The spectrum of the musical signal. Part 4. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The spectrum of the musical signal. Part 4. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Speakers

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Someone James Boyk from the California Institute of Technology conducted a study on the topic "Is there life above 20 kHz?". Well, firstly, he found out that there is, but this is somehow not the topic for us now. But in parallel, he established on some typical, in his opinion, phonograms, what is the distribution of power requirements and restrictions over the spectrum, if the AVERAGE and PEAK signal powers are measured. After all, indeed, the peak nature of musical recordings is most clearly expressed precisely at the upper, most "high-speed" frequencies. That's what brother James did. He took three records and two crossovers. Recordings are written by a singer named Diana Krall, Talking Heads and our compatriot Dmitry Shostakovich. And the crossovers for the experiment were taken three-way, with frequencies of the LF / MF section of 300 Hz, MF / HF - 3000 Hz, or the first order (with the Butterworth characteristic, there is no other one) or the fourth, with the Linkwitz - Riley characteristic. In all cases, the signal power was measured directly and directly at the terminals of the respective strip radiators. Type - that is, that is.

Here is the power distribution by bands he got when it came to average (RMS) powers:

Music signal spectrum

Any-expensive, all in science, just the joy of a graduate student. If filters with a high steepness are used, when only the inherent frequency band hits the speaker, and nothing extraneous, it turns out right along the curves on the graphs that you already know. Percent power units. With filters with a low steepness, of the first order, of course - more, but also not God knows how much. At lower frequencies, again, everything is according to science. The symphonists (third column) don't let the bass speakers work too hard, the pop-rockers throw up some work. Please note: the sum of power percentages does not always add up to 100 percent, since this is the property of filters with a uniform frequency response, the power is not distributed evenly there.

Now let's see what happens if we measure peak power values.

Music signal spectrum

Here you go, be kind! Not noticed in anything illegal, Diana Krall, when measured on the peak scale, showed that the HF band (above 3 kHz) at times accounts for more than 50% of the power. So the school of low-power high-frequency channels, accepted and very comfortable for designers of audio equipment, with multi-band amplification of modern recordings with high dynamics, can fail and will clearly benefit from a critical look. Practical recommendation: the peak power of the HF channel of a multiband system at a sufficiently low frequency of the MF / HF section (such as 3 kHz, we don’t have it any lower) should be chosen of the same order as the power of the MF channel.

A comfortable school of low-power HF channels is not well adapted to modern recordings with high dynamics.

Spectrum of strike in cymbals. It is much wider than one might think.

And how far and how energetically do musical instruments penetrate into the upper frequency region? Without going into the situation above 20 kHz, let's limit ourselves to what is happening in the sound range we are used to. Here, for example, academic orchestral cymbals. Let’s explain who has never been to the conservatory for the last time: cymbals are cymbals that the musician holds in his hands (with the help of loops on the back of the cymbals) and, at the conductor’s signal, smashes them against each other, giving drama to the performance of the work in accordance with the author’s intention. The cymbals sound, in terms of the frequency spectrum - just like on the graph.

It's funny, of course, that a lot of the energy of these seemingly very high-frequency percussion instruments is concentrated in the middle frequencies, up to 200 Hz. The main contribution of the hard worker-squealer to the overall spectrum is above 2 kHz, and even at the upper border of our attention zone, at 20 kHz - amplitude - please. And yet, such an instrument will be played in ANY audio system by at least two speakers in each channel.

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Literature

Magazine "Autosound" № 11 / 2000

Author: Andrey Elyutin; Publication: avtozvuk.com

See other articles Section Speakers.

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