OC705 vs. OC703

4065 Views 4 Replies 4 Participants Last post by bpape, Dec 10, 2008

BoomieMCT

Discussion Starter · Aug 6, 2007

I often hear that OC705 is better for building bass traps. However every time I see a comparison of absorption characteristics OC703 seems to absorb more @ 125 Hz.

Here is an example, ATS comparo

What am I missing here?

Save

1 - 5 of 5 Posts

bpape

· #2 · Aug 7, 2007

125Hz performance doesn't map directly to making a good bass trap. Unfortunately, you can't really do standardized tests at 40-50Hz.

The other thing that nobody addresses is thickness. If you're limited to 4", then 705 is a better choice. If you can go 6", then 703 will work just as well and will cost you less.

Bryan

Save

Ethan Winer

· #3 · Aug 7, 2007

BoomieMCT said:
What am I missing here?

See this:

www.ethanwiner.com/density.html

--Ethan

Save

grn1969c10

· #4 · Dec 10, 2008

Is it OK to resurrect a really old thread? There may be updated information available somewhere, but I'm chasing rabbit trails with the search feature right now.

http://www.ethanwiner.com/density.html

Ethan touts reducing the Q as a positive benefit. This spreads an effect across a wider frequency range. Wouldn't increasing the Q (giving a peak narrower bandwidth with steeper slope instead) make it easier to accurately target with a narrower parametric EQ filter?

Save

bpape

· #5 · Dec 10, 2008

If you want to do that, you have to start adding a membrane, calculating the specific resistance and flexibility of the membrane and a specific thickness of the 703/705, etc.

As an example:

Coefficients at 125, 250, 400, 1k, 2k, and 4k for various thicknesses and densities.

1"
703 FSK
0.18 0.75 0.58 0.72 0.62 0.35

705 FSK
0.27 0.66 0.33 0.66 0.51 0.41

2"
703 FSK
0.63 0.56 0.95 0.79 0.60 0.35

705 FSK
0.60 0.50 0.63 0.82 0.45 0.34

3"
703 FSK
0.84 0.88 0.86 0.71 0.52 0.26

705 FSK
0.66 0.46 0.47 0.40 0.52 0.31

Standard R-19 wall insulation ( around 1lb/cu ft density), paper faced. Paper facing the room
0.94 1.33 1.02 0.71 0.56 0.39

Some of those will actually show humps below the standardized 125hz band.

Bryan

See less See more

Save

1 - 5 of 5 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month