Re: bass head
I think your looking at it the wrong way. You already assume that I don't have good speakers already and have nothing better to do that listen to obscenly loud bass tests...
I'm not going to build it because I feel like making my house resonate. I want to find out why and how well it works. Not everything is about music reproduction, technology is something I enjoy just as much.
optichammer said:
I think your looking at it the wrong way. You already assume that I don't have good speakers already and have nothing better to do that listen to obscenly loud bass tests...
I'm not going to build it because I feel like making my house resonate. I want to find out why and how well it works. Not everything is about music reproduction, technology is something I enjoy just as much.
It wouldn't have to be quite THAT complicated. A helicopter's blades have to be different pitches depending on where in their rotation they are, and which direction you want to go. At least with this, all blades would be the same pitch at the same time. That would simplify the linkage quite a bit. I work for a commercial HVAC manufacturer, and we make fans with variable pitch blades like this. They aren't used as much any more though. These certainly woudln't be applicable for this application - the fans I'm speaking of are huge, and are designed to run at very fast speeds. And the last time I looked at one, the actuators that adjusted the pitch were pneumatic. The frequency response probably woudln't even get up to 1hz, due to the amount of time it takes to change the blade pitch. 😀sdclc126 said:
mondaycurse said:
It's certainly not worth 13k to you, or even me. But people who have enough disposable income to make their home theater experience the ultimate might have a different answer. Just because you can't hear it doesn't mean it can't be sensed. I don't know about DTS, but the Dolby Digital spec goes down to 3hz. Sub-harmonic content in current movies is quite common. Batman Begins, for example, goes all the way down to 3hz.
To the comments about making it bigger or faster... it already has insane output at only 300 rpm, and it looks like it's only about 16-18" in diameter. If you don't need more output, then it seems like faster would just make more noise, and bigger would just make controlling blade pitch at higher frequencies harder.
Wow, I just saw Batman Begins but at someone elses house with an improperly setup home theater (rear speakers are in the front. Why have a home theater system if you don't even bother to set it up correctly...). I think the experience would be better if I had been able to hear like what direction he would pounce on the gunmen. I wonder what a difference it would make with a system capable of generating 3hz airwaves. 🙂
In what circumstance would they even use a 3hz tone to give a accurate effect? An earthquake maybe???
i JUST got done watching batman begins, and while it was good, it surely wasnt up to all the hype. people are saying its the best audio on a dvd yet. i really didnt think so, i can think of many that are better. where does this go to 3hz???
I put in a request for a spectrogram of "Batman Begins". I imagine jman will eventually get to it on his section of the IB forum.
That, explosions, tidal waves, helicopters, lots of things. Though in my opinion, Batman Begins also uses it some places that isn't appropriate. For whatever reason, they seem to use it when Scarecrow talks (see link below)BassAwdyO said:
See the waterfall chart in this post. It shows a few places.cowanrg said:
The pitch mechanism would be VERY easy to obtain.
Simply buy an alloy ball raced swash plate/rotorhead assembly and all the shafts and bearings etc for a gas powered model helicopter. A voice coil would be fairly simple to attach to a swashplate, Make the blades from thin carbon sheets to make it run silent. Vario make substantial units.
http://www.variocanada.com/product_info.php?cPath=26_34_70&products_id=1670
The motor would probably need to be geared down or use a low noise high torque brushless outrunner type motor, say like a big AXI and a speed controller so you can fine tune it. certanly should be DIYable
Simply buy an alloy ball raced swash plate/rotorhead assembly and all the shafts and bearings etc for a gas powered model helicopter. A voice coil would be fairly simple to attach to a swashplate, Make the blades from thin carbon sheets to make it run silent. Vario make substantial units.
http://www.variocanada.com/product_info.php?cPath=26_34_70&products_id=1670
The motor would probably need to be geared down or use a low noise high torque brushless outrunner type motor, say like a big AXI and a speed controller so you can fine tune it. certanly should be DIYable
well, since this is a "non-traditional' technology, why not try something different. instead of using a traditional voice coil assembly for the motor, why not use servo motors to control each of the blades...
in another thread around here people are talking about a moving vane that is controlled by a DC brushed servo motor. when an AC signal is applied (audio signal from amplifier), the motor turns back and forth quickly in tune with the signal. you could have 4 (or more) of these motors attached to the hub of the fan (small ones) and they would control the blade movement. it would presumably be more accurate than a helicopter assembly with a voice coil, and it COULD be much easier to design.
