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JBL CBT 70J-1 Review (Constant Beam Transducer)
- Thread starter amirm
- Start date
I immediately thought the same. I took a healthy-sized rubber band, stretched it, and measured it as I plucked. First, the primary tone was around 250 to 350 Hz. Second, there were a lot of harmonics. Third, I had to pull it extremely tight to get up to 600 Hz, then it broke. A bungee is, of course, much thicker and would resonate even lower, most likely.Maybe they have a resonance of 800Hz
I suspect it is those large flat sides. @amirm, can you tap on them and measure what happens?
D
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I have no idea what to make of these. I guess it would be the mother of all soundbars, but what would happen if you tried to use them as a 2-channel setup. What would it sound like?
sam_adams
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Can you dig it?
sam_adams
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Don Keele is one of the primary patent holders for CBT tech. He has some really good videos that explain the soundfield. This presentation compares a floor standing CBT to the older B&W 801....
http://audioartistry.com/brochures/B&W 801 vs. CBT36 Ground-Plane Measurements v8.1.pdf
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The distortion between 1kHz ad 4kHz staying constant at 40dB SPL regardless of the listening level is intriguing.
As this is the highest sensitivity speaker ever tested here, this could possibly be coming from the amp or source...
As this is the highest sensitivity speaker ever tested here, this could possibly be coming from the amp or source...
Yes, these are part of JBL Professional products.
They have special software for deployment...
sam_adams
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CBT tech is derived from work the U.S. Navy did back in the '70s and '80s with sonar technology. Think one ping only.
https://www.xlrtechs.com/dbkeele.com/CBT.php
https://www.xlrtechs.com/dbkeele.com/CBT.php
I'll be using the little brother CBT 50-la for surround duty in a home theater project to be finished in the next month or 2 with JBL M2 LCR. Looking forward to the integration! Don't let the MSRP price scare people away from these models. Significant discounts to be had by several pro audio retailers who do high volume sales.
So like the 7 series and the M2
When do we draw the line of ignoring pre-EQ FR for passive speakers meant to work with EQ?
AndreaT
Addicted to Fun and Learning
Amir,
wonderful review and introduction of CBT sound diffusion. However, and I might be missing something, the sound is less decreasing/decaying its volume as my distance from the source (speaker) increases, but the very narrow vertical beam for frequencies over 250 Hz limits where I should position my head to hear the full bandwidth of the music signal. Should they be used in a multi-array multi-channel set-up only to increase the sweet spots? Do I understand this right?
wonderful review and introduction of CBT sound diffusion. However, and I might be missing something, the sound is less decreasing/decaying its volume as my distance from the source (speaker) increases, but the very narrow vertical beam for frequencies over 250 Hz limits where I should position my head to hear the full bandwidth of the music signal. Should they be used in a multi-array multi-channel set-up only to increase the sweet spots? Do I understand this right?
OP
- Thread Starter
- #36
It is not a tiny source. You have the full height of the speaker as far as vertical alignment. Is this what you were asking?
This is an interesting speaker! Now I'm also curious how cbt 1000 would measure on the klippel NFS. The horizontal beam pattern seems like a best of both worlds situation for long rooms:
"Patent-pending Tapered Horizontal Waveguide provides a continuously varying horizontal dispersion (very wide for short-throw, narrower for long-throw) delivering superior coverage in both the front and rear corners of a room (CBT1000)"
"Patent-pending Tapered Horizontal Waveguide provides a continuously varying horizontal dispersion (very wide for short-throw, narrower for long-throw) delivering superior coverage in both the front and rear corners of a room (CBT1000)"
I have designed a (relatively) simple, passive speaker that approaches a very narrow CBT response vertically. If anyone is interested in these types of designs, they can get their feet wet for only $750 a pair, which gets you all the drivers, all the crossover parts, and flat pack cabinets (that still require cutting holes, and building an internal enclosure for the mids). EDIT: the tweeter appears to be unavailable.
http://techtalk.parts-express.com/f...owers-nested-array-speakers-in-denovo-cabinet
http://projectgallery.parts-express.com/speaker-projects/skylark-flying-towers/
Comparing these to traditional speakers, here are some of the observations that I have heard, or which others have communicated to me:
Enhanced clarity, while maintaining a wide soundstage.
