JBL CBT 70J-1 Review (Constant Beam Transducer)

[Archaea]

Here is a quick video to show how the speaker sounds off axis. I unhooked all other speakers, and this is just the single front wide (and subs) playing in multichannel stereo DSP mode. I’m planning the camera around the speaker so you can hear off axis. iPhone 11 (non pro) phone camera recording.

If you’d like me to take any other recordings or angles let me know.

 

[Thomas savage]

This is a review and detailed measurements of the special JBL CBT 70J-1 (upper unit) constant beam transducer design. It was kindly purchased new and shipped to me by a member. It costs US $1047 on Amazon including free delivery. You can get it in black or white colors.

Note: our company, Madrona Digital is a dealer for Harman and hence JBL. We have actually installed a number of these speakers in commercial applications. See: https://www.audiosciencereview.com/...ransducer-speakers-in-commercial-project.310/. You may also want to assign as much bias as you feel necessary for the subjective aspects of this review.

Other than being tall and narrow, little hints at the unusual design of this speaker:

View attachment 118768

There are four low frequency drivers and whopping 16 high frequency ones:
View attachment 118769

Using "shading control" the drivers work together to limit vertical dispersion to the height of the speaker.

There are two settings on the unit as you can barely see on the right bottom of the speaker above. One sets the width, I choose wide, and the other, "music or speech." I naturally selected music. JBL documentation shows these settings create the flattest response.

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 2000 measurement which resulted in error rate below 2% up to 10 kHz or so. Above that, error shoots way up so the response there is not correct. I could use more points but as is, it took nearly 5 hours to measure and created a 1.5 gigabyte measurement file!

Testing temperature was around 60 degrees F.

I could not see through the grill to pick a "reference axis" and wouldn't know where that would be anyway. So for measurements, I just picked a more or less center location on the flat part of the speaker.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

JBL CBT 70J-1 Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
View attachment 118771

Harman includes spin data that shows much flatter response than above. Specifically there is no sign of that resonance in their measurements. But it is in every aspect of my measurements. I even heard it during the sweep! The level went up and then back down in the middle. We can see evidence of resonance in waterfall display:

View attachment 118772

And evidence of even more of then in impedance and phase graph:
View attachment 118773

I could also see it in the 'in-room" distortion measurements:

View attachment 118774

Speaking of distortion, it is extremely low:
View attachment 118775

Sure, it doesn't attempt to play very low but what it does play is very clean.

Efficiency is the highest I have measured of any speaker I have tested, clocking at 92 dB or so.

Early window reflections are very good:
View attachment 118776

Notice how the ceiling reflections - dashed red - are at so much lower level due to beam forming produced by CBT technology. Floor reflections are not that much reduced though.

Our predicted in-room frequency response is very good, sans that resonance:

View attachment 118777

Horizontal directivity is wide and not controlled a lot:
View attachment 118778
View attachment 118779

Vertically, it is another game altogether:
View attachment 118780

This thing is a shaft of sound coming at you! Vertically directivity control is definitely there.

Listening Tests
The efficiency advantage came through immediately as soon as I played my first track through the CBT J70-1. I could barely turn up the volume before the speaker would fill my large space with ease. Turn it up even more and it can get scary loud with no hint of distortion! Granted, deep bass is not there but everything above that plays with incredible efficiency and dynamics.

Tonality was very good but I thought I take down the resonance peak with EQ:
View attachment 118781

The difference was subtle. The sound was more open now, more detailed and slightly less harsh. Once there, I sat and listened and listened! It was an incredible experience.

If you have not ever heard a CBT speaker, it is something altogether different. You can walk up to it and level barely changes. Ditto for going back or even moving horizontally. It can almost be called "constant level speaker!" You feel like you are freed from sitting like a statute in a fixed spot. You can walk around a large area and overall response of the speaker barely changes. It is so uncanny and what I experienced when I listened to these at Harman years ago. They had them in this massive airplane hanger type building. Yet these were filling them with so little drop off in level as you walked forward and back.

While these speakers are a natural for outdoor use, they also make great surround speakers. They solve the issue of the people sitting to the sides hearing too much of the surround speaker closest to them.

Conclusions
I must say, while I expected to hear the nice experience of CBT beam forming, I did not expect the speaker to sound so correct tonally. And be so efficient and effort-free. With just that bit of EQ, you have a very high performance speaker. They need bass enforcement though. I have the companion lower half of this speaker which I will test next.

I am going to strongly recommend the JBL CBT 70J-1. You need to hear one to open your vista of what is possible with a bit of complex math.

------------
As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Looks awesome, I want at least 2 of these .

