Home » Reviews » Custom IEMs » Lear LCM BD4.2 custom in-ear monitor: Ultra-high performance 6 driver hybrid
Lear LCM BD4.2 custom in-ear monitors

Lear LCM BD4.2 custom in-ear monitor: Ultra-high performance 6 driver hybrid

Make: Lear
Model: custom fit – LCM BD4.2; universal fit – LUF BD4.2
Base Price: LCM model is HKD 9,998 ($1288); LUF model is HKD 8,888 ($1145); shipping HKD: 200 ($25)
Country of Manufacture: Hong Kong

Lear has been around since 2008, starting in China and moving to Hong Kong under Forever Source Digital.  They started making earphones and branched out to make portable amps and now custom in-ear monitors (CIEMs) and cables, and I have previously reviewed their previous flagship CIEM, the LCM-5, and their amp, the FSM-02 V2.  When presented with the opportunity to review their new flagship CIEM product, I jumped.  The flagship comes in two versions, the customized version, the LCM BD4.2 and a universal fit version, the LUF BD4.2.

Lear’s goal for the BD4.2 was to make a more accurate and capable performer than the LCM-5.  This was done using two different driver types, which is called a hybrid design.  The B represents balanced armature and the D represents dynamic driver, with four and two drivers per channel respectively.  At the time of writing, the BD4.2 is the highest driver count hybrid available and the only hybrid to utilize dual dynamic drivers.  In addition, the BD4.2 has bass adjustment capability to set the bass quantity to suit your taste, source, and environment.

General product information
Sound information
Source matching



The Lear BD4.2 can be ordered from the product page on the Lear website.  Click the Buy Now button, create an account or log in to an existing account and proceed through the process.  Payment options include PayPal and bank wire.  Impressions will need to be sent in before Lear can start working on your order, and turn time is 1-2 months due to the complexity of the product.  At the time of this review, the LCM BD4.2 Buy Now button is grayed out, but you can order by sending Lear an email.

Warranty: 1 year



The LCM BD4.2 utilizes dual dynamic drivers and four balanced armature drivers in vented acrylic shells that include a side mounted potentiometer for bass adjustment with flush mounted sockets for a detachable 2-pin cable connector.  The four sound tubes are smaller than any other I have seen to date by a large margin, with the BA driver sound tubes having a filter at the opening while the even smaller dynamic driver sound tubes don’t.

Since the sound tubes of the BD4.2 are by far the smallest I have seen and a typical cleaning tool (which is included) won’t reach, but the bass driver sound tubes can be cleaned with a needle if necessary.  In the three months of use/testing with the LCM BD4.2 there has been a small amount of cerumen (ear wax) build-up, some of which was partially blocking the sound tubes.  Cleaning them with a needle worked, but wasn’t the easiest due to the small size.  I am not yet sure if this will be a potential long-term concern.



The LCM BD4.2 came packaged in a nice cardboard box with the earphones and accessories placed nicely in an Otter Box hard case placed on top of the user manual.  Included inside the watertight Otter Box are a cleaning tool, screwdriver, carrying pouch, shirt clip, and cleaning cloth.  Otter Box makes very nice cases, and the one provided with the Lear is a nice hard-plastic version with a latch and lock mechanism that is easy to operate for a great experience.  The screwdriver unfortunately doesn’t have great quality and the tip bent when tuning the potentiometer.  While I haven’t seen a new screwdriver, Lear did say they have remedied the screwdriver situation.  9/10



The BD4.2 comes with the clear C2 cable which Lear sells as an aftermarket cable for HKD 668 ($86) shipped.  The C2 is made from high purity silver plated copper conductor using what they call the “Tinsel wire” technique.  While the cable is on the thinner side of the spectrum, Lear ensures the “Tinsel wire” technique results in maximum mechanical flexibility and much more resistant to failing as a result of metal fatigue than ordinary stranded wire or solid core wire.

