Subwoofer capable of killing the listener?

[MvonB]

http://www.eminent-tech.com/RWbrochure.htm

[Arny Krueger]

"MvonB" > wrote in message


> http://www.eminent-tech.com/RWbrochure.htm

The rated

Maximum acoustic output >110dB between 0 and 30Hz.

This spec is kinda ambigious, but the device were capable of 120 dB, you'd
think they would set the spec that high.

120 dB below 20 Hz is something most have experienced by opening car windows
at say 70 mph. Not only won't it kill you, you might not even think it is
all that loud. I won't even activate "the brown note" effect.

Note that true subwoofer fanciers like Nousaine rate woofers in terms of
output on the order of 120 dB @ 10 Hz.

BTW Maggie, nice job of making yourself look like a fool on AAPLS.

[John Atkinson]

Arny Krueger wrote:
> "MvonB" > wrote in message
>
> > http://www.eminent-tech.com/RWbrochure.htm
>
> Note that true subwoofer fanciers like Nousaine rate woofers
> in terms of output on the order of 120 dB @ 10 Hz.

The Eminent can do that easily. See, for example,
http://blog.stereophile.com/cedia2006/091906soundfield/
and
http://blog.stereophile.com/cedia2006/091606thigpen/

In the first photo, the subwoofer is outputting 8Hz at
115dB spl in the room next door.

John Atkinson
Editor, Stereophile

[Walt]

MvonB wrote:

Subwoofers have been capable of killing people for decades. Just drop
one on the listener from a height of 50 feet.


//Walt

[Arny Krueger]

"John Atkinson" > wrote
in message
ups.com
> Arny Krueger wrote:
>> "MvonB" > wrote in message
>>
>>> http://www.eminent-tech.com/RWbrochure.htm
>>
>> Note that true subwoofer fanciers like Nousaine rate
>> woofers in terms of output on the order of 120 dB @ 10
>> Hz.

> The Eminent can do that easily. See, for example,
> http://blog.stereophile.com/cedia2006/091906soundfield/
> and
> http://blog.stereophile.com/cedia2006/091606thigpen/

> In the first photo, the subwoofer is outputting 8Hz at
> 115dB spl in the room next door.

Trivial observation: 115 < 120.

Second observation, delivering 115 dB to a hotel room doesn't take as much
effort as delivering 120 dB to a good-sized listening room.

Third observation, distortion is only speced at a relatively weak 90 dB
SPL.

[John Atkinson]

Arny Krueger wrote:
> "John Atkinson" > wrote
> in message
> ups.com
> > Arny Krueger wrote:
> >> "MvonB" > wrote in message
> >>
> >>> http://www.eminent-tech.com/RWbrochure.htm
> >>
> >> Note that true subwoofer fanciers like Nousaine rate
> >> woofers in terms of output on the order of 120 dB @ 10
> >> Hz.
>
> > The Eminent can do that easily. See, for example,
> > http://blog.stereophile.com/cedia2006/091906soundfield/
> > and
> > http://blog.stereophile.com/cedia2006/091606thigpen/
>
> > In the first photo, the subwoofer is outputting 8Hz at
> > 115dB spl in the room next door.
>
> Trivial observation: 115 < 120.

Correct, but that was the level in the other room, according to a
spectrum analyzer. I also witnessed a IHz tone at the same level,
but I found it compeletly inaudible. Bandwidth extended up to
25-30Hz, so this is a a true_sub_woofer.

> Second observation, delivering 115 dB to a hotel room doesn't
> take as much effort as delivering 120 dB to a good-sized
> listening room.

True, but the room the Eminent subwoofer was operating into
was neither small nor a hotel bedroom. It was ameeting room
measuring around 15' x 25', if I remember correctly.

> Third observation, distortion is only speced at a relatively
> weak 90 dB SPL.

I couldn't hear any harmonics along with the 8Hz tone,
though there may have been some masking from the
noise of the furnishings/walls/ceiling rattling :-)

Harmonics visible on the spectrum analyzer were in the
few per cent.

And remember, this is with _one_ drive-unit and 30W
of amplification. No reason (other than financial) to
use multiple units.

What did you think of this subwoofer when you heard
it, Mr. Krueger?

