edstrelow

John, like you, I am getting increasingly annoyed with my 007A, (although I believe you had the 007Mk1.) Sure they have more detail and better frequency response than either the Sigma pro or Sigma/404. But you know, that's not enough. They are just not that pleasant to listen to, Too dry and bright. That's why I am so far underwhelmed by the reports abnout the 009, since it seems even brighter than the 007A and that I can't see enjoying anything brighter than the 007A. even if it has even more detail. I am tempted sell the 007A and cannabalize my Sigma low bias and try to fit in one of the newer drivers such as the 507 which seems to be reported as fairly bright. I believe you can feed a lot of high frequencies into a Sigma and get a good result because it doesn;t send the sound straight down the ear canal and adds some of its own ambience. This was part of my hope with the Sigma/404, the 404 driver was fairly bright. Although evidently John Buchanaan's experience with transformer set up doesn't make it sound brighter than the Sigma Pro. I understand that the 507 driver doesn't fit well, in the Sigma box, but my thought is to take the 507 driver with its baffle and cut the baffle, if necessary, to fit the front of the Sigma. Probably my main disincentive is that I don't like the idea of sacrificing a perfectly good low bias Sigma, although I have no hesitation sacrificing a Lambda.

This article shows significantly more high frequency roll-off http://www.regonaudio.com/Records%20and%20Reality.html Here is a quote: "Now you see why concert hall response is at least potentially flat across the midrange, but tends to roll off as soon as air absorption becomes a significant factor, for around 4 kHz up. There just is not much higher frequency energy around in the reverberant soundfield because, as the sound bounces around the hall, the air soaks up the highs even if the walls don't. " Overall it gives a good discussion of such matters and some interesting measurements of concert hall acoustics. Getting back to what should be the right high frequency response of headphones, the other part of my observation was that many recordings seem bright. For me this is shown by a comparison of recordings with the old Telarcs which often made a ppoint of using simple 2 channel mic setups with no equalization and no highlighting of individual instruments with near mics such that hf attenuiation hasn't kicked in. To my ear these sound pretty good with most phones, but often somewhat mushy through speakers. As well, as the above article notes, in concert hall listening the sound gets even less bright because ambience and reverberation become a bigger factor. One of the halls gives what looks like a 25+ dB drop at 8kHz. for sound measured at the loge level, which would be the first balcony. The other hall shows about 10 dB down but doesn't state where the sound was measured. Which leads to my last point. One of the big differences in headphone sound vs live and evens peaker sound is the balance of direct vs reverberant sound. In halls, reverberant sound is quite prominent. Even with speakers at normal distances (not near-field set-ups) there is still going to be a lot of reverberant sound. However, most phones shoot their sound right down the ear canal at the ear drum with virtualy no added reverberation. When you also factor in the prevelance of bright recordings, I believe we are getting a an excessively dry (i.e. unreverberant) and bright sound (i.e. too much highs) out of most phones. Probably this concern comes from spending so much of my listening time with Stax Sigmas, which try to give something of the reverberant field. I am not suggesting they do this perfectly but they are listenable with a wide range of even badly recorded material . I think this is because they mount the drivers away and ahead of the ears and create a sort of faux reverberation in the earcups.

What was the effect of the driver swap alone? Did it give a Mk,1 or Mk2 sound? If you change both the port and the driver at the same time you can't say how much is due to one or the other?

.I am enjoying this thread a great deal. It is nice to see some real data on these phones as opposed to the normal, purely subjective assessment. Of course the interpretation of data then leads to debate as to how accurate the data collection is, how it was collected and what the data then mean to the listener which the ultimately gets you back to the subjective.. Good point. The discussion of square wave response may be premature if there are artifacts in the measurement system. I am not sure about the various waterfall graphs which have been posted here either, in part since I assume they must also be based on some sort of impulse signal which would presumably be subject to the same artifact noted above. I am have having some problem following some of this discussion as to what is an actual measured response, what is derived from existing data and what is some kind of hypthetical simulation. The Frequency response data seems interesting and uncontroversial. But I would mention some additional points of testing or discussion which it would be nice to see clarified.. First whether the measuring set-up is properly compensating for pinna and ear canal effects so as to measure "flatness." comparable to measurements of speakers. It is my understanding that the system does ini fact attempt to do this but exactly how I am not sure. Secondly there is the issue of repeatability. To what extent you are getting positioning effects such that the measured response could change with a slight tweaking of position of the phones i.e. if the same phone is measured at different times is the response going to look the same. There is the question of how repeatable the measurements are across other examples of the same model or whether there may not be individual differences between examples of the same model. One simple example could be that changes in stiffness and compression of ear pads could give different results. Then there is the possibility that the manufacturing process for phones does not give exactly the same result every time. Finally, could some-one give an explanation as to why the high frequency responses of many phones is so much less smooth than the lower and mid frequencies. Are the transducers this erratic or is this the result someting like cancellations from reflections within the ear cups? Of course these are issues that measurement can clarify and I hope that will happen here. On the subjective side, there is little doubt that a reasonably flat frequency response is desireable in a headphone simply because this indicates that the phone is neutral. However when you get up to the high frequency range you probably want some roll-off in part because there is a natural high frequency roll-off with distance from a sound source and most recordings are made with microphones closer to the source than one would normally hear. Plus there seems to be an awful lot of high-frequency equalizing boosting in recordings, especially rock-pop. It looks like most of the phones are in fact giving some high frequency roll-off. But this is a great thread and Tyll has provided some important new information to anyone with a serious interest in headphones.

