Hey folks,
It is time for my first review of 2023... This one is about a complete objective analysis of the new
WiiM Pro streamer. The aforementioned has been recently announced, back in December 2022, and I can see quite a strong hype around it since. That is really not surprising : the WiiM Pro comes with a lot of promises : It is claimed to be a "bitperfect" streamer transport, as was
the WiiM Mini, now with the addition of cool features, like some S/PDIF pass-trough, Google Chromecast built-in, or (yet to be added) Multiroom and Roon Ready support.
At only 179€, it may sound like real bargain, especially when considering this could be the cheapest Roon Ready product ever. It is important to point out that the latter function is still not available by the time of this writing, even after the last (02/15/2023) update. The WiiM team publishes and constantly updates
their roadmap on their website (which is rather uncommon from most manufacturers, and as such, welcomed), and the WiiM Pro appears to be currently under certification with Roon. Please note that Roon users may already use the WiiM Pro, when selecting it as a Roon Endpoint (through Chromecast).
These asides, it mostly has the same features, and presumably the same DAC and ADC chips, as the WiiM Mini, but with extended connectivity. By bringing such a complete unit to the market, there is no doubt that WiiM is aiming to compete against well-installed and popular products like the Bluesound Node, but at almost 1/4 of the price. Speaking of price, I bought myself this sample, tested today, on Amazon. By the way, availability is yet to be optimized, especially in EU.
The WiiM Pro comes in a little and quite light plastic box. While I did not expect much in terms of overall build and finish, considering the features/price ratio, I am still kind of disappointed. The plastic feels a bit cheap on touch and I don't like the grey tone and texture. However, I appreciate the non-slip covering beneath it, that allows the unit to remain stable when plugging cables or using the touch buttons. As you can see, these are four, for either volume control up and down, play/pause and preset. I found them to be decently responsive, but pressing them doesn't display anything, unless the main LED that is blinking. Not sure if these will be used much, since the unit has to be entirely controlled by the App anyway.
View attachment 265797
On the back, I am please to see a rich connectivity for such a small unit. We got both RCA inputs and outputs, two optical sockets (in and out), one coaxial output, a 12V trigger out, wired LAN input, and a mic, probably to be used for Alexa or any assistant (I do not use these). The power is done by the USB-C input (USB cable and 5V/2A adapter supplied). I also like to not have any antenna, when knowing the WiiM Pro also supports both Wi-Fi and Bluetooth. By the way, I encountered no range issues, cuts, nor skipping, when using these two wireless inputs. It supports up to 24bits / 192kHz with Wi-Fi, Optical and Coaxial or 96kHz for Chromecast. Bluetooth (5.1) is unfortunately limited to AAC and SBC codecs.
This is how the WiiM Home App looks like :
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While this review is largely measurements-based, I used the WiiM Pro in my system during about a week, which is enough to share my two cents. I liked using it. It worked. That is it.
More seriously, yes, I have to admit I was a bit scared about getting something... more flawed. When you launch such a packed product at this price, then compromises are done, and software is usually the first victim... Well, not here ! The app is overall pleasantly stable and smooth. I like to see some cool additions like the bitrate to be displayed (like does UAPP). What I did not was the absence of "melting" artists and albums between different streaming services (as does Roon) when using the search button. I would also wish for a clearer way of displaying outputs and inputs settings. Apart from that nitpicking, WiiM Home does not compare unfavourably to other ecosystem on the market like BluOs, HEOS, MusicCast, StreamMagic and so on. In fact, I even preferred it over some of the aforementioned.
WiiM Home asides, the WiiM Pro (through Chromecast) worked flawlessly when controlled by either Tidal Connect, Qobuz Connect, and Roon.
These being said, it is now time for...
Measurements
Disclaimer: Measurements you are about to see are not intended to be as precise or extensive than what you get from a 30k€ AP. There is obviously both hardware and software limitations here, so not quite apples to apples comparison with Amir's testing. Still, this data is enough to have a pretty good idea if the gear is bad or not, stellar, broken, or sub-par...
- Instruments : E1DA Cosmos ADC (Grade B). Minimum phase filter. A newcomer is the RME ADI-2/4 PRO SE, which, 1) does a better job measuring unbalanced and low level signals, 2) may record and measure digital signals. E1DA Cosmos APU 60dB preamp is used for DR measurements. Output voltage is measured separately, using a DMM with a 0dBFS 1kHz tone.
- Software : REW V5.20.14, Multitone Loopback Analyzer 1.0.74 and RMAA 6.4.5 PRO,
- Method : 8 runs for each test, then I choose the closest to the average. Bandwidth and sampling rate to be specified for each test.
- WiiM Pro is running 4.8.507636 firmware. Output, input and setting to be specified below.
Let's start with the DAC performance. For this first battery of tests, I measured the WiiM pro through its RCA output, set at fixed level, 2Vrms. Digital input is S/PDIF optical.
