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View Full Version : Poll (w/pics): Which type of bracing Is better for my box?



ARSkemp
12-10-2009, 12:53 PM
Box is ~4ft^3 tuned to 40hz with a ~8" aero. Probably for 2 HDC312s. Double baffle on top, triple for just the aero (to keep it a diameter's distance from the back wall).

Which type of bracing would be better in this case?

Image 1 (1.5" Dowels)
http://img694.imageshack.us/img694/7350/subboxdowelbracing.jpg


Image 2 (don't know the name of this bracing, using .75" mdf just like the box)
http://img13.imageshack.us/img13/4043/subboxsquarebracing.jpg

phemps
12-10-2009, 12:56 PM
both would probably work fine. id go with the dowels because its less work. or all thread too

hrtbrk1
12-10-2009, 12:56 PM
round is better

dappa5
12-10-2009, 12:57 PM
use all thread like the dowels if you want easy , but i'm partial to "window bracing" myself

phemps
12-10-2009, 01:00 PM
the only thing that ***** about all thread is having some of it stick out the box and the nut on the end. it looks ******

spltuscon
12-10-2009, 01:44 PM
I prefer dowels but both are good. If you do window bracing (image2) then roundover both sides of the openings and it'll be fine too.

mlstrass
12-10-2009, 01:50 PM
#2 is window bracing, much stronger then dowels as it has much more contact area.

Not that hard to do and just use a roundover bit to smooth em over. I usually make mine about 1 1/2" wide for the frame part...

basebalz13
12-10-2009, 01:52 PM
threaded rod

PV Audio
12-10-2009, 04:11 PM
#2, not even close. Dowels are all but useless in anything other than bookshelf size loudspeakers.

Without trying to be rude, people don't seem to be a bit confused about what bracing is or how it works. Threaded rod is NOT bracing. It is used to eliminate opposing panel flex. Bracing works to lower enclosure resonance by raising the resonant frequencies of the panels. Think about it like this: why are the low notes on a piano the long strings and the high notes the short strings? Why is it that when you touch one of the long strings and pluck it, the note is higher? You're changing the resonant frequency of that string. Damping the string, which is what those pads are actually called, removes the resonance. Damping the enclosure is what bracing does. Threaded rod does not damp anything like wood does; you use it in high power applications where you need the box to just not flex apart under high pressure loads.

ARSkemp
12-10-2009, 04:45 PM
#2 is window bracing, much stronger then dowels as it has much more contact area.

Not that hard to do and just use a roundover bit to smooth em over. I usually make mine about 1 1/2" wide for the frame part...

So would 1 1/2" be you recommendation even though the box isn't very deep? The box in the images is only 12.5" net depth (from front to back in the inside) and I don't want to impede airflow too much...


#2, not even close. Dowels are all but useless in anything other than bookshelf size loudspeakers.

Without trying to be rude, people don't seem to be a bit confused about what bracing is or how it works. Threaded rod is NOT bracing. It is used to eliminate opposing panel flex. Bracing works to lower enclosure resonance by raising the resonant frequencies of the panels. Think about it like this: why are the low notes on a piano the long strings and the high notes the short strings? Why is it that when you touch one of the long strings and pluck it, the note is higher? You're changing the resonant frequency of that string. Damping the string, which is what those pads are actually called, removes the resonance. Damping the enclosure is what bracing does. Threaded rod does not damp anything like wood does; you use it in high power applications where you need the box to just not flex apart under high pressure loads.

Definitely learned something new from this, thanks for the response.

mlstrass
12-10-2009, 07:33 PM
if using MDF then yes 1 1/2" minimum as MDF isn't very strong and could still flex, especially if the window part is too small...

ARSkemp
12-10-2009, 11:05 PM
if using MDF then yes 1 1/2" minimum as MDF isn't very strong and could still flex, especially if the window part is too small...

Alright, so for the 1.5" part, do you mean the width of the pieces of the frame (so that the "window" created by the frame is smaller/larger depending on the width) or do you mean the thickness of the window (like stacking 2 .75" mdf windows together, like a double baffle)? or both?

schackel
12-10-2009, 11:12 PM
#2, not even close. Dowels are all but useless in anything other than bookshelf size loudspeakers.

Without trying to be rude, people don't seem to be a bit confused about what bracing is or how it works. Threaded rod is NOT bracing. It is used to eliminate opposing panel flex. Bracing works to lower enclosure resonance by raising the resonant frequencies of the panels. Think about it like this: why are the low notes on a piano the long strings and the high notes the short strings? Why is it that when you touch one of the long strings and pluck it, the note is higher? You're changing the resonant frequency of that string. Damping the string, which is what those pads are actually called, removes the resonance. Damping the enclosure is what bracing does. Threaded rod does not damp anything like wood does; you use it in high power applications where you need the box to just not flex apart under high pressure loads.
ok cool. well would you use both for a box for my set up in my sig?
thanks

PV Audio
12-11-2009, 01:26 AM
ok cool. well would you use both for a box for my set up in my sig?
thanks
No. Threaded rod is for people who have multiple high powered drivers in a single chamber enclosure. While wood glue is going to hold the box together, the flex caused by the sound pressure can cause the wood to flex and therefore become stressed. That's when you use rods. For damping resonance, i.e.

http://gallery.avsforum.com/data/507/BracingAngled.jpg

Versus for eliminating flex:

http://i184.photobucket.com/albums/x241/ryanvalin/Tundra%20Sub%20Enclosure%202/box2002.jpg

Rod is used when you have very large panels because you have large airspaces that extensive bracing would take away from and you're just wanting maximum output.

bjfish11
12-11-2009, 05:54 AM
#2 is window bracing, much stronger then dowels as it has much more contact area.

Not that hard to do and just use a roundover bit to smooth em over. I usually make mine about 1 1/2" wide for the frame part...

This, without a doubt.

marcotheclepto
12-11-2009, 08:22 AM
This, without a doubt.

x2.