My playing CDs through my DVD player is flat to about 2hz, and still has output to 1hz (or would that be 1 hert, sans the z? 😉 ). The rolloff at 1hz could be anywhere in the chain. And after all, that is a whole octave below 2hz. 😀Iron-Wizard said:
Hayden said:
I completely believe that you can get measurable output at very low frequencies with your 10" or 12" drivers. But you simply aren't going to get nearly as MUCH output at infrasonic frequencies as you will with the fan sub. Not unless you've got special drivers with excursion that is measured in feet. It's a simple issue of displacement.
I understand what the fan sub is capable of, I can imagine that the fan sub would feel like when someone drops a big sheet of 9 ply flat on the floor sort of like a strong instant gush of wind.
what’s the rmp of the thing? 1000rpm
what’s the rmp of the thing? 1000rpm
It would only behave like that if one were to test its step response.
Fed with real signals it would just generate "sound" as any conventional woofer except being capable of more SPL than any cone woofer ever could achieve.
Regards
Charles
I think I have an idea of something a 1 or 2hz sounds (or more like feels) like. My roomate after showering would swing his towel in verticle circles with his right hand just inbetween and perpendicular to the door frame connecting the bathroom with the office in our apartment to diffuse the steam from showering.
Because the room is pretty small, and the bathroom has a pretty large V_as, my roomate essentially becomes a fan subwoofer producing infrasonic waves. Its a kinda wierd feeling, like a slow helicopter, where you feel the waves like they are pulsating in your head and body.
Too bad I can't hook up my roomate to an amplifier...
Because the room is pretty small, and the bathroom has a pretty large V_as, my roomate essentially becomes a fan subwoofer producing infrasonic waves. Its a kinda wierd feeling, like a slow helicopter, where you feel the waves like they are pulsating in your head and body.
Too bad I can't hook up my roomate to an amplifier...
lol nice….. it would be good if I could feel that!! You’ll have to experiment with it to see whats the best way to do it. get him to dance to the music with the towel.😉
Btw is the air coming out of a port played at say 10hz the same as a pressure wave thing? or is it just air?
Well, it's ALL just air, but when there's periodic movement of the air, it has the potential to create pressure waves, and thus sound. In fact, that IS sound, though sometimes the frequency or level causes it to be inaudible to us. In the case of a port at 10hz: In a typical ported sub, 10hz is going to be well below the tuning point. In that situation, the port and the driver will be mostly operating out of phase. There will be positive pressure directly in front of the port when there's negative pressure directly in front of the driver, and vise versa. At such long wavelengths, the (opposite) pressure waves will have mostly cancelled each other out by the time they reach us. Of course, at 10hz, our hearing sensitivity is pretty low, so even if we were talking about a theoretical ported sub tuned at or below 10hz (such that the port and driver were operating in phase), it would take a lot of output for us to actually hear it.
Thanks
just say I had 5 10” subs that had 48mm p2p excursion in a small box with a big 10” port at the front all tuned at low frequency 10hz and lower would that produce sort of the same effect?
I’m very interested in this fan sub 😀
just say I had 5 10” subs that had 48mm p2p excursion in a small box with a big 10” port at the front all tuned at low frequency 10hz and lower would that produce sort of the same effect?
I’m very interested in this fan sub 😀
I was looking for feedforwarding on the internet and then i found this:
http://www.analog.com/library/analogDialogue/archives/34-02/noise/
maybe nice to use with a fan subwoofer??
http://www.analog.com/library/analogDialogue/archives/34-02/noise/
maybe nice to use with a fan subwoofer??
If the fan sub works like a helicopter with collective pitch and spinning fast, it’s going to create a lot of unwanted noise
It's not spinning fast, about 300rpm IIRC.
It does create some unwanted noise due to the motor driving the fan, that's why it's only suitable for IB usage for now.
