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

[dasdoing]

I wonder how hard it would be to create GLL files from the Klippel data

 

[ernestcarl]

to add to this. there is a software called GLL Viewer: https://www.afmg.eu/en/gll-viewer
it can create all kinds of graphs with the Ease File.

example:

View attachment 169859




even the resonance is in the data:

View attachment 169872


The HST speaker has a GLL file, too

Yes, that's the one I used. Unfortunately, haven't had time yet to play with it more.

 

[kyle_neuron]

I wonder how hard it would be to create GLL files from the Klippel data

You need a license for EASE and the accompanying SpeakerLab software to do so. It’s a fair few thousand dollars.

SOFA format has support for speakers or sources, including full balloon data. It’s open-source, but there’s no viewers or tools aimed at speaker data yet.

 

[Godataloss]

Seems like these are designed for boardrooms or conference spaces.

 

[jhaider]

Those HST's look perfect. Have you listened to them?

This is a speaker of similar design, though I'm sure some details differ:

Infinity RS152 Review (Surround Speaker)

This is a quick review and raw measurements of the Infinity RS152 surround speaker. It was kindly purchased new (last year!) and sent to me directly for testing. They current costs US $449 for a pair but Harman is know to have blow out discounts on these speakers at times. Edit: our company...

www.audiosciencereview.com

I think CBT50/100 on the optional flush mount brackets would be a better choice.

 

[dasdoing]

I would rotate the hst 90 degrees

hor

vert

 

[DubbyMcDubs]

This is a speaker of similar design, though I'm sure some details differ:

Infinity RS152 Review (Surround Speaker)

This is a quick review and raw measurements of the Infinity RS152 surround speaker. It was kindly purchased new (last year!) and sent to me directly for testing. They current costs US $449 for a pair but Harman is know to have blow out discounts on these speakers at times. Edit: our company...

www.audiosciencereview.com

I think CBT50/100 on the optional flush mount brackets would be a better choice.

Thanks for the link! I was looking at the rs152 as well but I have eliminated it and its coming down between the CBT and HST.

I have been going over the EASE, CLF and simulator tools and so far have come to the conclusion that the HST will be much easier to integrate into my room and has some nice advantages. I am continuing to play around with the modeling.

 

[kyle_neuron]

I would rotate the hst 90 degrees

hor

View attachment 170056

vert

View attachment 170057

Just a heads up, you have your polar maps the opposite way round to the way they’re normally presented, and the colour scale is so compacted that the plot doesn’t really tell us much. Hit Alt+Z twice more to rotate the plot so the HF is on the right, and you can edit the settings for the plot to get the colour scale approximately equivalent to the ones used by Amir. I think that’s a 30 dB range, with stepped colours every 3 dB, from memory.

 

[dasdoing]

Just a heads up, you have your polar maps the opposite way round to the way they’re normally presented, and the colour scale is so compacted that the plot doesn’t really tell us much. Hit Alt+Z twice more to rotate the plot so the HF is on the right, and you can edit the settings for the plot to get the colour scale approximately equivalent to the ones used by Amir. I think that’s a 30 dB range, with stepped colours every 3 dB, from memory.

I restricted it to 6dB on purpose. we should never look at any graph without reading the scales.
I get the idea of making a standard for comparison. but here I compared 2 graphs beween each other

 

[kyle_neuron]

Okay, you didn’t explain what that reason might be though so perhaps that’s why it looks a little odd. I presume you’re trying to really highlight the typical -6 dB directivity contour line?

I’d argue that a plot that is mostly ‘black’ lacks resolution regarding the off-axis behaviour, but each to their own

 

[dasdoing]

I’d argue that a plot that is mostly ‘black’ lacks resolution regarding the off-axis behaviour, but each to their own

personaly I find it easier to read in terms of where the output is usable (though I personaly would resctrict the range even more. 3dB diference is allready a lot).
it depends on what you are looking at. showing the 30dB is more usefull in terms of impact in the whole room (reflections).

 

[DubbyMcDubs]

This is a speaker of similar design, though I'm sure some details differ:

Infinity RS152 Review (Surround Speaker)

This is a quick review and raw measurements of the Infinity RS152 surround speaker. It was kindly purchased new (last year!) and sent to me directly for testing. They current costs US $449 for a pair but Harman is know to have blow out discounts on these speakers at times. Edit: our company...

www.audiosciencereview.com

I think CBT50/100 on the optional flush mount brackets would be a better choice.

After running some more examples in the simulator, the CBT 100LA looks like maybe the best of the CBT's for my room.

