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In Reply to: RE: Need to add another word posted by claudej1@aol.com on June 10, 2023 at 04:28:32
so why is your post about Electrostatic Loudspeakers???
Only too happy to repeat. :)
Brad needs more than "a word" to define high-eff speakers. The one he chose is not unique to them.
Follow Ups:
Sorry my word is fine...it's your understanding about what is acceleration that is the issue.
If we consider the equation F=ma and it is the force that makes the amplitude then for a given mass, the acceleration determines the force.
You made a comment about how light the membrane is relative to the column of air it pushes...this is the moving mass but says nothing about the acceleration part of the equation.
So, even if the electrostatic membrane is the lightest moving mass in existence (not sure if that is true or not) the fact that the sensitivity is only 89dB (not that bad really but not what I would call high sensitivity) tells me that the electrostatic drive cannot generate that much force and therefore has a lowish acceleration compared to my Supravox drivers or my compression drivers.
"It is not a very long post, but if you are really busy, here is a TL;DR summary:
Displacement in speaker diaphragm does not generate the pressure wave in air that is the sound we hear. Acceleration does.
What causes the diaphragm to accelerate (and therefore the air in front of it to pressurize) is force. A lower acceleration only results in lesser sound pressure level (SPL), i.e. less loud, not how quickly it appears, i.e. the lack of speed.
The speed at which we can modulate "force" is unrelated to the mass of the diaphragm.
I'll expand a little further on Purifi's blog post, since someone will inevitability ignore the last point above and will insist that acceleration is force divided by mass, and therefore lower mass gives higher acceleration. So how do we find how much acceleration we need?
The late Siegfried Linkwitz (RIP) gave us a very handy formula to predict the free field SPL generated by a speaker driver, given its size, diaphragm travel, and frequency. [Link, see the box "Theory Behind the Nomographs"] It is:
SPL = 94.3 + 20 log10(x) + 40 log10(f) + 40 log10(d) - 20 log10(r)
where: x is the peak-to-peak diaphragm travel in meters,
f is frequency in Hz,
d is the effective diameter of the diaphragm in meters (d = sqrt(4 * Sd / pi), with Sd = effective area in m^2)
r is the listening distance in meters
Now, say we want to generate the same SPL at two different frequencies, f1 and f2, what will the diaphragm travels (x1 and x2) be?
SPL1 = 94.3 + 20 log10(x1) + 40 log10(f1) + 40 log10(d) - 20 log10(r)
and
SPL2 = 94.3 + 20 log10(x2) + 40 log10(f2) + 40 log10(d) - 20 log10(r)
Since we want SPL1 = SPL2 ,and "d" and "r" remain the same, we have:
20 log10(x1) + 40 log10(f1) = 20 log10(x2) + 40 log10(f2)
or
log10(x1) + 2 log10(f1) = log10(x2) + 2 log10(f2)
or
x1 * f1^2 = x2 * f2^2
or
x2 = x1 * f1^2/f2^2
So, the amount of travel the diaphragm needs to produce the same SPL in inversely proportional to the ratio of the frequencies squared (i.e. with the same diaphragm travel, SPL goes up/down by 12 dB/octave).
How about acceleration? Well, given the displacement amplitude x, acceleration = x * (2*pi*frequency)^2. Which means acceleration goes up by frequency squared. Since, for the same SPL:
x2 = x1 * f1^2 / f2^2
and
a2 = x2 * (2*pi * f2)^2
= x1 * (f1^2 / f2^2) * (2*pi * f2)^2
= x1 * (2*pi * f1)^2
= a1
The acceleration amplitudes are the same! And therefore forces. Amazingly we need the same force amplitude to produce the same SPL regardless of frequency. Of course, the rate of fluctuation of force is higher with higher frequencies, but the force magnitude is independent of frequency. We need to wiggle the diaphragm more frequently, but that is completely countered by the fact that we need to wiggle it less far.
There are plenty of other reasons why a woofer is not suitable to produce treble. Mass of the diaphragm ain't one."
that any of Siggy's designs are considered "high-eff"?
Is that why the LX521.4 "requires between 8 to 10 power amplifiers of 50 W to 200 W"?
