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  1. Otto Motor
    Sony MH755 Review – Testing Another Hype
    Written by Otto Motor
    Published Jul 27, 2019
    5.0/5,
    Pros - Tonal balance and accuracy; value.
    Cons - Useless cable.
    intro-800x445.jpeg

    This review was originally posted at https://audioreviews.org


    CATCHING THE HYPE TRAIN


    This $5-8 cheapo has caught the attentention of the earphone wizards after creating a hype earlier in 2019. Crinacle rates them highly: “Clean notes, proper sub-bass extension and a tonal balance beyond expectations.” Shotgunshane also added them to his list of favourites: “Yup, Seven dollars and 95 cents. Dynamic driver. Universal. Exaggerated Harman type frequency response with large sub bass boost, very clear upper mids and slightly easier going treble. Less warmth than [Sony] MH1/C. Once again Sony makes a budget gem and then screws us over with a J cable.” Antdroid also appreciates the Sonys: “The Sony freebie is exceptionally good for $6-8. It’s included free with their Bluetooth adapters, and a similar model, the MH750, is included with their cell phones. It’s a warm, bassy yet quite coherent in-ear that is quite a bit bassier and warmer than the Harman Target but has a similar upper-midrange and treble curve. It’s a steal for $6 on eBay.” Another qualified earphone guy, B9Scrambler, assigned the Sonys a small soundstage typical for the price range [original statement]. Co-blogger Biodegraded commented the bass was a bit strong for him (I have not heard him ever not say that). The question is: who is right and is the hype justified? The short answer: they are all right, each for their own reasons, and the hype (if there ever was one) is somewhat justified considering the low price and the small risk to lose money on something one doesn’t enjoy.


    NOTHING SPECIAL IN MY EARS?


    This is the MH755: single dynamic driver, small earpieces, cable too short (needs extension or recabling), haptic is nothing special. Got my pair from Biodegraded who had purchased them on ebay for $7 AUS.

    I put these Sonys first into my ears after a week with the $600 Sennheiser IE 500 PRO [review], which generated a jaw-dropping experience (I had expected the Sonys being slaughtered but the opposite was the case): outstanding tonal balance, clean, natural reproduction. Technicalities are also good: sufficiently wide soundstage with ok depth, good resolution, separation, imaging, layering. No, the Sonys are not better than the Senns, but they excel in the upper midrange: the upper winds and strings of a symphony orchestra are nicely reproduced whereas they are lacking in the better resolving, smoother Senns. Note: the Sony MH755 need quite a bit of juice…while it appears to be preposterous purchasing a dongle amp/dac for a $8 earphone, they work “louder” with my audioquest dragonfly.

    To me, the Sony MH755 are like the Toronto Raptors basketball team: every element is good, not much is individually brilliant but everything working together wins matches or even the championship: HOMOGENEITY (=balance) is the Sony’s strength…some may disagree because of the lifted low end. These are simply a delight to listen to for my ears and the main reason may be the tastefully executed upper midrange. Personally, I favour the Sony MH755 over most of my recently reviewed (and much much more expensive) iems, which once again shows that listening pleasure/quality and asking price are frequently not correlated (hence the expensive stuff often has to compensate with window dressing). And even if the MH755 were a bucket of crap in the opinion of others, they still did their job for me by creating pleasure. Isn’t that what we want? MORE JOY OF UNBOXING? Not needed at this price (it comes in a plain baggie).

    [​IMG]
    Frequency response measured by Biodegraded. Bass appears too boosted for what I hear.


    So why are all earphone guys mentioned above right imo? It depends where you are coming from. If you listen to classical music, the Sonys will excel by their tonal accuracy (“timbre”), their liveliness, and their homogeneity. If you listen to amplified music, the Sony’s benefits don’t play such a big role. As so often, it is in the eyes of the beerholder. The discussion also shows how much timbre can contribute to the listener’s satisfaction…but it is not mentioned at all in many reviews. Many (expensive) balanced armature earphones may not satisfy the listener in terms of timbre or harmonic distortion. As to soundstage: small or not? I find the soundstage being oval, quite wide rather than deep, with an ok height, but it appears to become smaller with decreasing volume. Add some juice and the soundstage is ok (for my ears).


