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JBL 705P / 708P

Olli

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I would base any such reverse engineering or modification on anechoic or quasi-anechoic (gated) measurements taken over at least 90 degrees horizontal (on axis to perpendicular) at at least 10 degree intervals. A system such as Dirac that uses listening position measurements is not well suited to the task. I am not familiar with Audiolense or Acourate. Unless they use standard anechoic or quasi-anechoic measurements, the same caveat applies.
What‘s wrong with listening position measurements?

Mitchco did achieve excellent results with another JBL speaker using Audiolense:
https://www.computeraudiophile.com/...nd-room-correction-software-walkthrough-r682/
 

Bjorn

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What‘s wrong with listening position measurements?

Mitchco did achieve excellent results with another JBL speaker using Audiolense:
https://www.computeraudiophile.com/...nd-room-correction-software-walkthrough-r682/
Problem is that the sound in a room is not minimum phase behavior, meaning phase and magnitude does not correlate. Thus EQing such a response doesn't work well. While the frequency response may look impressive after such a correction, the phase will not follow and the result of that is weird and unnatural sound.
You can EQ the speaker (to a large degree) but not the room. So you need to measure the speaker without room interference.
 
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Sausalitoaudio measured the 708p speakers and has the results here.

Notable results (actually from this document, but speaker 'B' is the 708p):

About Axial response: "This highly regarded studio monitor, has an excellent, if not perfect, axial response. Everything above 1500Hz is shelved up 1dB. This is clearly audible."

About ER curve: "The studio monitor early reflection curve shows that the energy that hits the side walls of the room has the same spectral content as the direct sound. The family of curves developing here ALWAYS corresponds with higher preference scores in blind listening trials."

About DI curve: "Once again, this is excellent performance. The DI rises to 8dB and stays there. The early reflections DI shows that the speaker puts a remarkably consistent spectrum of sound toward the side walls. Good sounding speakers have Spinorama charts that look similar to this.
 

Jaimo

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Thanks for posting the links. I am about to pull the trigger on a pair of 708P's
 

Bjorn

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Sausalitoaudio measured the 708p speakers and has the results here.

Notable results (actually from this document, but speaker 'B' is the 708p):

About Axial response: "This highly regarded studio monitor, has an excellent, if not perfect, axial response. Everything above 1500Hz is shelved up 1dB. This is clearly audible."

About ER curve: "The studio monitor early reflection curve shows that the energy that hits the side walls of the room has the same spectral content as the direct sound. The family of curves developing here ALWAYS corresponds with higher preference scores in blind listening trials."

About DI curve: "Once again, this is excellent performance. The DI rises to 8dB and stays there. The early reflections DI shows that the speaker puts a remarkably consistent spectrum of sound toward the side walls. Good sounding speakers have Spinorama charts that look similar to this.
When did a speaker with a collapsing polar and serious vertical phase issues with lobing become "excellent performance" and yields a "consistent spectrum"? What a joke!
 
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@Bjorn -- I don't think its a joke, I think it a question of design decision and making assumptions about how these studio monitors will be placed and how the listener will consume the sound. They prioritized what Toole et al. had determined in listening tests to be the biggest levers they can pull when designing a monitor, namely:

1) A flat axial response.
2) "Good" behavior off-axis.
3) ER, On-Axis and Listening window spectral shape similarity.

...and some other things. Also, I suspect they expect the listeners of these monitors will largely be in one plane (not getting up an down).

It's regrettable that the article did not pay more attention to this. I'd love to see some additional research where vertical phase issues/lobing can be related to subjective preference of a loudspeaker.

At the end of the day, there is only so much you can do with a two-way. I'd love to see a similar measurement with the 705p. I think the 5" midbass would do a little better job up to the XO frequency and if you cross them over to a sub, I'd suspect similar performance (albeit with slightly less max output).
 

Bjorn

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1) A flat axial response.
2) "Good" behavior off-axis.
3) ER, On-Axis and Listening window spectral shape similarity.
Which it doesn't have. Neither horizontally or vertically.
It's a classic collapsing response. It's not a constant directivity speaker.
 

andreasmaaan

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Which it doesn't have. Neither horizontally or vertically.
It's a classic collapsing response. It's not a constant directivity speaker.
Which speaker would you nominate as having close to ideal/desired performance (forget for present purposes nonlinear distortion, I’m interested in polar response and to a lesser extent phase)?
 

