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I finally got around to making direct comparisons of the Stax 404 headphone with 2 different Stax amplifiers, my old SRM-3 and a newer 717, and then compared both with the Koss 950 amplifier/headphone combination. I was somewhat suprised at some of what I heard. You may think you know about the characteristics of different systems you may own, but unless you do some controlled comparative listening,you can not really be sure if you know what your gear really sounds like.
Koss and Stax have been in the electrostatic headphone business for a long time and both have even made electrostatic speakers. Currently Koss has only the ESP 950 in its electrostatic line-up and this model has been unchanged for 15 or more years. Stax has a fairly wide range of headphone/amp combinations with local prices ranging from about $350.00 for the the SRM-001MkII portable set-up to about $5,000.00 for the Omega II with the transistor 717 or the slightly more expensive tube SRM007t amp.
I bought the Koss 950's some years ago, in part because they were a lot less expensive than comparable Stax models after Koss had lowered the price of the 950 headphone/amp combination from an inital price of about $2,000.00 to $600.00, where it more or less remains today.(although I see the Koss website listing them at $999.00.)
A few years later I picked up a Stax SRM-3 amplifier and Lambda Novas. Subsequently I modified a low bias Stax Sigmas to pro, high-bias operation and also purchased some Stax 404 Lambda's, Stax' second most expensive model but about 1/3 the price of the Omega II. At that price you would think Omega's would be the best on the market, but followers of these forums will know that there is disagreement on that score and even some disagreement as to whether they are much better or better at all than the 404.http://headwize.com/ubb/showpage.php...tid=5171&srch=
I had made an initial evaluation as to how the Stax SRM-3/Lambda compared to the Koss 950 when I first bought the Stax, by swapping one system for another with the same CD player, and it was pretty obvious the that the Koss were not as good as the Stax.
However, more recently, I experimented with a larger power supply to power the Koss amp. I replaced it ultimately with an Elenco regulated bench supply rated at 3 amps. There is nothing special about the Elenco, it is a modetsly priced bench supply, but it works well with the Koss. I have previously reported on the improvements this power supply gives, but have never started a thread on this, and at least one other member has confirmed this. http://www5.head-fi.org/forums/showt...light=koss+950
Most recently I replaced the Stax SRM3 ampifier with the more modern and more expensive Stax 717 in my best system. I made some a comparisons with it driving the Sigma pro and 404 at that time. http://www6.head-fi.org/forums/showthread.php?t=162119 However, I decided that I really wanted to do a more systematic comparison with the SRM-3 and then the Koss 950, which I had not compared since using the Elenco.
EQUIPMENT SET-UP
The comparisons were done using a CEC 51Z cd player as a transport feeding a Musical Fidelity A324 DAC. The digital signals are further processed by a Monarchy Classic jitter reducer connected by Cardas High Speed Data cables. The power cables on the DAC and Monarchy are PS Audio Plasma cables, the 717 is powered by a Cardas power cord, the SRM-3 by an HCM power cord. Interconnects between the dac and the 717 are 1/2 m Monster Cable 950I.
TWEAKS
I use sorbethane fairly generously on most items of equipment as footers. I should also mention, because it could have bearing on my impressions of sound, that I also do some serious disc tweaking. All my discs have their edges sanded, and then painted black. They are polished with Auric illuminator and each disc is weighted with either an Alsop ring which fits around the edge of each disc or an Audioquest ring whch is glued to the top of the disc. As a final tweak, I use Herbies Grungbuster, stuck to the top of each disc. Obviously I think these tweaks help. I basically find regular disc, sound flat and lifeless compared to my treated discs.
CONNECTIONS
So how do you do quick comparisons between different systems? I don't want to be switching interconnects because I feel they should be left alone after connecting. However, the 717 and SRM-3 have parallel input/outputs so it was possible to link the DAC directly to the SRM-3, then to the 717 by another Monstercable 950I. The Koss amp was then connected to the 717 by a set of Audioquest Ruby cables. Thus I could just pick up the 950 phones or the 404 to compare sound. To compare the 2 Stax amps I would unplug and replug the 404 between the two amps. I have never found the 404 to be sensitive to being briefly unplugged after it had been warmed up.
All the equipment had been run separately for several hours the day before testing and again for about 2 hours after hooking together.