 

[dcolak]

Power Rating1000 W (4000 W peak), 2 hrs 700 W (2800 W peak), 100 hrs

JESUS! JBL does not play around.

https://jblpro.com/en/products/cbt-70j-1-plus-70je-1-system

 

[Bjorn]

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.

Where are those claims? And I assume they don't have any measurements?

I highly doubt the McIntosh use any "CBT technology" at all.
I've also listened to them and didn't recognize any "CBT sound". They would also need a license from JBL.

 

[nick-v]

Cool review. I was considering a pair of these in the garage (with a subwoofer).

 

[bigguyca]

Very interesting review. Size factor suggests they could be used as R and L for home theater. What would you use for center speaker?
Opinions please. Thanks

Get a decent sound bar instead.

 

[kaka89]

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.

Still don't get it. If change to closer distance, SPL will go up but everything else should remain the same.

The graph looks like only one treble is making sound.

 

[Rick Sykora]

Where are those claims? And I assume they don't have any measurements?

I highly doubt the McIntosh use any "CBT technology" at all.
I've also listened to them and didn't recognize any "CBT sound". They would also need a license from JBL.

Hi Bjorn!

From the McIntosh website...

“The ported, 4-way XRT1.1K speaker uses our line array design to yield an even and wide sound field, producing exceptional stereo imaging in nearly all listening positions. With our line array speaker design, listeners closer to the XRT1.1K will not be overpowered by extremely high volumes as they will only be on axis to a portion of the drivers; listeners farther away will be on axis to more of the drivers and will be able to easily hear the music without any large drop off in sound level or quality.”

Those claims sound pretty CBT-like to me.

Btw, I have not heard them so just saying.

 

[Archaea]

I saw someone post that the AMC movie theater had them in wrong orientation and they should be side by side with the bass modules. That is not correct. The mounting bracket that comes bundled free with the speakers to join the 70j-1 and the 70je-1 will only work with vertical orientation.

https://jblpro.com/en/products/cbt-70j-1-plus-70je-1-system

 

[RealityCheck18]

@amirm
Thanks for taking the time to test the speaker, and for doing this service to the audio community that you seem to tirelessly attend to!!! I see you will do the bass module next - I suppose they are too tall to be tested together?

For cinema, I don't know that I've heard better than these speakers. I've observed that all matching speakers is an incredible boon in the world of atmospheric audio/object based audio, where the Dolby Atmos or DTS-X objects can move between any speaker seamlessly in your cinema, and I'm particularly pleased with the JBL CBTs for that purpose!

Anyway - long read, but I know I like line array and CBT designs from several different experiences, and have further confirmed it with my time of ownership. Your mileage may vary! Thanks again amirm for measuring the speaker and supporting the community!

Thanks for the information, Archaea!

I get asked questions about those monsters in the garage--generally "compensating for something?", why they are what they are and so on. Yes, I built them because I wanted to play around with line arrays--I did and they do what I need a garage speaker to do. This leads to questions about multi-channel and I respond by avoiding the question. Did a ton of research on them as it required 3 builds/rebuilds to get them to make noise reasonably accurate and once there--I stoppped. Sure, I could go full PEQ, rebuild them for the forth time as CBT etc. but even the most avid DIY'er tires of fighting wood, wiring, solder and gaskets. Since I'm a moron and can be dangerous, I built the bezels to be self contained as they unblolt/unscrew and all the drivers drop down so I can fix my screw ups. Since the bezel is a two piece (midranges are enclosed on the baffle) it takes 28 feet or over 8 meters of gaskets every time I take one apart--did that several times and learned how to get 56 feet of gaskets to seal.

Never heard them as a HT system, go to KC for the BBQ and stay for CBT multi-channel.

I would I explain their oddities to a person that has never heard them. OK, I have an idea but a warning right up front...I will use a 4 letter word so hide the children, protect your elders.....here it comes!

Bose 901

Before you light the torches, send in the black choppers or swarms of "murder" hornets after me--let me explain! The 901 has a very different sound, a very big sound....really big as bouncing many full range sources of a corner will do. No claims of accuracy, pin point imaging or even something to strive for but they do sound "big", a feeling of sound bouncing everywhere and a sense of a huge sweet spot you could say. Oddly enough, a Bose engineer built a flat vertical line array in the 70's with 901 drivers but Uncle Amar told him it cost too much, did not mesh well with their marketing and quit wasting time. I get it, Shure back in the 50's used to have voice only speakers that had a stack of full ranges in them for public addresss. We actually had them in our grade school in the gym so not exacty new in concept. MacIntosh back in the late 70's (???) had the same thing with a bunch of tweeters etc. and, of course...the Infinity $50,000 mega speakers from 1980 was long lines of ribbons, drivers etc. that followed that same principle.

