Audioholics reviewed and measured it.
https://www.audioholics.com/tower-speaker-reviews/epique-cbt24
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JBL CBT 70J-1 Review (Constant Beam Transducer)
- Thread starter amirm
- Start date
https://www.audioholics.com/tower-speaker-reviews/epique-cbt24
Many thanks for the link. Might be one for this year...
I own CBT24s and the soundstage is great. They do need subwoofers, but mine are in my home theater, so already had. There is a Sound and Vision review here: https://www.soundandvision.com/content/dayton-audio-epique-cbt24-speaker-system-review
They are slim, but do take up some space due to the curvature. Mine were Parts Express closeouts and are no longer available. The JBLs are the only remaining commercial offering, but some others have plans. See this thread: https://www.audiosciencereview.com/...dth-transducer-cbt-speakers.12060/post-351042
tuga
Major Contributor
Welcome to the Harman church, we hope you have a good time:
JBL CBT line array columns installed at The Heath Methodist Church as part of complete Harman solution
https://www.soundtech.co.uk/professional-audio/harman/news/heath-methodist-church-jbl-cbt
JBL CBT line array columns installed at The Heath Methodist Church as part of complete Harman solution
https://www.soundtech.co.uk/professional-audio/harman/news/heath-methodist-church-jbl-cbt
If you are not into DIY and maybe find that that JBLs are not all that impressive, McIntosh makes comparable (CBT-like) claims for their XRTs...
https://www.mcintoshlabs.com/-/medi...RT21K/McINTOSH_020118_gnzphoto-1690-edit.ashx
A member bought a pair of the smaller XRT1Ks used. He offered to have Amir evaluate, but I think getting it into the test fixture was an issue. Something about Amir's back I recall. Maybe his insurance company too.
https://www.mcintoshlabs.com/-/medi...RT21K/McINTOSH_020118_gnzphoto-1690-edit.ashx
A member bought a pair of the smaller XRT1Ks used. He offered to have Amir evaluate, but I think getting it into the test fixture was an issue. Something about Amir's back I recall. Maybe his insurance company too.
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restorer-john
Grand Contributor
Well, if they can reproduce a decent sound in that space, I'm impressed.
But let's consider, line style arrays of PA speakers were used for decades in sound reinforcement, live vocal/speech amplification and general public address. This is just a curved version of a line array, with a little tweaking.
The Grateful Dead tried this on a grand scale-
https://en.wikipedia.org/wiki/File:Grateful_Dead's_Wall_of_sound_schematic.jpg
While an infinitely long line array would theoretically have a 1/r level drop-off with distance as opposed to a 1/r^2 drop-off for a point source, these JBLs are only 27 inches tall. When these are used to provide equal loudness in a big space, it's not because of differences in spreading loss. (Because every seat is in the far-field.) Instead, the speakers are positioned so that their maximum response axis (angle at which they are loudest) is pointed at seats in the back. Seats that are physically closer have a similar loudness level (rather than being substantially louder) because they are off-axis. In order to make this trick work without tilting the spectral balance, the off-axis curves have to be very similar to the on-axis curves.
Additionally, in the rooms in our houses, even point-source speakers can be considered sparse arrays. That's because the reflections create additional virtual sources. The result is that loudness does not drop off at the expected 1/r^2 rate across our whole room. It may approach that rate when very close to the speaker, where the direct sound dominates what we hear. In contrast, at those near-field distances the array will actually exhibit the 1/r loss. At greater distances (12-20 feet or so), I'd expect the point source speaker to exhibit a reduced fall-off rate because the reflections are reinforcing the sound. Since those reflections are reduced with the line array, it will likely exhibit less reinforcement, and actually fall-off faster (if comparing two spots at different distances that are both on the maximum response axis).
