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post #541 of 837 Old 05-02-2006, 07:38 AM
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Quote:
Originally Posted by brucet
Mark, tzucc,

120dB = 20 pascals = .0029PSI = about .4 pounds per square foot. You can use some of the internet conversion calculators to see if my memory is correct.

Bruce T
Thanks for the correction Bruce. That sounds and looks correct to me. I was a factor of 2 low in my earlier note.

Tzucc, as an example, this would mean that if you reach 120dB at your seats, your walls would in fact be seeing 126-130dB, at which point they would be presented with maximum pressures of 2-4 lbs. per square foot. While we most certainly react to pressures 1/10th to 1/100th of this level, remember that at low frequencies, the pressure is the same on all or most of our body. I wonder if an equivalent correlation to altitude change would be more meaningful a metric to anyone who's ever been to high altitudes before?

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post #542 of 837 Old 05-02-2006, 07:52 AM
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Quote:
Originally Posted by tzucc
just don't forget to make sure whatever you develop delivers on the SPLs necessary to make for a good demo.
Hehe... It's not often enough that people are telling me to make sure a subwoofer is loud enough. :rolleyes:

Thanks. I needed the motivation. :cool:

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post #543 of 837 Old 05-02-2006, 08:12 AM
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Can the room behind the screen and the 30 x60 x 5 Attic be used as an enclosure for this fan?

The room is apx. 30 x 30 x 8 with a central additional ceiling cove of 2.5 x 13 x 25 (as well as two semi-eliptical side coves).

The low ceiling heights preclude the use of any speakers that are not in a D'Appolito config.

http://gallery.avsforum.com/data/501..._ELEVATION.jpg

http://gallery.avsforum.com/data/501..._P_12_WIDE.jpg

I guess a remote controlled air valve could open a door to the exterior to vent Naples Bay (when wanting to show off the system).

Any thoughts?
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post #544 of 837 Old 05-02-2006, 08:21 AM - Thread Starter
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seems like the attic alone is plenty of room for the backvent.

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post #545 of 837 Old 05-02-2006, 09:07 AM
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What was the cu ft recommended for one of the infrasubs ?

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post #546 of 837 Old 05-02-2006, 09:10 AM - Thread Starter
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a good rule of thumb was the same space in the back as in the front. But even a 10:1 reduction in backside volume may make for an useful application, according to Bruce's analysis.

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post #547 of 837 Old 05-02-2006, 09:45 AM
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Quote:
Originally Posted by Art Sonneborn
What was the cu ft recommended for one of the infrasubs ?
Hi Art,

From what I recall of the attic space above your room, that would be a very workable option for the ET infrasub with the sub possibly vented in one of the front corners or even in the rear of the room. I'd be concerned about moving the screen if placed directly behind it.

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post #548 of 837 Old 05-02-2006, 10:31 AM
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So Mark ,you think in my room a few of these would be required ?

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post #549 of 837 Old 05-02-2006, 11:19 AM
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How many are needed depends on what exact iteration Bruce produces or offers. With room to work in the attic, I don't really see an reason you'd need much more than what one unit can provide, but two could make for a quieter system with equal or more headroom.

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post #550 of 837 Old 05-02-2006, 01:26 PM
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Quote:
Originally Posted by Mark Seaton
While we most certainly react to pressures 1/10th to 1/100th of this level, remember that at low frequencies, the pressure is the same on all or most of our body. I wonder if an equivalent correlation to altitude change would be more meaningful a metric to anyone who's ever been to high altitudes before?
The difference in pressure is not linear with altitude, so it isn't like changing 5,000 feet (just pulling numbers out of the air) of elevation unless you base it from sea level or the relevant elevation the person is used to and even then the change you go through takes quite a while. It took me a couple of hours to go from sea level to the top of Mauna Loa and we had to stop to take a break to let our bodies adjust. It just isn't the same as a short term difference in pressure.

