Review: Mixcder MS301 Bluetooth V4.2 Wireless Headset with aptX

Whenever I’m out and about, especially when commuting on public transport, I’m often listening to music or watching a video on my phone. Having a set of headphones over my head is my way of making the commute more bearable by “tuning out” the outside world. When I look around, it’s something a lot of people do. It’s rare to see people not fully absorbed into their smartphones with a set of headphones or earphones on.

But as technology advances, the frustrations of tangled, snagged or broken cables are something users often wish they didn’t have to contend with. Likewise, manufacturers are slowly following Apple’s lead in removing the “legacy” 3.5mm headphone socket. The result is clear – a preference for Bluetooth wireless audio devices.

While there is a big market for Bluetooth stereo headsets, they have never quite met everyone’s expectations. For one, the Bluetooth connection is limited in bitrate and thus audio quality is compromised due to the use of compression. Most headsets on the market use the “standard” SBC (sub-band coding) codec, which is adequate but not “hi-fi”. It’s often likened to 128kbit/s MP3 encoding with some audible artifacts especially in treble and stereo imaging. There is also a 200-250ms delay due to encoding/buffering which can result in synchronization issues. It is one reason why I still very much prefer a cabled solution.

However, when I was approached by Mixcder about reviewing their MS301 which features aptX low-latency support, I decided it was worth giving it a go – after all, I did have an aptX capable Bluetooth dongle. This review of the MS301 was made possible thanks to their generosity, and is performed with their agreement to the review challenge terms.

What is aptX? Why does it matter?

As mentioned in the introduction, traditional Bluetooth A2DP (stereo audio) devices typically use the Bluetooth SIG’s standard sub-band coding (SBC) codec. This is a computationally inexpensive codec with no additional licensing requirements, and is thus the most popular amongst devices. Unfortunately, it has limitations when it comes to quality which can result in audible artifacts. Thankfully, the Bluetooth SIG also allows for third-party codecs which can provide better quality, of which MP3, AAC and aptX are options. In the market, very few to no devices are known to use MP3 due to licensing issues, and AAC appears to be used by Apple products primarily.

aptX was introduced to Bluetooth headsets by Cambridge Silicon Radio (CSR for short, now part of Qualcomm). This codec operates at a higher bit-rate of 352kbit/s and offers higher quality than SBC (which runs up to 328kbit/s at best quality, often less and with a less efficient algorithm). There are several variations of aptX, including low-latency which runs at just 40ms latency making delay imperceptible, and high definition/lossless which offers a “near lossless” experience with higher sample rates and bit-depths. For these functions to operate, you must have both sender and receiver aptX-compatible, which normally means of a “compatible” chipset and with licensing fees paid. Otherwise, devices will revert to a “basic” SBC mode.

The Mixcder MS301 supports the “regular” flavour of aptX as well as aptX low-latency mode. Failing this, it should fall-back to regular SBC mode for other devices. Note that some others have confused aptX-LL as meaning lossless – it does not mean lossless, but merely low-latency.

Support for aptX is listed on Qualcomm’s site, of which there are a fair number of devices supporting aptX, but much fewer supporting aptX-LL or aptX-HD. However, some Android devices can be hacked to enable aptX even if not officially supported (at your own risk). When it comes to PCs, only those using CSR Bluetooth chipsets with the Harmony stack support aptX. Of note is that no Apple devices support aptX, thus using an aptX device with an Apple device will result in an regular SBC connection.

As a result, it might pay to do some research beforehand to see if your devices support aptX before buying a headset. However, even if your device does not support aptX, it should still work with your device albeit without the benefits that aptX brings.

The Package

The unit comes packaged in a black coloured cardboard box. The front side has a iridescent gold-coloured print sporting a line-art drawing of the headphones themselves, along with the aptX logo. It lists some features including 10m transmission distance, 20 hour talk/play time, last-call redialling and 2200 hours standby.

The rear of the box provides the specifications – the key specifications are a 40mm driver, 32 ohm impedance, 20Hz – 20kHz frequency response, 90+/-3dB sensitivity, 500mAh rechargeable lithium battery.

The headphone is supported on a black plastic tray with a box including some accessories.

The included accessories include a thin microUSB charging lead, a 3.5mm to 3.5mm stereo lead for wired usage, and a multi-lingual instruction manual booklet.

The headphones themselves feel moderately weighty due to the use of metal parts and construction, with padded surfaces covered in a soft pleather material. The headband has the brand embossed into it.

A closer look at the stitching of the material on the headband seems to show some waviness.

