4D Theater effect of wind swirling in the home theater - Fans/Blowers/Discussion - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 171 Old 10-19-2018, 10:43 AM - Thread Starter
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Cool 4D Theater effect of wind swirling in the home theater - Fans/Blowers/Discussion

@stitch1 and I were talking about the fun air swirling effect of a slot port subwoofer...We both really enjoy it, but we currently have sealed subs and aren't sure we want to give them up for various reasons.

This thread was created to brainstorm and evangelize means to deliver that air swirling effect in home cinema.



EDIT: --

Here are the ideas being tested and implemented so far:


@Archaea - via etauro (light organ style device) - Post 63
https://www.avsforum.com/forum/155-d...l#post59004824

@Nalleh - via etauro (light organ style device) - Post 93
https://www.avsforum.com/forum/155-d...l#post59110728

@SOWK and @SirMaster - via custom DIY program solution and IR fans with L/M/H fan speed timestamps to exactly replicate in the movie timeline only when the fans should spin up and what strength. - Post 118
https://www.avsforum.com/forum/155-d...l#post59622614
@SOWK guide to cosmetically cover fans - Post 121
https://www.avsforum.com/forum/155-d...l#post59627568
Video Demonstration - Post 128
https://www.avsforum.com/forum/155-d...l#post59631140
@SirMaster 's Application that sends IR signals per timestamp - Post 160
https://www.avsforum.com/forum/155-d...l#post59690708
SOWK's Pastebin repository for Fan TimeStamp files
https://pastebin.com/u/SOWK







------------------(back to the original first post

Amplifiers put out A/C power from what I read - so really any A/C fan is candidate...


Is there anything keeping an enthusiast from installing a couple blowers aimed at the theater seats, setting a steep LPF at like 25 or 30hz (so only the deepest bass material generates the breeze), and hooking the amplifier up to one of the AVR subwoofer outputs. Something like the iNuke DSP 1000 would allow you to limit the voltage output so you wouldn't fry your fan motor with too much voltage. But would the smaller voltage transients from the general soundtrack cause damage to the fan motor by not having enough voltage to spin it up, and therefore severely undervolting the fan during most of the movie soundtrack? Do you think the fan could spin up fast enough to make this viable with on screen explosions? A small delay is perfectly okay in my experience with ported subs. You see an explosion on screen, and a moment later you get the effect of that wind blast - the slight delay works just fine.


Maybe a blower or squirrel cage fan buried behind a baffle wall with just the fan mouth exposed... If the fan motor could spin up fast enough - noise wouldn't be a problem because you'd tune the rig so only the biggest heaviest bass explosions in your room would have the voltage to spin up the fan.


If you're reading this and thinking -- "Why would anyone want this???" I don't care. Obviously there are at least two guys that do want this.


How many CFM do we think we'd need to get this effect to the seats? Say at 12' from the front wall... 500CFM? 1500CFM? more?

Some of these units could almost just be dropped in room and not be too cosmetically imposing: For instance:
https://www.walmart.com/ip/1200-CFM-...87&athena=true

I wonder what fan design would be most effective for this type of use case? Squirrel cage fan? Vornado fans?
Vornado fans seem like they could almost be custom made for such an experiment with a design that specifically directs airflow at a point.
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post #2 of 171 Old 10-19-2018, 11:09 AM
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I think you would want the fan spinning at a lower rpm and then cranking up at certain points. Getting it started is harder as the motor gets bigger. Possibly put a light flap in front of the opening so the low speed breeze doesnt get noticed, heavy enough to block initially. Pick up a variable fan speed controller for $20 and see how you like the effect in real time.
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post #3 of 171 Old 10-19-2018, 11:56 AM
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Wikipedia - Rotary woofer
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post #4 of 171 Old 10-19-2018, 12:32 PM - Thread Starter
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Quote:
Originally Posted by fill35U View Post
I don’t need more output. I have eight 18” sealed subs now. Instead I’m looking to regain the wind effect that looks something like this:


Also I went to a 4D theater at LEGOLAND with my kids that was kind of fun. They had the snow, rain(mist), and wind effects to compliment what was going on screen - as well as ambient lighting changes around the theater room to reflect what was going on - on screen.
Overkill yes, but still kind of fun. I don't need any of that, but it might be fun to reproduce the wind effect alone. I know it's possible because they did it in a theater sized space for all the seats. I think they were using giant blower fans all along the top of the screen. I didn't hear the fans running normally - but you could hear them spin up when they were working hard. (still the fan sound was relatively subtle.)