    SMOOTH JOURNEY IN THE END


    Does the Chifi holy grail we all have been looking for come from Japan in the end? This is up to you to answer. I usually don’t give buying advice: “If you are in the market for a $xxx earphone, this is a no brainer because it punches above its weight…pull the trigger now” or similar sales blabla. But at $5-8 your biggest risk is getting a fake. Check the ratings of the ebay sellers.

    The Sony MH755: There is no reason to be euphoric about them but they certainly are a victory for the dollar-store audiophiles.


    P.S. I am lazy and “recabled” by adding a female-to-male audio cable for $2.99. Works.

    IMG_0388-1024x832.jpeg
      Viajero likes this.
  2. Ynot1
    Good bass and mids and highs are separated.
    Written by Ynot1
    Published Mar 31, 2019
    5.0/5,
    Pros - Clarity everywhere while with Bass
    Cons - Cable is Y and short.
    This is the best value iem on the market.
    I endorse, so it is said.
    The cost really disguises the performance of these.
    Granted everything man made seems to always gets better; and someday
    this too may become eclipsed in value by something better and cheaper.
    But life is just moment in time. Happiness is a state of mind. Few things
    can turn coal into diamonds, likewise few things can turn money into happiness.
    This is one.
  3. DocHoliday
    Re-Cabled MH755
    Written by DocHoliday
    Published Mar 7, 2019
    4.5/5,
    Pros - Timbre
    Balance
    Fatigue-free sound signature
    Cons - You could complain about the cheap plastic housings but you'd be nitpicking. The MH755 cost less than two frappaccinos at your local coffeehouse.
    20190227_122523-1 (0).jpg

    Full review to come but the MH755 is worth re-cabling. The MH755 follows the "Harman In-Ear target" frequency response curve very closely so most people will enjoy these. If you can get a legitimate pair of these at a reasonable price then don't hesitate to re-cable them. At the very least they'd be useful for comparison purposes with other IEMs you're considering purchasing.
      Viajero and DynamicEars like this.
  4. lllandline
    Why not five stars? Because let's be real.
    Written by lllandline
    Published Mar 1, 2019
    4.5/5,
    Pros - 1) Detail amount: just like it's supposd to be - it's just a headphones that work as they have to work: they don't lose details. That's it, there are no details to reveal, headphones can only fail to do what they have to do.
    2) Very comfortable. Small, beautiful (well, I just really like Sony design in everything), they disappear in you ears if you'll pick big enough tips.
    3) I don't care about the price, but srsly: I've bought two genuine pairs on ebay (don't try amazon, read reviews, you'll find that seller on eBay with no problems) for, like, 24$, including shipping to Russia.
    4) Overall tonal balance: first headphones that don't need an EQ.
    5) Bass isn't as deep or rumbly, but it's there, it's powerful, it doesn't bleed, sub-bass is deep and can create that basshead-ecstasy feeling.
    Cons - 1) VERY short cable.
    2) Overall sound is a bit simple, soundstage isn't that wide, layering isn't all that strong. Which is great if you want non-analytical, but music-listening experience, not to listen to disconnected parts of a track. Which is, of course, sometimes awesome, but it gets really old after several months.
    Tested them on Massive Attack tracks (why? because they have insane mixing quality with a lot of kinda quiet, background samples), on some black metal, on noise and power electronics albums - they don't fail in any of this genres.
    If you want to get really cinematic experience - tame the highs and lows thorugh an EQ, lift mids a bit. Wait for your brains to adapt.
  5. yuriv
    Cheap and good, but hard to buy
    Written by yuriv
    Published Dec 27, 2018
    4.0/5,
    Pros - Dirt cheap
    Frequency balance can sound very good
    Plays loud with low distortion
    Smooth response is easy to EQ
    Potential for mods
    Cons - Not easy to buy
    There are lots of fakes online
    Some samples can have too much bass
    Short J-style cable
    Long-term durability?
    Doesn’t come in purple or pink unless you buy the Bluetooth receiver
    [​IMG]

    “The correlation between price and sound quality is close to zero and, slightly negative: r = -.16 (i.e. spending more money gets you slightly worse sound on average).” Sean Olive was referring to the chart below when he wrote that in his blog:


    Let’s be fair here. They rate an IEM’s sound quality by how closely its frequency response follows their target curve. We also don’t know how they chose the models in the chart. They certainly don’t include the many, many kinds of $5 junk IEMs that you can buy at fashion discount stores like TJ Maxx and Marshalls, but we get what he’s trying to say. The subject of this review, the elusive Sony MH755, is sometimes the perfect embodiment of the idea.


