Preface: The history of the research on the frequency response curve of speakers and the origin of the CEA2034A standard
For a long time, people usually only use the axial frequency response curve to describe HiFi speakers and monitor speakers. Only use simple RTA curves to test and tune the performance of the speakers in the room. But things are not that simple.
In 1985, Dr. Floyd Toole, then a senior researcher at the National Research Council of Canada, first defined the "Spinorama" speaker test method.
In the 1990s, Dr. Floyd Toole and Sean Olive, who joined Harman International, further discovered the importance of the off-axis performance of the speakers on the sound quality in their experiments. However, people's research at that time only found that the sound radiated from the loudspeaker in different directions would have an impact on the sound quality and subjective hearing. It is not clear what quantitative relationship these effects are.
At the end of the 1990s and the beginning of the 21st century, the US CU (Consumer Reports) released sound ratings based on objective test data, which caused quite a stir in the industry, but the calculation method of the ratings was not strictly demonstrated. This feeling is very similar to the RTINGS I saw at the first time. It just calculates a score without verification by psychoacoustic experiments, but some consumers think it is very professional.
In 2004, Dr. Sean Olive published the experimental results in the International Audio Engineering Association AES.
Since around 2000, there have been many speakers designed according to this standard, such as Revel Salon2, Revel F208, JBL M2 and so on.
This standard became the American National Standard in 2015.
At present, more and more HiFi speaker brands and monitor speaker brands have designed speakers according to this standard. For example, KEF is one of the first brands outside of Harman International to disclose test data of similar standards (2018).
Prologue: How to interpret the CEA2034A frequency response curve data of speakers?
Before introducing how to interpret the CEA2034A frequency response curve data of speakers, I must first emphasize several applicable premises of this standard:
This standard does not apply to large-signal, high-power professional speakers; (this part of the explanation is only applicable to regular volume, and the dynamic range and maximum sound pressure level performance will be described separately below)
The interpretation of this standard below is limited to the sound quality and subjective listening performance of the speakers, and is not used to explain the sound field of the speakers (spatial impression performance). The sound field performance of the speakers will be described in the second half of this article;
For the interpretation of the data, the correlation coefficient of the prediction model is 0.86, indicating that there may be a certain range of fluctuations between the sound quality of the speakers and the actual hearing through the data interpretation. In the case of similar comprehensive data performance, there may be cases where the actual subjective evaluation of speakers with poorer data performance is better than speakers with slightly better performance. But usually, speakers with good data actually have a much better listening experience than speakers with poor data. And the interpretation of the data prediction score is limited to playing music instead of movies.