Pan,
The bottom line is that in any space the acoustic field can be decomposed into a sum of modes, i.e. eigenfunctions of the Laplacian, i.e. solutions to the Helmoltz equation. In a bounded room, the eigenvalues (frequencies of the modes) are discrete. In an unbounded room or free space, the eigenvalues form a continuous spectrum. I'm not sure how one could argue against this.
The bottom line is that in any space the acoustic field can be decomposed into a sum of modes, i.e. eigenfunctions of the Laplacian, i.e. solutions to the Helmoltz equation. In a bounded room, the eigenvalues (frequencies of the modes) are discrete. In an unbounded room or free space, the eigenvalues form a continuous spectrum. I'm not sure how one could argue against this.
LineArray said:
I feel like someone is pulling my leg but here we go..
A room mode (which is a standing wave) is a resonance at a frequency determined by the distance between the surfaces that makes the room.
Without surfaces > no room > no room modes > no standing waves > no resonances = the idea of infinitely number of modes equals nonsense!
/Peter
Rybaudio said:
In the free field there is only the output from the transducer and the box or baffle surrounding it. There are no room modes, no standing waves, no eigentones in the free field.
/Peter
We're more or less arguing what the definition of mode is. I'm using the scientific definition and you are equating mode with resonance due to reflection. These concepts coincide in a room, but not in free space. I'm not going to try to convince you to adopt my usage, but I will say this:
- it is the scientific standard
- it is the right viewpoint from which to analyze Mavo's original apparent problem
Also, this has been discussed on here before... in one of the "big" threads a half year ago or so.
- it is the scientific standard
- it is the right viewpoint from which to analyze Mavo's original apparent problem
Also, this has been discussed on here before... in one of the "big" threads a half year ago or so.
Furthermore i think, even though the freespace discussion
may be interesing, the thread was started to discuss
placement of subwofers in a listening room, which has
typically very low modal density in the bass range.
This low modal density is audible as "room resonances"
affecting the bass response ...
What can be done (besides using Headphones) ?
may be interesing, the thread was started to discuss
placement of subwofers in a listening room, which has
typically very low modal density in the bass range.
This low modal density is audible as "room resonances"
affecting the bass response ...
What can be done (besides using Headphones) ?
Multiple subs*
Directional subs/speakers
Line sources*
Passive/active bass absorbers
EQ
DSP
*Are variation on the same theme, both being a step away from the point source.
/Peter
Directional subs/speakers
Line sources*
Passive/active bass absorbers
EQ
DSP
*Are variation on the same theme, both being a step away from the point source.
/Peter
I consider this to be a problem with the listening environment.
So I would tame the room as much as possible, using as just stated ( bass absorbers and traps ).
I had tried multiple split subs in the past and abandon it for close coupled centered subs.
With separation, there was noticeable cancellation in the subs passband from destructive interference.
For some listening areas this might be a good thing, if there was a predominate room resonance at that frequency.
Basically what I see as a problem with this approach, the tendency to apply this to all listening areas. The AES analysis did not seem ( to me ) to be representative of the average listening area, more like a dedicated Home Theater room. Practically speaking I don't know anyone who has a room like this with dedicated seating confined to the small grid they used. SAF factors and realistic living circumstances would rule out this out for most I'm guessing.
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