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Advantages of beryllium?

Can someone please explain the advantages of beryllium drivers over titanium or aluminum?

Also, how concerning are health risks associated with beryllium?

many thanks for your input. 
defiantboomerang
kosst_amojan
2,095 posts
 
@shadorne 

Kinda like this?
https://www.stereophile.com/content/focal-aria-936-loudspeaker-measurements
That's what a pretty clean plot looks like with the exception of the excursion seen around 16kHz, which IS the resonance of the tweeter, which also reveals itself in the impedance/magnitude plot. That is NOT it's point of break up though. The internal damping of a Be tweeter is pretty much irrelevant because it's so easy to push it well beyond it's pass band. You seem to be confusing that with mechanical damping of the suspension. That's an entirely different matter. 
You seem to enjoy making broad, unequivocal statements about tweeter materials that don't reflect the reality. 
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mmeysarosh
124 posts
 
@shadorne 

Completely ignoring the point and instead demonstrating some odd ideology that isn't mat-sci. The notable aspect about Stereophile measurement is the result is system based, which I do not know if the Seas is the same and can not be compared. What does it mean? The decay energy being seen isn't just from the tweeter, but the interactions being produced by the system. This includes the mid driver, which the review states wasn't well isolated and was the source to the decay energy seen here. In order to have a clean plot, obviously the driver needs come to a rest as quickly and cleanly as possible. Energy that isn't well damped through the basket, the interface between the basket and the baffle, the baffle, behind the driver, and from other drivers will show in the plot. So your in a system and the diaphragm material plays a part, but in this test, its demonstrated to be more than itself as being the cause of the delayed decay.

Now where a well damped diaphragm material has its advantage is when you do happen to hit a resonance in the operating range, the material itself  will reduce the level through internal damping. As you pointed on the Focal tests, the Ti driver performance wasn't good but the Be is better. Did you even note that Ti has much better internal dampening than Al or Be? So it isn't the material selection in this case, but issues with the system instead. Any material can be tripped by poor design. Use a material, work within its constraint, and spend a greater effort in design over material selection.

As for the Kef, I believe that small notch in the treble may have something to do with the tangerine wave guide they use. Seems to be a solution compromise to the fairly wide and even dispersion in the upper treble. A number of speakers fall off to the sides, which make room balance a slight bit more of an effort to get right. If you look at the dispersion of it, the Reference 5, or the Blade 2, they all exhibit the same trait and treble radiation smoothness. Though right above 16khz, the sound field has less smoothing and is the point were we see that notch. They even use somewhat differing materials as the upper series use a Al-Li-Mg alloy. My guess is being the mathematical point in its physical design of that wave guide as its highly linear.
shadorne's avatar
shadorne
7,333 posts
 
@kosst_amojan

Obviously some implementations are better than other. My statement pertains to the problem of lack of internal damping in most metallic drivers (magnesium being perhaps a notable exception).

I count 5 resonances on the Focal Aria tweeter lasting up to 1.5 msec. These resonances are much much longer than the wavelength of the sounds that tweeter emits (an eternity in terms of PRAT) and will definitely color the sound in the way I described.

The resonances are multiple as a rigid disc has multiple resonant modes. I know this for sure as I have large collection of Sabian, Zildjian and Paiste cymbals and they shimmer with all kinds of non harmonic tones. A cymbal is an exaggerated example but the same principle stands.

If you want to hear musical timbre you need a driver that is critically damped - being inert it just gets out of the way once the desired movement is executed.

2 msec of waterfall hash on the first example I gave is really going to affect everything: the timbre of transients on percussive instruments (twang of guitar strings) to the articulation of sbilance on vocals.

The high but very narrow or sharp resonance peaks sometimes seen on JA plots is something to do with his measurement setup - you can ignore those - they look too narrow to be real effects.

FWIW the best waterfall plot I have seen, apart from the one on the Joseph Audio speaker linked above, is on a Quad electrostatic. So for those people who can hear what a difference a good electrostic speaker makes audibly in timbre then you can appreciate how a rigid tweeter can be coloring the sound in the way I describe.
shadorne's avatar
shadorne
7,333 posts
 
@randy-11

Interesting link. I think they sum it up very well. Be is better in the very top octave than Aluminium or Titanium (10 to 20 KHz)

Note that on the plots Be is not necessarily the best from 3 to 10KHz (the really important range musically for the tweeter). This is the point I am trying to make about internally damped drivers - better performance over a narrower frequency range. If the sound from 10KHz to 20KHz is most important to you then Be is the way to go (at the expense of more resonance at 3KHz to 10KHz)

As as far as I am concerned there is not so much musically in the 10K to 20KHz range - so I prefer a tweeter that performs better from 3KHz to 10 KHz.
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