The branding is also on each of the metal earcups, which is not as discreet as it could be, but isn’t too conspicuous. The headband is internally a stainless steel band, which connects to a metal hinge section.

The hinge itself feels fairly durable as a result. The metal hinge is connected to the metal earcup through a plastic grommet to allow the earcups to swivel in one dimension. This arrangement was smooth on one side, but slightly tight on the left which resulted in some creaking noises when adjusted.

The internal plastic backing of the headband has a number of click detents allowing for the headband to adjust in length to suit various sizes and shapes of head.

On one side of the interior face of the headband, the model number is printed. The other side has a label with regulatory approval numbers on it.

Removing it reveals the aptX logo.

A closer look at the rear of the earcup shows that only the rear portion is metal, with a small vented “gap” between the rear and front plastic portion. This gap is intentional, and provides the ability for the earcup to pivot up and down to ensure a comfortable fit. The front plastic portion does have a slight amount of “creak” to it on one side.

Each earcup is externally covered with a generous amount of pleather. The foam inside is not quite filling, resulting in a bit of a “baggy” look. The inner surface of the ear cushions is covered with a plastic-like material of a different texture and some fabric. The left and right orientations are printed on the fabric inside the cups for easy reference.

The right side earcup houses the main controls which include a power button, power LED (which shines through a hole in the casing), volume up and down buttons, a 3.5mm jack for “emergency” wired operation and a microphone. There is an extra hole at the top which does not seem to have a specific function.

The left-side earcup provides access to the microUSB charging port and a hole is provided to show the charging status.

The hinges allow the unit to swivel with the cups laying flat for transport.

It is also possible to contort it into a more compact shape, although as pressure seems to be applied onto the earpads, this is not recommended.

Teardown

Disassembly starts by removing the ear cushions, which are fitted with a bayonet mechanism. This is done by rotating and then unclipping the whole assembly – if you attempt to peel the cushions off, you are likely to damage the cushion. Undoing four screws lets us gain access to the driver.

The driver is unmarked, and its make is unknown. There is a piece of felt wadding inside the chamber to provide damping. This being the right earcup, there is a piece of self-adhesive tape which is metallized and acts as the antenna for the unit. Notice how it is torn – this was how it was received.

After carefully peeling it away to try and prevent any further damage, we can see the metallized pattern on the rear. I don’t believe the design intended for the antenna to be torn, as it seems this basically breaks one of the elements of the antenna and disconnects it. This may adversely affect the performance of the unit, and demonstrates poor manufacturing QC or a design problem, especially when the stiffness of the soldered coaxial lead is taken into consideration.

The active side shows the use of a module featuring a CSR A64215 chipset. A look at the datasheet shows this particular chipset as being capable of Bluetooth v4.2, 9dBm transmit power and -90.5dBm receiver sensitivity, AVRCP v1.6, wideband speech support with HSF v.1.6 with mSBC, cVc technology with wind noise reduction, multi-point A2DP support, aptX/aptX low latency/SBC and AAC support and wired audio support. While the chip itself is capable of these features, not all of them will be available in end products.

The module’s antenna output is connected to a socket where a coax lead brings the signal to the torn printed flexible antenna. Aside from that, there are a few wires which come from the other ear-cup that bring power and driver connections from that side. A single microphone capsule is seen as well as a few switches, a 3.5mm socket and indicator LEDs.

Removing the screws allows for the underside of the PCB to be examined. There are no components mounted on the underside, but there appears to be many provisions for ESD protection diodes which have not been fitted. These may not be entirely necessary, but their absence implies a cost-reduction measure. The PCB manufacture date is 3rd week of 2017, and the project itself is dated 23rd November 2016, making this a pretty fresh product. Its project name appears to be B032P or BT15215.

Opening the other earcup, I realize I’ve forgotten to show the intermediate disassembly step where the plastic pivot hinges are removed. These are screwed in, however, are plastic so it would not be advisable to place too much stress on the front portion of the earcups themselves.

As promised, there is a BYT Li-Polymer 3.7v 500mAh cell. This one was manufactured 7th February 2017, making it very fresh as well. The board features charge regulation for the battery, which is itself protected with its own protection PCB.

The underside of this PCB does not have any components either. So that’s all the internals covered – it’s definitely using the “right stuff” to have aptX capabilities, and it seems to have proved itself to be honest in regards to the battery capacity. However, the lack of ESD protective components on the PCB, the torn flexible antenna and the plastic pivot hinges seem to be some negative points on the construction.

