Early Reflections in Home Theaters: A Different Perspective

[admin]

Early reflections may or may not be major problems in home theaters. Addressing them through the use of heavy absorption should be pursued with caution. I believe the issue of early reflections and their relative merits (or lack thereof) in any home theater should never be ignored. This article opens a dialog on how to best deal with them and how they differ from large listening spaces.


Discuss "Early Reflections in Home Theaters: A Different Perspective" here. Read the article.

[Davemcc]

What a timely article. I just got finished building my acoustic panels and maunted them where I thought they might work best, acoustically and aesthetically. The result was awful. Movies and music sounded muted and distant, never mind that the bass response was awful, almost dangerous with a 30dB gain from 60hz down to 40hz. I played around with panel placement to try to achieve some positive results. Here's what I found:

Simply taking the large panels off the back walls and using them to straddle the corners of the front soundstage reduced the bass gain to no more than 12 hz and it opened up the sound to remove the muted, distant sound.

I tried taking down the side wall panel but found the sound more pleasing with it in place. I had it in and out of place a number of times to confirm, so I know I certainly prefer to have side wall absorption in place.

I ordered a OC 703 equivalent (according to the sales rep) Ottawa Fiber OFI-48. I'll use this to experiment with bass traps in the two front corners and play around a little more with panel placement. This must be where HT becomes a hobby.

[westcott]

I was reading some comments in another forum from a man who is getting his pHD in audio and his comments were somewhat similar in that he suggested that we ignore reverberation time in our small home theater calculations altogether. That overtreatment seems to be a growing concern when proper speaker placement practices are also used.

And as you mentioned Dr. Toole, it seems that Harman International and its subsidiaries may actually be designing their speakers with early reflections in mind and trying to offset their influences from the get go.

Other speaker designs like Klipsch have used controlled dispersion technology to also avoid early reflections and side panel placement in a tradional manner may be mute at shorter seating distances.

All very good perspectives that should give some people something to think about. In the end, it is what provides the flattest frequency response in your room and\or sounds good to you.

Keeping an open mind is the real key, IMO.

[mike c]

Audioholics needs an article about "How to setup acoustic treatments in your dedicated HT"

[westcott]

Originally Posted by mike c

Audioholics needs an article about "How to setup acoustic treatments in your dedicated HT"

I think if you dig into the Audioholics University section, you will find some relevant articles.

I think that you may be missing the gist of the article though. What we have been exposed to, as far as room treatments, was largely based on large room calculation scenarios. Since home theaters are not large when compared to public concert halls these original formulas were based on, we are now starting to question their validity of these calculation in the modern home theater application. This means we must rethink everything including acoustic treatments when addressing our own acoustic issues.

I hate to say it, but the only real reliable way to diagnose room acoustics is in room measurements with equipment capable of very high sampling rates. Not cheap or readily availble to the average sound designer, much less the audio enthusiast.

The only other real solution is to experiment with acoustic panels and place them according to what sounds best to you. You can try the tradional locations like corners and edges or primary reflection points, but as the article pointed out, we may be doing the right things for all the wrong reasons.

This article should be a real eye opener and I hope everyone who reads it walks away with a new found appreciation for the complexities of audio science.

[Scott R. Foster]

That's interesting stuff Jeff explores in his article... the most recent Toole paper has really got his gears turning I see... on a set of issues he has long warned us about [applying paradigms developed for opera houses to our spare bedroom ].

I would note however that Jeff's point is narrow in that he addresses the useful of early reflection control for speech intelligibility, and as such, properly focuses on calculations regarding the center channel. But there are other purposes beyond speech intelligibility and the center channel that can be beneficially served when you install early reflection control absorptive treatments... such as enhancing that clarity/depth of the stereo image... diminishing the likelihood the listener will be exposed to flutter echo... making the "sweet spot" larger... etcetera.

Still I think Jeff has an excellent point that absorptive treatment can easily be over done - and trying to apply irrational / inapplicable concepts like RT60 to small rooms is a practice that should stop.