Tip & How-To about Car Audio & Video

Box specs and airspace for 8 inch subwoofers

Regardless of your wattage rating on your sub woofer, sub woofers differ in only one way. You get an "Open Air" and a "Closed air" Sub woofer, That being said, you'll have to check on your magnet which one you have, to make the boxes for that particular sub woofer. If it is an "Open air" Sub woofer, you should see a hole with "wire mesh" or "metal grid" in the center, at the back of the magnet. If it is a "Closed air", the magnet will be solid with no hole whatsoever.

If it is a "Open air" sub, your boxes should always be sealed with silicone sealant, and no ports are to be cut in your box.

Regarding the "Closed air" sub woofers, you should have 2 ports cot in the corners of the boxes just below your sub on the face of the box, and the port sizes should be around 50mm in diameter. Get yourself some 50mm PVC drain piping to use as ports. Firstlycut yourself a 100mm piece and insert flush with the front of the box. Test your sound. then try a 150mm piecs and test again. You should start with a 100mm long piece in the one box and add 50mm increments to "tune" the port up to 250mm, depending on the frequency of bass you require. Carry on testing the sound on each increment until you find the sound you want, Then silicone the port to the box for permanent fixing.

On a 15 inch Sub woofer ranging between 80Hz and 100Hz, the ample box size required should be a box of 9 inches high, x 9 inches wide, x 9 inches deep. Or 400mm high, x 400mm wide, x 400mm deep.
Enjoy!

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1 Answer

i got vauxhall astra 1.6 and planning to put 1800w bass sub woofer. Can I do that, does astra can handle that.


If it is clean power it can handle it. Bad power causes distortion and DC output. That is what kills the sub woofer. The going rate for quality / good wattage is a dollar per watt. If you are not spending that much, then it is bad power.

Nov 01, 2013 | Cars & Trucks

1 Answer

I need a wiring diagram from car stereo to 2 x 6 " x 9 " and a sub woofer please


You can connect the two 6x9 speakers to the two individual left and right outputs of the car stereo.
Connect each of the left and right channel with the correct polarity . Now the Sub-woofer requires an amplifier to be connected separately and so you need to use the car stereo to be linked to a sub woofer amp which powers the sub woofer.

Mar 26, 2011 | Car Audio & Video

1 Answer

i have a subwoofer in my truck. 2 speakers in a box with an amp. One of the subs blew to a song that just came on. the volume was high. Sounds distorted. Any way to fix?


Sounds like the voice coil of that woofer overheated and melted while it was turned up too far. Now that area rubs on the magnet or pole piece internally and makes noise.

No you generally can't fix that except for a few high end woofer brands that have field replaceable voice coils that you can buy. Most subwoofers physically bottom out and sounds really bad before experiencing thermal damage like that. Sounding bad is a warning sign that it's being overloaded.

Note that woofers have 2 different types of overload conditions that can cause damage.
1. Over excursion from deep bass that moves the woofer cone too far and damages the suspension. This is clearly audible. Proper box design and user knowledge will prevent this.

2. Thermal limit. This is the published power rating that the voice coil can absorb without damage. Things can melt or fail entirely if this is exceeded.

Either of those issues can cause the noise you are hearing. Without a more detailed description of what happened or how it sounds before, during and after this is much detail as I can provide. But.. move the woofer some by hand, do it evenly pushing straight down evenly on both sides, not too far, go about half way through it's normal movement. If it clearly rubs and makes noise internally then the voice coil is damaged or if has some debris stuck in there. Most woofer are not serviceable.

There are many other factors that affect the longevity of the woofer, such as
  • Ambient temperature too high
  • Limited air flow has inadequate woofer cooling
  • UV exposure can make the surround material brittle
  • Proper enclosure design is needed to acoustically and physically supports the woofer to prevent bottoming out, particularly at the system resonant frequency.
  • Amplifier distortion can kill speakers even when rated far below the woofers max wattage.


Nov 28, 2010 | Sony XS-AW200 Car Subwoofer

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