John Atkinson
Editor, Stereophile

[MvonB]

"John Atkinson" > wrote in message
ps.com...
>
> Arny Krueger wrote:
>> "John Atkinson" > wrote
>> in message
>> ups.com
>> > Arny Krueger wrote:
>> >> "MvonB" > wrote in message
>> >>
>> >>> http://www.eminent-tech.com/RWbrochure.htm
>> >>
>> >> Note that true subwoofer fanciers like Nousaine rate
>> >> woofers in terms of output on the order of 120 dB @ 10
>> >> Hz.
>>
>> > The Eminent can do that easily. See, for example,
>> > http://blog.stereophile.com/cedia2006/091906soundfield/
>> > and
>> > http://blog.stereophile.com/cedia2006/091606thigpen/
>>
>> > In the first photo, the subwoofer is outputting 8Hz at
>> > 115dB spl in the room next door.
>>
>> Trivial observation: 115 < 120.
>
> Correct, but that was the level in the other room, according to a
> spectrum analyzer. I also witnessed a IHz tone at the same level,
> but I found it compeletly inaudible. Bandwidth extended up to
> 25-30Hz, so this is a a true_sub_woofer.
>
>> Second observation, delivering 115 dB to a hotel room doesn't
>> take as much effort as delivering 120 dB to a good-sized
>> listening room.
>
> True, but the room the Eminent subwoofer was operating into
> was neither small nor a hotel bedroom. It was ameeting room
> measuring around 15' x 25', if I remember correctly.
>
>> Third observation, distortion is only speced at a relatively
>> weak 90 dB SPL.
>
> I couldn't hear any harmonics along with the 8Hz tone,
> though there may have been some masking from the
> noise of the furnishings/walls/ceiling rattling :-)
>
> Harmonics visible on the spectrum analyzer were in the
> few per cent.
>
> And remember, this is with _one_ drive-unit and 30W
> of amplification. No reason (other than financial) to
> use multiple units.
>
> What did you think of this subwoofer when you heard
> it, Mr. Krueger?
>

He was preoccupied with chromosomes and missed it but I'm sure he'll ask
Nousaine how it sounded so he can convey his opinion of it to the rest of
us.

Cheers,

Margaret

[George M. Middius]

Into the back pages of the "debating trade" manual we go.

> > The Eminent can do that easily. See, for example,
> > http://blog.stereophile.com/cedia2006/091906soundfield/
> > and
> > http://blog.stereophile.com/cedia2006/091606thigpen/

> > In the first photo, the subwoofer is outputting 8Hz at
> > 115dB spl in the room next door.

> Trivial observation

Chapter 58, "Last Ditch Measures to Provoke an Argument out of Nothing",
gives us the following guideline:

"The Debating Trade warrior, failing to find the tiniest shadow of an error,
makes trivial observations* in hopes of bestirring his enemy into an angry
tirade at his ****fulness."



__________________________

* A "trivial observation" is an argumentative or obstreperous post that is
designed to incite exasperation in humans, who otherwise foolishly attempt
to communicate in a constructive manner.






--

Krooscience: The antidote to education, experience, and excellence.

[Arny Krueger]

"John Atkinson" > wrote
in message
ps.com
> Arny Krueger wrote:
>> "John Atkinson" > wrote
>> in message
>> ups.com
>>> Arny Krueger wrote:
>>>> "MvonB" > wrote in message
>>>>
>>>>> http://www.eminent-tech.com/RWbrochure.htm
>>>>
>>>> Note that true subwoofer fanciers like Nousaine rate
>>>> woofers in terms of output on the order of 120 dB @ 10
>>>> Hz.
>>
>>> The Eminent can do that easily. See, for example,
>>> http://blog.stereophile.com/cedia2006/091906soundfield/
>>> and
>>> http://blog.stereophile.com/cedia2006/091606thigpen/
>>
>>> In the first photo, the subwoofer is outputting 8Hz at
>>> 115dB spl in the room next door.
>>
>> Trivial observation: 115 < 120.
>
> Correct, but that was the level in the other room,
> according to a spectrum analyzer. I also witnessed a IHz
> tone at the same level, but I found it compeletly
> inaudible.

When reproduced with sufficient acoustic power, not heard but definately
sensed.

> Bandwidth extended up to 25-30Hz, so this is a
> a true_sub_woofer.

Agreed - and this is a consequence of the method of operation.

