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JBL Stage A130 Review (speaker)

abdo123

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In case you didn't notice, I referenced the directivity index and the heat map.

the directivity index does not matter as much as you think it does, the early reflection directivity index (ERDI, dotted blue below DI) is much more important and it's fairly smooth as well. When you mentioned 'people sitting off-axis will experience different things' well that's where you're wrong because ERDI is smooth, and that's the measure used to reflect the consistency of the off-axis response.

The predicted in-room response is 12% Listening window, 44% Early reflections, and 44% Sound power/ Power response. So a little bit messy DI is almost insignificant when ERDI is fairly smooth.
 

John Atkinson

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Thanks again. Is your film device something like the cheap MEAS ones (I think I have a few of those somewhere). Did you make some sort of preamp for it?
View attachment 136204
It's similar. It is a strip of PVDF tape, like a piezoelectric acoustic guitar pickup. I made a preamplifier with a high input impedance for it, using op-amps and two 9V batteries.

John Atkinson
Technical Editor, Stereophile
 

pjug

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It's similar. It is a strip of PVDF tape, like a piezoelectric acoustic guitar pickup. I made a preamplifier with a high input impedance for it, using op-amps and two 9V batteries.

John Atkinson
Technical Editor, Stereophile

Thanks!

In case anyone else is interested, I just came across this really great document on piezo films:
https://www.imagesco.com/sensors/piezofilm.pdf
 

thewas

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the directivity index does not matter as much as you think it does, the early reflection directivity index (ERDI, dotted blue below DI) is much more important and it's fairly smooth as well. When you mentioned 'people sitting off-axis will experience different things' well that's where you're wrong because ERDI is smooth, and that's the measure used to reflect the consistency of the off-axis response.

The predicted in-room response is 12% Listening window, 44% Early reflections, and 44% Sound power/ Power response. So a little bit messy DI is almost insignificant when ERDI is fairly smooth.
DI is "responsible" for the 44% sound power so I wouldn't call it almost insignificant, also above weighting factors are for a specific set of assumptions, if listened closer and/or in a less reflective room the LW and ER weights increase while at higher listening distances and/or more reverberant room SP weight is larger.
 

Chromatischism

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the directivity index does not matter as much as you think it does, the early reflection directivity index (ERDI, dotted blue below DI) is much more important and it's fairly smooth as well. When you mentioned 'people sitting off-axis will experience different things' well that's where you're wrong because ERDI is smooth, and that's the measure used to reflect the consistency of the off-axis response.

The predicted in-room response is 12% Listening window, 44% Early reflections, and 44% Sound power/ Power response. So a little bit messy DI is almost insignificant when ERDI is fairly smooth.
Maybe you don't think performance in the range of 9-13 kHz matters, but that is where the directivity sharply narrows. Below that of course it is very good for a cheap speaker. In summary though, the DI heatmap looks very strange for a waveguided tweeter. Content will sound less "airy" to off-axis listeners due to that kink. That is what I am talking about. To my original point, there are speakers that do better in that regard and even measured better overall that didn't get a recommendation. Perhaps this is something that Amir isn't likely to hear due to the way he listens.
 

abdo123

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Maybe you don't think performance in the range of 9-13 kHz matters, but that is where the directivity sharply narrows.

beaking (like a bird's beak) is a very very common phenomenon in Speakers. As long as it starts above 10KHz usually that's a passing grade for the majority of deisgns that don't claim perfection.
 

abdo123

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DI is "responsible" for the 44% sound power so I wouldn't call it almost insignificant, also above weighting factors are for a specific set of assumptions, if listened closer and/or in a less reflective room the LW and ER weights increase while at higher listening distances and/or more reverberant room SP weight is larger.

well the 'messy' DI of the A130 seems to give an almost perfect PIR (in the messy region). So I'm going to ask you for further clarification or evidence as it seems that your statments are not entirely true/accurate.
 

thewas

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well the 'messy' DI of the A130 seems to give an almost perfect PIR (in the messy region). So I'm going to ask you for further clarification or evidence as it seems that your statments are not entirely true/accurate.
DI index is per definition the difference of direct sound vs the sound power (so the response in all directions) and as known the sound power dominates more to the direct sound when the distance gets higher and/or the room more reflective.

For the example you mention, it exactly proves what I say, namely the PIR of the A130 at the "messy" mid region where the on-axis sound has a bump is smoother than its direct sound because exactly the directivity has also a bump there so it partially compensates the bump making the sound power less bumpy.
 

abdo123

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DI index is per definition the difference of direct sound vs the sound power (so the response in all directions) and as known the sound power dominates more to the direct sound when the distance gets higher and/or the room more reflective.

For the example you mention, it exactly proves what I say, namely the PIR of the A130 at the "messy" mid region where the on-axis sound has a bump is smoother than its direct sound because exactly the directivity has also a bump there so it partially compensates the bump making the sound power less bumpy.

I think it's important to keep in mind that Sound Power is not really relevant in the majority of rooms above 1-2KHz and that Direct sound and reflections take over.

1624012153285.png


So for that particular range, the DI is almost meaningless and ERDI is much more prominent.
 

thewas

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I think it's important to keep in mind that Sound Power is not really relevant in the majority of rooms above 1-2KHz and that Direct sound and reflections take over.

View attachment 136307

So for that particular range, the DI is almost meaningless and ERDI is much more prominent.

Nope, as you even quoted correctly the Olive metric
The predicted in-room response is 12% Listening window, 44% Early reflections, and 44% Sound power/ Power response. So a little bit messy DI is almost insignificant when ERDI is fairly smooth.

is 44% sound power for which the DI is responsible which is the same much as the 44% early reflections/ERDI and not insignificant at all. At higher distances and/or more reflective rooms those 44% of the sound power even rise!

