Early Reflections in Home Theaters: A Different Perspective

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admin

Audioholics Robot
Staff member
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

Davemcc

Audioholic Spartan
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.
 
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westcott

Audioholic General
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

mike c

Audioholic Warlord
Audioholics needs an article about "How to setup acoustic treatments in your dedicated HT" :p
 
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westcott

Audioholic General
Audioholics needs an article about "How to setup acoustic treatments in your dedicated HT" :p
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.
 
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Scott R. Foster

Junior Audioholic
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.
 
S

syntheticwave

Enthusiast
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.
... I am sure, the early reflections the core of each acoustic. Its correct spatial distribution is one of the most important cues for the spatial impression. The main difference regarding the genuine event is the reduction of its spatial distribution upon a few single channels in the conventionally surround procedures. Moreover the surround formats including no information regarding the elevation level of the mirror sources, which causing the early reflections in the recording room from all directions, mostly outside the horizontal level.

A new approach enables to synthesize its correct distribution by the reproduction side. That’s very expensive, but the reproduction by far more accurate as the conventionally methods. I am work on the topic since some years; the principle is described by easily understandable animations on my website. Unfortunately the procedure practically realized until today only by horizontal loudspeaker rows around the listener, wherefore the reproduction remains two dimensional still.

Hence, the website www.syntheticwave.de is only a description; the system isn’t purchasable until today. But the Problem description seems my important for all home cinema users. It becomes possible to enlarging the playback room virtually by the loudspeaker wall.


Kind regards Helmut
 
gene

gene

Audioholics Master Chief
Administrator
In our recently added YouTube video we discuss room acoustics and the importance of balancing the sound in your room to get the best possible performance from your speakers. Over treating can make your listening space sound too dead and take the life out of the room. Too little treatment can result in a room whose sound is dominated by reflections resulting in a very blurred, echoey and fatiguing environment. In a home theater room you should still be able to carry on a normal conversation comfortably but still have a room that is dampened enough to allow the first arrival of sound to be much louder than the associated reflections. Using multiple subs will even out the bass and negate expensive and bulky bass traps and low end acoustical treatments that reduce system efficiency and often look unsightly. Watch our video to learn more on this topic and feel free to ask your questions below.

 
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