Moondrop Chu II DSP - EQ Review

[DavidK442]

I just received the Chu II DSP. My Windows 11 Dell laptop is having difficulty consistently recognizing the DSP cable on the USB-C port. I have been using the Apple branded USB-C to 3.5mm dongle with the 7Hz Zero 2 IEM's flawlessly. Tried switching back and forth to compare sound and had to reboot the computer to have the Chu II DSP cable recognized.
When it was working, my impression is that the upper-midrange/lower treble is more pronounced compared to the Zero 2. A nice lift in detail on some recordings, but a bit too forward on others. As the app does not work on Windows, I assume the "Default" Harmon tuning is active. Wish I had access to the parametric EQ to tweak, but regardless will be returned due to the spotty USB recognition.

 

[gcompari]

Interesting product: but do someone tried to answer a phone call with these IEMs?
I tried the Chu II DSPs with 8 different Android phones (of different brands: LG, Samsung, Google Pixel, Xiaomi, OnePlus) and they don't work with phone calls if I use before USB Audio Player Pro.
I must detach the USB-C plug and reinsert it to make them work for a phone call.
I tried them on a Samsung S22 and I can't hear anything during a phone call: only very distorted sounds, also if I don't use before UAPP. Simply don't work at all for make a phone call. At the other end of the line, my interlocutor tell me that he can hear me, but I can't understand anything from what I hear. Playing music with UAPP: no problem.
I tried 5 samples of the Chu II...
No problem with PC/Windows: they work flawlessly with Meet, Zoom, Teams, Skype, WebEx and Foobar 2k in "WASAPI (event)" mode (the first one: with all others I have to use "WASAPI (push)" mode w/o loading a driver for a DAC).

 

[Eary]

Interesting product: but do someone tried to answer a phone call with these IEMs?
I tried the Chu II DSPs with 8 different Android phones (of different brands: LG, Samsung, Google Pixel, Xiaomi, OnePlus) and they don't work with phone calls if I use before USB Audio Player Pro.
I must detach the USB-C plug and reinsert it to make them work for a phone call.
I tried them on a Samsung S22 and I can't hear anything during a phone call: only very distorted sounds, also if I don't use before UAPP. Simply don't work at all for make a phone call. At the other end of the line, my interlocutor tell me that he can hear me, but I can't understand anything from what I hear. Playing music with UAPP: no problem.
I tried 5 samples of the Chu II...
No problem with PC/Windows: they work flawlessly with Meet, Zoom, Teams, Skype, WebEx and Foobar 2k in "WASAPI (event)" mode (the first one: with all others I have to use "WASAPI (push)" mode w/o loading a driver for a DAC).

I actually talked to their customer service about heavily distorted sounds I hear when making phone call, the otherside's voice sounds robot-like. They directed me to apply for a repair service, I mailed them my product and waiting for them to fix it. After waiting for a week they mailed me back a new one, it seems they didn't even understand the issue I reported, because on the new box it writes that the old one has "microphone issue" and it writes that the way to fix it is "exchange for a new one". I tried recording audio using the cable's mic and the recording is fine, so they basically didn't even test the problem I reported to them. And the new one they gave me, has the same issue, it works perfectly fine for media consumption, but when doing phone call, I always hear the otherside's voice got heavily distorted.

At this point I thought it was my Samsung phone's issue, but you said you tried many brands and the problem persists, that's might be an issue with the product then. Not sure if it's the DSP cable's problem, it's so annoying.

I must detach the USB-C plug and reinsert it to make them work for a phone call.

You mean doing that during the phone call? Unplug the type C end during phone call and replug it again? Interesting, might try it next time.

edit: Tried, not working for me. unplug and replug, still the same distorted sound.

 

[Jeromeof]

For me the microphone was very poor quality, so I just didn't use it for calls.

 

[gcompari]

I actually talked to their customer service about heavily distorted sounds I hear when making phone call, the otherside's voice sounds robot-like. They directed me to apply for a repair service, I mailed them my product and waiting for them to fix it. After waiting for a week they mailed me back a new one, it seems they didn't even understand the issue I reported, because on the new box it writes that the old one has "microphone issue" and it writes that the way to fix it is "exchange for a new one". I tried recording audio using the cable's mic and the recording is fine, so they basically didn't even test the problem I reported to them. And the new one they gave me, has the same issue, it works perfectly fine for media consumption, but when doing phone call, I always hear the otherside's voice got heavily distorted.

At this point I thought it was my Samsung phone's issue, but you said you tried many brands and the problem persists, that's might be an issue with the product then. Not sure if it's the DSP cable's problem, it's so annoying.



