WiiM Amp Pro Streaming Stereo Amplifier Review

[Old_School_Brad]

In the video, the transients hit 750W but the average output is around 350W so it means twice the average power as headroom for those transients. In such system one clearly needs a lot of power... I wish I could afford such pair of speakers.



Agree, music can be really dynamic but a decent amp should be able to handle that.

I do not want to keep deviating the focus from the main topic of this thread. Sorry if I offended you and enjoy your music!

A good pair of speakers should have a high transient capability since it only needs to handle these peaks for brief moments. The reason I quickly opened my app for my first post is because the track I was measuring isn’t what you'd typically consider a highly dynamic piece of music. It’s a fairly standard EDM/pop track with (in my opinion, great) vocals from Sia, but otherwise nothing extraordinary. That, in itself, says more than "test track" from the video Doodski linked to. At least I tend to think so.
With this in mind, it's worth considering whether you'd be satisfied with a peak power capability of 50W.

 

[shuppatsu]

The test speakers in the video are Harbeth Monitor 40.1 speaker with 85dB/W/m efficiency or sensitivity. They have the same sensitivity rating as your speakers. The average output is most likely not 350W/ch otherwise the people in the video would be unable to speak to each other. You should check your facts and figures before posting.

I don't know what's going on in that video, but I do see people getting up really close to it, like their ear pointed directly at the speaker at 1-2 feet. All I can say is that my 87dB speakers at 3 feet away are instant panic turn down loud with my Wiim Amp at 100%.

One of the comments says that the CH Audio meters are not accurate in bridged mode. Maybe that's what's going on?

EDIT: I don't have a lossless version of the song but the official Youtube Opus track (143kbps) has an RMS of -12.5dB, which is not a particularly dynamic track.

 

[Doodski]

I don't know what's going on in that video, but I do see people getting up really close to it, like their ear pointed directly at the speaker at 1-2 feet. All I can say is that my 87dB speakers at 3 feet away are instant panic turn down loud with my Wiim Amp at 100%.

One of the comments says that the CH Audio meters are not accurate in bridged mode. Maybe that's what's going on?

EDIT: I don't have a lossless version of the song but the official Youtube Opus track (143kbps) has an RMS of -12.5dB, which is not a particularly dynamic track.

I think the track they are using is very bass heavy and thumpy sounding so the volume does not need to be very loud to get the high peak power. I agree that at the distance they are at if it was a song that went loud and did not have those bass thumps that it would be unbearably loud. Keep in mind that most of the energy is coming from the woofers with that track and that means large power reserves are required even if it does not seem really loud. I don't think the meters are out of line.

 

[Doodski]

@shuppatsu maybe by looking at the voltage and current from the amplifiers will put into perspective the difference.

Wiim pushes 59WRMS@8R and so that means there is a ~ +/- 30.7 Volts DC power supply in the device for the speakers. So the current at peak output will be ~+/- 3.8A

The big monoblock power amps in the video test are seen to peak at 750WRMS. So the voltage output there will be ~ +/- 109.5 V peak @ +/- 13.7A peak.

 

[shuppatsu]

I think the track they are using is very bass heavy and thumpy sounding so the volume does not need to be very loud to get the high peak power. I agree that at the distance they are at if it was a song that went loud and did not have those bass thumps that it would be unbearably loud. Keep in mind that most of the energy is coming from the woofers with that track and that means large power reserves are required even if it does not seem really loud. I don't think the meters are out of line.

I don’t understand, which could be a me problem. It is a very bass-heavy track for sure, with lots of subbass that my bookshelfs can’t reproduce (a very different experience with my IEMs, makes it almost enjoyable). But I turned off EQ and the subwoofer crossover, so the amp is pumping out those watts regardless. And it’s the midrange “melody” pulse that is unbearably loud. So I just don’t know how they stand to get their ears so close to the speakers.

