Quote:
Originally Posted by Calanctus
Halcyon, when you say "uniformly directive speakers, that have a very steady, but slightly falling power response" are you referring to how the response declines off-axis?
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Yes, I'm referring to speakers that attenuate all frequencies evenly when you move off-axis.
When you measure the power response curve of such a speaker, it is essentially flat.
This means that driver/baffle/cross-over directivity characteristics have all been taken care of.
Considering that more than 60% of the sound you hear in non-near field listening is reverbated sound from off-axis output of the loudspeaker, this directivity is a key issue to accurate sound reproduction (both tonality and imaging).
Most good loudspeakers do measure well dead on-axis or even 15/30 degress off-axis, but fall apart after that. This is clearly audible in their sound.
However, I also wrote "slightly falling power response graph", because I've heard loudspeakers that have an almost ruler flat power response graph and they are too bright to listen to (imho).
Why? Because most recording are mixed with not very linear loudspeakers, the response of which falls of rapidly at higher frequencies.
Experienced loudspeaker designers (Gradient, Dynaudio, Amphion, Genelec, etc.) have noticed that due to this, it's better to have a linear, but slowly declining power response curve towards the higher frequencies. Measurements prove this as speakers from aforementioned designers have a uniformly directive dispersion pattern, but the power response graph is slightly attenuating towards higher frequencies (while still remaning as linear as possible).
This way tonality/imaging is portrayed accurately, but current recordings are rendered more naturally as well (i.e. not too bright).
I don't much like omni-directional speakers myself. I like cardioid/hypercardioid dispersion patterns (ala Amphion) better.
Omni-directionals are more of the "let's bring the players into this room by mixing the original acoustic space cues with the space cues of the listening room" school of thought.
This leads to a diffused and inaccurate soundstage. Very pleasing, if the omni-directional speaker is uniformly directive as well (this retains tonal accuracy), but not good in terms of imaging (re: Mirage omni-polars).
However, as in any audio reproduction there are many ways to perceptual happiness and the one that is technically correct isn't always the one that pleases everyone. So Caveat Emptor.
regards,
halcyon