The Loud Speaker Kit S250 Subwoofer
Review date: 4 July 2003.
Last modified
22-Feb-2013.
A lot of PC users think they know what a subwoofer
It's that little box under their desk, connected to the satellite
speakers on either side of their monitor, right?
Lots of &multimedia& speaker systems, and small pseudo-hi-fi rigs as
well, have a &subwoofer& that's the size of one to three stacked shoeboxes.
Some of these little things do a surprisingly good job of reproducing mid-bass
frequencies, considering how small and light and cheap they are. Many are
pretty darn ordinary, though, even after you make such allowances.
A real subwoofer is a speaker that reproduces frequencies below
those a normal woofer can handle. A &normal woofer& is not one of
the drivers in a PC it's a six to twelve inch diameter
driver, as seen in regular hi-fi speakers. Getting below that range means
response below 60Hz, at the very least.
A sub needs a frequency range that reaches up to about 100Hz,
if you want to be able to use it with small bookshelf speakers (which have
little performance below 100Hz of their own). But many buyers of serious
subwoofers are just looking for sub-60Hz performance to supplement a speaker
system that's already doing pretty well bass-wise.
Below 60Hz is where the fundamental frequencies of thunderous explosions,
deep organ notes, water-rippling dinosaur footsteps, deeper-pitched kick
drums, and similar coffee-table-rearranging sounds live. You can still hear
all of those things through the dinkiest of speakers, but all you're getting
in that case are the higher frequency components of the sound. You don't
feel the visceral kick of the bass drum, but you hear every other part of
the sound, so you still know what it is.
Because the human brain is so good at filling in bass (and treble, for
that matter) that it knows ought to be there, it's hardly essential
that you have a speaker system that can reproduce the full range of audible
bass frequencies, right down to the 20Hz pitch that's usually quoted as
the bottom limit for human hearing. Quite a lot of source material doesn't
have no subwoofer's going to do much if your
speakers spend their time reproducing
operas. Also, if you've got a very small or very large listening room, a
monster subw the lowest bass a room can support is
determined by its dimensions, so bedsit-dwellers have a reason besides the
possibility of being lynched by their neighbours for not using a thousand
watt horn-loaded bass gorilla as a coffee table. Opening the windows only
achieves so much.
If you do want solid bass all the way down, though, and have a
normal-sized room to listen to it in, a subwoofer is a good way to get it.
And a good subwoofer can slot into practically any sound system -
regular stereo, home theatre, even computer.
Getting a quality sub into your living room, computer room or bathroom
(I'm not judging anyone) for a reasonable price, though, is tricky.
Amplified (active) subs worth bothering with start from about $AU1000
(about $US680, as I write this), and you can pay a lot more to get
something really foundation-shaking.
About $AU1200. B&W
? $AU1300 or so. JMLab
$AU3000-odd. Krix , made right here in Australia? $AU3500. Meridian
? $AU4400 or
This is where kits come in.
A speaker kit gives you all of the parts you need to make a functional,
though not necessarily very aesthetically appealing, speaker of far higher
quality than you could buy pre-built for the same money. All you need to
build most speaker kits is a screwdriver, some wood glue and a few spare
Here in Australia, the inventively named company
a comprehensive line of high quality kit speakers. I
one of their cheaper products, the M4 Mini Monitors, a while
[UPDATE: As of 2012, The Loud Speaker Kit
as of early 2013 they're back under new management, though not with
a full line of products yet. There are
both here in Australia and overseas. It can also be
to design your own speakers from scratch!]
is, right now, the biggest subwoofer kit they make. Build it, and
you get a 30 kilogram (66 pound) active subwoofer with the specs to mix
it with the big boys. But it only costs $AU999, plus delivery.
(Delivery, by the way, costs $AU13.90 for Melbourne customers and $AU19.90
to me here in S other shipping rates are
but customers outside Australia need not apply.)
What you get
In the S250's imposingly large shipping carton, there are a couple of
smaller boxes...
...and there's this.
