A Little About JBL

[Stuart Polansky]

I wasn't aware of almost all of this. I know many in our club are fond of JBL speakers.

I hope this video is interesting and informative to you

https://youtu.be/oflI4KypXQI?si=hlgdd1M2ut8W-CV-

Stuart

[brombo]

I just got my first JBL speakers for my home theater. The JBL CBT 70J-1. Here is a review of it -

https://www.audiosciencereview.com/foru ... cer.21469/

[Cogito]

That looks like a 6' tall speaker with 15" woofers.

[Cogito]

But seriously, I question the design.

About 50% of the woofers surface area is blocked and reflected back to the cone. Looks like the reflections are aimed back at the cone.

[brombo]

Look at the review. The obscured speakers are 5" midranges. A subwoofer is required.

[cport]

But seriously, I question the design.

About 50% of the woofers surface area is blocked and reflected back to the cone. Looks like the reflections are aimed back at the cone.

If the “cut-over” for these drivers is below 150Hz, what is in front of the woofer is transparent and will only mildly effect the dispersion (very large and omnidirectional waveforms)- JBL has access to all the resources of Harman Corp, so this design (for sure) passed though an aechoic-chamber. Certainly a certified and engineered design.

[brombo]

Please just look at the review. The speakers were designed by Don Keele who wrote most of the book on speaker measurements ( https://en.wikipedia.org/wiki/D._B._Keele_Jr. )

https://www.audiosciencereview.com/foru ... cer.21469/

[tomp]

Don Keele inside speaker enclosure.jpg (30.74 KiB) Viewed 3981 times

Don Keele and I go back many years and he is certainly a very knowledgeable guy. In September 2017, he wrote an article in audioXpress called True Bass in a Large Space in response to an article I did in audioXpress called True Bass in a Small Space. If you get a chance you should read his article. It goes back to 1975 where while working at EV he built a 76 cu. ft. ported enclosure for the 30" EV woofer. I'm including a picture of Don and two other EV personnel actually inside the enclosure.

I think that when it comes to dynamic drivers, although Don is eminently capable as shown by among other things being awarded a technical Oscar for his work in theater sound, the preeminent expert is Wolfgang Klippel. He recently retired, but his work with drivers has set the standard for driver measurements. I did an article on his early Klippel system and DUMAX in audioXpress back in 2003. I also attended one of his seminars in Dresden. I have been fortunate to have known some experts in drivers and complete systems over the years and have learned much. We re lucky to have such competent people in the speaker field.

[Cogito]

But seriously, I question the design.

About 50% of the woofers surface area is blocked and reflected back to the cone. Looks like the reflections are aimed back at the cone.

If the “cut-over” for these drivers is below 150Hz, what is in front of the woofer is transparent and will only mildly effect the dispersion (very large and omnidirectional waveforms)- JBL has access to all the resources of Harman Corp, so this design (for sure) passed though an aechoic-chamber. Certainly a certified and engineered design.

I am not talking about dispersion, reflections are the issue.
The concave metal baffle is merely couple of inches away form the cone. Reflected sound pressure would hit the cone negatively impacting its movement.

There is a reason why we do not see baffles blocking the cones in high-end speakers.

[Cogito]

Please just look at the review. The speakers were designed by Don Keele who wrote most of the book on speaker measurements ( https://en.wikipedia.org/wiki/D._B._Keele_Jr. )

https://www.audiosciencereview.com/foru ... cer.21469/

Keele might have designed these speakers, but without information on the design criteria he was working with, one cannot make any judgements. Afterall, contemporary JBL is not a "high-end" company anymore. They are competing in low-end mass-production speaker brands like Yamaha and Sony.