Subwoofer Comparison Test: Round 1 (cont.)

Guidelines for Testing

Objective section

Enclosure size (15 points)
Given the fact that we are discussing car audio, space is a large factor to consider. There are not many people who can honestly give an entire trunk of their vehicle for an enclosure. For that reason, it is only right that we award points for size. However, what those points mean to consumers with different kinds of applications is up to them to determine. The point system in this test is applied to the enclosure volume that is recommended by the manufacturer. This same enclosure will be made use of throughout the majority of tests performed within this article. Given this, a maximum of 15 points may be awarded to each woofer per the enclosure volume recommended.

In Lab SPL (5 points)
SPL is a term that most audio consumers are familiar with these days. The simple fact that a loud system draws attention generates interest in SPL. For those of you unfamiliar with the initials, this stands for Sound Pressure Level. This is the measurement of sound volume (acoustical energy). The in-lab measurements for SPL are actually LEAP Software generated outputs. These outputs are derived using the Theile/Small measurements as shown in the Data Comparison Chart. Even though they are not actual test numbers, we have come to respect the accuracy of the LEAP system. Top honors will take home five points and leave second a point behind.

In Car SPL (10 points)
Subwoofers can perform noticeably different in a vehicle than they do in the lab. As well, the same sub will also vary performance from one type of vehicle to the next. Our test vehicle was a Toyota TacomaExtra Cab, so keep that in mind. In-car SPL measurements were taken at a one meter distance using a sign sweep starting at 1 kHz and falling to 10 Hz. The peak output is then taken from the data and referred to as the max SPL. Based on this peak amplitude, a maximum of ten points is given.

Xmax (length x 2)
Xmax is one of the most misconceived measurements in the industry. Yet, this is one of the easiest of the measurements to calculate. Xmax is simply how much the voice coil overhangs, top or bottom (these are normally the same), the top-plate of the motor structure when the speaker is at rest. This number by itself has no real useful meaning and really cannot be used compare woofers. In many cases, subwoofers with shorter Xmax can produce higher max SPL and have a greater dynamic range. We'll just chalk this up to bonus points by doubling the length in inches.

Subjective section

Tonal balance (10 points)
Take into consideration that a typical subwoofer has an expected useable frequency response of 20 Hz to 120 Hz. Obviously, this is what one is to expect from this subwoofer. But how smooth will the response be over the entire bandwidth? This is how we apply tonal balance. Tonal balance points are based on how flat the response of the subwoofer is conveyed in the enclosure over the a given frequency range of 20 Hz to 120Hz. Maximum of 10 pts.

Low frequency extension (10 points)
Most subwoofers can play down into the 10 to 30 Hz range, but how well, or should I say "loud" can they play it? Up to ten points can be awarded in this category in respect to how much earth shaking, low frequencies these long excursion subs can muster up.

Clarity at high volume (10 points)
Given moderate volumes, distortion can rise quickly with subwoofers. And with every subwoofer comes a new threshold for audible distortion. A maximum of ten points is achievable for clarity at high volumes. Each of the subs in this test was analyzed at the same volume level to note its abilities and will be subjectively awarded points based on the performance.

Clarity at low volume (10 points)
Distortion may be a factor when you listen for clarity at low levels, and low frequency response may suffer for various design reasons. Different design philosophies can vary the low volume frequency response in terms of attack and output levels. Upwards of ten points may be awarded subjectively to those whose clarity maintained a respectable balance as well as accurate dynamics.

Impact (10 points)
Attack and decay. These are the primary aspects of impact; the time it takes for sound to build up or die down. This subjective measurement is based on quickness of both attack and decay in due respect to the recording. However, this subjective test may not be of interest to you if large, boomy bass is what you desire. Take it for what it is, but the results will be based on the quickness and accuracy on a ten-point scale.

Overall sound quality (50 points)
Take all of the other subjective measurements, place them in a blender for five minutes. Voila! Sound quality! Okay, maybe it's not that easy, but the essentials are all there. For overall sound quality, all aspects of performance come to play as one. The result could be better or far worse than any one of the other subjective measurements. Given the importance of this listening test, it carries a lofty 50 points.