THE ART OF BUYING A SUBWOOFER
What You Need to Know Before Buying a Subwoofer.
When deciding to upgrade your audio system, adding a subwoofer
can produce massive results. Adding volume at sub frequencies
is like adding a third dimension to your music. Whether you
are considering building a new audio system, or just adding one
(or more) subwoofers to your factory system, this addition will
give you the single, most significant sonic improvement. Simply
adding even a little bass will make a HUGE improvement.
I will never forget my first experience listening to the heart
pumping sound of bass. I was listening to my friend’s
newly installed system, (he had a couple of 12’s with a decent
size amps), and it was literally shocking how R-E-A-L it
sounded, how you could actually feel the music. I was completely
amazed that you could actually feel the impact of the woofers. From
that moment on I’ve been a car audio fanatic.
But, choosing a subwoofer can be confusing! There are a
few questions that you should ask yourself before actually running
out and buying woofers.
1. What type of sound are you looking for?
There are two main camps in the sound world: Sound Quality (SQ)
or Sound Pressure Level (SPL).
Sound Quality refers to just that, a very linear response
that is not boomy and is very controlled, especially when listening
to complex software. An SQ System generally uses a smaller
woofer and requires a smaller enclosure. A sealed enclosure
would typically work best for this application.
SPL, on the other hand, is for you “Big Bass Lovers.” If
you’re like me and like a lot of impact with your music (extended
bass response and 3 dB more efficient gain) then you’re probably
looking for a ported enclosure.
2. How does a sealed enclosure work?
Sealed enclosures are also known as “Acoustic Suspension” enclosures. When
a speaker is placed in a sealed enclosure, the pressure becomes
trapped in the box and restricts the cone movement, so the air
inside the enclosure acts as a spring. The smaller the enclosure,
the more pressure is exerted against the cone under movement. With
a sealed enclosure of predetermined volume, we can also predict
the cut-off frequency and Q* of the system.
Sealed enclosures will also forgive minor mistakes in design (up
to 10%), without major effects on sonic performance.
The real advantage is that it just consumes less space, not to
mention, it’s easier to design and construct. Choosing
a sealed enclosure will give you clean and accurate bass with good
low-end extension.
3. How
does a ported enclosure work?
Ported enclosures are very similar to a sealed enclosure in construction
but with an additional opening for an attached port. This
allows the rear-radiated energy to be phase inverted (matched in
time) and to become in phase with the energy from the front of
the speaker cone, essentially doubling the effective cone area.
 The main drawback with a ported enclosure is that the design and
construction are not very forgiving of errors. Unlike a sealed
box, you must determine a number of different parameters: the box
volume, tuned frequency, port area, and port length. But,
the advantage is huge; you will get more output with the same number
and size of woofers.
However, with all of that extra output there ’s always a
trade off. More bass naturally means more space. Generally
speaking ported enclosures will be to be 30% to 40% larger than
a sealed enclosure.
You’re probably thinking, can a ported enclosure sound as
good a sealed enclosure? The answer is, yes, but it’s different
in that it will have a slight peak around the tuning frequency
(35Hz) and roll off very quickly. Both types of enclosures have
true supporters. What you use really boils down to your application
and how they load in your vehicle.
4. How
much space are you willing to give up?
Now, that you have determined your music tastes, you will need
to decide which one of the enclosures will fit your needs, and
your vehicle. Let’s review: A) Sealed: Clean, accurate, with
a smooth roll off and small to medium sized enclosure or B) Ported:
Very efficient, extended output, (plays loud) and requires a medium
to large enclosure. The decision is yours, but keep in mind that
weight and space are at premium in vehicles over the past few years,
particular with the tuner crowd and their traditionally smaller
vehicles.
Before you make your purchase, it’s also good idea to also
find out how much air space and what type of enclosure is required
for your dream woofers. Most manufacturers will have both
specifications for Sealed and Ported applications. This information
can be found several ways: through your local dealer, the Internet
or by calling the manufacturer’s technical department. When
in doubt, ask your dealer to help you determine the best woofer(s)
for your application.
5. How much money should you spend?
This can be somewhat subjective, many believe that the more you
spend the more bass you will get. There definitely is some truth
to that, but I found that a lot of people get hung up on specs
that really don’t matter. For example I wouldn’t buy
a woofer strictly based on its peak power handling capability,
or by trying to match an amplifiers output power to a speaker input
power.
Here are three key subwoofer specs to look for.
- Fs: The frequency at which the woofer naturally like to resonate
(like a tuning fork). The lower Fs the lower the driver will
play naturally.
- X-MAX: The amount of the voice coil windings that overhang
the top plate of the magnet assembly. This shouldn’t be
confused with excursion. They are two different measurements
but go hand and hand. In most applications the larger the number
the better, think of it this way; woofers behave like giant air
pistons. The more the pistons move the more SPL you will create.
- “BL”: The “BL” product, is a measurement
of the force (power) generated by the speakers’ motor.
The more “BL” product the more control the woofer
will have over the cone.
6. Does the installation matter?
Absolutely. Unlike a home audio system where the installation
is essentially plug and play. In a home system installation
accounts for a very small percentage of the sound quality and is
pretty hard to screw it up. Most home receivers have everything
built into one unit and the engineers have taken most of the guesswork
out. There’s no level matching between components and definitely
no subwoofer enclosure building. In a vehicle it is much
different; the installation takes a lot more finesse and accounts
for about 80% of the success of how the system will sound. This
is why it is so important to spend the time and
money on how it’s put together.
In fact, the installation is more import than the product itself.
Think of it this way, if you build a house with a poor foundation,
the house will always have a poor foundation and will never be
able to support the house. If you are installing it yourself or
if you are going to have your local shop put it in, do a little
homework and it will go a long way. Make sure you calculate the
correct volume for your enclosure and use good quality materials
like MDF or Fiberglass.
7. Should you be concerned about safety?
Safety is one of the most over looked things in car audio. I am
specifically talking about
mounting subwoofer enclosures, they generally just don’t
get mounted to the vehicle.
Can you imagine getting into an accident and havening a 75-pound
box fly through your car? Recently several people have been killed
because of this unnecessary tragedy, it really is serious. My advice,
bolt your bumps down…
If you follow these tips, you too can reap the rewards of Great
Bass.
Bryan Schmitt |
