Tech Article Title Author Date
How to Fix Booming or Muddy Bass John Witherspoon 2000

Many A6 owners have complained about "booming" or "muddy" base from the Bose subwoofers installed in A6s with Audi's premium sound system. If you count yourself among the dissatisfied, here's a quick fix you can try (at your own risk, of course) that may well solve your problem...

Open the compartment where your subwoofer lives just inside the trunk at the right rear corner of the car. Feel around the rear-facing side of the subwoofer housing and locate the 2 inch hole. Then take a 6-inch strip of tape (1.5 inch wide electrical tape will work very well) and affix the center of the strip so that it covers between 50% and 75% of the hole. Be sure the tape is well-secured to the rim of the hole. Press the ends of the piece of tape to the subwoofer cabinet. Your system should now sound a lot less muddy while still providing adequate bass response.

Why does this fix work? The answer lies in how Bose (and other manufacturers) make "ported" subwoofers and speakers (such as the Bose Acoustimass systems for the home). In a ported design like Bose uses, the subwoofer speakers which create the bass sound rely heavily on the lack of back pressure as they vibrate back and forth (like pistons) to create non-directional bass sound.

If back pressure is introduced, the subwoofer speaker cones (which you can see under the spider web grilles on the left-facing side of the subwoofer housing) cannot move back and forth quite as easily and therefore cannot vibrate quite so much during and immediately after a bass signal is sent to them. Blocking the port creates some back pressure and causes the cones to calm down a bit.

If you want to experiment before you decide on the final amount of port coverage that suits you, sit in the driver's seat with the stereo on and the tone controls set to flat. Then have a helper slide an index card or a CD case up and down over the subwoofer port. When you're satisfied with the bass response, signal to your helper and have him note how much of the port is covered. Then apply tape similarly.

A last word of advice: listen to a variety of CDs and music styles before making your choice because an amount of subwoofer port coverage that vastly improves one CD may adversely affect how another CD sounds. You'll just have to decide what's the best happy medium for your taste.

Good luck and enjoy!

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