Thanks
And to DrEm for pointing at the use of a bicycle tube for surround
I think I will stick to that
Theres a small issue with the air valve, but a small cutout will deal with that
And it will be adjustable by the airpressure
We will see whether it will make noises or not
But I dont expect it will move very much, so it will probably be ok
Sensitivity
Sure, with higher mms the sensitivity will goes down
Tho, at sub frequencies sensitivity goes up, right
Also, this is different as the higher mms comes from increased "sd"(area)
This will be 27-28", which equals 4x 15"
To the best of my knowledge 4x 15" will move FOUR times less than a single one
The chosen Beyma SM212 is special in the sense that its a 98db 12" with +/-7mm Xmax
If we stick to the comparison of 4x 15" it means that we get an effective Xmax that equals a 15" with 56mm Xmax (4x 14mm(p-p) = 56mm(p-p))
The big 31" Fostex has Xmax of 2.3mm, and impressive 96db with a mms of 440gr, Qts 0.69
PrecisionDevices 24" has Xmax of 15mm(p-p), and 99db with mms of 342gr
How much it moves will ofcourse depend on how deep it goes, and how loud its pushed, but I dont expect it will move very much
But it will be interesting to see the weight of all the needed polystyrene
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Update
The high density 50mm polystyrene for floors are only available in 500mm width
So, the 700mm round design with tube surround is on hold
May be that the softer poly is ok, or a smaller one is the option
The available tube will decide the size tho
I did found a 700mm LATEX tube, which could be interesting
New design is with TWO 12" woofers each panel
Which on its own might give a more stable design
It will be 500mm wide
Height could be like 800-1000mm
Surface would be 4000-5000cm2, which would be like 5-6x 15", each side if stereo subs
Actually, the cost of a second woofers isnt much more than the cost of the additional wood needed for the round 700mm "tube-design"
Rather use the money on a woofer, right
The high density 50mm polystyrene for floors are only available in 500mm width
So, the 700mm round design with tube surround is on hold
May be that the softer poly is ok, or a smaller one is the option
The available tube will decide the size tho
I did found a 700mm LATEX tube, which could be interesting
New design is with TWO 12" woofers each panel
Which on its own might give a more stable design
It will be 500mm wide
Height could be like 800-1000mm
Surface would be 4000-5000cm2, which would be like 5-6x 15", each side if stereo subs
Actually, the cost of a second woofers isnt much more than the cost of the additional wood needed for the round 700mm "tube-design"
Rather use the money on a woofer, right
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Polystyrene cone -- the EV 30W !
What I found on the web:
Re = 4 Ohm
Fs = 16 Hz
Vas = 5.9472 Ft^3
Qes = 0.3
Qms = 2.61
Qts = 0.2691
Sd = .3626 Ft^2 ?
Pe = 60 watts
Xmax = .15 in ( 3.81mm )
Le = 1.28 mH
Mms = .30624 kg?
BL = 20.261 Tesla-meter
1w SPL = 101.09 dB
no = 5 percent
Vd = 84.3 in^3
Sd = 562 sq in
It's indeed much lighter then those big paper cone, thus higher sensitivity.
And motors with 20TM BL and 5~6mm Xmax are not hard to find, so maybe it'll be a very good chance to get a superwoofer with big area polystyrene diaphragm of over 100dB/w
What I found on the web:
Re = 4 Ohm
Fs = 16 Hz
Vas = 5.9472 Ft^3
Qes = 0.3
Qms = 2.61
Qts = 0.2691
Sd = .3626 Ft^2 ?
Pe = 60 watts
Xmax = .15 in ( 3.81mm )
Le = 1.28 mH
Mms = .30624 kg?
BL = 20.261 Tesla-meter
1w SPL = 101.09 dB
no = 5 percent
Vd = 84.3 in^3
Sd = 562 sq in
It's indeed much lighter then those big paper cone, thus higher sensitivity.
And motors with 20TM BL and 5~6mm Xmax are not hard to find, so maybe it'll be a very good chance to get a superwoofer with big area polystyrene diaphragm of over 100dB/w
Regarding the round 70mm version with tube-surround
I just realised it probably wont work as smoothly as expected
1. The tube may not have enough control over the planar diaphragm, because of its unpredictable springyness
2. The space between the planar cone and surrounding baffle needs to be very precise, or the tube may push the cone sidewards, when airpressure is applied
There are ways around dealing with this, but its still unpredictable
But still, could be fun just to try it
Well, I did end up going back to the first version with "thread" surround, but modified with using strips of fiber net for surround
And using double 12" which ought to give better control
Surely not perfect either, but I think its the ways to go, if doing this
Beyma SM212 still seems like a fine woofer for this
Affordable low distortion woofer with high sensitivity and 15mm Xmax is a bit rare
I consider to use a SM212 for bassguitar as well
I just realised it probably wont work as smoothly as expected
1. The tube may not have enough control over the planar diaphragm, because of its unpredictable springyness
2. The space between the planar cone and surrounding baffle needs to be very precise, or the tube may push the cone sidewards, when airpressure is applied
There are ways around dealing with this, but its still unpredictable
But still, could be fun just to try it
Well, I did end up going back to the first version with "thread" surround, but modified with using strips of fiber net for surround
And using double 12" which ought to give better control
Surely not perfect either, but I think its the ways to go, if doing this
Beyma SM212 still seems like a fine woofer for this
Affordable low distortion woofer with high sensitivity and 15mm Xmax is a bit rare
I consider to use a SM212 for bassguitar as well
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Sony made a flat square woofer driven with four motor assemblies
Bertagni Electroacoustic Systems (BES) made some flat 2'x4' speakers.