I kept messing up my garage arrays, had to get them right for science! Actually, my wife would of busted my stones for life if after all the time, expense and countless purchases of stuff from the local lumber yard my tower of power failed. My long suffering wife only has one rule, whatever stupid thing I'm doing has to actually work before I move on to my next stupid thing. 17 months of effort and 3 rebuilds later--they worked so I played around with push-pull slot loaded subs then once those worked, it was green lighted to allow my garbage to enter the living room.

I thought I was out then Archaea pulls me back in! (Sopranoes) A simple question about surrounds as arrays--this does not necessarily make a simple answer. My adventures in woodworking have netted additional power tools, skills and so on to get more exotic in the past 8 years so--I ponder. On the surface, having arrays for surrounds make sense because a sound field in a bunch of speakers (array = bunch of speakers) in particular spots. A surround field is not supposed to be pin point imaging and arrays tend towards more "everywhere" in their sweet spot so would it work well to mix arrays as surrounds and "point source" as LCR? Since arrays have a distinctive near field, mid field and far field response would there be a disconnect if say the side surrounds are mid field and the rear surrounds are far field? I'll try to compensate for that by making the surrounds that are physically further away have a longer line to get their response more accurate with each other.

For clairity, I would use four Faital Pro 3" full ranges 2S/2P with the CBT curve and a 6.5" as a "side woofer" and eight 16 ohm Faitals 2S/4P with an 8 inch side woofer for the rear surrounds to make up for the longer distance required. Sure, I'd have to use EQ to make it work but not an issue. I just ponder how well "point source" LCR's mesh with arrays as surrounds and different array lengths (or height) will cause issues. Since I have four or more butts in the seats, I am more concerned with coverage than the ultimate in frequency response.

Sorry for the questions, it has been around 8 years since I read everything about arrays and wonder if they play well with others as surround fields. Nice rig by the way, now to figure out a way to BS my wife into going to KC for some reason...not a big BBQ fan, not really a Chiefs fan (or sports fan) so I'll have to figure out something.

Now for those full monty measurements with the bass boxes--it's only money, right?

 

[Rick Sykora]

They discontinued the CBT24s? That is disappointing.

Yes, since end of 2019 that PE stopped selling kits and finished speakers. Might have gone for the CBT36 had I known. Was rather sudden but sniffs like a business decision. They really did not fit their business model well.

 

[Bjorn]

Hi Bjorn!

From the McIntosh website...

“The ported, 4-way XRT1.1K speaker uses our line array design to yield an even and wide sound field, producing exceptional stereo imaging in nearly all listening positions. With our line array speaker design, listeners closer to the XRT1.1K will not be overpowered by extremely high volumes as they will only be on axis to a portion of the drivers; listeners farther away will be on axis to more of the drivers and will be able to easily hear the music without any large drop off in sound level or quality.”

Those claims sound pretty CBT-like to me.

Btw, I have not heard them so just saying.

Thank you.
They would need some quite sophisticated DSP and many amps to get true CBT quality in their straight line array. Since that's not the case this being a passive speakers, I don't think this is much other than some marketing language. But they have the line array drop off per meter.

I can assure you, even the low cost CBT36 with some subwoofers is way beyond and expensive regular line array. A CBT speaker basically solves the issues a line array speaker has.

 

[Archaea]

@RealityCheck18

Seriously if you are in KC - send me a PM. We'll go get some great BBQ, and then come back and audition some music and maybe watch a movie.
Covid be darned.

As to using line arrays or CBTs as surrounds. yes. I noted in my previous post that placement is more flexible because of their wide coverage, and even close proximity to a particular seat isn't a bother because they will not blast out your audience like a traditional speaker will. Since the sound is spread over so many drivers, and space, I can walk right up to the speaker at reference volume and put my ear almost up against a tweeter and not need to wince. Try that with a traditional loud speaker.

I personally am a fan of all matching speakers in this new world of object based audio, but that doesn't mean you couldn't use these (or your own brew) as surrounds and use whatever you wanted as your LCR. My last two 13 speaker setups have been all matching (13 Mackie C200 before this), and my opinion has solidified that a full match is the optimal way for the cinema experience. To each his own though, and perhaps worth noting, I value and prioritize the best Atmos or DTS-X Cinema experience I can assemble over a potential best two channel audio experience on the subjective scale of preferences.

