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Multiple perspectives and phase issues?
#1 Multiple perspectives and phase issues?
I've recently been experimenting with some of the newer Grabowski samplesets: Munich, Landau, Pinerolo and Lubin.
Until recently I didn't have enough RAM to load multiple perspectives, so I finally got myself a 128 GB MacBook. Now I can load whatever I want... only to discover that maybe I don't actually want to. 😄
I started experimenting with mixing the different perspectives, partly because of all the enthusiasm around this possibility in the Hauptwerk community. But I immediately noticed a pretty severe collapse of the main perspective (front) stereo image and a degradation of the sound that seems clearly related to phase interference.
In my experiments, the second perspective needs to be at least around -12 dB below the main one before the problem becomes reasonably acceptable. With three perspectives, things get even worse.
So I've gone back to using a single perspective and working on that sound instead. I guess I'll use the remaining RAM to store some vegetables. 😂
Then yesterday I watched the video of Nathan Laube playing the beta release of the new Voxus sampleset at York Minster. I assume it's a multi-perspective/surround recording (nowadays, who would buy a single-perspective sampleset?!), and I immediately heard what sounded like the same problem. It's particularly obvious around 2:15.
Am I the only one hearing this?
I know the obvious answer is that the different perspectives aren't supposed to be mixed down to stereo, but rather played through separate speaker systems. Fair enough, but then you introduce other problems, especially time alignment. And three stereo microphone perspectives don't really constitute surround sound anyway.
So I'm curious: what are your experiences with multiple perspectives? Do you actually mix them? Do you use separate speaker systems? Have you found a way to avoid the phase problems?
I'd genuinely like to understand whether I'm missing something here.
Hallo digitalpipes,
I'll answer in german, but put a translation below for your convenience:
Dein Eindruck ist grundsätzlich korrekt. Das Mixen mehrerer Perspektiven auf eine Stereowiedergabe neigt dazu, Phasenprobleme wie Auslöschungen oder Verstärkungen zu erzeugen. Das der Stereoeindruck der nahen Samples dabei reduziert wird, ist ebenfalls zu erwarten, da bei den entfernteren Kanälen eben deutlich weniger links/rechts Trennung, dafür aber mehr Raumeindruck enthalten ist.
Ich empfehle daher bei meinen Samplesets immer, wenn man nicht die Möglichkeit der Wiedergabe über entsprechende Audiokanäle hat, möglichst nur 2 der 3 Perspektiven zu mischen und eben, wie auch von Dir beschrieben, eine als Hauptperspektive zu nutzen und mit einer weiteren Perspektive anzureichern. Es sollte aber möglichst vermieden werden, dass die beiden Perspektiven im Verhältnis 1:1 gemischt werden.
Es ist leider nicht möglich, die Samples so zu bearbeiten, das alle Samples auf allen Perspektiven phasensynchron sind. Hinzu kommt, dass es ganz wichtig ist, dass die Hauptwerk-Zufallsverstimmung für Mehrkanalsets auf 0 gesetzt ist. Ich denke aber, das berücksichtigen inzwischen alle Hersteller in ihren Definitionsdateien. Hauptwerk hat nämlich keine Funktion, die mehreren Samples einer Pfeife gemeinsam zu verstimmen. Dann schweben einzelne Töne in sich selbst.
Was die Phasenlage angeht, kommt eine weitere NICHT abschaltbare Hauptwerkfunktion hinzu: Hauptwerk versieht alle gespielten Samples mit einem winzigen zufälligen Delay (max ein paar ms), auch hier werden die mehreren Samples einer einzigen Pfeife dann ungleich verzögert. Selbst wenn man es also schaffen würde, alle Samples phasensynchron aufzubauen, würde Hauptwerk selbst hier wieder zu Phasenverschiebungen führen.
Zusammenfassend: Deine Beobachtung ist korrekt und wenn man mehrere Perspektiven 1:1 mischt, sind Phaseneffekte zu erwarten. Allerdings variiert die Wahrnehmung dieser Effekte offenbar auch sehr stark, manche bemerken es nicht einmal, andere stört es eben.
Your impression is essentially correct. Mixing multiple perspectives into a stereo output tends to create phase issues such as cancellation or reinforcement. It is also to be expected that the stereo impression of the nearby samples will be reduced, as the more distant channels contain significantly less left/right separation but more of a sense of space.
I therefore always recommend, when using my sample sets, that unless you have the option of playback via appropriate audio channels, you should mix only two of the three perspectives where possible and, as you described, use one as the main perspective and enrich it with another perspective. However, mixing the two perspectives in a 1:1 ratio should be avoided where possible.
Unfortunately, it is not possible to edit the samples in such a way that all samples are phase-synchronised across all perspectives. Furthermore, it is very important that Hauptwerk’s random detuning for multi-channel sets is set to 0. However, I think all manufacturers now take this into account in their definition files. Hauptwerk does not, in fact, have a function to detune multiple samples of a single pipe simultaneously. Therefore, individual notes would float out of phase with one another.
As far as phase alignment is concerned, there is another Hauptwerk function that CANNOT be disabled: Hauptwerk applies a tiny random delay (maximum a few ms) to all played samples; here too, the multiple samples of a single pipe are then delayed by different amounts. So even if one were to manage to align all samples in phase, Hauptwerk itself would again cause phase shifts.
In summary: your observation is correct, and if you mix multiple perspectives 1:1, phase effects are to be expected. However, the perception of these effects apparently varies greatly; some people don’t even notice them, whilst others find them bothersome.
#3 RE: Multiple perspectives and phase issues?
Dear Reiner,
thank you for the explanation, which confirms my perception. From an audio engineering point of view, I really should have known about this issue, but, having been carried away into a state of overexcitement by the Hauptwerk community, my brain apparently just switched off!
In the end, in real life we can only hear an instrument from a single perspective; unless, of course, we have somehow figured out how to be in two or three different places at the same time…
A single perspective guarantees phase coherence and immaculate stereo imaging, when recorded well. The loss of spatial cues caused by mixing perspectives is therefore really a pity. And the “phasey” sound that results from it is, for me, truly unbearable.
Thanks again for the clarification!
Zitat von digitalpipes im Beitrag #3
Dear Reiner,
And the “phasey” sound that results from it
hmm, do you mean a dynamically changing shift in pahse, like in rotating speakers? In that case my assumption would be that the Hauptwerk random detuning is active, which may slightly detune the samples from the perspectives against each other, even for a single pipe. This can be turned off by the sample set producer, but may be it has not been done for those sets you are mentioning? In that case go into the Hauptwerk settings for the sample set you are working on and set random detuning to zero and try again. Does that change anything?
#5 RE: Multiple perspectives and phase issues?
The video also sounds very strange from 6:00 to the very end...
Couldn't this also be due to some problem in the recording equipment?But this is only a guess, as I don't know how it has been recorded.
Grüße
Wolfgang
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