LISTENING TESTS
POPULAR
I chose an early cd by Kate Bush, and which I had always liked, and the Beatles Sgt Pepper. I felt the Bush was a generally well-recorded disc, a bit treblish and Bush's voice could be at times, somewhat shrill. Thus it would make a good test of high and mid-frequency harshness an often cited complaint against electrostatics.
Listening first to the 950, I was surprised at how different the tonal balance was with the the Koss was hooked up to this system rather than its regular cd player a Sherwood Newcastle. There was much less harshness than with the Sherwood and the midbass was notably increased. In the Newcastle, I would have said that mid bass was either flat or somewhat reduced.
Switching to the Stax SRM3/404, I was initially taken aback at how close the sound was to to the Koss. There was somewhat deeper bass and also a mid bass peak, probably lower in the register than the Koss.
Plugging the 404 phones into the 717 amp, one got even deeper bass, and more extended treble. The soundstage widened notably, and there was better reproduction of ambience. The 717 had a generally cleaner sound.
While the 717/404 was clearly best, there was surpisingly little difference between the SRM-3/404 and the Koss 950. In fact there were times I had to check which phones I had on by feeling them to be sure.
I then checked the sound out with the Beatles Sgt. Pepper and found much the same characteristics. It was fairly evident that the 950's were especially good with pop music
CLASSICAL
To test the sound on classical I mainly listened to a BBC recording of Brittens suite from the opera Peter Grimes a fairly recent digital recording.
Now the Koss began to fall behind in the comparisons. There was a lack of resolution, smaller soundstage and the strings in particular seemed edgy.
The 404/717 combination again showed the wide soundstage, and sweeter treble. the bass was much deeper. There was a very deep bass almost a growl from the double basses. The 404/SRM-3 was basically half-way between the Koss and the 404/717.
Finally, I hooked up the Koss 950's directly to the DAC to see if their performance had been degraded by being last in the chain. Certainly there was some improvement in sound, things were a little clearer now but overall it was much the same as what I had heard previously.
OVERALL IMPRESSIONS
To no great surprise the Staz 404/717 had the best overall performance. Both Stax amps clearly outperformed the Koss combo in classical music. The results with pop were somewhat less clear. The Koss 950 set-up had some real strength here, partly I think because it rolled off the high frequencies somewhat more than the 404 phones geeting rid of a certain amount of high frequency emphasis and hash which seems to permeate pop recordings.
AUDIOPHILE SOUND?
It seems to be a common complaint about "audiophile" headphones that they sound thin with some kinds of music, especially pop. The reason is mostly that they provide more treble than some mixes need. The other factor is that such phones expose problems with lower levels of equipment which cheaper bassy phones cover up. Over the years I have found that with many tweaks, and add-ons, such as the Monarchy Classic jitter reducer, the sound blooms with audiophile phones and even bass seems to be pumped up.
Pop music seems to be recorded with treble emphasis, probably to sound good on low grade systems, lacking good tweeters. I recall reading notes on a Beachboy album in which it was reported that the final sound was adjusted to sound good on a monaural car radio of the 60's. Such systems had no tweeters at all. A mix for this is unlikely to sound good on a high definition system with an extended high frequency response.
Of course there are large differences in the tonal balance of different recordings. After the above tests, I listened to a Teldec recording of Prokofiev's violin concerto and the sound of the string section and the solo violin playing in their upper registers was simply enchanting with the the 717/404 combination.
Of course not all electrostatics that have high levels of treble. The Stax portable SR001, or its mate the SR003, have a fairly rolled off treble which probably fits the somewhat harsh sources such as portable cd players and pop music that may be played on the go. I have tried the 003 with the 717 and while the 717 boosts the treble somewhat it is still rolled off compared to the 404. Stax' older Sigma phones, the boxy predecessor of the 404 also rolls off treble quite markedly. Probably such phones would be preferred by those with less tolerance for high frequncy anomalies. I believe even the Stax Omega has a somewhat rolled off treble.
Probably the main point of note is that the Koss, which sells for half or less the price of a medium price Stax combo performs so well when a better power supply is used with pop music.
Others have commented on how good these phones themselves can sound with other amps. http://headwize.com/ubb/showpost.php...=1220&pid=9043. Kevin Gilmore has suggested that you throw away the amp, but I believe it is a much better amp when given better power. Others have thought quite highly of them even without the better power supply http://www6.head-fi.org/forums/showt...koss+esp%2F950
Still all the headphone/amp combos tested here are good. There is nothing I'm going to be selling on Ebay in the near future.
