JBL CBT 70JE-1 Review (CBT Bass Speaker)

[amirm]

This is a review and detailed measurements of the accessory bass module for the JBL CBT J70-1 that I just reviewed. It was kindly sent to me by the same member and costs US $594.

My sample is still sitting on the measurement gear so I thought I just show you the stock picture:

Note that the 70JE-1 mounts on top, not bottom. I am not sure how stable it will be as the 70J-1 did not want to sit by itself all that much. So likely you need to mount these to a wall or something. A bracket is provided to attach the two speakers together.

As you see the 70JE-1 only has the bass drivers and lacks the "J curve" of the 70J-1.

Since this is a bass module, I limited by scan to 8 kHz and used my usual 1000 point measurements. Error rate was well below 1% up to 2 kHz which is way past or frequency of interest. Measurement temperature was 60 degrees F.

JBL CBT 70JE-1 Measurements
Let's look at our usual spin data:

Hmmm. Bass response is quite peaky an uneven and different than what Harman shows in their brochure:

In-room response confirms my measurements to be correct as seen in distortion plots:

Distortion is low:

Here is the 70JE-1 response overlaid on top of the spin for the 70J-1:

As I am speculating on the graph, I wonder if the sum would then fill in the response below the peak resonance and give us something close to what Harman advertises?

Harman only speaks of beam forming in the context of combining the two modules and how it can go lower in frequency now. Here are my directivity plots:

Vertical response is sure narrow but not constant. Maybe it is in a narrow margin of 500 to 700 Hz? I plotted that in at a few points:

Looks like it is working. At 300 Hz and below there is next to no control though as you get an omni response (not shown).

Edit: here is the impedance:

Conclusions
It seems to me that 70JE-1 is more there to increase power delivery at lower frequencies than to provide much of any extension. After all, it uses the same four drivers. As it is, the baseline 70J-1 has excellent power capability. I am imagine with the addition of 70JE-1, you get incredible amount of loudness. I think the company advertises crazy numbers like 120 dBSPL!

No, I have not had time to listen to the stack. I don't want to go through the work of attaching them together. I didn't export the data either as I am not sure how useful that is to have for a bass module.

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

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[YSC]

it looks real bad... or just thinking, the Klippel is a nearfield robotic system, would it be not suitable to measure such a design with obviously a lot of controlling in directivity in action??? would love to see a single sweep measure with the stack in a more reasonable listening position to see if all that complex design did magic in real room environment.

P.S. that stack looks like me standing on one leg - extremely unstable

 

[beefkabob]

Bummer. I'd want to see how they work together.

 

[spacevector]

Did you measure impedance amirm?

 

[amirm]

would love to see a single sweep measure with the stack in a more reasonable listening position to see if all that complex design did magic in real room environment.

The distortion graph has a near-field measurement of that kind.

 

[amirm]

Did you measure impedance amirm?

I did. I will post it later.

 

[amirm]

I added the impedance graph.

 

[alanca3]

This speaker is also available as an EASE file.

Balloon

DI

On Axis

 

[YSC]

The distortion graph has a near-field measurement of that kind.

Interesting! That looks remarkably similar with the harman spec sheet!

If you remember me you likely remember I am always not too proud of harman products, while great their measurements usually to me shows less perfection than other big guys like the Neumann genelec dominance in here, resonances or so will appear as minor defects for most I recall. (No offence intended and in my mind you’re a bit preferential biased to favour harman stuffs given your close relationship with them, just as everyone of us do to our fav brand)

but this time around I have a feel that this type of “array” speakers will confuse the Klippel and results in way worse measurements than using in real life. Those measurements in distortion graphs looks remarkably better for this set than the anechoic measurements by Klippel. And I feel that for such designs with complicated interference control is not targeting anechoic chamber measurements as traditional speakers but tries to make great results in real rooms with wider SweetSpots

 

[mSpot]

that stack looks like me standing on one leg - extremely unstable

Of course they need to be properly mounted.

 

[Sancus]

Maybe for HT use you'd be better off skipping these and just using subs instead? I thought crossover at 140-160hz might cause bass to be localizable but with multiple subs perhaps that's not the case. At least others have tested and found it not to be an issue.

