The vintage Ortho thread

Discussion in 'Headphones' started by gurubhai, Jun 24, 2016.

  1. Biodegraded

    Biodegraded Friend

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    Yamaha YH-2 modding: a noob’s progress (part 2 of 3)

    Measuring modded vs (almost) empty pairs
    The graph below shows the effects of removing much of the damping from the two modded pairs. Taking everything but the ~14mm patch of foam in the central metal insert from pair1 results in removal of the 7k peak, introduction of a trough-peak pair at 2-3k, and a high peak at 160 Hz with a sharp dropoff below (green vs black curves). Taking everything but the damplifier & butyl from pair2 – so the cup-edge vents remain sealed – results in a drop through the treble and around 1k and a peak at 130 Hz, again with a sharp drop below (blue vs grey).

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    The major difference between the two pairs after disemboweling is that the cup-edge vents on pair1 are now completely open, whereas on pair2 they remain completely sealed. That pair2’s 2k peak remains (though narrowed somewhat because of a new trough to the left of it) suggests that the lack of cup-edge venting might be responsible. This idea matches @Ishcabible ‘s results from drilling holes in the backs of the cups of a pair of otherwise lightly-modded HP-1s. The introduction of a trough in the same place to the emptied pair1 further suggests that at least some degree of baffling of these vents is desirable. It’s tempting to infer from these observations that ~2k is the resonant frequency of the rear chamber, even though the cup volumes are somewhat different (there’s quite a bit of butyl/damplifier in pair2, and HP-1 cups are bigger).

    The mid-bass peak introduced to both pairs is reminiscent of what happens when leaving rear central cup vents more open vs baffling or closing them in other headphone mods (e.g. T50RP, HD250), so is likely due to the pivot-hole-connected vents in the central insert being uncovered by damping removal. The poorly-damped stock pair2 configuration had a similar peak in the @Philimon measurements. The difference in peak position between the two pairs measured here could be driver-related, maybe different stiffness of or tension on the supposedly tensionless diaphragms; or related to other differences between the two (pair2 has the conical magnet holes, pair1’s are cylindrical).

    Differences in the treble could relate to the pads. Pair1’s pads are very soft and compress markedly more than pair2’s on my coupler (and my head). Pair1 also retains its small central foam dot, which is just big enough to cover the 4 innermost magnet holes – but in theory, this should give more treble, not less.

    It’s interesting to compare the impulse responses and decays of the modded vs undamped versions if only to reinforce that yes, damping of these drivers is really necessary. Here are impulses and CSDs corresponding with the curves in the FR graph above (left channels only for brevity). Pair1 first, then Pair2:

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    Compared to their modded counterparts, the impulse responses of the undamped pairs look pretty ragged and have low-amplitude oscillations that persist out to beyond 1 ms. The modded pair1 impulse is interesting, the second peak being almost as high as the first.

    The CSDs show obvious differences, the undamped versions having much longer decays below about 3k. For pair2 the difference in the 800-2000 Hz area is more than is apparent because the dip introduced to the FR of the undamped version there results in a lower ‘start line’ (SPL at t=0) for the decay surface. Changing the graphs’ vertical ranges shows that the SPL drops in the highs of the damped vs undamped versions mask slightly longer decays there too, but the contrasts are nowhere near as much as in the mids. In both versions of both pairs, there are no obvious ‘ortho walls’ anywhere.

    I listened only briefly to pair1 without damping, and FR changes aside, it had lost the speed and clarity which were appealing in the modded configuration. Here are more thorough summaries of the sorts of changes brought by damping, from wualta in the HF ortho thread (scroll down to his last couple of headings) and @Philimon later in the same.

