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Τα ηχεία bass reflex είναι τα πλέον διαδεδομένα λόγω της αποδοτικότητάς τους στις χαμηλές συχνότητες. Κάποια έχουν την οπή στο εμπρός μέρος της καμπίνας, κάποια στο πίσω και μερικά στο κάτω μέρος. Συχνά ακούω και διαβάζω ότι η θέση της οπής επηρεάζει την αλληλεπίδραση του ηχείου με το χώρο ή/και το "μπουμάρισμα" του ηχείου, κάτι που, σε γενικές γραμμές, δεν ισχύει.
Παραθέτω επεξήγηση της genelec σχετικά με τις διαφορές τοποθέτησης της οπής bass reflex στην καμπίνα ηχείων.
"The direction where the bass reflex port is facing does not greatly influence the work of the bass reflex. While it is in resonance the reflex port generates low frequency sound. This sound sums with the low frequency sound output from the woofer at other frequencies. The distance and location of the bass reflex port is designed so that this summation works correctly.
If the reflex port is not sufficiently large, the air motion in the port can become turbulent (non-linear). This will dramatically increase air flow losses in the reflex port. The higher flow losses can cause the bass reflex to stops working. This will change the low frequency characteristics of the loudspeaker. In Genelec designs we take care to dimension the reflex port to have sufficient capacity to support the system up to the maximum sound level output.
In several Genelec products the bass reflex port opening is behind the enclosure. When you push the loudspeaker close to a wall, a small gap to the wall is needed to enable the bass reflex to work at full capacity. Our experiences show that a distance of twice (2x) the port diameter from the wall to the enclosure back is a very safe distance.
Benefits of a reflex port opening in the rear of the cabinet:
It allows to have a maximized waveguide (DCW) area on the enclosure front
It minimizes acoustic diffraction as the front of the enclosure has no holes, vents or slots. This is especially significant near the tweeter.
The port opening, or flare, can be significantly larger, ensuring laminar flow up to high sound level outputs, high linearity and low system distortion at woofer frequencies.
It minimizes the audibility of air flow in the port because the port opening is faced away from the listener. When the air flow in the port generates noise, this noise is typically 10…20 times higher in frequency than the port tuning frequency. The flow noise is therefore rather directional, and by having the port opening in the back, this noise is well attenuated compared to having a port in the front and directing such noises towards the listener."
http://www.genelec.com/answers-library
Παραθέτω επεξήγηση της genelec σχετικά με τις διαφορές τοποθέτησης της οπής bass reflex στην καμπίνα ηχείων.
"The direction where the bass reflex port is facing does not greatly influence the work of the bass reflex. While it is in resonance the reflex port generates low frequency sound. This sound sums with the low frequency sound output from the woofer at other frequencies. The distance and location of the bass reflex port is designed so that this summation works correctly.
If the reflex port is not sufficiently large, the air motion in the port can become turbulent (non-linear). This will dramatically increase air flow losses in the reflex port. The higher flow losses can cause the bass reflex to stops working. This will change the low frequency characteristics of the loudspeaker. In Genelec designs we take care to dimension the reflex port to have sufficient capacity to support the system up to the maximum sound level output.
In several Genelec products the bass reflex port opening is behind the enclosure. When you push the loudspeaker close to a wall, a small gap to the wall is needed to enable the bass reflex to work at full capacity. Our experiences show that a distance of twice (2x) the port diameter from the wall to the enclosure back is a very safe distance.
Benefits of a reflex port opening in the rear of the cabinet:
It allows to have a maximized waveguide (DCW) area on the enclosure front
It minimizes acoustic diffraction as the front of the enclosure has no holes, vents or slots. This is especially significant near the tweeter.
The port opening, or flare, can be significantly larger, ensuring laminar flow up to high sound level outputs, high linearity and low system distortion at woofer frequencies.
It minimizes the audibility of air flow in the port because the port opening is faced away from the listener. When the air flow in the port generates noise, this noise is typically 10…20 times higher in frequency than the port tuning frequency. The flow noise is therefore rather directional, and by having the port opening in the back, this noise is well attenuated compared to having a port in the front and directing such noises towards the listener."
http://www.genelec.com/answers-library
