UMIK-1 arrived

[khuntim]

At this Point you could finally try to adjust the Main speaker delay by +/- 1 or 2 ms or change the crossover +/- 5 or 10 Hz.

But always only one or the other, never both at the same time. And only if you feel like tinkering because the latest result doesn't look bad regarding sub integration.

I will try both ideas. sub is tidy now.

as far as the delay, I'm still confused and would like to learn a bit more. maybe someone can point to a basic page on this?

in a 2.0 system using the external mic, all bets are off, no latency without the sub?

 

[Susan’s boil]

‘6.5" only goes so far.’ Ooh matron!

 

[EddNog]

I will try both ideas. sub is tidy now.

as far as the delay, I'm still confused and would like to learn a bit more. maybe someone can point to a basic page on this?

in a 2.0 system using the external mic, all bets are off, no latency without the sub?

Without a sub, there is significantly less concern about synchronization of timing, other than making sure there are no lip sync issues with ARC input. Once you introduce more than a second speaker into the system, synchronization suddenly becomes…well, time-critical.

-Ed

 

[harkpabst]

as far as the delay, I'm still confused and would like to learn a bit more. maybe someone can point to a basic page on this?

in a 2.0 system using the external mic, all bets are off, no latency without the sub?

Sound as we can perceive it is transmitted as longitudinal waves composed of repetitive patterns of positive pressure and negative pressure. Positive and negative are really just relative to the static air pressure, which we cannot sense. These sound waves move at a limited speed, the speed of sound. Roughly 344 m/s at 21⁰ C at sea level might appear pretty fast. But it also means that sound takes 1 ms to travel 34.4 cm. At a distance of 3.44 m between you and a loudspeaker the sound takes 10 ms to travel the distance.

Lets imagine a simple sine tone at 100 Hz. If we stay in a fixed position and capture the sound pressure level over a long enough period of time we will find it follows a mathematical sine function. Zero to maximum to zero to minimum to zero. Repeat. The time needed for a full cycle depends on the frequency. At 100 Hz it's exactly 1/100 of a second because that's the definition of Hz: The number of oscillations per second.

At different positions in the room we would always register the same sine function, but the maximum and minimum values would not occur at exactly the same time because the longitudinall wave really travels through the room. And it does so at - we already know that - 34.4 cm per ms. If we could take a snapshot of the soundwave in the room at a fixed point in time, we would find that it looks like a sine function, too. The distance in space from the initial zero pressure value through max and zero and min to the final zero a tape measure could capture is the wavelength at this exact frequency. At 100 Hz a full cycle has a wavelength of 344 m/s divided by 100 Hz which is exactly 3.44 m. It's the distance sound can travel during 10 ms.

Keep this picture of a sound wave in the room in mind when we add two (or more) sources. The sound waves will interact according to the superposition principle. Depending on how far we are from each source they can either enforce each other or cancel each other out, because the time the sound takes to reach our ears can be different for each source. If the 100 Hz soundwave from one source arrives exactly 5 ms late at your ear compared to the other source they will fully cancel out each other. And yes, this is true even for just two speakers.

But normally, we don't sit 5 ms (equaling 167 cm) further away from one speaker than the other and still expect perfect hi-fi stereo sound. Also, the distance is different for all frequencies, so it's not that much of an issue for the whole spectrum of music. Any delay caused by the processing in our hi-fi gear is usually totally identical for the left and the right channel, so it could only result in lip sync issues with programme material that also features video. No cancellation.

This can change drastically as soon as we add a sub. More often than not it's not placed dead center between the main speakers. And just as important most modern subs employ some DSP, often adding 5 to 10 ms of extra delay to the sound played by the sub. If we do not compensate for this by adding delay to the main speakers, we might end up with perfect cancellation at 100 Hz, very close to the usual crossover frequencies. Some (but not full) cancellation will still happen at frequencies close by.

If you don't sit in the sweet spot exactly, things will change a little, of course, as the distance to the three sources changes. At low frequencies (longer wave lengths) there's less of a difference cause by the same amount of delay. As a result a single sub should not be crossed over too high (you can get away with ~125 Hz in a fully symmetrical setup) and the delay caused by electronics and different distances to the sources must be compensated for.

Someone make a drawing from this wall of text, please.

 

[khuntim]

Helpful!

Is it possible that a microphone could measure this delay, just not the Ultra/UMIK-1 in this case?

If the Ultra has a mic that measures, could I use a long set of RCAs and set the Ultra in in the listening position?

Sync Audio is set at 2ms, this is different than Sub & Speakers sync? Main Speakers Output Latency at 11ms/Sub Latency 0ms

I will see what happens with changing main speaker latency +/- a bit. Easy to save results and go back if worse.

 

[khuntim]

Without a sub, there is significantly less concern about synchronization of timing, other than making sure there are no lip sync issues with ARC input. Once you introduce more than a second speaker into the system, synchronization suddenly becomes…well, time-critical.