You mean doing that during the phone call? Unplug the type C end during phone call and replug it again? Interesting, might try it next time.

I tried five samples of Chu II DSP: isn't a problem of a single sample of Chu II DSP.
It's a design problem (FW? HW?)
WIth LG, Pixel, Xiaomi, OnePlus the Chu II DSPs work w/o problem until I play a hi-res track by UAPP.
With Samsung the Chu II DSPs don't work always, also w/o using UAPP.
With LG, Pixel, Xiaomi, OnePlus, after playng something by UAPP, I must unplug and replug the USB-C connector of the Chu II DSPs to make them to work with Android Apps and phome calls.

 

[gcompari]

For me the microphone was very poor quality, so I just didn't use it for calls.

I saw other negative comments about the mic of the Chu II DSP: for me the mic is very good.
I tried to make phone calls with many phones (but not Samsung), with two samples of the Chu II DSP at both side of the phone call and I can hear perfectly and at the other they hear me always perfectly: with full treble and bass in my voice (i.e. a voice with "body") and with a lot of "detail", so I was very satisfied about the mic.
Also with PC/Windows and Google Meet the result it was really impressive.

 

[gcompari]

For me the microphone was very poor quality, so I just didn't use it for calls.

In my opinion the Chu II DSP make sense to exist for the following reasons:
- make phone calls (why a microphone otherwise?)
- have a hi-res system available at a cost of about $20 (incredible!)
- not having to use a system to listen to music and another for calls
- the simplicity of a single cable for IEMs with phones without a 3.5mm plug
- avoid clutter, various devices connected to the phone that hinder its use and that risk breaking the connectors of the phone or the additional devices themselves.
To listen only to music, then it is better to have either an LG phone with ESS Sabre Quad DAC or an external USB DAC like the Tanchjim Luna and Chu II with passive cable w/o any DAC/AMP/DSP.
With the Chu II DSP I turn off all the filters (only 5 filters with frequency limiting and attenuation/gain do nothing to make the Chu II DSP compliant with the HK IE 2019 v.2 curve (Crinacle B&K 5128 measurements): it takes 13 filters with attenuation of -10.50db and amplification of 10 dB, frequencies from 20Hz to 18700Hz) and I use the equalizer of the UAPP player (unfortunately only 10 filters available).
With Windows I use Foobar 2k and MathAudio HP EQ with 13 filters: the filters of the Moondrop C-DSP cable are not enough for a good approximation of the HK IE 2019 v.2.

 

[Jeromeof]

Well I often use IEMs outside my house ( I have many work calls during the day ) and while technically the microphone worked ok inside my house in a quiet room compared to more advanced microphones ( which cancel background noise during a call ) I thought it was poor when outside ( and why I didn’t really mention it when I wrote this original post )

 

[gcompari]

Well I often use IEMs outside my house ( I have many work calls during the day ) and while technically the microphone worked ok inside my house in a quiet room compared to more advanced microphones ( which cancel background noise during a call ) I thought it was poor when outside ( and why I didn’t really mention it when I wrote this original post )

I agree: the mic is very sensible and there isn't any noise active reduction system. Normally I call from a quiet place and I like the detail of the Chu II mic. In a noisy environment this may be a problem. I don't like the loss of detail that active noise reduction systems cause: fortunately I don't need it.

 

[CedarX]

With LG, Pixel, Xiaomi, OnePlus, after playng something by UAPP, I must unplug and replug the USB-C connector of the Chu II DSPs to make them to work with Android Apps and phome calls.

Doesn’t this indicate some kind of an Android (or Android customization) problem? How would Chu II “know” that you were playing something through UAPP?
I don’t know enough about Android, but on Windows for example, a “headset” is not the same thing as a “headphones”, could it be an Android/Chu II configuration problem and the “assumptions” made by Android about the device?

 

[CedarX]

With the Chu II DSP I turn off all the filters (only 5 filters with frequency limiting and attenuation/gain do nothing to make the Chu II DSP compliant with the HK IE 2019 v.2 curve (Crinacle B&K 5128 measurements): it takes 13 filters with attenuation of -10.50db and amplification of 10 dB, frequencies from 20Hz to 18700Hz) and I use the equalizer of the UAPP player (unfortunately only 10 filters available).

Considering the uncertainty/error of any HP/IEM measurements, the fact that a target is just that—a target—but it’s not the exact (unknow) “target” for any individual, why are you trying to match exactly HK IE 2019 v.2?

I would argue that 5x DSP filters is “good enough” to get close to ‘a’ target and explore around… And if it’s not good enough, then Chu-II is certainly not the right IEM for the desired outcome.