    The bundled earphone
    You can’t drive to a store and buy the MH755 by itself. It’s the earphone that comes inside the box with the Sony MW600, SBH20, SBH50, and SBH52 Bluetooth receivers. Several eBay sellers sell replacement MH755 IEMs by themselves for $6 to $8 each. I have a strange love affair with bottom-of-the-barrel cheap IEMs, but I didn’t pay any special attention to the MH755 until I saw the measured performance at Speakerphone’s blog, ClarityFidelity.

    Last year, I was experimenting with mods for bassy and v-shaped IEMs by injecting resin into their rear volumes in order to reduce their bass. The process reminded me of the MH755’s smooth measured response. Its midrange and treble follow the diffuse field and Harman target curves closely. I was thinking to myself that all I had to do was reduce the compliance of its rear volume and I’d have the perfectly tuned IEM.

    Not long afterwards, I ordered three MH755 from eBay. The first thing I noticed was the short cable, which is designed to be used with a Bluetooth receiver like the SBH20. I use an extension cable with the MH755 when I’m not using it with one—a Radsone EarStudio ES100 in my case. The MH755 has a J-cord design, which means that the cable going to the right earpiece is longer than the one going the left. It’s supposed to go behind the neck on the way to the right ear. I sometimes find the arrangement annoying; I know it’s a deal breaker for some.


    What a cheap IEM can sound like
    I was surprised when I listened to them straight out of the wrapper. I didn’t hear the huge bass suggested by Speakerphone’s curves. Surely enough, my own measurements showed that my samples don’t have as much bass as the one measured at ClarityFidelity:

    Sony MH755 frequency response 3 pairs.png
    Frequency response of three MH755 from eBay​

    As you can see, my batch of three shows good consistency. I think they already sound very good without mods or EQ. The response at 200 Hz is only ˜1.5 dB up, relative to 1 kHz. At 100 Hz, it’s only 5 dB up. This kind of tuning is uncommon for an IEM that’s not trying to keep the bass flat, like an Etymotic.

    The sample that Speakerphone measured is bassier: +7.5 dB at 100 Hz. This boosted mid and upper bass makes the lower midrange sound thick and congested. In fact, the Harman target curve has a low point at around 200 Hz. Many IEMs sound clearer when equalized to decrease the response in this region.

    Sony MH755 sample 3 frequency response.png
    Sony MH755, frequency response
    Top: 2017 Harman In-Ear target compensated
    Bottom: Raw. 2017 Harman In-Ear target shown in gray​

    The MH755’s bass is a little elevated compared to the 2017 Harman In-Ear target. I prefer less bass than this, less than the target even, which is ok because the curve is just an average. The researchers who created the target prefer less bass themselves. On the MH755, it’s in the lowest octave where I especially feel the exaggerated weight, so I usually shelve the entire bass down with an EQ when it’s available. I still keep some of the bass above flat, but now it’s more in line with my calibrated home theater and two-channel stereo speaker systems (which have subwoofers that extend down to 20 Hz and 25 Hz, respectively).

    The MH755’s broad peak at 3 kHz is about 11-12 dB up from 1 kHz, close to Harman’s original 2013 target for headphones. Since then, the curve has evolved, and after some feedback from listening tests around the world, the latest versions of the around-ear and in-ear targets now have the peak ˜2 dB lower. This doesn’t sound like much, but it’s in the area where human hearing is most sensitive. A 2 dB adjustment at 3 kHz is noticeable.

    When I tested my own hearing, I discovered that the peak is centered at 3.3 kHz and that the resonance is very strong. An HD600 has a tall peak at 3.5 kHz that bothers some listeners, but it’s a good match for my hearing. Maybe that’s why the MH755’s 3k diffuse-field peak doesn’t bother me that much. It sounds close to what I’m hearing from my speakers. But I can imagine that, for some, the frequency response might give vocals an unwanted glare.