 

[Doodski]

I don’t understand, which could be a me problem. It is a very bass-heavy track for sure, with lots of subbass that my bookshelfs can’t reproduce (a very different experience with my IEMs, makes it almost enjoyable). But I turned off EQ and the subwoofer crossover, so the amp is pumping out those watts regardless. And it’s the midrange “melody” pulse that is unbearably loud. So I just don’t know how they stand to get their ears so close to the speakers.

The energy in the audio stream going to the speakers is mostly comprised of very low frequency energy. So the mid and high frequency energy is lower with this audio track than is found most of the time with most music tracks. So when the energy stream gets to the speaker it gets divided up by the crossover between the 3 drivers in the speaker and because most of the energy is very low frequency the majority of that energy only goes to the woofer and that makes the sound pressure level from the mids and tweeters not anywhere near as loud.

 

[Old_School_Brad]

I don’t understand, which could be a me problem. It is a very bass-heavy track for sure, with lots of subbass that my bookshelfs can’t reproduce (a very different experience with my IEMs, makes it almost enjoyable). But I turned off EQ and the subwoofer crossover, so the amp is pumping out those watts regardless. And it’s the midrange “melody” pulse that is unbearably loud. So I just don’t know how they stand to get their ears so close to the speakers.

How do you figure how loud you should have it to compare with the video?

 

[shuppatsu]

The energy in the audio stream going to the speakers is mostly comprised of very low frequency energy. So the mid and high frequency energy is lower with this audio track than is found most of the time with most music tracks. So when the energy stream gets to the speaker it gets divided up by the crossover between the 3 drivers in the speaker and because most of the energy is very low frequency the majority of that energy only goes to the woofer and that makes the sound pressure level from the mids and tweeters not anywhere near as loud.

This comports with my understanding. What I'm saying is that the midrange is unbearably loud with my Wiim Amp. Even without a lot of the subbass in the track that my speaker can't reproduce, the C-weighted peak (using my iPhone) from ~3ft was 109.7dB at 100%. Stupid loud. I had to press my hand against the ear pointing towards it while I took the measurement and it was still unbearable for more than a few seconds. Again, that's with EQ and subwoofer crossover both disabled, so the amp is wasting watts on the subbass even if I can't hear it.

How do you figure how loud you should have it to compare with the video?

Those duffers are hanging out like 1-2 feet from the speaker with their ear pointed directly at the speaker. Granted those speakers are 2dB quieter than mine, but 700W vs ~100W (6ohm nominal) should make up the difference and then some. I don't know how they bear it unless there's something going on that I don't understand.

EDIT: One funny thing is that one of my speaker grills is loose and when I blast the bass it literally gets blown off!

 

[Old_School_Brad]

This comports with my understanding. What I'm saying is that the midrange is unbearably loud with my Wiim Amp. Even without a lot of the subbass in the track that my speaker can't reproduce, the C-weighted peak (using my iPhone) from ~3ft was 109.7dB at 100%. Stupid loud. I had to press my hand against the ear pointing towards it while I took the measurement and it was still unbearable for more than a few seconds. Again, that's with EQ and subwoofer crossover both disabled, so the amp is wasting watts on the subbass even if I can't hear it.


Those duffers are hanging out like 1-2 feet from the speaker with their ear pointed directly at the speaker. Granted those speakers are 2dB quieter than mine, but 700W vs ~100W (6ohm nominal) should make up the difference and then some. I don't know how they bear it unless there's something going on that I don't understand.

EDIT: One funny thing is that one of my speaker grills is loose and when I blast the bass it literally gets blown off!

We can't accurately compare C-weighted SPL levels unless all systems being compared can reproduce a full-range sound. Without that, the numbers wouldn't provide meaningful conclusions.

 

[Doodski]

This comports with my understanding. What I'm saying is that the midrange is unbearably loud with my Wiim Amp. Even without a lot of the subbass in the track that my speaker can't reproduce, the C-weighted peak (using my iPhone) from ~3ft was 109.7dB at 100%. Stupid loud. I had to press my hand against the ear pointing towards it while I took the measurement and it was still unbearable for more than a few seconds. Again, that's with EQ and subwoofer crossover both disabled, so the amp is wasting watts on the subbass even if I can't hear it.


