Advantages of beryllium?

Here is a waterfall plot just for the Seas Excel Millenium fabric dome tweeter.

http://www.diyspeakers.net/snippets.org/ldsg.snippets.org/graphics/seas/e006w.gif

@mmeysarosh

The KEF R700 does measure well but the tweeter still has some hash and is not nearly as clean as the Seas Excel Millenium tweeter - see the outstanding lack of resonances (much better than any metal dome) in the waterfall plot for this speaker with the Seas Sonotex dome in their Excel Millenium tweeter (around 200 euros each!)

https://www.stereophile.com/content/joseph-audio-rm33si-signature-loudspeaker-measurements-part-2

@koost_amojan

You need to look for a clean waterfall with fast (damped) decay and no hashy stuff or resonances. The main resonant ringing is not normally in the audible band - my concerns are the additional resonances and lack of damping in rigid domes. The titanium dome on the JM Lab Utopia is up to 2 msec across the treble - this is a lot of vibration compared to something mostly clean or down 20 dB after 0.5 msec.

If a Be tweeter is properly constructed, there won't be any ringing in the audible band and well above it. While it has very low internal damping, implemented properly it is considered what would be called high damping, so rigid that it really doesn't resonate.

Now as for those delayed energy charts, look through all the measurements and read the comments. In the older Utopia, the mid driver wasn't well isolated and was impacting the tweeter and it does reach its breakup point is at 22khz and certainly does show. So there is a number of issues that design resulting in that measurement. Focal also didn't develop a great driver in this case as we have seen many other metal drivers of lesser material measure extremely well in the decay plots. Even Al, which should be one of the worst materials but has resulted in some of the better measurements is mainly due to the quality of implementation. The material certainly has an impact, but its use in design matters more. 

https://www.stereophile.com/content/kef-r700-loudspeaker-measurements

The Kef R700 uses a plebeian Al dome, but due to a designed shape and stiffening ring, measures perfectly clean. Kef uses just an alloyed version in the Reference and Blade series and gets the breakup point beyond 30khz. Associating a sound with material is for the most part is invalid and proper design and engineering is the correct answer. You can just as easily implement a fabric dome poorly and have messy decay plot due to energy coming elsewhere.

Those Focal speakers didn't achieve their designed goals and they likely knew it. Reached the end of the cycle and budget and released the product as it was, being the best they knew how to produce at the given time and a given cost. Looking at the Sopra 3, they still haven't quite gone as far as some other companies in spectral decay, but progress has been certainly made. 

beryllium is 1/3 lighter than aluminum yet 6x the specific stiffness of steel

IIRC, it outclasses Ti in that way - dunno re stress cracking but the newest Ti alloys are better than their reputation

the dust is highly toxic - ask Porsche who used them - briefly - on brake components of some race cars

might be fun to see if the German govt. allows Be in speakers - you can get away with putting toxic liquids in cables in Canada and importing them into the US though

Highly rigid and light but poor internal damping.

Personally I don’t like the splashy sound of drivers of this type design (metal and highly rigid). They have great bandwidth that makes for impressive measured performance but I find the sound is "splashy" due to the way rigid materials vibrate naturally (like a bell vibrates and rings after an initial hit but a damped material like a pillow does not).

Splashy is a good term - as in when you splash the water it makes a lot of sound after the initial splash. Acoustically this means the driver imparts its own sound to the timbre whereas an internally damped cone material is much more inert - contributing much less coloration after the sound stops.

I prefer damped designs even though they tend to have a narrower bandwidth and can suffer from breakup and therefore require more careful design and larger more expensive drive motors. Damped cones sound much more natural and faithful to the original tone/timbre of recorded instruments even if they are not as linear on a speaker frequency plot.

Here is an example of a titanium tweeter - look at the ringing in the waterfall plot in the treble !!!

https://www.stereophile.com/content/jmlab-utopia-loudspeaker-measurements-part-2

Here is an example of Be - similar problem in the treble but very much better than titanium

https://www.stereophile.com/content/focal-maestro-utopia-iii-loudspeaker-measurements

One good eye opener, listen to the Magico Be tweeters and compare to the Focal's.

Personally I find the tuning of the Magico's a bit bright, but butter smooth and wide dispersion spanks all the Focal's and certainly the B&W diamond tweets.

It's all in that luscious motor assembly that's behind it.

Best,

E

Don't be fooled just by the Be brand. They are not all equivalent, certainly not in frequency response or dynamic range.

In _theory_, be is very stiff and very light, so least stored energy or resonances of most materials.

The implementation of the suspension, motor, and overall speaker design is VERY important. Done well the best Be tweeters are among the best tweeters. But so are the best AMT's and ring radiators too!

Best,

E

Paradigm's new Persona line use's Truextent Beryllium mid/bass driver's and tweeter's in the entire line. 

In terms of the diaphragm, both Al and Ti have very similar stiffness with a given density. So when shaped, the weight will be quite similar between the to when targeting a specific stiffness performance, but the titanium part will thin in comparison due to its much greater density. Titanium will be somewhat more forgiving if over driven or out of bandwidth as it has greater internal dampening as compared aluminum alloys. So while Ti is a touch better than Al in overall performance, there is an added cost to its source and manufacture.

Be on the other hand can perform at much higher levels than either Al or Ti. A higher modulus than Ti and lower density than Al. This causes it to be highly damping, but not internally. Being very rigid, a Be diaphragm maintains is shape under a significantly high stress, but internal dampening is more about specific elasticity and this is where Be and Al share a commonality as neither have much elastic capability. Ti actually has quite a bit more elasticity, especially for a metal. So with Be or Al, its important to not go beyond the designed capability. Its important to do so with any driver, but the resulting output distortion will be higher. The designed capability will be very driver specific as the shape, size, thickness, quality of process will dramatically affect these figures. FEA applications will be primary point in the design process for modern drivers.

When Be is being formed, the dust that can be inhaled that can be hazardous. When formed in shape, its pretty stable and even when broken isn't quite as hazardous as it would be in a manufacture facility with volumes and processes being applied. It still needs to be handled appropriately in those situations.  

I run TADs and BE does have advantages its lighter stiffer has high resonate frequency before material breakup. But its highly toxic sure as a user you most likely will not BE exposing yourself family or pets to BE poisoning but maybe the place were its mined did or maybe the miner maybe the factory worker maybe anyone handling it in the future. So to me if you want BE buy vintage dont support modern production of BE drivers in things as disposable as a modern loudspeaker.