Envelopment in Spatializer not spreaded enough?

A re-post of my follow-up in question http://www.fmod.org/questions/question/whats-the-alternative-of-3d-spread-in-studio/, just to draw some attention…

It seems the effect of envelopment in Studio is kind of different from the 3D spread in Designer. We tested it with a stereo sound where the sound in the two channels are quite different. In Fmod Designer, when we set 3D spread as 180, the two channels are quite spreaded almost the same as a 2D sound. However in Fmod Studio, even if I set Min Extent to 180 (and 360), and Sound Size to maximum, the two channels are still somehow mixed together and make the sound feel like emit from the center.

Why is there such behavior difference? Am I misunderstanding something?


There is no direct equivalent of Designer’s Speaker Spread effect in Studio. The closest equivalent is the “Extent” of the event instance, which is derived from an event’s distance parameter value and the envelopment properties of its spatializer effect, and even that is rather different.

Designer’s speaker spread effect operated in a very simple way: The channels of a given signal were distributed around an arc whose length was defined by the 3D speaker spread property. When this caused a channel to fall between two real-world speakers, the signal from that channel would be distributed between those speakers in proportion to how close to each of those speakers it was.

FMOD Studio’s envelopment is significantly more complex: Every spatializer has a sound size and min extent. (By default, the sound size is double the spatializer’s min distance property and the min extent is 0 degrees, but both can be set to other values.) Both of these values, along with the distance parameter of the event, are used to calculate the event instance’s “extent,” such that extent can never be lower than Min Extent, but will otherwise be 360 degrees when distance is 0, 180 degrees when distance is half sound size, and 0 degrees when distance is equal to max distance. Extent, like Designer’s 3D speaker spread, represents an arc around which a signal’s channels are distributed, but the way in which those channels are positioned is different, such that when extent is 360 degrees the channels are positioned relative to each other as the speakers are to each other.

As for why Studio handles this differently…

Designer’s 3D speaker spread required you to manually create an automation curve for each event that you wanted it to affect. It took trial and error to get the curve right, and even knowing that it was necessary required a detailed technical understanding of what the effect did and how Designer’s spatialization of 3D event instances worked. In addition, if you wanted 3D speaker spread to apply to more than one event, you would have to duplicate your effort for each of those events.

FMOD Studio, by contrast, automatically calculates extent for every event with a spatializer effect. This requires no effort on your part, and the default values require little or no adjustment in the vast majority of cases. In the few cases where the default doesn’t quite fit, it’s generally sufficient to tweak the spatializer’s sound size or min extent properties a little; automating them is an option, but is rarely necessary.

In short, Studio’s envelopment properties are easier to use and significantly more powerful than Designer’s 3D speaker spread effect.


Thank you for this super detailed answer!! Clarified a lot of my confusions.

One follow up question though. Why 2 channels are still positioned inside of 2 real-world speakers even when extent is 180 or 360 degree? When distance between 2 channels are maximum, I expect each channels are closer to the each position of real-world speakers, like 2D sound. Is there any way to widen the distance of channels even more than setting MinExtent to 360?


The reason why a channel may be positioned between speakers even when extent is 360 degrees is that the event emitter and the listener may be rotated relative to each other and panned due to distance. If the listener and emitter have the same coordinates and are facing the same way, the channels and speakers should line up as in a 2D event.

Extent cannot exceed 360, but you could potentially use a channel mix effect and sends to mix your output in a variety of unusual ways.