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Showing posts with the label Subwoofer Design

Subwoofer Design - Bandpass Dual Chamber

Bandpass Dual Chamber Basic Theory:
The front and rear of the driver are mounted in separate enclosures and tuned to specific calculated values. Resultant output is suppose to be better than any of the other designs mentioned previously. Bose owns the rights to the exact details behind this design. They explain the theory like this, "The low-frequency speaker drivers are located between separate acoustic compression chambers inside a patented Bose Acoustimass module. As each speaker cone moves, it excites air in the chambers. Trapped in the chamber, this air acts as an acoustic spring, which interacts with the air in the port to produce more low-frequency sound with less power. The system is more efficient and requires less cone motion, which in turn produces less distortion. In the event that any otherwise audible distortion is produced, the patented design traps it inside the acoustic chambers -- so it never enters the room. The result is an Acoustimass module with no audib…

Subwoofer Design - Order Vented

Order Vented Basic Theory: Also known as bass-reflex, ported or vented. The driver is mounted into an enclosure which houses a large opening, port, vent or slot that extends into the cabinet a specified length. The length and area of this vent are extremely critical to the proper function of a 4th order enclosure. The port and driver contribute together to provide the desired response characteristic. The driver is generally mounted with the front facing outwards, but is not restricted to this method only. The vent which extends into the cabinet tunes the enclosure to a specific frequency (known as fB) thereby acting as a high pass filter on the driver. Driver excursion is at its minimum at fB where the vent then takes over and provides most of the output. Cut-off rate below fB is 24 dB/octave but can be varied up or down 5-6 dB depending upon the exact tuning frequency and volume of the enclosure. There are various types of alignments that all fit into the ported 4th order cate…

Subwoofer Design - Order Acoustic Suspension

Order Acoustic Suspension Basic Theory:
The driver is mounted in a sealed, airtight enclosure, generally with the front of the driver facing outward but is not restricted to this method only. The volume of the enclosure is chosen to achieve a desired system Q which defines the response characteristics of the driver and enclosure. Q values may range between the 0.5 and 1.5 - with 0.5 being overdamped, 1.5 being underdamped, and 0.7 being critically damped or flat. The total system Q (also known as Qtc) is dependent on 3 things: the volume of enclosure, the T/S parameters of driver and internal treatment compounds. A a general rule only, sealed enclosures may be best suited for drivers with an EBP (Efficiency Bandwidth Product) of 50.0 or lower and drivers with Qts values above 0.40 but is not restricted to these exact values. EBP is calculated by taking the the fs of the driver and dividing it by the Qes - therefore EBP = fs/Qes. The cutoff rate is typically 12 dB/octave below f3…