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Constant Beamwidth Transducer (CBT) Speakers
- Thread starter Rick Sykora
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OP
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- #42
To a certain extent, I concur. IMO, CBTs have a packaging issue that until it can be scaled, not enough people will experience and drive adoption. In this case, Harman owned the patents and controlled the market exposure too. By now, guessing those patents are expired.
There are new patents in the field (see some from M$, I think, from the 2008/9 timeframe. Maybe one from another source.
I'm pretty sure there are others from various of the giant-sized hall array designs, too.
I'm pretty sure there are others from various of the giant-sized hall array designs, too.
We might offer the CBT speaker with plate amplifiers and DSP as a second option to external crossover and amps. Probably Hypex. The drawback is the extra depth added to the speaker. It's an easier solution that resembles passive but with the benefit of active crossover.
I'm sure there are more issues than that. Expense for one. All for how much performance advantage, if any? The assembly is far more complex than for a typical speaker, from cutting the material to wiring up every component. You can probably make several conventional speakers for the time and cost it takes to make one CBT.
New tech is risky. It's like with cars and ICE. There are all kinds of fancy schmancy technologies for improving efficiency and power. Nissan spent beaucoup bucks to develop the supposed holy grail of ICE, the variable compression engine. By the time they got it to market, other companies had invested more in other areas and had superior efficiency and power. In 15 years, after the patents expire, few will want the tech anyway because it turns out that EVs and hydrogen are the future. I can think of only one ICE car I'd want to buy anymore, and Toyota won't take it to the US.
I think CBT is a dead end, or a fun niche, but is never going to be mainstream. The future is in several areas: typical boxes for the 2 channel geeks, omni directional for most people, sound bars for most people,
panel vibration for TVs, and surround for home theater geeks. Beyond that, I don't see much market.
OP
- Thread Starter
- #46
Traditional (passive) speakers are little changed from 30 years ago.
Am not saying CBT is the only answer but it does demonstrate a potential that is beyond the sad stagnation of monopole speakers. From experience, throwing more speakers (ala home theater) at the problem is not a panacea and is not acceptable in most rooms and smaller living spaces either. Owning CBTs, I like the soundfield, but agree the current implementation is a nonstarter for many as well.
Am not saying CBT is the only answer but it does demonstrate a potential that is beyond the sad stagnation of monopole speakers. From experience, throwing more speakers (ala home theater) at the problem is not a panacea and is not acceptable in most rooms and smaller living spaces either. Owning CBTs, I like the soundfield, but agree the current implementation is a nonstarter for many as well.
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Here’s the problem with CBT in a nutshell: show me one that can be used as a center channel with a standard OLED? That said, I could see using the JBL CBTs with 2” drivers or DIY ones built into the walls as sides and rears. They are efficiently packaged for that role and arguably do the required job better than standard speakers. We use CBT50 as surrounds on our deck.
I know someone did a massive horizontal CBT. That trades up the promised vertical constancy for a standard 2-way speaker vertical directivity though.
The combination of a text book vertical directivity, avoidance of floor reflections, greatly minimization of ceiling reflections and either wide or narrow constant horizontal directivity (depending on the design) makes a huge difference when placed in a room with four surfaces. Additionally, the distortion is lowered with the number of drivers and the speaker has the ability to play very loud if you feed it it enough power.
Assembling a CBT speaker certainly takes more time than a traditional speaker.
With a CBT speaker with constant and wide directivity, a center is much less important and one could run phantom center with great result. And obviously if you have sound transparent screen it can be placed behind it.
A lying CBT speaker sort of beats the purpose IMO. Unless you design it differently, you end up with a very narrow horizontal dispersion and wide in the vertical plane. I think a phantom center than is more advisable.
A lying CBT speaker sort of beats the purpose IMO. Unless you design it differently, you end up with a very narrow horizontal dispersion and wide in the vertical plane. I think a phantom center than is more advisable.