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post #5 of 171 Old 10-19-2018, 01:02 PM
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I can see the benefit of where this is going.
How much breeze? Like this.....


Or more in line like this....


Not sure how crowsons work but I think an actuator would work to trigger the fan but how much wind to produce would need some sort of control to ramp up and down according to Hz..
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post #6 of 171 Old 10-19-2018, 01:07 PM - Thread Starter
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Quote:
Originally Posted by BCRSS View Post
The green dress gif nails it, slight rustling of clothes is fine, even just the subtlety of the air moving hairs on the human body's legs/arms is a tactile effect that is fun that you miss out with sealed subs until the volume goes thunderous. I'm not looking to upskirt my guests.

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post #7 of 171 Old 10-19-2018, 01:16 PM
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Another thought or question is how would a person funnel that breeze/wind from a fan? Ports usually have a long throat to push the breeze a fan would need something to simulate that also .
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post #8 of 171 Old 10-19-2018, 01:17 PM
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Haha, AWESOME...
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post #9 of 171 Old 10-19-2018, 01:35 PM - Thread Starter
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another thing I was just thinking off... If trying to run the fans directly off the amp - I wonder if class D switching output of something like the iNuke would grenade a electric motor? I've always read that you are supposed to get a true sine wave UPS to run an electric motor and not a cheaper stepped sine wave UPS (to serve as a battery backup for something like a sump pump's electric motor.) Does the concept apply here at all? I have a couple A/B old Crown XLS 202 and 402 amps I could use to test if an iNuke is a bad idea.

paging @notnyt

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post #10 of 171 Old 10-19-2018, 01:42 PM
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Quote:
Originally Posted by Archaea View Post
another thing I was just thinking off... If trying to run the fans directly off the amp - I wonder if class D switching output of something like the iNuke would grenade a electric motor? I've always read that you are supposed to get a true sine wave UPS to run an electric motor and not a cheaper stepped sine wave UPS (to serve as a battery backup for something like a sump pump's electric motor.) Does the concept apply here at all? I have a couple A/B old Crown XLS 202 and 402 amps I could use to test if an iNuke is a bad idea.

paging @notnyt

Pretty sure the switching freq on the inukes are high enough not to matter.
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post #11 of 171 Old 10-19-2018, 02:56 PM
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The millions of PWM motor drives in service in industry, HVAC, and power tools show that motors can do just fine off a Class D amp. That said, filtering and cabling between the amp/drive and the motor, and the construction of the motor, can have a lot to do with longevity.

Engineering a system to drive a motor can be tricky business. And right now you don't have any performance specifications nailed down.

I mentioned the rotary subwoofer, not because I thought you needed ULF, but to consider the approach. A fan at constant RPM is easy to design a drive for. Then all you have to do is vary the fan pitch. The fan pitch is much more responsive, and requires very little power to activate. I'd check out RC/drone swashplates. A trip to the local hobby store might even get you *everything* you need.
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post #12 of 171 Old 10-20-2018, 12:39 PM
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DIY Speakers and Subs > Interesting DIY rotary subwoofer project

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post #13 of 171 Old 10-20-2018, 01:52 PM
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Hook this up to an actuator or driver motor.


https://www.amazon.com/Can-You-Imagi...dp/B00009B1SF/


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post #14 of 171 Old 10-20-2018, 05:27 PM
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Quote:
Originally Posted by Archaea View Post
I'm not looking to upskirt my guests.
Why not?
I want a system so loud it knocks the clothes of women.

Instead of bassheads, we can now all call ourselves airheads.

On a serious note though, rotary woofers are legit but:
THIS IDEA WON'T WORK
At least... not how you are going about it thus far.

The duration is too small!!!

and
in order to generate on-the-fly DBox vibs or AC blower instructions or smoke/mist/smellovision would require pre-delayed video/audio or pre-encoded movie meta-data (which is how DBox works... i.e. ain't no real-time on-the-fly stuff)

That said:
You could "fake it" convincingly...
The effects coming from the fans would be a delayed-action.
In that case, you could just use normal DC fans.
This would STILL require you to learn a programming language and interfacing with a relay controller system (to activate the fans automatically by command), similar to what I built a few years ago for power control automation for the rack of AV gear.

You'd have to code your own DSP software algorithms though. Which is a highly-advanced skillset. Basically you need to calculate the frequency with an FFT (frequency /amplitude gating), and then also the duration (attack/release gating), and use that as the basis of how you would activate the fans.

The good news is that you could reuse this logic for a DBox-like effect using chair hydraulics.