>> Second observation, delivering 115 dB to a hotel room
>> doesn't take as much effort as delivering 120 dB to a
>> good-sized listening room.

> True, but the room the Eminent subwoofer was operating
> into
> was neither small nor a hotel bedroom. It was ameeting
> room measuring around 15' x 25', if I remember correctly.

Agreed that 15 x 25 is a decent-sized listening room. It is like mine if you
further specify a 9 foot ceiling.

>> Third observation, distortion is only speced at a
>> relatively weak 90 dB SPL.

> I couldn't hear any harmonics along with the 8Hz tone,
> though there may have been some masking from the
> noise of the furnishings/walls/ceiling rattling :-)

Agreed, those are natural consequences of deep bass at a loud enough level.

> Harmonics visible on the spectrum analyzer were in the
> few per cent.

If it can do say 120 dB @ < 10% THD, why don't they say it?

> And remember, this is with _one_ drive-unit and 30W
> of amplification. No reason (other than financial) to
> use multiple units.

The 30 watt number is misleading. This is a speaker driver that works on the
principle of modulation. I see no specification for the power input to the
motor that provides the airflow that is modulated.

> What did you think of this subwoofer when you heard
> it, Mr. Krueger?

I didn't have the pleasure. Was it demoed at HE2005?

[John Atkinson]

Arny Krueger wrote:
> "John Atkinson" > wrote
> in message
> ps.com
> > Harmonics visible on the spectrum analyzer were in the
> > few per cent.
>
> If it can do say 120 dB @ < 10% THD, why don't they say it?

I have no idea. You should ask Bruce Thigpen at Eminent
Technolog, Mr. Krueger. I am only reporting what I
witnessed.

> > And remember, this is with _one_ drive-unit and 30W
> > of amplification. No reason (other than financial) to
> > use multiple units.
>
> The 30 watt number is misleading.

No, this was the rated power of the audio amplifier being used
to modulate the fan blades' angle of attack.

> This is a speaker driver that works on the principle of
> modulation.

That is correct. That is what I discussed in my Show blog
entries to which I gave the URLS earlier.

> I see no specification for the power input to the
> motor that provides the airflow that is modulated.

I don't see that it matters, as long as it has sufficient
torque/motive force. You can see from the photo that
a small electric motor, perhaps a couple of HP, rotates
the blades.

John Atkinson
Editor, Stereophile

[MvonB]

"John Atkinson" > wrote in message
ups.com...
>

> I have no idea. You should ask Bruce Thigpen at Eminent
> Technolog, Mr. Krueger. I am only reporting what I
> witnessed.
>

And as usual, Arnii was reporting on something he didn't witness. In fact I
doubt Arnii has witnessed anything lately that didn't float in his toilet
bowl.

Cheers!

Margaret

[Arny Krueger]

"John Atkinson" > wrote
in message
ups.com
> Arny Krueger wrote:
>> "John Atkinson" > wrote
>> in message
>> ps.com
>>> Harmonics visible on the spectrum analyzer were in the
>>> few per cent.
>>
>> If it can do say 120 dB @ < 10% THD, why don't they say
>> it?

> I have no idea. You should ask Bruce Thigpen at Eminent
> Technolog, Mr. Krueger. I am only reporting what I
> witnessed.

Unh, it was a rhetorical question.

>>> And remember, this is with _one_ drive-unit and 30W
>>> of amplification. No reason (other than financial) to
>>> use multiple units.
>>
>> The 30 watt number is misleading.

> No, this was the rated power of the audio amplifier being
> used to modulate the fan blades' angle of attack.

Next time John, try reading a bit further before jumping to a questionable
conclusion.

>> This is a speaker driver that works on the principle of
>> modulation.

> That is correct. That is what I discussed in my Show blog
> entries to which I gave the URLS earlier.

Which means that unlike most speakers, the devices power input is not taken
entirely from the amplifier.

>> I see no specification for the power input to the
>> motor that provides the airflow that is modulated.

> I don't see that it matters, as long as it has sufficient
> torque/motive force. You can see from the photo that
> a small electric motor, perhaps a couple of HP, rotates
> the blades.

If the motor is really a 2 hp motor, then it needs special wiring of one
kind or another. That is unless the 2 HP rating is made up out of the same
kind of whole cloth as is used with vacuum cleaner motors.