As to the 'everywhere' aspect of the sound. yes.
Here, I hope this quick video encompasses and relays that uncanny quality. Again another recording on my iphone. Just threw a random song on from amazon music, and put it in multichannel stereo and walked around the room - no tricks/no edit. If you didn't know better you might think it was dubbed audio because the sound is so uniform as you walk around the room. I love that. Sorry for the mess in the room. Maybe I'll have to throw another video later with my room not in disarray to avoid embarrassment. I'm always tinkering with stuff and not so always reliably cleaning up.

All 13 JBL CBT 70j-1 speakers playing in multichannel stereo (no EQ) walking around my HT room to showcase uniformity of sound.

 

[TimVG]

I watched Don Keele's CBT presentation on YouTube one or two years ago.. as far as conceptual design goes, that man is another planet. The floorstanding CBT speakers solve SO many problems in a room compared to conventional speakers I'm still beating myself over the head I didn't go for the Dayton's when they were still available.

 

[Ron Texas]

This technology is fascinating, but strange enough to make me dizzy.

 

[amirm]

There seems to still be some confusion about the operation of these speakers so I thought I get us some 3-D plots to make it clear. They are added to the review now. I am simply changing the frequency but keeping the rest the same. Speaker is facing to the right:

I don't know if lack of cohesivity is due to implementation of CBT breaking down or normal speaker design issues with diffraction and such.

 

[BenB]

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.

There are numerous important differences between the Skylarks (front) and Radicals (back). Spectrally they are actually pretty similar on axis. However Dennis auditioned the Radicals at my house with my subwoofer (the Radicals cannot and will not be loaned out). He auditioned the Skylarks at his house, without a subwoofer. The skylarks are effectively large bookshelf speakers (thus the term flying tower). They are designed to be used away from the wall, and the design incorporates baffle step compensation. The flat-pack denovo cabinet was selected to make it easy to replicate the project, but it does impart more diffraction than I would like. My co-worker built his skylarks custom, with large roundovers, and reduced the diffraction issues by at least 50%.

In contrast, the Radicals have a wide baffle, and were designed for on-wall placement. The wedge shape is one inch deep on the inside, and only 4.5 inches deep on the outside, which is completely rounded. This goes a long way toward mitigating diffraction. It also generates a rather different acoustic presentation compared to a speaker several feet away from the wall. Additionally, the Radicals are a 4-way design, with 15 drivers, compared to a 3-way design with 7. This allows for a greater consistency off-axis (vertically) while the diffraction mitigation allows for greater consistency off-axis horizontally.

As far as I know, the Radicals are universally loved by everyone who has heard them, but they are different from a traditional speaker in so many ways that it's not entirely clear where the magic comes from. Is it the reduced vertical reflections (which may emphasize the horizontal reflections)? Is it the diffraction mitigation? Is it the on-wall form factor (no delayed front-wall reflection)? Is it the dynamics associated with the output capability of all those drivers working together? Is it the combination of all those things? Is it something else entirely?
The skylarks were built in part to answer that question. To my ears, I think the narrow vertical beamwidth is part of the magic, but not all of it. I believe the reflection reduction adds a very small amount of clarity, and improves the ability of the recording to fool you into perceiving the sound source as being separate from the speakers.

The skylarks (and the JBLs, come to think of it) are also small enough to be flipped on their side (which can't be done with my Radicals). This allows the listener a very nicely controlled directivity comparison: Wide horizontal dispersion with narrow vertical dispersion -VS- Narrow horizontal dispersion and wide vertical dispersion. I have tried this test myself, and found that I strongly prefer wide horizontal dispersion (which is probably true whether vertical dispersion is limited or not). I'd be very interested to hear results from owners of this JBL, if they would replicate that test.

 

[BenB]

There seems to still be some confusion about the operation of these speakers so I thought I get us some 3-D plots to make it clear. They are added to the review now. I am simply changing the frequency but keeping the rest the same. Speaker is facing to the right:

I don't know if lack of cohesivity is due to implementation of CBT breaking down or normal speaker design issues with diffraction and such.

The tweeters are spaced about 1.5 inches apart (as best as I can tell). When the wavelength is less than twice that distance (any frequency greater than 4.5 kHz), it gets difficult to control sidelobes, and comb filtering starts to become a problem. They've actually managed a very good result given the spacing they are working with. There's very little musical content above 9 kHz.

Personally, I like a ribbon or AMT in the center of my CBTs, which prevents this from happening, but causes its own integration issues. Everything is a compromise.

 

[Randy Bessinger]

Every iteration of Archaea theater has been a continual improvement. A visit to his theater is a very fun experience for anyone visiting KC.

 

[JimWeir]

Looks a little like a tiny McIntosh XRT.
https://www.mcintoshlabs.com/products/speakers/XRT11K