The S250's panels are all pre-cut, of course, with rebates that let them
fit together quite precisely without fasteners to pin them while the glue
Do-it-yourself speaker builders without perceptible woodworking skills
often construct basic butt-jointed cabinets that are neither pretty nor
particularly strong. Been there, done that. Such cabinets often need to
be held together by screws and/or corner braces as well as glue. You'll
find none of that kludgery here.
The panels are, of course, made from
there is no finer material for sanely-priced rectangular speaker boxes (although
many homebuilt subwoofers these days use
The S250 box needs no internal reinforcement, partly because it's relatively
small (450mm high by 400mm wide by 400mm deep, which is 17.7 by 15.8 by
15.8 inches), and partly because the panels are one whole inch thick. Subwoofers
need to be built like brick ablutions blocks, because they spend a lot of
time trying to shake themselves apart. Assuming you do your gluing right,
the S250 is quite solid enough.
The robustness of the panels makes a big contribution to the weight of
this subwoofer. Almost half of its mass is the box.
The green fluff in the background of the above picture is Dacron wadding,
which The Loud Speaker Kit
isn't gen-u-wine
of adequate quality for the task. That task is slowing
down and mildly soaking up sound waves inside the box, to make it seem a
bit bigger to the driver, and dampen resonance.
The public relations department.
This hefty item (its magnet assembly is big, but looks bigger, because
it's got a protective rubber cap over it) is a 12 inch, dual
puppy with a 600 watt power rating. Both
versions of it have achieved a certain measure of fame.
It's made by &Dayton Loudspeaker Company&, which is the
of respected US speaker component suppliers
These Dayton drivers are generally recognised as providing an excellent
price/performance ratio. They're not up there with the European exotics
(this one only has a stamped metal frame, not a cast one! The very
idea!), but they're priced to move.
the Parts Express page for this driver.
The monstrous 600 watt power rating goes with a resonance below 22Hz
(it's very hard to get response out of a speaker that's much lower than
the resonant frequency of its bass driver), which will lead audio aficionados
to expect a fairly lousy
figure. Which, indeed, this driver has. It's sacrificing
noise-per-watt for bass. N More Power can solve that problem.
The big domed dust cap conceals a lot of the Dayton driver's cone, which
is made from &
impregnated& paper. The word &impregnated& implies that the paper's been
saturated with liquid Kevlar, or something, but I think it's actually just
got Kevlar fibres mixed in with the much weaker cellulose ones.
Paper is, by the way, a perfectly good material for speaker cones, all
by itself, because it's light and stiff. The various treatments used on
paper cones (polypropylene coating is a popular cheap one) are there primarily
to enhance the paper's toughness and moisture resistance, not to compensate
for any inherent acoustic shortcomings.
T two sets of shiny spring terminals.
Dual voice coils are commonly seen in drivers made for car audio applications.
Two separate coils are wound on the one former inside the magnet assembly,
and you can connect them in parallel to halve the speaker's apparent
(two eight ohm coils in parallel give a four ohm speaker),
or connect one of them to each output channel of a stereo amplifier.
That's a bad idea if the two channels are delivering significantly different
signals, since the two coils will fight each other, but bass is almost always
monophonic, so this problem doesn't often arise.
The S250's efficiency is further limited by its simple
cabinet - no
or other tricks. Sealed enclosures are the simplest
kind of bass box, and are very easy to design - the bigger you make 'em,
the more bass you get, end of story - but their efficiency is lousy. Ported
speakers give you more sound from your electricity.
Even in a sealed box, though, if you feed this driver with a reasonably
hefty amp, it'll still be more than capable of loosening the ceiling paint
in anybody's lounge room. I speak from experience.
In the S250, the voice coils are connected in parallel, and driven by...
...this. A 275 or 250 watt (depending on how you measure it) fully integrated
&Plate amps& like this one are the subwoofer-project-builder's friend.
One simple unit turns a box and speaker into a full-function, flexible,
configurable active sub, which is the best of the three kinds of subwoofer.
The simplest kind of subwoofer is the passive type. It's just a speaker
in a box with terminals, operating in the same basic way as other passive
speakers. To get it to make a noise, you have to connect it to an amplifier.
