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Thigpen Rotary Woofer - Page 8  

post #211 of 837
3/27/06 at 4:49pm
Quote:
Originally Posted by Morbius
Mark,

Yes - the Master & Commander cannon scenes would be good. I installed my theater seating on
a raised wooden platform to which is attached a Buttkicker "tactile transducer".

Whenever I play Master & Commander scenes of cannon shot hitting the sides of the ship, I'm
treated to the unmistakeable sound of wood "in distress". I'm not sure if that's the soundtrack or
the actual wood of the platform responding to the throws of the Buttkicker

Any way you cut it - it's a "E-Ticket" ride.
We really need to get you into e-Motion!

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post #212 of 837
3/28/06 at 6:16am
Quote:
Originally Posted by Mr.Poindexter
We really need to get you into e-Motion!
Mr. Poindexter,

I was quite impressed with the demo you did at tzucc's theater.

I recall that we were watching the "pod race" scene from Star Wars I: The Phantom Menace.

It really felt like I was in the pod along with Anakin. When I got out of the chair to return to the
chair I had been sitting in - I decided to lean against the wall for a bit before attempting to walk
across the room.

A few minutes in that chair was not unlike a few hours out on the Bay in a sailboat.
post #213 of 837
3/29/06 at 1:01am
Thank you. That demo was pretty intense, but most films are not that way all the way through. Rendezvous is an exception to the rule there.

We were watching Finding Nemo the other day and that is excellent in how much motion there is and it is all pretty nice and laid back - just adding to the swimming feeling. I think it is a better demo than the intense programming and I may just use that as my primary demo material now. I do believe that Jeff was on the platform when we had a few Nemo clips going.
post #214 of 837
3/29/06 at 7:09am
Quote:
Originally Posted by Mr.Poindexter
Thank you. That demo was pretty intense, but most films are not that way all the way through. Rendezvous is an exception to the rule there.
Mr. Poindexter,

I don't think I could take a motion simulation of "Rendezvous". I cringed just watching it without
the motion. :eek:
post #215 of 837
3/31/06 at 7:18pm
Quote:
Originally Posted by Mr.Poindexter
Thank you. That demo was pretty intense, but most films are not that way all the way through. Rendezvous is an exception to the rule there.

We were watching Finding Nemo the other day and that is excellent in how much motion there is and it is all pretty nice and laid back - just adding to the swimming feeling. I think it is a better demo than the intense programming and I may just use that as my primary demo material now. I do believe that Jeff was on the platform when we had a few Nemo clips going.
I really thought it added something to the movie - made it more realistic. It was subtle but gave that extra something that one doesn't experience by just watching in a stationary seat.
post #216 of 837
4/3/06 at 9:10am
Quote:
Originally Posted by brucet
If in fact infrasound causes anything close to some of the symptoms described in previous post and others around the internet then I think we would see many more health problems where the cause could be traced to "infrasound". Infrasound in fact is all around us, sometimes at very high levels.
I know of specific examples where infrasound caused nausea in a work environment with high levels of continuos low frequency sound, but it only affected a small percentage of the workforce. I do not think this is the intent of a sound system.
I will try and plot sound levels while riding in a car where the infrasound content can be way beyond what we might imagine.
Sounds we experience everyday:
These are the peak levels of sound measured when you close a door in a room, NOT a door slam. The room was about 14 by 20 by 8 feet.

http://www.eminent-tech.com/avsimage...oorclosing.jpg


These are the sound levels you experience when you sit in your car and close the door, windows rolled up, also not a door slam. The doors represent the equivalent of a very large woofer cone, in effect you are sitting inside the woofer box.

http://www.eminent-tech.com/avsimage...oorclosing.jpg


I think the goal should be to reproduce these sounds at actual levels. (The measurement system is calibrated to 1Hz).