Given that there appear to be changes in both the 007 and 009 during manufacture, It could be useful to have serial numbers of both phones.

Theer is a link on the Inner Fidelity page to an "007 Mk2", which I thought was the same as an 007A. http://www.stax.co.j...-brochure-s.pdf Possibly Tyll can clarify. There is a rather striking peak at the 9/10 kHz, which sounds like what I hear on my 007A. I am not sure if the Mk1 has similar peak since I haven't listened to it long enough.

No hum and I am using the SRD6 mains operated unit.The amp is not high-end, all I can say is that it is better than the previous one I had and gives very clean sound sound through both the phones and the small Spica speakers I use in the bedroom.

I am currently listening to some Hendrix "The Ultimate Experience" comparing the Sigma/404/717 vs low bias Sigma/SRD6/ Sherwood receiver. The transformer system does sound pretty good. Compared to the Sigma/404 it is somewhat rolled off in the treble, has less detail and a narrower soundstage, but it certainly gives a good overall presentation. At the risk of adding still more confusion to audio vocabulary I would say it gives a highly "coherent" presentation which just works. It is in no way an obsolete set-up. You are right John, I must try a high bias transformer for the Sigma/404.

Yes I have noticed a similar improvement of the frequency response of the low bias Sigma with an SRD6 transformer.

I see the ad in HF for the Sigma/404 is closed. It's not clear if they were sold or taken off the market. They had been marked down to $1325. The seller had a number of other things recently on the market, but not necessarily sold, including a BHSE amp. I looked up his early ad to buy a BHSE and it actually states "Willing to pay top dollar." So I assume he did. Considering that the Sigma/404 ad says the Sigma pro that was cannibalized to make the Sigma/404 cost $1250.00, that's a good deal for someone. But I can't see why the hurry to sell unless a cash infusion was needed. And it's only been a couple of weeks since they were made! I think I would have waited several weeks to see if they didn't grow on me, or kept the Sigma pro for several weeks to be sure that this was the general direction I wanted to go before turning them into a Sigma/404. My Sigma/404 has no serial number because the arc assembly was replaced by Yamas. My low bias Sigma, which I did not buy new is 00906 a pretty early one I would think. There may be a number on my pro but it's at work and I am home for the weekend. Its number would be for a low bias model, since that's what it was before it was rebuilt as a pro by Stax. I have never been too bothered by the mineral wool and I have not worried about replacing the inner mesh which is gone in all my models except the 404. The stuff in no. 906 is actually pretty soft. One of the odd things I find about amping both the Sigma pro and the Sigma/404 is that the SRM1Mk2 is all I feel I need to run them. The pro sits in my office with an A series SRM, the Sigma/404 sits in my living room with a B series SRM. The bigger and more powerful Stax 717 amp sits upstairs running the 007A. While I can hear the 717 giving the Sigma/404 improvements, mostly making it faster and crisper, it isn't that big a deal and I will happily put down my 717/007A and go downstairs and listen to the SRM1Mk2/Sigma/pro. I have the same DAC's for both although different cd transports The SRM's and Sigmas just have a good synergy even if not the last word in high-fi and even though the Sigmas are less efficient than the 007A. On the other hand, the 007A really needs the 717. It loses too much quality on the SRM1Mk2. Synergy among audio components is a pretty elusive concept. I guess it just means the combination of components you actually like to listen to most.

I have no trouble with people who disagree with my opinions about equipment as long they have actually had a proper chance to hear the items in question. I think comparisons made by persons with both items are the most reliable information you can get. What ear pads have you been using? I can't imagine that these phones would be sensitive to pad, although most other designs are. Your finding the Sigma pro as good or better than the Sigma/404 would certainly irk the guy on HF who dismantled a pro to turn it into a Sigma/404 at a cost of about $2,050.00! He also got an SR009 at the same time and immediately put the Sigma/404 up for sale. He says he doesn't like the sound of anything now except the 009. He should have listened to the pro when he had them to see if this was going to be his cup of tea. The sigma pro and Sigma/404 are more alike in sound than any other 2 phones you are going to find. Still, the 009 must be a pretty stiff competitor and he may also need some cash to cover the cost of the 009's. I made my Sigma/404 from my own low bias set which had a broken arc and cable. I had previously sent a broken low bias to Stax Japan to make what is now my Sigma pro. (They don't seem to do that any more. ) Thinking about repairing the second low bias unit, I thought, why not do a pro upgrade as well, and since the original pro parts were probably not available, just go for the 404 parts. The entire repair and parts cost about $600.00. However I also immediately picked up another Sigma low bias because I had none left. The guy only wanted $175.00, which is pretty cheap compared to current prices. But I could see that unlike, say the Lambdas ,they were going to get pretty scarce.

