What is the point of point source?

Don't confuse point source with a narrow soundstage. A perfect point source would give you a great soundstage and cause the speakers to 'disappear' in theory.

The larger the area of a radiator the more directional it is. This is why tweeters are made as small as possible. An infinitely small sound source would radiate equally in all directions and have perfect dispersion; this is why small speakers can "disappear" more easily than large ones. The smaller the drivers and the closer they are together the more they act as an ideal "point source". On the other hand the smaller the speaker the less air it moves so all speakers are a compromise. Low frequencies are essentially non directional so woofers can be quite large but the farther the drivers in the speaker are apart the farther away you have to be from them for the sound to properly integrate from the various drivers.

Perhaps it might be better to consider a point source as the starting point rather than as a tiny narrrow beam? Though somewhat unusual, perhaps the Quad ESL's might be a good example of what I'm trying to express.

I think one way to look at what people conceptually like about point source speakers is that microphones used to record music act in general like point receivers. There are various pickup patterns and multi-miking is common but you don't record a sound event with treble, mid, and bass microphones arranged top to bottom.

So the general idea with a 'point source' speaker being that it acts like a microphone in reverse. Whether this sounds good to you in your room is up to you.

WHat Nik said + speakers that approximate a point source (coaxial or OHM CLS drivers, or even smaller two way designs with more closely mounted drivers for example) tend to have advantages in general in regards to phase coherence at typical listening distances. For small or even modest sized rooms in most peoples homes, this can be very advantageous in regards to the music being delivered smoothly. Having the sound emitted from approximately the same location at the same time also often results paradoxically in a bigger soundstage along with more accurate imaging in that your ears are able to triangulate location of specific recorded sounds within the stereo soundfield more accurately. Its like an image being more in rather than out of focus enables your eyes to exactly determine the location of details better.

If you listen from farther away, speakers tend to approximate a point source more so you get a lot of the same advantages. Line arrays can also work very well in larger venues listening from a distance.

A point source speaker implies a perfectly uniform spherical dispersion. No instruments have such output. No microphones can record it, either.

Stan, above, started with the idea of the size of a radiator being related to its directivity but didn't finish the thought. I wonder if a radiator beams more as the wavelength approaches the size of the driver.....

I also wonder how various linear designs work into this. A ribbon tweeter is a point, but stretched up/down for a distance.

I like the way Mapman was headed with this.....as a practical solution for speakers....a point source, which may never exist as a practical driver.

Maybe someone will come up with a solution using that new carbon material....Graphene?

In a concert hall you generally do not sit very close to the group, and the sound wave is closer to a plane than a point source!

don,

i think live is different because instruments have actual location. with stereo sound reproduction, that is not the case. spatial cues captured in the recording process enable your ears to triangulate location. speakers that emulate a point sorurce better are advantaged to deliver these accurately. this is one of the reasons i am a big fan of the ohm acoustics cls walsh driver. with simple two mike recordings that emulate the listening topology of your ears, they are capable of eerie lifelike imaging.

>I wonder if a radiator beams more as the wavelength approaches the size of the driver.....<

That's exactly what happens. When the diaphragm is small compared to the wavelength that's being reproduced, it's omnidirectional. As the wavelength decreases, waves from one part of the diaphragm go out of phase with waves from other parts and start to cancel, making the diaphragm increasingly directional.

That's why woofers, which are small compared to the wavelength, are omnidirectional, while tweeters tend to beam.

>I also wonder how various linear designs work into this. A ribbon tweeter is a point, but stretched up/down for a distance.<

One is called a point source, the other a line source, and it's been said that they're the only correct ways to design a loudspeaker.. The point source is omnidirectional, and the sound falls off as the square of the distance. An infinitely long line source OTOH radiates in a cylinder, and the sound falls off linearly with distance, rather than following the inverse square law. Of course, you can't have an infinitely long ribbon tweeter any more than you can have an infinitely small point source driver. But the floor and ceiling reflections of a line source actually make a line source behave much as if it were infinitely long -- imagine mirrors on the floor and ceiling, the line source would seem to stretch out above and below to infinity. If this weren't the case, line source speakers would act as omnis at low frequencies, but instead they maintain much of their vertical directivity.