Set-Up

Regular users of Bluetooth devices will find set-up simple and familiar. Pressing and holding the power button puts the unit into pairing mode, and Bluetooth Secure Simple Pairing means that in most cases, entering a PIN code is unnecessary. The unit makes things somewhat easier by featuring voice feedback in the form of voice prompts so looking at the LEDs is not necessary.

Android with aptX-compatible Qualcomm Bluetooth Stack

Pairing with my Mi Max was easily achieved by scanning for the device while in pairing mode, and clicking on the device name.

Once connected, the device also shows its battery status in the status bar of the phone. This is a feature of some, but not all, Bluetooth headsets.

To verify the ability of the unit to connect in aptX mode requires CatLog and root access. Once some music is played, the log should display the codec selected as aptX. A quick check of the OUI shows that the internal module is a Shenzhen Boomtech Industry Co. Ltd module.

In the case your device does not support aptX, or you are using a headset without aptX support, you will see SBC instead (like the screenshot below).

Windows 7 with CSR Bluecore-based USB Bluetooth & aptX-compatible Harmony Stack

Adding the device follows the same basic routine of placing the device into pairing mode and adding a new device.

Pairing is established quickly with no PIN code required.

When properly completed, the unit should connect automatically and the aptX banner should display to confirm the presence of aptX connection.

The device will also come up in the sound devices, and can be set to default to route audio through it.

While it was possible to get it to work, it wasn’t always quite this easy. In fact, initially, I ran along a few issues which are due to the no-longer-maintained CSR Harmony Bluetooth Stack being just plain buggy.

The first time I tried, I could pair the device, but the Bluetooth Audio Renderer for Bluetooth Stereo Audio came up as “Not plugged in”. The aptX banner also did not appear.

Manually attempting to connect to A2DP (Sink) resulted in a time-out after a minute of waiting. No audio aside from the “telephone quality” handsfree was achieved under this situation. Rather interestingly, this unit also claims to do A2DP (Source) and Serial Port connectivity too.

In order to resolve this issue, I had to go to device manager and remove the two Bluetooth Audio devices.

Then I had to unpair the device by removing it within CSR Harmony.

Then, I set the headset to pairing mode, and paired the device. At this time, the drivers should re-install. Then, turn the headset off, and then back on so it auto reconnects. At this time, you should see the banner indicating success.

Unfortunately, this seems to be a temporary fix. Once the device is unpaired or the computer is restarted, the same symptoms will re-occur and following this procedure is required to restore connectivity. This seems to be the fault of the Harmony stack software which was last updated about five years ago, but sadly, is the only Bluetooth stack that allows aptX connection on a PC at this time to my knowledge.

Note that this is not a problem with the Mixcder MS301, but more a problem with the CSR Harmony software. However, if you do use the CSR Harmony stack, you may have problems connecting even in SBC mode.

Windows 10 with Broadcom-based Bluetooth Solution

Unfortunately, when using non-Qualcomm/CSR Bluetooth solutions, it is not possible to achieve aptX compatibility. However, pairing and using the headset is still just as simple and completed with no issues.

Once Bluetooth was turned on, the device placed into pairing mode, and a scan initiated, the device could be paired. No PIN code entry was required.

A short wait was necessary as Windows configured the drivers for the device.

Once ready, connection was established and audio routed through the device just fine.

Apple iOS 9.3.5

Unfortunately, I don’t use Apple devices primarily, so the “latest” device I use is an iPad 3rd-generation. Of course, we won’t get aptX capability, but pairing was easily completed and audio worked just fine, although presumably in SBC mode.

The battery indicator is also available under iOS.

Subjective Opinions

When it comes to audio products, opinions often differ widely. In this section, I’ll describe my experiences and feelings about the products, which some people may disagree upon. However, I won’t be drawn into arguments about it. For reference, I currently prefer the Audio-Technica M50x headphones as the “standard day-to-day reference”, and have listened to a good number of other wired headphone products ranging from AU$20 through to AU$350. While it may feel a little unfair to compare the product with a much more expensive product of a different category, this is the only way to adequately understand the strengths and limitations of a product.

That being said, everyone has a different idea of what “sounds” right or what sounds good, so feel free to ignore my opinions and form your own. That being said, I will remind you that I’m reviewing the product independently, with no financial incentive.

Ergonomics and Fit

The unit itself feels fairly good with a heft that implies some level of quality. It has good balance between the earcups, so as not to feel lopsided. The soft pleather also feels plush and sufficiently durable for everyday use. The headband has sufficient adjustment range to cater for larger heads, and the metal accents help improve the appearance and durability of the product.

