The Headcase Stax thread

[catscratch]

That info is actually not very easy to find. I tried some searching a while ago and a lot of it is scattered in small pieces and buried in various places.

The SR-007 and SR-007A (or SR-007 Mk2) do sound different. Some people prefer the O2Mk1, some prefer the O2A or O2Mk2. The number of people who have heard both is still not very large, though. Different systems and different amps also affect the sound.

I prefer the O2Mk2. But the difference with the O2Mk1 isn't very large. They sound very similar, and are a closer-sounding pair than most any other set of two headphones.

The O2Mk2 has a more forward-sounding midrange, more bass quantity, a bit better imaging and a larger headstage. I find the O2Mk2 to be more engaging and involving, and its larger headstage to be a very welcome improvement. I've always thought the O2Mk1's headstage to be small. Even so, the O2Mk2's headstage is still not very large compared to the HE90, R10, Qualia, K701, etc. By headstage, I'm talking about the distinction between headstage and soundstage as defined by darth nut in his long ago review of the O2.

Some of the differences could be due to the different earpads. The O2Mk2 also has a port.

Others can tell you more about their construction differences. SQ-wise I think both headphones are excellent and owning either one should basically be equally satisfying to most people.

Interesting. I was hoping you'd say that the O2 Mk1 would be quite a bit better, since the Mk2 is pissing me off right now. There are three things very wrong: 1) insufficient deep bass 2) overemphasized and bloated midbass 3) midrange tone (way too cold and shouty). This is in spite of nearly everything else being very much right.

Still haven't done the port mod - maybe this weekend. I don't have blu-tak yet though I have some non-reversible cement to plug those ports, though I'd wager it would probably be a more wise idea to get blu-tak in the first place

But, your findings are also making me think that the rest of my signal path is a lot more subpar for this rig than I originally thought. Now, I intentionally haven't spent a ton on upgrading it since I haven't yet settled on the headphone that I want to build the rig around - but maybe if I'm to hear what the headphones really have to offer, I don't have a choice.

Other than that, I'm thinking that there might be a FS: O2 MK2 soon followed by a WTB: O2 Mk1... and a new signal path to feed it all.

Don't get me wrong, I still think the Mk2 is a very good headphone, fabulous in fact, but in this rig it's colored in all the wrong ways. It sounds like it's trying too hard to impress, whereas in truth, with a transducer this detailed and this dynamic you don't need to try to impress; you just sit back and let the music do the impressing for you. With some genres - especially rock and small-scale ensembles - it works well, but with my favorite electronica, where I know every nuance of every vocal, tone of every instrument and sample down to a fault, it really gets on my nerves.

On a far more positive note, I finally managed to get a good fit after some time of wrestling with the headband and getting it into shape. The issue was me not being used to having a bit of pressure at the back of the ear, since for the best fit I find that the headphones have to sit slightly forward on the ear, angling the pinna a bit outwards. But, now that I'm more used to it, fit is finally fine, and damn, they are some comfortable headphones. Spectacular, in fact. I'm also surprised as to how much bass quantity changes with fit - I was finding them deep-bass non-existent and generally bass-deficient, but now there's too much midbass and not enough deep bass, with the overall bass quantity being a bit on the thick side.

I think I'll stop bitching and plug those ports as soon as I have the time and patience.

[deepak]

There is no lack of extension on my SR-007 MK1. The bass is slightly bloated when compared to the Koss ESP/950- which is fast and detailed, but lacks the extension and impact of the O2.

I'm pretty sure my transformer box and low quality power amp (I really want to hear this setup with the Beta22) are what is causing this. It's a minor point and only really noticable in direct comparison with the Koss.

