Slowmotion:
Shelf braces are a way to ~ 'kill two birds with one stone' by tying all sides together while breaking up large panels into smaller ones, so they must all touch/interlock. For sub duty only in cabs that aren't acoustically large for the BW, they're very effective and their negative side effects occur at frequencies above its cutoff.
Matttcattt:
Your cab needs to be too large IMO to keep from getting out of BW noise back through the cone, but if you want to use them, then make enough of them to subdivide the cab into many smaller cabs, ideally as close as you can to the golden ratio of 0.618:1.0:1.618. IOW each smaller 'cab' would have this dimensional ratio as would each 'cab' to each other 'cab'.
When figuring the round cutouts to allow airflow, you want to use a variety of different sizes, preferably eggshaped or at least freeform, and as large as practical without destroying the structural integrity of the piece. Some folks cut out four big rectangles, leaving just an "X" brace. Might as well just stick in 2x4s/wood dowels/whatever and save yourself all that sawing IMO.
GM
Shelf braces are a way to ~ 'kill two birds with one stone' by tying all sides together while breaking up large panels into smaller ones, so they must all touch/interlock. For sub duty only in cabs that aren't acoustically large for the BW, they're very effective and their negative side effects occur at frequencies above its cutoff.
Matttcattt:
Your cab needs to be too large IMO to keep from getting out of BW noise back through the cone, but if you want to use them, then make enough of them to subdivide the cab into many smaller cabs, ideally as close as you can to the golden ratio of 0.618:1.0:1.618. IOW each smaller 'cab' would have this dimensional ratio as would each 'cab' to each other 'cab'.
When figuring the round cutouts to allow airflow, you want to use a variety of different sizes, preferably eggshaped or at least freeform, and as large as practical without destroying the structural integrity of the piece. Some folks cut out four big rectangles, leaving just an "X" brace. Might as well just stick in 2x4s/wood dowels/whatever and save yourself all that sawing IMO.
GM
more questions, and i dont want to start a new thread.
1. ports, i am using winisd to make graphs, and this program only allows a small range of port sizes and lengths. if it says i need 3 ports of x length, and z width and hieght (square port), can i have one port x long, z wide, and 3 times z high?
2. carpet, i have read somewhere that i should put carpet on the inside of the box. why should i do this? which side/s do i put it on? the side with the driver and port/s, or the oposite side?
thankyou for any answers.
PS: sorry about the delay SimonTY, i have been on holiday, i will E-Mail you my address, and send you the money ASAP.
1. ports, i am using winisd to make graphs, and this program only allows a small range of port sizes and lengths. if it says i need 3 ports of x length, and z width and hieght (square port), can i have one port x long, z wide, and 3 times z high?
2. carpet, i have read somewhere that i should put carpet on the inside of the box. why should i do this? which side/s do i put it on? the side with the driver and port/s, or the oposite side?
thankyou for any answers.
PS: sorry about the delay SimonTY, i have been on holiday, i will E-Mail you my address, and send you the money ASAP.
Matttcattt:
WinISD, the freeware version, can calculate that for you.
Just click on the circle under "shape" if you want a rectangular port, and fill in the number "1" for the number of ports.
Actually, in a 13 Ft³ box, you can get by without a port jutting into the box. The ¾" thickness of the MDF itself will suffice. The larger the box, the smaller the port length for any given port crossection. In large boxes such as yours, simply cutting a hole in the wall of the box will give you a usable vent.
According to WinISD, a vent 3" X 6" will tune your box to 30 Hz.
If you want to make the cross section larger, (which will result in less port noise), then you can increase the port size if you want. For instance, a port that is 6" X 10" would require a length of 7¾".
You can also switch the dimensions in WinISD to Metric if you feel more comfortable that way.
WinISD, the freeware version, can calculate that for you.
Just click on the circle under "shape" if you want a rectangular port, and fill in the number "1" for the number of ports.
Actually, in a 13 Ft³ box, you can get by without a port jutting into the box. The ¾" thickness of the MDF itself will suffice. The larger the box, the smaller the port length for any given port crossection. In large boxes such as yours, simply cutting a hole in the wall of the box will give you a usable vent.
According to WinISD, a vent 3" X 6" will tune your box to 30 Hz.
If you want to make the cross section larger, (which will result in less port noise), then you can increase the port size if you want. For instance, a port that is 6" X 10" would require a length of 7¾".
You can also switch the dimensions in WinISD to Metric if you feel more comfortable that way.
kelticwizard said:
the help documents with winisd say that ports must be 3" long as a minimum, is this true? i have seen many sub woofers with 'wall-thick' ports. if i can use the wall thickness, it will make working out the size, and making the port/s easier.
mikee12345 said:winisd can be abit dodgy
one version doesnt calc ports right when u have 2
do you know which?
i have the original, as the website advises that the pro version is still in testing.
i think the old version is safe.
i use a patched version of new one
u shud get a few programs to compare with
re: ports
i wouldnt worry about using wall thickness.
a box that is tuned properly is simple one that has driver volume,bracing ,shelf port etc minused from total volume
my jbl tuned to 33hz like it shudve.
also shelf ports lengths are minus 0.5 *height ,i think.
in theor winisd SHUd allow ports down to 0.0000001 inches
i use a patched version of new one
u shud get a few programs to compare with
re: ports
i wouldnt worry about using wall thickness.
a box that is tuned properly is simple one that has driver volume,bracing ,shelf port etc minused from total volume
my jbl tuned to 33hz like it shudve.
also shelf ports lengths are minus 0.5 *height ,i think.
in theor winisd SHUd allow ports down to 0.0000001 inches
if ur stuffing a sealed box,it just acts like a 10% larger box when fully stuffed>or something>
there was a good link on the net about some one who fully tested stuffings.
