DIY Brothers,
Here starts a subwoofer project.
I now have two 21-inch woofers, and I promised my wife no more loudspeakers of any kind in the living room. No cutting holes in the floor or the ceiling either. So I have just bought this for the dining room.
Last night I told her when I get done none of the doors or drawers will open, and it hit her that I intend to stuff it with bass! She seems resigned to it. More later.
Here starts a subwoofer project.
I now have two 21-inch woofers, and I promised my wife no more loudspeakers of any kind in the living room. No cutting holes in the floor or the ceiling either. So I have just bought this for the dining room.
Last night I told her when I get done none of the doors or drawers will open, and it hit her that I intend to stuff it with bass! She seems resigned to it. More later.
Attachments
Question for Saul (he'll charge for this)
If it came to that would she get the subwoofer because it matches her other dining room furniture?
If it came to that would she get the subwoofer because it matches her other dining room furniture?
Focus...
Alright, enough levity, I'm too nervous! I'm thinking of an isobaric open clamshell, connected by a tunnel/passage/chamber which would be screwed onto the back, over the drivers, sort of like a flat head over an old ford V8.
The woofers would both face backwards, running out of phase, for vibration abatement. These would be on the right side so they will try and fail to move the rest of the cabinet back and forth, kind of like the tail wagging the dog. By the way, this would be up to a pound of cone on each, so they need to cancel each other as much as possible. One would vent out the bottom. Two nice flared ports would exit on the left.
By the way, I would like to add and remove mass from the cones instead of adding or removing volume. Is there a way to add and remove weight from a large driver repeatedly for tuning Qts? I've heard of lead shot and glue, lead wire and glue, but is there a method that uses bolt-on mass? I want to add as much as 300 grams to the cone.
Alright, enough levity, I'm too nervous! I'm thinking of an isobaric open clamshell, connected by a tunnel/passage/chamber which would be screwed onto the back, over the drivers, sort of like a flat head over an old ford V8.
The woofers would both face backwards, running out of phase, for vibration abatement. These would be on the right side so they will try and fail to move the rest of the cabinet back and forth, kind of like the tail wagging the dog. By the way, this would be up to a pound of cone on each, so they need to cancel each other as much as possible. One would vent out the bottom. Two nice flared ports would exit on the left.
By the way, I would like to add and remove mass from the cones instead of adding or removing volume. Is there a way to add and remove weight from a large driver repeatedly for tuning Qts? I've heard of lead shot and glue, lead wire and glue, but is there a method that uses bolt-on mass? I want to add as much as 300 grams to the cone.
MIKEVO,
Those glass doors are going be a problem. Plywood across the whole front inside. Maybe some pictures of dishes?
Those glass doors are going be a problem. Plywood across the whole front inside. Maybe some pictures of dishes?
You could replace the glass with plexiglass? Might look pretty funny with some glued-down dishes illuminated from inside.
Personally if I were going to hide subs from the missus, I would put them inside the sofa.
Personally if I were going to hide subs from the missus, I would put them inside the sofa.
🙂
FYI The third Season of Better Call Saul begins filming this week---great show that is getter better and better (no pun intended)...🙂
FYI The third Season of Better Call Saul begins filming this week---great show that is getter better and better (no pun intended)...🙂
I would get some tubes of construction adhesive, turn the thing on it's back with doors open, dwrs removed & get right at gluing every seam in the thing to quite the buzz down or have it spray foamed all around the inside to get the buzz out.
Not sure what you spent but if you spent serious dough I would return it and design/build the sub and then later build it up to look like that or hire a dude. The piece is a little on the decorative side but almost if not all that detail stuff can be bought premade. I am by no means a master carpenter but I think I could pull it off. I'd go all birch and use brown dye, seal it with dewaxed shellac, wipe on a dark brown glaze, and finish with lacquer.
I am picky and so is my wife but a large TH sub running floor to ceiling in a corner painted to match the room would probably be doable and very easy to hide or blend in with decor.
I am picky and so is my wife but a large TH sub running floor to ceiling in a corner painted to match the room would probably be doable and very easy to hide or blend in with decor.
Hi paulfx,
Post #5: "...isobaric open clamshell, connected by a tunnel/passage/chamber..."
Take a look @ djk's PPSL arrangement, it works with any kind of enclosure (sealed, vented, horn, etc.).
http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
Post #5: "...I would like to add and remove mass from the cones instead of adding or removing volume. Is there a way to add and remove weight from a large driver repeatedly..."
IIRC Josh Ricci has posted that he uses magnet slugs for this purpose (cannot find the quote). You might PM him on that subject.
Regards,
From data-bass.com: "... added mass method is used to lower the FS of the system the required amount to calculate the parameters. This is accomplished using 6.5 gram ceramic magnets clamped through the driver cone..."
http://www.data-bass.com/know-how
Post #5: "...isobaric open clamshell, connected by a tunnel/passage/chamber..."
Take a look @ djk's PPSL arrangement, it works with any kind of enclosure (sealed, vented, horn, etc.).
http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
Post #5: "...I would like to add and remove mass from the cones instead of adding or removing volume. Is there a way to add and remove weight from a large driver repeatedly..."
