Based on my experience in aerospace manufacturing, I would be surprised if the cost of a beryllium diaphragm was less than 10x the cost of an aluminum diaphragm. I would not be shocked if the true price difference was much more. If we compare the retail price of a popular beryllium dome tweeter (Satori TW29BN-B) to the same tweeter with a silk dome (TW29DN-B)... same motor, same frame, the only real difference is the diaphragm... The Be version is $405, the silk dome is $155.
The judgment as to whether this is an astronomical cost or a reasonable cost is dependent on the project, and the expectations of the persons designing, building, and using the speaker. It is a personal decision.
j.
The judgment as to whether this is an astronomical cost or a reasonable cost is dependent on the project, and the expectations of the persons designing, building, and using the speaker. It is a personal decision.
j.
$250 extra just for a Be dome...
The F14 'Tomcat' jet had some complex Titanium honeycombs, those were tough to machine. Expensive, beyond doubt, and essential.
I think the decision maker must make an informed choice before spending $810 on a pair of tweeters, when a pair of Al tweeters will cost $76 on Amazon, or a similar site (Amazon says $37.99 for a single 1.5" bullet)...
No, I do not think they are essential to my enjoyment of music.
The F14 'Tomcat' jet had some complex Titanium honeycombs, those were tough to machine. Expensive, beyond doubt, and essential.
I think the decision maker must make an informed choice before spending $810 on a pair of tweeters, when a pair of Al tweeters will cost $76 on Amazon, or a similar site (Amazon says $37.99 for a single 1.5" bullet)...
No, I do not think they are essential to my enjoyment of music.
The manufacturers obviously think there is a market for these. Otherwise they would not have spent the time and money to produce them. Does their MSRP somehow invalidate that they exist and hold a particular niche in the market?
I mean, I'm just taking a stab at it, I'm not actually sure what your point is, other than that you personally don't think they're worth the extra money. It is trivial to find the price of drivers that use Be diaphragms.
At the last Rocky Mountain Audio Fest, the project manager from Materion had an unusual demo: three otherwise identical tuning forks, one made from aluminum, one made from titanium, and one from beryllium. The color was slightly different, but the sound from each tuning fork was remarkably different, despite the similarity in appearance.
The longest resonance was from titanium, which also sounded brightest and harshest, while aluminum sounded calmer and rang down a little quicker than titanium. The beryllium tuning fork was a surprise: it was so light it practically floated out of your hand, and it rang down very quickly ... I'd say less than half the time of the other two, and it did not have any harsh overtones ... at all.
The self-damping was obvious. It was almost as if the tuning fork was coated in rubber, except the original strike was as crisp and clear as the other two. So a quick and very fast PING followed by a quick decay, with few harmonics audible. By contrast, the titanium had audible hash following the initial ping, with much less hash from aluminum, with a similar ring-down time.
My curiosity is whether nitriding significantly changes the properties of titanium.
The longest resonance was from titanium, which also sounded brightest and harshest, while aluminum sounded calmer and rang down a little quicker than titanium. The beryllium tuning fork was a surprise: it was so light it practically floated out of your hand, and it rang down very quickly ... I'd say less than half the time of the other two, and it did not have any harsh overtones ... at all.
The self-damping was obvious. It was almost as if the tuning fork was coated in rubber, except the original strike was as crisp and clear as the other two. So a quick and very fast PING followed by a quick decay, with few harmonics audible. By contrast, the titanium had audible hash following the initial ping, with much less hash from aluminum, with a similar ring-down time.
My curiosity is whether nitriding significantly changes the properties of titanium.
Last edited:
Nitriding of steel takes a week, the temperature is built up to nearly 500 C and then the closed chamber is filed with ammonia.
That is kept as is for about 4 days, and then the chamber is purged, and the temperature ramped down.
A pit furnace, with the job held vertically to reduce distortion, is normal.
This is a common process for the screws and barrels used in plastic processing, and engine crankshafts, among other things.
In Iron, the structure becomes Martensitic, from Austenitic, the temperatures are close.
So an element of heat treatment and stress relief is also achieved.
Titanium has a much higher melting point, so I have little idea if the structure will be affected, the skin on the SR-71 plane used to get red hot at times....Or even if it is practical.
