What is an elliptical EQ?

An elliptical EQ high-passes the stereo side (difference) channel below a set cutoff so that low frequencies collapse into identical mono while higher frequencies retain full stereo width.

What crossover cutoff frequency should I choose?

Setting the crossover between 80 Hz and 150 Hz works best for most programme material; setting it above 200 Hz can unnecessarily narrow lower-mid instruments.

Which filter slope should I select?

Use 24 dB/oct for general mastering, 12 dB/oct for gentle vinyl mastering transitions, or 48 dB/oct for sharp club-ready sub-bass isolation.

Does monoing the sub-bass change overall track volume?

No. The MID (sum) signal remains full-range and unaltered, meaning center-panned low-end energy maintains its original balance.

What output audio formats are supported?

The processed audio can be exported to MP3, WAV, FLAC, M4A, or OGG Vorbis.

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Sub-Bass Mono Maker

Fold everything below your crossover to mono while keeping the stereo image above it — the elliptical-EQ move that protects vinyl cuts and mono-sub club systems.

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What this tool helps you do

Implements the mastering technique known as elliptical EQ exactly the way vinyl cutting engineers do: the stereo SIDE (difference) signal is high-passed at your crossover while the MID (sum) stays full-range, then L = MID + SIDE and R = MID − SIDE are reconstructed. Below the cutoff the side channel carries almost nothing, so L and R collapse to identical mono with no level change; above it, the original stereo image passes through untouched. The slope (12/24/48 dB per octave) controls how hard the transition happens. Before rendering, the tool decodes the track and measures mid and side energy below the cutoff plus the L/R cross-correlation, so you can see how much out-of-phase low end you actually had; after rendering it re-measures the output and reports the achieved side-band suppression and the new near-perfect below-cutoff correlation. Mastering guidance: keep the crossover conservative (80–150 Hz for most programme material; monoing everything below 300 Hz throws away real width).

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Sub-Bass Mono Maker

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Examples

1. Club Master Sub Tightening

2. Vinyl Lathe Cut Preparation

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