It does create some unwanted noise due to the motor driving the fan, that's why it's only suitable for IB usage for now.
simon5 said:
That, and the fact that such a relatively low speed fan probably couldn't overcome the back-pressure of an enclosure. Compared to a regular driver, a fan is good for displacement, but not pressure.
questions
ive been reading on the net everything i can find about the rotary type transducer, and can't sleep at night because i need to make one, even a very rough model will do, just to better understand replicating infrasonics and hopefully use one in an art installation for the reasons of direct mental and pysical effects of infrasonics on the body. yes, i have read about the dangers to humans and weapons use of the "deadly" 7hz wave machines ect, and do not plan on specificaly focusing that energy for sustained periods on people or animals, that said
questions i have
someone said earlier that all the blades pitch at the same time, unlike a helicopter fixed swash.
i was hoping you could expound on that idea,
it seems like each blade should be pitching independently of the other blades, this is my largest stumbling in understanding the principle of this type of device, besides that i suck at math, but i have spent alot of time studying the geo project and pictures of bruce's rotary, it looks like every model has been different so far, being hand made and working out details, how important is shape of the blade, some pictures the blades are smaller and rounded rectangles, and others are sleek and curvey, all the blades i assume are flat, so they have zero resistance at zero signal, and should be made of a stiff material, maybe steel, so they resist warping as they pitch,
i have basic welding and soldering skills, and access to a metal and wood shop, good ability to scavange componants, but not much cash or math skilz,
if anyone has built a test rotary sub, please lend a picture, or advice, bruce made one, so can we
ive been reading on the net everything i can find about the rotary type transducer, and can't sleep at night because i need to make one, even a very rough model will do, just to better understand replicating infrasonics and hopefully use one in an art installation for the reasons of direct mental and pysical effects of infrasonics on the body. yes, i have read about the dangers to humans and weapons use of the "deadly" 7hz wave machines ect, and do not plan on specificaly focusing that energy for sustained periods on people or animals, that said
questions i have
someone said earlier that all the blades pitch at the same time, unlike a helicopter fixed swash.
i was hoping you could expound on that idea,
it seems like each blade should be pitching independently of the other blades, this is my largest stumbling in understanding the principle of this type of device, besides that i suck at math, but i have spent alot of time studying the geo project and pictures of bruce's rotary, it looks like every model has been different so far, being hand made and working out details, how important is shape of the blade, some pictures the blades are smaller and rounded rectangles, and others are sleek and curvey, all the blades i assume are flat, so they have zero resistance at zero signal, and should be made of a stiff material, maybe steel, so they resist warping as they pitch,
i have basic welding and soldering skills, and access to a metal and wood shop, good ability to scavange componants, but not much cash or math skilz,
if anyone has built a test rotary sub, please lend a picture, or advice, bruce made one, so can we
You want all blades to have the same pitch at the same time because you want each blades to produce the same sound. If some blades are lagging behind others, they might cancel some sound or barely increase it. You want all blades working together.
so, ive been looking at the helicopter swash plate setups and thinking for a few days, it seems that we could simply connect a very stiff wire or rod from the blade shaft directly to the copper circle that is connected to the voice coil, but i have suspicions that this wouldnt work, that the force of the magnet would be overwhelmed trying to move the blades, i got a 50 watt speaker that i will dissassemble later tonight maybe,
so, do i need to drill a hole in the magnet for the motor shaft to go through?
im thinking the voice coil magnet assmebly goes between the blades and the actual motor, elliminating the swash plate would mean that the voice coil assembly would have to rotate with the blades, could be an issue, and may have to go back to looking at swash plate design
can anyone help me find a 300 rpm motor for this?
hopefully i will get a chance to experiment with the speaker i got, and post soon
so, do i need to drill a hole in the magnet for the motor shaft to go through?
im thinking the voice coil magnet assmebly goes between the blades and the actual motor, elliminating the swash plate would mean that the voice coil assembly would have to rotate with the blades, could be an issue, and may have to go back to looking at swash plate design
can anyone help me find a 300 rpm motor for this?
hopefully i will get a chance to experiment with the speaker i got, and post soon
so i have come to a design that i will cheaply be able to build and test,
the voice coil pitch mechanism will be on the opposite side from the motor power source, im going to use a dewalt cordless drill for the first tests, this seperation will save me from drilling through the voice coil metal magnet assembly. i have access to a drill press so that might be an option if its nessicary
i will try to scavange some steel from the studio for the blade assembly, then worry about the voice coil. there is alot of little detail to make sure the blades all pitch to the same degree
the voice coil pitch mechanism will be on the opposite side from the motor power source, im going to use a dewalt cordless drill for the first tests, this seperation will save me from drilling through the voice coil metal magnet assembly. i have access to a drill press so that might be an option if its nessicary
i will try to scavange some steel from the studio for the blade assembly, then worry about the voice coil. there is alot of little detail to make sure the blades all pitch to the same degree
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