The cable uses memory wire to hold the cable in place during activities and has a cable cinch made from heat-shrink tubing and extends quite far down the cable.  While the memory wire was on the more easily malleable side of the spectrum, the earphone stayed in place fine, but it easily changed shape between insertions.  The clear version of the C2 cable is treated with a special coating that prevents oxidization color changes.  6/10



The build quality of the Lear LCM BD4.2 is very good.  The shell finish is very good with no shape defects, but the transparency isn’t perfect with some specs of dust or dirt in some parts of the shell, and over time the inside has developed a film that has reduced the transparency.  I am not sure if this film is from internal debris that has settled like I have seen before, or due to the ported nature of the shell.  These issues are minor, but worth a mention due to the competing products in this price range that don’t have these occurrences.  6/10



While the LCM BD4.2 is ported, the isolation is on par with a standard acrylic shelled CIEM. 5/10



Disclaimer: My review is done in a comparative way using similarly priced IEMs and/or CIEMs for perspective and to determine performance.  In this review I try to accurately portray the product under review, presenting strengths and weaknesses, the sound signature, characteristics, and technical performance as opposed to providing flowery dialog of performance without perspective.  My ultimate goal is to enable you to make an informed decision about what product is right for you.  Take the review as a critical look at the product and not a sales pitch or marketing fluff.  I believe gear should be selected based on the sound signature you want and/or the specific use, not solely on technical performance or unsubstantiated hype.  Here are some quick references for more information: My review technique, Thoughts on reading a review, Custom IEM information

The Lear LCM BD4.2 and LUF BD4.2 received 100+ hours of burn in as is customary before serious listening.  The following custom CIEMs and IEMs were used for comparison: Spiral Ear SE 5-way Reference, Unique Melody PP6, Hidition NT-6, Hidition NT-6 Pro, Ultimate Ears Personal Reference Monitors, M-Fidelity SA-43, Lear LCM-5, and Lear LUF BD4.2.  Comparison write-ups can be found on page 2.


Bass: The BD4.2 uses a potentiometer for bass adjustment of the dual dynamic drivers, resulting in a very large variance in bass reproduction.  At the minimum setting the bass level is subdued but still present, retaining depth and power while taking a back seat to the rest of the frequency spectrum.  Turn the knob up to the maximum setting and the bass becomes quite prominent and powerful, even overpowering and somewhat resonant in my ears.  The maximum setting should provide more than enough thunderous bass for anyone, even bass heads.  The bass adjustment is no joke and really works, making a huge difference.

Turning the bass up doesn’t mean the quality is reduced or that the rest of the spectrum is degraded.  In fact, even with the bass maxed out, the midrange and treble retain their clarity behind the wall of bass.  With the bass knob about halfway, the bass is quite neutral and similar to the NT-6 while the Spiral Ear SE 5-way Reference (SE5) requires about 3/4ths to the max for an equivalent.  I don’t have anything that is similar to the max setting.  Texturing of the bass is very good regardless of the setting but does degrade in the last 15% of the adjustment knob.  Detail is plentiful, but slowly decrease as the knob level is increased.  Note sustainment capability is top-notch with the ability to really move air.  As the bass is increase, the warmth also increases.

The LCM BD4.2 has a very large bass quantity change, only matched by the Perfect Seal Fusion 11, which is similar to the BD4.2 with an unobstructed vent hole.  Quality of the bass is excellent, with performance that is approaching the top of the chart in quality and tops it in capability.


Midrange:  With a spacious, clean, and clear midrange, the LCM BD4.2 envelops the listener in a large soundstage.  Detail levels are very high with excellent imaging and instrument separation, especially considering the laid-back presentation, while the clarity is just a hair below the Hidition NT-6, but better than other spacious sounding CIEMs such as the M-Fidelity SA-43.  Layering and resolution within the soundstage is very good, approaching but not quite reaching the top performing SE5; however the presentation perspective adjusts with the mastering similar to the SE5.  This can result in a more forward or distant sound in comparison with other CIEMs that don’t change the presentation perspective.

The presentation isn’t for those that want to have an intimate connection with the vocals, but space is conveyed more like headphones than IEMs, and is along the lines of a “reference” sound such as the Ultimate Ears IERM, but with a larger space.  Proportions of the soundstage are natural with exceptional imaging.  Overall, the space, layering, proportions, imaging, instrument detail, and resolution combine for a recreation of music that is top notch.


