Speed & Sound: Plugged In – High-End subwoofers

Text by Dave MacKinnon (www.osmlabs.com)

Photos by the Manufacturers

A few issues back, we took our first look at subwoofers. This is a key subject in the area of car audio, since most systems, even some of the best high-end factory systems, often lack the ability to reproduce the bottom octave of the audio spectrum accurately. In this installment of Plugged-In, we’ll look at what you get for your money when you buy a high-end subwoofer.

Depending on your point of reference, there are two definitions of a high-end subwoofer. For musical purists, it would be a subwoofer that reproduces music more accurately with better low frequency extension. For those of you who are more enthusiastic, a high-end subwoofer would be one that could handle massive amounts of power and produce near-lethal amounts of output. We’ll look at both.

On the SQ front, when looking for a subwoofer, you want something that sounds realistic. A true SQ subwoofer is likely going to be used in a medium-sized sealed enclosure, and should be able to easily reproduce frequencies down to 10Hz with excellent linearity. An SQ subwoofer should also be able to play to beyond 100Hz – this typically means that they have excellent dynamic abilities – making your bass fast and accurate.

SQ subwoofers are all about linearity – that is to say, they reproduce adjacent frequencies with similar output levels. You don’t want a big bump in the frequency response. Typically, SQ subwoofers also offer reasonable power handling capabilities, usually around 400-1,000 Watts, mostly because you need significant amounts of power to drive these speakers to realistic output levels at very low frequencies. If the drivers are frail, they would fail.

You can’t really spot an SQ driver based on any specific set of parameters, since none of the conventionally accepted criteria describes how the speaker performs when being fed large signals. Test equipment from companies like Klippel GMBH and Smith & Larson are capable of analyzing the behavior of these drivers in motion. This lets engineers work to ensure the suspension operates in a linear fashion, as does the magnetic motor structure.

How do you pick an SQ woofer? The best way, of course, is to audition it in your car on your audio system. You want to listen for dynamics and control – bass should hit hard and be solid. It should also stop as fast as it starts. You don’t want a kick drum to linger on after the hammer has hit the skin – just a solid thunk. Where many companies fall short on their subwoofers is in the area of subsonics. It is my opinion that bass response should extend to 10Hz – did I mention that? Only about half of the great sounding, musical woofers I have reviewed over the past ten years were also capable of playing very low. You should be able to feel the deep fundamental vibration of a pipe organ note.

The flip side of the high-end subwoofer camp are the SPL subs. Having attended two or three dB Drag Racing World Final events over the years, I can attest to the incredible punishment these speakers have to withstand. This is the car audio equivalent of Top Fuel drag racing. Imagine more than 10,000W being fed to a single subwoofer and vehicles with 10, 20, 60 or more subwoofers in them hitting SPL levels over 181dB. The excursion requirements are incredible, as are the power handling requirements. Subwoofers designed to take this kind of punishment are incredible beasts, and often weigh in at well over 100 lbs each.

Unlike SQ woofers, it’s a little easier to spot an SPL ‘in the wild.’ They typically have massive motor structures (magnets), huge surrounds that allow for massive (3-inch plus) excursions and can be very expensive.

Because these subwoofers need to withstand massive stresses, they often require multiple spiders to be used to keep the voice coil centred. Very large diameter voice coil windings, made of large conductor wire, are also used to handle the huge amounts of power that are fed to these drivers. The cone assemblies need to be very strong as well, as they have to withstand huge g-forces.

In either an SQ or an SPL application, the design and construction of the enclosure is equally critical to the subwoofer you choose. Last month, we got some help from Matthew Gordash at Defined Designs and we went through the construction of what would be deemed a good-quality consumer-level subwoofer enclosure. When you decide that you want to take your bass to the next level – so should the design of the enclosure. Thicker materials, more exotic materials and much more bracing are just some of the criteria. You don’t want to waste any energy vibrating the panels of your enclosure when it could be used to make music. These vibrating panels add noise to the system. Some call it colouration; whatever you choose to call it, it’s bad. If you are looking to build an SQ enclosure, then 1-inch MDF and extensive bracing are my recommendation. When it comes to SPL enclosures, that topic alone is diverse enough to fill an entire magazine. You are best to research and consult with some of the many veterans in the sport of SPL competition for what works best for your subwoofers and the vehicle of your choice.

When it comes to high-end subwoofers, just like with high-end cars or good quality tools, they all do the same basic job, but the high-quality models do it better, with more accuracy, detail and control. The joy of moving from a regular consumer-level subwoofer to a true high-end SQ subwoofer and hearing all sorts of new and subtle sounds is fantastic. Likewise, if you are after every tenth of a decibel and you have lots of power, a high-end SPL subwoofer can be the key to winning the next round and taking home the trophy.

Related Posts

1. 
   Speed & Sound: Plugged In – Subwoofer Enclosure Build
2. 
   Speed & Sound: Plugged In – Keep Your Eyes on the Road
3. 
   Speed and Sound: Feature Car – The Hustle
4. 
   Speed and Sound: Feature Car – What the 9ff?
5. 
   Speed & Sound: Performance – Battle of the Buldge