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.

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