I've seen photos of these speakers around the place and I always wondered, what's the effect of having two open baffle woofers arranged like this?
To my mind it seems like it will still perform the same as a single di-pole configuration, won't it? Do we get more sensitivity?
https://www.dagogo.com/legacy-audio-whisper-dsw-review-part-1-of-3-what-if/
To my mind it seems like it will still perform the same as a single di-pole configuration, won't it? Do we get more sensitivity?
https://www.dagogo.com/legacy-audio-whisper-dsw-review-part-1-of-3-what-if/
https://www.diyaudio.com/community/threads/multiple-stacked-dipole-bass.341691/post-5890479
They say they are are trying to control dispersion with that layout.
https://legacyaudio.com/backstage/perspective/project-whisper/
"The low frequency drivers operate in phase with each other and combine acoustically as a pair of figure- of-eights, one behind the other. The result: a compound null formed at the sides of the enclosure, which minimizes resonances and room reflections."
They say they are are trying to control dispersion with that layout.
https://legacyaudio.com/backstage/perspective/project-whisper/
"The low frequency drivers operate in phase with each other and combine acoustically as a pair of figure- of-eights, one behind the other. The result: a compound null formed at the sides of the enclosure, which minimizes resonances and room reflections."
prepared for some reading? 🙂
https://www.diyaudio.com/community/...m-open-baffleless-full-range-speakers.374043/
https://www.diyaudio.com/community/...m-open-baffleless-full-range-speakers.374043/
I see you have two woofers mounted face to face in an open configuration. Why? I mean not listening impressions but technically, what is the function of using two drivers rather than one? AFAIK there will be zero air velocity at the interface between the two divers because one moves forward while the other moves backwards (creating a side null), just the same as using one open driver?
If you really want to know, read the thread. It is not a "to the point" scientific work, but all information is there.
My geocities pages are long gone, but I recovered my old pages on the wayback engine and posted it on my pages again. (very old post)
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Erik, I can probably model it in AKABAK quicker than reading all that just to find a gem of technical information. It's the completely open arrangement that puzzles me. Obviously stacking di-poles like Linkwitz shows gives you more active surface area at the front and back so that makes sense to me.
Ok, I know what is in that thread, so curious what comes out of the simulation. Please simulate with different distances between the drivers.
It's called a "compound dipole". Siegfried Linkwitz has some info on it somewhere on his web site. I and others made measurements on drivers set up in this way about a year or so ago, and it was posted on this site. Use the search function.
In short, the compound dipole helps to reduce low frequency cancellation a bit, in a way similar to increasing the baffle size (which increases the front to back pathlength) but without using a baffle. If you CAN instead use a larger baffle, you will get more output if you just put the two drivers side by side in the baffle.
30second job in vituixcad with realtime adjustment: open diffraction tool, make dipole response say 15" ideal driver so 38cm x 38cm baffle and 850cm2 Sd, or what ever you want. Check feed driver and click Export. Then in crossover window connect source to driver with wire, duplicate the driver and connect that as well, series or parallel doesnt matter to check directivity. Adjust Z coordinate and watch graphs change.
Polar maps are at 100Hz.
There is certainly an increase in sensitivity or overall output with the double driver setup (drivers connected to source in parallel). I guess this is because we kind of have twice the magnetic power where the drivers are close enough to couple. There also seems to be a narrower side null as the spacing increases. At a certain point in the higher frequency response the two drivers no longer couple and we see some response cancellation (polar looks messy here).
There is certainly an increase in sensitivity or overall output with the double driver setup (drivers connected to source in parallel). I guess this is because we kind of have twice the magnetic power where the drivers are close enough to couple. There also seems to be a narrower side null as the spacing increases. At a certain point in the higher frequency response the two drivers no longer couple and we see some response cancellation (polar looks messy here).
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Celestion System 6000 was another that used this configuration. I haven't measured one, so can't say in practice whether the description below is completely accurate.
https://www.stereophile.com/floorloudspeakers/892/index.html
"Within the strangely shaped bass section are two 12" bass units, mounted "front-to-front" and spaced by an open air gap. There is no box or baffle as such, just the reinforced panels on which the drivers are actually mounted. The woofers are long-throw, low-resonance units with high stiffness, flared, pulp-composition diaphragms.
With the cones moving in the same acoustic phase, the 6000 bass section constitutes a bidirectional push-pull radiating element, or dipole, little different from an open panel loudspeaker. (The pair act as a virtual drive-unit located at a point midway between them.) A dipole has an output concentrated in the fore and aft directions, while the output at the sides falls to zero. This directional property is exploited in aerials to improve the signal recovery, and adding a second element makes the array performance still more directional, increasing the sensitivity or power gain in the desired axial directions. The second bass-driver, placed close behind the first in the 6000, constitutes just such a second element, resulting in a simple array equivalent to a two-element FM aerial. In addition, the excursion required for a given low-frequency sound level will be reduced, with the workload shared between two drivers."
https://www.stereophile.com/floorloudspeakers/892/index.html
"Within the strangely shaped bass section are two 12" bass units, mounted "front-to-front" and spaced by an open air gap. There is no box or baffle as such, just the reinforced panels on which the drivers are actually mounted. The woofers are long-throw, low-resonance units with high stiffness, flared, pulp-composition diaphragms.
With the cones moving in the same acoustic phase, the 6000 bass section constitutes a bidirectional push-pull radiating element, or dipole, little different from an open panel loudspeaker. (The pair act as a virtual drive-unit located at a point midway between them.) A dipole has an output concentrated in the fore and aft directions, while the output at the sides falls to zero. This directional property is exploited in aerials to improve the signal recovery, and adding a second element makes the array performance still more directional, increasing the sensitivity or power gain in the desired axial directions. The second bass-driver, placed close behind the first in the 6000, constitutes just such a second element, resulting in a simple array equivalent to a two-element FM aerial. In addition, the excursion required for a given low-frequency sound level will be reduced, with the workload shared between two drivers."