how important is bracing???

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Hi All, I am building two more subs for my listening room and have two good old Altec 4.5 sq ft cabs and will use the Dayton Audio RSS315HF-4 12" Reference HF Subwoofer 4 Ohm driver and the Behringer NU1000DSP iNUKE 1000 Watt Power Amplifier with DSP for power.

The back AND front of the cabs are glued in place so I have to work through the driver hole. It is a pain to brace through the hole so my question is: How important is bracing??? what is the downside of not bracing the inside and if it is really important, how can I do it easily through the hole?
 
The back AND front of the cabs are glued in place so I have to work through the driver hole. It is a pain to brace through the hole so my question is:
1)How important is bracing???
2)what is the downside of not bracing the inside and if it is really important, how can I do it easily through the hole?
Hi djn,
1) Bracing is important for eliminating unwanted cabinet resonances.
2) The downside of not bracing is a "looser" upper bass, as well as loss of some upper SPL.
You could cut four 2"x2" to the cabinet depth and glue them in place around the speaker hole.

Art
 
Well I'll be damned! I pull the cabs out tonight when i got home and just for fun i pulled off one of the velcro tabs that holds the grill on and low and behold there was a screw!!! I pulled the rest off and there were all the screws to take the front baffle off.
 
For future reference, look at the triangles
triangledel.jpg

You need to nibble away the right angle corner, because when the panels were joined, glue will of squidged out. So the cab no longer has an internal 90, it has a bead of goo the triangle would hit. So you must take off the corner.


tridel.png
 
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Since stiffness goes up at the cube of thickness, one easy way to brace a closed box is to add very stiff panels to the exterior that cover at least ~71% of each panel.

The aforementioned threaded rod system is excellent also, especially when building Sonotube, etc., tube type subs to preload/compress all parts together to take max advantage of the tube's incredible axial stiffness.

GM
 
You're welcome! FWIW, I do/recommend both woofers unless it's either a bipole or just plain weighs a lot to damp out high power oscillating vibrations. That, or place something massive on it like a large potted plant, decorative marble or similar.

GM
 
If i want to go lower than the driver/cabinet combo allows, how far can i push it with the DSP on the iNuke?
You can push it past Xmax with the NU1000DSP, and to voice coil burn levels with the NU3000DSP or NU6000DSP ;^).

The processing available has plenty HP/LP and EQ to flatten the response, and dynamic EQ and output limiters to dial in a safe power level with processing applied. Long term, about 30 volts should be safe for the drivers you purchased.
 
I dont think ill have to push it too much. When i look at the cabinet volume to get F3 of 37hz in a sealed box it says 2.88 cu ft. Which is just a bit smaller than mine. My other 2 subwoofers are flat to 22hz and this is a dedicated listening room so i should be ok....i think.
 


I've been thinking about using rods myself, though my idea was to put them across one side to the other, dead center. (and then more if needed.) I never thought to put them through the driver's mounting holes.

IMO, that way is much too difficult. Just thread one in from the back, until it hits the driver's magnet. Then do the others my way.

the idea, obviously, is that all sides of the enclosure will be expanding, or contracting, at the same time, so they can in effect "brace each other."
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Another way I might try it is with simple aluminum L channel, glued down the inside-center of each side. That way, the centers are braced by the stiff outside areas, and you still have minimal weight.
 
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