 

[gcompari]

Considering the uncertainty/error of any HP/IEM measurements, the fact that a target is just that—a target—but it’s not the exact (unknow) “target” for any individual, why are you trying to match exactly HK IE 2019 v.2?

I would argue that 5x DSP filters is “good enough” to get close to ‘a’ target and explore around… And if it’s not good enough, then Chu-II is certainly not the right IEM for the desired outcome.

Among the Audio Science Review tests I found only 3 transducers from electrical signal to acoustic pressure that have the following characteristics:
- THD always less than 1% at any audible frequency at any sound pressure up to the maximum bearable for the human ear.
- Possibility of equalization by very high approximation of the Harman Kardon IE 2019 v.2 curve (I believe the latest available with a certain reliability) with a parametric equalizer equipped with a number of filters that does not exceed 10/15 filters.
These devices are (if I'm not wrong) the following:
- Truthear x Crinacle Zero: RED
- 7Hz Sealnotes x Crinacle Zero:2
- Moondrop Chu II
Of these, the Zero:RED are the least comfortable in terms of size/encumbrance and weight. They are also two-way IEMs, so with all the problems associated with passive crossover filters (phase shifts in the crossover area, etc.) and they are reactive loads very far from an ideal purely resistive load that greatly helps the stability of the entire reproduction system. They also have a very low impedance that can overload the headphone power output stage. Finally, they are the most expensive of the three models listed.
The 7Hz Selanotes x Crinacle Zero: 2 seem to be the best (lowest THD overall, highest impedance than the others, practically resistive load), but they cost about double the Moondrop Chu II, are bulkier, heavier and their pads are less comfortable (at least in my opinion).
The Moondrop Chu II distort a little more than the 7Hz, but they are smaller, weigh less and (again in my opinion) are more comfortable. They have a constant impedance, so they are practically resistive loads. Their sensitivity is not too high to make the noise floor of the headphone amplifier's output stage audible, and it is not too low to make them unusable in portable applications. They are also the ones that cost the least.
I don't understand why they shouldn't be suitable to approximate the HK IE 2019 v.2 curve. Any other suggestions?
Crinacle measurements are often performed on multiple samples of the same IEMs model. They are performed with B&K 5128/4620 instruments which at the moment seem to be the closest to the (average) human ear available.
If we want to question the H&K curve, we can do so, but what objective reference do we then consider to establish the quality of an earphone? Personal taste? So do we indulge in total subjectivism? Maybe we go back to the loudness control of the 70s?

 

[gcompari]

Doesn’t this indicate some kind of an Android (or Android customization) problem? How would Chu II “know” that you were playing something through UAPP?
I don’t know enough about Android, but on Windows for example, a “headset” is not the same thing as a “headphones”, could it be an Android/Chu II configuration problem and the “assumptions” made by Android about the device?

Doesn’t this indicate some kind of an Android (or Android customization) problem?

Why all the smartphones tested work with Meizu HiFi DAC e Meizu HiFi DAC Pro that are always USB ADC/DAC?

How would Chu II “know” that you were playing something through UAPP

Because UAPP force the Chu II DSP to switch to 96/24 or 88.2/24 thare aren't "native" modes in Android.

I don’t know enough about Android, but on Windows for example, a “headset” is not the same thing as a “headphones”

This is valid for BT devices: for USB ADC/DAC there is no such distinction.

 

[CedarX]

I don't understand why they shouldn't be suitable to approximate the HK IE 2019 v.2 curve. Any other suggestions?

I understood your statement “it takes 13 filters with attenuation…” as dismissing the Chu-II DSP and its 5 peak filters only. I believe 5x filters is enough to reasonably approximate the HK IE 2019 v.2… and start from there to adjust to your own preference.

Why all the smartphones tested work with Meizu HiFi DAC e Meizu HiFi DAC Pro that are always USB ADC/DAC?

May indicate some compatibility or limitations of the Chu-II DSP chip (KTmicro I believe…).

Because UAPP force the Chu II DSP to switch to 96/24 or 88.2/24 thare aren't "native" modes in Android.

And…? I would personally accept a mandatory disconnecting/reconnecting of the Chu-II to re-enable phone calls… But I humbly admit I seldom use my phone for phone calls nowadays!

 

[gcompari]

I understood your statement “it takes 13 filters with attenuation…” as dismissing the Chu-II DSP and its 5 peak filters only. I believe 5x filters is enough to reasonably approximate the HK IE 2019 v.2… and start from there to adjust to your own preference.

May indicate some compatibility or limitations of the Chu-II DSP chip (KTmicro I believe…).


