Midrange dome drivers banned ?

[Newman]

I think driver material choice is overrated. Audiophiles have a bit of a weakness in this regard.

 

[JWAmerica]

I think driver material choice is overrated. Audiophiles have a bit of a weakness in this regard.

For sure, technically inferior materials can be engineered to perform at SOTA levels if you're willing to pay for it. Peerless makes some highly regarded corundum tweeters though that have been compared to beryllium tweeters. Flat response across a wide frequency range with low distortion.

 

[gene_stl]

I am working on a center channel speaker and I was successful in finding some Yamaha Be drivers. If I had not been successful or they were too much money , I would have used those Corundum drivers. Or possibly ceramic. The manufacturer's specs look good and they don't cost the world. Both stable stiff materials.

Most of the non Yamaha Be Tweeters are $350 to $650 each. That is insanity.

Why would anyone think that the driver dome material is unimportant? That is an absurdly silly statement, imo.

 

[thewas]

Why would anyone think that the driver dome material is unimportant? That is an absurdly silly statement, imo.

It is important in terms of engineering properties, but on the other hand even a well engineered affordable modern aluminium dome like the Seas DXT (less then $100!) which is used for example on real reference loudspeakers like the Kii Three and Grimm LS1 can provide sufficiently good properties to be transparent (see also https://www.audiosciencereview.com/...rbeth-30-2-vs-kef-r3.14450/page-2#post-445233 ) so the quest for the exotic unobtainium material is more marketing and hype nowadays then anything else. In the 1970s the modelling, simulation and engineering of the drivers wasn't as far though, so the Yamaha Be drivers were truly a step forward though.

 

[dshreter]

Why would anybody be stupid enough to think the sound source should be coincident with the listener?

I’m not sure, but it sure is very difficult to clap your hands in one location and listen to the echo in a different location without a microphone.

 

[Frank Dernie]

I’m not sure, but it sure is very difficult to clap your hands in one location and listen to the echo in a different location without a microphone.

It isn't what is easy that counts though. Doing something completely inappropriate because it is easier than doing it right is stupid and pointless. Just IMO of course.

 

[gene_stl]

A wag that I used to know quipped, "If something isn't worth doing , it isn't worth doing well."

Modeling and simulation are just that.

 

[Newman]

Modelling and simulation tools are probably the biggest reasons loudspeaker technology has advanced to where it is today.

 

[thewas]

Modelling and simulation tools are probably the biggest reasons loudspeaker technology has advanced to where it is today.

...and most other technologies and sciences.

 

[Frank Dernie]

Modelling and simulation tools are probably the biggest reasons loudspeaker technology has advanced to where it is today.

Particularly in making cheap units have very good performance.

 

[Newman]

That must be why all the high-end loudspeaker manufacturers use it so extensively, unless they are a tiny cottage outfit.

 

[witwald]

Properly designed the cone will act as a piston. If it does resonate, like paper and plastic do, damping will be applied to reduce the colouration.

Even if properly designed, a metal cone/dome will behave like a piston only up to its first structural resonance frequency. There isn't much inherent material damping in metals, so any resonances are going to have a very high Q. This is clearly apparent in the audio passband when bass-midrange drivers make use of metal cones (and usually a bit above 20 kHz for tweeters). Even though the crossover may heavily attenuate those resonances, is it wise to have them present in the first place as a result of a poor choice of material, when better approaches are available?

It is important to understand that, in a speaker, you are not listening to somebody using the cones as percussion instruments but, ideally, the cone does not breakup in its passband so that any characteristic sound the material would have won't be part of the sound coming from the speaker.

What is meant by the characteristic sound of the cone material when it is breaking up? Doesn't a cone material simply possess properties of density, stiffness and loss factor (damping)? Aren't those the fundamental material characteristics that are needed to be identified when engineering a new cone design? How do any of these engineering properties translate to a "characteristic sound" if the frequency response of the driver is ostensibly flat? Isn't the audio performance simply a result of the structural resonances, damping and piston-range behaviour of the cone, and not the "material" per se?

Why would anyone think that the driver dome material is unimportant? That is an absurdly silly statement, imo.

The following might provide some guidance. In terms of audibility of different materials, back in 2010, Rotter and Lindau published a paper titled "Audibility of tweeter performance beyond spectrum and phase" (PDF). They concluded that (emphasis added):

"When eliminating frequency and phase response irregularities, baffle and room interaction, non-linear behavior, and distance effects, a blind-comparison listening test could not reveal audible differences between different types of tweeters. Neither the material nor the actuator principle, neither the tweeters geometry nor the specific form of wave fronts in the far field could be shown to be distinctive features of different tweeter types. Divergent results of previous studies can only be explained by aforementioned shortcomings of the test designs. Furthermore, when excluding room and baffle interaction, FIR equalization seems to be capable to compensate for the behavior of different loudspeakers at the sweet spot within a typical range of horizontal head movements."

 

[KSTR]

Even if properly designed, a metal cone/dome will behave like a piston only up to its first structural resonance frequency. There isn't much inherent material damping in metals, so any resonances are going to have a very high Q. This is clearly apparent in the audio passband when bass-midrange drivers make use of metal cones (and usually a bit above 20 kHz for tweeters). Even though the crossover may heavily attenuate those resonances, is it wise to have them present in the first place as a result of a poor choice of material, when better approaches are available?

What is meant by the characteristic sound of the cone material when it is breaking up? Doesn't a cone material simply possess properties of density, stiffness and loss factor (damping)? Aren't those the fundamental material characteristics that are needed to be identified when engineering a new cone design? How do any of these engineering properties translate to a "characteristic sound" if the frequency response of the driver is ostensibly flat? Isn't the audio performance simply a result of the structural resonances, damping and piston-range behaviour of the cone, and not the "material" per se?

