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

[yourmando]

@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?

As to my experience/opinion on using 13 of these JBL CBT 70j-1 speakers in a 9.8.4 HT setup; I've posted that previously in post 3 linked below, so I'll let you read more there if inclined.
https://www.audiosciencereview.com/...eakers-in-commercial-project.310/#post-435727

In summary, I think they are fantastic. Someone asked about stereo listening. They are a very different sound than what you are most likely familiar with in traditional speakers. They have a sweet spot a mile wide, as in you could literally be in the chair on the either side of the center, main listening position, and it would sound like you are in the main listening position. This compared to many high end audiophile speakers I've auditioned in various home theaters that seem to have a very clear single centered sweet spot about 6" wide.
The CBTs do not have that focused center image sound that a stereo purist might seek, rather it's more of an “all around you" sound. Stereo listening is almost like engaging a multispeaker DSP function. Sometimes when I'm stereo listening I have to double/triple check to see if Dolby Surround or multi channel stereo engaged. With all thirteen speakers in multichannel stereo it's uncanny. I can walk anywhere in my home theater and it all sounds the same. Kneel, sit, or stand. All Uniform sound. No hot spots, no weak spots. With the eight 18” subwoofers, the bass is uniform too. It's a party trick I always show new visitors. Most I've demoed for have never heard anything like it. AND because of the distribution of the sound via the multiple drivers in each speaker you can walk right up to the speaker played at reference volume and not wince. That character makes them a great choice for a surround speaker that has to be too close to a particular seating position.

These JBL weren't my first exposure to CBT / Line Array technology speakers, I've had a few experiences and I've liked all of them.

My first audition was to the AVS123's LS6 and LS9.
View attachment 118848
I heard them at a few audio meets, and one of my friend's has a pair. They sounded great, but discontinued, HUGE, complicated, and now expensive, I wasn't going to buy a set of 13 of these.

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The second exposure was to a set of Selah Game Changer Line Arrays at a "Heavy Hitters" blind testing audio meet in PA. The Game Changers stole the show for me. They were diminutive, the smallest speaker in the lineup, and I initially smirked that they entered a big boys competition because they had such tiny little drivers. In the blind audition, they filled the room completely - sounding the same everywhere, and blew me away. I had no idea what speaker was playing, but it was my favorite and I was incredibly surprised I picked them as my favorites over the other much more visually imposing candidates. Again too expensive for me, but I sure liked them!
View attachment 118849
Video footage of that Heavy Hitters G2G and meet. What fun!
(13) Gorilla83's Home Theater Heavy Hitters Meet, with stops at Popalock's, Craig John's, and DMark1's - YouTube
The blind testing day starts at around the 18:30 mark. (Some crazy stuff in this video -- want to see what 16, eighteen inch subwoofers do in a home theater? Skip to timestamp 15:35)

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My third experience hearing a CBT design was at Axpona 2017 when Don Keele (the designer behind the CBT design) helped introduce the Epique CBT24K speaker as an audio speaker in partnership with Parts-Express. I walked by a mammoth pile of speakers (various products P.E. carried) with the CBT24K out front stand alone. As I walked by the display the sound was like a uniform wall, it sounded the same no matter where I walked within about a 20 foot range in the hotel lobby. It truly baffled me because I couldn't tell where the sound sourced from. It wasn't directional and barely changed volume as you walked closer or further away from the stack of speakers? How weird! The buddy I was with asked me if the sound was from the Epique line arrays, since he spotted and recognized Don Keele talking among the passer-bys, and understood the technology more than me. I told him no - it didn't sound like those little speakers could be doing that big sound, so I proceeded to walk up to the mountain of speakers and start putting my ear next the various drivers trying to figure out what speaker was producing such a uniform sound regardless of where you walked ---- were all the speakers on I initially wondered? I came to the realization it was, in fact, the little Epique CBT pair with tiny 2.5" drivers. I was blown away yet again. My buddy and I both bought a pair right there at the trade show floor! Sadly I never got around to putting mine together. My intent was to put them in my living room. Life happens - it's still unfinished. Someday?
View attachment 118850


