Radiation Patterns

[Borat]

Ok we have some people who think a perfect speakers should be a point source monopole, and that dipole is inherently inferior.

We have some who think a dipole is superior to monopole.

And we have some who think the devil is in the details. That issues like lobing are what kills a speaker.

So where does everybody stand ? I am including a poll. The poll asks which is the WORST PROBLEM for speaker radiation pattern.

[Drew Eckhardt]

Your brain derives timbre from both direct sound and reflections. Things which cause the reflected spectrum to have sufficiently broad peaks and dips change the timbre and don't sound natural. While lobing (as on a planar "dipole" or MTM) is one such defect an acoustically large woofer crossing to an acoustically small tweeter causes similar problems.

More and less uniform have a bigger effect than intentional monopole approximation/intentional dipole approximation/conventional speaker/horn or waveguide.

Different directivity changes how the speakers interact with the room (image width/placement is less affected when speakers have less output towards nearby objects).

[Borat]

Originally Posted by Drew Eckhardt

Your brain derives timbre from both direct sound and reflections. Things which cause the reflected spectrum to have sufficiently broad peaks and dips change the timbre and don't sound natural.

that just made me realize that it isn't just the speaker that must have an even power response - the room must have an even ABSORPTION SPECTRUM too. no ?

when we talk about rooms we usually talk about room gain, eigenfrequency etc. but we never seem to talk about absorption spectrum ?

i mean if you plaster 1" thick foam everywhere in your room you will mostly kill everything up top without much effect below 300 hz or so. so could you in fact be making your room sound WORSE by applying room treatment ?

by absorption spectrum i mean room frequency response above eigenfrequency or whatever it is called.

[bolserst]

Originally Posted by Borat

Ok we have some people who think a perfect speakers should be a point source monopole, and that dipole is inherently inferior.

We have some who think a dipole is superior to monopole.

And we have some who think the devil is in the details. That issues like lobing are what kills a speaker.

So where does everybody stand ? I am including a poll. The poll asks which is the WORST PROBLEM for speaker radiation pattern.

Borat,

Floyd Toole has summarized a life time of object(aka double blind) tests to learn what listeners(trained and untrained, young, old, audiophiles, non-audiophiles, musicians, etc) like concerning frequency response and radiation patterns of loudspeakers, and reflective qualities of rooms, first reflections, total room power, etc.

This book would be a good starting point for your research on this topic.

Amazon.com: Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms (9780240520094): Floyd Toole: Books

[bolserst]

Originally Posted by bolserst

Borat,

Floyd Toole has summarized a life time of object(aka double blind) tests to learn what listeners(trained and untrained, young, old, audiophiles, non-audiophiles, musicians, etc) like concerning frequency response and radiation patterns of loudspeakers, and reflective qualities of rooms, first reflections, total room power, etc.

This book would be a good starting point for your research on this topic.

Amazon.com: Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms (9780240520094): Floyd Toole: Books

Btw, almost forgot to mention, the tests DO include ESLs full range & hybrid in the mix with dynamic speakers.
Also shown are, comparisons of blind vs sighted tests for the same group of test speakers.

[Drew Eckhardt]

Originally Posted by bolserst

Btw, almost forgot to mention, the tests DO include ESLs full range & hybrid in the mix with dynamic speakers.
Also shown are, comparisons of blind vs sighted tests for the same group of test speakers.

I've seen the comparisons through Chapter 9 and noted that in the Quad ESL/2-way/3-way comparison I didn't notice anything done to account for the differences in bass response (I could have been distracted switching between text and illustrations but will look again) in the form of low-frequency cut-off, total power from the speaker, or room gain for the pressure sources.

[Borat]

Books

do i have to ?

[Key]

Originally Posted by Borat

that just made me realize that it isn't just the speaker that must have an even power response - the room must have an even ABSORPTION SPECTRUM too. no ?

when we talk about rooms we usually talk about room gain, eigenfrequency etc. but we never seem to talk about absorption spectrum ?

i mean if you plaster 1" thick foam everywhere in your room you will mostly kill everything up top without much effect below 300 hz or so. so could you in fact be making your room sound WORSE by applying room treatment ?

This is what I basically think happens. And I think it might be the cause of a lot of the CDs coming out really bright - but I am giving a lot of engineers the benefit of the doubt with that one.

It might be an over simplification of how we perceive things but I do think it gets overlooked that when you unevenly absorb reflections you effectively turn down the volume on the region you absorbed and not much else. I've heard it talked about here and there but for the most part speaker makers just stick to speakers and skip over the room part. Linkwitz is one of the first I heard explain it in a simple way like this about how turning down the reflection can be perceptually the same as turning down the volume. It's somewhere in this lecture

Linkwitz AESUK_lecture_0711.mp3 - 24.58MB

Here is a blurb about speakers from ATC although the article itself plays the fence and skips over absorption.

"4. Dispersion and Directivity
The relationship between direct and reverberant sound is
very important in high performance loudspeakers. It is clear that
not only must the on-axis magnitude response be accurate and
linear but also that the behavior off-axis must be both broad and
even with frequency exhibiting no abrupt dips in amplitude. The
aim should be to achieve a horizontal dispersion of +/-80 deg.
With a -6dB @ 10KHz and a vertical dispersion of at least
+/-10 deg. To ensure that in a well behaved room with a good
RT vs frequency characteristic, The reverberant sound will be
consistent with the direct sound in the listening area"

[Joachim Gerhard]

it depends a lot how far you sit from the speaker

[Joachim Gerhard]

and how big your room is