I'm trying to understand what's going on with an upfiring woofer and a 360° lateral reflector.
I assume a usual omni directional dispersion towards the deeper frequencies, and a usual off axis falloff in midrange rising frequencies.
Did you need a lot of trial and error reflector profiles to balance this out laterally, or are there worksheets somewhere for this sort of thing?
I assume a usual omni directional dispersion towards the deeper frequencies, and a usual off axis falloff in midrange rising frequencies.
Did you need a lot of trial and error reflector profiles to balance this out laterally, or are there worksheets somewhere for this sort of thing?
@MITsound & @mayhem13 --
Earlier in this thread, there was some discussion of omni speakers, touching on the Andrew Stewart Hegeman & Don Morrison speakers, specifically. I studied as much about the work of these men as I could find on the web. My 3D printed reflectors were based on their work.
https://www.stewarthegeman.com/home
https://www.stereophile.com/content/hegeman-model-1-omnidirectional-loudspeaker
https://www.morrisonaudio.com/speakers
https://shahinianacoustics.com/ -- mostly Compass-Starter
The above were primary sources. There are numerous posts on various audio forums by users. Most Hegeman/Morrison users appear to be diehard fans. That's one of the reasons I felt compelled to explore their designs: These fans can't all be crazy, can they? Hegeman & Morrison speakers are part of one continuous line of development. Hegeman basically did a technology transfer to Don Morrison in 1977, who then took over the commercial Hegeman speaker development & production. After Hegeman died, Morrison kept going, renamed the company and has been working at omnis now for nearly 5 decades. (For more of this story, see the first link above.) He is still building & selling omni speakers. IMO, that makes him just about the most knowledgeable person in the world on the subject of omnidirectional speakers.
All of their designs have several commonalities:
1. upward facing woofer (some with a forward slant, others straight up)
2. a conical or spherical reflector over the woofer
3. tweeter facing up with similar deflector, most recently above the woofer and/or in the woofer deflector
They also feature the resonance-cancelling multi-tube technology for the woofer that Hegeman invented back in the 50s. This is similar to the KEF metamaterial resonance damping featured in their UniQ Meta drivers. I am exploring this enclosure technology for the woofer as well, in discussions with @knarfor (Frank), who created
https://www.stewarthegeman.com/home but that's another topic.
Morrison speakers have featured a spherical reflector for the woofer for the last couple generations. The reflector for the tweeter went from a ball to one with a more pointed bottom facing the tweeter. Hence my "nipple" ball reflector.
I chose a shallow cone for the first reflectors (v1 & v1.1), 3D printed in purple, to keep the distance between the drivers small. Why? Instinct. It was sized so that when viewed from above, the outer edge of the woofer surround is just visible. The tweeter reflector was sized similarly.
Initial sweeps & listening with these reflectors suggested that a fair proportion of the drivers' energy was radiating more upwards than across. Positioning the mic (@1m horizontal distance) at tweeter height to one foot higher increased overall SPL. Sitting and standing, I could hear this. So, for version 1.2, the black one, the main reflector's contour was made shallower, closer to the angle of the woofer cone to create more of a 90 degree reflection, and the legs shortened to bring the reflector closer to the cone. The latter I misjudged, not taking into account the excursions of the 6.5" cone at low frequencies. At some point during testing or listening, the woofer center cap hit the bottom of the reflector. The cap got crushed inwards (much like domes of tweeter poked in by kids' fingers.
) No measured or audible consequences of that accident, but this is why the pics of the black reflector show it raised up by screws on the based of its legs. The nippled ball tweeter reflector, positioned closer to the dome, was introduced in V1.3 In any case, reflector v1.3 directs more of the speaker's acoustic output horizontall. This was confirmed by both listening & measurements.
So to answer your question
Also, the question of ceiling reflections/cancellations: It's not clear how much of a factor this is. In the studio, there was no shortage of bass energy 40~300Hz. This area sounded amazing. In J&L's huge 8000cf+ room, it's too far away to be significant, and the distance is not constant, as the ceiling slopes upwards from the wall starting at around 10'
The slanted top original Hegeman design was abandoned by Morrison decades ago. I suspect the slanted top was a compromise for close-wall placement, and Morrison decided it was too much of a compromise to tilt the dispersion plane. My choice was practical: I had already made the pentagon towers and it was easy to shift them from morphed-LXmini to omni.