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My fourth experience (actually my third experience chronologically) was the local Kansas City AMC Prime movie theater
View attachment 118854

This premium theater was setup with a full host of these JBL CBT 70j-1 speakers with the bass module 70je-1 mated to (brand new at the time) Dolby Atmos processing. I was blown away again. It was my favorite commercial movie theater sound experience I'd ever had - and nothing else was even close. The sound experience was amazing, the music as the credits rolled was utterly fantastic! My buddies and I after the movie spent time commenting on just how excellent the sound was, we took pictures of the speakers, and tried to identify them. I looked them up, $1200 a piece for the mainspeaker CBT 70j-1 and then another $600 a piece for the bass modules CBT 70je-1. Ouch! As you can see in the picture the AMC had a LOT of money in those JBL CBT speakers!
Ugh. Too expensive, yet again, but since these were a mass production speaker I figured I might have a good chance of getting some used cheaper. I set up an eBay alert and got occasional alerts for the next ~ 3 years. Finally an auction popped up locally with 34 JBL CBT 70j-1 that a company had used for a couple 5K races - and had stringed them along the race path (because of the CBT characteristic of losing SPL at half the rate per distance of a traditional speaker). The seller was about 60 miles away so I could do local pickup, and he was selling them cheap. I bought 13 for about $420 each.
View attachment 118851

There's more to the story, 10 of the 13 had an 8 ohm sandbox resistor that had failed, making a 10dB dip at 2Khz, so I had a LOT of unscrewing and crossover solder work to do, but ultimately I got them all fixed with the guidance of some smart, helpful guys on the DIY board at avsforum - measured with a calibrated omnimic as overlaying each other correctly, and finally was good to go!
All 13 overlay each other correctly when measured from the same position (FR measurements taken indoors inside my home theater room - all from the same position to validate each speaker was working similarly), metal speaker grills removed in all instances — I use them without the grills)
View attachment 118936
View attachment 118852
While all were disassembled, I installed the RGB 5050 lighting strips behind the tweeter array to match the AMC Theater look and that's where I now sit.
(I bought three more new last year, to eventually bump my HT system to 16 channels, and Amirm was sent one of the new units, which I tested before hand to verify it overlaid with my current 13 speakers in frequency response perfectly -- it did), so if the unit amirm measured was defective, then my 13 are also defective. (at least based on frequency response taken by my omnimic)

I've been through a lot of speakers in 15 years. (6 entirely different sets in my home theater room. Klipsch, Wharfedale, Elemental Designs, JTR, Mackie, and now these JBL CBTs) These are the first speakers where I feel like I'm done. I've had them now for about 3 years, I have zero intent of replacing them. Similar to my search for subwoofers, with both I've found my own place of satisfaction, and I do not need, or even desire to chase something else.
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!

If any of you are ever in the Kansas City Area and desire an audition of my setup let me know. I enjoy giving HT demos, and talking audio with other enthusiasts.

As @jhaider and @Spocko mentioned, these speakers seem ideal for a surround setup. @Archaea’s matching surround setup must sound amazing. I believe he’s heard a great deal of the best speakers in dedicated home theaters across the country, and considers these CBT JBLs among the very best.

What I don’t understand is why these speakers are talked about or used more for dedicated home theater use???

They seem to solve the major problem where even in a large-ish home sized room (say 20x30’), you are left with a very small sweet spot of “good seats” with the middle couple of seats of 2 rows maybe.

With the latest object based audio formats with pin point sound locations, sound from every speaker needs to be heard from every seat. So the modern way of laying out speakers aims all the speakers toward the 1 “master seat” in the center, and all other seats have to be within the sweet spot of the speaker dispersion.

A wide a controlled dispersion solves this.