Those duffers are hanging out like 1-2 feet from the speaker with their ear pointed directly at the speaker. Granted those speakers are 2dB quieter than mine, but 700W vs ~100W (6ohm nominal) should make up the difference and then some. I don't know how they bear it unless there's something going on that I don't understand.

EDIT: One funny thing is that one of my speaker grills is loose and when I blast the bass it literally gets blown off!

Yes, that is very very loud for a Wiim although it does not recreate the audio system that is used in the video. There are too many differences between your speakers and the speakers in the video and the speaker(s) impedances to go cranking your Wiim system to a very loud level and expect the same results without the bass capability of the Harbeth speakers. As you think and I think too that it seems very unlikely that the demonstration is going to 109'ish dB continuously while those guys are conversing and listening then the power can only be mostly in the low frequencies where it is not obnoxiously overbearingly loud to out ears and still requires high peak power to avoid clipping. The only remaining reason that comes to mind is that the Harbeth speakers are recreating very low bass and lots of it via the amp's high peak output without clipping so that the total volume of sound is not seemingly super loud due to it being low frequency stuff and possibly the Harbeth speakers are a very reactive load too. I have not seen a impedance graph for the Harbeth Monitor 40.1 speakers (I will Google that and provide a graph at the end of this commentary.). Keep in mind also that large increases in power output are required for a noticeable increase in the volume as well as low frequency output requires high power so seeing ~750W peak out of a capable amplifier is not unheard of nor a very rare thing. Remember that to double the sound pressure level one needs a very significant increase in power (10x more power.) As you can see the Wiim will go loud and we knew that from the beginning but it does not have the very high peak power output for demanding speakers with a low impedance(Z) and lots of inductive and capacitive reactance. The initial dB output commentary confirmed that the Wiim will get a system most of the way to loud sound with it's 59Wrms@8R and the rest when using monster amps is gravy on the top for difficult speakers and providing low low bass output for full high fidelity.

Upon looking at a impedance versus phase graph I am not seeing a really really difficult load with the Harbeth Monitor 40.1 speakers so the test amps 750 Watts peak power can only be attributed to low low frequency bass and high peak power required to reproduce that in a very dynamic way while providing the transients that the music is capable of.

 

[Old_School_Brad]

The demonstration is far from reaching an average SPL of 109 dB; this value represents a peak level. From my experience with my own system, playing this track, an A-weighted SPL around 70 dB would correspond to approximately 110 dBC, assuming linear scaling of speaker and amplifier capabilities across the entire frequency range.

At 70 dBA, people would need to raise their voices to hold a conversation, but due to the transient nature of this specific track, it might be possible to converse even at higher measured levels than one would expect.

 

[shuppatsu]

Yes, that is very very loud for a Wiim although it does not recreate the audio system that is used in the video. There are too many differences between your speakers and the speakers in the video and the speaker(s) impedances to go cranking your Wiim system to a very loud level and expect the same results without the bass capability of the Harbeth speakers. As you think and I think too that it seems very unlikely that the demonstration is going to 109'ish dB continuously while those guys are conversing and listening then the power can only be mostly in the low frequencies where it is not obnoxiously overbearingly loud to out ears and still requires high peak power to avoid clipping. The only remaining reason that comes to mind is that the Harbeth speakers are recreating very low bass and lots of it via the amp's high peak output without clipping so that the total volume of sound is not seemingly super loud due to it being low frequency stuff and possibly the Harbeth speakers are a very reactive load too. I have not seen a impedance graph for the Harbeth Monitor 40.1 speakers (I will Google that and provide a graph at the end of this commentary.). Keep in mind also that large increases in power output are required for a noticeable increase in the volume as well as low frequency output requires high power so seeing ~750W peak out of a capable amplifier is not unheard of nor a very rare thing. Remember that to double the sound pressure level one needs a very significant increase in power (10x more power.) As you can see the Wiim will go loud and we knew that from the beginning but it does not have the very high peak power output for demanding speakers with a low impedance(Z) and lots of inductive and capacitive reactance. The initial dB output commentary confirmed that the Wiim will get a system most of the way to loud sound with it's 59Wrms@8R and the rest when using monster amps is gravy on the top for difficult speakers and providing low low bass output for full high fidelity.

