Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Re: Q about DIY tube trap

Posted by Jon Risch (B) on October 28, 2001 at 20:39:10

In Reply to: Re: Q about DIY tube trap posted by FAT on October 28, 2001 at 11:34:14:

Just looking at specs in a book, or absorption coefficients in a manufacturer's chart do NOT tell the whole story.

Many such charts or data show absoprtion that EXCEEDS 1. This is, of course, patently impossible, but due to the methods used to measure such things, bogus numbers get generated. The one thing you seldom if EVER see is: what is the reflectance of the material? Here, the higher densities do not work as well at higher frequencies. Note that many charts end at 4 kHz or 8 kHz, and that actual HF reflectance does not tend to show up in the absorption coefficient numbers to any degree due to the way they are measured.

I specifically stated that this information stems from my own personal experiences and measurements. I have spent some significant amount of time measuring HF reflectance, and testing many different materials for reflectance.

Of course, most of the higher density materials can be "fixed" by adding a layer of 3/4 to 1" polyester hi-loft type batting.

Jon Risch

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