But also, any seats close to any speakers get that level too loud, so seats away from the very center get the double whammy of being off axis for some speakers and getting some speakers too loud and annoying in their ear.

The CBT design solves this too, with the 3b instead of 6db drop off with distance doubling.

Finally, these speakers are very efficient, so should be able to easily get to reference at every seat in a normal home.

Because directivity is well controlled, these are very EQ-able, and room correction plus something like @Maiky76’s speaker EQ for above transition would bring these up to a very accurate performance level.

I’m currently researching for my own dedicated home theater build, and it seems most common recommendations are JBL Synthesis, Triad, JTR, Procella etc.

It seems like this solves problems that none of the above do, and at a really goood price point of about $1k per speaker. There are some other high end line array designs for home theater from the likes of Widom Audi and Steinway, but prices are on another planet entirely.

Is there something I’m missing about trade offs for this JBL CBT? Why shouldn’t I consider these above all others mentioned above? It seems almost too good to be true!

 

[Ericglo]

A CBT with Revel-level build and finishing, plus focus on FR smoothness would be killer. I think the rejuvenation it would bring to Harman's home audio lineup would outweigh the risk of fragmentation.

So here you have some amazing speaker technology from JBL that can be described as the "perfect" home theater surround speaker due to the constant amplitude of sound regardless of the seating distance. Why hasn't JBL explored this further for dedicated HT use?? It's like they have a gold mine of technology buried and no product manager to uncover the treasure that lays within.

I am a HUGE FAN of these linear array speakers, if only JBL can dedicate their vast resources to make this happen.

I am a big fan of CBT tech, so don't take this the wrong way. What makes you guys think JBL hasn't looked at this and dismissed this as an approach they want to use? Harman has the Synthesis lineup for their ultimate HT setup. I am no where near as knowledgeable as Floyd Toole and he has said he would not use CBTs for LRC duty. He did say they are great for surrounds.

 

[Spocko]

As @jhaider and @Spocko mentioned, these speakers seem ideal for a surround setup. @Archaea’s matching surround setup must sound amazing. I believe he’s heard a great deal of the best speakers in dedicated home theaters across the country, and considers these CBT JBLs among the very best.

What I don’t understand is why these speakers are talked about or used more for dedicated home theater use???

They seem to solve the major problem where even in a large-ish home sized room (say 20x30’), you are left with a very small sweet spot of “good seats” with the middle couple of seats of 2 rows maybe.

With the latest object based audio formats with pin point sound locations, sound from every speaker needs to be heard from every seat. So the modern way of laying out speakers aims all the speakers toward the 1 “master seat” in the center, and all other seats have to be within the sweet spot of the speaker dispersion.

A wide a controlled dispersion solves this.

But also, any seats close to any speakers get that level too loud, so seats away from the very center get the double whammy of being off axis for some speakers and getting some speakers too loud and annoying in their ear.

The CBT design solves this too, with the 3b instead of 6db drop off with distance doubling.

Finally, these speakers are very efficient, so should be able to easily get to reference at every seat in a normal home.

Because directivity is well controlled, these are very EQ-able, and room correction plus something like @Maiky76’s speaker EQ for above transition would bring these up to a very accurate performance level.

I’m currently researching for my own dedicated home theater build, and it seems most common recommendations are JBL Synthesis, Triad, JTR, Procella etc.

It seems like this solves problems that none of the above do, and at a really goood price point of about $1k per speaker. There are some other high end line array designs for home theater from the likes of Widom Audi and Steinway, but prices are on another planet entirely.

Is there something I’m missing about trade offs for this JBL CBT? Why shouldn’t I consider these above all others mentioned above? It seems almost too good to be true!

Couldn't agree more - I gave up the search for CBT speakers that were not DIY about 2 years ago. I did see these JBLs but they were specifically marketed for PA use, so I just marked them off my list. I assume that the business case is not there because it's too hard to design these speakers in a way that is compliant with the wife-acceptance-factor. But I can't imagine they would appear any worse than Vivid's Giya speakers. Maybe the marketing team and product strategist didn't know how to properly position them in their product lineup?

