Polk Audio holds over 45 patents for
advances in loudspeaker design and technology. Their products are distributed
throughout the U.S. and Canada and in over 50 other countries. So, in other
words, this is a big company.
The 12” driver features a huge foam surround, and a polymer composite cone with an inverted dust cap. The driver mounting plate is covered with a decorative rubberized foam strip, so I didn’t attempt to remove the woofer.
The external dimensions, including the feet, grille, and amp controls, are
approximately 16-1/8" high, 15-1/8" wide, and 18-3/16" deep. The sub weighs
about 40 pounds uncrated. The MDF cabinet interior is a bit unique, using the
top of the slot port for a horizontal brace, which in turn supports two
vertical braces. Polyfill is stuffed between the two vertical braces. There
are four hard plastic feet mounted on the bottom of the cabinet. I never heard
any vibration from the feet, and the sub didn’t wander on my hard laminate
- On/Off Main Power Switch
Peak Dynamic Output: This test measures how loud the subwoofer can play across its pass band with a short-duration signal representative of typical music and movie transients. Frequency response sweeps were conducted at progressively louder (2 dB increments) levels until dynamic compression was noted. The green curve (midle curve in the graph shown below) represents the maximum uncompressed dynamic output of the PSW505, with 105 dB at 70 Hz, and 95 dB at 30 Hz. The next higher curve (purple) showed dynamic compression, and the test was subsequently terminated.
Power Compression: This test measures how loud the subwoofer can play across its pass band with a longer duration signal. A sustained bass passage in an action movie can create excessive heat in the voice coil, reducing longer term output capability. Power compression was evaluated with a slow reverse sine sweep from 100 Hz down to 10 Hz. Sweeps were conducted at progressively louder (2 dB increments) levels until power compression was observed. The PSW505 held steady up to the purple curve in the graph shown below, with 102 dB at 70 Hz, and 93 dB at 30 Hz. The next higher curve (gold) showed power compression, and the test was subsequently terminated.
Total Harmonic Distortion (THD): Harmonic distortion occurs when multiples of
the fundamental signal are produced due to non-linear driver behavior. A
subwoofer with low THD will sound clean and distinct, especially at the
deepest frequencies. THD was evaluated with sine waves (about 5 seconds
duration), and was limited to approximately 10% unless otherwise noted. Clean
output from the Polk was low in the 20 Hz - 25 Hz region, but it performed
considerably better in the 32 Hz - 80 Hz regions.
Bandwidth Linearity: Bandwidth linearity is
calculated by dividing the average distortion limited SPL by the maximum
distortion limited SPL, and expressing the result as a percentage. A score of
100% means the subwoofer exhibits perfect output linearity across a given
Group Delay: A sufficiently large and abrupt phase shift may cause the
perception of time smearing at the affected frequencies. Group delay is used
to quantify this phenomenon, and was calculated from the phase response for
select music notes. The approximate audibility thresholds are based on
extrapolations of existing group delay audibility studies. Group
delay from the Polk 505 remained below the approximate audibility thresholds
at each tested frequency.
Impulse Response and Spectral Decay: The impulse response (black line) shows transient overshoot and system ringing for about 40 ms. Spectral decay was evaluated to the –35 dB mark, relative to the test volume. Several minor system resonances were noted in the 20-100 Hz bandwidth. The largest resonance dropped below the test floor after about 110 ms.
In-Room Frequency Response
As expected, room gain helped considerably to improve deep extension, with the
Polk holding flat to about 25 Hz, and then dropping to –10 dB at 20 Hz. The
response also showed a pronounced peak in the 55 Hz - 90 Hz region (orange-gold
line in graph shown above).
This peak is the combined result of room acoustics, asymmetrical filters in
the digital bass management circuit, and the general shape of the
quasi-anechoic FR (which also plateaus in the 55 Hz - 90 Hz region).
Dynamic Impact 3.00
4) Los Lonely Boys - Or Music, LLC / Sony Music
Entertainment, 2003. The 505 had no trouble handling the aggressive electric
bass guitar work on this Latino rock CD, sounding natural with good
distinction of notes and solid extension on low E (about 40 Hz).