[sdiy] Waveform mixing - normalization? - Also multimodefilter level normalization

Mattias Rickardsson mr at analogue.org
Wed May 11 15:58:28 CEST 2016

True, good point! :-)

Den 11 maj 2016 2:22 em skrev "Richie Burnett" <rburnett at richieburnett.co.uk

> "Brighter" sounds perceptually louder because of the ear's response.  i.e.
> Equal loudness / Fletcher Munson curves:
> https://en.wikipedia.org/wiki/Equal-loudness_contour
> -Richie,
> -----Original Message----- From: Mattias Rickardsson
> Sent: Wednesday, May 11, 2016 1:06 PM
> To: Oakley Sound
> Cc: Synth DIY
> Subject: Re: [sdiy] Waveform mixing - normalization? - Also
> multimodefilter level normalization
> Yes, filtering will ruin any serious plans of super-duper perception
> application perfection. :-) In a way, we are already used to the fact
> that filters do these things in synths, and we have learned to
> compensate for it. It's a matter of learning to play an instrument.
> When switching between waveforms, though, it's of course important to
> have their levels designed roughly equal to avoid abrupt level
> changes. I usually do this by ear, at mid frequencies, without
> filtering. I.e., I would not normalize the fundamentals, and I would
> not take filtering effects into account. If I'd design a synth with
> simultaneous waveforms from the same oscillator, I'd probably want it
> to mix these in some kind of percentage fashion, summing up to 100%
> which would correspond to the level of any one waveform on its own.
> I'd also be careful to keep the waveforms' fundamentals fairly
> in-phase when mixing them, otherwise some unwanted cancelling effects
> would occur causing lower levels and nasal spectra.
> Btw on a simple analog monosynth with multiple mechanical switches as
> waveform toggle selectors, I figure they can easily be connected so
> that having two waveforms selected would mix them at 50/50% of their
> respective levels. On a more modern machine it could be a bit
> trickier, or easier, according to taste. :-)
> On a similar brown note, I have actually had a tough time deciding
> whether to take filtering effects into account in another
> level-related dilemma: when designing a multimode filter. The output
> from the different modes can be designed to have equal level in the
> passband, but this is sometimes not perfect. On a strongly filtered
> sound - say, a typical filtered synth-bass sound with a closing
> lowpass filter - the sound is perceived louder if a mode with a less
> steep lowpass slope is selected. The difference can be greater than
> you first might expect, since such a small part of the sound is the
> unfiltered passband. Here it might be advisable to consider raising
> the levels a little bit of the filter mode with the steeper slope.
> It's not unproblematic though, since a less radically filtered sound
> would feel strange if it altered level when jumping between filter
> modes that don't do much filtering to the sound.
> /mr
> On 11 May 2016 at 10:08, Oakley Sound <oakleylist at btinternet.com> wrote:
>> I mean consistent perceived volume from a waveform mixing section.
>> Whilst this may sound good in theory I think the problem will come when
>> you
>> filter the mixed result - which we will almost certainly be doing. The
>> relative harmonic structure will change and you'd be left out of kilter
>> again.
>> Personally, I'd stick with equal amplitude. Which I think if you're just
>> after switched waveform selection can be done with a R-R ladder.
>> Tony
>> www.oakleysound.com
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