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Mid Side Vinyl:
What’s Really In The Grooves


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Mid Side Vinyl - I bet you thought laying down grooves was easy!

It is - just stay here and follow me. Then you’ll really understand the number one rule for mixing for vinyl. And knowing the “why”, lets it become second nature and easier for you.

The Key Point Behind The Grooves

Let’s review the Mid Side part. (I refer to this so often I should make a page for it. Wait I have! More in-depth here if you want it.)

We start with our stereo file.

To get the MID portion: pan the left and right channels to the center, summing to mono.

To get the SIDE portion: invert the polarity of one of the channels, pan everything to the center then on this composite signal invert the polarity of one channel.

I called this: MID SIDE IN PLACE.

We’re Going Over For An Important Reason:

Yes.

Mid Side “In-Place” is How Vinyl Works. Call it “Mid Side Vinyl”.

Vinyl grooves may have left and right side walls, but they don’t contain left and right channel information.

It’s about motion. The side-to-side - or lateral - motion contains the MID signal (left plus right). The up-and-down - or vertical - motion contains the SIDE signal (left minus right with polarity inverted on one channel of that summed signal). And when you play back the vinyl you should get the original stereo signal.

All commercial stereo vinyl has been cut this way since the beginning. Mid side vinyl - why not?

The Number One Rule For Mixing For Vinyl

Pan your bass and kick dead center. Pan any low frequencies below about 100 Hz dead center.

You may have heard this before! You've probably figured out why:

If the lows were either left or right, your needle would jump out of the groove on every hit, damaging the needle and the vinyl. That won’t get you many happy fans!

When the lows are in the left and right channel, they are in the SIDE portion! The SIDE portions on vinyl are translated by vertical motion! Follow?

“What if I spread the lows across the stereo image?”

Nope. Dead Center.

If any lows are in the sides the risk to needle jumps and damage stays!

Why Is It Done Like This Anyway?

Mono Compatibility.

It was almost ten years after the LP was introduced, that the first stereo records were produced. People already invested in collections of LP’s, which were all mono, were entitled to avoid obsolescence.

Remember: playing back the MID and SIDE portions are about the interaction between the two. Because of that interaction, when the two portions are played in perfect sync, we get the original stereo file. If there is no SIDE portion being picked up, we get just the MID played back with no interaction. And the MID is simply left and right summed together to the center - all the information is there. In other words: MONO.

“But I can sometimes hear clicks and pops left and right? They aren’t in the original signal. How is that?”

The same way left and right panned instruments are recovered with the interaction of the MID and SIDE portions - the side-to-side and up-and-down motions - the same way clicks and pops are placed wherever they are interpreted to be.

But Still...Vinyl Ain’t Perfect

Warped records.

Because the warp is up and down it’s going to affect the stereo image in some way. That’s whether the warp is slow or rapid. It might be audible. It might not. Remember the SIDE portion, which contributes to the stereo image, is in the vertical motion from the vinyl. And no record is perfectly flat.

Vertical tracking angle.

The vertical playback angle of most systems is slightly steeper than the cutting angle. So?

We’re playing back the MID and SIDE portions. The interaction creates the stereo image. They have to play back in perfect sync to get the true stereo image. If the vertical motion happens at a different time than the corresponding lateral motion, we’ll have image problems. Even if that time is only in microseconds. I explain this all here. And: warps will also affect the tracking angles. Still - that may all be part the mystery that charms vinyl fans...

In either case, we have no control over those end results.

What If We Don’t Follow The Rule?

If you want vinyl, and you want to keep the lacquer engineer (and your fans) happy, I will be more than happy to help you after the fact. Because a solid vinyl master translates into a solid master - period.

Also...

Thinking of vinyl as Mid Side Vinyl will help you keep your head about this. Your mixes will be ready to master for any format.


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