Bruce T


Are those low frequencies as charted actually sound pressure levels (SPL's) of a frequency, or is that just a chart of change in air pressure that is being observed???
post #217 of 837
4/3/06 at 1:00pm
Rather than posting in two places, I responded to J_Palmer's question in the thread where I referenced the measurements Bruce posted:
http://www.avsforum.com/avs-vb/showt...&&#post7423267
post #218 of 837
4/3/06 at 2:20pm
Mark's response on the other thread is correct, sound is simply changes in air pressure. I made those measurements with a microphone calibrated to 1Hz input into a calibrated sound card. You can directly convert measured sound levels to pressure. As an example 20 pascals = 120dB SPL = .0029PSI. SPL is the log of a ratio of two pressures.
If we can get a good installation in tzuccs room, I suspect everyone who attends will be able to hear between 5-10Hz "sound" without much difficulty.

Bruce T
post #219 of 837
4/3/06 at 2:31pm
Maybe this will help. These are measurements in a car with the windows open.

Here are two examples of low frequency sound levels while in a car with the windows down moving at 55MPH. The microphone was in the middle of the car at ear level. As you moved the microphone closer to a window the measured sound levels went up.

First measurement, all windows down in a BMW 4 door sedan. Here the noise is above the threshold at 11Hz and up, there is substantial low frequency energy present even at 55MPH.

http://eminent-tech.com/avsimages/ca...sdown55mph.jpg

We have all heard this inside a car. At speed on the highway With one rear window down we get a strong low frequency flutter. In this case the cavity of the car makes a very large whistle 112dB @ 18Hz which is way above the threshold and clearly audible.

http://www.eminent-tech.com/avsimage...wonly55mph.jpg

Obviously convertables and motorcylces would be louder. Trucks, buses, and airplanes would exibit higher levels of interior low frequency sound. Also if you go faster the noise level goes up. There are plenty of examples where we can experience high level very low frequency sound.

Bruce T
post #220 of 837
4/3/06 at 3:45pm
Good stuff Bruce, thanks for the additional examples!
post #221 of 837
4/3/06 at 5:31pm
Thread Starter 
Yes, my Land Rover LR3 with one window down makes such a massive LF flutter, it does actually hurt your ears. It seems to be in the 2-5Hz periodicity range, and was such a problem that Land Rover thought fit to include a note in their owners manual about opening all 4 windows to alleviate that effect.
post #222 of 837
4/3/06 at 6:19pm
Quote:
Originally Posted by tzucc
Yes, my Land Rover LR3 with one window down makes such a massive LF flutter, it does actually hurt your ears. It seems to be in the 2-5Hz periodicity range, and was such a problem that Land Rover thought fit to include a note in their owners manual about opening all 4 windows to alleviate that effect.
My BMW 740iL does exactly the same thing when either of the rear windows are down. Very painful
post #223 of 837
4/4/06 at 5:55am
same with my Viper GTS
post #224 of 837
4/4/06 at 7:07am
Thread Starter 
Does anyone remember this LF flutter phenomenon happening with older cars? I sure don't. Perhaps the windows used to be smaller relative to the cabin size? That's the only factor I could think of.
post #225 of 837
4/4/06 at 7:20am
Not an issue with my '86 Dodge Colt since the muffler rusted off. Now the LFE flutter is drown out by the engine.
post #226 of 837
4/4/06 at 7:52am
Quote:
Originally Posted by tzucc
Yes, my Land Rover LR3 with one window down makes such a massive LF flutter, it does actually hurt your ears. It seems to be in the 2-5Hz periodicity range, and was such a problem that Land Rover thought fit to include a note in their owners manual about opening all 4 windows to alleviate that effect.
Quote:
My BMW 740iL does exactly the same thing when either of the rear windows are down. Very painful
Quote:
same with my Viper GTS

Yeah, and so does my Ferrari, Porsche and Mercedes :D
post #227 of 837
4/4/06 at 8:00am
Actually, I've experienced this effect in older, cheaper cars, yes. Rolling down a second or third window solves it.
post #228 of 837
4/4/06 at 8:17am
For those experiencing these problems with expensive sports cars, I recommend my Toyota Camry. :D