It is hard to get all the impact of an event with just VLF bass, which is why I have always felt that when one goes to below about 15Hz the most effective way to get the sensation is via direct coupling and motion. While using an infra woofer is great as well, I personally believe that motion or tactile sensations are a better way to go if one has to choose one or the other. Of course, having both would be best. While Bruce's demo at Tony's was very impressive from an audio standpoint and people were getting very impressed it was incredibly tame compared to what I am used to.

For music, I would think the infrawoofer would be the absolute way to go over motion, but there just isn't that much need for it in music. Movies on the other hand, well they are going to sell a lot of these systems with the aggressive mixes coming out now.
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post #551 of 837 Old 05-02-2006, 01:39 PM - Thread Starter
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Spoke with Bruce and my HVAC guy today. Looks like we are moving forward with a twin fan solution. Bruce is working on a next gen hub with sealed bearings. I have one more check to perform with my contractor, but assuming that's copacetic, the path looks relatively clear to an elegant retrofit of the fan sub technology in my house.
Elegant meaning no external construction. Some drywall surgery inside the media room and garage above.

At some point, I will start another thread to chronicle the progress so as to keep you interested parties vicariously following along.

The target install timeframe is planned for 1st week of August.

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post #552 of 837 Old 05-02-2006, 01:41 PM
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post #553 of 837 Old 05-02-2006, 02:41 PM
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Quote:
Originally Posted by Mr.Poindexter
Just be sure to alert the nearest seismology lab...
Mr.Poindexter,

The United States Geological Survey [ USGS ] center is Menlo Park about 10 miles up the
road from Saratoga are the ones to notify:

http://quake.usgs.gov/

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post #554 of 837 Old 05-02-2006, 02:42 PM
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Cineramax,

The attic space available is more than adequate and would probably make for a excellent and relatively easy installation.

Art,

In your room the one concern I have is the projector installation. If the woofer is installed in the attic, the type of installation I use, the ceiling will move up and down (the pressures discussed earlier are doubled). If the projectors are suspended from the ceiling, then the image would blur on the screen. A few braces in the attic should solve the problem. Attic space usually represents an excellent choice. Thank you for the question.

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post #555 of 837 Old 05-02-2006, 02:44 PM
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Quote:
Originally Posted by tzucc
Elegant meaning no external construction. Some drywall surgery inside the media room and garage above.
tzucc,

That certainly is good to hear. Glad you are able to accomodate Bruce's subwoofer.

I think it will make a very welcome addition to your home theater experience.

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post #556 of 837 Old 05-02-2006, 02:48 PM - Thread Starter
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Joking aside, I will have to occasionally turn off the sub if my wife is in the house and not with me watching the movie... which is ironic. I went to great expense and personal effort to make this room sound proof so that the wife could never tell me to 'TURN IT DOWN" and Bruce just went and took me right back to the drawing board.

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post #557 of 837 Old 06-04-2006, 04:33 PM
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I have downrezzed my video of the subwoofer and uploaded it to the web.

It is large - 44.6MB

http://www.cinemawizards.com/videos/...60p24MPEG4.mov

I would recommend right clicking and saving the file since but it will stream out if you want - my server has decent pipes.

It was filmed at 1280x720 resolution, progressive at 24 frames per second using DVCPro HD codec at 40mbit bitrate in 4:2:2 color space. The clip has been resized to 640x320 and compressed in MPEG4. No color correction or post processing has been applied. The voices are mine and Tony's - Tony is telling me not to stand too close in case the sub breaks and kills me or something to that effect.

Sadly, I doubt the camera could pick up the VLF bass, but even if it did, I couldn't play it back on my computer. Maybe if somebody wants to do a waterfall on the sound file from the clip it would be interesting.

