Philosophy behind sound deadening?

[Trendkill 10+ year member]

So then if you aren't using a sealed pod, then you are essentially using a "ported" pod. Since port tuning is so essential to sub boxes, would tuning still be important for the pod?

 

[audioholic 5,000+ posts]

So then if you aren't using a sealed pod, then you are essentially using a "ported" pod. Since port tuning is so essential to sub boxes, would tuning still be important for the pod?

Using an aperiodic membrane, and using a port, are different things. A port utilizes the backwaves to help reinforce the front waves, increasing output. AP setups use a membrane of material that air can pass thru, but not without resistance. You build a small enclosure that is sealed except for the hole you will cover with the membrane material. This allows the speaker to push air through the material, but with a resistance, thereby acting as if the enclosure is larger than it really is. These rear waves escpae through the membrane and them must be sealed off from the front waves to avoid cancellation issues (much like infinite baffle in doors).
Ports are to increase output (and tailor the response), AP membranes are to allow for a small enclosure while retaining the response and low-end output found in larger enclosed setups.

 

[Trendkill 10+ year member]

ah so is that somewhat similar to polyfill?

 

[audioholic 5,000+ posts]

ah so is that somewhat similar to polyfill?

Vaguely similar, but not really. Polyfill will increase perceived enclosure size slightly (like a few percent), changing your aperiodic mat thickness/density can emulate virtually any sealed enclsoure size up to and beyond the speaker's IB range.

Here's a good article on putting an AP enclosure in a door pod: http://www.elitecaraudio.com/home/html/print.php?sid=18