IIRC Josh Ricci has posted that he uses magnet slugs for this purpose (cannot find the quote). You might PM him on that subject.
Regards,
From data-bass.com: "... added mass method is used to lower the FS of the system the required amount to calculate the parameters. This is accomplished using 6.5 gram ceramic magnets clamped through the driver cone..."
http://www.data-bass.com/know-how
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I've got to get it air tight and rattle free. A single sheet of plywood across the front from the inside, then construction glue the doors and drawer fronts to that. Then foam the rest of the spaces. (Thnx Air!) The beast won't get here for a month or two. I have the woofers, now I have to give them "adjusto-mass." What better place to do some research on how to do that than right here on diyAudio?
Mass loading formulas courtesy of Ron E and GM -
mass(m) = 22.428*dia^4(cm)/(Fs^2*Vas(liters))
m' = m + mass added
mass ratio(mr) = m'/m
Fs' = Fs/mr^0.5
Qes' = Qes*mr^0.5
Qms' = Qms*mr^0.5
then: Qts' = Qes'*Qms'/(Qes'+Qms')
Vas is unchanged
n0 = 9.6352*10^-10*Fs'^3*Vas(liters)/Qes'
SPL = 112.018+10*Log(n0)
But it's probably a bad idea to add 300 grams. The same thing can be achieved with a bit of eq (kind of) and you will need eq anyway once you see what the room does to your carefully planned frequency response. And if these are very large excursion drivers they won't sim accurately anyway.
As others have mentioned, it's going to be nearly impossible to make a good enclosure from that, for the reasons mentioned.
Also, isobaric loading is probably a bad idea.
mass(m) = 22.428*dia^4(cm)/(Fs^2*Vas(liters))
m' = m + mass added
mass ratio(mr) = m'/m
Fs' = Fs/mr^0.5
Qes' = Qes*mr^0.5
Qms' = Qms*mr^0.5
then: Qts' = Qes'*Qms'/(Qes'+Qms')
Vas is unchanged
n0 = 9.6352*10^-10*Fs'^3*Vas(liters)/Qes'
SPL = 112.018+10*Log(n0)
But it's probably a bad idea to add 300 grams. The same thing can be achieved with a bit of eq (kind of) and you will need eq anyway once you see what the room does to your carefully planned frequency response. And if these are very large excursion drivers they won't sim accurately anyway.
As others have mentioned, it's going to be nearly impossible to make a good enclosure from that, for the reasons mentioned.
Also, isobaric loading is probably a bad idea.
Maybe post your driver's t/s specs, enclosure volume and someone might advise whether you even need iso loading or added mass - I'm guessing no.
Up-Down Thinking
Well, Just, in the cabinet I will have something like 350 to 400 liters to play with. For each driver Qts is around 0.337, Fs around 25 Hz. Vas is 605 liters. Of course I have to break them in and measure them.
So, if I add mass, Qts goes up, which means more Vb needed for a flat alignment. I would like to use up as much available Vb as I can and get that Fs down to something like 20 Hz by adding weight. These are very efficient so I can waste some SPL.
I had a 12 inch clamshell iosobaric sub a couple decades ago and it went clean down to 15 Hz, but a) there's no music down there, and b) it was so butt ugly it never made it out of the basement. Or rather the Wf was negligible!
Well, Just, in the cabinet I will have something like 350 to 400 liters to play with. For each driver Qts is around 0.337, Fs around 25 Hz. Vas is 605 liters. Of course I have to break them in and measure them.
So, if I add mass, Qts goes up, which means more Vb needed for a flat alignment. I would like to use up as much available Vb as I can and get that Fs down to something like 20 Hz by adding weight. These are very efficient so I can waste some SPL.
I had a 12 inch clamshell iosobaric sub a couple decades ago and it went clean down to 15 Hz, but a) there's no music down there, and b) it was so butt ugly it never made it out of the basement. Or rather the Wf was negligible!
Again, if you post t/s parameters you could get better advise. If you DON'T add mass, qts WON't go up and you won't need more Vb. Like I said, you probably don't need to do what you are planning to do, and it probably won't work the way you think it will.
21" Driver:Hiwell_21SW005
Hi All,
FYI:
21SW005:21",1500W RMS, 3000W program,5" copper coil, neodymium subwoofer-hiwell
..But Use Qmd=16.5611429(MJK) for Driver TS Consistency
b🙂
Hi All,
FYI:
21SW005:21",1500W RMS, 3000W program,5" copper coil, neodymium subwoofer-hiwell
..But Use Qmd=16.5611429(MJK) for Driver TS Consistency
b🙂
The glass is PROBABLY no issue as long as it's sealed and glued in tight and is a reasonable thickness. My intuition tells me it would take a lot of bass to break the glass outright. But I suppose it never hurts to exercise caution.
I do love the idea of a glued-down set of dishes on the inside though. That's great.
If I were you I'd make use of push-pull arrangements to cancel the vibration from moving mass of the drivers.
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