What are the effects of soffit systems on room acooutics?

[vanhanbr]

I noticed on a few sites that they use a soffit system claiming it helps acoustics. What exactly is the purpose of using such system? It seems like it is built with sound absorptio in mind. Is there anything special i need to know if I want to try building one on my own? <BR><BR>Two companies that use these sytems are:<BR><BR>http://www.asc-home-theater.com<BR>http://www.acousticinnovations.com<BR><BR>Thanks,<BR><BR>Brian Van Handel

[crazyoldfart]

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<DIV>I suggest you do a search on this site for the word "soffit". We have discussed them several times. </DIV><BR>
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<DIV>I will respond with the primary improvements soffits provide:</DIV><BR>
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<DIV>1. Elimination of the baffle step effect. </DIV><BR>
<DIV>2. Massive reduction in edge diffraction.</DIV><BR>
<DIV>3. Reduction in early reflections to the rear of the speaker. </DIV><BR>
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<DIV>A proper soffit requires the speaker baffle be completely flush with the wall on all four sides with complete elimination of the gap between the wall and the baffle (usually via foam in the gaps).</DIV><BR>
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<DIV>Also, in order to utilize soffits correctly, your speakers much have all the drivers and any vents (ports) on the front baffle. </DIV>

[crazyoldfart]

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<DIV>Here's a link to a thread where I diagramed the reflections of regular versus soffit mounted speakers:</DIV><BR>
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<DIV><A href="http://www.soundandvisionmag.com/idealbb/view.asp?topicID=28031&forumID=29&catID=1&search=1&searchstring=&sessionID={FD7BB7CA-BD1D-47FB-AF0E-119D392185FE">http://www.soundandvisionmag.com/idealbb/view.asp?topicID=28031&forumID=29&catID=1&search=1&searchstring=&sessionID={FD7BB7CA-BD1D-47FB-AF0E-119D392185FE</A>}</DIV><BR>
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Thanks COF, I forgot to check both the subject and body box when searching. The soffits I was looking at actually protruded from the walls and were hung at the top of the wall. It seemed to me that they were built more as a room treatment than as a place for mounting speakers, but I could be wrong. Would I be wrong in thinking that placing speakers high on the walls is less than ideal? I realize this is common practice for rear channel surround sound, but shouldnt the speakers be placed closer to the height of the listener? In this case they will be most likely sitting down, so wouldn't the ideal height is somewhere around 4ft from the ground? <BR>Thanks,<BR><BR>Brian

[crazyoldfart]

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<DIV>Height is not as important as most make it out to be. It is important to raise a non-tower speaker above the floor a bit so it can acoustically clear the coffee table and get the midrange away from the floor, and placing a speaker too close to the ceiling will cause nasty reflections off the ceiling, but otherwise, the ideal height is anywhere in the middle portion of the room height. </DIV><BR>
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<DIV>It is best to&nbsp;prevent the woofers from being in a location where the reflection from the floor is about the same distance as the reflection from the ceiling to reduce the negative affects of that nasty null. It is also a good idea to use absorption or diffusion materials on the direct reflection points on the floor and ceiling to reduce the negative affects of early reflections. </DIV><BR>
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<DIV>But I have heard great systems where the speakers were situated higher than the listeners' heads. In fact, in my old recording studio we found the best placement to be about two feet above the listener's head as it reduced the affects of reflections off the mixing console. I have also built a few mastering rooms where the best speaker placement turned out to be higher rather than lower. </DIV><BR>
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<DIV>As for soffits, if they are not several feet wide & tall (at least 3 to 4 feet), then they are purely cosmetic and actually may be seriously detrimental to the acoustics. The true acoustical purpose of a soffit is to eliminate all baffle step and edge diffraction issues. If the soffit is nothing more than a larger baffle for a speaker, then it only reduces those issues and may actually increase some of them. In that case they are for looks and, being a pragmatist, I discourage anything that is purely cosmetic and potentially detrimental to the sound. </DIV><BR>
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[crazyoldfart]

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<DIV>The "soffits" on the ASC web site are not for mounting speakers. They are bass traps with cavities behind them for running cabling. That is totally different than what I have been talking about. I have been discussing soffits for mounting speakers in. </DIV><BR>
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<DIV>Bass traps are always a good idea. I think the "soffits" ASC is selling are interesting, but they are not something I would consider for home theater use. They would be nice in a conference room at a business location since they are attractive and unobtrusive, but for home use, a properly installed panel trap or helm-holtz resonator is a better choice. </DIV>

[vanhanbr]

Thanks, I was pretty sure the soffits I was looking at were different. I guess not all soffits are the same. Bass traps are always best placed in corners correct? Does that include the corners on the ceiling (where the soffits are located) and the vertical corners in the room? Would only placing the basstraps in the top ceiling be an affective solution? It obviously looks better than tall bass traps in the corners of the room.

[crazyoldfart]

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<DIV>Bass traps can be effective in any corner in the room.</DIV><BR>
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