Head-Fi.org › Forums › Summit-Fi (High-End Audio) › High-end Audio Forum › The Stax Thread III
New Posts  All Forums:Forum Nav:

The Stax Thread III - Page 132

post #1966 of 2814
Thanks guys.
I'll call Fujiya and see how it goes.
Any other stores I should check?

I'm sure reserving and maybe paying for that over the phone will be quite challenging, considering I don't speak Japanese...
post #1967 of 2814

You're not gonna have much luck if you can't speak Japanese and if you're not local. These places are for local Japanese customers only. You could try Price Japan but be warned about warranty, etc. (go back a few pages or search for "warranty" on this thread and you may get a few hits).

post #1968 of 2814
I thought so...
I'll see if a good friend can do something about it. I'm staying in Tokyo for 3 weeks, so I'll search for it on the very first days and reserve in case I don't find any.

Thanks again for your inputs!
post #1969 of 2814
Quote:
Originally Posted by milosz View Post

With a HEADPHONE AMP designed to drive electrostatic headphones I doubt you'd see much variance of output vs. frequency.  Headphones of all types - including electrostatic- don't have anywhere near the impedance excursions that speakers exhibit.  So "tube sound" in an electrostatic headphone amplifier is more likely a result of harmonic distortion "flavor" than of frequency response variance.  All amplifiers distort, and tube amps tend to have a lower amount of high-order harmonics in their distortion products than solid state amps, many people attribute the 

tube sound" in part to this fact.

 

By the way, using a given set of speakers with a given tube amp can end up with less than great sound, for reasons noted above. The resulting frequency response might be pretty funky, matching speaker to amp can be hit-or-miss.  But I also heard a pairing which made the speakers sound GREAT>  unexpectedly so. Kind of a roundabout way to add an EQ curve to your playback chain, but the frequency-response artifact introduced by some tube amps can compliment certain speakers.  I put a pair of little Polk RT25i on a budget Audioromy FU29 tube amp and I could not believe how great it sounded.  The Audioromy FU-29 is a pretty decent low-cost amp, about 25 class-A watts per channel, and the RT25i's  are known to be great little budget  speakers but the combination really sounded so much better than I expected that I had to have some musician friends come over to make sure I wasn't imagining things or having a flashback to the 1960's.  They also agreed that the sound was pretty wonderful on the RT25i's with the tube amp, except the bass - already pretty light from the Polk's 5-inch woofers - was really kind of "mellowed out" with the tube amp, and not very "tight."  It didn't sound wooly or flabby, just lacked much punch below 60 Hz and had a little extra warmth around 200 Hz.  Still the mids and treble were just wonderful.  So, "tube magic" isn't about how inherently GOOD a tube amp is, it's more about how nicely it can WORK with the right speakers. 

Of course, I was responding directly to the allegation that transistor amplifiers were subject to greater flaws than valve designs. That is not the case.

 

I don't believe in the approach within your last paragraph because it subjects your signal to the element of randomness when a linear and transparent alternative solution (before the transducers) might be readily available.


Edited by 3X0 - 4/6/14 at 12:11pm
post #1970 of 2814
Quote:
Originally Posted by milosz View Post
 

 

Those wide deviations from flat frequency response of tube amps come from interactions of their output transformer / output stage / amount of negative feedback employed with the impedance variations in speakers.   These particular curves look like the kind of "simulated 3-way speaker load" curves that Stereophile runs.  Depending on the design, one tube amp will have greater or lesser "sensitivty" to speaker impedance than others.  It mostly comes down to Ohms-law kind of interaction between the source impedance of the tube amp and the impedance curve of the speaker.  Speakers have crossovers,  lots of drivers and so on, their impedance-vs-frequency curves can be pretty hairy.  And remember impedance is a vector quantity, not scalar....

 

(...)

 

We may have better transducers in the long run to ease the load of the amplifier. Maybe we would not need even stators, reducing reflections. Have a look at this research on a thermoacoustic transducer:

 

Quote:
Flexible, Stretchable, Transparent Carbon Nanotube Thin Film Loudspeakers
 
Most of the loudspeakers used today consist at least of a cone, a voice coil attached to the apex of the cone, a permanent magnet fixed to the loudspeaker’s frame, and an enclosure. By applying an audio current waveform to the nanotube (CNT) thin film could be a practical magnet-free loudspeaker simply by applying an audio frequency current through it. This CNT thin film loudspeaker can generate sound with wide frequency range, high sound pressure level (SPL), and low total harmonic distortion (THD). The nanothickness CNT thin films we used are flexible, stretchable, and transparent and can be tailored into many shapes and sizes, freestanding or placed on a variety of rigid or flexible insulating surfaces. Furthermore, the CNT thin film loudspeaker has a very simple structure, without magnets and moving parts. Such a single-element thin film loudspeaker might open up new applications of and approaches to manufacturing loudspeakers and other acoustic devices.
 