    Effects of different damping elements
    Having made some inferences on how different parts of the cup influence the frequency response, it’d be interesting to try to establish which damping components are responsible for which changes. A series of experiments on pair1 allows for some speculations. On the graph below (lots of curves, enlarge it):

    Black is the dBel84 config (microfiber, black foam, arctic fleece; photo in the previous post)
    Blue is with the microfiber removed
    Green is with microfiber removed and black foam switched for a 40 mm diameter, 8 mm thick cosmetic foam pad with ¼” holes over 2 of the centre-insert vents
    Purple is as green but with a hole over 1 centre vent
    Tan is as purple but with a solid cosmetic foam (no holes)
    Red is as green but with the microfiber returned
    The small patch of black foam in the centre-insert bowl and the 'Arctic fleece' cup fill remain in place for all. The red measurement (first in the series) was made with SPL = 90 dB @ 1 kHz and the volume knob was not changed for the rest, so the absolute changes of each configuration are illustrated.

    [​IMG]

    What I infer from these results is:
    • Blue vs black shows the microfiber mainly suppresses the lows & lower mids, the effect diminishing to zero around 3k.
    • Blue vs green and vs the undamped (‘empty’) curve in the first graph in this post suggests it’s the black foam that’s largely responsible for the upper mid dip and 7k peak. Red vs the others suggests the microfiber contributes here too.
    • The differences among green, purple and tan (same foam with different #s of holes over the central vents) suggest that variable damping of this part of the driver (the second set of driver holes counting out from the centre) and/or variable venting to the pivot exit influences the lower treble (less with less damping) as well as the bass & lower mids (more with more venting).
    I was surprised by the magnitude of the effect of the thin microfiber. I didn't at first believe it would reduce the lows so much (red vs green) so I tested the same config on the other side, being careful to ensure I'd got the holes in the foam pad lined up properly with the cup vents. The result was the same.

    While these results show the effects of different materials and seem consistent with variable central venting influencing bass, it’s not as clear how they bear on @dBel84 ‘s ‘differential damping’ strategy. Damping more holes in the inner – but not innermost – part of the driver does seem to boost the lower treble, but the results aren’t consistent: green (2 holes in the foam) is lowest, but purple & tan (1 & no holes, respectively) aren’t significantly different. More about that in the next post.
     
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  2. Biodegraded

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    Yamaha YH-2 modding: a noob’s progress (part 3 of 3)

    Biodegraded mods: many trials, many errors
    As I said in the first post, my approach to applying my own mods to these wasn’t very scientific but rather a series of random experiments to see what would work and what wouldn’t (undirected empiricism, if you like; equivalent to the “poke it and see what it does” approach in zoology). Looking back, though, I think some conclusions can be made about general principles.

    There were many more trials than I’ll show here, but I want to try to focus on the most informative ones. Most trials on this pair got listening time, some quite a bit. Although I had a general FR target in mind, I wanted to see what sounded best in the context of these ‘phones strengths: bass-light but speedy and clear in the mids. I wanted to avoid doing anything permanent like drilling holes in the cups as is done with reportedly great success by @rhythmdevils and others. Doing that would likely improve on my currently ‘final’ results but I’m only keeping 1 pair of these so there’s limited room for error, and I wanted to be able to reverse everything to leave myself free to try something completely different in future.

    The main problem with these things, as everybody(?) who’s tried to improve them has found, is that damping to improve transient response, bring up the treble, and flatten the mid-bass peak can result in killing the bass completely. Hence I played around with the differential damping idea and with changes to the baffling of the central cup insert vents to try to strike a balance. On the graph below:

    Green is with each cup filled with 2 cotton makeup removal pads, 56 mm wide (made for YH-2s, they fill the entire cup right out to the circumferential vents) with 25 mm holes (just large enough to expose the central metal cup insert and its vents) and a 25 mm central disc of 8 mm cosmetic foam pad as used in the pair1 experiments
    Tan as green but with the centre foam disc replaced by a 34mm disc of thin open foam (like Senn front foam) and another of 1/16” thick Creatology synthetic craft felt (thicker but less dense than Phil’s red & blue felts), sandwiched between the 2 cotton pads
    Purple is as tan but with the 2 cotton pads replaced by 1 8 mm x 55 mm cosmetic foam pad with a 25 mm centre hole
    Red is as purple with the addition of a 46 mm disc of thin but dense pale blue felt (@Philimon ‘s, from the photo in the first post) over the back of the driver
    In all configurations, loosely-packed strips of cotton wool were placed over the cup-edge vent slits. The curves were shifted vertically to show the major similarities and differences; unfortunately these measurements were not taken in the same session and so do not have a common amp-gain reference.

    [​IMG]

    The dense, thick central foam disc in the green configuration covers ~40% of the active area of the driver – all but the outermost 16 of the 36 magnet holes. If the mid parts of the diaphragm are indeed responsible for most of the bass, replacing this thick dense foam with less dense material – the thin open foam and felt of tan & purple – could be expected to boost bass and lower mids and to a lesser extent treble (the outermost putative treble-producing area being unaffected by the damping change).

    These results seem partly consistent with this idea: certainly the bass and lower mids are elevated in the less-damped configurations; the changes above 10k between green and tan (purple treble has other complications that I’ll address shortly) are inconsistent and I doubt my measurements are entirely trustworthy at high frequencies anyway. The relative dip in the upper mids of tan & purple might represent a ‘crossover’ area where the tradeoff between less damping of the bass (or less baffling of the central vents) and less enhancement of the highs starts to suppress the upper mid frequencies in favour of the lower ones. From the similarity of the curve shapes between 3 & 4k it looks like the upper end of this area is just above 3k but without a common reference it’s hard to be sure.

    The purple measurement represents a change (vs tan) of increased damping from 25 mm out to the edge of the driver (cotton rings replaced with thick dense foam). Purple and tan have similar shapes through the bass & lower mids and aren’t far apart through the middle & upper mids, but purple has significantly more energy above ~6 kHz. This could reflect denser damping of the outer parts of the driver (the outermost 16 holes) encouraging treble frequencies there; but…

    The red curve shows the effect (vs purple) of introducing an additional layer of damping across the entire width of the driver. Its shape is pretty close to the green & tan curves from the highs down to ~3 kHz, and below that to the tan curve down to ~1 kHz; and below there it falls between green & tan as would be expected from its intermediate baffling/venting of the lower frequencies. Although it’s hard to be certain without an absolute reference SPL, the similarity through the highs in red’s shape to tan & green and its difference from purple (being lower) would seem to contradict the idea that increasing damping over the whole driver results in an absolute increase in the high frequencies.

    For the next set of experiments, which includes my (currently) final version, I abandoned the foam and used the cotton pads as the main elements. These have the advantage that 2 gives similar damping to 1 foam in a thinner package, in which different size holes can be cut and between or over which other material can be sandwiched or overlaid; and when in place, they fill the cups right to the edge so additional material to baffle the cup-edge vents is not required. On the graph below:

    Red is 3 cotton pads, the outer with a 36 mm hole (just fitting around the black plastic cup-insert retainer ring; see photo in post 1), the middle with a 25 mm hole, and the inner with no hole
    Orange is as red but with the middle cotton replaced by a 46 mm disc of the 1/16” synthetic felt used in the previous set
    Blue is as orange but with a 46 mm disc of 2-ply toilet paper with a 18 mm central hole in front of the driver (between driver and baffle)
    Green is as blue but the inner solid cotton has 4 1/4” holes with centres 19 mm from the middle (see the photo below the graph).

    [​IMG]

    [​IMG]

    The red configuration is similarly peaky through the uppermost mids as the previous set of trials, and finding myself sensitive there I wanted to flatten that area. The orange solution, replacing the middle 25 mm holed cotton with light felt – therefore slightly increasing the damping of the driver’s central 25 mm but decreasing it outside that – worked fairly well, but upper mids & highs were still a bit sharp.