All of this sounds highly-obtuse and esoteric, even for me...
(and that's saying something... )
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post #15 of 171 Old 10-20-2018, 05:51 PM
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The other downside is that these effects would get old fast (i.e. annoying).

Sounds fun in-theory, but having your hair and clothes being blasted and misted every other minute would likely detract from the movie or music.

At the very least you'd definitely want a master On/Off button for this effect, controllable by your phone.

It would also require LOTS of free time and effort to code and rig up (and some money.)
As a result it would have a very low ROI me thinks.
There will be LOTS of hair pulling and hair loss. Most STEM tasks cause extreme presidentialing of the hair
Making your own DSP effects-engine to do all this definitely qualifies...

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post #16 of 171 Old 10-20-2018, 06:37 PM
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To get you moving towards a solution you'd need
this: https://www.kmtronic.com/
this: https://visualstudio.microsoft.com/vs/community/
this: https://github.com/naudio/NAudio
and this: https://www.amazon.com/C-Dummies-Ste.../dp/0764508148
(or other such comparable equivalents...)

I have/own all 4 of those already, I'm just too tired, lazy and faded to attempt it myself.
If you use those technologies I could guide you, but you'll have to do all the leg work yourself.
The learning-curve is too astronomical for almost everyone.

Any C language is "hard enough" to learn as-is, but toss in the DSP programming stuff (NAudio etc) and it becomes: ALIENS
Sufficiently indistinguishable from pure magic. (Even though it's 99.99% coded already...)

Lots of multidimensional data buffer array use/management, as well as audio-specific algebra, specifically...
Requires a full understanding of bit depth, sampling rates, as well as Frequency-amplitude and Time-amplitude manipulation of the array data.
https://en.wikipedia.org/wiki/Fast_Fourier_transform
http://www.drdobbs.com/cpp/a-simple-...atio/199500857
https://en.wikipedia.org/wiki/Sampli...nal_processing)
https://en.wikipedia.org/wiki/Audio_bit_depth
https://docs.microsoft.com/en-us/dot...ramming-guide/
https://docs.microsoft.com/en-us/dot...nsional-arrays
https://www.amazon.com/Digital-Signa.../dp/1856179214

I figure you'll be reading/learning/practicing this stuff for months before being ready to tackle that project.
The good news is that most of the knowledge can be googled and youtubed for free. It's all there.

Lots of brain hert will be involved.
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post #17 of 171 Old 10-20-2018, 06:43 PM
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Or just eat a lot of Taco Bell. Boom!
Instant wind on demand.
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post #18 of 171 Old 10-21-2018, 03:36 PM
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I love the idea. The problem i see is that transients dont last long enough for a fan to ramp up to blow air at you, you would need to use compressed air and have the bass transients activate a valve to open momentarily.
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post #19 of 171 Old 10-22-2018, 02:57 AM
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Quote:
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I love the idea. The problem i see is that transients dont last long enough for a fan to ramp up to blow air at you, you would need to use compressed air and have the bass transients activate a valve to open momentarily.
Exactly.

Having 1 or 3 of the fan's total blade count go from 0-degrees to 180-degrees and back, isn't gonna push any air at all, even with the fans superglued to your forehead at point-blank range. Which is one of the points I made above.

Even the rotary-woofer, the air becomes turbulent in the mid-bass. Which drops the SPL to 0.
There is also a problem with the moving-mass of the blades, the blades also have to be strong to resist flying apart. Balsa wood is lighter but the blades would fly apart instantly. Light things are weak. Ribbed carbon-fiber is about as good as it gets.

You have to "fake it" with DC fans or compressed air, pulsed with software, either derived as I described, or with pre-known metadata. You could leave the fans on and just have a relay-controlled shutter, that would greatly reduce the spin-up delay.

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Why is this desirable? I suppose you guys want to install sprinklers to drench yourselves when a movie has rain in it, too? Realism aside, not all or even most bass sounds would have air blowing. If your bass is loud and you don't have air blowing now, then there you go.

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post #21 of 171 Old 10-22-2018, 05:25 AM - Thread Starter
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Originally Posted by markmon1 View Post
Why is this desirable? I suppose you guys want to install sprinklers to drench yourselves when a movie has rain in it, too? Realism aside, not all or even most bass sounds would have air blowing. If your bass is loud and you don't have air blowing now, then there you go.


Reading comprehension fail...
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post #22 of 171 Old 10-22-2018, 11:50 AM
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I got the easy-button here. Build some ported 10-12hz cabinets and call it You could even cut your driver count down afterwards. Maybe start with 4 and go from there...