Treble: Treble can often be a trouble spot for in-ears, especially those that use balanced armatures for the treble.  While it isn’t a big issue above $1K, there are still different levels of “good.”  The LCM BD4.2 treble is exceptional with a natural note attack and decay for a smooth sound that retains good levels of detail.  With a bit of forwardness in comparison with the midrange, there is a slight emphasis, but in the grand scheme of things it is laid-back compared with others such as the Ultimate Ears IERM and Hidition NT-6.

Treble smoothness is also absolute top-notch, with the SE5 and Fit Ear PS-5 as the only competitors, but the BD4.2 maintains the smooth, detailed response regardless of the track quality while the others, especially the SE5, will make issues with tracks/masters stand out like a sore thumb.  Overall, the treble region is one of the best I have heard from a quality standpoint with the ability to reveal issues, but not make them offensive.


Presentation: Spacious.  Very spacious!  The LCM BD4.2 presents with the most space of any CIEM I have heard both on average and from a projection standpoint, although the SE5 is close in projection.  This presentation perspective isn’t fixed though as it adjusts to the mastering of each track and can sway from a more upfront sound to a laid-back one.  Imaging within the presentation is top notch and the focus of notes is among the best.  While resolution is good, it doesn’t have quite the black space or resolution of the SE5 or Hidition NT-6 pro, but neither presents with the spaciousness of the BD4.2.

Note ADSR is very natural across the entire frequency spectrum, with an excellent decay rivaling the best I have heard, the SE5.  Capability is also excellent, although it doesn’t deviate too much from normal like the SE5, maintaining a smooth yet detailed sound.  Transparency is also top notch as the BD4.2 gets out of the way of the music, making you forget you are listening to earphones.  Coherence between the drivers is also excellent as the ADSR characteristics and volume levels are extremely well matched between drivers.  Dynamic range is very good and fits well with the sound signature, providing good punch when needed and excellent differentiation between the quietest and loudest notes, although you do have to listen more for it due to the presentation perspective.


Volume performance: The sensitivity of the BD4.2 is lower than typical for a CIEM which makes it better for low-level listening and less susceptible to hiss and noise in the source chain.  Very low volume levels have a lower bass presence and detail levels are less pronounced due to the spacious sound signature, but the bass knob can turn up the bass level.  Performance at all other volume levels is excellent, with the ability to play very loud while maintaining clarity and quality.


Sound Summary: The Lear LCM BD4.2 offers a large, spacious presentation with a perspective of distance compared with the typical earphone.  Technical prowess puts the BD4.2 among the best I have heard with plenty of detail, a very natural note with excellent coherence across the frequency spectrum, and good matching with lower-end sources making listening easy.  Imaging is exceptional as is transparency, putting you in the audience for an enveloping, involving presentation.

Bass quantity stands up to the best and is adjustable, enabling matching the bass levels of other CIEMs, or just adjusting you’re your liking.  Tonality changes as the amount of bass changes as the treble is flat and neutral but not rolled-off.  Clarity is excellent, especially considering the presentation perspective, which typically reduces instrument detail articulation and overall clarity.  All in all, the LCM BD4.2 is a top performer.


Page 2: comparisons, source matching, and overall summary



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Having a life-long love of high-quality audio and gadgets, average_joe got back in touch with his audiophile side after a hiatus caused by life. His focus became headphones and related gear as the size and price fit his life better than home audio. He believes the entire audio chain is important, and likes to continue to think past the headphone and on into the head, as he believes understanding the details of how we hear will lead to a better audio experience.


18 Responses

  1. The treble on my LCM BD4.2 is top-notch and actually quite forgiving, but unless you crank the bass it has a balanced sound vs. warm. The treble is more forgiving than others such as the Hidition NT-6, Custom Art Harmony 8 Pro, and even the Spiral Ear SE5; the BD4.2 treble is as smooth as I have heard. The LUF (universal) version is a different story as it isn’t quite as good and is tip dependent.

