[dayneger]

I've been wondering what factors influence the size of the sweet spot, particularly in reference to speaker design.

Many speakers sound great, but unfortunately in a zone barely the size of a golf ball. . .

What design features yield a larger sweet spot for dedicated listening and a more enjoyable experience when one is living around the speakers as well?

Thanks!  Dayne

[nathanm]

It depends on how big your definition of "sweet" is. Actually, that's not entirely a joke come to think of it!

Although the technical gurus here will be able to tell you better I personally think it has to do with room interaction as well as the radiation pattern of the air coming off the drivers.  Similar to microphone pickup patterns I'd say.  Perhaps horns are like hypercardiods and cones like cardiods or semi-omnidirectional?  The speaker would have to have better off-axis frequency response than one which only sounds great in one point in space.  The high frequencies are the ones that seem to reinforce our perception of sound placement, so if the treble isn't as strong when you're outsite the direct blast zone then it might not sound as good.  That's just my layman's interpretation, take it as you will.  And as I said, it depends on what kind of sound you enjoy hearing.  If you are very concerned with left-right imaging then you may prefer to stay in the center.  If the song moves you regardless, then anywhere in the room might be the "sweet spot".

[PJ]

DImensions of the drivers and the frequency they are asked to reproduce.

As the wavelength of the soundwave approaches the driver dimensions, the sound becomes increasingly directional.

For instance, for a 7" (17.5cm) woofer, the woofer starts to "beam" around 1950Hz.

[John Casler]

Hi Dayne,

I think most people don't really know what the sweet spot is.  It is the singular convergent area of two or more signals to make a sonic image.

It might be helpful to think of each speaker as a projection gun, but instead of video, it projects sound.  

Your head is the screen and each gun(speaker) has a different signal that if converged "exactly" will produce an "exact" sonic image.  If the convergence is "off" the image begins to blur just like it would if we were converging video on your head and you moved from one side to the other.

The sad news is that any system that "seems" to offer this in anything larger than a couple inch leeway is only offering an acceptable blurred image and not a reproduction of the real thing.

Anyone who thinks their speaker system will provide a "two channel" music image larger than this is mistaken and probably has never heard a true "sonic holographic soundstage".  It is just impossible to do so

While we can use placement and toe in to help offer those who are out of the sweetspot some localization, the sweetspot itself is only big enough for one head, unless one head is below the other.

My girlfriend and I used to listen this way, where she sat in front of me and was short enough that we both enjoyed the sweet spot in different vertical planes.

Hope that make sense,

Regards,
 
John Casler
 
VMPS LA CA USA
SUMMIT Audio Video
[email protected]
http://my.register.com/summitaudiovideo.com/index.html

[dayneger]

Hello John,

Your point about the technical definition of sweet spot is well-taken, and it makes sense that the most ideal spot is exactly at this convergence.

What interests me in particular is that I don't always have my head in that tiny window.  It's nice to sit beside my girlfriend, for example, and still be able to have an enjoyable if rather blurred image.  I also like listening to my system when I'm at different parts of the room, with friends, when I'm folding laundry, or whatever.  I don't expect perfection for casual listening contexts, but the larger the projected image, the better the chances are of being able to interpret the image.

I've heard systems where the listening pleasure drops off dramatically as soon as you're out of the zone, whereas others seem more forgiving.

People have written that some of the Norh speakers are forgiving like this.  Why are these better, and others more directional?  What could you do to maximize this effect without screwing up the image for dedicated listening?

PJ's interesting note makes me wonder if a 3 or 4-way would be necessary to avoid this "beaming"?

Dayne

[John Casler]

What could you do to maximize this effect without screwing up the image for dedicated listening?

In my opinion "nothing"

To distribute sound throughout the listening area you either need multiple speakers or "reflected sound".  

The early Bose 901s could turn your wall (as long as it was rather lively) into a huge soundscape.  It wasn't accurate or real, but very musical.  Most Dipolar designs (Def Tech, Maggies, MLs) also captialize off of this reflected sonic energy to create beautiful results, but if it comes from the wall, it isn't close to real.

So the two things are mutually exclusive and one trades off to the other.  If you have a "wide dispersion" you may have a large beautiful and musical sound, but you lose the ability to produce a sonic image "true" to the original.  

Since my system is both HT and Audio, when I am listening for basically musical backround, I turn on all 7.2 speakers (actually 11.2 but who is counting) and get the most enjoyable and musical backround.

When I am seriously listening, it is two speakers only and I am "exactly" in the "sugar".

All the best,

John

[Night Wolf]

I think it also has to do with how wide a spekaer is, I noticed spekaers that are more narrow tend to have a greater sweet spot. take my L100's for example, a very small sweet spot, but once you find it, and sit in it, it's so sweet

[EProvenzano]

Stereo image and off-axis response are two very different things and both these issues are often not clearly defined.
I can't offer a complete definition but here are some of my thoughts.
I agree that there is only 1 true sweet spot where stereo image is best heard (likely at the convergence point exactly between 2 properly aligned speakers).
I do not agree that every speaker has the same off axis response in terms of details, clairity and musicality. The tonality of a speaker's presentation is very unique as one takes various off axis measurements. Some speakers lose much of their response at only a few degrees off axis while others can remain flat at 60 degrees off axis. Sure you will have all kinds of phase distortion if you try and listen to speakers this far off center, and the image will be nonexistent, but the tonality and over all character of the speaker will be conserved. There are always compromises.
Just my 2 cents.
BR,
EP

[PJ]

Hi Dayne,

My girlfriend and I used to listen this way, where she sat in front of me and was short enough that we both enjoyed the sweet spot in different vertical planes.

Ahh..  

[EProvenzano]

     

[Night Wolf]

lol, good one

[John Casler]

Did I say"vertical" planes?

I am currently writing the KAMA SUTRA of Listening, including sections on Eargasms and Aural  

As well, I have a chapter on "does Pinna size matter"?

You guys  

John