If the pictures I've seen are any indication, the motor might develop 1/2 hp
if it spun at 1725 rpm, which it doesn't. I seem to recall that its actual
speed is 800 rpm, so it might be rated at 1/4 hp.

All things considered, I would expect this woofer to generate more spurious
noises given as a percentage, when operating at low levels. IOW, the largest
source of spurious responses would be turbulence generated by the fan
blades, which is always spinning. It would not be classic IM or THD but
rather modulation distortion plus an increase in background noise.

[John Atkinson]

Arny Krueger wrote:
> I would expect this woofer to generate more spurious noises
> given as a percentage, when operating at low levels. IOW,
> the largest source of spurious responses would be turbulence
> generated by the fan blades, which is always spinning.

This is correct. As I wrote in my blog, the fan fires into a
foam-lined box about 5' on a side, which you can see in
my photograph. This then communicates with the room
in which the sound is being experienced via a 2'x2' hole
in the wall. The is arrangement does effectively filter the
fan turbulence noise, as no sound could be heard at all
with the blades feathered and no intermodulation or
other noise modulation effects could be heard with pure
tones.

The fan _was_ noisy in the room in which it was operating,
but that is irrelevant given that that is not the room in
which it producing useful sound.

I found it very impressive, but its requirements really
restrict its possible market to industrial set-ups,
like special LF effects at a theater or amusement park.

John Atkinson
Editor, Stereophile

[George M. Middius]

John Atkinson said:

> What did you think of this subwoofer when you heard
> it, Mr. Krueger?

What an outrageous attack, John. Have you no pathos?




--

Krooscience: The antidote to education, experience, and excellence.

[John Atkinson]

Arny Krueger wrote:
> If the pictures I've seen are any indication, the motor might
> develop 1/2 hp if it spun at 1725 rpm, which it doesn't. I
> seem to recall that its actual speed is 800 rpm, so it might
> be rated at 1/4 hp.

I meant to include this in my previous response. You're
probably correct, Mr. Krueger. As long as the fan motor
has enough motive force/torque to keep spinning at a
constant rpm when the blades change their angle of
attack, that is sufficient.

As I understand it, the subwoofer's dynamic range is
ultimately limited by the fan blades stalling at
extreme angles.

John Atkinson
Editor, Stereophile

[Arny Krueger]

"John Atkinson" > wrote
in message
ups.com
> Arny Krueger wrote:
>> If the pictures I've seen are any indication, the motor
>> might develop 1/2 hp if it spun at 1725 rpm, which it
>> doesn't. I seem to recall that its actual speed is 800
>> rpm, so it might be rated at 1/4 hp.
>
> I meant to include this in my previous response. You're
> probably correct, Mr. Krueger. As long as the fan motor
> has enough motive force/torque to keep spinning at a
> constant rpm when the blades change their angle of
> attack, that is sufficient.
>
> As I understand it, the subwoofer's dynamic range is
> ultimately limited by the fan blades stalling at
> extreme angles.

I see a number of limits, mostly related to noise created by turbulence.
Stalling is probably the final brick wall, but there are other smaller
problems along the way. Turbulence isn't just a problem for a speaker like
this, it can also affect speakers in ported enclosures.

[[email protected]]

Several things come to mind after looking at this device:

1. Has the fan blade shape and number been optimized for minimum noise?
That would make installation simpler. Take a look at the previous
generation of nuclear sub propeller blades (the current generation is
classified).
http://americanhistory.si.edu/subs/anglesdangles/taming6.html

2. The motor appears to me to be an AC induction motor of ~1/2 HP. I'd
guess it takes ~1/8HP to spin that fan at 800RPM. Would a smaller
motor, maybe brushless DC or hysteresis, be quieter?

3. There were attempts in the past to use LF sound as a weapon. Pick a
frequency that nauseates a soldier/target. One could increase the
diameter and RPM of the fan and replace the voice coil blade pitch
control with a mechanical coupling of fixed frequency and put the
result in the throat of a big horn. Gutblaster!