    Other options with more relaxed treble and similar overall quality are the Fit Ear PS-5 and to a lesser extent the AAW W500 AHMorph. If you have overly bright recordings, they would most likely be better options.

  2. Hello, thanks for the review!

    I’ve heard that this CIEM is merciless to bad recording, is that true? What do you suggest for people who have a lot of overbright Japanese recordings ranging from very bad to good enough? I’d like to have warm phone with very good and natural female vocal, strong bass that doesn’t intrude on the mids and non-sibilant treble, this could even take a seat back as long as it’s detailed and extended enough (don’t want it to be super revealing). I’d like it to be coherence too but I don’t really mind medium soundstage as long as it has good imaging and positioning (not super important but nice to have).

  3. Hi Joe,
    I have decided to go with Spiral SE5 + Pure silver cable. I’m thinking about reference DAP. Be honestly, I like Colorfly C4 design. What do you think about it? Is it the best one for SE5 (Sound Quality aspect)?
    Best regards.

  4. Hi Sun,

    Silicone is typically better in isolation and softness, but that doesn’t necessarily mean better comfort. Fit is primarily responsible for comfort, and stability is dependent on both fit and your anatomy. I can be comfortable with either acrylic or silicone for extended periods of time if they fit right. I have needed refits with both due to discomfort and/or a bad seal. Isolation can be seen in the scores; silicone is better, and/or filled acrylic.

    I will post when I have a chance to test the BD4.2 with a copper cable.


  5. Hi Joe,
    Thank you for your email. Lear BD4.2 has many advantages: Cheaper price, easy to order, sound signature is my taste. However, as I learn, silicon is better than Acrylic in isolation and softness. In my opinion, the comfort and stability when listening is the most important, SE5 win this point.
    What do you think about the isolation and comfort when use acrylic CIEM vs silicon CIEM?
    About cable, what I learn form Speaker is that Pure cooper or silver is better then silver plated cooper. Thus, in your review, when you use silver cable (which make sound brighter) for SE5 (which is a little bit dark) the result is very good.
    Please try pure cooper cable with Lear and let me know your feeling. I think that will be great.
    Still concern between Lear BD4.2 vs SE5.
    Thank Joe.

  6. Hi Sun,

    Talking about source first, the DX90 plus Portaphile Micro with MUSE 2 op amps is an excellent, portable source. The amp is excellent and adds to the overall presentation a good deal. After reading about your music, I think the LCM BD4.2 is the best choice and the SE5 is next. The reason I say that is because I also listen to most of the music you mentioned and some, such as Nightwish, G&R, etc. aren’t mastered that well. Those flaws are very apparent with the NT-6 Pro, and the Legend also reveals the issues. While the SE5 doesn’t bring the issues to light in the same way, it is less forgiving than the BD4.2. The cable of the BD4.2 is Lear’s aftermarket cable, so I think it is a good thing to stick with. Would a Whiplash cable help? Maybe, but I can’t say until I have the time to pair the two.

    I hope this helps, and please let me know if you have any other questions.



  7. Hi Joe,
    Thank you for your reply. I know that it’s hard to replace Stax SR 009 so I’m looking for something close to it.
    Previous years, I owned Thiel CS 3.7 + Classe Pre + Edge Pow + Weiss DAC and feel very comfortable with it: Natural sound, mid and high is so real and detail, not too warm, color or analytic, bass and mid bass are very impact, not too strong to make me tired, just enough to make me excited, Singers and instruments are in right positions. Sum up, I could spend days and enjoy the music, not analyze the sound. And Stax SR 009 can do the same.
    I intend to use Hifiman 901 or iBasso dx90 or just ipod classic + portable DAC/AMP as sources, with music 16bit 48kHz (Something 192kHz is not my favorite, too detail and tired to enjoy). My taste is Pop (Field of Gold, Betrayal…), Country (Willie Nelson), Gothic Rock (like Phantom of the Opera performed by Nightwish band, Evanescence band), Alternative Rock (Simple Plan, Linkin Park, Guns and Roses, Nirvana), Some Opera. Metal or Jazz are not my favorite.
    I spend time search your post in also and see some flagship CIEM like: Spiral Ear SE5, Lear LCM BD4.2, Earwerkz Legend, Perfect Sound PS8, Hidition NT-6 Pro, M-Fidelity SA43… Be honestly, I have no experience in CIEM, could you give me some recommend about a full combo:
    1. Source: Portable Player (with DAC/AMP) or Portable Player + DAC/AMP or Portable Player + DAC + AMP (Need to be portable, because I travel a lot)
    2. Cable (I do understand that cable is very important)
    3. CIEM
    Look forwards to hearing from you.

