TS> I just thought the above system would offer some interesting design TS> 
challenges, and could trigger an interesting adjunct discussion about TS> 
little discussed transfer efficiency of drivers and coupling systems.
 TK> Well ? :)
As to driver type efficiency and accuracy of reproduction considerations, 
some of the best discussions I've seen have come from white papers written by 
JBL engineers, usually in the context of comparing desirable design traits of 
compression drivers with various alternatives.  
Thiele and Small certainly have considered such things, but usually from less 
direct perspectives.  I sort of wonder if white paper style material was 
widely published back when Klipsch was first competing with products like the 
EV Patrician on low frequency products.  
TS>   Of course, I was thinking about bone conduction 
TS> of sound to influence brain waves,
 TK> Oh dear....
That's a serious factor when considering why headphones can't produce the 
same perceived sound experience as a good speaker system and environment for 
some music, despite generally being easier to design for better response, 
distortion, stable platform, and freedom from room artifacts.  Of course, the 
NASA lauch pad where they use unusually high bias voltages on B&K condenser 
mics so as to not overload at 180 dBspl's could be another real world 
example, not to mention my old high school classmate who tests solid rocket 
boosters fired sideways at ground level out in the SW US deserts, working for 
Morton-Thiokol.  
Pistol shooting alone outdoors can be another interesting acoustic scenario, 
as short duration intense sounds can have much more energy (and cause more 
damage) than we realize hearing them.  More sustained muzzle blasts among a 
group of shooters at a range can be easier to perceive as loud.  Larger 
calibers and use of common in the ear protectors have the same problem 
musicians using off the shelf ear plugs have:  bone conduction bypass.  
That's where custom molded deep earplugs or over the head protectors are 
useful (not to mention acoustically flatter attenuators being available for 
custom deep molded earplugs).  
Of course, I was suggesting how sound can trigger subconscious alpha, beta, 
delta, and other brain wave patterns, pleasurably or with possible pain 
stimuli that aren't directly sensed as well as possibly with others that are. 
 
TS> and impose pleasure patterns in such intensity as 
TS> to be disorienting, or
TS> pain for more reasons than the listener would understand.
 TK> Why, on earth, would you like to cause pain anyway ?....
Well, we could go to an S&M echo....    
Anyone creative with audio, whether with technical or musical manipulations, 
should be able to understand what it takes to cause a variety of human 
responses, as a basic aspect of understanding how related human perceptions 
work.  Some people want pain, as a masking pattern, as a perceived need (kids 
associating high frequency distortion with desired loudness due to too many 
crappy stereos, masking more annoying physical pain, to interrupt and prolong 
pleasure stimuli, etc.), or for various other reasons.  I've thought about 
painful but also psychologically disorienting acoustic stimuli as having 
possible applications in a burglar alarm system so as to make a smash and 
grab crook less likely to stay focused in the time before police might 
respond, or for driving rabid church protesters from areas near abortion 
clinics, adult book and toy stores, etc.  We see higher frequency simplified 
versions of pain stimuli acoustic devices sold to drive away insects.  
Pain is a more basal reaction than most other human responses to stimuli.  
Learning tricks to trigger it when unexpected can be useful in also finding 
ways to powerfully attract attention or stimulate pleasure in various forms, 
though usually less predictably across an unknown group of people.  
TS> I really wasn't planning to raise the issues of living animal tissue TS> 
damage by sound a couple of serious sadists have 
TS> tried over the years.
 TK> so ?
Raw energy!  OTOH, something like phaco-emulsification is very focused sound 
used to remove cataracts from eyes without cutting.  
Are you familiar with the Crown 10 KW 3-phase input power amps, used more for 
industrial vibration tables than audio?  Could you picture a human attached 
to a table driven by 12 of those (4 corners by 3 axis directions)?  What 
would the acoustic experience be like if such an arrangement were used to 
reproduce audio by vibrating the listener in the surrounding air, rather than 
the other way around?  
TS> If the above spec's could be met without using more than 150 KW of AC TS> 
power, I'd qualify the system as having an 
TS> extremely efficient design if
TS> based on speaker cabinets.  Consumption of under a 
TS> megawatt max would place
TS> it in the realm of average small commercial systems.
 TK> There are cabinets with a 7% efficiency
Which would equate to around 102 dB/1W/1m.  OTOH, junky compression drivers 
run around 15%, and good ones nearly 35%.  Piezos run twice that or more, in 
exchange for distortion.  A 50-60% efficient compression driver could be 
produced, but it would have serious undamped resonance problems.  
TS> How many people here realize that at average home 
TS> system (in)efficiencies
TS> the above would require over 5 megawatts of line power in?
 TK> What IS the average ?.....84 dB/1W/1m ?......92db/1W/1m ?
Something like that.  I assume 90 dB average, and a fractional percentage 
efficiency.  
TS> Now, dropping some likely assumptions based on the thread, can you TS> 
picture a more efficient way of producing that 
TS> energy?  How about a pipe
TS> organ with about 40 HP of blowers, and a rank of 
TS> pipes out to 64' added?
TS> That could require under 50 KW of AC power in.
 TK> Never seen one with bigger than 16'....anyway, ik 
 TK> would be a nice vibration :)
Very little music calls for anything below 32 Hz.  My ideas for more 
subliminal psychoacoustics call for more ability to intermod at 5-14 Hz 
rates.  Either way, a pipe organ isn't very space-efficient, but it's often 
overlooked as to being a marvel of efficient musical transducers.  
TS> For comparison, the average moderately large 
TS> church pipe organ has 16'
TS> pipes and a 3 HP blower, while the largest Austin 
TS> organ I've ever been
TS> inside uses a 15 HP blower, a ton of different 
TS> special pipes on two air
TS> chests about 6.5' x 15' x 30', but wouldn't 
TS> produce sound below 16 Hz or at
TS> the required volume (1922 World's Fair organ in Philly is one of the TS> 
largest in the world).
 TK> Sydney Operahouse Organ... dated somewhere in the '60 I guess...
The one I described is in a university 3 story octagonal auditorium in 
Philadelphia now, maintained by a 30 person volunteer group plus some organ 
contractors (LOTS of electro-pneumatic solenoids).  It's unusual in that the 
ranks are split between sides of the hall, and aren't up front or rear with 
possible added trumpets or effects as with most organs.  I'm always impressed 
at a musician who can play such an organ well with active works, as the time 
delay to the console is hundreds of milliseconds, near a rather confusing 
syllabic period.  The performer needs to know how to produce the desired 
sounds without being able to monitor in real time much more than most 
musicians can handle.  
What's the Sydney organ like?  
Terry
--- Maximus 2.01wb
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