- Terry
post #229 of 837
4/4/06 at 8:49pm
i remember an old hyundai pony that was so bad you had to warn people before rolling the windows down
post #230 of 837
4/4/06 at 10:03pm
I have that in my car also, but it happens when both windows are equally rolled down, or close to it. It seems like the windows basically slice off two semi-symmetrical streams of air, which meet in the rear of the car and slam into each other and just pulse with the slight changes in air pressure of the incoming streams. It can actually hurt my ears sometimes. I guess it helps to have a hatchback style car which provides a nice container for the pressure pulse to resonate in.
post #231 of 837
4/4/06 at 10:42pm
Quote:
Originally Posted by tzucc
Does anyone remember this LF flutter phenomenon happening with older cars? I sure don't. Perhaps the windows used to be smaller relative to the cabin size? That's the only factor I could think of.
In addition to the comments already made about examples that did exhibit this problem, the sleeker, more aerodynamic cars of today and the much quieter interiors tend to make the overly loud, higher frequency noise less pronounced. This makes it a bit easier to notice that low frequency energy that's still left over.

There's also the factor that you're much more bitten by the audio bug these days and pay attention to such things much more. ;)
post #232 of 837
4/7/06 at 2:34pm
A quick bump and heaven forbid, a post more on topic...

Tzucc & Bruce,

Have you sourced anything for crossover and possible EQ purposes? Which option did you go with or which ones are you considering?
post #233 of 837
4/7/06 at 2:56pm
Thread Starter 
Bruce will have to answer those questions... I am simply serving as the host and wine pourer.

I did get an email from him today, we're on track for everything as planned on Sat April 22.
post #234 of 837
4/7/06 at 3:57pm
Hey Tony, is it OK if an audio engineer friend of mine comes along?
post #235 of 837
4/7/06 at 4:00pm
Thread Starter 
Sure. I will try get an accurate headcount frozen by next weekend, but we should be fine.
post #236 of 837
4/9/06 at 7:12pm
Tony,
so it's definitely Saturday the 22nd, not Sunday the 23rd?
Terry
post #237 of 837
4/9/06 at 11:06pm
Thread Starter 
Yes, it is Saturday the 22nd... I finally learned how to read a calendar.
post #238 of 837
4/10/06 at 12:49am
Bruce, I fly r/c heli's also, and can verify that the blades do sing quite a bit when large pitch is applied (ie, steep banked turns with lots of collective....probably around 16 degrees of pitch)...

My friends flip out when I fly it overhead and they hear the blade slap, sounds real......

Assuming you have found a way to predictably recreate that sound, you have a believer out of me.

Quote:
Originally Posted by brucet

"This is kind of like a helicopter in that you spool up the blades to constant rpm and only vary pitch to implement the function?"

This was the epiphany, I was flying a model helicopter and watched it while moving the collective back and forth and said to myself, this is a speaker I have been looking for. Since I crashed a lot, I had plenty of spare parts and by noon the next day I had a working prototype.

Mark,

I will try and run some plots in a car and also some films we might have fun with. I should be able to post these in the next couple weeks. With regard to the torque load on the motor, read Marks description. We use a industrial motor controller to try and maintain constant RPM. The torque varies with the amplitude and frequency of the input signal. As frequency goes down, blade pitch goes up, the torque load on the motor goes up. The motor tries to keep the blades spinning . At the equivalent radiating area of 30 to 40 eighteen inch woofers and extremely low frequencies, the motor runs out of torque, (1/3hp) or if the rotational speed is too low the blades will stall because of a high angle of attack and the torque unloads.
The bottom line is does this approach have any value in home theater? I hope we can come to some conclusions about that. Thanks for the interest and let me know if there are more questions.

Bruce T
post #239 of 837
4/10/06 at 8:02am
Thread Starter 
interesting... I don't think that was Bruce's intent or message in your excerpt above, but it would be awesome if his fan sub could accurately reproduce or enhance the sound track of helo's in movies... that would be really really neat.
post #240 of 837
4/10/06 at 8:04am
Does the fan sub have a fan club? I know, not very punny.
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