Ok dosłowny tekst z broszury do Rehdeko (5 str.)
Jak mówiłem, język jest lekko murzyński, ale ja w 99% dokładnie rozumiem o co chodzi - jakby ktoś miał problemy, to jestem gotów przełożyć niezrozumiałe fragmenty (a nawet całość, jak trzeba)
Acoustic pressure or wind pressure?
In majority, actual woofers have a very flexible suspension of their cone. They "move"a great deal and are sometimes exposed in spectacle to the public which is always avid for enthousiastic sensation! However, elastic performances and musical reproduction quality have nothing in common!
Consider some bass musical instruments whose we have spoken later on. Which of these musical instruments produces wind? None!
Contrabassoon goes down to 33 Hz, imperial tuba to 42 Hz,. These are two "wind” musical instruments but they do not produce wind in your face!
Elsewhere, this is entirely impossible since it is with such small ports (beaks or mouthpieces) as an instrumentalist can arrive to create wind. A big drum, when the mallet knocks the skin, does not create any wind either. It is created just a disturbance of the mass of air and not an impetuous breath.
Imagine poor instrumentalists if they are obliged to create us much wind as the loudspeakers that are going to reproduce their execution, what symphonic tempest!
A musical instrument does not create any wind. It gives you what we can call an acoustic pressure, an excitation, a vibration of molecules of the mass of air, and not a perturbation and a strong disturbance of this air molecules. A natural sound that propagates in the space does not displace practically air molecules. Thus. a sound very few audible will be produced by a variation of 19^10 (19 do potęgi 10) of the normal pressure, and a sound, sufficiently strong to provoke an audible pain sensation, will be produced by a variation of 14^10 around the average pressure.
On the other hand, concerning the cone suspension of a woofer. The theory wants it must be very flexible, and able to move a lot,. And there, inevitably, this is no longer a simple vibration of the mass of air that is created but a chaotic and huge displacement of molecules of the air, as would make a fan or even better a compressor!
There is no longer acoustic pressure but "air pressure”. And this too important flexibility is not only responsible of the wind, but also for an incorrect and imperfect reproduction,
Consequences of cone displacement
As we come to see it, all cones that displace a lot in bass frequencies create a big disturbance of the air, a very great air pressure. However, that contributes incontestably to warping measurements.
Thus, when plotting a frequency respons curve of a loudspeaker, the microphone, situated in front of the loudspeaker, is as much influenced by the air pressure (the wind) displaced by the woofer that by the real acoustic pressure. Then the curve is also influenced since it is a paper representation of what the microphone receives; and the dB level i higher not by the alone acoustic pressure of the loudspeaker but because of wind displaced by the woofer, wind that will influence the microphone, not only to 1 meter in front of the loudspeaker (as wants the norm), but also to several meters of distance!
Let us take a very simple example for illustration: a good microphone connected to a tape recorder. If we blow softly In the microphone. Without producing any sound, the influence of the wind is going to make \'knock\' very strong the VU-meters of the tape recorder. Acousticaly, the noise will be quasi imperceptible but, physically, the blow will entail an important flicker of the cone microphone due to air pressure and hence a strong increase of the dB level on the VU-meters.
It is exactly the same phenomon that produced with all traditional woofers. During a measurement, the great cone beats create wind pressure, this wind pressure influence the microphone. and there is an increase of several dB with low frequencies level.
This increase is only fictitious since it is created only with the wind displaced by the cone. In the final analysis, we think to have bass and extreme bass, but this a s only \'false\' bass, \'ghost\' bass, \'artificial\' bass, wind.
This is not the exact acoustic pressure that we hear (or measure), but the noise of the soft beating of the cone, that of its air mixing, or that of its mechanical shaking. The woofer specific resonance itself (the low frequency which the cone overrides) will also tend to amplify this \'good\' low frequencies effect.
There is thus an \'illusion\' of bass, both in measurements and in listening which has very little in common with a live audition.