Of course this Olive metric is just an averaging numeric approach and for the perceived tonality at higher frequencies rather the direct sound is responsible so those are all only numerical approximations but saying that the sound power is not relevant while posting the Toole metric is a contradiction in itself.
 

abdo123

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Nope, as you even quoted correctly the Olive metric


is 44% sound power for which the DI is responsible which is the same much as the 44% early reflections/ERDI and not insignificant at all. At higher distances and/or more reflective rooms those 44% of the sound power even rise!

I don't think these percentages remain constant throughout the entire Frequency range.

Both PIR and IR measurements show the A130 to be completely flat above 1KHz.

I'm not that experienced to further continue this discussion, but all the evidence show that the A130 is flat in spite of the messy DI at that region so it's fair to assume that messy DI in that region is not a concern for this speaker.
 

thewas

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I don't think these percentages remain constant throughout the entire Frequency range.
Of course not, as I said this is an average numerical experimental approximation, in reality at higher frequencies the direct sound dominates more our perception.

Both PIR and IR measurements show the A130 to be completely flat above 1KHz.
Not really, the approximately 3 dB 800-2000 Hz mid bump is still there

1624021066268.png


I'm not that experienced to further continue this discussion, but all the evidence show that the A130 is flat in spite of the messy DI at that region so it's fair to assume that messy DI in that region is not a concern for this speaker.
As I wrote above the DI bump partially even compensates the on-axis bump, but saying that the DI does not play a role when even in the Toole formula it contributes 44% is not true.
 

thewas

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You seem to be a little bit confused here, the discussion you joined is about the 'terrible' Directivity the speaker exhibits above 2KHz, the directivity is quite sublime up to 2KHz.
I never wrote anything about "terrible" directivity, just joined when you claimed that the DI plays no significant role in the PIR which is clearly wrong.
And no, the directivity has its biggest audible problem at its 1-2 kHz mid bump, the 10 kHz bump has by far not such a significance in practice.

Also please stop getting personal "You seem to be a little bit confused here" as it doesn't bring anything constructive to the discssion and its quite obvious who was understanding deficits in this topic.
 

abdo123

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Also please stop getting personal "You seem to be a little bit confused here" as it doesn't bring anything constructive to the discssion and its quite obvious who was understanding deficits in this topic.

this entire discussion you're picking things i said and criticize them out of context.

Here I am clearly saying that PIR is smooth inspite of DI being messy in reference to the region between 2KHz and 10KHz, which was the topic of discussion.

all the evidence show that the A130 is flat in spite of the messy DI at that region so it's fair to assume that messy DI in that region is not a concern for this speaker.

However, you preceded to bring the region where PIR is messy and DI is smooth? Why? this is not the context of this discussion.

Not really, the approximately 3 dB 800-2000 Hz mid bump is still there
.

Then you get all mad and take it personally for saying you're a little bit confused ?

I'm sorry what?
 

thewas

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Here I am clearly saying that PIR is smooth inspite of DI being messy in reference to the region between 2KHz and 10KHz, which was the topic of discussion.
Nope, you wrote that generally the DI plays no big role "the directivity index does not matter as much as you think it does" which is as shown wrong as in this case the DI bump even reduces the on-axis bump in the PIR.

By the way you write that the ERDI is much more important without noticing that is has almost the same curve like the DI (as in most usual loudspeakers) only with approximately half the amplitude:

1624023634100.png


However, you preceded to bring the region where PIR is messy and DI is smooth? Why? this is not the context of this discussion.
?? The mid region I talk about the DI is not smooth but has as said a bump.

I'm sorry what?
??
 

abdo123

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Nope, you wrote that generally the DI plays no big role "the directivity index does not matter as much as you think it does" which is as shown wrong as in this case the DI bump even reduces the on-axis bump in the PIR.

By the way you write that the ERDI is much more important without noticing that is has almost the same curve like the DI (as in most usual loudspeakers) only with approximately half the amplitude:

View attachment 136349


?? The mid region I talk about the DI is not smooth but has as said a bump.


??

I don't want to invest further in this, I'm sorry if I offended you in anyway, feel free to read the entire conversation, we're obviously talking about two different things.
 

Ralferator

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Maybe you don't think performance in the range of 9-13 kHz matters, but that is where the directivity sharply narrows. Below that of course it is very good for a cheap speaker. In summary though, the DI heatmap looks very strange for a waveguided tweeter. Content will sound less "airy" to off-axis listeners due to that kink. That is what I am talking about. To my original point, there are speakers that do better in that regard and even measured better overall that didn't get a recommendation. Perhaps this is something that Amir isn't likely to hear due to the way he listens.

Which speakers are you referring to?
 

375HP2482

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The predicted in-room response is 12% Listening window, 44% Early reflections, and 44% Sound power/ Power response. So a little bit messy DI is almost insignificant when ERDI is fairly smooth.
Those Olive numbers may be representative of a cohort of residential living rooms with abundant uncovered sheetrock.

In my room with my speakers, no way. Listening window dominates, as I'll wager it also does in most purpose-built rooms.

I have surrounds for late, not early, reflections.
 

abdo123

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Those Olive numbers may be representative of a cohort of residential living rooms with abundant uncovered sheetrock.

In my room with my speakers, no way. Listening window dominates, as I'll wager it also does in most purpose-built rooms.

I have surrounds for late, not early, reflections.

what are your speakers and what's the measured response?
 
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