Donation Help for JBL CBT 70J-1 Measurements

[pozz]

I recently posted in the wishlist thread about the JBL CBT 70J-1: https://jblpro.com/en/products/cbt-70j-1

@amirm has expressed interest in measuring the speaker has even published a case study on their use. Would anyone be interested in donating to make it happen? One is around $1k USD. The prospect is pretty exciting and I can give the initial $200 to get it started.

(JBL's pictures show slight differences in tweeter mounting, as seen above.)

It's an unusual speaker based on the constant beamwidth technology developed by Don Keele. JBL has a white paper on it, and I found two good lectures by Keele:

• (2015) Don Keele - Constant Beamwidth Transducer Loudspeaker Arrays (9-Part Playlist)
• (2017) Don Keele - Broadband Constant Directivity

It's a curved line source that uses power shading (or deliberate attenuation of drivers in the array) to counteract SPL changes and keep directivity even as you move from nearfield to farfield. This makes it ideal for commercial applications in live sound or reinforcement, and potentially excellent for good coverage at home (@Archaea posted postive impressions after buying this model for his home theatre). Needless to say, the complexity of the design will test the limits of the Klippel system and there is plenty of data for us to compare the results.

 

[pjug]

I will probably just do a general donation with a note to Amir that I'd support doing your idea. Question for @amirm just out of curiosity: what do you do with a single speaker like this or the recently reviewed Revel after the measurements are finished?

 

[pozz]

Thanks @pjug. I'm doing the same thing: general donation to ASR with a note attached.

 

[Archaea]

I could loan a brand new one to Amirm. I’d like it back though after the measurements are done as I have plans for it. It just so happens I bought three more new in box recently.

That offered, I think JBL has a LOT of first party measurements already on this. They even have a whiz bang calculator program available for it.

Look at all the white papers, data sheets, and various measurements on this speaker. JBL already threw the proverbial objectivity book at it. What more are you wanting to see? Or did you just want someone, not first party JBL, to objectively measure it?

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

 

[amirm]

Question for @amirm just out of curiosity: what do you do with a single speaker like this or the recently reviewed Revel after the measurements are finished?

I like to sell them and can get a matching one from Harman to go with them. I am discounting the F328Be fair bit since Harman gave me a discount to purchase it.

 

[amirm]

I could loan one. I’d like it back though after the measurements are done. I just bought three more new in box.

Oh, if you are in US, let's do that. Measuring it will be a challenge due to countless drivers firing at once. So we may not get usable data but it is worth trying.

 

[Archaea]

Oh, if you are in US, let's do that. Measuring it will be a challenge due to countless drivers firing at once. So we may not get usable data but it is worth trying.

PM sent. I live in the Kansas City, Missouri area.

 

[pozz]

Look at all the white papers, data sheets, and various measurements on this speaker. JBL already threw the proverbial objectivity book at it. What more are you wanting to see? Or did you just want someone, not first party JBL, to objectively measure it?

Few reasons, the main one being curiosity. Measuring it here lets us compare the results directly to our current database and test both the capabilities of the Klippel system and the spin presentation. JBL has also focused on advertising the CBT for commercial installations, but, really, the CBT array and its evidence-based design should get wider attention, especially for use in studios and at home.

 

[Valentin R]

 

[pozz]

View attachment 94338

Thanks Valentin. Where did you find this image?

 

[Valentin R]

It was a presentation on CBT series from JBL pro

 

[Archaea]

And they’re off!
Amirm will have them next Monday.

I opened the box and tested the new 70j-1 against my current 70j-1 center channel on a frequency sweep with Omnimic to make sure I was sending Amirm a nominal speaker. FR overlaid reasonably perfectly.
I only have one 70je-1, so I couldn’t validate that speaker against others, but it subjectively sounded fine in a short listening session (in tandem with a 70j-1) and was also purchased new, so should be good to go!

For question of consistency between speakers. I measured my original 13 (I purchased used on eBay) from the same speaker position with my Omnimic (sans subs) previously, and here is that comparison.


and specifically my L/C/R compared.

 

[pozz]

And they’re off!
Amirm will have them next Tuesday.

I opened the box and tested the new 70j-1 against my current 70j-1 center channel on a frequency sweep with Omnimic to make sure I was sending Amirm a nominal speaker. FR overlaid perfectly.
I only have one 70je-1, so I couldn’t validate that speaker against others, but it subjectively sounded fine in a short listening session (in tandem with a 70j-1) and was also purchased new, so should be good to go!

This is going to be very, very interesting.

Thanks so much @Archaea.

 

[richard12511]

And they’re off!
Amirm will have them next Monday.

I opened the box and tested the new 70j-1 against my current 70j-1 center channel on a frequency sweep with Omnimic to make sure I was sending Amirm a nominal speaker. FR overlaid reasonably perfectly.
I only have one 70je-1, so I couldn’t validate that speaker against others, but it subjectively sounded fine in a short listening session (in tandem with a 70j-1) and was also purchased new, so should be good to go!

For question of consistency between speakers. I measured my original 13 (I purchased used on eBay) from the same speaker position with my Omnimic (sans subs) previously, and here is that comparison.
View attachment 94539

and specifically my L/C/R compared.
View attachment 94540

Awesome! Thanks for sending them in. Really looking forward to this review, and I'm hoping it will serve as a good learning experience that will help us in later reviews.

 

[tifune]

And they’re off!
Amirm will have them next Monday.

Did you ever hear back by chance? Seems like @Valentin R 's screenshot is slightly more optimistic than what was published in the user guide (pg 5):

https://jblpro.com/en-US/site_elements/cbt-70j-1-spec-sheet

so very curious to see a 3rd party result

 

[Archaea]

Not yet. I know Amirm has them, I presume they are in his working backlog, and I understand they may be challenging to measure because of their design and tall form factor when mounted together as designed. I check the reviews page every day or two, but haven’t bugged him otherwise.
I see reviews churning out consistently so I know he’s working hard and steady.
I also sent in my tiny Creative Super X-Fi headphone amp, bundled in the instruction manual ziplock bag of one of the two speakers - I’m hoping he has time or interest to measure it as well.