Bjorn

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Which speaker would you nominate as having close to ideal/desired performance (forget for present purposes nonlinear distortion, I’m interested in polar response and to a lesser extent phase)?
Take note that I'm actually selling both the JBL speakers mentioned here and other JBL speakers. And while I think they a decent design and much better than a lot of expensive hifi speakers (which are often poor designs), I don't believe in misguiding people which the text from that review did. They have obvious weaknesses, and which are very evident when comparing directly to better designs.

When it comes to your question I think I will refrain from answering due to the fact that I'm involved in designing and developing speakers.
 

andreasmaaan

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Take note that I'm actually selling both the JBL speakers mentioned here and other JBL speakers. And while I think they a decent design and much better than a lot of expensive hifi speakers (which are often poor designs), I don't believe in misguiding people which the text from that review did. They have obvious weaknesses, and which are very evident when comparing directly to better designs.

When it comes to your question I think I will refrain from answering due to the fact that I'm involved in designing and developing speakers.
Perhaps then without naming a specific speaker you could describe what attributes you aim for in a speaker? I think your criticisms of the JBL would be given better context with reference to an (achievable) ideal to aim for.
 

dreite

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When it comes to your question I think I will refrain from answering due to the fact that I'm involved in designing and developing speakers.
Maybe I've missed it, but JBL makes no claims for "constant directivity" with these 700 series speakers.
And the Sausalito Audio measurements do not exhibit this characteristic anyways. In fact they specifically mention the varying Directivity Index.

You seem to be wound up about something, but I'm not sure what it is.

Dave.
 

Wombat

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Take note that I'm actually selling both the JBL speakers mentioned here and other JBL speakers. And while I think they a decent design and much better than a lot of expensive hifi speakers (which are often poor designs), I don't believe in misguiding people which the text from that review did. They have obvious weaknesses, and which are very evident when comparing directly to better designs.

When it comes to your question I think I will refrain from answering due to the fact that I'm involved in designing and developing speakers.
I am interested in what your stated involvement is in designing and developing speakers?
 

Bjorn

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I have already answered this. Bottom line is that the claims are largely incorrect, which the measurements of the speaker clearly shows. The speaker has a classic collapsing polar, making the claims untrue. This is misleading information IMO.
About Axial response: "This highly regarded studio monitor, has an excellent, if not perfect, axial response. Everything above 1500Hz is shelved up 1dB. This is clearly audible."

About ER curve: "The studio monitor early reflection curve shows that the energy that hits the side walls of the room has the same spectral content as the direct sound. The family of curves developing here ALWAYS corresponds with higher preference scores in blind listening trials."

About DI curve: "Once again, this is excellent performance. The DI rises to 8dB and stays there. The early reflections DI shows that the speaker puts a remarkably consistent spectrum of sound toward the side walls. Good sounding speakers have Spinorama charts that look similar to this.
 

Bjorn

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Perhaps then without naming a specific speaker you could describe what attributes you aim for in a speaker?
That can be heard, measured and judged when the speakers are released to the market besides the data we will provide.
 

mitchco

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Problem is that the sound in a room is not minimum phase behavior, meaning phase and magnitude does not correlate. Thus EQing such a response doesn't work well. While the frequency response may look impressive after such a correction, the phase will not follow and the result of that is weird and unnatural sound.
You can EQ the speaker (to a large degree) but not the room. So you need to measure the speaker without room interference.
Perhaps you can provide some clarification here....? Did you happen to notice the phase response is as good as the frequency response in the measurements provided in the article? Look's like ideal minimum phase response at the LP to me... I have had several excellent loudspeakers come through my room, (e.g. Kii THREE, D&D 8c), some use FIR filtering to correct for frequency and phase and some don't. I am comparing a pair of KEF LS50's to my JBL speakers that are eq''d with Audiolense, both in frequency and phase. Article forthcoming with binaural recordings of both speakers so folks can compare and can clearly hear there is no "weird or unnatural sound" from the eq'd speaker as compared to the LS50's with no eq.
 

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