The Headcase Stax thread

[chinsettawong]

Stax adds thin Mylar spacers to increase the spacer thickness in an SR007 MK2.  I'm pretty sure that they do the same on SR009.

 

[nopants]

Has anyone experienced AC hum while moving their heads around while wearing the 007s? I'm using my formerly-imbalanced pair with the BHSE and 323s and it seems to be consistent across both. This doesn't happen when I move the cable, just my head. If I make more sudden movements there's a more familiar squealing, not sure what that's about either.

 

I think the hum is similar to transformer hum

[Torpedo]

That's probably your brain implant interfering with the electrostatic field.

[nopants]

I have been called a dickhead historically, it's starting to make sense now

[wink]

As long as the hum  harmonically enhances the music, enjoy it.

 

If it doesn't, don't listen to those tracks.

Edited October 31, 2014 by wink

[nopants]

I'm not sure what you're getting at, it's present even with no track playing- as long as the amplifier is on

[kevin gilmore]

so the bias supply is a voltage multiplier directly off the ac line, and its really

high impedance. So anything that might load it even a little bit is going to

cause 60 hz hum. if the diaphram slams hard against the stator, its going

to discharge the bias a bit.

[nopants]

so all diaphragms are modulated in this way by the 60Hz? not that I can remember but I thought the kgsshv psu derived the bias voltage differently. I started thinking about how the hum and squeal might be related, thanks for clarifying. 

 

Is there something that could make a specific pair of ES headphones more susceptible to this than another? sensitivity?

[kevin gilmore]

there is no 60hz unless there is excess current being drawn by the headphones

 

the 500V version of the kgsshv takes the voltage directly from the main unregulated

supply, so no chance of hum even with the headphone drawing much more current

than it should.

[nopants]

What would cause excess current draw? 

 

I guess that's one reason to build the 500V version of the kgsshv

[spritzer]

I suspect there is a simpler explanation, one of the wires which goes from the cable to the drivers is broken.  Those are fiddly to say the least and can be easily broken. 

 

If enough load was put on the bias supply to reveal the AC frequency then the phones would drop in sensitivity as well, especially on the Stax amp which uses on 10nf caps in the bias supply. 

[spritzer]

Ok.... something weird just happened.      The SR-009 has seen heavy use recently off the KGST and today the right channel was suddenly quieter than the left one.  No idea why but I've been wanting this to happen so I can study what the fuck is up with these things. 

 

First thing I did was to unplug and try grounding the stators and diaphragms at various combinations.  Listening carefully when you do that gives an idea how the charge on the film is working.  Nothing concrete to be gained from that so I just grounded all 5 pins.  No change at all but when listening so some highly localized tracks I noticed the channels were drifting a tiny bit. 

 

Before ripping them apart I thought I'd at least try tapping them on the side of the housing as one does when there is some dust stuck in a driver causing it to buzz.  Well here is the weird bit, one sharp knock to the side of the offending channel and it sprung back to life.  WHAT THE ACTUAL FUCK!!??!! 

 

One thing I did observe is that the volume level of the "working" channel is lower than it should have been.  As soon as the "broken" channel kicked into full gear the volume of the "working" channel rose by 2dB or so.  Maybe a bit more.  No other conclusion can be drawn from the info at hand than the imbalance issue is not caused by a charge sitting on the diaphragm but rather some build anomaly in the driver.  

[Torpedo]

WTF? I haven't had any issue like that in all the time I've been owning the 009, more than 3 years already, but it's true that they haven't suffered anything like "heavy use" as in more than 5-6 hours of playing in a row. Let's see what you find out 

[n3rdling]

I'm guessing there's something up with the way the drivers are held together (screws loose, etc)

[nopants]

that happened to the 007 I mentioned, just shifting the earpad fixed like 6 db of imbalance

[spritzer]

The 007 driver is held together in a resin frame and the 009 as well which is then encased in the alu shell so a lot of things would have to be loose on a lot of sets.  I suspect the connection into the driver as the most plausible point of failure.  The bias is indeed attached with a screw... 

[Dusty Chalk]

The pixie/fairy fell asleep on the job due to long hours, and the knock woke her back up?

