Aerated Polypropylene (APP) Cone:
The Polk Audio SR5250's woofers are constructed of Aerated Polypropylene, a
mineral-filled polypropylene that has been "puffed up" with injected air to form
a honeycomb-like structure. The result is a stiff, lightweight material with
excellent damping qualities.
Surround: The cone is bonded to
the basket with a soft butyl rubber surround. The injection-molded butyl rubber
is tuned to absorb unwanted cone resonance. In addition, the surround is
resistant to ultraviolet rays, temperature extremes, and humidity to add to
the speaker's reliability and longevity.
Phase Plug: The bullet-shaped
phase plug in the center of the driver ensures a smooth, flat, off-axis
frequency response by preventing the high frequency sound waves emanating from
one side of the cone from interfering with sound waves from the other side of
the cone. The phase plug can be removed to convert the SR5250 into a coaxial
Basket: The woofer features a
high-mass cast aluminum basket. The basket and magnet cover are one piece with
heat sink fins that draw heat away from the voice coil, increasing power
handling and reliability.
Voice Coil: The voice coil is
wound around a 1-1/2" diameter low-mass, high temperature polyimide
former. The large diameter coil contributes to the high bass output and high
power handling of the driver.
Neodymium Magnets: The speaker
uses a Neodymium magnet, which has a similar magnetic flux density to a ceramic
magnet 10 times its size.
Mounting Rings: Mounting rings are
included which reduce the mounting depth and increase the mounting height, both
by 0.36 inches. The effective frame diameter of the woofer when using the
mounting ring is 6.298", meaning it covers a 6-1/2" or 6-3/4" speaker opening,
but the screw holes don't match either standard application.
5x7/6x8 Adapters: The
woofers can be mounted in many 5x7/6x8 applications when used with the supplied adapters.
Terminals: The woofers have typical
quick-slide terminals, and also have screw terminals which will accept bare wire
or spade terminals.
Ring Radiator Tweeter: The
SR5250 has a 22mm (7/8") Ring Radiator tweeter, the same type as used in
high-end audiophile home speakers. The Ring Radiator's ultra-light woven
diaphragm is supported at two pivot points, with the voice coil attached
approximately midway between the two pivots. Since there is a very small
diaphragm area that is unsupported, there is less opportunity for the
development of performance-robbing resonance. The phase plug, similar to the one
found on the woofer, prevents phase cancellations, so you get a flat, smooth
frequency response, both on- and off-axis.
Extended High Frequency Response:
The tweeter's frequency response goes well beyond 20kHz; to 40kHz overall
and to 30kHz at -3dB. This drives resonant peaks beyond audibility, and gives
the speaker more overall detail and lower distortion levels.
Dual Neodymium Magnets: The
tweeter has two Neodymium magnets to provide a powerful magnetic field for the
voice coil, while still maintaining the tweeter's compact dimensions.
Faraday Cap: The motor
structure includes a copper Faraday Cap on the pole piece to flatten the
impedance curve, lower distortion, and extend and improve high frequency
Mounting Options: The tweeter
can be mounted a variety of ways. When the speakers are mounted as
separate components, the tweeter can be mounted in a straight flush-mount cup or
in an angled flush mount cup. In addition,
you can remove the woofer's phase plug and mount the tweeter on the woofer as a
coaxial speaker. When configured as coaxials, the tweeter speaker wire is threaded
through the magnet and adds approximately 1/16" to the mounting depth. The tweeter
adds a little over 3/4" to the mounting height, for a total of 1.141
inches. The tweeter can also be mounted in the 5" x 7" adapter.
High Quality Components: The SR5250
crossover uses 1% tolerance resistors and capacitors to ensure the woofers and
tweeters are perfectly matched to provide a solid, stable, and consistent stereo
image. Air Core Inductors with Oxygen-free copper wire are used for wider
dynamic range, contrast, and punch.
Zobel Network: The crossover includes a
Zobel network, which flattens the system's impedance curve for a more efficient
power transfer and flatter response.
Bi-Amping: The crossover's circuit board
includes two jumpers which can be configured for single amplification or bi-amping.
You can independently drive the woofer and tweeter with separate amplifier
channels when the jumpers are removed. If driving the woofer and tweeter from
the same channel, the jumpers should remain installed.
4-Position Tweeter Levels: You can adjust
the output level of the tweeter at the crossover by positioning a jumper to one
of four positions: -3dB, -1.5dB, 0dB, or +2dB.
Crossover Slopes: The crossover includes a
2nd order, 12dB per octave low pass filter for the woofer, and a 3rd order, 18dB
per octave high pass filter for the tweeter. The crossover frequency for both
high- and low-pass filters is 4600 Hz.
Tweeter Protection: The crossover's
Tweeter Protection device limits the current flowing into the tweeter,
preventing damage to the tweeter when it is operated beyond safe operating
Heat Sink: The crossover is housed in a
heavy-duty solid cast aluminum chassis which acts as a heat sink for cooler
operation and longer reliability.
Tweeters (mounted separately):
||Straight Flush Mount
Angled Flush Mount
||0.826" (incl. grille)
Width, 2.375 Depth
Crossover: The crossover dimensions are:
- Width: 6.767"
- Height: 1.585" (chassis) / 1.890"
(overall, including knobs)
- Depth: 4.518"