Moondrop Chu II IEM Review

[georgehifi]

Even a slight break in seal though can significantly affect bass levels and I think this is where most of the perception of tip differences on bass come from, it is almost always back to a seal issue. Some tips are even designed with a textured surface, intended to slightly break seal, to slightly reduce bass levels. This sort of works but it's a pretty subtle effect, usually with IEMs it's either sealing or it isn't and you go from full bass or very near to no bass.

Like I said I tried all three sizes, all had the same "slightly light" bass with all of the 3 x gel ear pieces.
I have "maybe" a feeling they "could" be even harder (more current hungry) to drive than what's reviewed here, as my DAB source is up and over 75% volume to get the same volume as my IEM's that came with it, which were only at 50% and over. (making these less musical/enjoyable than the no name IEM's that came with it)

@amirm what source do you use when testing these, what sort of output stage (specs) does it use?

Pocket Portable Digital Radio (RR10) - Richter Audio

The Richter Pocket Portable Digital Radio (RR10) boasts a DAB+ & FM Tuner, large LCD Display, in-built speaker with headphones (included). Check it out....

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Cheers George

 

[georgehifi]

My no name ones that came with the DAB portable seem to be 34ohms (double the impedance easier to drive?? more bass??), and they seem to be ported!!!! maybe that accounts for the better bass?


This looks like it could be them???

 

[markanini]

Like I said I tried all three sizes, all had the same "slightly light" bass with all of the 3 x gel ear pieces.
I have "maybe" a feeling they "could" be even harder (more current hungry) to drive than what's reviewed here, as my DAB source is up and over 75% volume to get the same volume as my IEM's that came with it, which were only at 50% and over. (making these less musical/enjoyable than the no name IEM's that came with it)

@amirm what source do you use when testing these, what sort of output stage (specs) does it use?

Pocket Portable Digital Radio (RR10) - Richter Audio

The Richter Pocket Portable Digital Radio (RR10) boasts a DAB+ & FM Tuner, large LCD Display, in-built speaker with headphones (included). Check it out....

richter.com.au

Cheers George

Have you tested other sources?

 

[amirm]

@amirm what source do you use when testing these, what sort of output stage (specs) does it use?

I use an RME ADI-2 Pro.

 

[georgehifi]

Have you tested other sources?

This Bush/Richter DAB one, beats out any of the phones we have here and other portables we have, but I have other Sennheiser/Sony etc etc IEM's here and they have equal or touch more bass also.

Cheers George

 

[georgehifi]

I use an RME ADI-2 Pro.

Just looking at that it would seem to have far superior output stage for current into 18ohms in it than any phone or portable audio device would have.
Or it's the "port"?? on the no name IEM'S
Cheers George

 

[markanini]

Notice that, for me, Filters 1 & 5 are slightly different from what @markanini got…

Good catch, yikes. I assume a transcription error on my part, I took the values down from a screenshot like yours some time back. Back then I also crosschecked on squig.link and it looked reasonably matched so hopefully not a to big disparity for @herr.jemine

Here's the corrected text version:

Filter 1: ON PK Fc 40 Hz Gain -4.2 dB Q 0.300
Filter 2: ON PK Fc 200 Hz Gain -5.0 dB Q 0.700
Filter 3: ON PK Fc 1400 Hz Gain -2.5 dB Q 1.600
Filter 4: ON PK Fc 3500 Hz Gain -4.8 dB Q 1.000
Filter 5: ON PK Fc 9000 Hz Gain -2.0 dB Q 1.500

 

[amirm]

Just looking at that it would seem to have far superior output stage for current into 18ohms in it than any phone or portable audio device would have.

Correct although my average listening level for an IEM like this is around -40 dB so not remotely using its full power. That said, I am always a fan of using powerful sources and not just relying on a low output dongle or what comes out of a portable device.

 

[posvibes]

I like these very much, with all of my IEM's I use aftermarket silicone triple flange tips and they give me a good fit.

I like all my IEM's from the Truthear's series, I prefer just slightly more the Truthear Zero (blue) to the Moondrop Chu II, the Truthear has a more relaxed presentation.

If only the Truthear's had the same shape and weight of the Moondrops, they would be perfect. But these Moondrops are impressive.

And a shout out to Maikey1976 for his APO EQ settings always good value!
And thanks to Amir, (again) for all of this an island of sanity in an ocean of madness.

 

[Blorg]

@georgehifi It seems like you've never used any other IEM before, those are earbuds and don't rely on a seal. Earbuds have sub-bass roll-off but some of them can be very mid-bassy, I don't know about that one but some of them are incredibly bloated in the mid-bass. So it is possible you are used to excess mid-bass which the Chu II doesn't have, it's more sub-bass focused.

