The current GERIs depend on the variable of AAD (Absolute Average Deviation) only. Now, GERI is being hugely renovated. That is why we stopped posing the GERI values. We will resume posting GERIs after we gather more data on other variables and update GERIs.
The Golden Ears Target Curve refers to the prototype Frequency Response curve that Golden Ears considers ideal. In case of speakers, the Target Curve is completely flat; in case of headphones and earphones, the Target Curve has a slight hump in the bass area.
Golden Ears Target Graph for Earphones and Headphones (Green Line)
Golden Ears Target Graph for Speakers (Green Line)
Note 1. Speakers vs Headphones / Earphones
Because of the difference in the amount of absolute energy (bone conduction) involved between loudspeakers and headphones / earphones, the bass tends to lack impact in the latter, which is why the hump is desirable in the target curve for headphones and earphones.
Note 2. Speakers are the Standard of Flatness
A question that comes up from time to time is ‘why are speakers the standard for flat sound?’ The answer is because recording studios, theatrical audio systems such as Dolby, THX, and live performances are all calibrated based on the speaker as a standard of flatness - this is what ‘Hi-Fi’ is.
Note 3. Personal Preferences
As outlined in the ‘Golden Ears Philosophy’ article, some may not like the sound signature characterized as ‘Hi-Fi’ - in this case, please disregard the Golden Ears Recommendation Index.
Note 4. Error bars on Measurements
Every time that you put on headphones(earphones) to listen to music, the headphones(earphones) shift slightly so that they are never in the exact same position, which leads to the sound changing minutely. The same phenomenon occurs when measuring - to reduce the error as much as possible, Golden Ears uses a real-time analysis (using pink noise) to check for this shift and then measures the device once more using a sweep signal for accuracy, but some error is inevitable.
In order to select recommended items impartially, the G.E.R.I., or the Golden Ears Recommendation Index, was devised. The algorithm used to compute the G.E.R.I. is as follows:
1. Divide the Target Curve and the Frequency Response curve of the product into many subsections (as in differentiation), and obtain the difference in each section.
2. Multiply the difference in each section by how sensitive the ear is in the frequency range, using a weighting curve obtained by taking the JND (Just Noticeable Difference) into account. For instance, the lower frequencies tend to be less noticeable in their deviations than higher frequencies.
3. The weighted average is the G.E.R.I..
Golden Ears weighting curve, Reference: JND (Just Noticeable Difference) Graph
The G.E.R.I. from some sample products were as follows:
Most recommended products had a G.E.R.I. of below 3, so the threshold for being considered for recommendation will be 3 (lower is better).
Note 5. Products within margin of error
While analyzing the AKG K701/702, we found that K701 had a G.E.R.I. greater than 3 by a hairline, while the K702 passed by a small margin, despite their nearly identical sound signatures. This was attributed to the series bordering on eligibility within the margin of error (0.4 dB). To give at least partial credit in cases like these, products with G.E.R.I. under 4, but over 3 will be designated ‘worth considering’.