 

[Ericglo]

As @jhaider and @Spocko mentioned, these speakers seem ideal for a surround setup. @Archaea’s matching surround setup must sound amazing. I believe he’s heard a great deal of the best speakers in dedicated home theaters across the country, and considers these CBT JBLs among the very best.

What I don’t understand is why these speakers are talked about or used more for dedicated home theater use???


Is there something I’m missing about trade offs for this JBL CBT? Why shouldn’t I consider these above all others mentioned above? It seems almost too good to be true!

People get locked into certain brands and speakers. They seem to be ideal for surround, but Toole doesn't think they are as good for LRC. With that, what LRCs would one match them with?

And yes, you did mention the popular brands. Wisdom and Steinway are very expensive. Wisdom does sound great, but at a couple hundred thousand it better.

 

[yourmando]

I am a big fan of CBT tech, so don't take this the wrong way. What makes you guys think JBL hasn't looked at this and dismissed this as an approach they want to use? Harman has the Synthesis lineup for their ultimate HT setup. I am no where near as knowledgeable as Floyd Toole and he has said he would not use CBTs for LRC duty. He did say they are great for surrounds.

I’d be interested in hearing why they don’t pursue this approach as well. There must be some technical reason.

A non-technical reason would be that they don’t want to cause confusion with their own luxury synthesis lineup, which is based also very similar to their pro cinema solutions. But there has to be more than that.

 

[yourmando]

Couldn't agree more - I gave up the search for CBT speakers that were not DIY about 2 years ago. I did see these JBLs but they were specifically marketed for PA use, so I just marked them off my list. I assume that the business case is not there because it's too hard to design these speakers in a way that is compliant with the wife-acceptance-factor. But I can't imagine they would appear any worse than Vivid's Giya speakers. Maybe the marketing team and product strategist didn't know how to properly position them in their product lineup?
View attachment 119331

The WAF factor is a good point, which is why I mentioned the CBTs potentially being awesome in the context of a dedicated home theater.

Whatever speakers I use will be hidden by an acoustically transparent screen or by stretch fabric along the walls. So bring on the ugly speakers and just give me the best performing for the application

 

[Spocko]

The WAF factor is a good point, which is why I mentioned the CBTs potentially being awesome in the context of a dedicated home theater.

Whatever speakers I use will be hidden by an acoustically transparent screen or by stretch fabric along the walls. So bring on the ugly speakers and just give me the best performing for the application

OR maybe it's a moot point because when you have a 7.1 bed layout, the surround DSP can create a sound field that is "good enough", whereas the CBT would reign supreme if you only had a 5.1 layout.

 

[PeteL]

I find it odd that Dolby doesn’t use specific speakers for all their theaters. The ones by me use dual horns (one facing towards the other end and one facing downwards):

Dolby builds theaters?

 

[TimVG]

I am no where near as knowledgeable as Floyd Toole and he has said he would not use CBTs for LRC duty.

I bet those reasons would not be related to sound quality.

 

[MZKM]

Dolby builds theaters?

Dolby Cinema, which feature Dolby Atmos and dual 4K laser projectors. It’s Dolby’s equivalent to IMAX (usually, theaters only have LieMax, very few have dual 4K laser IMAX with 11.0). Every blockbuster I see in my local AMC’s Dolby Cinema ($16-$18 a ticket), I only see “regular“ movies in regular theaters.

Just like IMAX, I presume Dolby has a hand in each theater built and sends their technicians to calibrate it.

 

[Ericglo]

I bet those reasons would not be related to sound quality.

I am not going to speak for Floyd. He knows Keele and was around during the development of CBTs, so I am sure he has a better understanding of there ablities.

 

[Joecarrow]

I’m quite interested in the audible consequences of the ~800hz resonance after equalization. Is it OK then, or are there lingering issues? What do we need to look at to determine the severity?