I suspect though it is most likely a seal issue. Sometimes, none of the stock tips will seal with an individual ear and you need to look at aftermarket tips to get a good seal.

I would suggest you try playing a 50Hz tone and then with the best fitting tips you have, physically push them in with your fingers. If the bass goes up when you do this, you have a seal issue. Obviously you can't hold them in all the time, this is just a diagnostic. If the bass increases when you do this, it will also increase if you get an aftermarket tip that seals effectively. If the bass doesn't go up at all, it's probably not a seal issue.

They are not that difficult to drive, few IEMs are, you should get solid bass levels off just about anything. That source might be marginal for high volume listening but you should still be able to hear the bass levels relative to the rest of the FR at lower volumes.

My feeling is, it's more likely to be seal than source. Even a slight seal break on an IEM and the bass disappears entirely, it's critical.

 

[georgehifi]

So it is possible you are used to excess mid-bass which the Chu II doesn't have, it's more sub-bass focused.

No these no name brand ones with "port", are closer sounding to my main man cave system, (and without any bass bloat) and far more musical to listen to, esspecially big orchestral pieces.
Man Cave system: MSB R2R Discrete Dac into monoblock NC500 Hypex (no input buffers/linear supplies) GoldenEar Triton2+ with 2 x servo controlled subs from 30hz down

Cheers George

 

[Blorg]

@georgehifi right, well the Chu II are about +10dB in the sub-bass over the mids, so if you're not hearing the bass you almost certainly have a seal problem. It's unlikely to be faulty IEMs either as when you get faulty IEMs it's very unusual that they'd be faulty in exactly the same way on both sides; if it was an IEM fault they'd almost certainly have bass roll-off on one side but not the other.

I have never seen an earbud that can do sub-bass, I don't believe it's physically possible. So it's unlikely they are doing much of anything at all at 30Hz. This is more typically what earbuds (Moondrop U2) do in the bass, it's totally rolled off due to the lack of a seal. While the Chu goes up. However, an IEM will roll off exactly the same if you don't have a seal, so if you are saying the Chu II has less sub bass than an earbud, you almost certainly don't have a seal.

 

[dzerig]

I have the Chu I but it never fit well in my ears, I will try this though maybe better fit and cheap enough to try.

 

[georgehifi]

What more can I say, both sides are as said "slightly" bass shy in terms of "weight", regardless of which size gel ear seals are used, compared to those other "ported" earbuds I've shown. Like I said maybe it's the Moondrop 18ohms vs the 34ohms of the earbuds that's the problem with current drive.

Cheers George

 

[markanini]

What more can I say, both sides are as said "slightly" bass shy in terms of "weight", regardless of which size gel ear seals are used, compared to those other "ported" earbuds I've shown. Like I said maybe it's the Moondrop 18ohms vs the 34ohms of the earbuds that's the problem with current drive.

Cheers George

Some troubleshooting steps away is likely the bass you are missing if you care to:
Connect to a different output source, like any phone or tablet. (for the purpose of testing)
Manually nudge the shells around until you hear the bass come in. If no change, go up one ear tip size, or down.
Doublecheck that you are orienting the shells and the cable as pictured:

 

[Jimbob54]

What more can I say, both sides are as said "slightly" bass shy in terms of "weight", regardless of which size gel ear seals are used, compared to those other "ported" earbuds I've shown. Like I said maybe it's the Moondrop 18ohms vs the 34ohms of the earbuds that's the problem with current drive.

Cheers George

Just try the alternating tone test here. If not equally loud then it's not a good seal.

Audio Seal Test

The Audio Seal test is designed to help you determine whether your earphones are correctly inserted. The test consists of audibly comparing two tones, one at 50 Hz and the other at 500 Hz, which should be heard at the same level. A weaker low frequency tone indicates a poor ear seal, resulting...

asiaudio.com

 

[georgehifi]

Just try the alternating tone test here. If not equally loud then it's but a good seal

I have a proper Tektronix FR generator both are perfectly equal, they are just not "quite" weighty enough in the bottom end for me, which makes them less "meaty" in the prestation to what I like, which gives gut, body, and musicality to things like cello's etc etc

Cheers George

 

[Oso Polar]

Just try the alternating tone test here. If not equally loud then it's but a good seal

I was surprised that with Chu II I got a good seal with medium tips and very bad, with *zero* bass with large.

 

[Oso Polar]

they are just not "quite" weighty enough in the bottom end

Chu II have significantly more bottom end than any earbuds. Unless you call 200 Hz a bottom end. Most probably you do have seal issues. I certainly had initially.

 

[MacClintock]

I have a proper Tektronix FR generator both are perfectly equal, they are just not "quite" weighty enough in the bottom end for me, which makes them less "meaty" in the prestation to what I like.

Cheers George

Maybe the driver is not yet broken in properly? Do some more 100 hours of listening......