Feature description
Could a simple stereo width control be added to the DSP section — a mid/side
gain, L' = M + w·S / R' = M − w·S, with one slider for w?
Why the existing DSPs don’t cover it
- Crossfeed narrows the image, which is the opposite direction.
- The binaural/transaural virtualizer does widen, but via crosstalk
cancellation. That’s a different mechanism, with a listening-position
dependency (high-frequency cancellation tolerates only a couple of cm of
head movement) and some inherent coloration. For speaker listening from a
couch it isn’t really usable.
A plain M/S gain has neither problem: no sweet spot, no coloration, no phase
manipulation.
Use case
I’m reproducing a mastering chain (iZotope Ozone 12) in Symfonium so my TV
playback matches my desktop. I measured the chain by rendering three tracks
with and without it and comparing the pairs. Everything transferred to
Symfonium’s existing controls except the Imager stage, which applies
+1.0 dB to the side channel while holding the mid at 0.0 dB — consistent
to within 0.1 dB across all three tracks.
The parametric EQ can’t do this: per-channel filters process L and R
independently, so a cross-channel operation is out of reach at any band count.
A width slider spanning roughly −6 to +6 dB of side gain would cover both this
and the general “slightly wider please” case in one control. Ideally in the
local 64-bit engine, since that’s where the rest of my chain already runs.
Thanks — the PEQ and per-output profiles are excellent.
Problem solved
There’s currently no control for this:
- The parametric EQ can’t do it. Per-channel filters process L and R
independently, and width is inherently a cross-channel operation, so it’s
out of reach at any band count. - Crossfeed only moves in the narrowing direction.
- The transaural virtualizer does widen, but through crosstalk cancellation —
which brings a listening sweet spot of a few centimetres and some inherent
coloration. That’s a much larger intervention than the small, clean width
change I’m after.
More broadly, “I’d like this a little wider” and “this recording is too wide”
are ordinary listening adjustments, and at the moment the only tool for either
is a psychoacoustic effect with significant side effects.
Brought benefits
- Completes the DSP set. Crossfeed narrows, the virtualizer widens
dramatically, and there’s nothing in between. This is the gentle middle
option. - No sweet spot, so unlike crosstalk cancellation it works equally well on
speakers, headphones and in the car. - Almost free: a few multiply-adds per sample. No filters, no latency, no
measurable CPU cost. - Safe at any setting — no coloration, no phase manipulation, no artifacts
needing explanation in support threads. - Fixes recordings, not just preferences. Over-wide 60s stereo mixes and
flat narrow masters both become adjustable.
Other application solutions
Rockbox (player firmware) has this as a plain “Stereo Width” sound
setting. Its manual describes exactly the behaviour I’m asking for: values
below 100% progressively mix each channel into the other, reaching mono at
0%; values above 100% remove content shared between the channels, widening
the field; 100% leaves the signal unaltered. One setting, no psychoacoustics.
Poweramp ships a “Stereo expand” DSP effect on Android.
Ableton Live’s Utility device is the desktop convention — its Width
control is, in Ableton’s own description, simply the amplitude of the side
signal. Most DAWs expose the same thing somewhere (Logic’s Direction Mixer,
and so on), always as a single knob.
Worth noting the contrast: Neutron takes the other route, with an
Ambiophonic R.A.C.E. processor — recursive crosstalk elimination. That’s the
same family as Symfonium’s transaural virtualizer and carries the same
sweet-spot and coloration trade-offs. A simple M/S width control is the
lighter, complementary option rather than a duplicate of what’s already there.
Rockbox’s percentage scale (0% mono, 100% unaltered, above 100% wider) seems
the most user-friendly convention if you wanted one off the shelf.
Device type
All
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