Saturday, August 25, 2018

Fixing sibilance with a parametric equalizer

What I like best about vinyl are the vocals. Instrumentals, particularly piano, I believe sound just as good on CD than on vinyl, but vocals are different as these are where I notice most clearly the warmth of the format. There's the big problem, though, of sibilance. I have had some success against it over the years and shared some of it on previous posts, but I've learned the hard way that sometimes the source is to blame.

I had always wondered about the pre-out/main in jacks on the back of my preamp and found out that I could hook up equipment through them. A graphic equalizer was an obvious choice, but I didn't like the fact that the bands were pretty much set. As it turns out, parametric equalizers address this and found them readily available on eBay, mostly vintage. I settled for the least expensive SAE 180 from the early 80s at $140 and I received it in great shape.

As compared to the graphic equalizer, a parametric one has the double benefit of allowing the pinpointing of a certain central frequency and the amplitude of the effect. For sibilance purposes I already knew the expected frequencies on which to attack, but was greatly aided by an online recommendation to boost the suspect frequencies in the initial pass to better pinpoint the center. After this, it was only a matter of opening and closing the octave range and decibel volume starting both with the least amount of change possible to get the desired effect, that is mellow the ess sounds while preserving as much as possible the tone of the rest. Just killing the identified frequencies doesn't work because although it may appear that nothing interesting is happening on them, the wholesale removal of brightness makes the music dull and unexciting. Once I tried it, it became apparent to me.

By some experimentation I narrowed the parameters to a general range I could work with. Depending on the source, I tweak a bit. However, I soon discovered what is probably the greatest downturn to my solution and that is the noise floor. My particular equalizer (don't know if this is widespread) has a noticeable noise level that gets worse as one narrows the octave range in the high frequencies. Widening it to around two octaves just barely subdues it to make the whole scheme work, but just barely.

To compensate the loss of brightness by the wide octaves I resorted to raising the level at 1.2 kHz, the highest frequency I could get from the low-frequency sliders, with a three octaves spread by a couple of decibels and very nearly got back all the high frequencies that I had lost, while still keeping the sibilance in check.

This model has a button to activate/deactivate the tone effects and has rec out jacks presumably to pass the signal on the yet another processor.

A couple of small negatives: there's no power switch; presumably it has to be plugged on the rear of your preamp to pop into life when you power the system on; the manual surely makes this clear, but the only place I could find the download online required registration and I couldn't bother. Higher models have an on/off button. Another thing to consider is it small overall shape which doesn't allow straightforward stacking: some sort of space has to be found on the side for it.

In the end I got 85 to 95% of my wish and am very happy about it. Is it just cosmetic? Yes. Does it fix the underlying problems with my set up? Not at all. Does it work for my ears? You betcha.

Approximately what my frequency  curve looks like (using Magix ACL 11)
When I add back just a bit of brightness


Post a Comment