SV Subwoofers (SVS) is a purveyor of subwoofers only on
the Internet, although they may be selling at dealers soon.
Their products are notorious for great sound, great
build, and fine value.
For a couple of years, SVS's subs were cylindrical
tubes covered by a sock, the driver mounted at the bottom, with the port at
As their subs got more and more powerful, it was only a
matter of time before they decided to build a statement piece that could
blow the walls out. Because multiple drivers would be employed, it was
necessary to move into a box design, rather than the tube.
The SVS B4-Plus is the result of that effort.
The B4-Plus is definitely a box, a very big box. It has four
12" long throw drivers, each with a 2" voice coil and large strontium
ferrite magnet (photo shown below).
The drivers are configured as dual push-pull,
with two drivers mounted facing outward on the left and right sides, and two
drivers facing inward, mounted in a center chamber (bottom photo below). Four very large ports
are mounted on one of the sides (photos shown below). The enclosures come in
gloss maple veneer, with other colors as options. I thought it might not be
very spouse acceptable, because of its size, but my wife commented on how
beautiful it was, so maybe she is getting used to big speakers around our
A set of speaker binding posts are mounted underneath the left side of the
rear enclosure panel (just to the left of the logo in the left-hand photo
shown above). The opening to the center chamber is covered by a grille,
shown in the right-hand photo above.
The B4-Plus can be purchased with or without a power
amplifier. Since you will need a big amp to drive this, and since SVS
supplies power amplifiers at a very good price (about half MSRP), it is
prudent to order the B4-Plus with a power amp.
In our case, we obtained the B4-Plus with a Crown K1 fully
balanced stereo power amplifier, rated at 1,500 watts RMS into 4 Ohms, in
bridged mode. The front of the K1 is shown below. It has an on/off toggle
and dual volume controls. When in bridged mode, you just use the volume
control on the left. There are several LEDs on the front, which light up
when there are various overload issues. These amplifiers are used by rock
groups in concerts, and they likely overdrive the amps, so that is why there
are so many protection indicators.
The rear panel of the K1 has Balanced XLR as well as
1/4" phone jack inputs for each channel. There are slider switches to select
the input sensitivity, bridged mode, and to have a single input go to both
channels. For our review, we used bridged mode and 1.4 V input sensitivity.
Bridging requires that you use the two red + binding posts shown in the
photo, to drive the subwoofer. The - binding posts are not used in this
case. Channel 1 input is used in bridged mode.
From my listening experiences with the B4-Plus, it is
obviously the most powerful subwoofer ever constructed for consumer use. It
plays loud and deep. Movies such as "Pearl Harbor" just explode into the
room. Not only explosions from bombs and torpedoes, but the low frequencies
from machine guns have tremendous impact.
One of my favorite home theater gadgets is an Audio
Control Phase Coupled Activator. It takes a low frequency and creates a
sub-harmonic at half that frequency. So, if the sound track has some 40 Hz
explosion sounds, the PCA adds in some 20 Hz. This drives some subwoofers
crazy, since not all of them can handle material down around 20 Hz, but the
B4-Plus did not flinch.
"Daylight" is another of my favorite movies to test a
subwoofer, even though it is not a very good movie in itself. The scene
where explosions occur in the tunnel can bring many subs to their knees.
But, the B4-Plus, being the standup fellow it is, just blew through all of them.
I am surprised someone has not tried to use the B4-Plus as a termite
exterminator, because I think any that were in my walls took a long hike
after that test.
I watched rental movies using the B4-Plus, along with other
movies from my collection such as "Patriot Games", "Air Force I", and
"Phantom Menace". All were enjoyable, with no boominess from the
B4-Plus. At sane
volumes, it just coasted along. Because the Crown K1 does not have a
crossover built-in, I used a 50 Hz crossover setting in my Theta Casablanca. SVS can supply a Rane electronic crossover if you need one.
On the Bench
I tested the B4-Plus with no foam plugs, since this product
is made for high SPL. With foam plugs inserted into the ports, the B4-Plus will play
deeper (16 Hz), but not as loud. I took these measurements outdoors with the
microphone at 1 meter from the side with the ports.
At 15 Hz and 100 dB SPL, THD was quite high. This is
because the B4-Plus, without foam plugs, has extension to 20 Hz, but not lower.
At 20 Hz, THD was a lot more manageable at a little
over 3%. I was able to get 110 dB at this frequency before the amplifier
shut down for a few seconds. Keep in mind that because I tested this
subwoofer outdoors, there is no "room gain". So, if the sub were in a room,
you could likely expect another 10 dB maximum SPL. This means that you
would not have to turn the volume up as much, so the distortion would be
even lower than shown here.
At 25 Hz, THD is coming down. I got a maximum of 115 dB
here, before the amp shut down.
At 31.5 Hz, THD was less than 2%. I got 121 dB at this
frequency at maximum volume control setting, but the amp did not shut down.
The B4-Plus obviously could take more power, but the K1 "only" delivers 1,500
watts. The K2 is rated at 2,500 watts if any of you dare to use it. The
is rated at 2,500 watts continuous, so it could handle the K2. SVS has even
used a Crown 5,000 watt amp with the B4-Plus, and found that, finally, the could
determine the sub's limits.
40 Hz at 100 dB produced only 1.2% THD. Maximum output
was 122 dB, and the amp did not shut off.
At 50 Hz, THD was less than 2% at 100 dB output. I got
122 dB at this frequency with the volume control turned all the way up. The
B4-Plus wanted more.
Quasi-anechoic frequency response showed a maximum at
about 60 Hz, with steady roll-off down to 20 Hz, using a 60 ms MLS window.
The impulse response, shown at the bottom, has three initial peaks,
representing the delay between the driver facing the microphone, the one on
the front, and the one on the other side of the enclosure. The large long
peak at 16 ms is probably cabinet resonance. The 16 ms corresponds with 60
Hz, and the frequency response shows the peak at that frequency. The
resonance could probably be tamed by placing a rubber pad on the top of the
enclosure and then sitting the power amplifier on top of the pad.
SVS has done it again. For anyone who wants to have the
Darth Vader of subwoofers, the B4-Plus is it. With almost unlimited power and low
distortion, the B4-Plus is definitely one of the Masters of the Universe.
- John E. Johnson, Jr. -