    The treble has a smooth response and is free of nasty resonances. I’m hearing a small (seemingly) low Q bump between 7 kHz and 8 kHz. It’s the ear canal's half-wavelength resonance, so its frequency depends on the distance to the eardrum. Speakerphone seems to have inserted the MH755 deeper into the coupler, so the bump is at 9 kHz instead in his measurement. That seems to help fill in the dip in the response above 10k. I can’t insert the MH755 that deep in my ear canal even with the small sleeves.

    To my ears, the overall balance is superb, and much better than many expensive headphones and IEMs. The MH755 doesn’t sound out of place in a comparison with well-known models that have stood the test of time.

    MH755, HD6xx, ER4PT 4.jpg
    MH755 with ER4PT and HD6xx (HD650)​

    Two of my three pairs have well-matched left and right channels, and the third is only off by 1-2 dB in parts of the treble. I hear a strong center image, especially with the first two pairs. Within its limitations, MH755’s stereo separation is satisfying and doesn’t call undue attention to itself. I’ve heard headphones and IEMs that play tricks with the phase to try to project a distinctive stereo image. But it’s like looking at shadows at the back of a cave instead of the real thing. It’s laughable when you compare them to a live performance, or even a good stereo or surround speaker system. I suppose it could sound pleasing if the trickery matches your personal HRTF. But it usually doesn’t work for everyone and the result often sounds like a cheap effect that negatively affects the tonality. The MH755 has none of that. It’s a simple minimum phase system.

    MH755 with NHTPro A20.jpg


    Comparisons
    I compared the MH755 to several other cheap IEMs. The local schools here have lost and found boxes, and they have lots of earphones because students lose them all the time. I got to measure several of them. Lost and found gives me an idea of what students are buying. There’s a lot of cheap Bluetooth buds, but I found two KZ IEMs among other Chi-fi models, so my guess is that they’re reading the buzz online. The rest are from my collection.

    TL;DR version: I like the sound of the MH755 better than the stock sound of any other cheap IEM that I’ve tried.
    All graphs: MH755 frequency response in light gray.

    Sony MDR-EX15AP, MH1, MH750.png
    Sony MH1 (green), MH750 (blue), and MDR-EX15AP (red)​

    The EX15 is the cheap Sony IEM that is sold in the local stores here. It sounds terrible. Maybe there’s a way to mod it to make it sound better. The well-known MH1 has way too much bass for my liking. It sounds good once you take care of the bass by equalizing or modifying the IEM. The two MH750 samples that I have also have too much bass. I don’t know if all MH750 are like this or it’s just my bad luck with these samples. More on this later.


    Panasonic RP-HJE120, TCM125, HJE125.png
    Panasonic RP-HJE120 (red), RP-TCM125 (green), RP-HJE125 (blue)​

    The Panasonic ErgoFit IEMs are very comfortable. They’re also top sellers on Amazon, with thousands of 4+ star ratings. I suppose they sound ok. The TCM125 is the headset version of the HJE125. The difference in the response is probably due variation in samples. I like the older HJE120 better. All of them improve a lot when equalized with a wide dip at 200 Hz. The MH755 still sounds better after that because of its smooth, mostly resonance-free treble and its extended response above 10 kHz.


    AKG Y20U, JBL E15, JBL Synchros E10.png
    AKG Y20U, JBL Synchros E10, JBL E15​

    You would think that these three Harman models would follow their own target curve. Nope: big bloated bass and two sharp resonances in the treble make for an ugly family resemblance. The Wirecutter used to recommend the AKG Y20U, which is, arguably, the worst sounding of these three. Maybe their sample is the good one. They’re now recommending the JBL Live 100 and T210. Perhaps the new models follow the Harman target more closely, but I’m not holding my breath.


    Skullcandy Jib, Inkd, Smokin Buds 2.png
    Skullcandy Jib (red), Ink’d (green), and Smokin’ Buds 2 (blue)​

    Not bad. The muddy Jib is the worst sounding one of the three. But when the bass is reduced via EQ or by sealing the rear volume, it becomes the best-sounding one. It still doesn’t have the high-frequency extension of the MH755. The Ink’d and Smokin’ Buds 2 might have the potential to sound really good after mods. I haven’t tried yet.