WiiM Pro - DAC Summary
Tests | Results | Rating |
Frequency Response 40Hz; 15kHz | -0.02; +0.05dB | Very Good |
Noise Level (REW) | -110.9dBA | Very Good |
Dynamic Range (REW) | 104.3dB | Good |
THD (REW) | 0.003427% | Good |
THD+Noise / SINAD (REW) | -88.8dB | Subpar |
IMD SMPTE (REW) | -77.5dB | Subpar |
Stereo crosstalk (RMAA) | -109.8dB | Very Good |
IMD+Noise at 10 kHz (RMAA) | 0.0118% | Average |
Multitone 64 TD+N (Multitone) | -82.9dB | Average |
Note: In addition to the supplied USB adapter, I also tested the WiiM Pro with two different USB chargers, from either Google Pixel or Xiaomi, then with a 5V/2.4A battery/power bank. So far, I measured absolutely no difference to speak about (at least not in the 20Hz-20kHz range). That being said, every measurement to come have all been done with the battery.
Note: SINAD performance is 100% the same when using the Wi-Fi input.
What to say? The whole performance seems to be very similar to WiiM Mini, apart from Dynamic Range. Meaning: not quite OK. Overall, while far from being catastrophic, we are expecting much better by 2023 standards. Yes, some may point to the price, but no, we have seen cheaper unit performing better than this. Yes, not as features-packed, but at least suitable/transparent enough for 16 bits, what is not even the case here. At least, I cannot point one particular result showing a "broken" product (except IMD VS Level that is particularly poor, though) I would say that it is "cohesively subpar" performance... But, at least, the results are still a bit above manufacturer's specs: -86dB THD+N, 102dB SNR.
Line Out Level
The WiiM Pro also comes with four selectable (fixed) output levels. While I did not test precisely the behaviour of digital attenuation at different level in the analog domain, (but I did catch THD+N at different digital volume below), I measured each of the output settings and expected a logical drop in performance. Yet, for some reason, the opposite happened:
2Vrms : -88.8dB THD+N
1Vrms : -92.8dB THD+N
800mV : -93.1dB THD+N
500mV : -93.2dB THD+N
Finally, the best performance I could have measure out of the DAC has been when set at 0.5Vrms:
Total Harmonic Distortion + Noise (SINAD) - 24b/44.1kHz
ADC Performance
For these next bunch of tests, I compared the exact same analog signal, which is the RCA output of my Matrix Mini-i Pro 3, first measured by the ADC of the ADI-2/4 PRO SE, then measured by the ADC of the WiiM Pro (and finally, the latter digitally recorded by the ADI-2/4 through S/PDIF). The obvious purpose is to observe how the WiiM Pro performs against a much higher end ADC. While being not Sate Of The Art, I considered the Matrix to be clean enough (about 109dB SINAD, SE) to not bottleneck the ADC performance of the WiiM Pro. And trust me, it did not !
Note: The WiiM pro cannot handle input signals when slightly above 1Vrms, which is according to manufacturer's specs. After quite a few tests, I lowered the Matrix's output down to 1.05Vrms to get the best case scenario in terms of performance.
WiiM Pro - ADC Summary
Tests | Reference 1.05Vrms output | ADC |
Frequency Response 40Hz; 15kHz | +0.01, -0.02 | +0.01, -0.05 |
Noise level | -115.1dBA | -97.1dBA |
Dynamic range | 113.5dB | 92.4dB |
THD + Noise / SINAD | -109.8dB | -88.8dB |
IMD SMPTE | -103.5dB | -80.2dB |
Stereo crosstalk | -115.3 | -84.7 |
Note: It appears that the WiiM Pro's ADC is using internal sampling to 48kHz, according to frequency rate displayed on the ADI-2/4. As such, measurements you are about to see are all done at 24bits / 48kHz.
Ouch. That really is not great, and seems to be on par with @amirm measurements of the WiiM Mini ADC. This is the best performance that I could measure. When feeding the ADC with a slightly stronger signal (1.09Vrms), the performance degrades only by a few dB. However, we start to see the ADC clipping when reaching about 1.20Vrms. Above, we enter this scenario:
Needless to say, it is completely unusable. Which is a shame, when we know that the vast majority of analog sources out there are often rated 2V output voltage, not to mention without variable output... So if you planned to pair the WiiM Pro with, say, a regular CD Player, you will have to use the S/PDIF input or just forget about it...
There is some 0.4dB loss in amplitude over the original measured signal. It is still fair and most likely flat from 20H to 20kHz.
Note: This is measured without the Cosmos APU, due to wiring limitations. Still enough to observe Dynamic Range differences between both ADC.
Wow. This last one is a complete failure. I had to double-check this J-test several times to understand how it could be so wrong, but no, this is what you get after WiiM A/D conversion. Some may think the S/PDIF output of the WiiM Pro to be responsible, but it is not, as you will see later.