Glad to hear that you like the pro's. I have never understood the bad rap they have been getting. Some people even saying the low bias model is better. It seems as if the pro's really like your transformer set--up. Is there anything in which you find the Sigma/404 better? However, I find that used with my Stax 717 amp, it's a good phone but not as good as the Sigma/404. My results are almost the opposite of your's in that regard, the 404 has better definition, treble and bass. I had both phones set up in my 717 at the LA Canjam some years back and I didn't hear anyone say the pro was better. About the only comment I heard was that it had a more prominent midrange, which is similar to saying it has less bass and treble. But you are using a transformer, and these do tend to transform the sound. Certainly my experience with my low bias transformer and low bias Sigma is that the transformer gives better dynamics and a flatter frequency response than amps such as the SRM1Mk2, but that it loses detail.

What amp would that be? I really don't listen to the low bias Sigma much, preferring the pro and 404 variants. But when I listen to them with my late model SRA12 (which claimed to be improved and has a PS Audio Noise Harvester pluged in the back ) I am often surprised how good they still sound. And when I run them from the SRD6 transformer, their dynamics are improved even more and the frequency response seems flatter. Unfortunately, the transformer reduces ambience and detail. Sometimes I think they have a certain sweetness of sound that the high bias models lack. At any rate I have never been inclined to sell them or canibalize them to make another Sigma/404.

I'll let you draw your own conclusions first.

It's good to have both the Sigma Pro and Sigma/404. Do you still have a low bias model? I keep a Sigma Pro in my office and the Sigma/404 at home, each happily running off an SRM1Mk2. The 717 is a bit better with them but the older amps are still pretty decent. I will be curious to see what your impressions are. About 2 years ago at an headphone meeting in LA I had both hooked up to my 717. I did a comparison of all three some time back on a different site.

I would guess this depends on exactly what you propose to do by way of repairs. If the imbalance were due to something like the one stator contact being disconnected that would be a fairly easy fix. If the driver is seriously damaged, eg. holes in the driver membrane I don't think they are easy to rebuild. I once split the driver unit of a Sigma so that one stator came off completely. I glued the driver unit back together and amazingly it was nearly ok, and nearly balanced compared to the good driver. However, gradually it deteriorated and I finally sent the whole set to Stax Japan, back when you could still comunicate with them. They rebuilt the set as a Sigma pro. Re:007 headband. In order to get a good fit, I found myself bending the metal arc assembly a whole lot more than I initially felt comfortable doing in order to get a proper fit. But the whole structure seems very strong and well-made and can take a fair bit of manipulation. Of course one can question the design decisions that made such a balky set-up in the first place. However, I do like the fact that the structure is very rigid, i.e. the drivers are tightly fitted to the fames which in turn are tightly fitted to the arc assembly. There is no wiggle in the system. I would guess that this might have some sonic benefits even though it resulted in a set-up which is hard to adjust for many people's heads. The only residual problem I have with my 007A is that the top elastic is needing to be tightened again. This will make three such adjustments I have done.

I accept that these types of equipment need to warm up but I don't like the sound of the amp when it has been sitting on for a long time. The sound seems to get thin, lacking in bass and have some slight rise in background noise. I prefer to short period of sitting, say 30 minutes and then a minute or so of playing louder than I would be listening.

That doesn't surprise me or change my opinion. Here's why. I was first clued to this issue when I replaced the old foam of my LNS. The foam was so old it became thin and crumbly and I don't think it had any impact on the sound. Your sigs would be even older than my LNS. I ordered new foam from the Stax dealer and these foams made the LNS phones sound terrible. It is certainly possible that the old foam was more acoustically transparent than the new foam or just became that way with age. I only caame to dislike foam when I put new foam, which was much thicker than the old stuff.

It's not and it does. I am not saying getting rid of the foam helps all Lambdas, but I prefer my 404 and LNS without it. Didn't you once report on the effects of different backings? I don't think I hallucinated this.

Do these phones have foam backing like the other Lambdas? I couldn't see any in the pictures.

Hair getting into the drivers is also a problem and is probably easier to see than dust.

Looks like either would do.

All I know is that I have been able to order a replacement pad for the Koss esp6/9 based on another Koss dynamic phone. Only cost about $6.00 and was a bit tight but I don't know the name. I would send Koss an e-mail.

Hello all, I have decided to shift over to this site after several years at the other main headphone site due to an inexplicable editorial shift there which appears to be directed at downgrading Stax listeners. After complaining a few times and getting nowhere I decided it was time to move on. Isn't the internet great or what? Re: the Koss ESP6 and 9's. I still like mine even with an 007A and some good Lambdas and Sigmas to play with. I have been trying in a very desultory fashion to run the ESP9 off a Stax amp. So far without success but when I get some time free I wil try again.