-Ed

Haven't had lipsync issues when using the ARC input. I know the Ultra is more of a music streamer, but the ARC works pretty well. So with 2.1 setup I actually get to hear the .1 information in DD 5.1? Seems like it.

 

[harkpabst]

Is it possible that a microphone could measure this delay, just not the Ultra/UMIK-1 in this case?

There are ways to measure this using e.g. REW and the UMIK-1. I'd have to look up a good instructional guide.

If the Ultra has a mic that measures, could I use a long set of RCAs and set the Ultra in in the listening position?

It's possible and it has been done. But it's even more cumbersome than using external software.

Sync Audio is set at 2ms, this is different than Sub & Speakers sync?

Yes, it's different. Sync Audio is for syncing multiple WiiM devices for multi-room music. It aims at having all WiiM play music exactly at the same time.

Main Speakers Output Latency at 11ms/Sub Latency 0ms

Note that you can always enter only one latency value, either for the mains or for the sub.

As soon as you enter a non zero value for sub delay the mains delay will be set.to zero and vice versa. This is not a limitation. You only ever need one of them. In most cases the mains need to be delayed because the sun lags behind. 11 ms is not an ureasonable value but it's impossible to tell if it's ideal from a remote place.

I will see what happens with changing main speaker latency +/- a bit. Easy to save results and go back if worse.

Exactly. It's free and there's nothing to loose.

 

[khuntim]

Agreed; it's baffling.

At this point, I would suggest using a third party app to perform evaluation/analyzation of results. HouseCurve is a good one which utilizes the UMIK-1 and it is free.

-Ed

will HouseCurve determine the latency from the external mic? free/paid version best?

 

[slartibartfast]

will HouseCurve determine the latency from the external mic? free/paid version best?

I assume with Housecurve you would look at the amplitude of the response around the crossover frequency and adjust the delay to achieve a maximum. You can do the same with REW.

 

[EddNog]

will HouseCurve determine the latency from the external mic? free/paid version best?

To determine latency, you need to use REW. You would have to use either Bluetooth or optical input from your computer with the UMIK-1 attached. Sweep range needs to be around the crossover (so if you cross over around 80Hz, use a sweep range like 60-200Hz), use an acoustic timing reference from the nearest speaker, and make sure to disable the actual crossover in Subwoofer settings (subwoofer and speakers should be set to full bandwidth) as well as the speaker or subwoofer delays must be reset to 0ms to get an accurate read. There are tutorials across the web on how to configure REW. Done right, REW tells you the delay in the notes for each sweep. Even the reference speaker will have a delay, you need to subtract that from the delay for all channels. Because you can’t mute any specific outputs, you’ll need to manually connect/disconnect the speaker you’re testing, so using REW as an example let’s say you decide to use left speaker as acoustic reference, first step turn off the subwoofer, set acoustic reference as left channel and playback as left channel, run the sweep (preferably 3 or more times and take an average of the delays indicated), then to measure right speaker, change output to right channel and do it again, your delay should be extremely close to left channel since the speakers should be very close to the same distance to the listening position, then disconnect the right speaker, turn the subwoofer on, and with right channel still set as output run some more sweeps and you’ll have your delay for the sub (since WiiM will sum left and right channels together to send to the sub).

So let’s say left and right sub are about 2ms and subwoofer is 9ms then you want to delay speakers 7ms. Be careful of the direction of the delays, so for example if speakers are -2ms and subwoofer is 9ms then you must delay 11ms.

-Ed

 

[harkpabst]

Be careful of the direction of the delays, so for example if speakers are -2ms and subwoofer is 9ms then you must delay 11ms.

Mathematically I agree. Just how could the delay of the closest speaker come up as negative relative to the acoustic timing reference?

 

[EddNog]

Mathematically I agree. Just how could the delay of the closest speaker come up as negative relative to the acoustic timing reference?

I really don’t know why that happens.

I only know that it does. Both my loudspeakers get negative delay results when I perform this procedure. Positive delays for the three subs (they each have internal DSPs that slow them down ).

-Ed

 

[khuntim]

To determine latency, you need to use REW. You would have to use either Bluetooth or optical input from your computer with the UMIK-1 attached. Sweep range needs to be around the crossover (so if you cross over around 80Hz, use a sweep range like 60-200Hz), use an acoustic timing reference from the nearest speaker, and make sure to disable the actual crossover in Subwoofer settings (subwoofer and speakers should be set to full bandwidth) as well as the speaker or subwoofer delays must be reset to 0ms to get an accurate read. There are tutorials across the web on how to configure REW. Done right, REW tells you the delay in the notes for each sweep. Even the reference speaker will have a delay, you need to subtract that from the delay for all channels. Because you can’t mute any specific outputs, you’ll need to manually connect/disconnect the speaker you’re testing, so using REW as an example let’s say you decide to use left speaker as acoustic reference, first step turn off the subwoofer, set acoustic reference as left channel and playback as left channel, run the sweep (preferably 3 or more times and take an average of the delays indicated), then to measure right speaker, change output to right channel and do it again, your delay should be extremely close to left channel since the speakers should be very close to the same distance to the listening position, then disconnect the right speaker, turn the subwoofer on, and with right channel still set as output run some more sweeps and you’ll have your delay for the sub (since WiiM will sum left and right channels together to send to the sub).

