HARMAN KARDON BETATWELVE
Manual de Servicio

SUBWOOFER ENCLOSURE TRADE-OFFS
Subwoofer enclosures are classified as sealed (acoustic suspension) or ported (bass-reflex), and can be built in many configurations. Here we discuss three popular box types and encourage you to compare their response curves, noting the differences in Beta Twelve output level and frequency response versus volume in sealed, vented, and single-reflex band-pass enclosures. A sealed enclosure is the smallest and simplest to build, with high power handling, good phase coherence, and the most predictable response, at the expense of somewhat diminished sound output. If amplifier power is not a concern, this is the best choice for most systems, providing the highest output at the lowest frequencies. A vented enclosure adds a port (or vent) tuned to the speaker�s resonance in the box to help boost sound output by �tuning� the rear sound waves so they add to the front ones. It is more efficient than a sealed box above the tuned frequency, but more difficult to build properly. For frequencies below the tuned range, output is lessened due to sound cancellation, and there is a 180degree phase shift at the tuned frequency. Other drawbacks are the increased box size for the added port and diminished power handling due to woofer over-excursion at frequencies below the tuned frequency. A single-reflex band-pass enclosure counteracts the sound cancellation properties in vented designs by isolating the subwoofer from the port within its own enclosure. It offers higher power handling, and an automatic band-pass response to help roll off higher frequencies. However, it has a 180-degree phase shift at the tuned frequency. Also, complexity and size are increased, due to separate front and rear chambers, and it requires adding substantial midbass drivers elsewhere in the car. We recommend a sealed enclosure for the Beta Twelve. Depending on your taste in music, you can select a box volume for a flat, enhanced, or extended bass response (see graphs on right). The flat response is optimum for all enclosures and types of music. The enhanced sealed box provides a �tighter� bass, great for rock and rap. An enhanced vented box has increased output, but with diminished transient response and power handling. The extended sealed box is more efficient at the lowest frequencies, providing added bass boost for jazz and classical music, but with diminished power handling. The extended response curve provides the best power handling for vented enclosures. For more help, please call Infinity technical support at: (800) 553-3332

BETA TWELVE SEALED ENCLOSURE

BETA TWELVE VENTED ENCLOSURE

BETA TWELVE SINGLE REFLEX BAND-PASS ENCLOSURE
L= length (see responses below)

L = length (see responses

Port

Port Beta Twelve
(side view)

Beta Twelve
(side view)

Beta Twelve
(side view)

below)

D = diameter (see responses below)

V

BOX

= Box Volume
(see responses below)

V

BOX

= Box Volume
(see responses below)

D = diameter (see responses below)

VBOXR = Box Volume Rear
(see responses below)

VBOXF = Box Vol. Front
(see below)

dB (Normalized)
0 Close-Field (In Car) -10 -20 -30 V
BOX

dB (Normalized)
Close-Field 0 (In Car) -10 *= 0.75 ft 3 -20 -30 VBOX*= 1.25 ft L = 15.00" D = 4.00 " Free-Field 10

dB (Normalized)
Close-Field (In Car) 0 -10 -20 -30 Free-Field VBOXF*= 0.70 ft 3 VBOXR*= 0.75 ft 3 L = 6.20 " D = 4.00 "

3

Free-Field

10

Beta Twelve Sealed Enclosure � Flat Response

50

100

500

1k

Freq. (Hz)

Beta Twelve Vented Enclosure � Flat Response

50

100

500

1k

Freq. (Hz)

10

Beta Twelve Band-Pass Enclosure � Flat Response

50

100

500

1k

Freq. (Hz)

dB (Normalized)
0 -10 -20 -30 VBOX*= 0.50 ft 3 Close-Field (In Car)

dB (Normalized)
0 Close-Field (In Car) -10 -20 -30 VBOX*= 2.50 ft L = 3.70 " D = 4.00 " Free-Field 10 50 100 500 1k
3

dB (Normalized)
Close-Field (In Car) 0 -10 -20 -30 Free-Field

VBOXF*= 0.70 ft 3 V *= 0.65 ft 3 BOXR L = 5.30" D = 4.00 "

Free-Field 50 100 500 1k

10

Freq. (Hz)

Freq. (Hz)

10

50

100

500

1k

Freq. (Hz)

Beta Twelve Sealed Enclosure � Enhanced Response
dB (Normalized)
0 -10 -20 -30 10 Free-Field V
BOX

Beta Twelve Vented Enclosure � Enhanced Response
dB (Normalized)
Close-Field (In Car) 0 -10

Beta Twelve Band-Pass Enclosure � Enhanced Response
dB (Normalized)
Close-Field (In Car) 0
3

Close-Field (In Car)

-10 -20 Free-Field -30

*= 1.20 ft 3

-20 -30

VBOX*= 1.75 ft L = 17.20 " D = 4.00 " Free-Field

VBOXF*= 1.00 ft 3 V *= 1.10 ft 3 L = 5.90" D = 4.00 "
BOXR

50

100

500

1k

Freq. (Hz)

10

50

100

500

1k

Freq. (Hz)

10

50

100

500

1k

Freq. (Hz)

Beta Twelve Sealed Enclosure � Extended Response
*If filling is desired, reduce box volume by 20%.

Beta Twelve Vented Enclosure � Extended Response
*If filling is desired, reduce box volume by 20%.

Beta Twelve Band-Pass Enclosure � Extended Response
*If filling is desired, reduce box volume by 20%.