[sdiy] Ray tracing hardware for audio simulation

[rburnett at richieburnett.co.uk]

Thanks for clarifying,

-Richie,


On 2022-08-01 22:14, Mike Bryant wrote:
>> Or is there no "all analogue" path with zero latency in today's modern 
>> digital world!?
> 
> Definitely not !   How could you send data through the Ethernet snake
> from the stage to the mixer, then back again to the monitor earpieces
> without going digital ?  There are one or two analogue-only studios
> left, but almost all remaining analogue live work went digital when
> the X32 was launched.  There's even a couple of notepad style digital
> mixers now at not much more than the all-analogue ones for sole pub
> artistes.  Indeed for these people, they are more and more using
> digital microphones as they are now of good enough quality and easier
> to set up.
> 
> ADC and DAC delay is the primary latency in the system, and you choose
> a mixer with the lowest delay which is the main reason to go 96kHz or
> 192kHz for live - you can't hear any difference but the signal gets
> there faster.
> You try to keep any other delays - the mix bus, Ethernet, effects
> sends and DSP units at as low as possible a delay as possible,
> otherwise when you mix it in with the clean signal you can get all
> sorts of phasing problems.
> 
> Another problem for bands is the bass player sets the timing, the
> drummer follows this from his earpiece, then the bass player hears the
> drums back through his earpiece doubly delayed so he instinctively
> slows down for the drummer to catch up.
> 
> Also bear in mind in live work that 'clean' signal may be some leakage
> into someone else's microphone.  If you have a church choir with 50 up
> to 100 or more live Countryman mics that are fairly omnidirectional
> and all at similar sensitivities, it can get quite complicated.  Live
> mixing isn't simple nowadays - it was much simpler in the analogue
> days when microphones were on stands and had cardioid responses with
> several people singing into one mic.
> 
> The latency issue is also why live sound autotunes don't use SFFTs or
> wavelets, whereas studio ones usually do as they are more accurate at
> the expense of far more delay.  Have a listen to the ones used in
> theatre musicals and they can be highly irritating to say the least,
> and personally I'd rather they weren't used  and just accept the
> average musical singer isn't Freddie Mercury or one of the Three
> Tenors.  A Jesus Christ Superstar production of some years ago was
> infamous for this.
> 
> 
> 
> -----Original Message-----
> From: rburnett at richieburnett.co.uk 
> [mailto:rburnett at richieburnett.co.uk]
> Sent: 01 August 2022 21:43
> To: mskala at northcoastsynthesis.com
> Cc: Mike Bryant; synth-diy at synth-diy.org
> Subject: Re: [sdiy] Ray tracing hardware for audio simulation
> 
> On 2022-08-01 14:38, Matthew Skala via Synth-diy wrote:
>> On Mon, 1 Aug 2022, Mike Bryant wrote:
>>> 1mS delay is too much for live voice processing so they need to work
>>> on
>> 
>> Move the speaker a foot closer to the listener.
> 
> Yeah.  I'm very sceptical of claims about such small latencies
> mattering.  As you say it's equivalent of the monitor speaker being 1
> ft further away.  Many audio CODECs have considerable delay due to the
> digital filters in their ADCs and DACs anyway so that sets the limit
> on what even a basic talk-through DSP program could achieve.
> 
> The only time I can see 1ms latency mattering is possibly for
> something like headphone monitoring where a vocalist might be put off
> by hearing their own voice coming back in the cans with a delay and
> mixing with what they hear directly in their head (via bone
> conduction?)  But then how small a delay *is* tolerable without tonal
> colouration?  And surely for something like "comfort reverb" on a
> vocal monitor mix, only the "wet" reverb part would go through the DSP
> system and incur latency.
> The dry vocal signal would still be all analogue, and therefore have
> no delay?  (Or is there no "all analogue" path with zero latency in
> today's modern digital world!?)
> 
> -Richie,