(...) The ac impedance of a CNT thin film is pure resistance and shows no frequency dependence within 1 MHz.
 
(...)
 

Edited by jgazal - 4/6/14 at 12:16pm
post #1971 of 2814

Thermoacoustic speakers aren't high fidelity. However, electrostatically driven graphene has already demonstrated excellent acoustic performance. Methods to low cost / high quality graphene is an enormous topic, but the material is readily applicable to Stax, and proposes to improve their products.

 

On the other hand, the availability of $1000 voice coil headphones suggests a general disinterest in science on behalf of users, right?


Edited by dripf - 4/6/14 at 1:28pm
post #1972 of 2814
Quote:
Originally Posted by dripf View Post
 

Thermoacoustic speakers aren't high fidelity. However, electrostatically driven graphene has already demonstrated excellent acoustic performance. Methods to low cost / high quality graphene is an enormous topic, but the material is readily applicable to Stax, and proposes to improve their products.

 

Would you please point me thermo acoustic speakers available for purchase?

 

I see the electrostatically graphene you mentioned: http://www.physics.berkeley.edu/research/zettl/projects/graphene_loudspeaker/speaker.html. Which is the thickness of that graphene diaphragm? Is it a single layer graphene or it has a substrate? If it is not a single layer graphene, how graphene in a substrate would differ in quality from mylar?

 

Would you point me where to buy similar single layer graphene or a graphene in a substrate sheets to made larger diameter diaphragms (i.e. a diaphragm for the SR-003 or SR-009)?

 

I think consumers were not concerned about teflon or lithium until they realized their utility.


Edited by jgazal - 4/6/14 at 1:50pm
post #1973 of 2814

You can get graphene sheets here, although they seem to be a minimum of 25um thick, which is far too thick for an electrostatic driver. Also, graphene is conductive which seems to me to make it a fairly bad electrostatic diaphragm material. The demos on electrostatic graphene drivers thus far has been extremely small sized drivers, nothing like stax headphones.

 

https://graphene-supermarket.com/Graphene-Coatings/

post #1974 of 2814

It would be very cool if some of the DIYers would experiment with graphene for their 'stats. Don't know if it is viable to do so in the first place.

 

EDIT: I suppose the thread above answers that.. Maybe in the future.

post #1975 of 2814
Quote:
Originally Posted by jgazal View Post
 

 

Would you please point me thermo acoustic speakers available for purchase?

 

I see the electrostatically graphene you mentioned: http://www.physics.berkeley.edu/research/zettl/projects/graphene_loudspeaker/speaker.html. Which is the thickness of that graphene diaphragm? Is it a single layer graphene or it has a substrate? If it is not a single layer graphene, how graphene in a substrate would differ in quality from mylar?

 

Would you point me where to buy similar single layer graphene or a graphene in a substrate sheets to made larger diameter diaphragms (i.e. a diaphragm for the SR-003 or SR-009)?

 

I think consumers were not concerned about teflon or lithium until they realized their utility.


Thermoacoustic speakers are inefficient at audible frequencies and exhibit a response slope that is unsuitable.

 

The thickness of the diaphragm demonstrated in that paper was determined to be about 30 nm via measured light transmittance. The graphene film would represent a perfect diaphragm transducer.


Edited by dripf - 4/6/14 at 2:21pm
post #1976 of 2814
Quote:
Originally Posted by dripf View Post
 


Thermoacoustic speakers are inefficient at audible frequencies and exhibit a response slope that is unsuitable.

 

The thickness of the diaphragm demonstrated in that paper was determined to be about 30 nm via measured light transmittance. The graphene film would represent a perfect diaphragm transducer.

 

Assuming one could purchase graphene that thin, which it appears one cannot, wouldn't it still be nearly as conductive as metal? An electrostatic diaphragm should not be anywhere close to that conductive.

post #1977 of 2814

The diaphragms are insulated.

post #1978 of 2814
Quote:
Originally Posted by dripf View Post
 


Thermoacoustic speakers are inefficient at audible frequencies and exhibit a response slope that is unsuitable.