And…? I would personally accept a mandatory disconnecting/reconnecting of the Chu-II to re-enable phone calls… But I humbly admit I seldom use my phone for phone calls nowadays!

This is my approximation.
The parameters are:
PK Fc 20.00 Gain 1.25 Q 1.00
PK Fc 60.00 Gain -1.20 Q 1.80
PK Fc 120.00 Gain -1.00 Q 4.00
PK Fc 180.00 Gain 2.20 Q 1.40
PK Fc 600.00 Gain -2.00 Q 0.70
PK Fc 2200.00 Gain -1.00 Q 2.00
PK Fc 6150.00 Gain -6.40 Q 2.20
PK Fc 8600.00 Gain 3.20 Q 3.50
PK Fc 9700.00 Gain -2.90 Q 3.40
PK Fc 12300.00 Gain 10.50 Q 3.00
PK Fc 14000.00 Gain -4.00 Q 5.40
PK Fc 16800.00 Gain 5.75 Q 1.90
PK Fc 18700.00 Gain -10.00 Q 2.80
to compensate the deviation from the HK curve, just invert the gain signs.

 

[gcompari]

I understood your statement “it takes 13 filters with attenuation…” as dismissing the Chu-II DSP and its 5 peak filters only. I believe 5x filters is enough to reasonably approximate the HK IE 2019 v.2… and start from there to adjust to your own preference.

May indicate some compatibility or limitations of the Chu-II DSP chip (KTmicro I believe…).


And…? I would personally accept a mandatory disconnecting/reconnecting of the Chu-II to re-enable phone calls… But I humbly admit I seldom use my phone for phone calls nowadays!

The problem is the CDSP cable, not the Chu IIs.

 

[markanini]

Among the Audio Science Review tests I found only 3 transducers from electrical signal to acoustic pressure that have the following characteristics:
- THD always less than 1% at any audible frequency at any sound pressure up to the maximum bearable for the human ear.
- Possibility of equalization by very high approximation of the Harman Kardon IE 2019 v.2 curve (I believe the latest available with a certain reliability) with a parametric equalizer equipped with a number of filters that does not exceed 10/15 filters.
These devices are (if I'm not wrong) the following:
- Truthear x Crinacle Zero: RED
- 7Hz Sealnotes x Crinacle Zero:2
- Moondrop Chu II
Of these, the Zero:RED are the least comfortable in terms of size/encumbrance and weight. They are also two-way IEMs, so with all the problems associated with passive crossover filters (phase shifts in the crossover area, etc.) and they are reactive loads very far from an ideal purely resistive load that greatly helps the stability of the entire reproduction system. They also have a very low impedance that can overload the headphone power output stage. Finally, they are the most expensive of the three models listed.
The 7Hz Selanotes x Crinacle Zero: 2 seem to be the best (lowest THD overall, highest impedance than the others, practically resistive load), but they cost about double the Moondrop Chu II, are bulkier, heavier and their pads are less comfortable (at least in my opinion).
The Moondrop Chu II distort a little more than the 7Hz, but they are smaller, weigh less and (again in my opinion) are more comfortable. They have a constant impedance, so they are practically resistive loads. Their sensitivity is not too high to make the noise floor of the headphone amplifier's output stage audible, and it is not too low to make them unusable in portable applications. They are also the ones that cost the least.
I don't understand why they shouldn't be suitable to approximate the HK IE 2019 v.2 curve. Any other suggestions?
Crinacle measurements are often performed on multiple samples of the same IEMs model. They are performed with B&K 5128/4620 instruments which at the moment seem to be the closest to the (average) human ear available.
If we want to question the H&K curve, we can do so, but what objective reference do we then consider to establish the quality of an earphone? Personal taste? So do we indulge in total subjectivism? Maybe we go back to the loudness control of the 70s?

I owned all three IEMs and TE Red was by far the most comfortable to me. Comfort is individual though due to varying anatomy. I don't think 2DD is problematic for the reasons of phase shifts. Becuase, phase shifts are a reason why EQ works fundamentally, and you seem ok with using EQ. It's also part of how various speakers recommended by Amir work. The only sure way you will know how much the issues you are concerned about affect you is to personally evaluate each IEM by physically fitting them.

 

[Tell]

How loud can these go? I'm curious about these since it would be nice to have a pair of headphones with inbuilt DSP, but I don't want them to play softer than what my Zero2 + JM20 can do. Anyone knows?

 

[Zarniwoop]

Where is the currently selected EQ stored? Is it in the cable itself? And therefore the sound is carried to whatever device it is plugged into?

 

[Emlin]

Where is the currently selected EQ stored? Is it in the cable itself? And therefore the sound is carried to whatever device it is plugged into?

Yes on both counts.