  8. Hi Sun,

    Replacing a Stax SR009 with something portable is difficult, and nothing I know of offers the same sound as in-ears have a very different presentation perspective. Unfortunately, I haven’t had a chance to A/B the Stax with any CIEM, so I can’t say for sure what level of performance these two are at in comparison, but I would say the BD4.2 is closer than the SE5 purely due to the more open, spacious sound.

    What source will you be using, what type of music do you listen to, and what bitrate? What do you like best about the 009?

  9. Hi Joe,
    I have just sold my Stax SR 009 combo because I have traveled a lot. Now, I’m looking for a CIEM combo which have the similar sound to Stax SR 009. I see your list I think that may be Spiral Ear SE5 or Lear LCM BD4.2 can be my taste.
    In my country, there is no distributor of 2 brands so I can only blindly buy.
    Could you give me some advice?
    Thank you so much for your time.

  10. Thanks for reading and the kind words.

    The LCM version is an excellent performer indeed.

    As long as the knobs are in the same location, the sound is balanced. I haven’t yet had to adjust after my initial adjustment.

    The Clip+ can provide some excellent performance from the price.



  11. I love your reviews! It’s like a virtual audition….. enough said.

    Wow…these sound like end-game neutral IEM and versatile to boot. The last time I heard about these was on the horror LUF tour thread.

    Tunable bass that never messes with the mids is the dream(for me at least :P). The versatility quotient skyrockets.

    Q : Is it easy to balance the L and R tuning knob positions? Or does it take multiple tries with every change. Depends on how sensitive it is I guess.

    PS: Mighty clip+ is mighty.

  12. Ah. I agree that Noble products are art; stunning. From a pure sound quality standpoint though, I have heard mixed reviews on the K10. Looking at the headphones you listed, the HD800 seems to be an outlier. If you want a brighter sound, Hidition is open and relatively spacious, but not one of the available products. The UE PRM is much better than the IERM, but then it cost double. Let me know if you have any other questions. Thanks!

  13. The place where i live has authorized dealers of Rooth, ADW, Custom art, JH, Noble, Hidition and UE so it’s easier for me to purchase products from companies above. I have read a lot of reviews about Mentor and K10, many say K10 is the best one out there while some claim the Mentor is even better. K10 has that amazing look and build quality and i just have to wait for a month to get it. JH is nice to but the waiting time just kills me. I have listened to many IEMs and headphone before but my ears sweat a lot so it’s pretty annoying wearing them for a long time so I decided to get a CIEM. My favorites are HE400, 500, HD800, IE800, Dunu 1k, 2k… Oh and what I like the most is the soundstage performance of an IEM or a headphone.
    In my mind right now are NT6+Whiplash hybrid combo, Mentor, K10, UERM and probably BD4.2. I’m planning to get a Hibino HDP-R10 to pair with one of the above :). But I couldn’t decide which one to buy.

  14. Unfortunately I have never had the opportunity to hear the 1plus2. From what I understand, it is also spacious with neutral bass, but I don’t think it has as much space. Of course, without a comparison, there is no real way for me to know. Sorry.

  15. I have only read about the sound of both, so I can’t give a first hand response. Why have you decided to choose between the K10 and Mentor? There are plenty of other CIEMs out there, so what about those two is attractive to you? Also, what other IEMs and/or headphones do you like/dislike?

  16. Thank you for such a great review. I’m having a hard time choosing between Noble K10, UM mentor and this. Can you give me any advices? I listen to every genre but mostly pop and vocal.

  17. any chance you were able to listen to a 1plus2, silver/gold and uber. Just want to know how the two compare with the 4.2

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