I had a vague idea for a possible CBT implementation that might be flexible enough for multiple applications: modular small (like 6" tall) individual units that can be stacked and wall-mounted (since each one is small enough, even something like removable 3M Command Strips can be used to attach each unit to the wall) in vertical line arrays with delay-shading to come reasonably close to the performance of the physically curved CBT (see graphic below). This would be a little similar to how Audience used their ClairAudient 1+1 full-range 3" drivers (https://www.theabsolutesound.com/articles/audience-clairaudient-11-v2-loudspeaker) combined into a line array (https://www.audioholics.com/tower-speaker-reviews/audience-clairaudient-16-plus-16-pre), but here intended for wall-mounting the array. Users would purchase a base unit with speaker terminals on the bottom (I was assuming that it would be mounted several inches above the floor in order to clear baseboard molding and allow for the speaker wire to be connected), then however many additional units to go as close as possible to the ceiling (I was assuming that increased height of the array would result in increased distance for the reduced sound fall-off with distance). Each of these additional units would have special connectors on the bottom and top that would snap onto other units for physical and electrical connections. Some engineering and a DSP crossover unit between the amplifier/receiver and speakers would be required to implement the delayed shading itself, and some design would be required to help with the cosmetics. It would end up looking like a super-long version of https://www.revelspeakers.com/produ...wvar_M8-_color=White-USA-Current&cgid=on-wall with much improved performance, and the characteristics of CBT would be make it particularly compatible with multiple applications. For the center channel, stereo or phantom would have to suffice.
OP
- Thread Starter
- #51
Your assumption is that the center must be well matched to the (other) mains. I have tried that with standard monopoles at least 4 times in my family room without real success. I have mounted the center speaker above, below, on a shelf and sitting on the tv stand. While intended to anchor the sound to the tv, they almost always have drawn too much attention to themselves.
I currently use an OMD-5 as a center and it has worked well with monopoles as well as my CBT24s. As @Bjorn suggested, running a phantom center has worked well too, but my room is only about 14 feet wide. With my CBTs, you can sit in many positions around the room and get good sound. The sound is much better than with any monopole I own or have owned since home theater has been available.
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The center is one of the mains. That’s not an assumption, but physical reality. "Stereo" as we have it is a downmix from the originally intended 3-channel. If you listen to a recording such as the 3.0-channel Mercury Living Presence SACD and compare to the 2-channel downmix of the same performance on vinyl or CD, it's quite clear how much was lost because records couldn't carry three separate channels.
Unfortunately it does often have to be different in some way for practical/aesthetic concerns but ideally this is the style of setup one wants.
(As you can see, that was acceptable for a spring/summer review but not a viable permanent solution.)
While that sounds more like a calibration issue than anything else to me, IMO the best solution is to place the center properly and move the TV up. Our TV starts about 5’5” off the ground. This TV placement should be standard. There are no disadvantages in viewing comfort, unless you use those unsightly “theater chairs” that ball you up. By contrast, with a crotch height TV small children or large pets playing on the living room floor can obstruct the view when between viewer and screen, and they have more opportunity to knock the whole thing over.
I guess that would open up more opportunities for mains (LCR) setups with CBT speakers, too. At least for people who don't have fireplaces front and center. PE's terrible new website makes it impossible to find such a basic specification, but if memory serves CBT24 is around 5' tall, right?
Are the Dayton CBT’s that dark sounding?
I’ve had a pair of OMD-5 for some time. They’re really beautiful, especially in the gloss birch burl veneer. However, they sound quite dark, and if there's not a lot of free space around them they get muddy too.
It almost seems like you've never heard CBT speakers. Have you experienced the physical reality of the reduced sound level fall-off with distance, which is objectively measurable?
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Oh, if you've heard them, then I don't understand your deleted "bullshit" comment about a phantom center or about "dark sounding."
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Simple.
1) phantom centers are bullshit, full stop, and people who propose them as solutions to market impractical speakers should not go around claiming other companies say misleading things. I deleted because I thought it intemperate to say, but the concept is bullshit, as to CBT or any other speaker design.
2) my “dark” comment clearly referenced Mirage OMD-5. If Parts Express CBT meshes well with that speaker, they must sound quite dark too.
From what you've written just now, I'm sure that nothing I have to say would be of value to you.