    I’d tried front filtering before with tolerable results, but Don suggested this ‘lens’ approach with the TP with a hole in the middle. The hole is just big enough to expose the inner 8 holes in the driver magnet. Blue vs orange shows that inserting this dropped the area above ~5k by up to a couple of dB, and this did make an appreciable difference subjectively – perhaps not only because it reduced the high frequencies but maybe also because it blunted ridges in the upper mid decays. The CSDs below show the before & after differences in both channels, v11 being without the lens (orange curve above), v12 being with it (blue).

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    Version 12 became my stopping point for a while. Although being light in the bass and tipped up through the treble, it was speedy, clean but punchy in the mids, and resolving in the highs. Ultimately though, I kept wondering if I could get more bass without ruining everything else so I replaced the inner solid cotton pad with one with 4 holes, each hole being positioned over one centre-insert vent and being just big enough (1/4“ because I had a punch that size :p) to expose half of 2 ‘second row’ (ie mid-driver) holes in the back of the driver. The pad holes mean that in this version the centre vents are baffled only by the light synthetic felt. The green curve (v13; final for now) was the result. Here it is compared to the dBel84 and philmod8 versions, and to @purr1n ‘s V1 (different) coupler measurement of @rhythmdevils2011-modded YH-3s:

    [​IMG]

    It’s evident that this change brings back more lower mids and bass – mid-bass apparently, but remember I think my coupler might roll off too fast below ~120 Hz. Something I’ve recognized about myself is that tonality is more important to me than technicalities and even timbre (within limits) and this sort of downward slope from mid-bass onward is something that sounds right to me. By way of illustration, here are v12 & v13 with my measurement of a stock HD6XX (good pads), corrected for a B & K style -1 dB per octave ‘good room’ target so that a horizontal line would be a ‘flat’ response:

    [​IMG]

    There’s still an obvious upslope through the upper mids and into the treble, but these ‘phones seem to behave well there and the elevation highlights their strengths in transient speed and note separation. Yoofs might find the level above ~8k to be a bit much. Listening to sine sweeps, for me these are pretty even below the upper mids but give me a peak from ~2.5 to 3.5k (right where the FR shows a dip), and a climb from ~6k up to about the point where my ears give up (around 13k). I don’t detect the roughness in the treble that’s been spoken of, but that might be my old ears doing me a favour.

    Planar purists might not enjoy this version so much because it seems that some of the planar characteristics have been sacrificed. While bass is bigger (and seems to go deeper than indicated), it has more of a dynamic than a planar character, being rounder and punchier rather than ‘fast’ and tactile. The reason for this might come down to relatively high distortion inherent in these corrugated drivers, as alluded to by @dBel84 in the quote in post 1. Compared to my measurements of HD6XX I was surprised that the Yamaha bass distortion was markedly higher, especially in the higher orders. My distortion measurements are always pretty ugly so I haven’t posted any here, but can do if people are interested. CSDs show that the change from v12 to v13 has extended the decay times in the mids, and has sharpened the 3k ridge on the R side.

    [​IMG]

    [​IMG]

    While I like this result (so far), others might prefer to tune the bass somewhere between v12 and v13, which would be possible by having fewer or smaller vent holes in the outermost cotton pad (which would also clean up the midrange decays a bit). I might yet experiment with this.

