Founded in 1974, Krix is a loudspeaker manufacturer located in South
Australia. They have a successful line of speakers for consumers and also
for commercial theater installation.
The Seismix 3 Mk2 is the smallest of three subwoofers offered by Krix, and
is designed for small to medium size rooms. MSRP ranges from $975 to $1,375
depending on the finish, which includes vinyl as well as wood veneers.
The MDF cabinet interior is neatly lined with
polyfill, and does not contain any bracing. The exterior of the review unit
is nicely finished
in a real beech veneer on five sides, with the rear panel finished in a
The grille frame is made from lightweight wood, and is
attached to the cabinet with a plastic pin ball/socket arrangement. The
speaker cut-out is irregularly shaped, to reduce the potential for
resonances. The close knit fabric is stretched tightly over the frame and
secured with adhesive. A “Krix Loudspeakers” metal nameplate is located on the
grille at the bottom center.
There are four large doughnut-shaped soft rubber feet
mounted on the bottom of the cabinet. The rubber feet worked well on
carpeted and hard surfaces alike, with no buzzing, vibrating, or wandering.
This is a high quality floor interface solution.
The Seismix 3 Mk2 is a bass reflex design, and the woofer and
vent are both front firing. The plastic vent is flared at both ends, with an
inner diameter of 4" and an outer flare diameter of 5”. There is also
a wooden dowel mounted inside the cabinet which extends partially up the
vent. This dowel prevents small objects which are placed into the vent from
falling completely inside the subwoofer cabinet, which would then
necessitate removal of the woofer for retrieval.
The 10” woofer is secured with four T-15 head wood
screws and features a synthetic rubber surround, impregnated pulp cone with
inverted dust cap, a shallow stamped steel basket, soldered amp leads, and a
double stacked magnet structure. I would estimate the woofer weighs about 7
- 80 Watts Continuous, 200 Watts Program
- On/Off Power Switch
- Auto-On (15 minute delay before shut-off)
- Low Level L/R RCA Inputs (gold plated)
- Input Sensitivity Switch (9mV on “Hi” and 320 mV
- Low Pass Filter (22-120 Hz, continuously variable,
no disable switch)
- High Pass Filter (22 Hz non-user adjustable)
- Phase Control (0/180 switch)
- Overload Clipping Protection (with indicator light)
- Fuse (1 amp) Protection
- Detachable Power Cord
The control layout is logical, and the rotary knobs
move smoothly with a slightly heavy feel. I was pleased to note a beefy toroid power transformer.
In my opinion, toroidal transformers are better than standard
(El, EL, etc.) laminated transformers due to their inherent phase
cancellation of noise and radiation products. I also noted two 6800 uF
capacitors. There is no heat sink, and the amp got hot during the ground
plane session, but stayed reasonably cool during normal use. The detachable
power cord is heavy duty and grounded.
I liked the amplifier overload protection circuit. It
softly ramps down the subwoofer output when the amp is driven into an
overload or clipping situation. I was only able to engage the overload
protection circuit during the ground plane session, and never during normal
The Hi/Lo input gain switch is a nice feature for
when your subwoofer pre-out signal is weak. The Hi setting allows the amp to
be driven to full power with only 9 mV of input.
Even with the input sensitivity switch set to Hi, the
auto-on circuit was a bit hard to initialize, requiring a boost in system
volume. There is a 15 minute no-signal delay before the amp shuts back off.
Ground Plane Objective Testing and Measurements
All objective tests were conducted using ground plane methods with
the microphone facing the woofer and vent, at a distance of 2 meters from
the acoustic center of the enclosure. Control settings: low pass filter set
to high, gain switch set to Hi, and phase control set to 0 degrees.
Frequency Response: A short-duration (about 1.5 seconds), digitally
synthesized logarithmic sine sweep was used to evaluate the frequency
response of the subwoofer. The Seismix 3 Mk2 frequency response measured
3 dB from 38 Hz -127 Hz, and was characterized by a plateau in 50 Hz - 70 Hz region
with a falling response above and below those points.
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 increment) levels until dynamic compression was
noted. The purple curve represents the maximum uncompressed dynamic output
of the Seismix 3 Mk2, with 103 dB at 60 Hz, and 91 dB at 30 Hz. Minor
dynamic compression was noted below 40 Hz on the next higher curve (gold).
Power Compression: This test measures how loud the subwoofer can play across
its pass band with a longer duration signal. A sustained signal (like the
avalanche scene in the movie Triple X) can create excessive heat in the
voice coil, thus reducing the output capability of the subwoofer.
Power compression was evaluated with a slow (about 30 seconds) reverse sine
sweep from 100 Hz - 20 Hz. Sweeps were conducted at progressively louder (2 dB
increments) levels until power compression was observed. The Seismix 3 Mk2
held fairly steady up to the green curve, with a maximum of 98 dB at 60 Hz,
and 87 dB available at 30 Hz. The next two higher curves (purple and gold)
showed more severe (3-4 dB) power compression in the 30 Hz - 40 Hz bandwidth, 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 steady (5-10 seconds) sine
waves, and was limited to 10% unless otherwise noted.
