Dry hump mod.

[NightWoundsTime]

It's funny, because not only is he annoying like our old friend Gurushanker, he actually looks like him.

I missed the post, but logging in revealed that I had two PM's from April 2011 sitting on Head-fi from Guru. Totally forgot that the last thing I'd written to him in 2008 was a fairly scathing remark on his ego and such.... Three years later after much soul seraching or something he sends two PM's full of apologies. The BS just keeps giving.

I got sick of him and yelled at him (and had a hilarious post-dude-breakup exchange of borrowed stuff). If I saw him now I'd buy him a beer and be happy knowing we're both no longer 23 years old

Edited July 17, 2012 by NightWoundsTime

[deepak]

I missed the post, but logging in revealed that I had two PM's from April 2011 sitting on Head-fi from Guru. Totally forgot that the last thing I'd written to him in 2008 was a fairly scathing remark on his ego and such.... Three years later after much soul seraching or something he sends two PM's full of apologies. The BS just keeps giving.

I got sick of him and yelled at him (and had a hilarious post-dude-breakup exchange of borrowed stuff). If I saw him now I'd buy him a beer and be happy knowing we're both no longer 23 years old

Not logging in Headfi in over a year, I envy you Matt.

[spritzer]

What I meant was that the diaphragms don't share motion, the "woofer" and "tweeter" common rim is a circular spacer which pins both membranes (one on the outer edge, one on the inner edge. This probably makes no sense from a manufacturing point of view, that wouldn't be a first coming from an acoustics guy .

I'm sure Quad would have tried to build something like that but they also never bothered to hire production engineers or look at how much some of this actually cost.

Also, from your post above, it would seem like that stator-diaphragm gap is essentially fixed by the polarization voltage. I somehow though it was adjusted based on the diaphragm tensioning and thickness (it really has to elastically deform to get shorting and my guess was the max excursion occured at the tuned LF resonance frequency, e.g. 50-75Hz for stax estats).

Anyhow, at the very least I am curious to see the effect of having two independent membranes. I "just" need to find time to update the model I made.

The diagram tension is essentially fixed (though there is some variation) and it is then put in an oven to rearrange the polymer and lock that tension in place. The tension is very high though and there is next to no excursion even at silly levels. The diaphragm certainly can never hit the stators as you can't push it that far with a finger, let alone using the very weak electrostatic force. What the diaphragm can do is vibrate while being locked in place thus creating the very low distortion output.

The bias voltage sets the film to stator distance or rather it's the other way around. If you use a voltage that is too high then the driver will arc and burn up the film. Low voltage will lessen the grip the stators have over the diaphragm and lower the sensitivity of the system. In the middle is the sweet spot which will allow enough control while allowing plenty of voltage on the stators.

Now lets discuss that a bit. The electrostatic force is by definition very, very weak and it's strength diminishes by distance squared. That's why the normal bias Stax have a 230V bias voltage of a 0.3mm D/S gap but the Pro bias is 580V for 0.5mm. The gap is up by 60% but the bias is up by a factor of 2.5. Stax could have pushed it further but they clearly wanted the same sensitivity for both standards so they could be used together on the same amps. While the SR-Omega was being designed they tried going even further (1100V or 0.6-0.7mm) but decided against it for some reason.

Now the extra distance could give more excursion but in reality is just gives the ability to put more voltage on the stators without damaging the diaphragm. The max voltage any electrostatic driver can see is bias*2 which is why the SRD-7Mk2 boxes have 450V zener diodes forming a clamping circuit for the normal bias output. The transformers are capable of crazy voltage swings so Stax tried to limit it somehow but they would never reach the 1200V needed to damage the Pro bias drivers. More voltage means more control and that the drivers can go louder without damage.

Anyway, enough from this lowly baker in Iceland as Sachi put it...

[NightWoundsTime]

Not logging in Headfi in over a year, I envy you Matt.

Well over that more than likely. Also had a guy asking about HD600 woody mods, which I guess I posted about at some point also way in the past.

[arnaud]

Anyway, enough from this lowly baker in Iceland as Sachi put it...

Hehe, if you're actually clueless, you're hiding it rather brilliantly .

Thanks for the 101 course review, it does feel like you telling me the same thing as before and I still come back some months later thinking differently, please bare with me .