    JVC HA-FR6R, HA-FX7M, HA-FX32.png
    JVC Gumy Plus HA-FR6 (red), Gumy Plus HA-FX7M (green), Marshmallow HA-FX32 (blue)​

    All of these are current models, according to JVC’s official website. All of them are way more V-shaped than the MH755. I don’t know what happened to my measurement of the HA-FX8 Riptidz, which is also a current model, but it was nothing special anyway. The best of these is the newer Gumy Plus (HA-FX7M) but switching back to the MH755 from any of them gives instant relief.


    LG Quadbeat, Quadbeat 3 AKG, Quadbeat 4.png
    LG Quadbeat HSS-420 (red), Quadbeat 3 AKG (green), Quadbeat 4 (blue)​

    Overall, these Quadbeat models sound pretty good. All can play loud with very little distortion. The best-sounding one out of the box is the Quadbeat 3, which sounds closest to the MH755. The older HSS-420 sounds quite good when you flatten the treble peak at 5.5 kHz and cut the thick lower midrange with an EQ. It's perhaps my favorite after equalizing. Too bad about its silicone sleeves though, which don’t want to stay in my ears.


    Philips SHE3550, SHE3595, SHE3855, SHE3905, SHE8105.png
    Philips SHE3550 (red), SHE3595 (green), SHE3855 (blue), SHE3905 (orange), SHE8105 (cyan) frequency response​

    The Philips family sound: big bass, tall 3k peak, and then two more treble peaks after that. They can sound harsh, depending on what frequency the resonance lands. I like the bass response of the SHE3855 Chromz best. Unfortunately, its midrange has a coloration that I don’t like. Unlike the others, its peak is closer to 2 kHz instead of 3 kHz, and it makes vocals sound a bit shouty. I tested another unit, and its frequency response is basically the same.

    The SHE8105 sounds best out of the box, but still not as good as the MH755. It has less bass than the others and its resonances aren’t as sharp. The response is still a little v-shaped. It’s also harder to find at discount stores. I bought the only one I ever saw for $6. The SHE3905 Metalix is much more common. It also has almost as good treble extension as the 8105. Mods can make it sound very good. More on this later.


    KZ ED9, ATE, ES4, ED16, ZSN.png
    KZ ED9 (red), ATE (green), ES4 (blue), ED16 (orange), and ZSN (cyan) frequency response​

    Ok, one more comparison; Chi-fi this time. I chose KZ instead of Xiaomi, Brainwavz, Soundmagic, or HiFiMan. Except for the ED9, all of the ones measured here have the KZ house sound: Lots of midbass, which makes the lower treble somewhat thick, two bumps near 3 kHz, a steep drop in response above 4 kHz, with a valley that goes lower than the level at 1 kHz, then a really sharp spike between 7 kHz and 9 kHz.

    The midbass on the ATE and the ES4 are too much for me, even after trying all sorts of tips including wide bore. This boosted response pulls up the low midrange, making it sound thick. It’s better on the ED16 and ZSN, although I would have preferred even less, like on the Sony. Less low midrange gives country music a delightful twang, and the MH755’s steel guitars twang harder than any of the KZs. Equalizing this region down on the KZs improves their clarity. It makes Shawn Mendes sound less chesty, for example. In “Stitches” and “Treat You Better” he sounds more realistically whiny on the Sony, where his expression of angst and anguish is more palpable.

    The KZ response falls off steeply after 4 kHz, unlike on the MH755, where it decreases slowly. Dips are usually less offensive than peaks, but here, the KZs are a good 7 to 8 dB lower. Information in this frequency range is being withheld. Snare drums, for example have more snap on the Sony compared to any of the KZs (maybe its attack is slightly too sharp, compared to my speakers). The KZs sound relatively dull here.

    The sharp treble spike is the half-wave resonance, so its frequency depends on the insertion depth. In my measurements, the resonance is near 8 kHz. The ES4 and the ZSN, however, have large housings that prevent me from inserting them as deep inside my ears, so I hear the sharp peak near 7 kHz instead. It affects the timbre of cymbals and hi hats, which can sound spitty. On the MH755, it’s a gentler shimmer.

