BTW, is there any audible diff between the HP-1 and YH-1? I know they're both technically similar(identical?), but I've got a YH-1 coming my way and if it were anything like a slightly bassier sintered HP-1 that'd make me VERY happy

I've had a few of each, and they're all within the same ballpark, maybe within the same infield. This is not to say that you won't find samples that vary widely from this [very small] "norm". So as we say here on HF, Go for it, you have nothing to lose but your money. Or something like that.

Sounds like a plan! Once I will have found my fav Yamie, I'll play around w/ acoustic deadening foam and acoustic damping clay...so far the sintered HP-1 is still on the very top of my list, though....Hopefully some of that foam could bring deeper bass w/o killing the holographic SS..then I'd be in heaven 
 
But yes, due to poor QA and/or drivers aging, you never really know what you're getting w/ those vintage Yamie's as it would appear 

And how good are those SFI's anyway(especially the 120 Ohm flavor)? I always see ppl having fun rehousing them, then they always end up in the classifieds after a little while ^^

Quote:

vid said:

 
When the sheet is 'up' (i.e. covering the upper portion of the driver), the frequency response develops a notch around 6500 Hz, the 9000 Hz hump is more or less unaffected, but the overall sound (listening to music) has more bass – I quite like the way this sounds. When the sheet is 'left' (I think this translates to the portion of the outer blade of the ear), the overall sound is notably muffled and the 9000 Hz hump is slightly reduced. 'Right' produces a sound that's perhaps more or less equal to 'up' (these two orientations I didn't test against each other, but in any case 'right' produced a less muffled sound than 'left', which I did compare directly). 'Bottom', again, muffled the sound, but also completely got rid of the 9000 Hz hump, and in fact pretty much smoothed out all the upper frequencies north of that (but, again, the overall sound was muffled). I'll do some more experiments with different materials and thicknesses.

Click to expand...

 
I did some frequency measurements on these different orientations. The recording setup I have models the ear canal resonances (mainly ~3 kHz and ~10 kHz in this case – I think the 9000 Hz hump I talked about is the latter resonance). It doesn't model the rest of the ear, but considering the HOKs are on-ear, I'm guessing we're only missing the concha and some of the lower flaps. In any case, the graphs below give some indication of the effect of the paper thing in regards to how it affects ear canal resonances, but do not indicate exactly how the phones sound above 3 kHz.
 
Also, the measurements are contaminated by ambient noise below 40 Hz, although these graphs are pretty noisy up until 100 Hz, which is something I haven't noted in my earlier measurements of other phones. Could be the time of day, i.e. noon.
 

 
In the above graph, the violet line represents having the paper aligned in the 'up/right' position, i.e. at a 45-degree angle between up and right (see the post I'm quoting for some pictures of the paper setup if you wish); the green line has the paper placed over the bottom part and the blue line has the paper left.
 

 
In the second graph (the program I'm using only lets you plot three simultaneous graphs, so I had to break it into two), everything else is the same as in the previous one, except that blue line now represents having no paper between the driver and the ear.
 
In my above post, I noted that the left and bottom positions both muffle the sound, and in the first graph it can be seen that they both produce a roughly equal graph. I'm not sure if these graphs show what causes me to perceive the muffling of the sound. I'm guessing that having the paper left would cover the concha, and having it bottom would cover whatever those flaps at the bottom are called (anti-tragus?). Maybe covering these would result in muffling? In any case, those parts weren't modeled in my recording setup, so any effects on them would not show up.
 
It's a bit curious that I heard the 9 kHz peak as having been eliminated by having the paper at the bottom, but in the graph it's not quite so. Possibly to do with the other parts of the outer ear, I've no idea.
 
In a later post I noted that having the paper up/right produced a clearer sound, and in the graphs it seems that it produces a slightly more even response. I also felt that that position increased the bass a bit, and in both graphs it did produce (very, very slighty) a little bit more bass – but it could be a coincidence.
 
