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Axiom05
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Stereophile's Room Measurements

I have been reading some of the past speaker reviews that contain JA's in-room measurements of the speakers in the reviewer's listening room. In particular, I have noticed that in Wes Philips' room there is consistently a suck-out around 35-40Hz. It varies in depth depending on the specific speaker, but always appears to be present. For example, it is especially deep in the review of the Avalon Indra speaker. I am wondering if there is a known mechanism for the presense of this "hole" at this particular frequency in his room? I am interested because my listening room exhibits the exact same behavior. This is a problem that I have been trying to solve for 15+ years. No changes in speaker placement or listenting position have any effect whatsoever on this lack of sound pressure at these frequencies. The problem seems to be consistent throughout the entire room, not just at one or two locations. Hoping to learn from the experience of others.

John Atkinson
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Room Measurements Anomaly

Axiom05 wrote:

I have been reading some of the past speaker reviews that contain JA's in-room measurements of the speakers in the reviewer's listening room. In particular, I have noticed that in Wes Philips' room there is consistently a suck-out around 35-40Hz. It varies in depth depending on the specific speaker, but always appears to be present. For example, it is especially deep in the review of the Avalon Indra speaker. I am wondering if there is a known mechanism for the presense of this "hole" at this particular frequency in his room?

This is due to a node or anti-resonance in this region at the listening position in Wes's room. It does disappear in front of or behind the listening position.

Quote:
I am interested because my listening room exhibits the exact same behavior. This is a problem that I have been trying to solve for 15+ years. No changes in speaker placement or listening position have any effect whatsoever on this lack of sound pressure at these frequencies. The problem seems to be consistent throughout the entire room, not just at one or two locations.

This a little strange, as this kind of measured behavior is generally very position-dependent. Is your room rectangular, or does it have recesses and alcoves, or openings into other rooms?

John Atkinson

Editor, Stereophile

Axiom05
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Room Measurements
John Atkinson wrote:

This a little strange, as this kind of measured behavior is generally very position-dependent. Is your room rectangular, or does it have recesses and alcoves, or openings into other rooms? 

Yes, strange and very frustrating. BTW, thank you for your response! The room is 21 ft long, 16.3 ft wide with a nine foot ceiling. The speakers fire down the long dimension of the room. There are two sets of doors leading from the room, one to a library/office (back of room) and one to the foyer (side of room). Both sets of doors are kept shut while listening. Closing the doors improves bass response by 1-2 dB. I suspect the problem is a large bay window alcove (appx. 9 ft wide and 3.5 ft deep) at the front of the room behind the speakers. I am able to measure high SPL's within the bay window area for the frequencies in question, e.g., 40Hz, but not within the main room itself. Not sure what this means or what I can do about it.

Josh Hill
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I don't know why this is true

I don't know why this is true everywhere in the room, but I put the dimensions in a room mode calculator and you do have some problematic modes in that region:

34.7 hz 

43.8% 

32'7", 16'3", 8'2"

(0,1,0 Axial)

Start iso, End iso

39.0 hz 

11% 

28'12", 14'6", 7'3"

(2,0,0 Axial)

 

39.8 hz 

2% 

28'5", 14'2", 7'1"

(1,1,0 Tangential)

Caveat, the actual modes tend to vary from the predicted ones.

I could be wrong, but I'm guessing it isn't the bay window. They do focus sound but at these frequencies the window is << a wavelength.

Calculator is at:

http://www.bobgolds.com/Mode/RoomModes.htm

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