(07-Jun-2016, 13:53)f1eng Wrote: I am bemused by the suggestion of a Ti tweeter. With few exceptions (Be, B) most engineering metals have more or less the same specific stiffness, that is to say ratio of density:modulus.
Titanium is quite a bit heavier than aluminium, so a titanium dome of the same weight as the existing aluminium dome will have to be thinner. Since the bending stiffness is proportional to thickness cubed that means a Ti dome will break up at a lower frequency than an Al one. On top of that anodising Al leaves a hard coating which may well increase its stiffness still further (I haven't checked the modulus of the aluminium oxide anodised layer).

So whilst this may be a better tweeter than the current one it won't be because it is Titanium.

As far as metals go only Beryllium has much better properties for tweeter domes than others, Magnesium may have a touch higher breakup frequency than aluminium, which will be slightly higher again Titanium if each are the same weight, since the less dense materials will be a tiny bit thicker.

(08-Jun-2016, 11:47)f1eng Wrote: Beryllium is very difficult, expensive and dangerous to manufacture.
I have a pair of Yamaha NS1000M which have Beryllium tweeter and mid range domes which they say would be impossible to make economically today.
Scanspeak Beryllium tweeters are >£500 each retail, so would probably add around £1250 to each Phantom (using the 2x retail markup and 5x BOM cost formula).
This may well be better but move them into a different price bracket.

Paper is a very good material for Bass drivers. It is a bit limited for mid range drivers, with breakup modes likely towards the upper crossover area. Damping can mitigate this but there is still distortion. Scanspeak, and maybe others, cut slots in the paper cone of some models and re-glue with a damping compound. This works well, and is used in some high end speakers, but is pretty expensive too.

Overall for lower frequency drivers many materials cleverly implemented work well. Tweeters are more difficult since most will have breakup in their passband and need to be damped to prevent audible peaks. Metal dome tweeters have their resonance at inaudibly high frequencies and are rarely damped.
Some people don't like them!
I have 4 largish speakers at home. Two pairs have damped fabric domes, one a titanium compression driver, one a Beryllium dome!

Then there are the tiny Phantoms which work amazingly well IMHO.

(08-Jun-2016, 13:08)Zappydev Wrote:

(08-Jun-2016, 11:47)f1eng Wrote: Beryllium is very difficult, expensive and dangerous to manufacture.
I have a pair of Yamaha NS1000M which have Beryllium tweeter and mid range domes which they say would be impossible to make economically today.
Scanspeak Beryllium tweeters are >£500 each retail, so would probably add around £1250 to each Phantom (using the 2x retail markup and 5x BOM cost formula).
This may well be better but move them into a different price bracket.

Paper is a very good material for Bass drivers. It is a bit limited for mid range drivers, with breakup modes likely towards the upper crossover area. Damping can mitigate this but there is still distortion. Scanspeak, and maybe others, cut slots in the paper cone of some models and re-glue with a damping compound. This works well, and is used in some high end speakers, but is pretty expensive too.

Overall for lower frequency drivers many materials cleverly implemented work well. Tweeters are more difficult since most will have breakup in their passband and need to be damped to prevent audible peaks. Metal dome tweeters have their resonance at inaudibly high frequencies and are rarely damped.
Some people don't like them!
I have 4 largish speakers at home. Two pairs have damped fabric domes, one a titanium compression driver, one a Beryllium dome!

Then there are the tiny Phantoms which work amazingly well IMHO.

Very informative - thank you. 

Have you ever used the NS1000 with your Devialet?

(07-Jun-2016, 06:55)MountainGuy Wrote: Any other changes except for power and titanium tweeters?  Improvement on the midrange ring?

(08-Jun-2016, 03:59)MountainGuy Wrote:

(07-Jun-2016, 13:53)f1eng Wrote: I am bemused by the suggestion of a Ti tweeter. With few exceptions (Be, B) most engineering metals have more or less the same specific stiffness, that is to say ratio of density:modulus.
Titanium is quite a bit heavier than aluminium, so a titanium dome of the same weight as the existing aluminium dome will have to be thinner. Since the bending stiffness is proportional to thickness cubed that means a Ti dome will break up at a lower frequency than an Al one. On top of that anodising Al leaves a hard coating which may well increase its stiffness still further (I haven't checked the modulus of the aluminium oxide anodised layer).

So whilst this may be a better tweeter than the current one it won't be because it is Titanium.

As far as metals go only Beryllium has much better properties for tweeter domes than others, Magnesium may have a touch higher breakup frequency than aluminium, which will be slightly higher again Titanium if each are the same weight, since the less dense materials will be a tiny bit thicker.

f1eng,

Very helpful comments.  That would explain why there are so few titanium tweeters.  In that case, perhaps they are considering Beryllium.  I was interviewed a while ago by someone at Devialet and had suggested Beryllium. 

As to 4500 watts, my thought is that it may offer more control over the cones than increasing decibels.  More resolution.   

Also, paper woofers can sound fantastic. I currently have a speaker with small paper woofers which have a moving mass of just 1.9 grams and they are incredibly fast and resolved.  Just wonderful drivers.