Upon looking at a impedance versus phase graph I am not seeing a really really difficult load with the Harbeth Monitor 40.1 speakers so the test amps 750 Watts peak power can only be attributed to low low frequency bass and high peak power required to reproduce that in a very dynamic way while providing the transients that the music is capable of.

The track definitely has tons of low bass content:

But my PSBs have much lower impedance at these low frequencies than the Harbeths, meaning they would use more power, right? For example, the most energy is at 50Hz, and my PSBs are at 6ohms at 50Hz whereas the Harbeths are literally off the chart! So again, wouldn't the Wiim be spending tons of its power trying (in vain) to recreate those low frequencies?

 

[shuppatsu]

The demonstration is far from reaching an average SPL of 109 dB; this value represents a peak level. From my experience with my own system, playing this track, an A-weighted SPL around 70 dB would correspond to approximately 110 dBC, assuming linear scaling of speaker and amplifier capabilities across the entire frequency range.

At 70 dBA, people would need to raise their voices to hold a conversation, but due to the transient nature of this specific track, it might be possible to converse even at higher measured levels than one would expect.

Maybe your system goes down really low. Mine doesn't, no subwoofers.

Maybe I'll remeasure and note more things, but not tonight with the family in bed. Suffice it to say that it was loud enough in regions that I'm sensitive to that every millisecond that it was on filled me with the urge to turn it off as soon as possible. Painfully loud. I would not be holding any kind of conversation. Maybe in a huge room, but again they literally had their ear right next to the speaker with no apparent discomfort.

 

[shuppatsu]

We can't accurately compare C-weighted SPL levels unless all systems being compared can reproduce a full-range sound. Without that, the numbers wouldn't provide meaningful conclusions.

I’m not sure that I understand. My bookshelf speakers don’t go nearly as low as the Harbeths. All else being equal, the Harbeths would pump out more c-weighted decibels, right? Of course the comparison would not be exact, but we’d know which direction it goes in, right?

 

[Doodski]

@shuppatsu apparently your speakers cannot reproduce the low frequencies and the Wiim if pushed beyond 59 Watts or in Volts 30.7 Volts then it will clip. It's that simple. You may not hear the clipping but it is clipping.

 

[MelodiousThunk]

Thanks for all of the info (even if I do not understand everything). I have a loaner 1st edition WiiM Amp coming sometime this weekend. So, I will give that a whirl. I started to seriously consider the Marantz M1 but then I saw the difference in software. The M1 really seems to be lacking in that department. And, it is lacking a remote. So, now I am undecided again.

 

[Old_School_Brad]

Maybe your system goes down really low. Mine doesn't, no subwoofers.
View attachment 401415
Maybe I'll remeasure and note more things, but not tonight with the family in bed. Suffice it to say that it was loud enough in regions that I'm sensitive to that every millisecond that it was on filled me with the urge to turn it off as soon as possible. Painfully loud. I would not be holding any kind of conversation. Maybe in a huge room, but again they literally had their ear right next to the speaker with no apparent discomfort.

What I’m suggesting is that your C-weighted measurement likely differs from mine because your system may not perform as strongly in the low frequencies, where the track’s power primarily lies. My guess is that if you measured the playback, the difference between the average dBA and the C-weighted peak would be smaller than what I recorded, and that this difference would further decrease as the SPL increases.
Add to that the uncertainties that are room reflections (or lack thereof), room modes and DSP.