Tim

John Atkinson wrote:
> Arny Krueger wrote:
> > If the pictures I've seen are any indication, the motor might
> > develop 1/2 hp if it spun at 1725 rpm, which it doesn't. I
> > seem to recall that its actual speed is 800 rpm, so it might
> > be rated at 1/4 hp.
>
> I meant to include this in my previous response. You're
> probably correct, Mr. Krueger. As long as the fan motor
> has enough motive force/torque to keep spinning at a
> constant rpm when the blades change their angle of
> attack, that is sufficient.
>
> As I understand it, the subwoofer's dynamic range is
> ultimately limited by the fan blades stalling at
> extreme angles.
>
> John Atkinson
> Editor, Stereophile

[John Atkinson]

wrote:
> 1. Has the fan blade shape and number been optimized for
> minimum noise? That would make installation simpler.

According to Bruce Thigpen, most of the development work
involved investigating and optimizing the shape of the fan blades.

It was indeed to odd to stand in a 1Hz 115dB soundfield
and not actually _hear_ anything.

Which reminds me of a jioke I was once told by the late
Michael Gerzon:

Q: What do you call very low-frequency sound?

A: Weather.

John Atkinson
Editor, Stereophile

[[email protected]]

John Atkinson wrote:
> wrote:
> > 1. Has the fan blade shape and number been optimized for
> > minimum noise? That would make installation simpler.
>
> According to Bruce Thigpen, most of the development work
> involved investigating and optimizing the shape of the fan blades.

I emailed Mr. Thigpen and he made a very informative reply. He says
they tried 100's of fan blade shapes.

Tim

[Howard Ferstler]

wrote:
> John Atkinson wrote:
>
wrote:
>>
>>>1. Has the fan blade shape and number been optimized for
>>>minimum noise? That would make installation simpler.
>>
>>According to Bruce Thigpen, most of the development work
>>involved investigating and optimizing the shape of the fan blades.

> I emailed Mr. Thigpen and he made a very informative reply. He says
> they tried 100's of fan blade shapes.

I did an evaluation of this subwoofer design in the
July/August 2006 issue (number 104) of The Sensible Sound. I
live in the same town as Bruce and not only heard the unit
installed in a car but also heard a larger sample installed
in the attic of his home.

I am not sure if the device is suitable for most audio
buffs, but it certainly did generate impressive bass for its
size. It is also the only subwoofer I have heard that has a
driver with a S/N ratio.

Bruce Thigpen is one of the most innovative (and honest)
speaker designers that I know of.

Howard Ferstler

[Clyde Slick]

Howard Ferstler a scris:
> wrote:
> > John Atkinson wrote:
> >
> wrote:
> >>
> >>>1. Has the fan blade shape and number been optimized for
> >>>minimum noise? That would make installation simpler.
> >>
> >>According to Bruce Thigpen, most of the development work
> >>involved investigating and optimizing the shape of the fan blades.
>
> > I emailed Mr. Thigpen and he made a very informative reply. He says
> > they tried 100's of fan blade shapes.
>
> I did an evaluation of this subwoofer design in the
> July/August 2006 issue (number 104) of The Sensible Sound. I
> live in the same town as Bruce and not only heard the unit
> installed in a car but also heard a larger sample installed
> in the attic of his home.
>
> I am not sure if the device is suitable for most audio
> buffs, but it certainly did generate impressive bass for its
> size. It is also the only subwoofer I have heard that has a
> driver with a S/N ratio.
>
> Bruce Thigpen is one of the most innovative (and honest)
> speaker designers that I know of.
>
> Howard Ferstler

That answers the original question.
If there were a subwoofer capaqble of killing the listener,
Howard would already have one, aqnd he would be dead.

[George M. Middius]

Brother Horace the Self-Hating Audiophobe said:

> I am not sure if the device is suitable for most audio buffs,

Sounds like you're admitting you're clueless about what "audio buffs"
appreciate.

> but it certainly did generate impressive bass for its size.

Excuse me, Clerkie, but where are the "test" results on which you're basing
your claim? It takes so little effort to do a level-matched evaluation of
two or more equivalent components. What you're offering here is a completely
worthless, egregiously-flawed™, totally off-the-wall "test" results. Clearly
your own biases prevented you from using any sicccnnecce to analyze the
performance of this "impressive" sub.

How much did Mr. Thigpen pay you for this shameless shilling? You ought to
be ashamed, Harold.





--

Krooscience: The antidote to education, experience, and excellence.

