Why so much disagreement about EQ curves, especially in Japan — organizing the structure of the debate

Why is there so much disagreement about EQ curves?

Question answered on this page: Why is there so much confusion about EQ curves? Why are opinions so widely divergent, especially in the Japanese-speaking world?

Three axes of disagreement

To organize the debate over EQ curves, disagreements generally arise along three axes.

Axis 1: confusion between "recording curves as fact" and "preferred playback settings"

Changing the EQ curve changes the sound. This is physically natural. And sometimes a certain setting sounds "more desirable."

But "the setting that sounds preferable" and "the curve used in the recording" are two different questions.

When these two are confused, a leap occurs: "it sounded good → therefore this is the curve used in the recording." This is the primary reason the debate over EQ curves fails to converge.

(→ Can you hear a difference when you change the EQ curve?)

Axis 2: confusion between truly unknown areas and established facts

There are certainly unknown areas in the history of EQ curves.

• For some monaural recordings from the pre-RIAA period (before 1954), no record of the curves used has survived. For independent studio recordings in particular, the exact curve is often unknown.

However, this "unknown" does not apply equally to all periods and labels.

• For U.S. stereo LPs (1958 onward), multiple independent sources — including cutting equipment designs, engineer testimonies, and internal documents — indicate the use of RIAA curves.

The fact that "there are unknowns in the pre-RIAA period" is sometimes extended to the inference that "stereo-era records may also be non-RIAA." However, the former being true does not constitute evidence for the latter.

(→ Are all U.S. stereo LPs on the RIAA curve?)

Axis 3: different verification methods — aural comparison and primary sources

The basis for claims about EQ curves can be divided into two broad categories.

Aural comparison: Switching curves on a variable-EQ phono equalizer, listening, and concluding that the setting judged to sound "best" is the "correct curve." The experience is intuitive and easy to share. However, human auditory characteristics (changes in perceived frequency balance with volume), personal preferences, and differences in playback environments all affect the results.

Verification through primary sources: Identifying the curves used in recording based on recording equipment specifications, cutting engineers' testimonies, internal label documents, trade journal articles, and other documentation. These sources are difficult to obtain and are mostly in English.

When these two methods reach different conclusions, opinions diverge on which should be trusted more.

Why is there particular disagreement in the Japanese-speaking world?

The three axes above are universal, but there are structural factors that make the discussion particularly prone to confusion in Japan.

Barriers to accessing primary sources: Most primary sources on the history of recording technology are in English. AES (Audio Engineering Society) papers, Billboard magazine articles, interviews with cutting engineers — accessing such factual sources in English can be challenging.

The course of overseas debate is difficult to convey: The claim that non-RIAA curves were used for stereo LPs once existed in the U.S. and Europe as well. However, it has now been largely refuted by cutting equipment design specifications and the testimonies of several engineers themselves. This history has rarely been reported in Japanese, and remains difficult to convey across the language barrier.

Circulation of information without primary sources: Some "recommended curve by label" lists compiled on the Internet lack any primary-source backing. Some of these have been featured by audio specialist media, and as a result have come to be widely referenced.

Stance of this site

The author spent over two years researching the history of EQ curves based on primary sources. The results are documented in the blog series Pt.0–Pt.25.

The stance of this site is as follows:

• Facts confirmed by primary sources are stated clearly as facts. We do not write "there are various theories" for established facts.
• Truly unknown matters are stated as "unknown." We do not pretend to know.
• No specific individuals or theories are criticized. Facts are presented, and judgment is left to the reader.
• Listening with the sound you prefer is a personal choice. Identifying historical facts is a separate act.

→ Read the series "Things I learned on Phono EQ curves" Pt.0–Pt.25

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