Sell Subwoofers Without the Specs

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“One thump fits all” doesn’t work in autosound, so how do you help customers select the right woofers without knowing the Thiel / Small parameters? Buzzwords, general guidelines, and common sense.
The fun part of selling and installing mobile electronics when the “crank it up” days first started was all based around subwoofers and amplifiers. While there’s many of both products out there on the market now, subwoofers still cause much confusion among salespeople because the range of choices is so broad. How do you select and sell the right one(s)?
Before there’s even a concern about brand, the key factors need to be outlined. Although the Theil /Small parameters are very important for the overall enclosure design and construction, they aren’t the first things sales associates need to dabble with. Determining the key factors starts with finding out more from your customer. Some questions to ask are:
What amplifier will be used to run the woofer(s)?
The amp is important for several reasons. First, how powerful is it in comparison to the motor size (that’s the magnet and voice coil assembly) of the subwoofer? Second, how much heatsink and cooling ability does the amp have? Playing a single subwoofer is a different “workload” than, say 3 or 4 subwoofers, even if the load of both scenarios is the same. More voice coils is more work for the amplifier to start and stop.
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Tip #1: Keep It at a Safe Level
Regardless of how stable a manufacturer claims an amplifier to be in regard to the “load” it’s connected to, keeping things playing around 4 ohm loads on Class AB amplifiers (which covers most of them) will keep them running cooler and more reliably than trying to extract the maximum 2 or 1 ohm power. In those lower loads, they quickly lose the ability to start and stop the speaker effectively, they draw more current, and they run considerably hotter in the process.
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How much space is the customer willing to allot for a box?
The space concern will, often times, be a big influence on choosing a subwoofer. Not every subwoofer works in just any enclosure. If one is better suited in a vented enclosure, it’s less than optimal as a sealed box woofer. There’s always a trade-off with designing the right subwoofer system, so start with the right type of woofer and there’ll be fewer unexpected surprises.
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Tip #2: Ohm Loads Made Simple
The “load” of a speaker or set of speakers relates to how hard the amplifier has to work to push the speakers to make sound with a precise degree of control. Think of it this way: if the music being played has a number of beats in rapid succession, the amplifier needs to be able to push the woofer out, then reset it before the next beat. If the load is too much for the amp, it loses some of its control, and the woofer does not efficiently reset due to the extra heat and vibration caused by the amp’s distortion.
Each speaker is rated with a load. Most automotive speakers have 4-ohm loads, compared to home speakers that primarily have 8-ohm loads. By combining speakers in one of two wiring configurations, you can change the load placed on an amplifier.
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Tip #3: Sealed vs. Vented Boxes
Small sealed enclosures for a single subwoofer are a great way to get a reasonable amount of accurate bass. If you give it at least 100 watts, the results are impressive. If the customer likes a little more bass, or has less power to use, then a vented enclosure might be a better choice. The trade-off is usually that the vented enclosure will be a little larger than a small sealed enclosure. The benefit is lower bass and higher output from less power compared to a small sealed enclosure.
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What’s the next size speaker in the frequency chain?
Avoid a gross mismatch of the blend between the subwoofer and the midbass or midrange speaker. It’s tough to get a good solid “bass up front” illusion from two 18” subs in a vented enclosure on 1000 watts when the next speaker in the system is a 4” speaker in the dash on 25 watts. The idea is to have a gradual transition as the frequencies pass from one speaker to another. Without the balance, listening fatigue sets in much sooner.
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Tip #4: “Blend” in Add-on Sales
In order to get an effective blend of frequency from a sound system, there needs to be a midrange or midbass driver of adequate size up front to handle the transition from the subwoofer. You can get some pretty impressive results from 6.5” or even 5.25” drivers if they’re crossed over actively. Damping materials (Dynamat, Scosche Accumat, etc.) in a door location can make a big difference in blending technique.
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What is the spending limit?
The total cost of adding a subwoofer needs to be considered as well. It’s not really the subwoofers themselves, but driving them with the appropriate amount of power (and all those associated costs), constructing the proper enclosure, and adding the right kind of low-pass filtering are all additional costs that can easily double or triple the price. Many times the cost of vehicle specific subwoofers such as the JL Audio Stealthboxes, MTX Thunderforms, Rockford Fosgate VSS enclosures, Q-Logic vehicle specific enclosures, and others seem like good value for money after considering all the hidden costs in custom built composite enclosures.
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Tip #5: Build It Piece by Piece
If you want to keep things cost effective on systems that are “under construction”, it’s a great plan to start with a 4-channel amplifier (preferably with an internal active crossover), good front speakers and a single sub. Run the fronts off of channels 1 and 2, channels 3 & 4 can be bridged to that single sub. If the customer has rear speakers at all, use the deck power as “fill”. When it comes time to move up to another sub, the customer can run the channels 1 & 2 to the new sub and purchase another amp to compliment their front speakers, or even another 4-channel amplifier to run something in the rear. The key is to keep adding adequate power as speakers (especially subwoofers) are added and NOT to expect that you can always just add another subwoofer onto the same amplifier without also expecting it to work harder (draw more current) and run hotter.
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The reality is that with moderate power, say 150 watts per woofer on all but the monster “Built for SPL” subwoofers, one can get pretty impressive results. What’s important is that the woofer is positioned in the vehicle in the right spot and that it’s in a properly suited enclosure.
MECP has a great book out for salespeople called the Mobile Product Specialist Study Guide and there’s a lot of great non-product specific information on subwoofers and all the advantages & disadvantages of nearly every type of enclosure that you can imagine. It’s written very “laymen” so it’s easy to understand. It’s available by calling MECP at (703) 907-7689.
The main thing to understand with subwoofers is that getting great bass in most cars is really pretty easy. There are a few fundamentals to consider as you design what will accomplish the goal, but after that, it’s hours and hours of satisfied listening.

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