The sub is playing a sweep tone.
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post #558 of 837 Old 06-04-2006, 04:37 PM
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FYI, the original file was 302 MB - quite large for 51 seconds! It would have been 755MB if I recorded it in 720p60, 1080p30 or 1080i60 or 604MB if it was in 1080p24. None of them really conducive for internet downloading.
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post #559 of 837 Old 06-05-2006, 07:35 AM - Thread Starter
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wierd... when I right click to save the video both IE and FF lock up taking 100% of the CPU.

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post #560 of 837 Old 06-05-2006, 08:31 AM
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I downloaded it without any problems at home off the machine I used to upload it. I tried here at work and it started OK but stopped after 19.2MB. The video played fine until about 20-25 seconds into it.

A second attempt at downloading it worked much better. It downloaded in around 5 minutes and played fine.
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post #561 of 837 Old 06-05-2006, 09:31 AM
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I just downloaded it without any problems as well. Is it always on?

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post #562 of 837 Old 06-05-2006, 09:45 AM
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Hi Eric:

I would have a special button on the touchscreen panel to engage.
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post #563 of 837 Old 06-05-2006, 09:49 AM
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The server? Yes, it is dedicated web hosting - not coming off my home computer. I have asynchronous DSL at home and wouldn't subject anybody to trying to get that via "not-too-broad-band."
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post #564 of 837 Old 06-05-2006, 09:51 AM
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Rereading my post, I should have elaborated with two more words.:) Is the fan always on, even if it is not generating sound?

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post #565 of 837 Old 06-05-2006, 10:05 AM
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Yes, it is always on. It takes a while for the fan to build up momentum and that is required for it to work. When nothing is playing, the blades have no pitch. Also, the sound it makes isn't that loud - I was in a stairwell with concrete and tile on all sides. The other side had some baffling that cut down on the noise substantially and they didn't even have 2 turns in it like they would have preferred.
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post #566 of 837 Old 06-05-2006, 10:37 AM
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Quote:
Originally Posted by Mr.Poindexter
and they didn't even have 2 turns in it like they would have preferred.
?
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post #567 of 837 Old 06-05-2006, 10:43 AM
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They wanted two turns in the path for the bass to come out in order to reduce the high frequency noise generated by the fan.

It is a common tool used for acoustics to reduce higher frequency sound waves.
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post #568 of 837 Old 06-05-2006, 02:33 PM
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Mr. Poindexter,

I wanted to say thanks for the nice comments you made about the woofer on other forums. Here is a spectrogram of the two frequency sweeps shown on the footage. Its looks like the microphone and recording electronics on the camera are good to about 17Hz which is surprising.

Outside the signal to noise ratio of the woofer is not too good, about 30-40dB. This is the blue border around the signal. The first sweep is on the bottom and the second sweep is on the top. If I recall these sweeps were from Mark Seatons TEF analyzer and they went to about zero Hz.

On the footage to the right you can see the motor controller. This was run on 220VAC single phase. You can also see the motor trying to move from the thrust of the vanes during heavy pitching. These signals were at a fairly high level, about the limit of the amplifier we were using, 200 watts. Thanks very much for posting this.

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http://www.eminent-tech.com/avsimage...pectrogram.jpg
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post #569 of 837 Old 06-05-2006, 03:03 PM
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Quote:
Originally Posted by brucet
Mr. Poindexter,

I wanted to say thanks for the nice comments you made about the woofer on other forums. Here is a spectrogram of the two frequency sweeps shown on the footage. Its looks like the microphone and recording electronics on the camera are good to about 17Hz which is surprising.
WOW! 17Hz response - that is cool. This was taken using the on-camera mics. I didn't even have my good mics in yet. If I had my Audio Technica I think we would have had even better response.
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post #570 of 837 Old 07-12-2006, 04:10 PM
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How thick is the baffle which the fan is mounted to? It appears to be something like 1/2" or so thick. Would it help any to sandwich it against 1 to 2" of MDF. Just curious?

That's definitely cool as $#!+ :D

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