This is all very well if you've got a multi-channel surround amp with
a subwoofer channel, or if you're happy to deal with the processing and
amplification yourself using separate boxes (dusty old
are popular candidates for repurposing into subwoofer amps),
but it's not a plug-and-go option at all.
Many passive subs have onboard
(also passive, like the crossovers in ordinary passive speakers)
and may have output terminals for satell those ones
can just be plugged into the speaker wires from any amplifier and, if you
use them with appropriate satellites, will work fine. They won't be running
from a separate Low Frequency Effects ()
channel then, though.
Then, there's the active sub, with an amp but not necessarily with much
in the way of brains. You have to feed it a signal that's been pre-processed
to some extent - the sub will probably have its own level control, but won't
necessarily have an onboard crossover or any other controls.
And then, there are subs that use integrated amp modules like this one.
It's a featureful gadget.
From top to bottom, you've got the power switch (you can turn the sub
off, or on all the time, or put it in &Auto& mode where it powers up when
it detects a signal and shuts down again after 15 to 20 minutes with no
signal) and a couple of sets of RCA connectors. They let you hook the sub
up to dedicated home theatre systems (which usually only have one RCA output
for the subwoofer, since it's not a stereo channel), or to anything else
with a line out, and then pass the signal through to another device. So
you can easily integrate this sub into pretty much any audio rig, including
a PC sound system.
If... you dare.
Below the switch and the RCA connectors, there are three knobs. Level
is the sub's master volume control. Crossover lets you set the point above
which the amp module's 12dB-per-octave filter attenuates the treble, from
40Hz to 160Hz. If you've got big beefy speakers already then 40Hz is likely
if you've got dainty bookshelf speakers, then 100Hz or higher
will be in order. Higher crossover frequencies make the sub's location more
obvious - 100Hz isn't very bassy, and 160Hz is actually only a bit below
the E below middle C - but it's better to have the sub playing some mid-bass
and giving its position away than to leave a wide trench in the system's
frequency response.
And then, there's the phase control. It determines the relationship between
the subwoofer's cone motion and the driver motion of the other speakers
in the system. That lets you compensate for subwoofer placement, if its
compression waves aren't lining up with the compression waves from the other
speakers at your listening position.
Subwoofers can play low enough that you can put them anywhere and not
be aware of their location, but if you get placement wrong some parts of
the room will be relatively bassless while others will sound like a car
belting down the highway with one window open. Phase adjustment gives you
more positioning flexibility, so you can minimise these &bass nodes& without
rearranging the whole room, knocking down a wall, or moving house to a football
Next up on the back of the amp, there's a set of screw terminals for
high level input and output - another compatibility feature. These terminals
work like the RCA connectors, but at speaker level, so you can just stick
the sub in the middle of your existing speaker wires. They've got a high-pass
crossover that protects the satellite speakers from bass they can't reproduce.
Sending high frequencies to a big driver that can't play them is pretty
much just a waste of time, but sending low frequencies to a little driver
that can't play them will deleteriously affect its fidelity, at best, and
can burn it up, at worst.
At the bottom of the amp panel, there's the IEC power receptacle, and
a voltage selector switch - the amp will work from 110/120V at 60Hz or 220/240V
Because of its multi-voltage compatibility, I think the exact same model
of this sub is sold in various different countries.
it is at Parts Express, for instance (it's got small but devoted
in the States);
here in Australia,
looks to be the exact same amp for $AU369 (catalogue number AA0501).
The Parts Express page for the amp links to
which contains detailed specs for the amp and also tells you how to set
it up for different amounts of bass boost by swapping a couple of resistors.
The amp that comes with the S250 is already tuned to match it, with 6
of boost at 30Hz.
The amp module also, by the way, has an integrated rumble filter, which
eats up any infrasonic frequencies in the program material. Ultra-low bass,
below the threshold of hearing, can't be effectively reproduced by any normal
speaker driver, but they'll try - and ultra-low bass is close enough to
direct current that it'll strain the biggest sub's voice coil forward and
backward, turning it into a toaster rather than a motor.
Rumble filters haven't been as important since most of the world stopped
playing LP records, but they can still only make a subwoofer sound better.