Koss and Stax have been in the electrostatic headphone business for a long time and both have even made electrostatic speakers. Currently Koss has only the ESP 950 in its electrostatic line-up and this model has been unchanged for 15 or more years. Stax has a fairly wide range of headphone/amp combinations with local prices ranging from about $350.00 for the the SRM-001MkII portable set-up to about $5,000.00 for the Omega II with the transistor 717 or the slightly more expensive tube SRM007t amp.
I bought the Koss 950's some years ago, in part because they were a lot less expensive than comparable Stax models after Koss had lowered the price of the 950 headphone/amp combination from an inital price of about $2,000.00 to $600.00, where it more or less remains today.(although I see the Koss website listing them at $999.00.)
A few years later I picked up a Stax SRM-3 amplifier and Lambda Novas. Subsequently I modified a low bias Stax Sigmas to pro, high-bias operation and also purchased some Stax 404 Lambda's, Stax' second most expensive model but about 1/3 the price of the Omega II. At that price you would think Omega's would be the best on the market, but followers of these forums will know that there is disagreement on that score and even some disagreement as to whether they are much better or better at all than the 404.http://headwize.com/ubb/showpage.php...tid=5171&srch=
I had made an initial evaluation as to how the Stax SRM-3/Lambda compared to the Koss 950 when I first bought the Stax, by swapping one system for another with the same CD player, and it was pretty obvious the that the Koss were not as good as the Stax.
However, more recently, I experimented with a larger power supply to power the Koss amp. I replaced it ultimately with an Elenco regulated bench supply rated at 3 amps. There is nothing special about the Elenco, it is a modetsly priced bench supply, but it works well with the Koss. I have previously reported on the improvements this power supply gives, but have never started a thread on this, and at least one other member has confirmed this. http://www5.head-fi.org/forums/showt...light=koss+950
Most recently I replaced the Stax SRM3 ampifier with the more modern and more expensive Stax 717 in my best system. I made some a comparisons with it driving the Sigma pro and 404 at that time. http://www6.head-fi.org/forums/showthread.php?t=162119 However, I decided that I really wanted to do a more systematic comparison with the SRM-3 and then the Koss 950, which I had not compared since using the Elenco.
EQUIPMENT SET-UP
The comparisons were done using a CEC 51Z cd player as a transport feeding a Musical Fidelity A324 DAC. The digital signals are further processed by a Monarchy Classic jitter reducer connected by Cardas High Speed Data cables. The power cables on the DAC and Monarchy are PS Audio Plasma cables, the 717 is powered by a Cardas power cord, the SRM-3 by an HCM power cord. Interconnects between the dac and the 717 are 1/2 m Monster Cable 950I.
TWEAKS
I use sorbethane fairly generously on most items of equipment as footers. I should also mention, because it could have bearing on my impressions of sound, that I also do some serious disc tweaking. All my discs have their edges sanded, and then painted black. They are polished with Auric illuminator and each disc is weighted with either an Alsop ring which fits around the edge of each disc or an Audioquest ring whch is glued to the top of the disc. As a final tweak, I use Herbies Grungbuster, stuck to the top of each disc. Obviously I think these tweaks help. I basically find regular disc, sound flat and lifeless compared to my treated discs.
CONNECTIONS
So how do you do quick comparisons between different systems? I don't want to be switching interconnects because I feel they should be left alone after connecting. However, the 717 and SRM-3 have parallel input/outputs so it was possible to link the DAC directly to the SRM-3, then to the 717 by another Monstercable 950I. The Koss amp was then connected to the 717 by a set of Audioquest Ruby cables. Thus I could just pick up the 950 phones or the 404 to compare sound. To compare the 2 Stax amps I would unplug and replug the 404 between the two amps. I have never found the 404 to be sensitive to being briefly unplugged after it had been warmed up.
All the equipment had been run separately for several hours the day before testing and again for about 2 hours after hooking together.
LISTENING TESTS
POPULAR
I chose an early cd by Kate Bush, and which I had always liked, and the Beatles Sgt Pepper. I felt the Bush was a generally well-recorded disc, a bit treblish and Bush's voice could be at times, somewhat shrill. Thus it would make a good test of high and mid-frequency harshness an often cited complaint against electrostatics.