its just a thought... the helicopter thing just got me thinking about how the vanes on wings work on RC airplanes. they use small powerful servo motors. and they can handle the forces exerted on them. so, maybe that would be worth a shot. they are small anyways.
in another thread around here people are talking about a moving vane that is controlled by a DC brushed servo motor. when an AC signal is applied (audio signal from amplifier), the motor turns back and forth quickly in tune with the signal. you could have 4 (or more) of these motors attached to the hub of the fan (small ones) and they would control the blade movement. it would presumably be more accurate than a helicopter assembly with a voice coil, and it COULD be much easier to design.
its just a thought... the helicopter thing just got me thinking about how the vanes on wings work on RC airplanes. they use small powerful servo motors. and they can handle the forces exerted on them. so, maybe that would be worth a shot. they are small anyways.
Everyone give up?
Did this thread really die quietly back in November? Someone needs to make one and give us some plots and pics.
Both the Thigpen fan design and the Danley vane are making an amplifier, actually. A large amount of power moves a big mass (driver) and a relatively small amount of power is used to modulate the flow.
The Thigpen Rotary sub works exactly like a helicopter swash plate, but only does half of the functions--all blades twist the same amount at the same time. In a helicopter, one control twists all blades and the other control makes them twist more on one side than the other. (See http://travel.howstuffworks.com/helicopter5.htm)
In a rotary woofer, I would recommend a single servo motor, or a pair that can push on a swashplate.
A bandpass box to contain the out-of-band noise (like everything from 50Hz up) could be built just like a (somewhat larger) car muffler.
On the backside, some sort of infinite baffle box to waste the entire rear wave would be fine. An attic, the whole outdoors (venting through an exterior wall).
Nothing says that the control of the blade pitch needs to come from behind the blades. A motor in back spins the axle that drives all of the fan action, and a linkage on the other side of the blades could tie into the pitch controls.
The suggestion to have a servo motor on each blade was pretty wild, but may ultimately be the design with the lowest noise.
Since we don't really care how much mass is spinning -- we actually want lots of mass/momentum on that whole assembly. The only low mass component would be the blades themselves. You could actually mount several servo motors and spin the whole mess.
What would be a decent way of running the signal to the servo motors, then? Would need to be something like the concentric traces used in rotating lights (like older police car lights or disco spinners).
Hmmm...? I no one really working on a DIY version of this? I can't wait to hear this progress. This is so radically different and would come with radically different limitations. Imagine the discussion about trying to makea sub go higher? Like "my sub is fine from DC up to about 17HZ, but I can't get it up into the 30Hz range..."
I have a feeling that the rotary sub is tuned down to the 5-15Hz range because this is largely been non-addressed by other subs.
There is definitely potential content down there.
Did this thread really die quietly back in November? Someone needs to make one and give us some plots and pics.
Both the Thigpen fan design and the Danley vane are making an amplifier, actually. A large amount of power moves a big mass (driver) and a relatively small amount of power is used to modulate the flow.
The Thigpen Rotary sub works exactly like a helicopter swash plate, but only does half of the functions--all blades twist the same amount at the same time. In a helicopter, one control twists all blades and the other control makes them twist more on one side than the other. (See http://travel.howstuffworks.com/helicopter5.htm)
In a rotary woofer, I would recommend a single servo motor, or a pair that can push on a swashplate.
A bandpass box to contain the out-of-band noise (like everything from 50Hz up) could be built just like a (somewhat larger) car muffler.
On the backside, some sort of infinite baffle box to waste the entire rear wave would be fine. An attic, the whole outdoors (venting through an exterior wall).
Nothing says that the control of the blade pitch needs to come from behind the blades. A motor in back spins the axle that drives all of the fan action, and a linkage on the other side of the blades could tie into the pitch controls.
The suggestion to have a servo motor on each blade was pretty wild, but may ultimately be the design with the lowest noise.
Since we don't really care how much mass is spinning -- we actually want lots of mass/momentum on that whole assembly. The only low mass component would be the blades themselves. You could actually mount several servo motors and spin the whole mess.
What would be a decent way of running the signal to the servo motors, then? Would need to be something like the concentric traces used in rotating lights (like older police car lights or disco spinners).