Overall, this is indeed a bad performance. I would personally not pair any analog source to this product, unless some (already poor) signal out of a phono preamp.
By the way, in case some may think about using it as an analog hub, this is the performance when using Line In straight to Line Out:
Total Harmonic Distortion + Noise (SINAD) - 24b/44.1kHz
View attachment 266502
Alright, now we are entering a much more interesting (and cleaner) area. Because I assume that many WiiM Pro owners are intending to use it mostly as a digital hub, paired with a much better DAC than what we have seen above. (in fact, you all have to!). These next tests have all been done without A/D conversion and are 100% in the digital domain. I used either REW tone generator for S/PDIF inputs, or WAV test files tones from the Audio Precision's tone generator, then played through the WiiM Home App, or Roon. Results are directly recorded through S/PDIF with the ADI-2/4 Loopback.
Note: To state the obvious, zero difference has been observed between wired LAN and Wi-Fi connection (literary no reason there would). All tests have been done with Wi-Fi.
Let's start with the regular main (Wi-Fi) input:
As we might expect from any decent unit, we got a textbook, absolutely perfect 1Khz signal, with distortion and noise out of this world. Nothing to worry about if you plan to use the WiiM Pro that way. The rest will be up to your own DAC.
By the way, just for peace of mind, this is how the SMPTE IMD looks like :
Intermodulation Distortion SMPTE - 24b/44.1kHz
View attachment 266504
Chromecast
Since the WiiM Pro does have a Google Chromecast bluit-in, that uses different protocols than the WiiM App, we have to check its specific behaviour. To do so, I used a 44.1kHz 0dBFS sine wav, played through Roon (and WiiM Pro Chromecast as a Roon Endpoint). We got this:
Note: This test has been done again after the latest update. Before that, Chromecast's performance was much worse (
see there).
S/PDIF pass-trough
I also checked both optical and coaxial outputs, hardly trying to find any difference...
Note: I have read and heard some early adopters complaining about the S/PDIF showing some delay, for instance when used with a TV optical output. I noticed nothing of the sort (LG OLED C2), so my guess is that it has been fixed since.
Speaking about it, here are the jitter plots for both:
When EQ is set On, it widely affects performance:
Obviously, you do not want to use EQ at fixed volume, unless 57dB SINAD (before D/A conversion) is something you are looking for... It becomes way cleaner with volume is unlocked, the lowered at about 95%. This issue could be easily fixed by firmware, by setting max volume about 1dBFS down.
Bluetooth
For the last graph of all, let me introduce this horror show:
What a shame that the WiiM Pro does not support aptX HD or LDAC... These results are to be expetced and share the same profile than seen in
@amirm measurments there (with even a touch worse implementation).
Digital Volume
Last but not least, a quick world about digital volume implementation. This is what I get when measuring the same 1kHz tone (Wi-Fi In, 44.1kHz) at different levels:
Fixed: -141.8dB THD+N
≃75%: -138.2dB THD+N
≃50%: -131.5dB THD+N
≃25%: -115.5dB THD+N
≃10%: -99.6dB THD+N
...Well, that is enough data for today! As I do not use these at all, I missed either DLNA and Airplay, but you have to expect 16bits/48kHz limitation for the latter. In my humble opinion, that would make no sense to use it over Chromecast.
Conclusions
I will try to isolate both my subjective thoughts and objective findings each others for a little... If looking only at overall pure performance, the WiiM Pro is kind of a mess. While not being the worst I have seen, the DAC portion is nothing near suitable for 24 bits content, far from what we should expect from a product launched in late 2022 (at whatever price), and actually surpassed by some dongles. The ADC is even weaker, not to mention almost useless if you do not have a variable output, thanks to its 1Vrms rated max input. Among other scenarios, it will probably not degrade (even more) some phono signal, but what would be the point to use a turntable for ending in the digital domain that way? You vinyl guys tell me...
On the other hand, we got the digital side. First, the app is cool, it works great, without noticeable bugs or lags. I enjoyed using it on a daily basis. Then, we have the unquestionable performance. It is indeed perfectly transparent when using Wi-Fi, and remains always stable even when streaming 192kHz tracks. The S/PDIF inputs/outputs are a great addition if you want, like me, a streamer feeding your DAC (with only one optical input), that may also catch a signal from a TV or another source. If I forget the (expected to be) poorly Bluetooth measurements, all digital inputs just work and measure great. Chromecast is one of the best addition over the regular WiiM Mini, since you may choose to bypass the WiiM Home App, using either Roon, or any major streaming service's dedicated app. I am personally still waiting for Roon Ready update, and would be glad to re-measure if the digital performance remains the same that way.
Weighting the pros and cons, I will give the WiiM Pro my recommendation, based on how I would (and will!) use it for myself. For the price, it just does its job, and in a great manner. Period.
Flanker rating:
WiiM Pro (analog in & out): Mediocre
WiiM Pro (digital transport): Excellent
