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JBL 705P / 708P

Olli

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A question about the 705/708 i (the passive version): Is there a passive XO inside or are the XO settings applied by the coressponding external crown amps and there DSP settings?

Or in other words: Is the i version a nice basis to apply external (r)eq settings via Audiolense, Acourate or Dirac when using MC DACs and amplification?
 

andreasmaaan

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“Near-field” is one of the most nebulous terms in audio IMHO. Probably a close second to “long-throw”.
 
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watchnerd

watchnerd

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A question about the 705/708 i (the passive version): Is there a passive XO inside or are the XO settings applied by the coressponding external crown amps and there DSP settings?

Or in other words: Is the i version a nice basis to apply external (r)eq settings via Audiolense, Acourate or Dirac when using MC DACs and amplification?

External XO.
 

FrantzM

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They'll start to follow normal (far-field) acoustic propagation characteristics and drop off (roughly) the same, depending upon the speaker's dispersion characteristics, natch. Before being impacted by boundary reflections leading to room mods and all that jazz.

Look guys (and gals or whatever), acoustics is not my day job, I just quoted what I "know" from previous experience and definitions I remember. As in my day job, when someone questions a basic principle, I try to provide an answer in those terms, be it audio, RF, or whatever. That is why I found and quoted the IEC. Heaven knows the industry (any field of industry) tends to develop their own definitions. Outside my field of so-called expertise I am not competent to comment nor debate. I'll leave that to the experts.

You are too modest. This attitude however, belies your (very high) level of Knowledge and Expertise. "The more you know ...."
 

jhaider

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A question about the 705/708 i (the passive version): Is there a passive XO inside or are the XO settings applied by the coressponding external crown amps and there DSP settings?

Yes.

To elaborate, there is a rudimentary passive crossover that performs some functions, and the filters in the Crown amp or BSS processor perform some functions. Otherwise, there would be no way to run the speaker off of one amplifier channel. I do not definitively know if any part of this crossover is in the circuit in biamp mode, though from a warranty claim reduction standpoint it makes sense for at least one pole of the tweeter crossover to be looped in.

Or in other words: Is the i version a nice basis to apply external (r)eq settings via Audiolense, Acourate or Dirac when using MC DACs and amplification?

Yes, it would be possible to reverse engineer the full crossover using a non-Crown solution, or engineer a whole new crossover with a different target curve with your processor of choice. I think it is more work than warranted, compared to just buying the right components to start with, or going with the powered version.

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.
 

andyc56

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A question about the 705/708 i (the passive version): Is there a passive XO inside or are the XO settings applied by the coressponding external crown amps and there DSP settings?

Or in other words: Is the i version a nice basis to apply external (r)eq settings via Audiolense, Acourate or Dirac when using MC DACs and amplification?

I've got a pair of the 708i. There is a passive crossover internal to them with a two-wire connection, and also a separate set of biamp terminals. The biamp terminals have three jumpers in addition to the four-wire terminals, and according to the documentation, when using these terminals properly, the internal crossover is bypassed so that real biamping (not just passive biamping) is accomplished using external amps.

705i/708i documentation said:
LSR705i and LSR708i Dividing Network can be bypassed for bi-amplified operation.

Edit 04/24/2019:
I just had a look at the filter configuration captured from the Harman Audio Architect software for biamped operation. In the low-pass section, it does show an active LR 24 dB/oct active filter, but there is no corresponding active high-pass section. This strongly suggests that in biamped configuration, the internal passive low-pass section is bypassed, but the internal passive high-pass section is not.
End edit

The parametric EQ settings for the 705i and 708i from the Harman Audio Architect software can be found here and here. These are a fixup of the anechoic response. I've converted the two-wire 708i EQ to the Equalizer APO format and posted the results here.
 
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jhaider

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The parametric EQ settings for the 705i and 708i from the Harman Audio Architect software can be found here and here

I have taken measurements of the tunings out of BSS BLU50. While I will not post out of respect for Harman IP, I will inform that those links are wrong or at least incomplete.

You can verify by measuring and comparing to the published spins.
 

andyc56

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I have taken measurements of the tunings out of BSS BLU50. While I will not post out of respect for Harman IP, I will inform that those links are wrong or at least incomplete.

They're taken straight from the Audio Architect software using the Crown amps. They are the two-wire settings.
gNAdEfS.png


Edit 04/25/2019: The screen capture pictured above reflects an incomplete set of filters, based on an apparent error by JBL/Harman. The revised filter coefficients linked in post 347 above are provided based on the 16-biquad filter set from the BSS BLU-50 device.
 
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jhaider

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They're taken straight from the Audio Architect software using the Crown amps. They are the two-wire settings.
View attachment 17309

And they are wrong. Do as I suggested (measure and compare to the published data) and you will see the obvious truth of my statements.
 

jhaider

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You haven't provided any evidence for your claim at all. You've only shifted the burden of proof.

I have no burden and need provide no proof. I provided accurate information as a courtesy and have already stated my grounds for not going beyond my chosen statements.

If you wish to uncritically accept suboptimal performance (especially up top) from your new speakers because you have faith in some magic screenshot, that is your choice. I don’t have to hear them! If you wish to attain most of the fidelity they can provide on the cheap, then do the measurements and try to sculpt the FR to match the published data. Or just buy the appropriate equipment and get all the fidelity JBL designed into them. A BLU50 is relatively cheap.
 

jtwrace

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As someone who owns JBL M2's, Crown DCI 4 1250N (for sale with M2 tuning loaded), BLU 50 programmed with the M2 Turning and who has owned the JBL 708P I'll say that there are some things in the tuning file that are hidden and proprietary to Harman. They purposely do not show all what's going on there. I learned quite a bit on my trip to Harman.
 
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watchnerd

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As someone who owns JBL M2's, Crown DCI 4 1250N (for sale with M2 tuning loaded), BLU 50 programmed with the M2 Turning and who has owned the JBL 708P I'll say that there are some things in the tuning file that are hidden and proprietary to Harman. They purposely do not show all what's going on there. I learned quite a bit on my trip to Harman.

Given the 708P is active and has the DSP built-in, I'm not sure what you're implying about that particular model.
 

FrantzM

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Not JW Trace.
Given the 708P is active and has the DSP built-in, I'm not sure what you're implying about that particular model.
That there is more to the settings than what is seen at first glance.
 
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watchnerd

watchnerd

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Not JW Trace.

That there is more to the settings than what is seen at first glance.

You've lost me....the active models, like the P, should be self-contained and used with any electronics, right? They don't require the use of Harman, or any other, external DSP profiles.
 

jtwrace

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Given the 708P is active and has the DSP built-in, I'm not sure what you're implying about that particular model.
My point was simply that there is a lot that is unknown unless you have the resource of Harman. Just measuring as we would doesn't tell the whole story.
 
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watchnerd

watchnerd

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My point was simply that there is a lot that is unknown unless you have the resource of Harman. Just measuring as we would doesn't tell the whole story.

Okay, but when you referring to a tuning file in the context of a 708P, what is that referring to?

It's all internal and inaccessible, as far as I know, in that model.
 

FrantzM

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W’ n

This is pertaining to the 7xx “I” version. They require external amp, EQ and x-over.
 
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watchnerd

watchnerd

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This is pertaining to the 7xx “I” version. They require external amp, EQ and x-over.

Okay, sorry, I got confused because @jwtrace said, "BLU 50 programmed with the M2 Turning and who has owned the JBL 708P".

I guess the 708P part was moot.
 
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