[HeadphoneAddict]

WTF? I haven't had any issue like that in all the time I've been owning the 009, more than 3 years already, but it's true that they haven't suffered anything like "heavy use" as in more than 5-6 hours of playing in a row. Let's see what you find out 

My never acted up, even after listening for four or five hours at a time.

[numbercube]

Got a Stax Lambda Pro and the drivers are crackling and squeaking from pro outputs... while everything's fine when they're driven by normal bias outputs. Apparently they have been in use with a SRD6 for years. Could that have harmed the Lambda Pros?

[Tachikoma]

Nope, but on high bias, any dust in the drivers makes a great deal more noise. If you don't mind taking the drivers apart, you could clean the stators with sticky tape and very carefully blow any dust on the membrane off.

Edited November 2, 2014 by Tachikoma

[Tachikoma]

Ok.... something weird just happened.      The SR-009 has seen heavy use recently off the KGST and today the right channel was suddenly quieter than the left one.  No idea why but I've been wanting this to happen so I can study what the fuck is up with these things. 

 

First thing I did was to unplug and try grounding the stators and diaphragms at various combinations.  Listening carefully when you do that gives an idea how the charge on the film is working.  Nothing concrete to be gained from that so I just grounded all 5 pins.  No change at all but when listening so some highly localized tracks I noticed the channels were drifting a tiny bit. 

 

Before ripping them apart I thought I'd at least try tapping them on the side of the housing as one does when there is some dust stuck in a driver causing it to buzz.  Well here is the weird bit, one sharp knock to the side of the offending channel and it sprung back to life.  WHAT THE ACTUAL FUCK!!??!! 

 

One thing I did observe is that the volume level of the "working" channel is lower than it should have been.  As soon as the "broken" channel kicked into full gear the volume of the "working" channel rose by 2dB or so.  Maybe a bit more.  No other conclusion can be drawn from the info at hand than the imbalance issue is not caused by a charge sitting on the diaphragm but rather some build anomaly in the driver.  

Any chance the membrane simply got stuck on the stators (to the point it doesn't come off after you ground it)? This, combined with the bass suckout you mentioned sounds exactly like my experience with a membrane that I coated with too much antistatic. Its also consistent with Wachara's observation that Stax increased the spacer thickness slightly, which might be to address this very issue.

Edited November 2, 2014 by Tachikoma

[Torpedo]

I've forgotten to mention that if I force a typical Stax fart on my 009s by pressing them against my skull, one of the drivers lowers its SPL output (my guess is about 3 to 6dB) for a good 20-30 seconds, then it slowly balances both channels output back to normal. Would this be consistent with the spacing issue?

[nopants]

to clear dust from the assembly there is an air bulb from giotto? that I've used in the past with some success

[Ali-Pacha]

Got a Stax Lambda Pro and the drivers are crackling and squeaking from pro outputs... while everything's fine when they're driven by normal bias outputs. Apparently they have been in use with a SRD6 for years. Could that have harmed the Lambda Pros?

I've read somewhere high bias cans won't like playing too loud out of normal bias...but I don't remember why. Birgir may help (as usual).

 

Ali

Edited November 2, 2014 by Ali-Pacha

[spritzer]

The diaphragm being stuck to a stator doesn't sit right with me for a few reasons.  First of all, a diaphragm shouldn't be able to do that in the first place.  The diaphragm is stretched tighter than the skin of a drum and there is no force inside those drivers strong enough to move it.  It also stands to reason that if the diaphragm were to move from its center point between the stators at any point then the distortion would rise dramatically.  It's a common misconception that electrostatics arc by the film touching the stator.  The film doesn't have to touch the stator for it to arc, it just needs to break down the natural insulation of the air.  That is ca. 100V/mill so certainly possible to do. 

 

Second would be how the "broken" driver sounded.  I've heard drivers which have stuck to one stator a few times but all of them have been severely damaged and the distortion was easy to spot.  This one was just lower in volume but it played just fine. 

 

Lastly how the bias supply in the KGST would have responded to diaphragm shorting out like that.  Being a simple voltage doubler it can't (nor should it) maintain anything close to full output for the working channel.  Granted it was a bit down in volume but it was one click on the DAC attenuator so not a major difference. 

 

Running Pro phones off normal bias can't do any damage what so ever.