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What Are EQ Curves? Understand the Most Important Curves in Vinyl History

For many music fans, EQ curves remain an abstract concept despite their importance in the world of vinyl records. Without EQ curves and standardization in the record industry, listening to vinyl would not be the same rewarding experience.

To properly explain what EQ curves are, we must first understand what equalization (EQ) is and why it’s so important. Equalization is the process of adjusting the volume of different frequencies in sound recording and reproduction. 

The curve portion of an EQ curve refers to the curved shape that the volumes of the frequencies form. This curve is for playback purposes and is the opposite of the curve used when the recording is mastered. With each curve acting as the inverse of the other, you get improved sound quality, more music on each record, and less groove damage. This phenomenon is also commonly referred to as pre-emphasis (the frequencies used when recording/mastering) and de-emphasis (the curve used when the recording is played back through a stereo system).

So, now that EQ and curve have been defined separately, let’s nail down a definition of EQ curves and cover some of the most important curves throughout vinyl history.

EQ curves are standardized recording characteristics that ensure records are mastered and manufactured with equalization that ensures a smooth listening experience. 

RIAA Curve

Visualization of the RIAA curve.

Until the RIAA curve came along in 1954 and eventually became the standard, various companies used their own EQ curves when producing records. The focus here will be on seven of the most iconic EQ curves, including the RIAA curve we still use today. For the sake of accuracy, Discogs has enlisted the help of a few audio experts at Technics.

RIAA

With the RIAA curve, low frequencies are reduced and high frequencies are boosted before being reversed in the playback process. Unless you collect a lot of pre-1954 records and equipment, most of your vinyl and gear will feature the RIAA curve.

Columbia

Established in 1948, this EQ curve was used for Columbia and many other labels’ 33 ⅓ LPs. The low frequencies of this pre-RIAA curve are cut at a lower volume. This can sometimes make Columbia EQ curve records sound a bit too bright when played through a standard RIAA setup.

DECCA/FFRR

This curve was used for Decca and London shellacs from 1944 – 1956. The FFRR stands for full frequency range recording, which was groundbreaking technology that allowed a full frequency range of audible sound to be captured on a 78.

AES

Developed by the Audio Engineering Society, the AES curve was originally intended as a replay standard for American shellacs of the 1930s and ‘40s. However, many record producers used the curve between 1951 and 1958.

NAB

NAB stands for the National Association Of Broadcasters and this curve was originally used for broadcast transcriptions before becoming widely adopted from 1949 – 1958. This curve is also known for having a bit more of a bass boost when compared to the Columbia curve.

RCA

This curve was used in the early 1950s for LPs mastered by RCA for other labels. In 1952, the curve evolved into a new orthophonic version that eventually became standardized as the RIAA curve in 1954.

IEC

In 1963, the IEC (International Electrotechnical Commission) curve disputed the RIAA curve and by 1976, the RIAA-IEC curve was born. This curve has a lower volume for the low range which can help reduce unwanted noise.

EQ Curves Made Easy

If you have an extensive collection of pre-1960 records, you may be wondering if there is an easier way to switch between EQ curves. For years, separate sets of equipment and some audio wizardry have been the main options. Now you can easily toggle between these 7 EQ curves with the touch of a button. The Technics SU-R1000 Integrated Amplifier allows you to select the EQ curve that matches the record you are playing. You can also toggle between the EQ curves to see which sounds best for each album you spin. If you are unhappy with the sound, you can always switch back to the standard RIAA option, which has been celebrated for its unparalleled accuracy by Stereophile.


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