The pre-amp board's sealed to the mounting plate with a foam gasket,
and the plate itself has another gasket around it. T if
the amp board doesn't tightly seal the hole it mounts in on the back of
the box, the sub will whistle and buzz like crazy as it pumps air in and
out of the leak.
Putting it together
As speaker kits go, this is a surprisingly simple one. And not a tremendously
big one, either, by subwoofer standards. But if you're small, frail, or
just not at all accustomed to manhandling an object that gets closer to
its 30kg final weight with each construction stage, then you may want to
enlist some help.
Barring hernias, it should only take about an hour to get the panels
together, and rather less than another hour, after the glue's dried, to
get the electronics installed.
Before you start slathering glue on everything, the instructions tell
you to test-fit the panels so you can see where everything goes. This is
you don't want to have a crisis of confidence when you're holding
a panel that's dripping
down your arm.
During this stage, other family members may find it necessary to inspect
the box from the inside.
They may also sleep on the wadding, but always get up before you can
take a picture of them doing it.
The actual box assembly process is simple enough, provided you've done
this sort of thing often enough before that when you read instructions which
tell you to use amounts of glue described with words like &copious&, &ample&,
or &generous&, you know that what they actually mean is &well, not that
much, obviously&.
Once the box is assembled, the instructions say clamping it while the
glue sets is optional. But this thing needs to be strong, so it helps
to have at least a couple of large-ish clamps handy.
I clamped the box front to back, as the instructions tell you to do if
you're going to clamp it at all, and I also weighed it down a bit with the
conveniently-nearby other components.
The boxed woofer and amplifier by themselves weigh about 14 I
added a couple of phone books for luck. That still isn't much vertical clamping
force for a box this size, but it's better than nothing.
After leaving the box overnight for the glue to set, it was time to install
the other components.
Here, I struck a couple of problems. Fortunately, ordinary customers
ought not to encounter them.
First up, the two sets of woofer terminals needed to be joined together
with a provided bit of figure-eight cable, and the wires from the amplifier
had to be stuffed into one of the terminal sets, too.
The link cable was just barely thin enough to fit through the holes in
the spring terminals, but there was no way to twist the amp wires onto the
link cable wires and end up with a bundle small enough to fit. I solved
the problem by clipping off some of the strands at that end of the link
cable, which is more than chunky enough to handle such abuse.
I'm assured that retail S250 kits have the amp wires pre-soldered to
the link cable, so it all goes together easily. The kit I got was a pre-production
My other problem was that the pre-drilled pilot holes for the eight driver
fixing screws were very, very driving the screws by hand was
practically impossible, and assaulting them with a power driver...
...sheared 'em off.
This is often quite easy to do with the anonymous low-quality black screws
that people commonly use to attach the screws are more
than strong enough to hold a driver on, but they've got poor torsional strength
and don't deal well with hard driving.
I wrestled a couple of sheared shanks out of the holes, filed down the
rest, turned the driver so its mounting holes lay between the failed screw
holes, drilled some more generous starter holes, and fixed it with some
better quality screws.
Other people ought not to have to do this, at least if The Loud Speaker
Ki they tell me they've sold quite a lot of S250's,
and only the sample they sent me has had this problem, as far as they know.
Fair enough.
Apart from these hassles, assembling the S250 was plain sailing.
The amp module screwed on with no trouble at all. I left it a tad loose,
and it whistled and flapped when I started testing the sub, but a swift
retightening fixed that.
So the S250's pretty large, yes. It's heavy, yes. But it's not a very
advanced project - you could certainly choose an S250 as your first speaker
If you want to leave the S250 cabinet without a finish, that'
it'll work the same. If you want it to look more professional and/or be
more resistant to high humidity, though, you'll need to cover it with something.
Paint, veneer, PA-speaker-style carpet, it's up to you.
The Loudspeaker Kit offer self-adhesive
, and currently have iron-on wood veneer on their
They also have basic clips-and-cloth grille kits to cover the driver
side of the speaker (you have to make your own frame). If you want something
more robust to protect the speaker cone from feet, claws or little fingers,
any decent electronics store should stock cheap stamped steel grilles.