I have owned a variety of loudspeakers over the years (Celestion, Fried, Spendor, GR Research, NHT, Infinity, Allison, RDL, Guru, JBL, Gradient, Stirling, Revel, among others). Many users of controlled directivity loudspeakers find time-intensity trading to widen the sweet spot when set up so axes cross in front of the listening position and sometimes obviate the need for a discrete center channel speaker (compare with designs from Earl Geddes, Brian Waslo, Duke Lejeune, etc). I have some examples of CD speakers, but the CBT24s are pretty unique in terms of their dispersion characteristics and the only ones that might work reasonably well (in my opinion, as long as the listener is within about 10 feet) without a discrete center or else even with a limited frequency spectrum one (I think this is what Rick was referring to), though perhaps I am more susceptible to the ventriloquist effect than other listeners, as I notice a difference in my perception of image "height" with my eyes open and closed in some of my setups.
Anyway, I won't respond further. Have a nice rest of your weekend,
Young-Ho
I have owned a variety of loudspeakers over the years (Celestion, Fried, Spendor, GR Research, NHT, Infinity, Allison, RDL, Guru, JBL, Gradient, Stirling, Revel, among others). Many users of controlled directivity loudspeakers find time-intensity trading to widen the sweet spot when set up so axes cross in front of the listening position and sometimes obviate the need for a discrete center channel speaker (compare with designs from Earl Geddes, Brian Waslo, Duke Lejeune, etc). I have some examples of CD speakers, but the CBT24s are pretty unique in terms of their dispersion characteristics and the only ones that might work reasonably well (in my opinion, as long as the listener is within about 10 feet) without a discrete center or else even with a limited frequency spectrum one (I think this is what Rick was referring to), though perhaps I am more susceptible to the ventriloquist effect than other listeners, as I notice a difference in my perception of image "height" with my eyes open and closed in some of my setups.
Anyway, I won't respond further. Have a nice rest of your weekend,
Young-Ho
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I get what you are saying that crossfiring is a good technique to balance focus and spaciousness with narrow-horizontal-pattern speakers, but I think you are making an assumption of 2 channel program. In any event wide horizontal pattern speakers violate the conditions required to make crossfiring work.
I'm also not sure I understand your reference to the "ventriloquist effect" or how it relates to CBT speakers or center channels. Can you elaborate? One thing I've noticed in sighted listening to simpler tall line arrays is stretched image height. It would be interesting to see if that holds up when you don't see thin tall things playing the music, or if that is another example of deaf eyes interfering with the ear-brain connection.
Several years ago I had three Gedlee Abbey speakers in the front of a home theater. Having three identical speakers standing with same height (one behind a screen) was something I thought was a dream come true for a home theater. But the center channel had a major and broad cancellation between 100 Hz and 200 Hz area. The result was a complete lack of midbass in the sound with a very lean presentation and despite of crossing over high to subwoofers. So running a phantom center was considerably better. I sold the center speaker.
Some of the reasons why a center is often crucial in setups are because:
1. The front speakers don't have a broad and uniform directivity. Even speakers that score high on reviews here often have a collapsing polar response where they loose the directivity fairly high in frequency.
2. The center is placed further from the side walls. This reduces comb filtering/specular reflections which is detrimental to clarity and intelligibility (a controversial topic here at ASR!). Treating these reflections if one has that possibility basically takes care of that.
While these two points can be addressed, there's one area where a phantom center will suffer compared to a physical center speaker. And that is for listeners further to the side and especially combined with a narrow room. Those listeners will hear one front speaker stronger that the other and due to precedence effect will be drawn to that channel. In those cases, a center channel certainly works better.
Some of the reasons why a center is often crucial in setups are because:
1. The front speakers don't have a broad and uniform directivity. Even speakers that score high on reviews here often have a collapsing polar response where they loose the directivity fairly high in frequency.
2. The center is placed further from the side walls. This reduces comb filtering/specular reflections which is detrimental to clarity and intelligibility (a controversial topic here at ASR!). Treating these reflections if one has that possibility basically takes care of that.
While these two points can be addressed, there's one area where a phantom center will suffer compared to a physical center speaker. And that is for listeners further to the side and especially combined with a narrow room. Those listeners will hear one front speaker stronger that the other and due to precedence effect will be drawn to that channel. In those cases, a center channel certainly works better.
I would like to clarify that the center image of 2 stereo speakers in no way is perceived as less precise compared to a center, from center listening position, with good speakers and decent room acoustics.
Having done this test several itmes myself, it is obvious that the sound quality of the 2 speakers or the center has far more significance for overall perceived sound quality, and 2 stereo speakers of better quality will sound better than a lesser center speaker.