There is another process called 'Sursulf' or 'Liquid Nitriding', the hardness and depth achieved are much less than what is got during gas nitriding. It is claimed to get skin hardnes on more materials than nitriding steels, which contain traces of Aluminum...the skin is actually Aluminum Nitride.
Also, Titanium needs inert gas atmospheres, so that is also a practical point. It is melted under Argon, air makes it burn.
I have no idea if it will react with Nitrogen containing gas, or whether it can actually be nitrided.
There are processes using physical vapor deposition under vacuum, for making tools wear less, among other intended results, those may work for Titanium.
That is kept as is for about 4 days, and then the chamber is purged, and the temperature ramped down.
A pit furnace, with the job held vertically to reduce distortion, is normal.
This is a common process for the screws and barrels used in plastic processing, and engine crankshafts, among other things.
In Iron, the structure becomes Martensitic, from Austenitic, the temperatures are close.
So an element of heat treatment and stress relief is also achieved.
Titanium has a much higher melting point, so I have little idea if the structure will be affected, the skin on the SR-71 plane used to get red hot at times....Or even if it is practical.
There is another process called 'Sursulf' or 'Liquid Nitriding', the hardness and depth achieved are much less than what is got during gas nitriding. It is claimed to get skin hardnes on more materials than nitriding steels, which contain traces of Aluminum...the skin is actually Aluminum Nitride.
Also, Titanium needs inert gas atmospheres, so that is also a practical point. It is melted under Argon, air makes it burn.
I have no idea if it will react with Nitrogen containing gas, or whether it can actually be nitrided.
There are processes using physical vapor deposition under vacuum, for making tools wear less, among other intended results, those may work for Titanium.
Last edited:
Some people are OCD about exotic and expensive stuff.
You should see the discussions on fountain pen forums about inks and nibs!
Some things like F-14 parts are essential for their use, with light weight and strength under harsh conditions being important.
Nitrided Titanium tweeter vs. regular Titanium tweeter, or the ringing of tuning forks...not so important in my opinion..
You should see the discussions on fountain pen forums about inks and nibs!
Some things like F-14 parts are essential for their use, with light weight and strength under harsh conditions being important.
Nitrided Titanium tweeter vs. regular Titanium tweeter, or the ringing of tuning forks...not so important in my opinion..
https://www.youtube.com/live/x9NAVlwvLro?feature=share
Pertinent convo starts at around 54min.
18 Sound nitride was the clear winner over Radian aluminum when I closely compared both of them. 745Neo vs ND3SN.
Hard to say how much the diaphragm material played in the outcome.
Last edited:
I think that much too seldom the structure is used to reinforce the material.
JBL used origami embossed titanium for their tweeters making stiffness much better.
Some car Hifi diaphragms for woofers use structures making a cone much stiffer.
Ribbed cone helps to lessen radial break up.
Fostex did it for the fe208 sigma driver
But also sandwich materials can help but rarely are used.
D a Barlow on sandwich cones
https://www.diyaudio.com/community/threads/full-range-pics.87174/post-6711011
https://www.diyaudio.com/community/threads/acoustic-research-ar-7.156828/post-7177618
AR speaker with JBL like diaphragm for tweeters
https://www.diyaudio.com/community/threads/acoustic-research-ar-7.156828/post-7177619
JBL used origami embossed titanium for their tweeters making stiffness much better.
Some car Hifi diaphragms for woofers use structures making a cone much stiffer.
Ribbed cone helps to lessen radial break up.
Fostex did it for the fe208 sigma driver
But also sandwich materials can help but rarely are used.
D a Barlow on sandwich cones
https://www.diyaudio.com/community/threads/full-range-pics.87174/post-6711011
https://www.diyaudio.com/community/threads/acoustic-research-ar-7.156828/post-7177618
AR speaker with JBL like diaphragm for tweeters
https://www.diyaudio.com/community/threads/acoustic-research-ar-7.156828/post-7177619
Attachments
Last edited:
Thanks for the video! Great to hear the designers at B&C and 18Sound talk about what their customers want. To my surprise, some, maybe even most, want that breakup sizzle in the 10-20 kHz top octave ... a sizzle so loud it can be heard 10 to 30 meters away from the PA speaker! In some new models, B&C even replicated that breakup sizzle because customers demanded it. And by contrast, 18Sound has tried to design away from it. Also surprising that beryllium is so different in the time domain, although regrettably many times more expensive.