These graphs are by no means accurate, but I suppose they could serve some purpose of curiosity.
 
As a bonus, this is the impulse response – these measurements should be somewhat reliable:

 
I also recorded the 300 Hz square wave response (paper is up/right):

 
Not terribly impressive. (My sw measurements seem to be slightly indicative of the fact, not totally correct. For instance they introduce tiny hills that aren't a part of the headphones' response. Take them with rough-grained sea salt.)

Whoa! If you lived here in the US, I'd strongly suggest sending the HOK to Tyll Hertsens for corroborating measurements. The square wave actually doesn't look that bad-- there's some resonant bounce (the hills) which also shows up in the impulse response graph, but the tops are straightish if not flat, and all the tilt indicates is lousy bass response, which we already know the HOK has. The tiltier the tops are, the lousier the bass. In fact, lousy bass is what all the graphs are screaming. Getting more diagnostic detail from them might be problematic, as you know, but as a rough correlation with what you're hearing, it looks promising to me. 
 
Have you, by any chance, a 1/3rd-octave graphic equalizer?

There were 2 different thicknesses of dense damping foam discs used in Fostex's vintage T20v1, v2 and T10 models, along with a very light weight foam disc. 
 
Does anyone know which went with which? 
 
I know the thick dense foam disc came from the T20v2, and I'm guessing the thinner dense disc was T20v1 and the very light damping disc was T10.  But I'm not sure about those. 
 
 

Quote:

wualta said:

 
Have you, by any chance, a 1/3rd-octave graphic equalizer?

Click to expand...

 
I'd love to send them to Tyll, but the shipping would be waaaaay too much for me right now – small population, high postal rates.
 
Any recommendations for a good 1/3 EQ? I took off to Google and downloaded the first free 1/3 EQ I found, but apparently it may not be as good as one might want. What sort of equalizing did you have in mind?
 
I used the equalizer I downloaded to come up with this configuration:

 
Apparently it's your average smiley EQ, but I found out by accident while I was boosting the bass (which is what I assume you wanted me to do) that giving the treble a hump as well made the HOKs sound reasonably good, though a bit too bright I think.
 
This is the freq response for that EQ (and why I might need a different equalizer):

 
I don't know what's up with the noise at the very low end... Could just be the HOK, you know... (I'll mention this again just in case, for those who are uncertain: the response above is raw, so to get an approximation of what's really there, subtract in your mind this from the graph.)
 
This is the square wave for that:

 
There's a point where upping the bass just makes it sound flabby. The bass boost I have in that EQ doesn't quite go that far yet, and as I said, it sounds reasonably good. Should I push the bass more, or what EQ did you have in mind?

Quote:

rhythmdevils said:

There were 2 different thicknesses of dense damping foam discs used in Fostex's vintage T20v1, v2 and T10 models, along with a very light weight foam disc. 
 
Does anyone know which went with which? 
 
I know the thick dense foam disc came from the T20v2, and I'm guessing the thinner dense disc was T20v1 and the very light damping disc was T10.  But I'm not sure about those. 
 
 

Click to expand...

 
The T10 has the glass fibre disc and a thin foam disc, honest truth I don't recall the T20v1 -  thought it was same/similar to T10 and as you say the T20v2 has that thick foam disc..dB
 
ps cool measurements and experimenting vid 

 
Quote:

vid said:

 
1 ) I'd love to send them (and the K 250) to Tyll, but the shipping would be waaaaay too much for me right now.
 
2 ) Any recommendations for a good 1/3 EQ?  
 
3 ) What sort of equalizing did you have in mind?
 
4 ) There's a point where upping the bass just makes it sound flabby. The bass boost I have in that EQ doesn't quite go that far yet, and as I said, it sounds reasonably good. Should I push the bass more?

Click to expand...

Yes, Tyll is explicit about not accepting stuff from overseas, which is of course understandable but too bad, because there are a lot of Grundig 224s I'd like to see tested, if you know what I mean.
 