The midrange is absolutely flawless on the O2 (again IMHO), if I could get a pair of speakers that sound like the O2 I would be in heaven. I'm pretty excited about hearing the Sound Lab Majestic 945

[grawk]

I think plugging the ports won't solve your problem. Upgrading your amplification might. Head to the next meet justin will be at, and try it with a KGBHSE

[Dusty Chalk]

...the Mk2 is pissing me off right now. There are three things very wrong: 1) insufficient deep bass 2) overemphasized and bloated midbass 3) midrange tone (way too cold and shouty). This is in spite of nearly everything else being very much right.

x2 what Dan said -- what are you using for amplification? Nearly every amp I've heard Stax on have had perfectly adequate, controlled, deep, extended bass -- not monsters, mind you, but there's certainly enough there there. And that's including the "measly" little SRM-310.

[Elephas]

Interesting. I was hoping you'd say that the O2 Mk1 would be quite a bit better, since the Mk2 is pissing me off right now. There are three things very wrong: 1) insufficient deep bass 2) overemphasized and bloated midbass 3) midrange tone (way too cold and shouty).

Hmm, I don't doubt this is true for you, but I am a bit puzzled because it isn't my experience.

Regarding the lack of deep bass, you're not the only one with this complaint, I remember spritzer and audiod having the same issue.

Can you list some tracks where the O2Mk2 is lacking deep bass compared to the O2Mk1?

For example, Jennifer Warnes' "Way Down Deep" from The Hunter is a track with some deep bass.

[spritzer]

There are three things very wrong: 1) insufficient deep bass 2) overemphasized and bloated midbass 3) midrange tone (way too cold and shouty). This is in spite of nearly everything else being very much right.

These are the three exact reasons why I tore my 007A apart to try and fix it. Plugging the ports does fix the bass issues but they are still a bit shouty. It's clearly not the drivers though as the SR-Omega hybrid sounds great and it uses 007A drivers. The overly emphasized midrange could be caused by a number of things and I'm sure I can "fix" it but working on any one of the Omega's takes a lot of time. A small calibration and then 15 minutes of piecing them back together will get old very quickly.

The bottom line here is that Stax made a bad call IMHO and made a more impressive phone that does sound good for a while but to those that love the Mk1 there is no comparison.

[spritzer]

Hmm, I don't doubt this is true for you, but I am a bit puzzled because it isn't my experience.

Regarding the lack of deep bass, you're not the only one with this complaint, I remember spritzer and audiod having the same issue.

Can you list some tracks where the O2Mk2 is lacking deep bass compared to the O2Mk1?

For example, Jennifer Warnes' "Way Down Deep" from The Hunter is a track with some deep bass.

There are no special tracks I can remember now (been at work now for 15 hours so all memory is shot) but it's something you hear with almost everything. The SR-007A and He90 bass are similar in a way that they allude to some deep bass that the phones can't deliver in the end (all show and no go) while the Mk1 is the exact opposite. The SR-Omega is between as it can pull off complex and deep bass but the chassis can dissipate the energy so turn up the volume and you have some excessive midbass bloom.

[slwiser]

Question for the gallery: When a spec states that an amp has 450v RMS how does that compare with 1200 volt Peak to Peak? Is it 1200 divided by 2 times 0.707 which approximates 425 volts RMS? So 450 volts RMS > 1200 volts PP, right?

[n_maher]

Question for the gallery: When a spec states that an amp has 450v RMS how does that compare with 1200 volt Peak to Peak? Is it 1200 divided by 2 times 0.707 which approximates 425 volts RMS? So 450 volts RMS > 1200 volts PP, right?

Yes, they're the same - at least based on my understanding they are. 425V RMS roughly translates to 1200V peak to peak.

In your example you know the RMS voltage = 425. To convert that to the peak (not peak to peak) you divide by .707.

425/.707 = 601V

Peak to peak voltage is double the peak voltage.

2 x 601 = 1200V

Hope that helps.

Edited July 18, 2008 by n_maher

[spritzer]

Question for the gallery: When a spec states that an amp has 450v RMS how does that compare with 1200 volt Peak to Peak? Is it 1200 divided by 2 times 0.707 which approximates 425 volts RMS? So 450 volts RMS > 1200 volts PP, right?

That is correct. Something like the BH will output around 600V RMS and the KGSS 495v RMS if my memory and calculations are correct. The small Koss amp can do 810v RMS according to the instructions manual... but sounds like shit and can't drive anything.