i would imagine using some sort of speaker stuffing is best.
apparently pinkbatts works.
any sort of fibrous material will workbut to what degree-who knows.
ported box-just line the walls dont 'fill' it
cos then ur volume will be different-
so your port wont tune right
and also it mite get abit resistive,the port that is
those are my opinions-some one will correct me if im wrong.
ooh its late ,so excuse my ramblings,it mostly makes sense
there was a good link on the net about some one who fully tested stuffings.
i would imagine using some sort of speaker stuffing is best.
apparently pinkbatts works.
any sort of fibrous material will workbut to what degree-who knows.
ported box-just line the walls dont 'fill' it
cos then ur volume will be different-
so your port wont tune right
and also it mite get abit resistive,the port that is
those are my opinions-some one will correct me if im wrong.
ooh its late ,so excuse my ramblings,it mostly makes sense
Hi Matttcattt,
People get bored, and want to see things happening, progress. You have been hovering around some basic questions and points for a while, and I think everything important has already been answered!
All that remains is to get building the sub, and expect to experiment with it - that way you can learn by the best method!
Box- brace well, don't make it a cube, make it pretty, make it forwards-firing, don't worry anymore than that
Ports- make it/them a little oversized and cut down length to adjust tuning if necessary
Stuffing and overall box volume- work out box volume and assume your (not overdone) stuffing adds enough volume to compensate for the port volume - just stick foam to the walls and be happy Do work out how much vol. is lost from the bracing. Use a glue gun or spray glue on the stuffing, I tried nails once, but I wouldn't really advise that!!
I still have this Eminence bass driver taking up space somewhere, please e-mail me if you want it. I will need your address, then a little money for postage, won't be much - it's quite light.
-Simon
People get bored, and want to see things happening, progress. You have been hovering around some basic questions and points for a while, and I think everything important has already been answered!
All that remains is to get building the sub, and expect to experiment with it - that way you can learn by the best method!
Box- brace well, don't make it a cube, make it pretty, make it forwards-firing, don't worry anymore than that
Ports- make it/them a little oversized and cut down length to adjust tuning if necessary
Stuffing and overall box volume- work out box volume and assume your (not overdone) stuffing adds enough volume to compensate for the port volume - just stick foam to the walls and be happy
Do work out how much vol. is lost from the bracing. Use a glue gun or spray glue on the stuffing, I tried nails once, but I wouldn't really advise that!!I still have this Eminence bass driver taking up space somewhere, please e-mail me if you want it. I will need your address, then a little money for postage, won't be much - it's quite light.
-Simon
allow for the cost of a chiropractor as well
if you work out a budget and you plan to make such big boxes, don't forget to allow the cost of a chiropractor!!!!
also if you want to make big test boxes, consider instead of making two separate big boxes, make two modules so that you can bolt them together to get the bigger size.
if you work out a budget and you plan to make such big boxes, don't forget to allow the cost of a chiropractor!!!!
also if you want to make big test boxes, consider instead of making two separate big boxes, make two modules so that you can bolt them together to get the bigger size.
SimontY said:Hi Matttcattt,
People get bored, and want to see things happening, progress. You have been hovering around some basic questions and points for a while, and I think everything important has already been answered!
All that remains is to get building the sub, and expect to experiment with it - that way you can learn by the best method!
Box- brace well, don't make it a cube, make it pretty, make it forwards-firing, don't worry anymore than that
Ports- make it/them a little oversized and cut down length to adjust tuning if necessary
Stuffing and overall box volume- work out box volume and assume your (not overdone) stuffing adds enough volume to compensate for the port volume - just stick foam to the walls and be happy
I still have this Eminence bass driver taking up space somewhere, please e-mail me if you want it. I will need your address, then a little money for postage, won't be much - it's quite light.
-Simon
i have started cutting the MDF, and when i get a chance i will post some pictures.
i will E-mail you my address if you post your E-mail here. send me your address and i will post the cash (£10?).
i have some questions about these "golden ratios" and "standing waves".
1. what are the "golden ratios"?
2. will standing waves matter in a sub? using this program, the standing waves are at 200Hz, which my sub will not reach (LP at 120Hz).
1. what are the "golden ratios"?
2. will standing waves matter in a sub? using this program, the standing waves are at 200Hz, which my sub will not reach (LP at 120Hz).
Hi MatttCattt,
I can't remember what golden ratios I've seen before, look here for some good ratios:
http://www.audioasylum.com/forums/rives/messages/375.html
These are more useful for rooms than subwoofer cabinets
I agree it can't be so important for such low frequencies, but you will get [quiet] sounds at ~200hz coming from your sub, unless you somehow roll it off ultra steeply.
Better to use good ratios than a cube
I got your e-mail btw, cheers.
-Simon
I can't remember what golden ratios I've seen before, look here for some good ratios:
http://www.audioasylum.com/forums/rives/messages/375.html
These are more useful for rooms than subwoofer cabinets
I agree it can't be so important for such low frequencies, but you will get [quiet] sounds at ~200hz coming from your sub, unless you somehow roll it off ultra steeply.
Better to use good ratios than a cube
I got your e-mail btw, cheers.
-Simon
SimontY said:Hi MatttCattt,
I can't remember what golden ratios I've seen before, look here for some good ratios:
http://www.audioasylum.com/forums/rives/messages/375.html
These are more useful for rooms than subwoofer cabinets
I agree it can't be so important for such low frequencies, but you will get [quiet] sounds at ~200hz coming from your sub, unless you somehow roll it off ultra steeply.
Better to use good ratios than a cube
I got your e-mail btw, cheers.
-Simon
So about 1x1.5x2?
I will have a LP filter. i havent desided what type yet.
yep, money is in the post now. should arive friday/saturday (is there post on saturday?).
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