[headchange4u]

Eminent Tech TRW 17

I saw this article yesterday. This is amazing. A sub capable of producing 1Hz FLAT and it looks like a fan.

 

[rsaavedra]

Quote:

Originally Posted by headchange4u Eminent Tech TRW 17 I saw this article yesterday. This is amazing. A sub capable of producing 1Hz FLAT and it looks like a fan.

Wow never thought of that but looks like a great idea. The fan spins at constant speed I'm sure, but depending on which low frequencies to play, the blades should swivel repeatedly and accordingly (similar to a helicopter's blade, but much faster) so as to create the exact pulsating sound at that frequency in the stream of air pushed by the fan. Great idea to achieve very low responses.

I do believe in the flatness of this sub, but they never mention SPL levels, I'm guessing it's not incredibly loud. Loudness is simply the amplitude of the wobble, the louder you want it, the farther the blades should wobble/swivel.

Also, the upper limit of its response is not mentioned. Those blades shouldn't be able to swivel too fast accurately, so the upper limit shouldn't be too high.

 

[NightWoundsTime]

And they're making a car version! SPL competitions are about to get even more insane, you'll be able to hear them from several miles away. Actually new regulations will be passed on such competitions that they have to be held on specially designed oil dampened absorbent platforms.

I don't think anyone has said yet whether this thing is self powered or if you have to find an amp to make the thing move.

 

[NightWoundsTime]

Quote:

Originally Posted by rsaavedra I do believe in the flatness of this sub, but they never mention SPL levels, I'm guessing it's not incredibly loud.

The second page has some comments from people at the Rocky Mountain convention saying the walls were fluttering like paper. I think that implies HUGE volume.

"The big fan—er, sub—with a blade diameter I'd estimate at 17-inches was operational, and clearly produced audible, high level output to at least 17Hz. Below that its action was more obvious in the way it shook everything in the rooms and, below 10Hz, caused the rooms' walls to literally flutter back and forth like a sheet in the wind. Scary, but impressive."

 

[rsaavedra]

Quote:

Originally Posted by NightWoundsTime The second page has some comments from people at the Rocky Mountain convention saying the walls were fluttering like paper. I think that implies HUGE volume.

No not necessarily, lots of stuff resonates with low frequencies, particularly large volumes of air within walls. I think that's why the walls rattled.

This device should be able to reproduce frequencies even fractions of 1Hz easily actually. What I'm wondering is how good and loud it can reproduce let's say 10-20Hz. From 0 to 10Hz sound waves supposedly just cause nausea and some general feeling of uneasiness/aprehension.

 

[rsaavedra]

Quote:

Originally Posted by NightWoundsTime "The big fan—er, sub—with a blade diameter I'd estimate at 17-inches was operational, and clearly produced audible, high level output to at least 17Hz.

Ah exactly, so around 17 Hz is more or less its upper limit. Wow 17Hz as upper limit! This shoudn't be called a subwoofer but an "infrawoofer". Actually, it doesn't have a "woofer" after all, what should we call this? Infra-sub maybe?

 

[JaZZ]

Great idea! I just wonder how it performs from 20 up to 100 Hz. It would be interesting to see measuring data, especially about harmonic distortion.


Quote:

Originally Posted by rsaavedra Ah exactly, so around 17 Hz is more or less its upper limit. Wow, 17 Hz as upper limit! This shoudn't be called a subwoofer but an "infrawoofer". Actually, it doesn't have a "woofer" after all, what should we call this? Infra-sub maybe?

If you read further, it's clear that the guy wasn't talking about the upper limit, but the lower limit of audibility:

"The big fan—er, sub—with a blade diameter I'd estimate at 17-inches was operational, and clearly produced audible, high level output to at least 17Hz. Below that its action was more obvious in the way it shook everything in the rooms and, below 10Hz, caused the rooms' walls to literally flutter back and forth like a sheet in the wind. Scary, but impressive."

 

[rsaavedra]

Quote:

Originally Posted by JaZZ Great idea! I just wonder how it performs from 20 up to 100 Hz. It would be interesting to see measuring data, especially about harmonic distortion.

No check Matt's quote, it seems its upper limit is already below 20Hz. Amazingly, the lower the frequency, the easier and more comfortable this sub works. Even 1 Hz shouldn't be a problem. That would correspond to just wobbling those blades once every second. But wobbling those blades 20 times per second is quite a mechanical engineering challenge.

 

[JaZZ]

Quote:

Originally Posted by rsaavedra No check Matt's quote, it seems its upper limit is already below 20Hz. Amazingly, the lower the frequency, the easier and more comfortable this sub works. Even 1 Hz shouldn't be a problem. That would correspond to just wobbling those blades once every second. But wobbling those blades 20 times per second is quite a mechanical engineering challenge.

No no... see my edited post above!

If you read further, it's clear that the guy wasn't talking about the upper limit, but the lower limit of audibility:

"The big fan—er, sub—with a blade diameter I'd estimate at 17-inches was operational, and clearly produced audible, high level output to at least 17Hz. Below that its action was more obvious in the way it shook everything in the rooms and, below 10Hz, caused the rooms' walls to literally flutter back and forth like a sheet in the wind. Scary, but impressive."

 

[rsaavedra]

Quote:

Originally Posted by JaZZ No no... see my edited post above!

Got it. Still I think upper limit of operation shouldn't be too high just because of mechanical constrainst. But anyway the specs sheet would dissolve this uncertainty.

 

[BOERteun]

And here it is:
http://www.eminent-tech.com/RWbrochure.htm

Quote:

Specifications: Amplifier Requirement 200 watts @ 8 ohms impedance 8 ohms 0Hz - 40Hz Frequency response 1Hz – 30Hz +/- 4dB suggested crossover 30Hz @ 18dB/octave Sensitivity 90dB 1 watt 1 meter @10Hz Maximum acoustic output >110dB between 1 and 30Hz. Distortion typically 3% or less between 1 and 30Hz @90dB Warranty – 3 years parts and labor Price $12,900 each, not including amplifier or crossover Patent Pending

 

[DrewWinters]

If it's producing "clearly audible" sound at 17hz, then I'd venture to guess that THD is rather high.

20hz is really a lower limit, not an average, to human hearing. In fact, most people can barely hear below 25 (give or take) and what you hear is mostly harmonics (same is true with 20khz, although there are some of us unfortunate souls who can hear up a bit past 20KHz) from our relatively (to the mains) inaccurate subs.

But I'm sure I'm preaching to the choir here...

EDIT: OH look! While I was typing, we got the specs... 3% at 90db would definitely be "clearly audible", especially at 110db where it's probably closer to 12% or even higher. I'd cross this sucker over lower than 30Hz if I intended to use it.

 

[JaZZ]

Quote:

Originally Posted by BOERteun And here it is: http://www.eminent-tech.com/RWbrochure.htm

 

[JaZZ]

Quote:

Originally Posted by DrewWinters If it's producing "clearly audible" sound at 17hz, then I'd venture to guess that THD is rather high.

Well, 3% is a quite normal value for woofers and not even bad for this range. It's not deniable that it may be audible though...

 

[rsaavedra]

I stand corrected, wow it goes quite higher than I would have thought. Quite a mechanical engineering achievement, no wonder it's that expensive.