Help / DSP Rack
The spectrum analyser and visualiser
The Spectrum panel in the DSP Rack draws the frequency content of whatever is playing, bar by bar, live. It is a window onto the sound rather than a control over it. Nothing you see there changes what you hear.
Where it is, and what it is not
Open DSP Rack from the left navigation. The page is two rows of panels. The top row holds the Equalizer, the Parametric EQ and the Output meters. The Spectrum sits in the bottom row, alongside ReplayGain, Crossfeed, and the column carrying Bit-perfect mode and the Signal Path. What is in the DSP Rack tours the rest.
It has no buttons, no sliders and no menu. It exists to show what the processors beside it are doing.
There is no second visualiser elsewhere in the app. The full-screen player you can open from the Now Playing pane on Home gives you artwork, lyrics and a scrubber, not bars. There is no waveform view, no mirrored-bar view and no colour picker here; the phosphor swatches you may have spotted belong to the Output meters.
What the bars mean
Fifty-two bars, low frequencies on the left and high on the right, sampled from a finer sixty-four band analysis behind them. They are spaced logarithmically, so an octave takes roughly the same width wherever it falls. That is why the bass end looks generously wide and the top end compressed.
Bar height is a level on a perceptual scale, not a calibrated decibel reading. Treat it as shape, not as measurement. When you want numbers, the Output panel in the row above gives you peak dBFS, a VU needle, a PPM needle and a momentary LUFS figure. See Output meters - VFD, VU, PPM & LUFS.
The band edges follow your output device's sample rate, and the rightmost bar always sits at half of it. The same album will not fill the width identically at 44.1 kHz and at 96 kHz.
Where it taps the signal
The Spectrum reads the same buffer the app hands to your output device, after the rack has done its work. ReplayGain, the Equalizer, the Parametric EQ, crossfeed and the volume control all sit upstream of it, in that order. So:
- Lift a band on the Equalizer and the bars beneath it rise.
- Turn the volume down and the whole display drops with it.
- Engage crossfeed and the change is visible.
That makes it the quickest way to confirm a control you just moved is really reaching the audio.
With Bit-perfect mode armed, the rack stops shaping the stream, so the Spectrum shows the audio with nothing from the rack on it. That is narrower than it sounds: a sample rate conversion can still sit in the path, and the Signal Path column names that stage when it does. See Bit-Perfect mode: the bypass switch, and the badge it is not.
The Spectrum does not dim or pick up a Bypassed tag the way the Equalizer, Parametric EQ and Crossfeed panels do, because it has nothing to bypass. It simply keeps drawing.
The picture is mono. Left and right are averaged before the analysis, so the Spectrum cannot show you channel balance or a mono fold. The Output meters keep independent left and right columns for exactly that.
Display only, in the strict sense
On its way out, the audio thread copies each rendered buffer into a small store of recent samples, and the drawing code reads from that copy. Neither side waits for the other: when the store is busy, either one buffer's copy is skipped or the bars ease down for a single update. Leaving the DSP Rack open all evening changes not one sample of what reaches your device.
How fast it moves
Every third display frame, so roughly twenty updates a second on a 60 Hz screen. Each update analyses a 2048 sample window of the most recent audio, about 46 milliseconds at CD rate, and blends roughly a quarter of the new reading into what is already on screen, so the bars settle instead of flickering. Fast enough to follow a snare, smoothed enough to read.
When nothing is playing the bars fall away and the drawing stops until you press play again, so a DSP Rack left open on a paused track costs nothing.
What it is good for
- Confirming an EQ change landed on the bands you meant.
- Watching what crossfeed does to a headphone mix.
- Getting a rough sense of how far up the band a track carries, though the display is far too coarse to be evidence about a file on its own.
It is not a measurement instrument or a verdict on quality. For what a file actually is, see The signal path & the bit-perfect badge and Library Health & finding duplicates.
The Spectrum carries no entitlement check and draws on any licence. Two neighbours in its row do, and say so on the panel: the ReplayGain Scan button runs against a usage allowance, and the Bit-perfect toggle reads "Preserve audio data - Lifetime" until your licence covers it.
If the bars sit flat while music is clearly playing and the Output meters are moving, that mismatch is worth telling us about. See Is this a bug? How to report it.