Behringer. They're surprisingly affordable here in the US. Where you are, who knows.
 
Primarily, taking that huuuge treble shelf back down to midrange level. That will make what bass there is seem much more. I'm not sure if you're saying in your post that you've already done that.
 
Flabby? That's not a good sign. Generally it means you've uncovered a resonance (but check for signs of mechanical or amplifier stress). You can push the bass, because the drivers will take a lot of punishment, but there's no point in merely feeding the resonance.
 
 

Hmmm maybe my pair of T10 were not completely stock as they had only foam.  But if the T10 has the thin, light foam (almost acoustically transparent) then it must be the T20v1 that has the thin dense foam (same as v2 except thinner)

Oh, so he wouldn't even take them in... Didn't know that. Can't blame him, though, damn ocean and all. I'll measure all the Grundigs that come my way, although I advice against anyone actually sending me theirs.
 
I was empowered when you said the HOKs can take the bass! I interpreted the flabby bass as being due to the driver desperately hitting against the magnets and hurting itself (I really did).
 
The thing with the treble hump is – it works. It's a bit too big of a hump now, sure, and I could bring it down a few dB, but if I get rid of it (and keep the extra bass), the phones sound dark. The treble isn't half as bad as the (raw) graph suggests. The sound is a tad trebly, but not by much. – But of course I'll have a third listen tomorrow, my ears could be tricking me.
 
What happened was that I was testing the bass boost on a different (low-quality) equalizer, then for some reason (and unknown to me) the equalizer on foobar was activated, and it had some crazy default treble boost setting loaded. I put the phones on my head and thought I had the wrong ones, because they sounded really good.
 
It's pretty late at night, and I didn't realize to eliminate the treble boost for this test (just lowered it a little), but I did punch up the bass some more for a last quick test for today. (Yeah, I went over the 0 dB line.)

 

(I don't have time to censor the <40 Hz area, but basically what's there is semi-random noise. I've highpassed the test signal and the recording at 40 Hz due to background noise, so pay no attention to those frequencies.)
 

 
I did some quick listening tests, and the bass didn't seem flabby yet. I don't actually like the amount of bass at this point, but it's done for the sake of experimenting.

Yes, the HOKs can take it. They look fragile and pathetic when they wash up on your doorstep, but they will man up and take bass torture with grace. I'd still recommend anyone thinking of buying an HOK get the model 2, which has noticeably better ability in this part of the spectrum. There's another reason: both HOKs are so inefficient that they can suck an otherwise capable headphone jack dry and send the amp into clipping when bass boost is applied. Better to have the model that gives more bass back before that clipping point is reached. This advice applies to the 'phones in stock form-- once all the many leaks are sealed up (or a transplant is done), who knows?
 
I call the shelving above 2k the "klarheit" effect, aka the Sennheiser MD 421 Effect. I recognize it as a viable response curve, useful for many things, though not, for me, long-term listening. For a pro-audio 'phone, though, it's perfect. I wonder if these drivers are too big to be transplanted into something like a Fostex T20 v1 or v2. They certainly seem to cry out for liberation.

Hey, the HOKs don't look pathetic! They're working class rugged, looking as they sound.
 
A transplant would be nice to see, though it won't be done by meh (h added to avoid silly rhyming).
 
I trust your more experienced ear when it comes to the treble hump – or klarheit – in long-time use. (Do I sense contempt in that post towards klarheit?) I've taken a few moments to slightly tone down my own treble hump.
 
I looked up the response curve of the MD 421 – it looks just like the Terhardt outer ear curve. Any connection?
 
Because the raw measurements were up-playing the treble hump in the graphs, I dug up my blu-tack recording ear (see this post for pictures etc., and measurements for context) so that I could apply an HRTF curve and thus maybe have the graphs better reflect what I hear.
 



 
Each graph shows two lines: violet for the un-HRTF compensated curve recorded with the ear + ear canal; and green for the HRTF (diffuse field) compensated curve.
 