Earlier in this thread, there was some discussion of omni speakers, touching on the Andrew Stewart Hegeman & Don Morrison speakers, specifically. I studied as much about the work of these men as I could find on the web. My 3D printed reflectors were based on their work.
https://www.stewarthegeman.com/home
https://www.stereophile.com/content/hegeman-model-1-omnidirectional-loudspeaker
https://www.morrisonaudio.com/speakers
https://shahinianacoustics.com/ -- mostly Compass-Starter
The above were primary sources. There are numerous posts on various audio forums by users. Most Hegeman/Morrison users appear to be diehard fans. That's one of the reasons I felt compelled to explore their designs: These fans can't all be crazy, can they? Hegeman & Morrison speakers are part of one continuous line of development. Hegeman basically did a technology transfer to Don Morrison in 1977, who then took over the commercial Hegeman speaker development & production. After Hegeman died, Morrison kept going, renamed the company and has been working at omnis now for nearly 5 decades. (For more of this story, see the first link above.) He is still building & selling omni speakers. IMO, that makes him just about the most knowledgeable person in the world on the subject of omnidirectional speakers.
All of their designs have several commonalities:
1. upward facing woofer (some with a forward slant, others straight up)
2. a conical or spherical reflector over the woofer
3. tweeter facing up with similar deflector, most recently above the woofer and/or in the woofer deflector
They also feature the resonance-cancelling multi-tube technology for the woofer that Hegeman invented back in the 50s. This is similar to the KEF metamaterial resonance damping featured in their UniQ Meta drivers. I am exploring this enclosure technology for the woofer as well, in discussions with @knarfor (Frank), who created
https://www.stewarthegeman.com/home but that's another topic.
Morrison speakers have featured a spherical reflector for the woofer for the last couple generations. The reflector for the tweeter went from a ball to one with a more pointed bottom facing the tweeter. Hence my "nipple" ball reflector.
I chose a shallow cone for the first reflectors (v1 & v1.1), 3D printed in purple, to keep the distance between the drivers small. Why? Instinct. It was sized so that when viewed from above, the outer edge of the woofer surround is just visible. The tweeter reflector was sized similarly.
Initial sweeps & listening with these reflectors suggested that a fair proportion of the drivers' energy was radiating more upwards than across. Positioning the mic (@1m horizontal distance) at tweeter height to one foot higher increased overall SPL. Sitting and standing, I could hear this. So, for version 1.2, the black one, the main reflector's contour was made shallower, closer to the angle of the woofer cone to create more of a 90 degree reflection, and the legs shortened to bring the reflector closer to the cone. The latter I misjudged, not taking into account the excursions of the 6.5" cone at low frequencies. At some point during testing or listening, the woofer center cap hit the bottom of the reflector. The cap got crushed inwards (much like domes of tweeter poked in by kids' fingers.
) No measured or audible consequences of that accident, but this is why the pics of the black reflector show it raised up by screws on the based of its legs. The nippled ball tweeter reflector, positioned closer to the dome, was introduced in V1.3 In any case, reflector v1.3 directs more of the speaker's acoustic output horizontall. This was confirmed by both listening & measurements.So to answer your question
Not really. I simply copied existing designs that seemed successful and fine-tuned my interpretation by measurements and listening.
Also, the question of ceiling reflections/cancellations: It's not clear how much of a factor this is. In the studio, there was no shortage of bass energy 40~300Hz. This area sounded amazing. In J&L's huge 8000cf+ room, it's too far away to be significant, and the distance is not constant, as the ceiling slopes upwards from the wall starting at around 10'
The slanted top original Hegeman design was abandoned by Morrison decades ago. I suspect the slanted top was a compromise for close-wall placement, and Morrison decided it was too much of a compromise to tilt the dispersion plane. My choice was practical: I had already made the pentagon towers and it was easy to shift them from morphed-LXmini to omni.
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