 

Can carbon nanotubes film transducers also be classified as inefficient at audible frequencies? I think that article also covers such slope:

 

Quote:
(...)
 
Despite the excellent acoustic performance of the CNT loudspeaker, it has a drawback. As shown in Figure 2d, the output frequency doubles that of the input. The human voice and music sound strange when a commercial bipolar audio amplifier is used to drive the CNT thin film loudspeaker. A simple solution is to add a direct current bias Io to the alternating current for driving such CNT loudspeakers. To achieve this, we use a very simple single transistor amplifier to drive our CNT loudspeaker, which can reproduce the input sound wave signals faithfully. The schematic circuit is shown in Figure S2 of the Supporting Information. Note that the impedance of the CNT loudspeaker is pure resistance (see Supporting Information, Figure S1), and the design of the amplification circuit is much simpler than that for inductive voice-coil loudspeakers. (...)
 

 

Indeed an interesting topic.

post #1979 of 2814
Quote:
Originally Posted by dripf View Post
 

The diaphragms are insulated.

So what's the total thickness (really weight) of the moving diaphragm?

 

I've always thought that graphene should eventually be used for the stators, not the diaphragm.

 

Traits important for the diaphragm:

- lightweight

- high resistance (low conductance)

- very pliable

- long term dimensional stability

- able to flex continuously without break/fracture

 

Traits important to stators:

- high conductivity

- as rigid as possible

- related, high rigidity allows for thinner stators which allows for smaller and more numerous holes which allows for more evenly distributed charge on the surface (no "hotspots")

 

Graphene has conductivity and rigidity that are off the charts.  I'm hoping that one day it will be possible to consistently make the graphene sheets thick enough so that they can be used as ultra strong stators.  There will also need to be a way to shape the graphene sheets (to insert the stator holes, etc). 

post #1980 of 2814
Quote:
Originally Posted by n3rdling View Post
 

So what's the total thickness (really weight) of the moving diaphragm?

 

I've always thought that graphene should eventually be used for the stators, not the diaphragm.

 

Traits important for the diaphragm:

- lightweight

- high resistance (low conductance)

- very pliable

- long term dimensional stability

- able to flex continuously without break/fracture

 

Traits important to stators:

- high conductivity

- as rigid as possible

- related, high rigidity allows for thinner stators which allows for smaller and more numerous holes which allows for more evenly distributed charge on the surface (no "hotspots")

 

Graphene has conductivity and rigidity that are off the charts.  I'm hoping that one day it will be possible to consistently make the graphene sheets thick enough so that they can be used as ultra strong stators.  There will also need to be a way to shape the graphene sheets (to insert the stator holes, etc). 

 

I had this doubt also. I think stiffness can also refer to an elastic material. As I see it, it can take a lot of force without tearing apart, but it does not mean it won't bend. I have found this article particularly interesting: http://physicsworld.com/cws/article/news/2008/jul/17/graphene-has-record-breaking-strength.

 

Quote:
Originally Posted by dripf View Post
 

Thermoacoustic speakers are inefficient at audible frequencies and exhibit a response slope that is unsuitable.

 

The thickness of the diaphragm demonstrated in that paper was determined to be about 30 nm via measured light transmittance. The graphene film would represent a perfect diaphragm transducer.

 

Thank you for mentioning this paper (http://arxiv.org/ftp/arxiv/papers/1303/1303.2391.pdf)! They give the recipe to cook the graphene! Nice.

 

Quote:
Graphene was previously used to construct a thermoacoustic loudspeaker12-14. In the thermoacoustic configuration graphene serves as a stationary heater to alternately heat the surrounding air thereby producing , via thermal expansion, a time-dependent pressure variation, i.e. sound wave. The method is especially effective in the ultrasonic region because of graphene’s small heat capacity (for this reason, carbon nanotube films can also be utilized15-17). However, for thermoacoustic speakers operating at audio frequencies, most input energy is dissipated by heat conduction through the air and does not generate sound12. For example, the power efficiency for a graphene thermoacoustic speaker is exceedingly small, decreasing from ~10-6 at 20 kHz to ~10-8 at 3 kHz12,13. The thermoacoustic approach also suffers from sound distortion because the heating power is proportional to the square of the input signal and the transduction is therefore intrinsically non-linear15.
 

 

So I think thermoacoustic CNT film is ruled out...


Edited by jgazal - 4/6/14 at 4:35pm
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: High-end Audio Forum
Head-Fi.org › Forums › Summit-Fi (High-End Audio) › High-end Audio Forum › The Stax Thread III