However, the HST option is a lot more consistent over the spectrum than the CBT's. So they are still on the table. Wish it wasnt so hard to get these things in Aus to audition!

 

[DubbyMcDubs]

Not that anybody cares, however I have made the ultimate decision to buy a set of both the JBL HST and Infinity RS152's to compare. Maybe one day I can get my hands on a set of CBT's and do a comparison.

 

[Head_Unit]

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.

I was just thinking that before I read your post. BUT, if the horizontal coverage is compressed, would that not be a negative if you were seated not so far back? Because it would (in ideal theory) beam over your head?

 

[Bjorn]

I was just thinking that before I read your post. BUT, if the horizontal coverage is compressed, would that not be a negative if you were seated not so far back? Because it would (in ideal theory) beam over your head?

What you mean by the horizontal coverage is "compressed"?
The horizontal directivity of a traditional CBT is 180°.

 

[Head_Unit]

What you mean by the horizontal coverage is "compressed"?
The horizontal directivity of a traditional CBT is 180°.

Oh dang I meant vertical! (And it's not perfectly compressed, I know).

 

[Bjorn]

Oh dang I meant vertical! (And it's not perfectly compressed, I know).

I see. That's not a problem if the speaker is aimed correctly. Take note that a vertical coverage of a CBT can easily be adjusted in many ways. But generally we want to avoid reflections from both the ceiling and the floor, as they dont' contribute to anything positive. So a narrow vertical directivity is beneficial and mounting in the ceiling with the opposite shading of a ground plane CBT will completely avoidance of ceiling reflections and the "ceiling bounce" (ha, new phrase!).

Take note this would not work in the same matter with a free standing CBT as the JBL. A ground plane CBT is really a much better design for hifi and home theater.

 

[Larry B. Larabee]

Here is a good description of CBT from earlier in the thread 'When listening to music, they give a very HUGE sound to them because they are huge! This is generaly a good thing but listening to a wall of solo flute is...odd.'
Others note similar reproduction characteristics. Now, used as surround speakers some have claimed nothing has ever come close to CBTs, this seems to infer that location for this type of speaker as a strictly stereo pair does not follow conventional use. A 'huge sound' and 'wall of solo flute' and being able to move anywhere in the room without the annoyance of localizations (because there are none to begin with) happens because what is being described is known as monophonic reproduction.

L

 

[Archaea]

YouTuber Youthman toured through Kansas City Home Theaters and and had a stop at my place to demo my thirteen JBL CBT 70j-1 line arrays in a 9.x.4 Dolby Atmos configuration.

His video tour of my room goes live today.

 

[Wright Sound]

@amirm The measured performance doesn't really correlate with your strong recommendation IMO.

Perhaps the novelty, unconventional design and the CBT 'magic' is influencing you? Based on your measurements, I wouldn't bother with these for anything other than a small exhibition or conference room, but certainly not in the home. What do you think?

There is no magic going on here. And I can tell you, based on actually seeing (and hearing) these turkeys in 2 different churches, they are remarkably ineffective. Short throw, inefficient, very beamy on the highs, disregarding the useless lack of bass. The real problem is that they are being marketed for churches and auditoriums, but have neither the directivity, pattern control, projection, or efficiency for those jobs. 93dB is not high efficiency. A typical pro speaker is 100dB or more sensitivity; a 7dB difference equals 5 times the power, so figure that out for yourself.
While they might be adequate for a conference room, or maybe your jazz trio at the coffee house, there’s much cheaper ways to do that. To reach the back of a room 60’ to 100’ long, requires long throw speakers with a narrow dispersion, like 40°, not a bunch of 1” tweeters. And the data AMIRM posted shows that JBL was lying, or at least misleading about the highly touted "constant beamwidth". Bottom line - they are not only inadequate, they are totally the wrong design for a sound system in a church or auditorium. Note: JBL's own guide suggests that more speakers might (probably) need to be added for coverage. Well ….. if I spend over a thousand dollars on a speaker, I certainly expect it to cover the whole room.
See photos of my designs that actually work.
P.S. Don’t get hung up on the slight advantage of cylindrical vs spherical, No loudspeaker radiates a spherical wave. A 12” or 15” speaker is about 90° conical. A horn will give a 20dB - 30dB advantage of loss per distance, not a mere 3dB. This is another topic fully worthy of a detailed discussion. Very many people have misunderstood this for a long time. Check these out for the 411: http://www.csgnetwork.com/speakerqestcalc.html http://www.mcsquared.com/Qcalc.htm