Analog Obsession is known for giving away a steady stream of free plugins, and a mid/side EQ has appeared among their releases. Whether or not that particular offer is still live, the technique is worth learning. Mid/side EQ lets you treat the centre of your mix and the sides separately, which solves problems a normal stereo EQ cannot.
Check availability: free releases can change. Confirm the current price, formats and system requirements on the developer's official page before you download, and use only official links.
What is mid/side processing?
A stereo signal can be split into two parts. The mid is what is identical in the left and right channels, which is the centre of the image. The side is what differs between them, which creates width. A mid/side EQ applies separate filters to each part.
| Part | Contains | Typical content |
|---|---|---|
| Mid | Centre information | Kick, snare, bass, lead vocal |
| Side | Left and right differences | Stereo pads, reverb tails, wide guitars, room sound |
Why use M/S EQ?
- Tighter low end: cutting the lows in the side channel keeps bass focused in the centre and improves mono compatibility.
- Vocal clarity: a small cut in the mid around the vocal range on a busy stereo bus can make room for the singer.
- Extra air: boosting high frequencies on the sides adds width without making the centre harsh.
- Fixing a stereo recording: tame a boomy centre or a harsh side separately.
Step-by-step setup
- Insert the M/S EQ on a stereo track or bus, not on a mono source.
- Set the plugin to process Mid and Side separately if it has a mode switch.
- On the Side, add a high-pass filter around 120 to 200 Hz.
- Optionally add a gentle high shelf of 1 to 2 dB from 8 kHz up on the Side.
- On the Mid, dip a few dB where things sound congested, often between 250 and 500 Hz.
- Check the result in mono and stereo.
Where to use it
Master bus or mix bus
Keep moves small, under 2 dB. A mid/side EQ on the master is a fine-tuning tool, not a fix for a poor mix. If your mix already has clipping issues, revisit your levels using our gain staging guide first.
Synths and pads
Wide pads often carry low frequencies that clash with bass. High-pass the side channel of the pad so the bass stays in the centre.
Drum overheads and room mics
Cut some low mids from the sides to reduce mud, and lift the highs slightly for openness.
Common mistakes
- Boosting the sides too much, which makes the mix collapse in mono.
- Cutting the mid instead of solving the problem at the source.
- Forgetting to check phase relationships on wide sources.
- Never testing on a phone speaker or in mono.
Free tools to pair it with
Once your width is set, add a reverb with plenty of stereo spread. Valhalla Supermassive is a great free choice. For dynamics, see the Analog Obsession LAEA compressor, and find more in our free VST collection.
Key takeaways
- Mid is the centre, side is the width.
- High-pass the sides to keep bass centred and mono-safe.
- Use small boosts and cuts, and A/B in mono.
- Confirm current availability at the official developer page.
A practical mixing example
Imagine a pop mix with a wide synth pad, a centred vocal and a punchy kick. The pad sounds great alone, but in the full mix the low mids feel cloudy and the vocal is slightly buried.
- Put the M/S EQ on the pad channel.
- High-pass the sides at about 150 Hz so the pad's low end collapses gently toward the centre.
- Cut 2 to 3 dB from the mid at around 300 Hz to clear space for the vocal.
- Add 1.5 dB of air to the sides above 10 kHz for sparkle.
- Solo the mix in mono and confirm the pad does not disappear or sound hollow.
Each move is small, but together they clean the mix and make the vocal easier to hear without touching its fader.
Mono compatibility check
Many phones, smart speakers and club systems fold the stereo image to mono. Anything that relies on extreme phase differences can vanish. Flip your master to mono regularly while you work. If instruments drop out or sound thin, reduce stereo widening, and check that no processing on the sides is doing all the work of a sound.
A quick habit is to mix the first pass with the sides muted. If the song already works, the width becomes a bonus and not a crutch.
FAQ
Is the Analog Obsession M/S EQ still free?
Free offers change, so check the developer's official page for the current price.
What frequency should I cut in the sides?
Start with a high-pass between 120 and 200 Hz and adjust by ear, checking the low end in mono.
Can I use M/S EQ on a mono track?
There is no side information in a mono signal, so it will not do anything useful. Use it on stereo material.
Does mid/side EQ change phase?
Some EQs add phase shift, especially at steeper slopes. Use gentle filters and check your mix in mono.