    A different insertion depth sometimes results in excessively sibilant vocals. The worst offender of the bunch is the ED16. On “Barbie Dreams”, for example, Nicki Minaj sounds like she’s hissing at you. It’s strangely fitting for a diss track because it arguably intensifies the contempt in her voice. It’s now dripping with disdain. But it’s not the intended effect. The Sony is much more forgiving when it comes to this because its peak is less intense; depending on the amount of damper, it’s just a small bump. Moving that small bump up and down the frequency axis doesn’t result in any range being overemphasized.

    KZ IEMS and MH755.jpeg
    The MH755 looks different. In this company, it sounds different too. From left to right: KZ ED16, KZ ZSN, Sony MH755, KZ ES4​

    I don’t know why KZ does this, but with four different models doing the same thing, it’s definitely a deliberate design choice. Are they trying to simulate the jagged frequency response that the pinna imparts on headphones and speakers, in an attempt to project some kind of stereo image? I don’t think it works for everyone, and it just messes up the tonality. I prefer the MH755’s smooth treble response, even if it’s a little elevated. It’s simple and unassuming and doesn’t try too hard. But that’s me. Your priorities could be different.


    MH755 with Dynaudio BM6 2.jpg


    Tuning the Response
    This section is about EQ and basic mods. It’s mostly about controlling the bass response. January 4 Update: added information on the effect of output tube dampers and foam tips. Enter if you’re interested.
    Using an equalizer

    [​IMG]
    Sony MH755 and Radsone EarStudio ES100 Bluetooth receiver​

    The MH755’s smooth frequency response makes it easy to apply EQ or crossfeed. For me, simply reducing the bass a little goes a long way. If the Harman target is what you want, a 10-band graphic equalizer can get the response close. Here’s what it looks like with the ES100’s equalizer:

    [​IMG]
    Frequency response with Radsone EarStudio ES100’s equalizer. 2017 Harman In-Ear target shown in gray​


    [​IMG]
    Radsone EarStudio ES100 equalizer settings for Sony MH755​

    A 10-band parametric equalizer for the ES100 is planned for a future firmware and app update, so this can get even closer to the target using fewer filters.

    Reducing the compliance of the rear volume
    If a system-wide equalizer isn’t available, the bass can be reduced by sealing the rear cavity. To do that, block the rear vent, cover the rear cup’s seam all the way around, and seal the bottom where the cable emerges from the rear cup and the strain relief. It can be done temporarily with putty like Blu-Tack.

    Sony MH755, where to seal.png
    Block the air flow at locations 1-4 to completely seal the rear volume.​

    Here’s how it affects the frequency response:

    Sony MH755 rear volume sealed (sample 3 R).png
    Effect of completely sealing the rear volume.​

    I like it. The drawback is that it increases the response between 200 Hz and 500 Hz. This mod doesn’t increase the amount of distortion by much:

    Sony MH755 harmonic distortion, rear volume sealed, 3 R.png
    Sony MH755 with sealed rear volume, harmonic distortion​

    Here’s what happens with a partial seal; keep open the part where the cord emerges from the strain relief (location 4 in the photo above):

    Sony MH755 rear volume partially sealed (sample 3 R).png
    Effect of partial seal.
    Top: 2017 Harman In-Ear target compensated
    Bottom: Raw. 2017 Harman In-Ear target in gray​

    Depending on how deeply the MH755 has been inserted, this can get the response within 2 dB of the In-Ear target between 30 Hz and 10 kHz. It’s not a huge change, and I would have preferred more bass cut, but it’s noticeable. I like the sound better than the stock MH755, but I’m not sure if I prefer it to the one with the complete seal. To me, it makes solo piano, acoustic bass, bass guitar, and kick drums sound more realistic. Your preferences might be different.

    I suppose, if even less bass is desired than possible with a complete seal, we could 1) play with the front vent, or 2) further limit the excursion of the diaphragm by increasing the stiffness of the air in the back volume even more. That could us into the realm of non-reversible mods, e.g., injecting resin in the rear cavity.