Mass of the diaphragm ain't one.
More than the diaphragm moves. ;)
The LX 521.4 is an open baffle design to remove "the box resonances" and their phase issues.
More importantly, as a SYSTEM, that provides an AMAZING 3-Dimensional presentation of the Music in Space, where the Speakers themselves simply "Disappear" Acoustically speaking.
Their Figure 8 pattern inherently decouples the speakers from the room by Side Cancellations which "throw away" driver Efficiency to achieve all the goals of that type of reproduction.
Having owned 3 pairs of Caver Amazing speakers and helping a friend build his version of it (Six 10" drivers and on large Bohlender Graebener Planar Magnetic driver, side by side), the speakers have the unique presentation that is quite remarkable. The antithesis of my preferred All Horn systems.
Nevermind that he's using JC-1 Plus class A/AB power amps at 1 Horsepower Each to drive them, they just do sound Terrific, at a HIGH PRICE, for the hifi.
I only mention this in CONTRAST to the Horns People here, including me. IMHO, this type of system is not for the Weak Wallet types like me and other Klipscheads from that forum.
Most certainly not in the high-eff family.Never took a cotton to traditional Altecs/K-Horns but would like to hear one of Tom's synergy horns where all frequencies radiate from the same "mouth". In some respects they are like my Sound Labs in that they have controlled directivity and can be used in horizontal or vertical arrays since they are full range designs.
I discovered as a teen that I am particularly sensitive to driver blending issues and have no need for 100 db output. I suspect that music preferences play a role in determining one's optimal speaker approach.
Edits: 06/13/23
I have 3 Danley SH-50's in my full Atmos HT as front RCL channel for a 7.4.2 setup in my tiny Living Room. Also have Tom's prototype #3 of his companion TH-50 tapped horn Subwoofer that literally scares strangers with the right movie LFE.At the touch of a button on my Yamaha Pre Pro, I have 2.2 for Music instantly.
I bought a used pair of his Unity Summation Aperture TD-1 horns. I drove all the way from Indianapolis (at the time) to Buffalo, NY to get them from a DJ who had an extra pair. They easily fit in the trunk of my Toyota, at the time. I was blown away by the sound of those little horns, even without a sub.
So, sound unheard, I upgraded to a pair of SH-50s Brand New, in 2014, and a Hypex NC-400 Kit, also unheard. This combination makes the Chesky Drum Recording sound like the Drums are literally in my living room as certified by a few drummer friends who shook their heads in disbelief. This done in 2.2. Also the Center Phantom image is so sharp on a vocalist, that my friend have to stick their heads in the middle one to know it's not even on. Lots of FUN as the voice sounds like it's coming directly from the center of my big 4K TV with just Land R on. LOL
Now THIS is true HiFi!! Full Dynamics, driven by TI Chip amps, while I reduce the gain on my Hypexes.
My small space means I have to have the horns in corners, which boosts the bass, so I have to EQ them down. This way they perform way beyond the Spec , as flat to 40 Hz than crossed to the subs. I will never sell them as they are a lifetime speaker for me after owning every horn speaker imaginable, several DOZENS by now, and counting.
Edits: 06/13/23 06/13/23
more simply:Acceleration = Force/Mass
Same force, high mass → low acceleration = low SPL
Same force, low mass → high acceleration = high SPLThe relationship (for first order effects) is independent of frequency.
Or if you keep mass constant and increase Force then you get higher acceleration = High SPL
It is the acceleration that creates the pressure wave, not displacement and not velocity the rate of change of velocity (acceleration) creates the pressure wave and it's amplitude (SPL).So, in a word...acceleration defines sensitivity...how you get that acceleration (low mass, high magnetic strength etc.) is the balance played in driver design.
Edits: 06/12/23
"Acceleration is a red herring."
Which chums?
Who is Brad? (like we are supposed to know your friends on a public forum?).
and a 100 db/watt at 1 meter or calculated back at 10 meters in the case of a big E-stat is good enough NOT to need more words to define Sensitivity/Efficiency.
89 'aint cuttin it!
Who is Brad?
Sorry, he's the Swiss based chemist known here as "morricab".
89 'aint cuttin it!
That was my point from the outset. :)
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