    Summing up, what have I learned, and what might I do differently?
    • Yes, YH-2s need extra damping – but applied with some thought to cup design as well as driver design
    • In general, increasing damping density uniformly across the driver will linearize the frequency response but make it upward sloping: the denser the damping, the more the treble and the less the bass
    • The cup-edge vents should be baffled but not closed; closing them will likely give you a 2k peak, leaving them open maybe a 2k trough. Start with the stock felt baffling if you have it, then add or subtract to try to match the FR that evolves from your other modding
    • The vents in the central cup insert affect bass & lower mids, with maximum effect in the mid-bass; there’s a balance to be struck between exposing these enough to retain adequate bass and covering/damping the suprajacent driver holes so as not to screw up upper mids
    • A ‘differential damping’ approach involving heavy damping of the outermost and innermost sections of the driver and lighter treatment of the central section (second row of driver holes) might give an adequate level of bass; if bass needs increasing, remove some of the damping material above the centre-insert vents (make holes in one layer; start with small/few)
    • The drivers are very sensitive to small changes in damping. The cotton pads and felt used here have densities that aren’t always uniform, and while they worked for me in the end, some effort was required to get acceptable channel balance
    • Because different materials affect different frequency ranges, an approach using different materials and targeting different parts of the driver will give great flexibility – but also a large variety of potential results, so be prepared to do a lot of experimenting
    • Don’t be afraid of front filtering
    • While the increased thickness of damping materials vs stock will hold the drivers more firmly in the cups, it’s probably still a good idea to stick the drivers to the front baffles with appropriate caulking; I haven’t done this because I might not be finished modding yet
    • Space below intentionally left blank for readers to draw their own conclusions.
     
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    Last edited: Oct 30, 2022
  3. Biodegraded

    Biodegraded Friend

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    Yamaha YH-2 modding: bonus post

    Couldn’t resist a beauty shot (so of course not on my own head). One of the headband stays on Pair2 was broken so I replaced the stock band with a strip of brown belt leather (you can get imitations of the OG on ebay but I like the DIY solution); and the original cable was stiff and too long for desktop use so I substituted a shorter one, again in brown. So yeah, if it wasn’t already obvious – I’m keeping this pair, which will be referred to by me as the ‘brown noise’ version.

    [​IMG]
     
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  4. dBel84

    dBel84 Friend

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    This is just a mind boggling amount of data and work to get there, these are seriously fun headphones if anyone is thinking of scouring the usual spots to find a pair or 2 and now that the hard work of trying to figure out what works is done, there should be no stopping the fun.
    ..dB
     
  5. Philimon

    Philimon Friend

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    I was on break for awhile but I kept in touch. Ill add later some of my pm comments on these awesome posts by @takato14 and @Biodegraded . I dont have anything good to add to their informative posts but just my reactions. Appreciate that these guys took the time to write up these guides and impressions, @Vtory too for the Yamaha Compendium which I hope he will add a YHD1 chapter eventually… YHD series are pretty bad sounding stock due to decrepit earpads which are not simple to suitably replace but I know a vintage ortho ninja out there is helping already.

    Maybe I misread your post Bio but to be clear I didnt give takato my T30 or RP18. T30 I adore so would not abandon. The NAD had a bass imbalance so I offered tak to keep as parts but he refused and he offered to fix for free instead! So he is the truly generous one... It would take a long time to write out all the kind things every individual member here has done for me personally without any want or mention in return. Super!
     
  6. Philimon

    Philimon Friend

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    Related to vintage ortho and T50RP. Current T50RP is a relative, 3rd generation Fostex planar.
    T50RP mod kit sold by Fostex. Ive recorded some screen shots just in case the link gets disbanded by Fostex after the kit sells out.
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    Last edited: Nov 23, 2022 at 9:07 AM
  7. Biodegraded

    Biodegraded Friend

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    Looks like this is not so much a mod kit as a self-assembly kit to build a complete pair of headphones, as pictured in the first graphic - with drivers, cups, headband etc. included.

    Which fits with the price: at JPY 33,000 it's a bit more expensive than their price for a complete pair of T50RP3, JPY 31,900.

    Shame they're not selling just the foams & gaskets.
     
  8. dBel84

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    These look awfully similar to the mod developed for the drop version. Wonder if they just had some left over and came up with a clever way to market it.. dB
     
    • Agreed, ditto, +1 Agreed, ditto, +1 x 2
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