Can we combine the advantages of line- and point-source technology into one speaker?

Can we combine the advantages of line- and point-source technology into one speaker?

I'm now inspired by vintage ADS L2030 speakers. They're described as being designed to combine the benefits of both line- and point-source technology in a single speaker. They use four midrange drivers and have a midrange toggle switch for switching between line-source and point-source operation.

According to the brochure, the main bigger midrange is more efficient than the remaining three smaller midranges. In point-source mode, only the main bigger midrange sings, whereas, in line-source mode, the four midranges sing concurrently. The line-source mode is advertised as "weighted line-source", which is also promoted as combining the advantages of both line-source and point-source technologies.

However, these speakers were produced in the early 1980s. I have never heard the sound of these speakers, though.

I'm curious whether this idea should be revived in modern design. I'd like to hear other people's thoughts.
 
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Another combination of arrays acting as (sort of) a point source would be bbutterfield's fractal array.

I've linked to it quite often because I simply love the ingenuity of it. The behavior is controlled in both the horizontal as well as the vertical plane.

vertical_polar-png.715844

horizontal_polar-png.715845
 
Many years ago, Bottlehead made a kit line array of 8 small bass-midranges (iwth a tweeter above 3-5kHz), called the "Straight Eight." We tried out a modification that cut out the lower ones progressively. It was different; I think it was a modest improvement, but these things are too dependent on room acoustics to generalize. It also had varying impedance, from 16 ohms in the bass to 4 ohms at the crossover - somewhat of a problem for SET amps!

There is a crossover circuit that gives constant impedance while transitioning gradually from 4 to 1 driver, but there is a 6dB bass boost. That might serve as a baffle-step corrector for a narrow column (?)
 
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Comb filtering happens when the wavelengths from multiple drivers are longer than the driver spacing. However, this is a multi-way speaker with each ring using steep crossovers and digital delay to compensate for travel distance. As a result, the comb filtering in the vertical direction shouldn't be much different than a properly designed multi-way speaker using single drivers. It's not clear to me how the radiation pattern will look in the horizontal direction, particularly near the crossover points. However, this curved array approach has been used before in the McIntosh XR-19 and was shown to have "excellent imaging".
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A ring of drivers like that is most likely intended to give consistent horizontal results. In such a case there would be no shading or delay added as they would be intended to radiate horizontally as though from a point in the middle of the ring.
 
Pretty much could skip the line source mode.

Otherwise be interesting to see a modern take on that speaker.
Using just one Dome mid.
Allows a much smaller tweeter to be used.

As with many domes, rather smooth and easy to sum.
They touch distortion at high levels.

Only reason likely to care about a " line" source at that point.
Is running 2x dome mids for higher SPL.

Far as trying to weasel in more domes at that point be silly.
Wide baffle is pretty gorgeous though for people that appreciate them

To really get the massive line look.
Probably use 2x 12" woofers then toss in 2x 12" passive radiators
Basically make the woofers look like a line.
But just a passive radiator reflex
 
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It is a fact that "point source" and "line source" are two different things.
The idea of trying to combine them seems a little odd and pointless.
EG:
If point source was 'acid', and line source was 'alkaline', then combining them would give you SALT.
My combination for great HiFi stereo and excellent cinema-surround would be >
Line source for Left & Right, and point source for Centre & Surround.
 
PS.
My main Left & Right speakers are custom built 'poor man's' di-polar line source 2 meters high with bass
coming from their dedicated enclosures. 12 inch front firing LF. & 15 inch rear subs. 6 X 5.5 inch 'line' mids.
3 X front firing tweeters & 1 X rear firing. All connected by a totally custom cross-over network.
I call them - "The Twin Towers".
They are very big, broad & open sound, able to play at real concert levels without distortion.
 
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Sounded BAD!!!

Used the midWoofer in these, i had to mod them to clean up a lot of the ringing.

https://www.t-linespeakers.org/FALL/toobz/index.html

dave
Well, yes, that driver had all the vices and only some of the virtues of metal cones, particularly after the revision of the cone curve to straight sides. IIRC, they kept the same part number :^( In production, we coated the cones with a butyl rubber compound, and added damping tape to the frames, both of which helped a little.

But my point was just that the line array was shaded in the experiment, and it made a positive change.

(The shaded crossover was never put into production, nor was an experimental lower crossover frequency - the product became unproducible and was discontinued.)