    Update: January 28, 2019: You can reduce the rear volume via reversible mode: See this post: https://www.head-fi.org/threads/sound-science-approach-to-modding-headphones.694963/page-4#post-14744462


    The effect of dampers in front of the output tube
    The response between 1 kHz and 7 kHz can be controlled by the use of dampers in front of the output tube. Here’s the effect of earbud foam inside the silicone sleeve, in front of the output tube:

    Sony MH755, effect of foam dampers in front of output tube.png
    Gray: stock Sony MH755
    Red: less earbud foam
    Green: more earbud foam​

    The damper reduces the height of the main peak near 3 kHz and shifts the peak frequency a little higher. It seems to have the most cut around 6 kHz. If you don’t like how the MH755 follows the 2017 Harman IE Target around here, you could use some foam damper. The drawbacks are that it exposes the half-wave resonance more—it was a small nub, but it can grow to a small peak that’s 3-4 dB higher, depending on the amount of damper material. Even a little bit seems to kill the resonance around 14 kHz. Added damping reduces the “air”, which some listeners can still hear clearly, especially those who are younger.

    The added damper also makes the graph look closer to the one for the MH1 and one channel of my second sample of MH755, where the 7-8 kHz peak stick out more. It suggests that they have more damping. Perhaps their response can be tuned the other way around by reducing the amount of damper inside the output tube.

    I haven’t played with other damper materials like microfiber cloth or tea bags, with or without pinholes. The dampers can be combined with a rear volume seal to make the response less v-shaped:

    Sony MH755, damper + complete rear volume seal.png
    Gray: stock Sony MH755
    Red: added earbud foam damper + rear volume seal​

    Maybe this example has too much added damping. Adjust the amount of damper and seal to taste. As always, YMMV.

    Starting experiments with foam tips
    Here’s what the response looks like with a Comply Sport Pro with Smart Core tip:

    Sony MH755 with Comply Sport Pro with Smart Core tip.png
    Gray: stock Sony MH755 medium silicone tip.
    Red: response with Comply Sport Pro with Smart Core tip​

    As expected, Comply foam effectively damps the ear canal’s half-wavelength resonance, so there is no peak near 8 kHz. The big drawback is that it kills the response in the top octave while introducing a peak near 4.5 kHz.

    I’ll see if a Sony EP-TC50 replacement sleeve can be made to work with the MH755. It’s the ear sleeve used by the XBA-N3AP. It’s a bit different from Comply foam, but also works as a damper.


    Fakes are out there!
    Last year I took a risk and ordered three MH755 from an unknown eBay seller. I was lucky to get a good batch. A few months later, I decided to order two MH750, which have microphones and longer cables. I was hoping to get the same performance as the MH755. The seller had the words "100% Brand New OEM and Grade A Quality, NOT Generic, NOT Fake, NOT Replacement" in the page’s item description. Look what I got:

    Fake Sony MH750 2 pairs.png
    Fake MH750 frequency response?​

    As you can imagine, they sounded horrible. I showed the seller this graph and one from the MH755 and explained to him that I was returning the products because they're obviously malfunctioning. It’s possible that these sellers don’t know any better if they’re selling a genuine item or a fake. Who knows where they’re getting their wares? They could have several suppliers themselves.

    I don’t remember where, but a few years ago, I read that Sony changed the guts of the MH750 while keeping the exterior the same. The only visible difference is the white filter at the end of the nozzle on the older models instead of a black one. Perhaps I got two original MH750 instead of fakes. I should have taken a photo of the ones I returned.

    Update: January 12, 2019
    aspire5550 has some excellent information on how to spot fakes: See this post and the next one: https://www.head-fi.org/threads/chi...hones-and-iems.820747/page-1412#post-14705306


    MH755 vs MH750
    I ordered two MH750 from an Amazon seller after returning the bad ones from eBay. This time, I’m convinced that I have the real deal, but I’m unhappy with their boosted bass:

    Sony MH750 frequency response.png
    Sony MH750, frequency response​

    After rereading this post by Sead Smailagic, the designer of these MH-series IEMs, it seems that the typical MH750 has a bass response that’s 7.5 dB up, relative to 1 kHz.


    This response is similar to the one on the MH755 measured by Speakerphone. On my MH750, the bass boost is closer to +9 dB. On one of them, the left earpiece makes a crinkling sound during insertion—a sign that the driver is bottoming out. My MH750 must not be properly vented in the front. Perhaps the bass can be decreased by restoring the front vent, if I can find it.

    I prefer the sound that I’m getting from my three MH755 and their much more controlled bass. What’s not certain is if my samples are atypical and that most units measure like the one at ClarityFidelity, or worse yet, my MH750. That would be disappointing.

