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The Headcase Stax thread


thrice
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Binaural recordings are usually based on dummy head microphones. The outer ear (pinnae), the distance between diaphragms (mimics the distance between your tympanic membranes or at least the entrance of your auditory canal) and torso reflections and absorptions will not match the way it happens with the vast majority of the population.
Have you actually heard binaural recordings that aren't based on your own personal HRTF? They really aren't that bad, quite listenable, and quite (still) binaural.
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A lot of people say that hd800 has a much more expansive sound stage than the O2s.

I have found this to simply NOT be true. I can however understand why people have come to this conclusion, and that is simply because the hd800 sound more distant. The hole in the midrange will only emphasize this attribute, making vocals sound slightly further away.

As the O2 doesnt seem to have this problem, things are layered much more realistically, accounting for the awesome pin point imaging, and I believe it does go much wider. I cant wait to see how they respond to improved amplification.

Some saving graces for the hd800 though, I do think it has slightly better detail retreival and things seem to have a bit more "texture" although some might call it "coarseness." Remember though that the hd800 is running off much "better" amplification than the O2.

The HD800 has a larger soundstage than the O2.

To be sure, we're talking about the soundstage illusion, where the sounds seem to appear at varying distances away from your head. It's not like speaker soundstage, it's the artificial headphone-type of soundstage, which some people claim isn't actually soundstage at all. In Darth Nut's classic O2 review, he talks a lot about this aspect of the O2 vs. SR-Omega (another headphone with a larger soundstage than the O2) and even coins the term "headstage" to distinguish between the soundstage illusion and the places where the sounds seem to emanate from around your head. Which is actually another illusion, because the sounds are produced by those things strapped over your ears. ;)

One may prefer the O2's soundstage, or think that it presents a more coherent and realistic portrayal. Those are opinions, while it's fact that the HD800 has a larger soundstage than the O2.

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Have you actually heard binaural recordings that aren't based on your own personal HRTF? They really aren't that bad, quite listenable, and quite (still) binaural.

You are absolutely right. I have these CD's:

cduniverse.com - Richard Strauss (Also Sprach Zarathustra) - Camille Saint Saens (Symphony No.3 -Organ)

cduniverse.com - Pearl Jam (Binaural)

I also have a demo disc from Ultrasone (just the disc, not the headphones).

They are all very good.

What I was trying to say is that I always searched for out of the head lifelike "sound image" (avoiding to use the term “sound stage”).

While binaural recordings really do the trick, it is usually presented in the back of my head. Perhaps your pinnae etc. is similar to Neumann KU100.

In-front localization is very poor to me. It is said that sounds coming from your front does not have delays or frequency deviation, thus you unwittingly slightly turn your head so that your brain is able to calculate where they come from.

That's why that DSP I have mentioned also use head-tracking and it lets you measure the center channel of a multi-channel home theater system so that you can measure it right there where your TV is going to be during the playback. It also lets you to control the speaker’s azimuth so you can virtually place them wherever you like and to alter the room reverberation. It is a piece of very solid audio engineering knowledge (primarily an algorithm).

I also have the same disappointment with cross-feed circuits some years ago. I thought it would be a 3D revolution. And it was just a subtle effect which kept images inside my head...

I just wanted to let this clear. Binaural recordings really help to retrieve the venue tonal ambience (reverberation, reflections etc.), but it does not retrieve the 3D “sound image”.

No need to mention that such DSP comes with an electrostatic headphone and amplifier combo. They had feared that users would blame the DSP for deficiencies in their current headphones (poor ones like ear buds etc.) so they have chosen to sell it with a faithful headphone (SR-202 + SRM252II). This might be evidence that any electrostatic headphone is generally suited for binaural recordings. What does really make a difference is HRTF matching (call it personalization if you want).

Best regards,

Jose Luis

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Hmmm, I just had a listen to my hd800s just then, I still think the O2 has much more width then the hd800. Mind you this is only to the left and right of the drivers themselves, not vertical.

OK, then. It seems I may have overstated the fact and opinion thing.

How's this: In most cases, the HD800 should have a larger soundstage than the O2. But this may depend on the listener, the system, the recording, and the conception and definition of "soundstage" itself. :D

Anyway, if you're enjoying a wider left-right soundstage with the O2 than the HD800, your O2 system is doing something very right.

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That's enough about those inferior dynamics!!! :D

So I've been working on this SR-Omega that needed some TLC. I don't think I've ever posted pics of an empty SR-Omega shell to show why I sometimes call them the tin cans... :)

p1000547t.th.jpg

p1000548.th.jpg

p1000549b.th.jpg

p1000550h.th.jpg

As you can see the cups are very thin and it is mostly just plastic in there. Couple that to the huge driver and no wonder they get a bit ill tempered at higher volume levels. Far cry from the SR-007 design where the drivers are securely mounted in a large slab of metal. Another insteresting bit is that Stax grounded the metal enclosure through large resistors to the + and - terminals.