Consistent spectral balance throughout the room, and even into other rooms on the same floor (while traditional speakers get dark the farther away you get). This ended up being a major reason that my co-worker built a pair. This feature allowed him and his wife to enjoy music more.
Brighter sound. I prefer a response that tilts down a bit on speakers like this. I suspect that the floor and ceiling reflections have a tendency to shift the perceived spectral balance (making it darker) and when you suppress those, a flat speaker can sound bright and very unforgiving. Perhaps the JBLs didn't cause this in part because they aren't actually reducing the floor reflection significantly. The narrower the beam, the more difficult it is to maintain consistency.
High dynamics. This comes with having the extra drivers it takes to achieve the narrow beam.
High measured sensitivity, but not perceived as high. For a traditional speaker, there's typically as much or more energy arriving from the vertical reflections (combined) as there is direct sound. Reduce those reflections significantly, and you reduce the perceived loudness. I suspect this same reduction in perceived loudness also impacts the perceived strength of the lateral reflections. Since they don't have to compete with vertical reflections, the strength of the lateral reflections is relatively enhanced. This can be a benefit if you can manage a bit of space, or if you diffuse the first reflection points (if they are too close).
A greater ability to disappear, and let the spatial cues in the recording come through.
I haven't heard the JBLs. The measurements look pretty nice, except for the resonance we're all waiting to hear an explanation for. I do think that it takes two speakers to appreciate the soundstage and imaging differences associated with this type of speaker. I wonder if Amir will be intrigued enough to set up a stereo listening session somewhere, somehow, and report his experience. Perhaps the owner will comment.
http://techtalk.parts-express.com/f...owers-nested-array-speakers-in-denovo-cabinet
http://projectgallery.parts-express.com/speaker-projects/skylark-flying-towers/
Comparing these to traditional speakers, here are some of the observations that I have heard, or which others have communicated to me:
Enhanced clarity, while maintaining a wide soundstage.
Consistent spectral balance throughout the room, and even into other rooms on the same floor (while traditional speakers get dark the farther away you get). This ended up being a major reason that my co-worker built a pair. This feature allowed him and his wife to enjoy music more.
Brighter sound. I prefer a response that tilts down a bit on speakers like this. I suspect that the floor and ceiling reflections have a tendency to shift the perceived spectral balance (making it darker) and when you suppress those, a flat speaker can sound bright and very unforgiving. Perhaps the JBLs didn't cause this in part because they aren't actually reducing the floor reflection significantly. The narrower the beam, the more difficult it is to maintain consistency.
High dynamics. This comes with having the extra drivers it takes to achieve the narrow beam.
High measured sensitivity, but not perceived as high. For a traditional speaker, there's typically as much or more energy arriving from the vertical reflections (combined) as there is direct sound. Reduce those reflections significantly, and you reduce the perceived loudness. I suspect this same reduction in perceived loudness also impacts the perceived strength of the lateral reflections. Since they don't have to compete with vertical reflections, the strength of the lateral reflections is relatively enhanced. This can be a benefit if you can manage a bit of space, or if you diffuse the first reflection points (if they are too close).
A greater ability to disappear, and let the spatial cues in the recording come through.
I haven't heard the JBLs. The measurements look pretty nice, except for the resonance we're all waiting to hear an explanation for. I do think that it takes two speakers to appreciate the soundstage and imaging differences associated with this type of speaker. I wonder if Amir will be intrigued enough to set up a stereo listening session somewhere, somehow, and report his experience. Perhaps the owner will comment.
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Alice of Old Vincennes
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This is a confusing speaker. Will take some time to digest. This why site is stimulating. In my wildest dreams did a think this design would work. My, my!
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