 

[yourmando]

I am not going to speak for Floyd. He knows Keele and was around during the development of CBTs, so I am sure he has a better understanding of there ablities.

I found a @Floyd Toole ’s comment on avsforum about not using the CBTs as LCRs but would as ideal surrounds.

Unfortunately, he doesn’t elaborate. (Note in the link above, he replied in the quote block so it‘s a bit hard to parse which are Floyd’s comments):

”I am puzzled by this comment, as it is simply not true. The CBT 70J-1 and the much more substantial CBT 1000 both deliver eminently satisfying music in their switchable "music" modes. The designer, Doug Button, absolutely knows what accurate sound reproduction is, and aims for it. They are used by bands, as well as lecturers. I have spent enough time listening to music through these to have great respect for the fact that significantly high sound quality has been preserved while delivering selectable controlled-directivity sound. I would not choose them for LCR duties, but in the right rooms I would not hesitate to employ them as surrounds, where they have the unique advantage of being able to deliver similar sounds to both ears of several listeners across the width of the room, the advantage described in my books. Check out the frequency response and directivity measurements in the published spec sheets. They are competitive with several pretentious "high end" consumer loudspeakers, but that, frankly, is not a very high bar .”

I also found that JBL did a synthesis demo at CEDIA 2015 using SDP-75 with M2s as LCR and CBT-50s as surrounds, so it does appear to be a thing.

I’d love to hear more about why not using the CBTs as LCR. Sure M2s measure better (and cost 10x more) and their directivity and SPL variance would work fine as the LCRs are furthest away so no seats should be overly loud unless really close to the screen/front wall.

 

[Ericglo]

I also asked him about CBTs on AVS and he didn't elaborated IIRC.

 

[Ericglo]

I found Floyd's reply to me from four years ago:

I know this is probably a question for the current group at Harman, but I will inquire anyway. Is there a reason JBL or Revel hasn't made a home theater line of CBT speakers? Based on your comments and others, a well designed CBT should make an excellent HT speaker. I realize that JBL has a commercial CBT speaker (and may be the only one).

CBT loudspeakers: The decision to use or not use the design has been a marketing decision. In professional audio there are very good practical reasons for employing a design that can shape the wavefront to deliver uniformly good sound to a large distributed audience - coverage. Doug Button at JBL Pro has done some good innovative work on the new designs. Some elaborate home theaters and high-end cinemas have used these as side surround loudspeakers to allow more of the audience to experience "envelopment" - this is explained in Figure 16.8 and section 18.4.4 in my existing book. However, the advantage is less obvious in LCR locations in typical domestic rooms, and consumers have found happiness in well executed conventional designs.

I should mention that Rick Craig has said that they would work well for HT. I know he has designed some high end CBTs. Maybe he can give his thoughts in this thread.

 

[yourmando]

I found Floyd's reply to me from four years ago:




I should mention that Rick Craig has said that they would work well for HT. I know he has designed some high end CBTs. Maybe he can give his thoughts in this thread.

That‘s very helpful.

Indeed “the advantage is less obvious in LCR locations in typical domestic rooms” makes sense because the distance and coverage issues are not a huge issues as with surrounds.

In an ideal home setup, the good seats at reference angles from the screen and speakers puts you about 1/3 in from the back of the room, sitting very close to the surrounds and far from the LCRs.

There might be more to it, as well, because CBTs being less needed in LCR is a good reason, but there is also a benefit of having all identical speakers for perfect timbre matching. And usually it would be crazy expensive to have all speakers identical yet still able to hit reference SPL levels (crossed over to a bass array), but these are very affordable.

 

[amirm]

When these speakers came out, the marketing message was also for home theater use. I suspect though the market was way too small compared to outdoor use so it was not pursued. As for LCR use and Dr. Toole's response, there are much higher end speakers available for that use than these.