So let’s say left and right sub are about 2ms and subwoofer is 9ms then you want to delay speakers 7ms. Be careful of the direction of the delays, so for example if speakers are -2ms and subwoofer is 9ms then you must delay 11ms.

-Ed

Going to mess with it a bit, I have some active speakers on the way. with the laptop UMIK-1 is seen in REW using USB-C input. I think the calibration file is loaded, not positive.

 

[Öggy]

Hi everyone,


I also used the WiiM Ultra’s automatic synchronization between the sub and the main speakers. If that’s generally inaccurate, I’d like to set the delay manually. However, I’m a bit confused by the math. Could someone explain—based on the attached sketch—how to calculate the correct delay value? Many thanks!

 

[slartibartfast]

Hi everyone,


I also used the WiiM Ultra’s automatic synchronization between the sub and the main speakers. If that’s generally inaccurate, I’d like to set the delay manually. However, I’m a bit confused by the math. Could someone explain—based on the attached sketch—how to calculate the correct delay value? Many thanks!

My delay is set to 6ms based on maximum amplitude at the the crossover frequency and my sub is adjacent to one of the speakers. So I wouldn't just use maths to calculate the value.

 

[dominikz]

Hi everyone,


I also used the WiiM Ultra’s automatic synchronization between the sub and the main speakers. If that’s generally inaccurate, I’d like to set the delay manually. However, I’m a bit confused by the math. Could someone explain—based on the attached sketch—how to calculate the correct delay value? Many thanks!

Looking at your sketch your subwoofer is 1m further away from your listening position compared to either of your main loudspeakers.
Since the speed of sound in air is 343m/s, all else being equal, that means that the sound from the sub would arrive at the listening position about 3ms later compared to the sound from the main loudspeakers.

Calculation: (3m - 2m) / 343m/s = 0,00291...s = ~3ms

If this was the only source of delay you could just delay your main loudspeakers manually by 3ms in the WiiM Home App.

The issue is however that this calculation only works if the sub doesn't have any extra processing delay (e.g. due to ADC/DAC and/or the onboard DSP). This can add an unknown amount of delay to the sound coming from the sub, which you should also compensate for by adding the same amount of delay to the main loudspeakers.

You can try one of the following procedures to find the total delay:

• To put the WiiM at the listening position temporarily and run the auto sync, then return it to the original position. Or,
• To measure the delay with a measurement mic and REW, or
• Google the latency figure for your subwoofer model, and add that to the 3ms delay caused by the physical placement.

 

[EddNog]

Hi everyone,


I also used the WiiM Ultra’s automatic synchronization between the sub and the main speakers. If that’s generally inaccurate, I’d like to set the delay manually. However, I’m a bit confused by the math. Could someone explain—based on the attached sketch—how to calculate the correct delay value? Many thanks!

You can't use basic math based on physical distance due to inherent system/chain/processing delays. Your best bet is REW and a microphone.

-Ed

 

[EddNog]

Mathematically I agree. Just how could the delay of the closest speaker come up as negative relative to the acoustic timing reference?

Here’s the running table I have from my last few REW sessions. The most recent one on the bottom I ran multiple sweeps and averaged the delays, with more repetitions for the subs. Notice the speakers got negative delays:


-Ed

 

[khuntim]

You need better cables!

Seems like my small sub only likes 180° phase so far. I tried some different timings, came back to 11ms (original calculation) with 80hz xover, 20hz-400hz MMM

Not spending too much time with new speakers on the way, will try USB-C input.

I can put the Ultra at listening position, I have 3m USB cable/Coax for sub.

Will be nice to figure out REW.

sub phase zero:

sub phase 180° (80hz xover)

 

[harkpabst]

Seems like my small sub only likes 180° phase so far. I tried some different timings, came back to 11ms (original calculation) with 80hz xover, 20hz-400hz MMM

Nothing wrong with that.

The term "phase" usually describes a variation in timing relative to a full 360⁰ sine wave. The 0⁰/180⁰ "phase" switch is actually a bit of a misnomer because it doesn't shift anything in the time domain. It just inverts the polarity (or "absolute phase") of the signal.

Surprisingly, quite a number of amplifiers do not preserve the absolute phase and human beings are usually not sensitive to it. However, if you combine two separately amplified sources (like e.g. a sub and an amp with passive speakers or a a pair of active speakers) you should always check which polarity results in a clean summation with no dips.

0⁰ or 180⁰, it doesn't really matter as long as the outcome is OK