horn break in
A while back, we looked at how some car audio speakers and subwoofers perform after being damaged. We analyzed how the Thiele/Small parameters of a sample subwoofer changed after hours of playback. What we didn't adequately clarify in that article was whether or not speakers had to be tuned before use.
Parts of a speaker or subwoofer
Let's start by understanding the basic parts of a speaker or subwoofer. We'll use this great cutaway view of a Hertz Mille subwoofer to see what's moving and see what changes when the driver "breaks in".
horn break in
I've marked the subwoofer parts that don't move in light blue and those that move a lot in yellow. Components that connect moving parts to fixed parts are marked with green arrows. The moving parts are stationary relative to each other. Therefore, they should not bend or deform when moving back and forth. As for the part where the compliance of the speaker may change with use, all we need to care about is the spider and the surround sound.
The role of the surround is primarily to keep the top of the cone centered in the basket and provide a flexible joint to prevent any sound produced in front of the speaker cone from mixing with sound coming from behind. In most car audio speakers, the surround is made of foam or rubber. However, some high-efficiency PA-type speakers use pleated fabric for surround sound. Generally speaking, surrounds don't usually change compliance over the life of the speaker unless the foam surround dries out and fails.
Now let's look at the spider. This is the main component that controls the motion of the cone. Put it unequivocally: a spider is a spring. The Oxford English Dictionary defines a spring as "an elastic device, usually a helical coil of metal, which can be depressed or pulled, but which returns to its original shape when released, and which serves primarily to exert constant tension or to absorb movement." If you (carefully) push on the cone or pass current through the voice coil, the cone will move. When you remove the force on the cone assembly, the cone returns to its rest position.
The spider used in speakers is different from the helical metal coil springs in pens or car suspensions because it is made of a woven material such as cotton, cotton and polyester, rubber, acrylic, or aramid fibers (Kevlar or Nomex) . Spiders made of woven materials (everything except rubber) have been impregnated with resin to increase their stiffness. Spiders are designed with linear or progressive scrolling to change their compliance at different offset levels. Also, the thickness of the thread used in the weave and the amount of resin added can change the compliance significantly.
The diameter of the spider relative to the diameter of the voice coil former's central opening also affects its resistance to movement and the force required to bring the cone assembly back to its rest position. From a transducer design perspective, the bracket is the key component that determines the Thiele/Small parameters of the transducer and how it works. A stiff spider may produce a very high Q design, ringing and oscillating around the resonant frequency, while a compliant spider may have a lower Qms, allowing the cone to gracefully return to rest, resulting in a nice, tight sound .
As the cone moves forward or backward, the space between the rollers in the stand elongates. If the cloth has a lot of resin mixed in, you might even hear a slight cracking or crinkling sound the first time you manually push the cone. This stretching of the braided material and resin reduces the spider's compliance. This change will cause a change in the Thiele/Small parameter and possibly a change in the frequency response of the drive.
horn break in
Spiders are available in a variety of materials and sizes to suit different applications.
Break the speaker and car engine
There is general agreement in the auto industry that new car and truck engines need to be lightly broken in to last a long time. It is said that the piston's compression and oil control rings need to fix themselves or embed themselves into the cylinder wall. Presumably, the break-in process increases compression. Some flat tappet camshafts do require a proper run-in process at higher engine speeds to ensure the components are properly lubricated.
Crucial to engine life is making sure the engine is fully warmed up before you put your foot on the floor. If the oil isn't hot enough to flow properly through every part of the engine, metal-to-metal contact can cause premature wear. At the very least, cold oil won't flow as easily, and the engine will waste more energy trying to run. Still, always follow the manufacturer's recommendations for break-in to maintain your warranty.
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It never hurts to break in a new car engine lightly. Always follow the manufacturer's instructions in the owner's manual.
Now, back to our speakers. Depending on the materials used to build the spider, it may take some time for it to reach its final operating state. If it was stiff when new, it may soften or loosen after playing at high volume for a while. If you're gentle and don't play the speakers loud, nothing will stretch, will it? When I'm ready to check the speakers, I apply a low frequency signal to the drivers to practice the suspension. I usually leave the speakers playing for at least 5 hours, sometimes even 10 hours. Smaller drives may only see 3 or 4 watts to provide enough excursion. A subwoofer may require 25 watts to run the cone.
What are the best speakers for my new car audio?
If you've bought new speakers or subwoofers for your car or truck, the first thing you need to know is that you can enjoy them right away. If they do need some break-in time, let it happen. Turn up the volume and stretch and get into top operating shape. The only way to know if a speaker's design has changed (from a consumer perspective) is to measure its parameters when it's brand new, and then again after hours of playing. If they change, then you're good to go. If they don't, you can still continue. See a pattern?
It is assumed that the audio system you are installing will be calibrated using a digital signal processor. In this case, changing the suspension compliance of the speakers or subwoofer may affect the frequency response of the system. Install the system, calibrate it, and enjoy it. Schedule an appointment to check the calibration after a few months of playing to see if adjustments are needed.
horn break in
If your audio system includes DSP or EQ, you should consider checking the calibration after 100 hours of playback.