Neither caught on, and were nothing special.
http://www.soundadvance.com/downloads/SA73/SA2C.pdf
Bertagni Electroacoustic Systems (BES) made some flat 2'x4' speakers.
Neither caught on, and were nothing special.
http://www.soundadvance.com/downloads/SA73/SA2C.pdf
You could say that about many things in audio, or elsewhere
I wouldnt rate it as a quality parameter
Many ways of wrongly use units could lead to the judgement of "not working"
Many things that do get popular, are not always anything special either
Also, many ideas doesnt work for mass production, or too expencive
Big Rubanoide could be one of those
Anyway, it just makes it an even bigger challenge
btw, maybe remember that this is for free standing dipole sub only, nothing else
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some correction:Polystyrene cone -- the EV 30W !
..Re = 4 Ohm
Fs = 16 Hz
Vas = 5.9472 Ft^3
Qts = 0.2691
Sd = .3626 Ft^2 ?
Mms = .30624 kg?
Sd = 562 sq in
And motors with 20TM BL and 5~6mm Xmax are not hard to find, so maybe it'll be a very good chance to get a superwoofer with big area polystyrene diaphragm of over 100dB/w
Vas = 5.9472 m^3 (5947 litres)
Sd =3626 cm^2 = 562 sq in
and have you more info about cone concstruction?
6 EVs: dougronald.com , look "wall of sound"
generally i don't look sub topics, but find this when searching kef 1814 (and b139)
(two side) laminating by aluminium foil (kef) or tin paper (?)
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If you want to stiffen that diaphram then use thin aluminium foil. A company called Leak (as well as Kef) did the same thing. Kef used a solid polystyrene cone, where as Leak used a conventional cone shape with approximately 10 - 12mm thick polystyrene.
When i saw this i went searching for a picture on the net of the designer of the cone literally standing on the apex of the driver cone. It was that stiff & strong that it'd take an adult mans weight without breaking
A thin sheet of aluminium foil either side should prevent a hell of a lot of flexing
Found it, click for more info
E2A:- If you look up "Leak Sandwich" speakers on the net you'll find out a load more.
When i saw this i went searching for a picture on the net of the designer of the cone literally standing on the apex of the driver cone. It was that stiff & strong that it'd take an adult mans weight without breaking
A thin sheet of aluminium foil either side should prevent a hell of a lot of flexing
Found it, click for more info
E2A:- If you look up "Leak Sandwich" speakers on the net you'll find out a load more.
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The automotive audio industry has created a few unusual subwoofers like this four motor rectangle speaker in the attached picture. I believe it about 34" on one side using four 15" woofers.
I think you would get the best bass from a push-pull planar similar to Eminent Technologies, or the best Magnepans like the MG20 which have magnets on both the front and back for true push pull. NdFeB magnets can provide good efficiency and have come down in price. A steel frame completes the magnetic flux path, and would have a minor sonic impact to very low frequencies.
A suspension of butyl or silicone rubber will last decades. The membrane can also be clamped into a wood/plastic frame and several real metal springs can be used, and tuned to minimize resonance. The large Apogee bass panels used this frame+springs construction technique. Each springs had a screw to adjust tension and tune the membrane over the length to reduce resonance. The Apogee bass panels were typically crossed around 300Hz, and could produce 20Hz bass because of their massive area, despite having magnets only on the rear.
I think you would get the best bass from a push-pull planar similar to Eminent Technologies, or the best Magnepans like the MG20 which have magnets on both the front and back for true push pull. NdFeB magnets can provide good efficiency and have come down in price. A steel frame completes the magnetic flux path, and would have a minor sonic impact to very low frequencies.
A suspension of butyl or silicone rubber will last decades. The membrane can also be clamped into a wood/plastic frame and several real metal springs can be used, and tuned to minimize resonance. The large Apogee bass panels used this frame+springs construction technique. Each springs had a screw to adjust tension and tune the membrane over the length to reduce resonance. The Apogee bass panels were typically crossed around 300Hz, and could produce 20Hz bass because of their massive area, despite having magnets only on the rear.
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Hi there: Last summer, I built a similar experimental sub by bolting an Aura Bass Shaker to a 16-inch sheet of masonite (1/8-inch thick) and bonding the sheet's edges to the end a 48-inch pipe forming a u-frame. The sub plays bass, however, my wife a musician, says the sub is not musical. I intrend to build another, by attaching the Aura to a 48-inch sheet of masonite and suspend the sheet from a frame with bunge cords ( similar to the mounting of a concert gong, hope it does not sound gong like) .... regards, Michael Droke
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