Measuring latency and signal levels of the Stage using a digital console

  • Testing, testing, 1... 2... BLAT!!! ARGH!!!



    My digital console looked a bit unloved, so I decided to use it as a fancy signal generator to do some testing with the Kemper Stage. I made a video of my methods and observations in case it is interesting to anyone from a technical standpoint. Some of it just helps *visualise* what's happening to signals rather than giving out numbers. I accept that some of this may be known already or buried in the manuals and that I've also taken some liberty with my assumptions!


    I'm interested to keep the technical conversations going for my own learning, so if there is something flawed in my test methods - [entirely possible] - and/or you're getting wildly different results, please let me know and I will try, try again...

    Here are the video 'chapters' if you just want to skip through:


    0:05 SSL Live test rig explanation

    1:10 +14dB of gain measured from inst. input to line output

    2:00 -12dB switch is two -6dB stages

    2:30 Different gain stages in the signal path

    3:00 Bug in latest 7.4.1 release regarding -6 dB switch for Git+Processing

    4:40 1kHz tone stack harmonics test

    5:00 Pink Noise Stack test

    5:30 Phase cancellation test - nice and flat

    6:50 Latency measured = 2.5 ms

    8:10 Constant latency mode = 4.9 ms

    9:30 Essential cheesey outro


    Notes in addition to commentary, the phase-cancellation test did factor in the latency of the return signal, delaying the reference, I just didn't mention it. It made no significant difference to the result. I could get absolute cancellation of the 1kHz sine wave signal when aligned, but also didn't show this.


    All the best,

    Ed

  • EdwardArnold

    Changed the title of the thread from “Signal generator tests with the Kemper Stage using an SSL Live console” to “Measuring latency and signal levels of the Stage using a digital console”.
  • Most digital wireless systems will introduce more latency than the Kemper. However, a real amp will have latency depending how far away you are from the speaker too. If you are in ears it should be very good.

  • Fair comment - I should measure my Shure PSM-300 system actually. A guy I know who runs a live rental company said he'd bought back a lot of analogue mic and IEM transceivers/receivers they thought they'd moved on from more recently, as a couple of high profile tours had been plagued by latency adding up to too much through the complete system and interference in the 2.4 and 5GHz bands meaning they needed an unhealthy dose of radio transmission level onstage to make the digital systems work.

  • Most digital wireless systems will introduce more latency than the Kemper.

    This might surprise you (it has me), but now I remember why I bought the Shure PSM system; I measure the latency at only 0.667ms ! A quick check on the Shure website to make sure and yep, they quote 0.7ms end-to-end. I'm using the P3RA belt pack for reference - others may differ. There are surely much slower digital IEM systems out there - I seem to remember Line 6 options I looked at are 4ms, which seems unreasonably slow by comparison.


    Anyway, that means a round trip latency of 3.2ms for a Kemper + PSM + analogue mixer system. That's the same time it takes sound to travel 1m through the air... 8|

  • This might surprise you (it has me), but now I remember why I bought the Shure PSM system; I measure the latency at only 0.667ms ! A quick check on the Shure website to make sure and yep, they quote 0.7ms end-to-end. I'm using the P3RA belt pack for reference - others may differ. There are surely much slower digital IEM systems out there - I seem to remember Line 6 options I looked at are 4ms, which seems unreasonably slow by comparison.


    Anyway, that means a round trip latency of 3.2ms for a Kemper + PSM + analogue mixer system. That's the same time it takes sound to travel 1m through the air... 8|

    That is incredibly low, but I avoided Shure when getting into in ears because the system I looked at (PSM300 ?) was mono at the time.


    I had a Smooth Hound guitar wireless system at one stage with 8ms quoted latency! That seemed a bit much with other delays in the system, so I moved on.

  • I have the PSM300, which is stereo, which I use with some RHA earbuds. I tried out a PSM200, which is mono and I could not get on with it, personally.


    8ms is outrageous for a wireless system in modern terms it seems. IIRC the Line 6 G10 and G30 stuff is under 3ms. I still have an Audio Technica analogue system that has no latency, but doesn’t sound too great. It is also only just clinging on to a bit of channel 70 in the legal spectrum - the MoD have taken all its other channels ?

  • I have the PSM300, which is stereo, which I use with some RHA earbuds. I tried out a PSM200, which is mono and I could not get on with it, personally.


    8ms is outrageous for a wireless system in modern terms it seems. IIRC the Line 6 G10 and G30 stuff is under 3ms. I still have an Audio Technica analogue system that has no latency, but doesn’t sound too great. It is also only just clinging on to a bit of channel 70 in the legal spectrum - the MoD have taken all its other channels ?

    You're right; it was the 200 with 2 separate inputs, but in mono:-) I ended up with the Sennheiser EW 300.

  • damn! Gutted to hear that the PSM300 has such low latency. Now I can’t blame my shit timing on the IEM latency and might need to actually do some practice with the metronome ?

    Haha :D Blame it on interference from the lights or something Alan, or every time you miss a beat just stare in disgust at the keyboard player.