Hmmm...? I no one really working on a DIY version of this? I can't wait to hear this progress. This is so radically different and would come with radically different limitations. Imagine the discussion about trying to makea sub go higher? Like "my sub is fine from DC up to about 17HZ, but I can't get it up into the 30Hz range..."
I have a feeling that the rotary sub is tuned down to the 5-15Hz range because this is largely been non-addressed by other subs.
There is definitely potential content down there.
I too am interested in the progress of anyone who attempted this project. I think the difficulty is in getting the pitch control mechanism to work with the driver. Perhaps we should post designs so people can try building them?
How about using peizoelectric devices to alter the blade pitch?
No doubt it would require several stacked crystals for each actuator, but ther action would probably be more efficient and linear that anything using mechanical linkages.
No doubt it would require several stacked crystals for each actuator, but ther action would probably be more efficient and linear that anything using mechanical linkages.
That style of fan sub has already been done years ago.
I can get the same effect with a 12 and a 10” sub I put a piece of paper near the window a good 3 meters away and it vibrates about 1cm peak to peak, the store room door also vibrates 5mm at very low frequencies about 20hz and that’s only running 60 watts. With the subs 60cm away I can knock over a bunch of AA battery on my computer table made of 18mm marine ply with a metal frame in less than 2 seconds with that setup
btw the fan must have fast acceleration because the wind takes longer to reach you than audio does.
I can get the same effect with a 12 and a 10” sub I put a piece of paper near the window a good 3 meters away and it vibrates about 1cm peak to peak, the store room door also vibrates 5mm at very low frequencies about 20hz and that’s only running 60 watts. With the subs 60cm away I can knock over a bunch of AA battery on my computer table made of 18mm marine ply with a metal frame in less than 2 seconds with that setup
btw the fan must have fast acceleration because the wind takes longer to reach you than audio does.
A 10", 12", or even 18" driver isn't going to be able to have anywhere near as much output as this thing at infrasonic frequencies. And there is no "wind", at least not in a sense that makes it separate from sound. It's simply pressure waves.
Hayden said:
The fansub runs at a constant speed, it's the pitch of the blades changing that creates the sound, it alternatly sucks and blows air in the room creating a pressure change, it's a different effect to a normal fan blowing air around in a room. When there is no sound playing the fansub doesn't blow any air, it just spins with the blades at 0 angle of attack.
And that is one of it's biggest downsides, for the tiny frequency range that it coveres and small % of time that it would even be called upon to operate, you have a ~1hp motor running constantly, whose own noise needs to be taken off.
Anything that can reproduce sound is audio IMHO.
We can sense sound below 20Hz so this fan woofer is a valid attempt to reproduce the whole audio range.
Phoenix Gold made something like this almost a decade ago, only problem was low output and time delay.
Maybe CD players can not produce infra sound but record players can.
The problem with randon high output infrasound is we get sick, its not like natural infra sound like thunder, waves or wind, these phenomena do not sound real from your best audio set ups, this could bridge that gap and there is no harm in trying.
We can sense sound below 20Hz so this fan woofer is a valid attempt to reproduce the whole audio range.
Phoenix Gold made something like this almost a decade ago, only problem was low output and time delay.
Maybe CD players can not produce infra sound but record players can.
The problem with randon high output infrasound is we get sick, its not like natural infra sound like thunder, waves or wind, these phenomena do not sound real from your best audio set ups, this could bridge that gap and there is no harm in trying.
As I said I can get pressure waves 3 meters away moving a piece of paper greatly back and forth with a cheap small setup I’m going to design my own low end sub and show it does work, I can give you a video clip if you like
Noise is a problem. But 1 HP constantly isn't since it doesn't need that amount of power while it doesn't move air.
1 Hz to 30 Hz is not a tiny frequency range BTW it is almost 5 octaves !
It is actually vice-versa. The subsonics coming from record players are mostly rumble and other unwanted garbage while the CD is capable of storing DC (at least theoretically).
And how does it look like 2 meters away ? 😉
Regards
Charles
Been there done that with a computer studio and burnt it to cd and it does store dc and I think most if not all cd players will give out dc.
If you want the clip email me skitzmix_rules@yahoo.com
If you want the clip email me skitzmix_rules@yahoo.com
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