[Kalman Rubinson]

On Sat, 09 Dec 2006 12:08:13 -0500, Howard Ferstler
> wrote:

>I am not sure if the device is suitable for most audio
>buffs, but it certainly did generate impressive bass for its
>size.

It is actually quite large as the relatively small mechanism requires
a rather large intermediate enclosure to buffer the output. In the
demo I attended, the listening room was a roughly 12x22 hotel room and
the adjacent and similar room was partitioned with roughly 2/3 behind
the driver and the other 1/3 as that buffer between driver and
listening room. To me, that makes it a pretty large subwoofer that
is, nonetheless, very impressive.

Kal

[John Stone]

On 12/9/06 5:54 PM, in article ,
"Kalman Rubinson" > wrote:

> On Sat, 09 Dec 2006 12:08:13 -0500, Howard Ferstler
> > wrote:
>
>> I am not sure if the device is suitable for most audio
>> buffs, but it certainly did generate impressive bass for its
>> size.
>
> It is actually quite large as the relatively small mechanism requires
> a rather large intermediate enclosure to buffer the output. In the
> demo I attended, the listening room was a roughly 12x22 hotel room and
> the adjacent and similar room was partitioned with roughly 2/3 behind
> the driver and the other 1/3 as that buffer between driver and
> listening room. To me, that makes it a pretty large subwoofer that
> is, nonetheless, very impressive.
>
But not really a subwoofer. More like a sub-subwoofer. With a 20Hz
recommended xover, unless you've got really serious full range speakers,
you'll still need a regular sub. It is impressive, but I see it very much as
a rich person's toy. You would need incredibly stable and solid walls,
floors, and ceilings, along with bolting everything down that sits on a
shelf. Otherwise everything just rattles like mad, and the flexing walls
will actually cause cancellation between the front and rear wave. Another
interesting phenomenon is that the motor speed has to be adjusted for to
altitude. In Denver, Bruce increased it from 700 to 800RPM.

[Kalman Rubinson]

On Sat, 09 Dec 2006 19:16:36 -0600, John Stone >
wrote:

>But not really a subwoofer. More like a sub-subwoofer. With a 20Hz
>recommended xover, unless you've got really serious full range speakers,
>you'll still need a regular sub. It is impressive, but I see it very much as
>a rich person's toy. You would need incredibly stable and solid walls,
>floors, and ceilings, along with bolting everything down that sits on a
>shelf. Otherwise everything just rattles like mad, and the flexing walls
>will actually cause cancellation between the front and rear wave. Another
>interesting phenomenon is that the motor speed has to be adjusted for to
>altitude. In Denver, Bruce increased it from 700 to 800RPM.

Yes and he had to brace the intervening wall!!

Kal

[Arny Krueger]

"Kalman Rubinson" > wrote in message


> It is actually quite large as the relatively small
> mechanism requires a rather large intermediate enclosure
> to buffer the output. In the demo I attended, the
> listening room was a roughly 12x22 hotel room and the
> adjacent and similar room was partitioned with roughly
> 2/3 behind the driver and the other 1/3 as that buffer
> between driver and listening room. To me, that makes it
> a pretty large subwoofer that is, nonetheless, very
> impressive.

This seems to be a band-pass enclosure.

[Kalman Rubinson]

On Sun, 10 Dec 2006 11:50:38 -0500, "Arny Krueger" >
wrote:

>"Kalman Rubinson" > wrote in message

>
>> It is actually quite large as the relatively small
>> mechanism requires a rather large intermediate enclosure
>> to buffer the output. In the demo I attended, the
>> listening room was a roughly 12x22 hotel room and the
>> adjacent and similar room was partitioned with roughly
>> 2/3 behind the driver and the other 1/3 as that buffer
>> between driver and listening room. To me, that makes it
>> a pretty large subwoofer that is, nonetheless, very
>> impressive.
>
>This seems to be a band-pass enclosure.
Well, a low pass filter at the very least. Gotta get rid of the
actual fan noise even though it is pretty quiet.

Kal

[Fella]

George M. Middius wrote:

>
> John Atkinson said:
>
>
>>What did you think of this subwoofer when you heard
>>it, Mr. Krueger?
>
>
> What an outrageous attack, John. Have you no pathos?
>

Logos? I beleive his amp is a Krell or somesuch.