The following might provide some guidance. In terms of audibility of different materials, back in 2010, Rotter and Lindau published a paper titled "Audibility of tweeter performance beyond spectrum and phase" (PDF). They concluded that (emphasis added):

"When eliminating frequency and phase response irregularities, baffle and room interaction, non-linear behavior, and distance effects, a blind-comparison listening test could not reveal audible differences between different types of tweeters. Neither the material nor the actuator principle, neither the tweeters geometry nor the specific form of wave fronts in the far field could be shown to be distinctive features of different tweeter types. Divergent results of previous studies can only be explained by aforementioned shortcomings of the test designs. Furthermore, when excluding room and baffle interaction, FIR equalization seems to be capable to compensate for the behavior of different loudspeakers at the sweet spot within a typical range of horizontal head movements."

That was a somewhat flawed study in my view. They did NOT test for actual audible differences. They offered linear (free of distortion) emulations (auralizations via headphones) of tweeters EQ'd to the same target. That last part is OK and actually required (since we don't want to judge frequency response as such), but using only a linear copy of the signal and the "indirect" comparison via head-tracking headphone playback is questionable. It just made the experiment much easier to conduct.

 

[Frank Dernie]

Even if properly designed, a metal cone/dome will behave like a piston only up to its first structural resonance frequency.

Correct, and correct in the case of all materials one may choose to use for a cone or dome.

There isn't much inherent material damping in metals, so any resonances are going to have a very high Q.

Correct, and how it is notched out is important for a mid or bass unit, possibly not for a tweeter.

Even though the crossover may heavily attenuate those resonances, is it wise to have them present in the first place as a result of a poor choice of material, when better approaches are available?

The current approach is to use a material which is breaking up and damp it a bit. Is this a better approach?

What is meant by the characteristic sound of the cone material when it is breaking up?

I didn't explain this well.
If you strike the cone with a drumstick, for example, it is a broadband excitation and the sound heard will be almost entirely the breakup and its timbre is that due to the various overtones and their Q. This will vary between materials in the way bells and cymbals do.

When driven by a voicecoil there is the possibility, if the cone is stiff enough, to only excite it below its first mode and it will then be acting as a piston and there is no mechanism by which there will be a different characteristic sound between different materials.
That was the point I was trying to make, the material of a driver being driven in the pistonic frequency range has no mechanism by which it can alter the sound by material characteristic alone.

It is true that very few speaker drivers are made which remain pistonic through their passband and the engineering required to get the best out of those that do is at a higher level than conventional speakers.

The various plastic and paper drivers which do not remain pistonic may well have a characteristic sound caused by the non-flat frequency response inevitable from the various breakup modes, however well damped they are.
OTOH we have been "getting away with" imperfect cone materials for over 100 years.

 

[headshake]

New Bliesma mid dome specs!

Now I just need to see the distortion and decay.

 

[dfuller]

New Bliesma mid dome specs!

Now I just need to see the distortion and decay.

The silk dome one looks to have the best overall performance as a midrange. Really pretty impressive.

 

[headshake]

The silk dome one looks to have the best overall performance as a midrange. Really pretty impressive.

The paper dome is the one I have an eye on-lowest fs and least power drop off-axis around 4khz. Whichever one has the best decay will get my bucks. I am interested in 500hz-4000hz and a 1ms to drop -30db... this is my wish list anyways.

 

[dfuller]

The paper dome is the one I have an eye on-lowest fs and least power drop off-axis around 4khz. Whichever one has the best decay will get my bucks. I am interested in 500hz-4000hz and a 1ms to drop -30db... this is my wish list anyways.

Reason I think the silk looks best is its complete lack of severe breakup. Even the paper is worse. The Beryllium is very good too.

 

[witwald]

Now I just need to see the distortion and decay.

The Cumulative Spectral Decay (CSD) curves will no doubt be as expected for a bandpass driver with some very lightly-damped high-frequency resonances present. It's a pity that the designs still include these.

As for distortion, the magnet motor utilizes an underhung voice-coil, as was and continues to be used in many ATC loudspeaker drivers. This design feature will be helpful, as it should help to minimise distortion arising from the magnet motor, and the rest will be up to the linearity of the suspension. It could reasonably be expected that these drivers will all have low distortion.

However, it's disappointing and a bit of an oversight that the datasheets are silent on this distortion issue. They omit providing some very useful data for loudspeaker system designers to look at. That sort of information probably might have been standard back in the 1970s. So why not now?

It is also quite odd that there is the claim that "Extremely low moving mass for better transient response", as the transient response of a linear driver (which I hope these are!) is entirely defined by its frequency response function. A driver with a lower moving mass (lighter diaphragm) does NOT have a better transient response than a driver with a greater moving mass with the same shape of frequency response function. Of course, the driver with the larger moving mass will have a lower sensitivity. I think that loudspeaker designers such as Thiele, Small, Benson, etc., worked that out a long, long time ago.

 

[bigjacko]

Saying some marketing stuff around transient is common practise for manufacturers now..... No one wants to try to be the first to go full blown science and engineering based marketing because objective people does not hate subjective marketing but subjective people hate objective marketing.

Personally I would choose the silk if I am going passive crossover as there is no break up to worry about. The paper and aluminium ones have break up that simple 2nd order crossover is not enough. Berylium will always not get my pick because it is not worth it. Paper has wider directivity so has some merit too. I think the directivity for those mid domes are not that wide compare to 4 inch woofers, but these domes don't need seperate chamber so a very big plus.