Additionally, in the rooms in our houses, even point-source speakers can be considered sparse arrays. That's because the reflections create additional virtual sources. The result is that loudness does not drop off at the expected 1/r^2 rate across our whole room. It may approach that rate when very close to the speaker, where the direct sound dominates what we hear. In contrast, at those near-field distances the array will actually exhibit the 1/r loss. At greater distances (12-20 feet or so), I'd expect the point source speaker to exhibit a reduced fall-off rate because the reflections are reinforcing the sound. Since those reflections are reduced with the line array, it will likely exhibit less reinforcement, and actually fall-off faster (if comparing two spots at different distances that are both on the maximum response axis).
beagleman
Major Contributor
Or, as I have said many times, maybe JUST measurements alone do not dictate if something is pleasing to listen to?
Not everything is "Based on measurements".
I see your comments as "IF it measures good it will sound good, if it measures not too great it will sound unlistenable"
Give yourself some leeway, and move from the "measurements are the only indicator of pleasing sound", Trust me, your life will be happier.
The curve in CBTs makes the differene, but theoretically this JBL is way too short. Curve makes phase shift that greatly enhances vertical beam formation without harming horizontals. With straight arrays same effect can be achieved with shading ie. gradual dsp delay changes or gain/spl shading.
https://www.soundonsound.com/techniques/line-arrays-explained
https://www.diyaudio.com/forums/multi-way/301259-improved-array.html
http://www.audiodevelopers.com/10-case-study-3-a-line-array-with-dsp/
https://www.soundonsound.com/techniques/line-arrays-explained
https://www.diyaudio.com/forums/multi-way/301259-improved-array.html
http://www.audiodevelopers.com/10-case-study-3-a-line-array-with-dsp/
Those beautiful things here are responsible for my biggest auditory disappointment yet. I really wanted to love them, but just couldn't. I think I ended up leaving the demo long before it finished - a first for me.If you are not into DIY and maybe find that that JBLs are not all that impressive, McIntosh makes comparable (CBT-like) claims for their XRTs...
View attachment 118897
https://www.mcintoshlabs.com/-/medi...RT21K/McINTOSH_020118_gnzphoto-1690-edit.ashx
A member bought a pair of the smaller XRT1Ks used. He offered to have Amir evaluate, but I think getting it into the test fixture was an issue. Something about Amir's back I recall. Maybe his insurance company too.
If I recall correctly I was hyped because I had my mind blown with a demo on Piega's Master Line Source earlier in the year. So disappointed I don't ever want to listen to McIntosh ever again!
Interesting, so what is the difference in frequency response between the Radicals and Skylarks?
I noticed your Skylarks have a similar radiation pattern to the JBLs.
They discontinued the CBT24s? That is disappointing.
I don’t get the narrow vertical dispersion too.
How is this "full height" of the speaker when the graph show only one beam.
Archaea
Active Member
I wonder if this is an artifact of the spinorama measuring system - against the unique design of the speaker? I say that because that is not my experience in person. I can sit on the floor in my room, chair, stand, walk right up to the speaker and anywhere in between and it all sounds the same. In person I would not have guessed there was a focused beam of vertical dispersion. I can’t really wrap my head around that from my subjective experience. I’ll take a video with my cell phone of a speaker playing and move my phone vertically in front of it to try to pick up how it works with vertical dispersion on video footage and share the link.
Edit. If I lay on the floor basically underneath the speaker the sound is very muffled, but in the center of the room sitting on the floor where one would as overflow seating, say on a bean during a movie the sound is quite good and similar to the main seating position. So yes extreme off axis vertical perspectives change the sound more than horizontal. But I still not sure I’d think of this as narrow vertical dispersion in listening to it? I uploaded a video a few posts forward to show off axis listening.
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I don't really trust these speakers from the measurements, the fact the measurement was inaccurate above 10kHz, and the 800Hz resonance, and the very narrow vertical directivity....I can't really align all that to a great listening experience. Interesting to see a totally different type of speaker design tested though, perhaps some of it's secret sauce isn't coming through in the measurements or my interpretation of them.
This technology fascinates me! How does the listening experience compare to omnidirectional speakers? This seems like a better way to meet some of the same objectives.
Amir’s graphs are set to 10m distance (SPL adjusted to 1m), so at that super far distance, while a traditional speaker wouldn’t matter as long as it’s in the far-field, this speaker obviously is not traditional; so I think if Amir recomputes it at a normal listening distance (say 3m) that it would look more sensible.
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