|
Speaker Asylum General speaker questions for audio and home theater. |
|
|
|
Speaker Asylum General speaker questions for audio and home theater. |
|
In Reply to: Bass mode & node integration. What if a wall is missing? posted by Quiet Earth on May 6, 2007 at 22:26:20:
just moved.I have 2 archway entrances to my room. There's a 4' or so wide corridor on the other side of one archway with a wall on the far side of the corridor. I get some bass mode contribution from normal room width because the whole wall isn't missing, and some from the room width + corridor width because there's a parrallel surface there also. Neither mode will be as strong as if there was an unbroken wall at either width, but there is a contribution from both. Ditto for the other archway which opens up into a breakfast nook that extends through to the kitchen with a wall there, quite a distance away.
The best way of looking at what is happening is to say that what you get is a combination of:
- weakening one of the room modes because of reduced opposing wall areas;
- gaining another weaker mode because of the wall somewhere outside the opening;
- losing the 'cabin gain' that you would get in a closed room at frequencies below the lowest room mode;
- since the room can't be pressurised to anywhere near the same degree, other room modes will also probably be weakened somewhat;
- depending on the size and other factors related to the space outside the room, that area may also act as a Helmholtz resonator and provide some absorption;
- there will also be some energy loss at all frequencies because not all of the sound energy exiting through the opening will be reflected back into the room to the same degree as it would if the opening wasn't there.
Another way of looking at it would be to regard the situation as one of a much larger room with a number of internal floor to ceiling reflective surfaces that break the space up into some smaller areas, one of which is your listening area.
The weakening of one room mode and gaining of another weak mode may help to smooth rthe area's bass response somewhat, or the added weak mode may reinforce an existing room mode. That all depends on dimensions.
Corners will still give you some support for woofers or subs, and they're still the most effective place for siting bass traps though the effect of both will be reduced in comparison to a closed room.
As an unrelated aside, you also don't get rid of the room mode if you angle two opposite walls slightly so they aren't parrallel. What you do is to spread the mode over a wider frequency range and weaken it's maximum level.
Overall the end result may be beneficial or detrimental depending on the spaces involved. It's a much more complex situation than a closed room but the same principles apply. You just get a much more complex situation to model and make it much harder to predict by doing basic calculations. A computer model should be able to handle it but I don't know of any model that's designed to handle complex spaces for our purposes. If there was one and it was available for the Mac, I think I would have bought it and given it the several days or weeks it would need to calculate the response of my listening area which is L shaped, has one corner truncated at 45 degrees, plus the 2 open archways I mentioned. Given the open plan nature of a large part of the house, my 'larger space' would probably have to be regarded as the whole house. Not an easy set of calculations.
David Aiken
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- But it's not missing, … - David Aiken 00:28:12 05/07/07 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