It's only the one B&C model ASFIK that they have added sizzle in. Not my kind of thing but its also worth noting that compresion drivers sound different at close to maximum output than home use levels, polymers soften tending to reduce the top end and motor force decreases, a full Ti diphragm helps mitigate this. The resonance also boosts efficiency, this technique is used to good effect to bring up the top end of BMS small format comps: https://www.bmsspeakers.com/fileadmin/bms-data/product_data_2019/bms_5530_datasheet.pdf
although I doubt in that case the cause of the resonance is breakup of the diaphragm as its a small anular ring and of a single frequency and lower Q.
although I doubt in that case the cause of the resonance is breakup of the diaphragm as its a small anular ring and of a single frequency and lower Q.
Buy some elemental beryllium and find out.
These beryllium diaphragms shown are either PVD deposited onto another metal, such as aluminum or titanium.
My point is that "elemental" (pure) beryllium isn't made into these speaker drivers. It's an alloy or PVD process.
The topic was regarding if Be containing speaker drivers SOUND better, not really how they are made, if you can make them in your home shop.
I have compression drivers that have Be and can't hear any difference in the sound. Congratulations to all that have bought beryllium containing diaphragms and can actually hear a difference. Rather than spend my time on a DIY audio forum discussing physics, manufacturing processes, I prefer to read these forums to learn about audio. Cheers!
The melting temperature of iron (steel) is 1540C and titanium melts at 1670C. Less than 10% difference.
To take a stab at addressing the original question, annealing an aluminum diaphram is probably a pretty good idea. When you take a sheet of aluminum and press it into a dome, you're going to get some surface stress that the annealing will relieve. This should drop the coefficient of restitution, or how elastic it's impulse response is (CoR=1 is perfectly elastic, CoR=0 is perfectly plastic, or a low CoR is a very damp material). A high surface stress sheet like 7075-T6 is going to be up around 0.75, while the same alloy un-tempered is about 0.35.
Please see this, from a Google search: https://thermalprocessing.com/gas-nitriding-of-titanium/
It seems that Titanium is difficult to process, preferring to bond with Oxygen rather than Nitrogen, even in a controlled atmosphere vacuum furnace.
You can read the above articles, and similar ones to satisfy your curiosity.
As above, simply use a stiffer Aluminum alloy, and that is the driver maker's decision.
Most of us do not have the ability or facility to make them, let alone process a toxic material like Beryllium...
It seems that Titanium is difficult to process, preferring to bond with Oxygen rather than Nitrogen, even in a controlled atmosphere vacuum furnace.
You can read the above articles, and similar ones to satisfy your curiosity.
As above, simply use a stiffer Aluminum alloy, and that is the driver maker's decision.
Most of us do not have the ability or facility to make them, let alone process a toxic material like Beryllium...
I don't think Ti domes would be much harder or more expensive to make than Al ones. I have no clue how they get made in volume, but an open back hydroform should probably work for both metals. The labor/energy cost to anneal Al is probably more than the material cost diffference.
One of the big upsides to Ti is that it has much better cyclic loading fatigue properties compared to Al.
One of the big upsides to Ti is that it has much better cyclic loading fatigue properties compared to Al.
The problem seems to be in rolling Titanium to the thin sheets need to stamp it out, and the stamping tools need to be carbide, that is a big cost per unit.
Not really my area of expertise, in my city, we have many units making orthopedic implants in Titanium and stainless steel, up to knee and hip joints. They usually use bars and plates as raw material, not the thin sections needed for tweeters.
Not really my area of expertise, in my city, we have many units making orthopedic implants in Titanium and stainless steel, up to knee and hip joints. They usually use bars and plates as raw material, not the thin sections needed for tweeters.
All industrial use of metals, be it steel, titanium, aluminum, magnesium or beryllium is in the form of alloys. Even the gold ring around your finger is alloy. Metals are kind of useless in their pure state.