Anyhow, this gets me motivated to give another shot to stax headphone acoustic simulation. Between experience of people like you and wachara and measurement capabilites of someone like purrin, there's got to be a way to come up with realistic model which could then be used to improve upon existing design (or at least help us cut the chase to the key design parameters).

I have to say though that there's been so much experimentation already that my simulation work has a steep uphill curve to climb before bringing value .

[Wmcmanus]

If I saw him now I'd buy him a beer and be happy knowing we're both no longer 23 years old

Well, at least you're not 23 anymore. Not so sure about Guru.

[spritzer]

Hehe, if you're actually clueless, you're hiding it rather brilliantly .

Thanks for the 101 course review, it does feel like you telling me the same thing as before and I still come back some months later thinking differently, please bare with me .

Anyhow, this gets me motivated to give another shot to stax headphone acoustic simulation. Between experience of people like you and wachara and measurement capabilites of someone like purrin, there's got to be a way to come up with realistic model which could then be used to improve upon existing design (or at least help us cut the chase to the key design parameters).

I have to say though that there's been so much experimentation already that my simulation work has a steep uphill curve to climb before bringing value .

Fake it 'till you make it works for me... Some proper simulations would be cool and it might be a good idea to contact DuPont and see if they have any data on how mylar behaves while under such tension and heat annealed. The newest sets use some other polymer but mylar would be a good start.

A proper simulation could also dispel the age old myths that electrostatics are just capacitors that require virtually no power and are just voltage creatures.

[arnaud]

Birgir, there are actually other software tools in my company to simulate all sorts of non linear physics (like vehicle crash worthiness, airbag deployment, parts stamping, ...). So getting the effect of stretching / tensioning is feasible, I just can't pull the resources since I do that for free on the side.

By far the easiest way to get the effect is inverse method: find out the first membrane resonance from SPL measurement (that until someone can come up with a way to measure electrical impedance), and backout what is the effective stiffness of the diaphragm using a coupled vibro-acoustic simulation under the same air loading conditions (you simply tune the properties until the resonance frequency matches). I think I did it wrong the first time around with my 009 simulation since I used the in-vaccuo vibration simulation and tune the membrane stiffness, then couple it to the acoustics. i plan on revisiting this...

[Dusty Chalk]

... there are actually other software tools in my company to simulate all sorts of non linear physics ...

Distortion? It's one of my pet projects to create a better digital distortion simulation, the starting point of which is a mathematical "best guess".

Sorry, kind of off topic, but I think this one has more or less run its course, so thought I'd drop the question here.

Uh...like it's hot.

[arnaud]

Distortion? It's one of my pet projects to create a better digital distortion simulation, the starting point of which is a mathematical "best guess".

Sorry, kind of off topic, but I think this one has more or less run its course, so thought I'd drop the question here.

Uh...like it's hot.

Yes, possibly we could model some forms of distortion, but non-linear does not mean magic and you still very much need a mathematical model for whatever you're simulating. Typical non-linear simulations are discrete time domain and with varying physical properties / geometry at each time step.

I do all my work using linear vibro-acoustic models so I couldn't help you with any non-linear types of distortion. But things like residual vibration (of the stators or enclosure for instance) are linear behaviors that I could simulate...

[kevin gilmore]

measuring the electrical impedance is going to be a major bear.

currents are super tiny and the voltages are electronics killers.

The best thing could be to make a coil of 100 turns of wire, and put

one of the drive wires thru it. Then a voltage attenuator, and a 2

channel sampling device.

[spritzer]

Bloody modern electronics with no real high voltage capabilities...

Birgir, there are actually other software tools in my company to simulate all sorts of non linear physics (like vehicle crash worthiness, airbag deployment, parts stamping, ...). So getting the effect of stretching / tensioning is feasible, I just can't pull the resources since I do that for free on the side.

By far the easiest way to get the effect is inverse method: find out the first membrane resonance from SPL measurement (that until someone can come up with a way to measure electrical impedance), and backout what is the effective stiffness of the diaphragm using a coupled vibro-acoustic simulation under the same air loading conditions (you simply tune the properties until the resonance frequency matches). I think I did it wrong the first time around with my 009 simulation since I used the in-vaccuo vibration simulation and tune the membrane stiffness, then couple it to the acoustics. i plan on revisiting this...

It would be interesting to nail down the resonance frequency of these drivers if only to see how it interacts with the sound. Stax clearly makes small alterations to the diaphragm tension between models to get the performance they want. As the engineers get older they seem to be leaning towards a brighter sound though....