3015lf TH @ 35-40hz but only 20" deep help - Page 5 - diyAudio
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Old 3rd January 2013, 11:28 AM   #41
epa is offline epa  Netherlands
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the front plate is part of the tunnel system,and is needed for this type of box.
the bracings need to be placed in the center of the front>speaker baffle>back pannel,to reduce pannelflex(pannelflex reduces output)
Click the image to open in full size.i would make a brace against the top pannel aswel
for starters set the hpf @ 30 hz as steep as possible.
i think these subs are excurion limmited,meaning excursion limmit wil be reached before the power limmit is reached.
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Last edited by epa; 3rd January 2013 at 11:31 AM.
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Old 3rd January 2013, 07:30 PM   #42
maxo is offline maxo  United States
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Quote:
Originally Posted by epa View Post
the front plate is part of the tunnel system,and is needed for this type of box.
the bracings need to be placed in the center of the front>speaker baffle>back pannel,to reduce pannelflex(pannelflex reduces output)
Click the image to open in full size.i would make a brace against the top pannel aswel
for starters set the hpf @ 30 hz as steep as possible.
i think these subs are excurion limmited,meaning excursion limmit wil be reached before the power limmit is reached.
Hey Epa,
can you do a 3d sketchup pic of how the braces would be placed
i havent build any wood box yet , i can understand the words you say
but cant draw a picture on my brain of it

Excursion limit can be controled with the HPF right ?
Thank Man
Max.
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Old 4th January 2013, 11:56 PM   #43
maxo is offline maxo  United States
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Also,
i attached a hand sketch i made ( excuse my sloppy draw skills )
hand drawing is not my forte

as you can see i have seen somewhere that you can
reinforce a rectangular area with a brace placed in the orientation
shown at the bottom of the pic

Max.
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File Type: jpg 20130104_185105.jpg (901.6 KB, 268 views)
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Old 5th January 2013, 09:24 AM   #44
epa is offline epa  Netherlands
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hi maxo
yes the brace in the sketch helps.
maybe ill find time this week to make a 3d model.
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Old 5th January 2013, 05:42 PM   #45
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Default Stud Walls

maxo,
That is an excellent method of bracing.
Think of it as adding the studs from a stud wall to the panels of your speaker boxes.
If you can glue on good quality 3/4 plywood all the way around on 8" to 12" centers, your box will become super stiff.
.
I recently cheaped out and bought a kit flatpack speaker and although it was made from 18 mm thick, dadoed birch ply, the wood was only 7 plies and when finished the box vibrated like crazy with an automotive 12" woofer installed in it and sealed.
I went back and glued 18 mm X 2" wide strips, using 2 screws per strip, from the outside to hold them till the glue dried, all the way from bottom to top, up the back and across the top too.
I put them on 9" to 10" center to center according to what fit on each wall.
Now the box is solid as a rock.
.
Also, if you have this structure inside a box, it is a great way to add some damping material.
You staple a thin (1/2" to 1" thick) sheet of fiberglass on top of the "studs" so it is held 2" away from the wall.
That gap makes the damping material act slightly differently in a sealed box that has a pressure swing as the air travels through the damping, back and forth and well... without going into it too much, the insulation acts like a heat exchanger which lowers the hysteresis losses in the internal gas and helps to isothermalize the internal gas.


Dave

Google_ regenerator, or regenerative heat exchanger on Wiki
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Last edited by Shadydave; 5th January 2013 at 05:58 PM. Reason: added confusing theory about action of spaced damping material
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Old 5th January 2013, 05:49 PM   #46
maxo is offline maxo  United States
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Quote:
Originally Posted by Shadydave View Post
maxo,
That is an excellent method of bracing.
Think of it as adding the studs from a stud wall to the panels of your speaker boxes.
If you can glue on good quality 3/4 plywood all the way around on 8" to 12" centers, your box will become super stiff.
.
I recently cheaped out and bought a kit flatpack speaker and although it was made from 18 mm thick, dadoed birch ply, it was only 7 plies and the box vibrated like crazy with a car 12" woofer installed in it and sealed.
I went back and glued 18 mm X 2" wide strips, using 2 screws per strip, from the outside to hold them till the glue dried, all the way from bottom to top, up the back and across the top too.
Now the box is solid as a rock.

Dave
Hey Dave,
what about some solid wood for braces, can that bring benefit ?
instead of plywood,like those 2x4 wood but i think 1x2 will suffice
as the 2x4 will rob too much of the internal volume...
just a tought
Max
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Old 5th January 2013, 06:03 PM   #47
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Oops..You got ahead of me.
Yea, anything is better than nothing.
Ply is allot stiffer in the bending direction, and there are woods that are way stiffer than Pine one by.
It is all relative, I used Baltic Birch because I had a bunch of thin strips left over and it was right there instead of at the lumber yard.
.
Anyway, I think you get the idea of how much stiffer a few ribs will make a flat panel.

Dave
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Old 5th January 2013, 07:00 PM   #48
maxo is offline maxo  United States
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So Dave, have you built one of this Bjorno Subs ? i want to start making some sawdust soon
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Old 6th January 2013, 10:19 AM   #49
epa is offline epa  Netherlands
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here you go
use the cutsheet from don snyder
all dims in fractional and mm units.
Click the image to open in full size.
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Old 7th January 2013, 01:29 PM   #50
maxo is offline maxo  United States
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Epa, how do you cut the holes inside the brace
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