, for instance, will sell
you a steel 12 inch grille and set of mounting bolts and
under $AU15. I'd be inclined to just get the grille itself and stick it
to the front of the drive that avoids drilling the
front panel for the T-nuts and then caulking the screws into them to stop
Alternatively, The Loudspeaker Kit will provide on request a variant
of the S250 that has the driver firing downwards. That makes it more of
a home theatre sub than a music one, if you believe What Everyone Says About
Subs, but I'm not convinced that anybody would be able to tell the difference
without looking. It ought to solve the driver vulnerability problem well,
for anyone who doesn't own ferrets.
Listening tests
The Dayton driver has an unusually stiff suspension - the flexible part
of the driver that connects the cone to the frame around its edge and around
its neck, inside the speaker. This means it benefits from a few hours of
gentle exercise, to loosen the suspension up. I fed it a 25Hz sustained
bass note and left it throbbing away at medium volume all day, giving the
vague impression that a large diesel engine was idling somewhere in the
After that, I played with location and alignment and control settings
a bit, until the sub blended into the background as it should.
The idea of a subwoofer is that you shouldn't know it's there. You may
notice that the floor's moving rather more than it did the last time you
listened to a spot of
or ), and your home theatre
may suddenly sound a lot more like a multiplex, but the sub shouldn't jump
out and say hello.
If you ask it to, though, it certainly will.
Those who're tempted to wind everything up to eleven and see what the
heck happens may well give themselves a rather nasty surprise if they try
it with a Real Sub like this one. It's all a bit of fun when you're only
fiddling with an over-specified, over-pumped, over-grown set of computer
speakers like the , but if
you try the same thing with the S250 you'll discover that a
of &at least 105dB at 20Hz& means that anybody who walks through
a bass node in your listening room may suddenly find themselves swallowing
their fillings.
There are, undeniably, people who enjoy that feeling. Someone
must buy those &Bassy McBass and His Bass-Bumping All-Bass Big Bass Band
(Extra Bass Mix)& CDs and play them as they're meant to be played, through
at least six 18 inch subs in the back of a
If that's what you're into, then an S250 will give you a not dissimilar
experience in the privacy of your home.
All of those tracks just sound like someone diddling the bottom register
to me, though, so I stuck
to more mainstream program material in my testing.
The S250 turned in an excellent performance on a variety of bass-heavy
music and movies. Some of my test material turned out to be rather less
bass-heavy than I'd thought, from listening to it on lesser speakers and
that's not the S250's fault. The sub did justice to everything
that had low bass. And the phase control worked - though, since I
ended up lining the sub up with the main speakers, I left it on its zero
setting in the end - and so did the crossover control and the auto-power-on.
An LED above the power switch glows red when the sub's in standby and green
when it's on, so it's easy to see when it's detected a signal.
Thanks to the amp module's 30Hz bass boost, this sub definitely does
have serious output at 25Hz and below. So I think it'd have to be a darn
picky music-or-movies enthusiast who wouldn't find it adequate for their
It's unfair to directly compare kit speakers with pre-built ones. The
building process, for well designed kits like this one, isn't a big deal
for anyone slightly handy. But neither is one of these things a plug-and-go
experience.
Pre-built speakers will also come with at least a cheap vinyl veneer
a lot of expensive subs have gorgeous real wood veneers, or are
even made from solid timber, not &engineered wood& like MDF.
If you ask me, though, these caveats aren't serious when you look at
what you're getting for the money with the S250.
If you like the idea of the S250 but still want more, you'll soon be
able to get it. The
kit is coming, with a bigger ported cabinet for even more bass
extension, and substantially higher efficiency, for $AU1299. Threshold of
pain and broken filaments in every light bulb in the house, here we come.
I'll settle for the S250, though. It's a manageable size, it's got slabs
of power despite its basic efficiency limitations, it goes together easily
enough, and it costs little more than the most basic serious pre-built subs.
Which it outperforms by miles.
Highly recommended.
Review S250 kit kindly provided by
[UPDATE: As of 2012, The Loud Speaker Kit
as of early 2013 they're back under new management,
though not with a full line of products yet. There are
both here in Australia and overseas. It can also be
to design your own speakers from
(and no-one gets hurt)
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