Distortion-limited output was low in the 20 Hz - 25 Hz region, partially due to
the high-pass filter engaging at/near 22 Hz. In the 32 Hz - 80 Hz area, the Seismix 3 Mk2 posted more impressive numbers, and the sophisticated amp
limiter did a good job of holding distortion to 6% or less.
||6.1% amp limited
||4.9% amp limited
||4.6% amp limited
||2.5% amp limited
||1.7% amp limited
Bandwidth Linearity: Developed by Tom Nousaine, 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
Phase Response and Group Delay: This test measures
the amount of phase shift which occurs across the pass band. A minimal phase
shift means that all the bass frequencies will be perceived as time
coherent. 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 for select musical note
approximate audibility thresholds are based on extrapolations (John Murphy)
of existing group delay audibility studies. Group delay from the Krix
remained below the approximate audibility thresholds at all significant
musical bass frequencies.
||Approx. Audibility Threshold
|F2 / 87 Hz
|G1 / 49 Hz
|C1 / 33 Hz
|A0 / 27 Hz
|E0 / 21 Hz
Enclosure Tuning Frequency: A phase wrap was noted at 30 Hz, indicating the
tuning frequency of the enclosure. This was also verified with a close-mic
sweep of the woofer.
Impulse Response and Spectral Decay: The impulse response (black line) shows
transient overshoot and system ringing for about 50 ms. Spectral decay was
evaluated to the –35 dB mark, relative to the test volume. This test floor
was still well above ambient noise levels, ensuring the decay plot was not
contaminated. Several minor system resonances were noted in the 50 Hz - 140 Hz
region. The largest resonance dropped below the test floor after about
In-Room Frequency Response
To simulate a typical user set-up, the Seismix 3 Mk2 was placed in the front
left corner of my 2,000 ft3 home theater room. For digital bass management,
all speakers were set to small with a crossover of 80 Hz. The in-room FR
sweeps were processed through the pre/pro with only the main speakers and
the subwoofer operating. Setting the phase to 0 degrees provided the best
results. The in-room FR was measured at three popular listening positions,
all about 12 feet from the subwoofer. The three curves were then combined to
create an average response curve.
As expected, room gain helped to considerably shore up the low end, with the
Krix holding flat to 30 Hz, and meeting its rated deep extension of –6 dB at
22 Hz. At each in-room test location, the Seismix 3 Mk2 showed a pronounced
peak in the FR at 60 Hz - 65 Hz (blue line). Considering the shape of the ground
plane FR (which also peaks in the 60 Hz - 65 Hz region), this was expected.
Setting the low-pass filter to the lowest setting helped some (green line),
but didn't completely eliminate the response peak.
The 60 Hz - 65 Hz peak tended to dominate the acoustic signature, creating a
chesty and congested sound on music. I normally avoid using a parametric
equalizer to tweak review subwoofers, but in this case, it was necessary.
After 10 minutes of running in-room sweeps and adjusting two bands on the Rane PE-17, I achieved an in-room FR of 25
Hz - 100 Hz
2.5 dB (purple line).
Now the Krix came alive, with a natural and balanced bass presentation.
I played several action-oriented DVDs, evaluating the Krix for dynamic
impact, sustained output capability, indications of audible distress, and
deep extension. My overall subjective home theater ratings for the Seismix 3
Mk2 are provided in the table below.
I selected the Hellboy DVD for a more detailed demo. To set the playback
level, I increased the master volume until the Krix exhibited some minor
distortion and dynamic compression artifacts, and then I backed off 2 dB. I
measured SPL peaks at the listening position with a sound meter set to
C-weighted fast. The Krix performed well on most bassy passages in
Hellboy, displaying good dynamics and decent extension to about 25 Hz. It
missed some of the visceral infrasonics on the ice prison space scene,
though. I noticed some power compression on the extended (25 second) fiery
blast scene, where the Krix failed to break 100 dB at the 1:38:50 climax.
After a cool down period, I replayed the last 5 seconds of that scene, and
the Seismix 3 Mk2 recovered nicely, punching out a solid 104 dB peak at
|Ice Prison In Space
|Hellboy Drops Dumbbell
|Removes Tomb Cover
|Pendulum Swings By
|Portal Lock Opens
With the parametric equalizer in the loop, I evaluating the Krix on several
music selections for pitch, definition, coherence, balance, and overhang. My
overall subjective music ratings for the Seismix 3 Mk2 are provided in the
table below. Also provided below are some listening notes from a few CDs.
1) Gladiator soundtrack - Hans Zimmer, Decca Records, 2000. The Seismix 3
Mk2 showed decent focus and separation on the deep, throbbing bass hits at
the 6 minute mark of Barbarian Horde.
2) Time Out - The Dave Brubeck Quartet, Columbia Records/CBS, 1959 (1997
Direct Digital Remaster). The Krix did a credible job conveying the delicate
timbre of the acoustic bass featured in "Three To Get Ready".
3) Kamkiriad - Donald Fagan, Reprise Records, 1993. The Krix occasionally
lost a bit of focus and coherence on the deepest electric bass notes in
“Springtime”, but otherwise performed well, providing good foundation to the
4) Everything Must Go - Steely Dan, Reprise Records High Resolution DVD-A,
2003. “Godwhacker” opens with a well recorded bass kick drum, and the Krix
displayed good impact with just a touch of overhang.
5) Flight Of The Cosmic Hippo - Bela Fleck & The Flecktones, Warner Brothers
Records, 1991. The Seismix 3 Mk2 displayed decent pitch and definition on
the fretless sliding bass of the title track.
While the Seismix 3 Mk2 is a little expensive for the performance it
delivers, I liked
the handsome looks, real beech veneer, quality amp, sophisticated limiter,
and the well engineered floor interface. A parametric equalizer will help
owners achieve the best sound quality from this subwoofer, particularly for
music applications. In my mid-size room, the Seismix 3 Mk2 displayed decent
dynamics and sufficient extension for most home theater applications.
- Ed Mullen -