 

[amirm]

Interesting! That looks remarkably similar with the harman spec sheet!

Not really. You have to back off the room modes.

 

[Blumlein 88]

Are the pair too tall to measure together on the Klippel? It does appear to just mirror the rest of the speaker on the low end giving some headroom to that part of things. Seems a shame not to put them together and give a listen.

 

[Blumlein 88]

Maybe for HT use you'd be better off skipping these and just using subs instead? I thought crossover at 140-160hz might cause bass to be localizable but with multiple subs perhaps that's not the case. At least others have tested and found it not to be an issue.

Yeah, I was considering trying one of the smaller CBT50's as a center channel. Completely different beast really with all two inch drivers. But I'd think using it with subs to actually extend the low end would work better.

 

[amirm]

If you remember me you likely remember I am always not too proud of harman products, while great their measurements usually to me shows less perfection than other big guys like the Neumann genelec dominance in here, resonances or so will appear as minor defects for most I recall. (No offence intended and in my mind you’re a bit preferential biased to favour harman stuffs given your close relationship with them, just as everyone of us do to our fav brand)

I don't keep track of membership views so don't know where you come from. I can tell you are wrong about my favoritism of Harman products. I have given some of their products totally failing grade. And likes of Neumann and Genelec extremely high grades.

As for relationship with Harman, there is none. They have never loaned me one thing to test. And won't answer my questions about their measurements, etc. I used to have a relationship with them years ago but nothing is left of it since I started measuring speakers. Or they got bought by Samsung. Or both.

You are also comparing products that have little to do with each other. An active speaker with DSP can always produce a more perfect on-axis response than a passive one.

Really, all of this is uncalled for.

 

[Bruce Morgen]

Maybe for HT use you'd be better off skipping these and just using subs instead? I thought crossover at 140-160hz might cause bass to be localizable but with multiple subs perhaps that's not the case. At least others have tested and found it not to be an issue.

That was my intuition too -- a conventional active sub or subs would probably be a better solution for use in a home stereo or theater system than this product.

 

[Robbo99999]

Not impressive at all on it's own, but I suppose it synergises with the other module in terms of fitting in with the CBT technology......yes bass extension really quite poor.

 

[amirm]

but this time around I have a feel that this type of “array” speakers will confuse the Klippel and results in way worse measurements than using in real life. Those measurements in distortion graphs looks remarkably better for this set than the anechoic measurements by Klippel.

Well, you are wrong on both fronts. Here is Klippel's analysis of actual measurement (in-room) versus computed with and without reflection elimination:

In-room measurement is in red. In green is the computed field which is so close to the real one that obscures it fully. Elimination of room reflections results in the graph in solid blue. You can easily see that between 50 and 100 Hz, the response dips low and is not what Harman is showing.

As I have noted before, Harman's anechoic chamber is only so to 120 Hz. Below that they have been applying an equalization curve which I think has been too optimistic. Even with equalization, the shape, size of the speaker and measurement mic can invalidate it.

 

[amirm]

This speaker is also available as an EASE file.

I can also export to Ease. I have the GLL viewer but it doesn't do animations. Do you know how that animated gif was generated?

 

[YSC]

I don't keep track of membership views so don't know where you come from. I can tell you are wrong about my favoritism of Harman products. I have given some of their products totally failing grade. And likes of Neumann and Genelec extremely high grades.

As for relationship with Harman, there is none. They have never loaned me one thing to test. And won't answer my questions about their measurements, etc. I used to have a relationship with them years ago but nothing is left of it since I started measuring speakers. Or they got bought by Samsung. Or both.

You are also comparing products that have little to do with each other. An active speaker with DSP can always produce a more perfect on-axis response than a passive one.

Really, all of this is uncalled for.

Hi amirm, really no offence or accuse of somewhat as English is not my mother tongue so it might sound that way, I was trying to kind of mocking myself for some very early entry into the forum when seeing your disclaimer for Harmon stuffs.
And that this product really looks like it’s trying to deal with a very special use case, this with its unusual shape and the Klippel being robotic system with lots of assumptions in their Complex calculations I was curious about was that the case and would be interesting if contacting with Klippel is possible to discuss.
My apology again if the original post have made you any insulting feel