An ideal speaker's off-axis response

[bachatero]

Does the "ideal" speaker have its volume reach a limit of 0 outside of its designed beamspread? Or does the "ideal" speaker emit sound omnidirectionally? I'd like to know because it seems like this is all over the map. Some speakers are pretty loud even behind them, while others might have huge, thick enclosures that block sound from all directions except the front. And, then there's the omnidirectional ones which are just the same everywhere.

 

[kemmler3D]

There's actually no solid consensus on this, even among top experts like Toole. Anything from narrow beams to full omnidirectional seems to have good arguments for it, depending on who you ask and what your priorities are.

As a rule of thumb narrow dispersion can take your room out of the equation to an extent, (for better or worse) but it limits where you can sit. It gets you more of a "they are here" type of imaging, supposedly.

Wide dispersion can give you more options of where to sit, and produces more of a "you are there" type of image.

Since stereo is ultimately an illusion and artificial, etc. - it seems impossible to say that one approach is objectively better.

There is a way out of this, which is to say "I want to listen the way they listened in the studio" - which would imply monitors and (maybe) relatively narrow dispersion. But even monitors aren't all the same in this regard.

So I think it's really down to preference.

 

[Deleted member 21219]

The biggest (and most obvious) problem associated with loudspeakers is dealing with the room acoustics. Not only do different designers have differing opinions about how to do that, but rooms are all different sizes and shapes, with differing degrees of reflectivity, so the problem is even more complex and more difficult to deal with.

I was in Japan in 1975, and visited a research center for audio. As part of a demonstration, I, among others, was led into a dark room that had one single chair in evidence. I sat down, and the most amazingly real jazz trio played in front of me, club environs and all. The piece played out, and the lights came up, and I was in an anechoic chamber. In front of me were two medium-size speakers. They appeared to be 8" two-ways.

In discussions with the presenters, there were statements made that (at the time) surprised me. They said that 1) the recording didn't sound the same in a normal room. In fact, it didn't sound very good at all except in the chamber. 2) The speakers sounded hugely different outside the chamber, and 3) for this arrangement to work, head positioning was critical.

I was unable to really appreciate what I had just heard, and went about my way, searching for speakers that sounded good in my normal living environs. But I never forgot that the best sound that I had ever heard was in a controlled environment that removed the room from consideration.

Jim

 

[DVDdoug]

while others might have huge, thick enclosures that block sound from all directions except the front.

I'm not an expert...

Assuming a traditional speaker with the drivers on the front and facing forward, it's largely dependent on the relationship between driver size and wavelength. Horns & waveguides also have an effect, and again it's related to wavelength.

At bass frequencies (long wavelengths) the soundwaves tend to spread-out in all directions.

Most speakers are ridged enough that the sound from cabinet vibrations is insignificant. And midranges & tweeters are usually closed-back or a cabinet-in-a-cabinet.

Speaking of Floyd Tool, I bought his book. I'm in the middle of a different book right now but I read the 1st chapter, or so, and it's very good and it looks like it's going to be an easy read... Not nearly as much math as I expected.

 

[dfuller]

But I never forgot that the best sound that I had ever heard was in a controlled environment that removed the room from consideration

Yep - this is why the best studio control rooms out there do their absolute best to (and I know this is going to get blowback) remove themselves from the equation. It's the exact same thing, it removes the room as a confounding variable to the music.

 

[Penelinfi]

I always thought wide dispersion is "they are here" - musicians in your room = your room acoustics.
And narrow is "you are there". You hear more reverb from the recording. Your room is removed.

 

[mcdn]

The ideal is that it’s even, not that it has a specific pattern.

So for example a good omnidirectional speaker is omnidirectional at all frequencies

Or a good cardioid speaker is cardioid down to below the Schroeder frequency of the room (~300Hz typically)

Of course most speakers are neither of those, they are monopoles with a narrowing horizontal response directivity with frequency, and a terrible vertical response mess around the crossover. They still sound great though! For these speakers the PIR curve on the CEA2034 charts is a good proxy for quality.

 

[kemmler3D]

I always thought wide dispersion is "they are here" - musicians in your room = your room acoustics.
And narrow is "you are there". You hear more reverb from the recording. Your room is removed.

I might have gotten it backwards, I wrote that pretty late at night...

 

[rdenney]

In real rooms, the design target linked to the preference testing done by Toole and others is wide directivity, where off-axis frequency response is as flat as on axis response, though perhaps tilted down as the frequency increases. That seems to be the most versatile in real rooms.

Rick “gets clear imaging even with wide-directivity Revels” Denney

 

[fpitas]

though perhaps tilted down as the frequency increases

Which is a hotly debated target. About all that everyone agrees on is it should be smooth to avoid apparent resonances.