Meze Audio 99 Classics and Meze Boom Mic as a Hi-Fi gaming headset with a real fun factor including burl wood and stainless steel

1 - Einführung, Lieferumfang und technische Daten 2 - Unboxing, Tragekomfort und Funktionalität 3 - Mkrofon im Detail mit Messung und Audio-Sample 4 - Kopfhörer-Messung mit Frequenzverlauf und Decay 5 - Subjektiver Sound-Check und Fazit

Measurement setup and basics

In general, so-called couplers with clearly defined volumes and built-in, properly calibrated measurement microphones are used to measure the transmission behavior of headphones. The rest is then also based on the object to be measured. The setup can be used just as well for plug-in headphones (in-ears) and small headphones (e.g. from hearing aids) as for simpler headphones and headsets as so-called on-ears (headphones with supraaural cushions). For such headphones (on-ear), the “artificial ear” according to IEC 318 can be used, which I have now followed with the implementation.

The thick over-ears, i.e. circumaural or ear-enclosing headphones, are not easy to handle when it comes to measurement and, above all, reproducibility. This is because there are not yet any truly standardized couplers. The reasons for this lie in the difficulties of measurement technology and the many influencing factors that make reliable reproducibility almost impossible. Therefore, such circumaural headphones are mainly measured with appropriately modified couplers for supraaural headphones by using an additional flat plate as a support for the circumaural cushion (see picture).

Important reference point for headphones: the Harman curve

The so-called Harman curve is an (optimal) sound signature that most people prefer in their headphones. It is therefore an accurate representation of how high-quality speakers sound in an ideal room, for example, and it shows the target frequency response of a perfect-sounding pair of headphones. It also explains which levels should be boosted and which should be attenuated when using this curve as a basis. This also explains the term “bathtub tuning”, which is often quoted, but in which the Harman curve is completely misused and exaggerated.

For this reason, the Harman curve (also known as the “Harman target”) is one of the best frequency response standards for enjoying music with headphones, because compared to the flat frequency response (neutral curve), the bass and treble are slightly boosted in the Harman curve. This “curve” was created and published in 2012 by a team of scientists led by sound engineer Sean Olive. The research at the time included extensive blind tests with different people testing different headphones. Based on what they liked (or didn’t like), the researchers found and defined the most popular sound signature.

Tuning headphones can be really problematic due to the human anatomy. Everyone has a slightly different pinna and ear canal, which affects how individuals perceive certain frequencies. In extreme cases, there is a difference of a few dB from person to person, which explains the small differences in some measurements with artificial ears. Furthermore, if the sound is not absorbed, it is also reflected by other surfaces. Theoretically, a torso could also be included in the test setup, but this would be far too time-consuming.

Measuring the frequency response

Now we come to the measurement in which the headset was measured on the HIFIMAN. The output impedance of the power amplifiers is well below one ohm, so that there are no impedance shifts and therefore no additional measurement errors, especially in the bass range. Speaking of the bass range: we see a very strong emphasis and for users who pay particular attention to bass quality, the controlled and “clean” bass of the Meze 99 Classics offers an excellent listening experience, despite the slight over-fattening. The bass is “fun” but never overdone, making the headphones suitable for bass-loving listeners and audiophiles alike. If you find it a little too much, simply turn it down a little.

The frequency response of the Meze 99 Classics offers a warm, natural and balanced reproduction that is ideal for listeners looking for a detailed but not overly analytical sound signature. The slight emphasis on the upper bass and lower mids gives the sound fullness, while the treble and super highs are kept gentle to ensure a pleasant and relaxed listening experience

Cumulative spectra (CSD, SFT, Burst)

The cumulative spectrum refers to different types of graphs that show time-frequency characteristics of the signal. They are generated by successively applying the Fourier transform and suitable windows to overlapping signal blocks. These analyses are based on the frequency response diagram shown above, but also contain the time element and now show very clearly as a 3D graphic (“waterfall”) how the frequency response develops over time after the input signal has been stopped. Colloquially, this is also known as “decay” or “decay”. Normally, the driver should also stop as quickly as possible after the input signal has ceased. However, some frequencies (or even entire frequency ranges) will always decay slowly(er) and then continue to appear in this diagram as longer-lasting frequencies on the time axis. This makes it easy to recognize where the driver has glaring weaknesses, perhaps even particularly “clattery” or where, in the worst case, resonances could occur and disturb the overall picture.

Cumulative Spectral Decay (CSD)
The cumulative spectral decay (CSD) uses the FFT and a modified rectangular window to analyze the spectral decay of the impulse response. It is mainly used to analyze the driver response. The CSD normally uses only a small FFT block shift (2-10 samples) to better visualize resonances in the entire frequency range and is therefore a useful tool for detecting resonances of the converter. The picture shows very nicely the transient response and some tiny bass resonances in the upper bass and lower mids.

Short-time Fourier Transform (STF)
The Short-time Fourier Transform (STF) uses the FFT and Hanning window to analyze the time-varying spectrum of the recorded signals. Here, a larger block shift (1/4 to 1/2 of the FFT length) is generally used to analyze a larger part of the time-varying signal spectrum, which is particularly useful for applications such as speech and music. In the STF spectrum, we can now also see very clearly the work of the drivers, which have hardly any weaknesses. The slight “trailing” at the lower frequencies below 500 Hz is then repeated again at approx. 2KHz. You can live with that very well.

Burst decay
With CSD, the plot is generated in the time domain (ms), while the burst decay plot used here is displayed in periods (cycles). And while both methods have their advantages and disadvantages (or limitations), it is fair to say that the display in periods can be more useful for determining the decay of a driver with a wide bandwidth. And this is exactly where the Meze 99 Classics also perform well. We hardly see any real resonance oscillations. We definitely like that.

Interim conclusion

That (almost) concludes this part and we come to the subjective impression on the last page.