Room Acoustics Forum by Rives Audio Welcome! Need support, you got it. Or share you ideas and experiences.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Room Acoustics Forum by Rives Audio ]

---

[ Alert Moderator ]

---

"… 4 ft wide absorption immediately behind the listening position which opens out into a biggish room behind…"

Posted by David Aiken (A) on February 13, 2011 at 23:04:07

In Reply to: RE: Some quick thoughts on reflection… posted by Mark UK on February 13, 2011 at 14:36:59:

It doesn't work that way.

Sound will certainly exit the room through the opening and some will come back through it, after reflection around the space on the other side of the opening. What you have, though, is a coupled space and the results of that are unpredictable. The sound that re-enters the room through the opening is going to have some of the acoustic "signature" of the other space.

There are some plusses to be had. For a start you not only weaken the basic front/back axial mode for your room but you gain another mode based on the length of the distance between your front wall and the wall opposite it in the other space. The modal response of a room smoothes out as the number of modes per octave increases and gaining another mode, especially a lower one than your room would otherwise have, results in the "modal density" increasing faster than it would if you didn't have the opening which is beneficial, as is weakening one of the room's natural strong modes.

On the other hand I've heard of coupling spaces causing suckouts and simply causing bass response to start rolling off at around 100 Hz in one case. If the "sound" of the space behind is particularly different in character from the "sound" of your room—say if one space has a relatively normal or even "warm" character and the other sounds "hard" or "bright", the difference in tonality of the sound re-entering your room from behind might be disturbing.

I don't know any way of predicting whether the coupled space will work for good or bad. I've got 2 openings in my room, but my room is L-shaped, the right wall is the wall with the bend in it, and one of those openings is in each of the two "right" walls. One is into a hallway and the other into a large open plan area that the hallway enters so I'd hate to try and figure out what's going on in my room but it doesn't seem to create any major problems for me. On the other hand, a former dealer (now retired) who I know had a showroom with coupled spaces and he was never satisfied with the bass response of speakers in that room. Measurements showed it simply started rolling off from 100 Hz or so on down.

Basically all I think you can do is try but if there's a big tonal shift going on behind you with a difference in character of the sound coming from the rear sides of the room and that from the opening behind you, you may want to try either using absorption rather than diffusion behind you so that the sound coming from the coupled space dominates and weakens the difference in character, or place some sort of absorbing panels as a screen across the area behind you in order to weaken the sound re-entering the room, weakening the difference in the other way.

If you want to actually get genuine absorption including at bass frequencies then what you need is an opening to outside the house, to open space, so the sound exits and doesn't return.


David Aiken

This post is made possible by the generous support of people like you and our sponsors:

Atma-Sphere Music Systems, Inc.

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---