The ESP950 is indeed more neutral and that's why I always rank them above any Lambda. The bass is leaner but it also lacks the bass boom all Lambdas have.

Glad that God of Stats agreed with me. I think I'm practicing my writing and deduction skills in audio.......i said it and gonna said it again, 950+404LE = O2

Bit OOT but I was wondering is there any sonic difference between xlr and rca input on Headamp KGSS?

No sonic difference except the normal difference in the output levels of the two types. The RCA input is just the - side of the amp grounded so half the output level of the XLR input all things being equal.

Too lazy to do a final write-up but I tried undoing the seal by either slightly lifting the pads from the sides of my head or by opening my jaw and that causes some mad crazy mid-bass and the highs become more natural. The constant bass drone gets real boring real fast, though. Summary is still the same, rubbery sound, not enough treble, not airy enough, forgiving and fun for some, etc.

5th day I had it......same like Justin, nothing changes. One thing I notice that this headphone does a better job on male vocal than 950. But it could be my hearing

Thought I'd resurrect with a couple of observations. I had the good luck of buying a 404LE from Asr back in mid-2010. Needless to say that I'm now a huge fan of the Lambda design and think it makes a great companion phone to the O2.

However I always wondered whether there were any differences in the LE beyond the cosmetics/cables. That is to say I suspected that it was a gussied-up 404 with sound similarity way beyond the simple lambda heritage. Which is fine by me, since before hearing it I thought of the Lambdas as some of the ugliest phones around, made worse only by the shit brown. So a sleek black headphone with terrific comfort and fit as well as a sound to match came as a welcome surprise and in my mind were ample justification for the price differential.

A unique opportunity to test my suspicions came about after Tyll graciously offered to provide stat measurements. Luckily, a regular 404 was in the sample group. The measurements of my 404LE as well as the regular 404 may be found at:

http://www.innerfidelity.com/images/StaxSR404S2742.pdf

http://www.innerfidelity.com/images/StaxSR404LtdSSL0670.pdf

Here's an overlay of the two freq. response curves, with the 404LE in the darker orange and brown vs. the light outlines of the regular 404:

The curves are nearly identical, except perhaps for slightly smoother & less rocky upper treble on the 404LE and maybe a slight improvement over the already excellent channel matching.

Where I did find a difference, and where it turns out it really might matter, was looking at the effect the different pads had on the isolation measurement (404 in blue, 404LE in violet):

Now is it possible that aside from the recorded linear/nonlinear distortion of the response that there is some added effect of having an essentially flat, little to no isolation measurement in an open baffle headphone? Could that variation in the upper bass/lower midrange section of the measurement explain some of the recorded opinions of varying bass response among the Lambdas?

Aside from the minor discrepancy between the two channels recorded in the regular 404's 30hz response the rest of the measurements are almost identical. (At least I think it's safe to say that minor differences in HD at decently less than -40db may be dismissed.)

The impulse response also looks to be within a reasonable margin of variation between pairs of the same model, though it's tough to tell without those lovely CSD waterfall plots.

Again, even though I don't see substantial evidence of 404LE having any notable audible differences from the measurements, the foundational sound of this headphone has been superb. Maybe I've a tendency to prefer a slightly brighter signature because the 404LE sounds fairly neutral.

The response curves IMO aren't nearly identical. Take as a reference the flat line from 100 to 500Hz. On the 404 the response keeps increasing from there and get up to 15dB higher than that line at 3-4KHz. All the treble response is above that line. OTOH on the LE all the treble is under that line, as low as by 10dB and the only part of the treble leveling the response from the 100-500 baseline is at 8-10KHz and only by a few dB. That's far from the 10dB higher response at these frequencies the 404 have.

By looking the response curve I'd expect the 404 to be tending to bright, detailed, airy and with a good sense of soundstage. Depending on recordings, even sibilant. The 404-LE should be a bit darker yet still detailed, but not bright nor sibilant.

I must say I had a pair of 404 at home for a couple of months, hence I know their sound a bit, but never listened to the 404LE.

To me the 404's biggest failing was pronounced upper midrange emphasis which screwed up the tone and made it sound unnatural. It was also on the bright side. The FR graphs seem to support this. I haven't heard the 404LE but it does seem to be a lot less emphasized in the upper mids which would be a big improvement.

Nobody has said it sounds rubbery in this whole discussion. MPI is going to be very upset when he comes back.

^LOL

The response curves IMO aren't nearly identical. Take as a reference the flat line from 100 to 500Hz. On the 404 the response keeps increasing from there and get up to 15dB higher than that line at 3-4KHz. All the treble response is above that line. OTOH on the LE all the treble is under that line, as low as by 10dB and the only part of the treble leveling the response from the 100-500 baseline is at 8-10KHz and only by a few dB. That's far from the 10dB higher response at these frequencies the 404 have.

By looking the response curve I'd expect the 404 to be tending to bright, detailed, airy and with a good sense of soundstage. Depending on recordings, even sibilant. The 404-LE should be a bit darker yet still detailed, but not bright nor sibilant.

I must say I had a pair of 404 at home for a couple of months, hence I know their sound a bit, but never listened to the 404LE.

I think you're confusing the upper and lower freq. graphs for the different colored ones. This is partly my fault as the faded 404 freq. response lines are pretty tough to see.

Here's a better side by side:

There are minor variations below 30hz and larger ones beyond 10khz, though variations that high in frequency shouldn't be that noticeable. My guess is that the >10khz variations, especially in the case of the mismatched L&R responses in the regular 404 driver, might manifest themselves as differences in soundstage / the amount of "air".

You're right, my fault entirely, I took the top graph on your first post as the 404LE's and the lower as the 404's. I didn't see each graph had both colors. My apologies Now I understand why you didn't see such clear differences hahaha

I'd say the different between SR-404 and 404LE is the same as with the former and SR-SC1, subtle and mostly just that midrange etch that is under control. Now it has to be said that not all 404's suffer from this peak (my set doesn't) so the same could be going on here. Earpads also matter and the 404 has had 3 different versions.

Yeah, I made that mistake too. I'm also not surprised that there's some variance among the 404s. Without the midrange problem the 404 would be a significantly better phone for sure.

The etch looks to be that 3db rise from 1 to 2 khz, then it's fairly smooth until the 10k hump. Or the etch could be a product of a sharp band in the impulse response. I'd love to know how to tell where that sort of thing comes from.

Listening to my 404LE, I do notice a tiny bit of extra "presence", however there's nothing overtly offensive otherwise.

Note to self: use "rubbery" in review soon.

Nobody has said it sounds rubbery in this whole discussion. MPI is going to be very upset when he comes back.

Welcome back Justin.

Welcome back Justin. Your post seems a bit rubbery.

Welcome back Justin.

Welcome back Justin. Your post seems a bit rubbery.

I love you guys. I would also like you to know that I am somewhat slightly very drunk right now.