When wearing the unit for extended listening sessions however, some discomfort can be felt. The clamping pressure feels slightly higher than other products. The wide and “baggy” pleather earcups form a positive seal to help improve isolation, however, the design is a hybrid supra-aural and circum-aural design with the pad both applying pressure to your ears and its surrounds. These two factors combined results in reduced breathability and “warm” stuffy ears. At least it does somewhat mitigate the risk of the unit falling off your head due to the amount of contact.

Isolation is average to fair. While the design of the earpads definitely help isolation, the vented rear plastic earcup defeats this to some extent, allowing some sound leakage in and out of the unit.

The design of the unit appears to deliberately ignore the inbuilt charging capabilities of the CSR chip and opt for a standalone charger IC. This design choice results in the possibility to use the unit to listen to audio while charging, which some people may find handy. The charging LED is easy to interpret and separate from the main Bluetooth LEDs – a red LED lights to indicate charging and turns off when fully charged.

All of the interface buttons are on the right side earcup, which makes it easy for one-handed operation. Like other CSR based devices, just three buttons are provided, which is easy to navigate by feel but results in the need to double-click the power button for redial, or long-click the volume keys for next/previous. To avoid the need to reference the LEDs, voice prompts are provided through the headset, but the voice prompts and tones are fairly loud. This may ensure that all users can clearly hear it, but is also very disconcerting to those with more sensitive ears as the “end of volume range” beep and battery low beep can be loud enough to startle. There doesn’t seem to be any way to change this, unfortunately. The LED on the right side earcup does indicate status, and when connected, shines a solid blue which is less distracting than the flashing blue of many other headsets.

The unit does offer battery status monitoring over Bluetooth so that your phone can display the battery status. However, in testing, this was found to be very approximate. In one case, it showed about half-full and dropped into the red after merely a minute or two of playback. As a result, it cannot be relied upon as an accurate gauge of remaining power.

As the device is wireless, it is expected that users might choose to take the unit around. The hinges do have extra articulation to allow the unit to be contorted into a shape which minimises its space requirements, however, it does not come with any protective bag or casing thus leaving its pleather surfaces at risk of damage.

Bluetooth Sound Quality

I first started by auditioning the unit connected via aptX using FLAC files of music I was familiar with. I spent at least 60 hours throughout two weeks listening to the headphones in aptX mode, and then several hours afterward listening to it in SBC mode paired to devices which did not offer aptX.

The character of the headphones seem to have a slightly veiled and laid back treble, offering a warmer presentation. This is not unexpected, since my reference M50x are sometimes criticized for being a bit too clinical and “sharp”. The upper midrange seemed a bit resonant and boosted, which reduced the clarity of the audio slightly. The unit was not especially bassy, offering a good balanced bass although one which does not extend very deeply, thus some basslines are almost completely lost. If I had to summarize the sound quality in general, it would be more balanced to warm, but very “average” in the clarity department and something like a AU$40 wired set of headphones.

Unfortunately, this does not make them audiophile quality. This is particularly problematic, as people who specifically look for aptX on Bluetooth products tend to be those who look for higher fidelity products, and this one seems to fall a short of my expectations.

My frustrations were amplified somewhat by the fact when switching over to SBC-only devices, it was extremely difficult to distinguish the difference in quality between SBC and aptX mode due to the limitations in the sound quality of the unit. I could not be certain, but it seemed SBC didn’t have as well defined treble, but I could not confirm it definitively. I think this illustrates clearly just how limiting the quality of the drivers and earcup design is.

Unfortunately, there was another drawback which seems common to many Bluetooth products. During idle connected periods prior to being commanded to standby, the unit does have a noticeable amount of background white noise hiss. This is somewhat distracting during quiet portions of music, and persisted regardless of which codec was used. When commanded to standby, the unit drops to dead silence with a quiet “tick”, but this merely makes it more apparent just how noisy the module is when in operation. However, one positive is the maximum volume is more than adequately loud.

Directly-Connected Sound Quality

In a rather surprising twist of fate, when directly connected to my Soundblaster X-Fi Xtrememusic, the headphone has a slightly different quality. The treble was more prominent and stronger, verging on tinny but still lacking in fine detail. The bass was still somewhat limited. The upper midrange seemed more recessed and lacking in comparison. Unfortunately, I’d have to say the directly connected sound quality sounds extremely average, which probably stems from the design of the headphones and the driver units in use. While it certainly is not bad for casual listening, it’s not commendable in any particular way.

As a result of this result, it seems to suggest the CSR-based module while capable of directly driving speakers, may not be optimized to do so. Higher end aptX headsets may use its I2S capability and use that to drive an external DAC or buffer the output with an opamp rather than use direct connection.

