Acoustic design of low-frequency dynamic head
Constructors foreign firms "Jamo" and "Paradigm" developed by the AC, comprising separately from the low-frequency level (subwoofer) and two high-frequency speakers. Subwoofers are a body placed in it and dividing it into 2 volumes acoustic panel with the installed dynamic bass head. This head front surface of the diffuser works on single closed volume of the shell, and rear - second, bass reflex, tuned to a specific frequency. Design with two inverters that are configured on different frequencies, known as dual setup.
Some subwoofers are composed of two bass heads based on the principle of Push-Pull set against each other and are in acoustic communication.
In some designs used bass head with two voice coils. This allows you to connect the speaker to the two channels of a stereo amplifier, bass.
The range of frequencies reproduced these AC - 25...150 Hz.
I have made several subwoofers of similar design. Used domestic treble head DN-3. The result exceeded expectations!
Subwoofers really give, as stated in the advertisement, "...unsurpassed, profound, and penetrating the reproduction of bass tones".
I want to share my experience of making the most successful to repeat subwoofer design with one bass head.
Case (figures 1, 2) made of chipboard with thickness of 20 mm. wall of the housing are connected to each other by rails 20x20 mm with glue and screws. Acoustic panel with a hole for the bass head is mounted inside the speaker. The rear wall of the housing is removable, it installed an HPF and terminals of the low pass filter - model for multilane AU). Pipe inverters - with an internal diameter of 75 mm, a length of 50 and 250 mm, the thickness of the walls should be at least 3 mm Diameter holes for inverters in the drawing is not specified and depends on the diameter of the pipes used.
The inner surface of the acoustic box is glued with batting or foam. The bass head is attached to the panel with screws. The gap between the panel, the bass head and the walls of the housing are sealed with clay and foam. The rear wall is attached via a foam gasket. Part of this speaker is glued veneer or plastic foil. Hole inverters are issued with decorative moldings in the form of rings.
P. S. unfortunately, the figure does not shows the vertical size of the subwoofer, but according to my rough calculations it should be around 600 mm. (N. B.)
1. Vasiliev V. A. Foreign Amateur radio designs.- Moscow: Energiya, 1977; M.: Radio and communication, 1982.
2. Advertising catalog of "Paradigm".
3. The catalogue of the firm "Jamo".
A. ILYIN, Lipetsk.