The top-most graph duo uses this modified treble (and bass) hump EQ:

(I perceive a valley around 6 kHz, so that's why it's punched up.)
 
The second set of graphs uses this bass hump with no treble hump added:

(Forgot to adjust the trim setting to match the one above – sorry!)
 
The third and final graph image is the HOK without any added EQ at all.
 
Here are all the HRTF compensated graphs from above lined up for comparison:

 
(Again, pay no attention to anything below 40 Hz; the recording was highpassed there. Semi-random noise. I believe the wavy line in the middle of the graphs is due to the equalizer, since it doesn't show up if the EQ is disabled [blue line].)
 
I don't claim that the blu-tack ear gives accurate results, but it seems to indicate a better-matching graph (to what I hear) than simply taking measurements with the ear canal alone, as I did in the earlier graphs I posted.
 
I did a listening test on the non-EQ'd HOKs with a sine sweeper, and the 'no EQ' graph is reasonably well matched to what I heard. I can't hear the hump between 4 and 7 kHz – and in fact I hear a valley around 6 kHz, but the positions of the 3 kHz and 10 kHz peaks and their intensities are roughly matched, as is the drop-off after the latter peak, as is the low end from about 500 Hz upwards (didn't test below that).
 
The HOK with no EQ sounds dark, which I believe is reflected somewhat by the blue line. The HOK with just the bass boost also sounds dark, which is definitely indicated by the green line. The HOK with bass + treble boost sounds trebly-ish, but not much, which I believe is somewhat indicated by the graph if you ignore the 4-7 kHz hump. Although if someone disagrees with my interpretations of these graphs, please let me know! It'd help me interpret future measurements.

     Quote:

vid said:

1 ) Hey, the HOKs don't look pathetic! They're working class rugged, looking as they sound.
 
2 ) I trust your more experienced ear when it comes to the treble hump – or klarheit – in long-time use. (Do I sense contempt in that post towards klarheit?) I've taken a few moments to slightly tone down my own treble hump.
 
3 ) I looked up the response curve of the MD 421 – it looks just like the Terhardt outer ear curve. Any connection?

Click to expand...

1 ) Har!  Pathetic in the "poor little lost puppy" sense. When you open the box and see the exploded earpads, your first thought is "This headphone neeeds me!", and, well, you can't say it doesn't. I have a theory about this, which I will now dump on you.This feeling is a driving emotion which I believe partly underlies the motivation of the engineering mind. My father, a brilliant mechanical engineer, would regularly bring home pathetic appliances, radios and the like, because, I am certain, he could tell, almost by a sixth sense, that they were badly made, poor things, wasn't their fault, and we would not kick them into the gutter, but would give them a loving home. He liked dogs, too.
 
2 ) If it's done nothing else, teh intarnet has done two things for us as humans: One, made it far too easy for millions of people to reach into the muckpool of their lives and spew random, unfocused contempt, and two, made it far more likely that normal people will sense contempt where none exists. Given the loud ostinato omnipresence of the first group, can we blame the second group for a little oversensitivity? No. Which is a very long way of saying, no, I don't hold frequency response curves in contempt. They're either useful or educational.
 
3 ) Terhardt's paper (if I've got the correct one) came out about 10 years after the 421 mic and the HD 414 headphone, so it most likely was influenced by ideas flying around Germany for many years. Whether specifically Sennheiser research/ideas, I don't know. You'll see that same basic shape in a lot of microphone curves.
 
Oh! Almost forgot-- You should, like, get in touch with Tyll (and wouldn't that make a great morning cable-TV show? In Touch-- with Tyll ) and, like, compare notes on Headphone Measurement comma Pitfalls Of. As long as you're measuring for you, you can establish a baseline and watch the 'phones change as you work on them. Over time you'll learn ways to control ambient noise and other distractions and increase your ability to get repeatable results... and then you can become the eastern headphone measurement guru to whom everyone sends their headphones. If you want to.