Having the option of direct connection is a good thing, especially if users remember to bring their cables, so that they can use it with devices without Bluetooth capabilities or when the battery is depleted.

Testing

Battery Charging

I first depleted the headset by running a run-time test until it shut down on its own. Using my Keysight U1461A as a data-logger and my USB current shunt, it was found that the unit charged in 2 hours and 1 minute – pretty much right on time. The delivered charge was 510mAh from the USB, and due to the linear regulator, all of this would have been delivered to the cell minus a little bit to light up the status LED. As a result, the onboard battery is an honest battery with a capacity of 500mAh. Charge tapered and terminated as expected, and thus indicates it is safe to leave this unit plugged and charging.

Battery Runtime

Battery run-time was assessed by setting the unit to my preferred listening volume in a quiet room and running a song on loop with the audio recorded by a microphone. Total running time was found to be 25 hours and 56 minutes, exceeding the 20 hours claimed. This was with aptX audio, although run-time is likely to vary depending on the loudness, RF signal level, codec and playing material.

The claimed 2200 hours of standby is about three months and is a big claim, but what type of standby was not specified. When connected but idle in standby, the LED indicator shines a continuous blue – with this drain on the battery, I find it unlikely that 2200 hours of standby can be achieved. Instead, I suspect they mean on a soft-off state, or maybe even a disconnected standby state.

Microphone Voice Quality

I checked the quality of the microphone by recording a sample with myself speaking inside my quiet room environment. The resulting audio has a bass-heavy character lacking in treble detail. This was intelligible for the most part, although when tested “on call” with several people, they did note that it was difficult to understand when I was speaking quickly. This is likely due to the fact that there is no microphone boom – the mic merely sits inside the earcup and thus gets less-than-ideal sound.

This is no major issue, as most users will probably be using it to listen to music more than to make calls with, however should still be considered.

Transmission Range

I tested the range of the unit paired with my Class 1 (50m) CSR USB dongle, and my Mi Max mobile phone. With the Mi Max, I could easily reach 10m with clear audio despite the torn antenna, which may have been due to a good antenna design on the Mi Max.

However, with the Class 1 (50m) CSR USB dongle, I did have difficulties at around 4-5m, with occasional audio stuttering. At 10m, the unit was stuck in a continuous connect/disconnect loop. I suspect that if the antenna was not torn, the performance may have been improved.

The use of metal earcups and metal hinges makes adequate RF design difficult due to the potential for shielding or multipath reflections to arise due to the close proximity of the metal.

Conclusion

The Mixcder MS301 is a Bluetooth headset with a bit of an identity crisis. On the one hand, it offers an aesthetically pleasing metal-accented construction with lush black pleather earpads and premium aptX low-latency codec support. On the other, it targets a low price to give value for money. In the end, the result seems somewhat of a compromise.

For those specifically looking for aptX support and high-fidelity audio, they will be somewhat disappointed by the recessed treble, resonant upper-mid range and limited depth of bass. They might also be distracted by the background hiss that pervades every quiet section. If you’re specifically looking for high quality audio, you’re probably looking at much pricier products from major brands anyway.

For those looking for a Bluetooth headset with a decent build quality and better quality than the average “cheapy” plastic unit, then this unit does have merit as a step-up, offering more definition and better build quality. It is suitable for casual listening, and feels sturdy enough for everyday use. In this case, aptX is probably not on your priority list, but it doesn’t do you any harm so you might as well have it. It will connect as regular headsets do, in SBC mode. Given its retail price of about US$90, it does command a premium over a wired headphone of similar characteristics, but isn’t as expensive as (the few) other aptX capable options.

However, there was some observed build quality issues, mainly with the torn flexible antenna which may compromise performance slightly, and slightly creaky hinge and plastic cup on one side. The semi-open design also means that isolation isn’t as good as it could be. The hybrid supra-aural and circum-aural earcups with higher clamping pressure also isn’t as comfortable or breathable as some other products.

At no fault of the product itself, aptX support itself is also patchy due to the issue of licensing. Only a limited number of products support aptX which should bring better audio quality, of which no Apple products support it. Even fewer support low-latency. As a result, most users will never experience any latency advantage. Even if you do have aptX support, it seems doubtful that this particular set of headphones will let you experience it fully. I certainly found it difficult to discern any advantage from aptX over SBC, so I suppose if you’re considering buying this particular unit, it shouldn’t be because of the advertised aptX support.

Thanks to Mixcder for providing this unit for review.