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post #23 of 171 Old 10-23-2018, 05:37 AM
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Quote:
Originally Posted by SteveCallas View Post
I love the idea. The problem i see is that transients dont last long enough for a fan to ramp up to blow air at you, you would need to use compressed air and have the bass transients activate a valve to open momentarily.
I think this is the best idea. Using a fan wouldn't produce the same affect. You could just rig a release button right in front of the sub so when the excursion hits it, the air fires - easy peasy

On a serious note, it would probably require some relays and programming to have it fire when the wave peaks on either the positive or negative side. That would mimic the airflow from a port. The issue with that, however, is there would most likely be too much noise from the actuator - similar to an air powered grease gun/jack.
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post #24 of 171 Old 02-08-2019, 12:21 PM - Thread Starter
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Bought one of these to test.


https://slickdeals.net/f/12781696-la...ipped#comments


I'll hook it up to a crown XLS202 on a subwoofer output channel. We'll see how it goes.
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post #25 of 171 Old 02-09-2019, 07:52 AM
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this might be better accomplished with variable pitch blades.

electric motors have some properties that may need to be worked around, such as their decreasing impedance with (decreasing) rpm, for example. applying full on voltage at very low rpm will drive huge current through the motor, which could cook the motor, the wiring, the amp, or other components. this tends to not be a problem with most fans because they spend very little time getting going. once turning at the speed for which they are designed, resistance rises, current declines and the fan can operate comfortably for extended duration. there are devices that are designed to provide compensation for this effect called variable frequency drives (vfd), which as their name suggests, adjust the voltage based on the frequency so as not to drive too much current through the motor at startup/low rpms. at a minimum, you may wish to switch the fan on and off at its operating frequency as compared with driving low and variable voltage through the motor.
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post #26 of 171 Old 02-09-2019, 10:48 AM
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Quote:
Originally Posted by Archaea View Post
We'll see how it goes.
My guess: a dead amplifier and no wind.

I'm guessing it is near 0-ohms across most of it's bandwidth, I'd be surprised if it were >2ohms... but who knows!
If you have a WT2 you could verify that before connecting it to the amplifier.

It likely has a 120V 60Hz AC to DC transformer in it, either SMPS or blob of copper.

Audio amplifiers can't output DC very well; and likely can't provide 1800W @ 60hz sinewave for long either (into 0-ohm, or whatever it is...)

If you can find a device that outputs variable DC, that is computer controlled. Now you might be getting somewhere. But you still need meta-data or a custom-written DSP engine.
Instead, you could make a panic-button or something. Panic-Wind... (copyright pending) hehe!

Last edited by BassThatHz; 02-09-2019 at 10:58 AM.
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post #27 of 171 Old 02-09-2019, 10:55 AM
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Would it be better to feed the audio signal to some sort of transistor to turn the fan on and off? I've used a very cheap transistor to turn LEDs on and off to lower frequencies in music but I don't know if that would work for much more AC power.
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post #28 of 171 Old 02-09-2019, 12:30 PM
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2 things come to mind.

That wind is the sub port getting huge output right at tuning, no?

#1 It can't be reproduced easily by a fan. In a sealed room those ports create huge pressure waves which u cant get with a regular fan.

#2 . A sub designer (several posted here already) would understand the port velocity bell curve and be able to design an expanded range in which a subs port is getting big m/sec.

As Beastaudio mentions, build subs with a few ported tunes specifically designed to create port output while balancing any chuffing problems. Lets say a bell curve of wind ouput at tune covers 20hz of range...build 2 or 3 with the right overlap so it has a somewhat consistent vent response. i.e. 1 sub covers 10 to 25, 1 from 25 to 40, a third from 40 to 55 say.

This actually seems easy, except for balancing the wind vs port noise.

Thats why we need sub designers/engineers to run with the concept.

Thoughts?
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post #29 of 171 Old 02-09-2019, 03:52 PM
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My first thought was also some kind of compressed air rig.

If trying fans...maybe use some old school high-current/low ohm-load stable car-audio amps. Back in my competition car-audio days I had a Phoenix Gold MPS2240 amp that could run down to half an ohm in stereo or one ohm bridged. There were other brands making similar style "cheater" amps back then including Orion with their HCCA line, US Amps, and others. These types of amps were high dollar units back in the day but now you can still find them often for pennies on the dollar.
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post #30 of 171 Old 02-09-2019, 06:59 PM
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Hah

Ported sub owners gave up sealed for more output at tune, while always trying for lower extension; and now sealed owners wishing for the air blast that only porting provides.


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