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Spritzer, does this apply to the Omega II as well?

BK

That's enough about those inferior dynamics!!! :D

So I've been working on this SR-Omega that needed some TLC. I don't think I've ever posted pics of an empty SR-Omega shell to show why I sometimes call them the tin cans... :)

p1000547t.th.jpg

p1000548.th.jpg

p1000549b.th.jpg

p1000550h.th.jpg

As you can see the cups are very thin and it is mostly just plastic in there. Couple that to the huge driver and no wonder they get a bit ill tempered at higher volume levels. Far cry from the SR-007 design where the drivers are securely mounted in a large slab of metal. Another insteresting bit is that Stax grounded the metal enclosure through large resistors to the + and - terminals.

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That's enough about those inferior dynamics!!! :D

So I've been working on this SR-Omega that needed some TLC. I don't think I've ever posted pics of an empty SR-Omega shell to show why I sometimes call them the tin cans... :)

p1000547t.th.jpg

p1000548.th.jpg

p1000549b.th.jpg

p1000550h.th.jpg

As you can see the cups are very thin and it is mostly just plastic in there. Couple that to the huge driver and no wonder they get a bit ill tempered at higher volume levels. Far cry from the SR-007 design where the drivers are securely mounted in a large slab of metal. Another insteresting bit is that Stax grounded the metal enclosure through large resistors to the + and - terminals.

What is that knob-like thingy in the middle? Edit: Scratch that, it looks a heck lot more sturdy than the drivers I've seen on the SR-5/X at least.

One thing I'm curious about, if we increased the bias voltage on the O2, would it make it easier to drive?

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What is that knob-like thingy in the middle? Edit: Scratch that, it looks a heck lot more sturdy than the drivers I've seen on the SR-5/X at least.

They are two pieces of neoprene rubber with adhesive backing, one on top of the other use to damp any ringing from the two metal grills. The first units didn't have them so they were a later addition.

One thing I'm curious about, if we increased the bias voltage on the O2, would it make it easier to drive?

That hasn't been my experience. I've gone up to 900V and they really couldn't have cared less. :D What the SR-007 really needs isn't more power, just a very stable amp that doesn't give a damn about the load it sees.

Is $370 a decent deal for an SRM-1/Mk2 C series?

FS: STAX SRM-1 / MK-2 Amplifier - 'C' Series - Head-Fi.org Community

It's a bit high since there is nothing special about this amp. The whole C-series stigma only applies to some units which had the same PCB as the rare PP units. They had better wiring (massive solid core PC-OCC wires) and better resistors. I would ask for an internal shot to verify that this isn't just a plain old SRM-1 Mk2.

Edited by spritzer
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Would you mind going into the differences between the different SRM1 MK2 series and versions a little more, Spritzer?

Reason for this: A friend and I both have said amps (his is a B, mine an A) with the only apparent difference being, that the B series seems to use fancy looking wirewound resistors (damn, lowpasses everywhere :D) while the A one uses metal film types; and if I recall correctly the Q201/101 fet pair looked different as well - but I am not sure about this, got no pic of his amp internals... only of mine, see below.

We never got round to compare the two head to head.

Thanks!

_dsc6684yej4.jpg

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There is no way to nail down the SRM-1 Mk2 amps in terms of serial number or series. Way too much crossing over and since this is by far the most popular amp Stax ever made, there are a lot of revisions and different parts used. That amp doesn't have the 2SJ109 dual fet but otherwise it is the same circuit.

Here is a pic of the PP I'm rebuilding, this is what a late C-type should look like on the inside (minus the balanced pot and my other mods):

p1000559o.th.jpg

It would have been nice to have the heatsink as well but one can't be too picky... :D

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Heatsinks are overrated for class A amps anyway; way more fun to run them without :D

Hmm... those resistors look familiar - don't know about the rest however. There seem to be no obvious differences between the pcbs of your PP and my A - except for the slightly moved/shortened vertical brigde-wires and a larger cap in the norm bias circuit .

Has anybody ever measured (or simulated) actual performance differences between the different revisions (ie different input fet pairs)? Or is the whole part-mania purely auto-suggestion?

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The different parts are mostly due to the amp being made from 1982 to 1992. The 2SJ109 didn't exist back in 1982 hence the J75 used instead.

That layout is indeed the final one as the original Mk2 normal bias amp had only two main PSU caps instead of 3. The first A models used that PCB as well and an off board Pro bias supply.

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