Listening first to the 950, I was surprised at how different the tonal balance was with the the Koss was hooked up to this system rather than its regular cd player a Sherwood Newcastle. There was much less harshness than with the Sherwood and the midbass was notably increased. In the Newcastle, I would have said that mid bass was either flat or somewhat reduced.
Switching to the Stax SRM3/404, I was initially taken aback at how close the sound was to to the Koss. There was somewhat deeper bass and also a mid bass peak, probably lower in the register than the Koss.
Plugging the 404 phones into the 717 amp, one got even deeper bass, and more extended treble. The soundstage widened notably, and there was better reproduction of ambience. The 717 had a generally cleaner sound.
While the 717/404 was clearly best, there was surpisingly little difference between the SRM-3/404 and the Koss 950. In fact there were times I had to check which phones I had on by feeling them to be sure.
I then checked the sound out with the Beatles Sgt. Pepper and found much the same characteristics. It was fairly evident that the 950's were especially good with pop music
CLASSICAL
To test the sound on classical I mainly listened to a BBC recording of Brittens suite from the opera Peter Grimes a fairly recent digital recording.
Now the Koss began to fall behind in the comparisons. There was a lack of resolution, smaller soundstage and the strings in particular seemed edgy.
The 404/717 combination again showed the wide soundstage, and sweeter treble. the bass was much deeper. There was a very deep bass almost a growl from the double basses. The 404/SRM-3 was basically half-way between the Koss and the 404/717.
Finally, I hooked up the Koss 950's directly to the DAC to see if their performance had been degraded by being last in the chain. Certainly there was some improvement in sound, things were a little clearer now but overall it was much the same as what I had heard previously.
OVERALL IMPRESSIONS
To no great surprise the Staz 404/717 had the best overall performance. Both Stax amps clearly outperformed the Koss combo in classical music. The results with pop were somewhat less clear. The Koss 950 set-up had some real strength here, partly I think because it rolled off the high frequencies somewhat more than the 404 phones geeting rid of a certain amount of high frequency emphasis and hash which seems to permeate pop recordings.
AUDIOPHILE SOUND?
It seems to be a common complaint about "audiophile" headphones that they sound thin with some kinds of music, especially pop. The reason is mostly that they provide more treble than some mixes need. The other factor is that such phones expose problems with lower levels of equipment which cheaper bassy phones cover up. Over the years I have found that with many tweaks, and add-ons, such as the Monarchy Classic jitter reducer, the sound blooms with audiophile phones and even bass seems to be pumped up.
Pop music seems to be recorded with treble emphasis, probably to sound good on low grade systems, lacking good tweeters. I recall reading notes on a Beachboy album in which it was reported that the final sound was adjusted to sound good on a monaural car radio of the 60's. Such systems had no tweeters at all. A mix for this is unlikely to sound good on a high definition system with an extended high frequency response.
Of course there are large differences in the tonal balance of different recordings. After the above tests, I listened to a Teldec recording of Prokofiev's violin concerto and the sound of the string section and the solo violin playing in their upper registers was simply enchanting with the the 717/404 combination.
Of course not all electrostatics that have high levels of treble. The Stax portable SR001, or its mate the SR003, have a fairly rolled off treble which probably fits the somewhat harsh sources such as portable cd players and pop music that may be played on the go. I have tried the 003 with the 717 and while the 717 boosts the treble somewhat it is still rolled off compared to the 404. Stax' older Sigma phones, the boxy predecessor of the 404 also rolls off treble quite markedly. Probably such phones would be preferred by those with less tolerance for high frequncy anomalies. I believe even the Stax Omega has a somewhat rolled off treble.
Probably the main point of note is that the Koss, which sells for half or less the price of a medium price Stax combo performs so well when a better power supply is used with pop music.
Others have commented on how good these phones themselves can sound with other amps. http://headwize.com/ubb/showpost.php...=1220&pid=9043. Kevin Gilmore has suggested that you throw away the amp, but I believe it is a much better amp when given better power. Others have thought quite highly of them even without the better power supply http://www6.head-fi.org/forums/showt...koss+esp%2F950
Still all the headphone/amp combos tested here are good. There is nothing I'm going to be selling on Ebay in the near future.