[slwiser]

That is correct. Something like the BH will output around 600V RMS and the KGSS 495v RMS if my memory and calculations are correct. The small Koss amp can do 810v RMS according to the instructions manual... but sounds like shit and can't drive anything.

For the KGSS design I would guess it would depend on how the builder set the PP voltage. On the Headamp site Justin specs a pp voltage of 1200 volts. It could be higher if he wanted to stress the components more I would assume by design. As you noted it could be as high as 495v RMS but it would appear to be set lower at about 425 volts for conservatism.

Thanks for everyone's input.

[Guest aaron313]

Hey spritzer, when I eventually purchase my O2 MkII, can I send it to you for mods?

[spritzer]

For the KGSS design I would guess it would depend on how the builder set the PP voltage. On the Headamp site Justin specs a pp voltage of 1200 volts. It could be higher if he wanted to stress the components more I would assume by design. As you noted it could be as high as 495v RMS but it would appear to be set lower at about 425 volts for conservatism.

Thanks for everyone's input.

Ahh I forgot that the stock KGSS runs on +/-350v and not 400v...

Hey spritzer, when I eventually purchase my O2 MkII, can I send it to you for mods?

No.

[The Monkey]

No.

[GPH]

Hey spritzer, when I eventually purchase my O2 MkII, can I send it to you for mods?

I've heard markl has a Ph.D. in headphone damping, you should ask him.

[slwiser]

Ahh I forgot that the stock KGSS runs on +/-350v and not 400v...

No, it apparently is not +/- 350 volts but something like +/-425volts for the stock KGSS.

[Guest aaron313]

No.

Owned .

[spritzer]

No, it apparently is not +/- 350 volts but something like +/-425volts for the stock KGSS.

A stock Blue Hawaii is +/-400v so the KGSS is less then that or +/-350v though it can be run at 400v+. I would like to run the BH on 550v+ but capacitors are a problem at this level though I have some huge oil caps that can handle the voltage...

it was an honorary doctorate, and it was from Dipshit University.

...and here I was thinking he was just a fucktard...

Owned .

I'm not a MOT so I don't work on stuff for others unless there are some very special circumstances.

[slwiser]

No, it apparently is not +/- 350 volts but something like +/-425volts for the stock KGSS.

A stock Blue Hawaii is +/-400v so the KGSS is less then that or +/-350v though it can be run at 400v+. I would like to run the BH on 550v+ but capacitors are a problem at this level though I have some huge oil caps that can handle the voltage...

I got it wrong in my post for the KGSS from Headamp per that spec. It is +/- 600 volts since it is 1200v PP. It is 425V RMS as noted in the first of my posts on this subject for the KGSS as spec'ed on the Headamp listing for Justin's KGSS. I would think the KGBH would be more like +/- 530 volts RMS being spec'ed at something like 1500v peak to peak (PP) or 750+/- volts. So to summarize hopefully correctly this time.

Headamp KGBH --1500vpp (+/- 750v) or ~530v RMS

Stax 727 -- ~1250vpp (+/- 625v) or ~450v RMS

Headamp KGSS-- 1200 vpp or ~425v RMS

Another interesting note is that on some of the Stax amps they are spec'ed having either 500x gain or 1000x gain. The 727 is noted as having a gain of 500x not the 1000x gain that is suggested as being needed for the SR-007MkII somewhere around here.

I now am interested in the relationship between the gain and the voltage swing if anyone can provide additional insight I would appreciate it.

My take, which is completely conjecture at this time, is that for the KGSS being a constant current amp is different from the Stax amps which may be constant voltage amps. Therefore the relationship between gain and voltage may not be consistent comparing these with each of these amps.

Help from KG would be appreciated here. I am out of my depth but attempting to learn.

[justin]

The output voltage is measured stator to stator so your numbers are all double. So you'd need +/-300V. But the amp runs on +/-350V, because it does not swing all the way to the rails.

