# Secondary Reflection Points



## jackfish (Dec 27, 2006)

It is relatively easy to either calculate or mirror-eyeball first reflection points. I can't seem to find much on how to determine secondary reflection points. Or if I should even try in a 11.5' x 15.75' room? Any resources out there on this? Thanks.


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## bpape (Sep 14, 2006)

Easiest way is to use 2 people and a mirror for 1st points

Bryan


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## jackfish (Dec 27, 2006)

Bryan, yeah I got that, but what about secondary reflection points? Thanks.


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## bpape (Sep 14, 2006)

Wouldn't worry too much about them honestly if the rest of the room is at proper decay times. The rear of the room in a multi-channel setup is generally a little more lively to allow good development of the surround field.

Bryan


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## jackfish (Dec 27, 2006)

I have GIK 244s in the rear corners and two GIK 242s on the back wall. I think I'm pretty close with my treatments. I also have GIK 242s at the side wall first reflection points and will be adding one on the ceiling soon. There are two GIK TriTraps in the front corners and I will soon be stacking two more atop those. A single GIK 242 is on the middle of the front wall. Thanks for your products and help.


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## bpape (Sep 14, 2006)

Sounds pretty good. I might suggest using 244's on the rear wall to reach deeper in helping nulls off the back. Maybe move the 242's that are there to behind the front speakers to address potential boundary issues.

Bryan


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## jackfish (Dec 27, 2006)

Eventually the speakers will be Magneplanar MMGs which might benefit from some hard surface behind them. When I get them I will play around with treatment placement as there are mixed opinions on how to address the back wave in Maggies, diffusion or not. I have six 242s, three at the first reflection point (2-sidewall, 1-ceiling) and currently two on the back wall and one in the center of the front wall. So are you suggesting replacing the two 242s on the back wall with 244s and putting all three 242s on the front wall?


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## bpape (Sep 14, 2006)

Yes. That's what I was suggesting. The bass waves that are problematic off the rear wall are too deep for the 242's to handle effectively. The 244's will reach considerably deeper. 

On the front wall, 242's will work well behind Maggies or you can use diffusion if you prefer to scatter rather than absorb the rear wave. In any case, the rear wave needs to be dealt with to address comb filtering. Diffusion will keep all of the energy and increase the soundstage width at the expense of the last iota of imaging specificity. The absorption will mitigate the problem with comb filtering but give pin point imaging at the expense of some of the rear wave energy.

Just 2 different ways to address the issue.

Bryan


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## jackfish (Dec 27, 2006)

What about using a single GIK Monster Bass Trap in the middle of the back wall instead of two GIK 244s, similar to what is shown in the GIK Room Kits?


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## bpape (Sep 14, 2006)

That's always a tradeoff. The monster will reach deeper, but, the waves are pretty large. The 4'x4' surface area of 2 panels will work better. I'd stick with 2 244's, or 2 Monsters if budget allows.

Bryan


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## jackfish (Dec 27, 2006)

Yeah, I can go with two GIK 244s, they are only $20 more than a single GIK Monster Bass Trap. Thank You.


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