    Update: January 28, 2019 I modded the MH750 and decreased the bass more than what's possible with a simple rear volume seal. See this post (scroll to the middle): https://www.head-fi.org/threads/sou...odding-headphones.694963/page-4#post-14744462

    Low-cost and low-risk alternatives to the MH755
    There are many inexpensive IEMs that follow a different target curve, and they have their many fans. But I don’t know anything dirt cheap that sounds like an MH755 out of the box, especially a good one with less bass. My problem with the MH755 is the risk of getting a fake when you order online. Even if you get a genuine unit, you still might get a sample with an obscene amount of bass. What are the alternatives?

    The MH750 and MH755 are cheap enough that many enthusiasts can afford to gamble a little bit and order online anyway. If you get a bassy sample, maybe it can be fixed with a simple mod. Buying other IEMs from local discount stores is less risky, and If you’re willing to tinker a little bit, you might be able to might get one of the clearance bin cheapies to sound close.

    The graph shown below is what I got last year with the Philips SHE3905 (aka Philips Metalix). I wrote about the experience in this thread: https://www.head-fi.org/threads/sou...odding-headphones.694963/page-3#post-13921453.

    Philips SHE3905 with reversible mods 2.png
    Reversibly-modded Philips SHE3905 headset, frequency response
    Top: 2017 Harman In-Ear target compensated
    Bottom: Raw. Sony MH755 frequency response in light blue/red.
    The resulting frequency response closely follows the Sony’s between 100 Hz and 9 kHz. It sounds similar too. The response between 200 Hz and 400 Hz is a tiny bit higher, but the Sony does that too when fully sealed. I have the bass where I like it. If you want more, don’t seal the rear volume.

    It has a few advantages over the MH755: I sometimes like its stronger response between 9 kHz and 12 kHz. It also has a microphone and a longer Y-style cable. The disadvantage is that you have to use a foam tip. And you have to experiment. This is where having a measurement rig helps to shorten the listen-modify cycle time. But I think it sounds lovely, and that the result is worth the effort.

    Philips SHE3905 x 3.jpg
    The crude Philips SHE3905 can be polished and refined​


    Update: January 28, 2019
    The Philips SHE8105 is another good one. See this post: https://www.head-fi.org/threads/sou...odding-headphones.694963/page-4#post-14744462
    [​IMG]

    If there are other cheapie IEMs out there that have good potential, I’d like to know about them, their measurements, and how they were hot-rodded.


    Outro
    Sony’s MH series of IEMs has been around for a while. They came out before the first Harman target was published in 2013. But somehow, with the MH755, Sony came up with a smooth frequency response that closely follows Harman’s latest crowd-pleasing target. (That is, if you consider a sample with less bass.) The performance doesn’t end there. It plays loud with low distortion, and it doesn’t suffer from a compressed dynamic range when playing back at high volume.

    The Sony MH755 shows what’s possible from a dirt-cheap IEM. It puts to shame many, many products that cost several times its price. Why don’t manufacturers, including Sony, make IEMs like this easily available? I mean, look at the kinds of things that are being hyped as the best low-cost IEM:

    Massdrop Hifiman Bolt.png
    Massdrop HiFiMan Bolt frequency response​

    It sounds worse than the cheapo IEMs from Panasonic, Philips, and Skullcandy. Maybe we should ask Massdrop and Sony to reissue the MH750/MH755, but with a few changes: less sample variation, longer Y-style cable with mic, and more colors available—all of this while keeping the price low. Call it the MH75x or something like that. If a cheap IEM with the performance of an MH755 ever becomes popular, it will become a benchmark, a well-known reference used to compare to other products. It will be easier to call out the many pretenders out there and force manufacturers to step up.
      Viajero, djray, castleofargh and 20 others like this.
    1. View previous replies...
    2. yuriv
      @oluv Lol. Soon after I typed my reply, up comes your review of the Nuraphones. Too bad they're horrible. I sent you an e-mail message because the character limit here is frustrating. Another option is PM to here.
      yuriv, Feb 13, 2019
    3. oluv
      Hi Yuri, sorry I just discovered your email within my spam-folder, not sure why it landed there. I will read it now and let's continue our discussion over there...
      oluv, Feb 14, 2019
    4. hakuzen
      superb deep review!!!! thanks a lot
      hakuzen, Mar 2, 2019