There is no relationship between gain and voltage swing. A KGSS built with a gain of 500 and one built with a gain of 1000 have identical max output power. It's possible with a low output source you wouldn't be able to realize that max output with a gain of 500. But 99.9% of the time it just means you'll have the volume knob 2 or 3 clicks higher than with a gain of 1000.

[spritzer]

I got it wrong in my post for the KGSS from Headamp per that spec. It is +/- 600 volts since it is 1200v PP. It is 425V RMS as noted in the first of my posts on this subject for the KGSS as spec'ed on the Headamp listing for Justin's KGSS. I would think the KGBH would be more like +/- 530 volts RMS being spec'ed at something like 1500v peak to peak (PP) or 750+/- volts. So to summarize hopefully correctly this time.

Headamp KGBH --1500vpp (+/- 750v) or ~530v RMS

Stax 727 -- ~1250vpp (+/- 625v) or ~450v RMS

Headamp KGSS-- 1200 vpp or ~425v RMS

We are talking about two completely different things here. I was talking about the rail voltages for the output stage as Justin said which are a good way to see maximum output voltage. More voltage will only make the amp go much louder and not give more power. A Jecklin Float adapter swings a lot more voltage then any Stax unit but that's due to different driver design i.e. a larger D/S gap.

That being said, voltage isn't that hard to come by but you also need current due to the wild impedance curve of an electrostatic element. It's a similar situation as with low and high impedance dynamics though electrostatics are both. The impedance is very high in the midrange but drops dramatically in the bass and treble. To maintain the same output voltage into a lower impedance you need current and that's where the Stax amps fall short. Right now I'm listening to my SR-Omega hybrid on a SRM-1 and it simply can't feed the treble and bass so when I increase the volume (voltage) the sound is louder but there is no more power to be had so the bass is still tubby and the treble rolled off.

[slwiser]

justin..thanks for jumping in and helping clear up my understanding...

where is the peak to peak of 1200 voltage measured? This obviously is not the stator to stator measurement that you noted as being +/- 350volts. So if it were to run all the way to the rails it would be the spec'ed ~425volts RMS?

So in the PR literature we have specs noted as being RMS and Peak to Peak and in your discussion above rail to rail. It is noted that Stax amps are spec'ed as having outputs anywhere from of 280 to 450 volts RMS depending on the amp except for the T2 which is 600 volts RMS. Are these measured at the same location as well?

[spritzer]

justin..thanks for jumping in and helping clear up my understanding...

where is the peak to peak of 1200 voltage measured? This obviously is not the stator to stator measurement that you noted as being +/- 350volts. So if it were to run all the way to the rails it would be the spec'ed ~425volts RMS?

So in the PR literature we have specs noted as being RMS and Peak to Peak and in your discussion above rail to rail. It is noted that Stax amps are spec'ed as having outputs anywhere from of 280 to 450 volts RMS depending on the amp except for the T2 which is 600 volts RMS. Are these measured at the same location as well?

Again you are confusing rail voltage with output voltage. Like Justin said the KGSS runs on a +/-350v power supply which would give an output swing of 1400v P-P if run all the way but it isn't so the output voltage is 1200vP-P. A Blue Hawaii runs on a +/-400v PSU so it could output 1600vP-P and Stax would have used a +/-450v PSU in the T2 to reach the 630vRMS figure.

[slwiser]

Again you are confusing rail voltage with output voltage. Like Justin said the KGSS runs on a +/-350v power supply which would give an output swing of 1400v P-P if run all the way but it isn't so the output voltage is 1200vP-P. A Blue Hawaii runs on a +/-400v PSU so it could output 1600vP-P and Stax would have used a +/-450v PSU in the T2 to reach the 630vRMS figure.

Spritzer...you are correct in that I have been confusing these values. This extra that you gave me helped me a lot. One is the Power Supply swing the other is the output voltage swing. I was not getting this distinction before. Thanks

[spritzer]

Spritzer...you are correct in that I have been confusing these values. This extra that you gave me helped me a lot. One is the Power Supply swing the other is the output voltage swing. I was not getting this distinction before. Thanks

No problem.