[aceinc]

While the speakers I an thinking about building are OB the questions are more about the line array issues. I couldn't find a "Line Array Circle."

I am contemplating building an OB line array with 8" "ribbon" (planar) speakers for the mid to high frequencies. The bezel (flange?) would cause the actual diaphragms to be about 1" apart.

In discussing this with both ChatGPT & Gemini, they contend the acoustic centers of the drivers will be so far apart as to cause lobing and comb filtering above 800 hz.

I think differently. Does anyone have experience with this type of build?

Does it behave as a line source (single driver) at all frequencies, or is there comb filtering above a certain frequency?

Also Iwas under the impression that tweeters in an array do not have the cumulative effect of increasing efficicency/sensitivity as the woofer do. AI disagrees with this, who is right?

[ThePriest]

As far as I know, the line array efficiency increase is the same for woofers/mids/tweeters.
What are your thoughts as to why not?

If I remember correctly (it is more than 10 years since I designed and built mine) the center-to-center distance of the drivers should be less than the wavelength of the lowest frequency that driver is intended to play, in order to avoid (or minimize) lobing.

/The Priest

[S Clark]

These are 8" electrostatic drivers on my GR-Research LS9 speakers.  Looks like the diaphrams are about 1.5" apart. 
It's one of the best of the type. 

Also, you state "In discussing this with both ChatGPT & Gemini, they contend the acoustic centers of the drivers will be so far apart as to cause lobing and comb filtering above 800 hz."   I think this should be below 800 hz.  Make your crossover higher than that.   The LS9 crossover point is at 900Hz, and the LS6 higher still. 

[FullRangeMan]

Eight Visaton B200 no cross over and nice bass.

[aceinc]

As far as I know, the line array efficiency increase is the same for woofers/mids/tweeters.
What are your thoughts as to why not?

If I remember correctly (it is more than 10 years since I designed and built mine) the center-to-center distance of the drivers should be less than the wavelength of the lowest frequency that driver is intended to play, in order to avoid (or minimize) lobing.

/The Priest

I believe I have had conversations via the forums with Danny Richie, and I remember him saying tweeters behave differently. I remember him saying an array of tweeters specifically ribbon/planar tweeters do not increase in sensitivity the way lower frequency drivers do. It is possible I misremember but I believe I pushed bac at the time and he defended his position vigorously.

[JohnR]

Search for the line array white paper by Jim Griffin. It was written a while ago but the truths in it don't change.

[jeffreybehr]

These are 8" electrostatic drivers on my GR-Research LS9 speakers.  Looks like the diaphrams are about 1.5" apart. 
It's one of the best of the type. 

...

"Electrostatic"?  Did you mean magnetic-planar?

[S Clark]

Yes!  Thanks for the correction. 

[Will P]

8in mid-tweeter planars with 1in space between them should be no problem as far as lobbing at the listening position is concerned.

As far as line array driver efficiency increase with the frequency increase - yes, the higher the frequency the tighter the group of drivers which would work in coherent matter to allow for 6dB increase of SPL output for doubling the number of drivers. 1/2 wave length difference is the maximum for each center-of-driver-to-listening position distance difference between the drivers for coherent summing of output.

With frequency increasing the group of coherent drivers gets smaller and smaller.

For non-coherent drivers - their output is summed 3dB/doubling the number of drivers (their power is summed). Even for non-coherent drivers for a particular frequency band there would be some summing but not the full 6dB/ doubling the number of drivers as seen in drivers with coherent output.



Here is a link to Don Keele's line array white papers.

Tons of useful information.


https://dbkeele.com/technical-papers-2/

https://dbkeele.com/constant-beamwidth-transducers/
.