Another issue is the fact that these are JBL speakers. They are sold through pro channels at usually lower margins than Revels. As such, it is much harder for a Revel dealer to make a living on them.

The installations our company has made have been outdoor. As I noted in the review, the Seattle Wheel which is a major attraction here has ones we installed:

They are positioned above where people line up to get on the wheel. It is uncanny how you can get close or far from them yet the sound level doesn't change. It plays nice "background" music while you wait and never gets annoyingly loud.

We did build some custom, invisible subs to go with them to bring the low end.

 

[Bartl007]

As @jhaider and @Spocko mentioned, these speakers seem ideal for a surround setup. @Archaea’s matching surround setup must sound amazing. I believe he’s heard a great deal of the best speakers in dedicated home theaters across the country, and considers these CBT JBLs among the very best.

What I don’t understand is why these speakers are talked about or used more for dedicated home theater use???

They seem to solve the major problem where even in a large-ish home sized room (say 20x30’), you are left with a very small sweet spot of “good seats” with the middle couple of seats of 2 rows maybe.

With the latest object based audio formats with pin point sound locations, sound from every speaker needs to be heard from every seat. So the modern way of laying out speakers aims all the speakers toward the 1 “master seat” in the center, and all other seats have to be within the sweet spot of the speaker dispersion.

A wide a controlled dispersion solves this.

But also, any seats close to any speakers get that level too loud, so seats away from the very center get the double whammy of being off axis for some speakers and getting some speakers too loud and annoying in their ear.

The CBT design solves this too, with the 3b instead of 6db drop off with distance doubling.

Finally, these speakers are very efficient, so should be able to easily get to reference at every seat in a normal home.

Because directivity is well controlled, these are very EQ-able, and room correction plus something like @Maiky76’s speaker EQ for above transition would bring these up to a very accurate performance level.

I’m currently researching for my own dedicated home theater build, and it seems most common recommendations are JBL Synthesis, Triad, JTR, Procella etc.

It seems like this solves problems that none of the above do, and at a really goood price point of about $1k per speaker. There are some other high end line array designs for home theater from the likes of Widom Audi and Steinway, but prices are on another planet entirely.

Is there something I’m missing about trade offs for this JBL CBT? Why shouldn’t I consider these above all others mentioned above? It seems almost too good to be true!

Just an FYI the CBT50 (and other models) can be flush mounted right up to a wall surface with the optional accessory bracket attached. Also the CBT50 can be had new for a little less than 1/3 of the price point you mentioned if you shop around.

 

[Bjorn]

Toole doesn't say anything about not using CBT speakers in general as LRC. Why would he do that when a well designed ground plane CBT measures generally much more even placed in the room compared to the most expensive Harman's speakers and has lower distortion as well?

He talks specifically about the CBT 70J-1 and the CBT 1000 which are free standing CBTs and with some quite obvious weaknesses, which we also clearly seen in Amir's measurements of the CBT 70J-1. These do not avoid floor reflections, the on-axis response isn't great, there are diffraction issues, lobing of the 70-J-1 start fairly early in frequency, they don't offer much low frequency level and the horizontal directivity is quite uneven. In other words this type of CBT speaker simply has many disadvantages as a LRC speaker. However, this has nothing to with the CBT technology or CBT speakers in general. A CBT speaker can be deisgned in numerous ways.

Harman/JBL doesn't offer any ground plane CBTs which is the kind that makes sense to use as a LRC. Most likely they are not prioritizing it due to higher cost of both drivers and assembling or some other marketing reasons.

The best CBT surround speaker IMO would be one that is mounted against the ceiling and uses the ceiling as a mirror just like the ground plane version uses the floor as a mirror. That gives several acoustic advantages.

 

[richard12511]

I found Floyd's reply to me from four years ago:




I should mention that Rick Craig has said that they would work well for HT. I know he has designed some high end CBTs. Maybe he can give his thoughts in this thread.

So, he's essentially saying that CBT is still better for LCR, but the advantage is just smaller