2.4G Wireless Earphone Monitor M-vave

[InTheWorks]

I bought this M-vave WP-10 2.4G Wireless Earphone Monitor Rechargeable Transmitter Receiver from aliexpress:

https://www.aliexpress.com/item/1005003623348899.html

M-vave-WP-10-2-4G-Wireless-Earphone-Monitor-Rechargeable-Transmitter-Receiver-Support-Stereo-Mono-Recording.jpg_640x640.jpg (148.32 KiB) Viewed 211779 times

Quite affordable. USD$37 with free shipping.

Quality isn't awesome, but it has no lag. There are spurious noises when it's quiet. And when it's quiet there's also a slight tone present in the background.

But when there is audio playing you don't notice that stuff. I've never used anything like this before so I don't know if that's normal for these inexpensive chinese 2.4G wireless links. Whatever latency there is, it's not a distraction.

I bought this transmitter/receiver pair some time ago and never got around to testing it. I just played a along to a few songs and it was nice enough.

I plug a 3.5mm male to male cable from the laptop into the transmitter. I plug my headphones into the receiver and clip it to me somewhere. Freedom. I can't speak to how long they run for. I was playing with Aerodrums for about 1/2 hour so they last that long.

Definitely make sure the volume is all the way down (up one from mute) on the receiver and all the way up on the laptop. Raising the volume at the receiver just raises all the noise.

And yeah I normally use a long 3.5mm cord that goes under my throne and up to my back. So the cord is not in the way of the sticks. I don't know how much I'll use this wireless bridge for drums, but I bought it to use with my TV. And honestly, I don't know if those background noises will be too annoying to watch with them.

[Richard]

Cool! That looks like a nice find. But I might have to test out the "no lag" claim for myself

[InTheWorks]

I'm reasonably certain that it's the same technology as the wireless guitar transmitter/receiver.

The specs indicate that the latency is <2ms. Maybe I'll measure it and confirm.

[Richard]

Funny that the AliExpress listing says "Delay: ≤12ms"

[InTheWorks]

Well I measured the latency. I have two pairs of over the ear headphones. I used a splitter on the 3.5mm cable from the headphone output of my laptop. One of the splits went directly to a pair of headphones, the other split went to the M-vave transmitter. I connected the other pair of headphones to the M-vave receiver. Then I put the left ear cup of each pair of headphones together, facing each other. Between them I placed the business end of a Behringer ECM8000 microphone. I then used a rubber band to sandwich the two ear cups together.

I created a file that was mostly silence except for one cycle of 2kHz in the middle and 0.5s of silence on either side. I played this test tone while simultaneously recording. This showed two distinct peaks with a distance between them of 650 samples at 48000Hz. That's 13.5ms. I repeated the test a few times changing the volume on the M-vave receiver so I could make sure the second peak came from that headset. I also turned the receiver and transmitter on/off in different sequences. The latency was pretty constant at 650 samples +/- 20.

So the latency measurement of 13.5ms is definitely not 2ms, and definitely not <= 12ms. Liars!

Still 13.5ms from the M-vave and even 13.5ms from Aerodrums (I was using a windows machine) would be under 30ms. I could measure that, but not tonight.

It's much better than bluetooth though and I can't say I noticed the increase in latency when I was playing Aerodrums. I was distracted with sight reading though.

What I don't like about this system is the background noise. As I mentioned there is an underlying noise that sounds like shushes. When there's music playing it's buried, but when watching something with lots of silence between people speaking (like a movie) that shushing noise is annoying.

[yeshuacreates]

Hi, In the Works. I just noticed your post because I ordered a W-VAVE Tx-Rx pair (for a mere $16, still not arrived) for ad hoc applications and was curious about latency+quality results. So even though I don't have any way of offering my own test results, I thought it might be helpful to point out some potentially problematic caveats to the latency assessment you posted here.

First and foremost, it's really important to note that 650 samples at 48000 Hz has a duration of 135ms, not 13.5. ms = (samples/Hz)*1000. So if you really did measure 650 samples, chances are there are other factors at play resulting in the latency you documented (or at least I would be very surprised if the factory latency of this product turned out to be inherently 10x greater than published, where as a 1.5ms difference for a user would be pretty acceptable).

Some factors to consider include:
1) the way you tested latency here introduced way too many other variables and potential imprecisions to produce an accurate measurement. you have the latency of the playback, of the heaphone connections, of the microphone connection, of the microphone's placement. and you have the cross-feed between to signals from L-R cans on the headphones, no matter whatever you tried to do to dampen or isolate them. ... no way this is gonna be consistent or precise.
2) more minor factor but relevant: using an audio file that peaks at just a certain frequency (2khz in your case) may not represent the average latency of frequency response over the whole audible spectrum (which is how audio is normally played back)

A better way to test (without needing super fancy gear) would still need some sort of audio interface with at least 2 ins and 2 outs. (ideally 4 if you are testing stereo). send 1 out directly back in to an input on the interface. send the other out to the wireless transmitter and send the signal from the wireless receiver back in to another input on the interface. then record both inputs at the same time, then measure sample difference.

[Richard]

I think you miscalculated:

650/48000*1000 = 13.5 ms

[InTheWorks]

First and foremost, it's really important to note that 650 samples at 48000 Hz has a duration of 135ms, not 13.5.

As Richard pointed out, you made a mistake. 650/48000 = 0.0135 seconds. Or 13.5ms.

1) the way you tested latency here introduced way too many other variables and potential imprecisions to produce an accurate measurement. you have the latency of the playback, of the heaphone connections, of the microphone connection, of the microphone's placement. and you have the cross-feed between to signals from L-R cans on the headphones, no matter whatever you tried to do to dampen or isolate them. ... no way this is gonna be consistent or precise.

You're not wrong that a more precise measurement can be obtained, but given the magnitude of the latency (13ms!) do you really care if the error is plus or minus a few samples?

Also you don't seem to understand the measurement. The latency of the sound card has zero effect. The headphones and the mwave were driven by the exact same electrical signal. The sources of error are limited to microphone positioning relative to each headphone speaker and my ability to find alignment points on two (and only two) very visible sine waves within the same recording.

I don't use them anymore because of that background noise I also mentioned in my previous post. Instead I bought a 3m cable and use wired headphones.