon for working with me on this and enduring my onslaught of questions :)

Specs
-18 cubic feet before driver and bracing
-15.7hz port tune
-24"x24"x76" final cab dimensions. Foot print is same as most do with sealed cabs at 24"
-Each of the two cabs will each their own channel from a Crest Pro Lite 7.5.
-Finish, not sure yet if I want to do Duratex or just paint black. They will be hidden so...
-Mini DSP to EQ
-Nuetrik NLM4PR connectors



Cut list will follow the mini marty style but obviously taller :)

 

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Nice design once again, Hjon!

Maybe some window bracing like a tic-tac-toe board every 10" up the box with four 10" vertical braces between each window connecting them which would brace it top to bottom.


I made some cross bracing for this box below since I was wanting to use up scrap (probably went overboard with the amount). It would have been easier to cut windows out of a full panel:

ImageUploadedByTapatalk1450134210.523008.jpg
 

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Wow subscribed this is going to be sweet set up. I agree with above with the bracing. Just make sure you use plenty of pl adhesive on all the braces so nothing is lose.
Also with you having your slot ports facing out under the screen is a great idea I have mine facing outwards with fabric panels around the screen and the screen still shakes during heavy bass clips.
 

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i may have forgotten to mention that with a tall cab like that you can get internal standing modes/resonances. it wouldn't be a bad idea to stuff a bunch of polyfill pillows in around the center of the cab (the cheap walmart pillows). bracing can by just about anything. dowels/2x2 stock/mdf scrap, etc. the weak part of the panel is in the center. the edges and corners are naturally strong as they are. just make sure that the cabs are as solid as rocks and airtight around the seams. :)
 

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Discussion Starter #11
These are going to be sweet!!

I would do windows where the dotted lines are and then strips connecting them then maybe a half window against the top
Nice design once again, Hjon!

Maybe some window bracing like a tic-tac-toe board every 10" up the box with four 10" vertical braces between each window connecting them which would brace it top to bottom.

I made some cross bracing for this box below since I was wanting to use up scrap (probably went overboard with the amount). It would have been easier to cut windows out of a full panel:

View attachment 1120962
Okay I like the window style bracing at each red dotted line then vertical strips. For making the window pieces I assume one uses a jigsaw? And router if you want to round the edges? I actually can't recall seeing or reading any step by step process.


Can't wait to see measurements once you get the room completed. I like the "small" footprint with volume coming from height.
Yea it will be a long time coming when that actually happens :roll eyes: I won't go Tom Logan style and take a decade! I am hoping two years will give me enough time to build and fund the entire project.
 

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Discussion Starter #12
i may have forgotten to mention that with a tall cab like that you can get internal standing modes/resonances. it wouldn't be a bad idea to stuff a bunch of polyfill pillows in around the center of the cab (the cheap walmart pillows). bracing can by just about anything. dowels/2x2 stock/mdf scrap, etc. the weak part of the panel is in the center. the edges and corners are naturally strong as they are. just make sure that the cabs are as solid as rocks and airtight around the seams. :)
Sounds good, I will take my wife with me to deplete the Eugene Walmart pillow stock :cool:

Yes the final product will be well made. I may not have sub enclosure experience but have used tools my whole working life and have done quite a bit of sealing work as well in numerous applications.
 

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Discussion Starter #13
Wow subscribed this is going to be sweet set up. I agree with above with the bracing. Just make sure you use plenty of pl adhesive on all the braces so nothing is lose.
Also with you having your slot ports facing out under the screen is a great idea I have mine facing outwards with fabric panels around the screen and the screen still shakes during heavy bass clips.
Will do, need to swing by and grab some PL still. I assume it's normal to tack a couple brad nails into the brace from the outside of the box to hold it along with the PL?

Ports were planned that way for sure :)
 

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Okay I like the window style bracing at each red dotted line then vertical strips. For making the window pieces I assume one uses a jigsaw? And router if you want to round the edges? I actually can't recall seeing or reading any step by step process.




Yea it will be a long time coming when that actually happens :roll eyes: I won't go Tom Logan style and take a decade! I am hoping two years will give me enough time to build and fund the entire project.
But Tom did complete it in the end....

I am starting the research and development for a sub system that I will build when i retire from active duty in 2 yrs, 8 months, and 17 days.

I enjoy the R&D part, it's what I do for a living so I get a little obsessed in the details at times. The procurement is an additional, often harder, hurdle.:eek:
 

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Discussion Starter #15
Gonna start tonight!!!

So I was planning on recessing the driver a bit. I like the look and the screen will be not far from the mains and subs. So I was thinking perhaps the double baffle piece on the inside should be at least 1" piece of plywood perhaps maybe a couple 0.75 pieces, thoughts?
 

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The way Jon H drew it up has a single full baffle with another baffle behind it to make 1.5" to screw the driver into. As for recessing, most go with .75" but remember that adds to the total depth and wont make the driver any less close to the screen.
 

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Discussion Starter #18 (Edited)
The way Jon H drew it up has a single full baffle with another baffle behind it to make 1.5" to screw the driver into. As for recessing, most go with .75" but remember that adds to the total depth and wont make the driver any less close to the screen.
Yea we didn't get into discussing recessing the driver much. Originally yes a second 0.75 piece on the inside for 1.50 total. Thats why I mentioned going to a thicker piece but perhaps it may be best to not recess the driver. Any idea how much internal cab volume would be lost recessing it 0.75 and then using two additional 0.75 pieces on the inside? So technically it would be three 0.75 layers. The front baffle cut to recess the driver then two more pieces at the 30" on the inside for a total of 1.50 for screws to grab. But if it screws up volume forget it, these will be ultimately hidden. Not 100% sure if it's right but a random volume calculator online says the 22.5x30x0.75 second baffle piece eats about 0.292 cu ft.

I am not understanding how recessing the driver will not move it away from the screen however deep the recess is. If not recessed then the driver surround sticks out however thick it physically is, if recessed it moves back however far is decided correct?
 

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I am not understanding how recessing the driver will not move it away from the screen however deep the recess is. If not recessed then the driver surround sticks out however thick it physically is, if recessed it moves back however far is decided correct?
All of the recessed drivers I have seen have been an outer baffle. I have never seen someone recess the driver the way your talking about. Not sure how well that would work because if you do that, the only thing really attaching the driver to the enclosure is the PL holding the two inner baffles to it.
 

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Discussion Starter #20
All of the recessed drivers I have seen have been an outer baffle. I have never seen someone recess the driver the way your talking about. Not sure how well that would work because if you do that, the only thing really attaching the driver to the enclosure is the PL holding the two inner baffles to it.
Okay, I see what your saying. I think my confusion was the fact I did not know that 0.75 is the general recess depth people use. I hadn't really thought about a number but was assuming 3/8 to 1/2 inch or so. I agree recessing 0.75 and mounting driver to the smaller internal baffle piece may not be a good idea. Could always add an entire full length external piece if I really want to recess the driver that bad.
 
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