I also think Doodski has a valid point: your amplifier might be clipping when the low-frequency bass hits, and you might not notice it because we’re less sensitive to detecting distortion in that frequency range. Given that the bass in this track primarily hits at different times than the other frequencies, it’s quite possible that clipping could occur unnoticed.

 

[Piotr]

The info you guys shared here is a bit over my head, so I’d really appreciate a simpler explanation.

When you say, "The max rated output power is also the max capable peak output power [class D amps]" does this mean that higher-powered class D amps are preferable since class AB amps typically handle peak power better?

I'm also deciding between the WiiM Amp Pro and possibly the M1, and I gather that the best choice largely depends on the speakers. Could you help me understand if Wim Amp would be a better match for the following speakers?

1. Monitor Audio BX2
2. ELAC DBR-62

Currently, I’m using the BX2 with an MCR603, but I’m not satisfied with the sound in my living room. It worked fine in a smaller bedroom, but now it feels muddled – lacking stereo separation, instrument clarity, and depth that I'd expect from a hi-fi system.

Typically listen at low volumes, and if the source and system quality are good, my family also enjoys it. But if anything sounds off, my wife—who’s a musician and highly sensitive to distortion and harsh tones—usually asks to turn it down.

 

[shuppatsu]

@shuppatsu apparently your speakers cannot reproduce the low frequencies and the Wiim if pushed beyond 59 Watts or in Volts 30.7 Volts then it will clip. It's that simple. You may not hear the clipping but it is clipping.

Maybe. My speakers definitely cannot reproduce the low frequencies. I've been saying that over and over again. I don't know if it's clipping. From the (non-pro) review: "Unless you use analog input, the gain settings is designed such that you never clip. This means that the "peak" power is the same as what I have measured above. Spec is 120 watts at 4 ohm and we are achieving that so no issue there. Same with 60 watt specified for 8 ohm." Now, maybe it can't clip on his test, but it can clip if fed a low frequency signal? I don't know enough about audio to know whether that's likely.

What I’m suggesting is that your C-weighted measurement likely differs from mine because your system may not perform as strongly in the low frequencies, where the track’s power primarily lies. My guess is that if you measured the playback, the difference between the average dBA and the C-weighted peak would be smaller than what I recorded, and that this difference would further decrease as the SPL increases.

That's also what I was suggesting when I said, "Maybe your system goes down really low. Mine doesn't, no subwoofers." And showed you the FR graph showing sharp reduction in bass below 60Hz. But we are drawing different inferences from this.

What I'm saying is that all things being equal (it's not, but close enough), the fact that the Harbeth goes down lower means that for the same wattage, my CPeak would be lower than the Harbeths. That means the Harbeths would be pumping out the bass that my system can't handle, plus it would outputting the mids and highs which makes it unbearable for me to listen for more than a second. In reality, my speakers are 2dB more sensitive, so it's a little more complicated than that, but then again 90W and 700W is like a 9dB difference. My point is my setup could be half as loud (9W?) and there's no way I'd be sticking my ears right next to the speaker for any length of time. Yet they are doing this casually in the Youtube video!

It really sounds like I'm against you and Doodski but I'm not. I'm trying my best to understand this stuff, and apart from a brief dalliance 25 years ago I've only gotten into audiophilia in the last year or so. So I'm just trying to expand my mental model by pushing against it.

 

[shuppatsu]

When you say, "The max rated output power is also the max capable peak output power [class D amps]" does this mean that higher-powered class D amps are preferable since class AB amps typically handle peak power better?

Yeah, basically there never was much standardization on max power and manufacturers ran away with their max power claims, so on spec sheets that is highly disfavored. But lost in the mix is that there is such a thing as max power and it is useful! And similarly rated AB amps will have much higher max power than D amps.

If it sounds bad at moderate volume, then your amp should be fine. I'd look into speaker placement and room issues. If it only sounds bad at high volume, then maybe more power would help.