3ll3d00d
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because it's intended as a guide to a layperson
you'll find the basis for this (with formulae) in https://www.pearl-hifi.com/06_Lit_A...apers/Keele_D_B/LF_Near-field_Measurement.pdf
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JBL 708i Monitor Review (Passive: Part 1)
- Thread starter amirm
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you'll find the basis for this (with formulae) in https://www.pearl-hifi.com/06_Lit_A...apers/Keele_D_B/LF_Near-field_Measurement.pdf
Well I have been checking, and KLH150 is not too far, though the JBL is superior in the low octaves. Though the Klh performance is overkill for me too...
I also checked that the JBL woofer has been designed with low power compression in mind, which for me is a no matter for concern at all for hifi use, as i have never warmed any voice coil more than a few degrees above room temperature...
As said before, these JBL pro are more similar to PA stuff than hifi gear
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I am quite aware of that paper. What has got to do with Klippel measurement nor the need to adjust emitter outputs according to their size?
every kid who measured a vented speaker knows of the fact, but some pertain to bigger ideas. let him have his special universe.
I am surprised about the outrage: the resonance was already well documented in the 708p thread. Nothing new here, yet a 180 degrees vibe shift. interesting.
Can you explain why you disagree with the explanation provided to you?
Even if the microphones were placed at perfectly the exact distance from the port/woofer during measurement (they wont), the signficantly smaller port opening would have to let through the same amount of air that the woofer displaced but over a much reduced surface area.
There is no plausible scenario where an SPL adjustment of some sort is not needed. and your arguments don't seem to argue against the value needed for the adjustment but rather whether an adjustment is needed to begin with which doesn't make any sense.
Your premise is that Klippel measurements must be adjusted as per the driver or port area. They show this being done when measurements are split to two. Lower spectrum is measured at near-field (as Keele’s method) and higher spectrum at far-field (often at 1-2m using the MLSSA method) then both are stitched together with a level shift to match the levels. You seem to want the same to be done for Klippel’s measurements.
In short you do not believe that Klippel is measuring correctly.
Klippel system is not only based on peer reviewed and famous research by the man himself but is now considered the pinnacle of loudspeaker testing. Do you expect me to believe you just because someone wrote a white paper that offers no scientific proof.
They didn’t believe Galileo as what he explained was interpreted as against the Bible.
do not make it worse, people have experience that you do not have. @amirm’s near field measurements are not corrected for radiator size, this is apparent to anyone who has created a combined system response for a vented enclosure. The port is simply lower in level, trust me.
There seems to be some misunderstanding? Amir's Near-Field measurements are just sticking the microphone sensibly close to the driver that he's measuring. This is not a proprietary method by Klippel at all and there is no processing being done to these measurements.
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beagleman
Major Contributor
Not actually disagreeing with you, but Genelec is "Loved" here based on measurements mostly..........
The reality, I believe only a handful in here have actually used them or heard them playing music. Not saying that makes a huge difference, but.....
The only charts I had been seeing since @amirm purchased a Klippel system are like this one. Can you explain what you mean by "just sticking the microphone sensibly closed to the driver" please?
I don't think the 308p Mkii follows your analysis re chewed up mid response, but it does have some higher distortion at high SPL:
The only charts I had been seeing since @amirm purchased a Klippel system are like this one. Can you explain what you mean by "just sticking the microphone sensibly closed to the driver" please?
He moves the robotic microphone boom of the Klippel NFS ''manually'' and places it really close to what he is interested in measuring and takes a sine sweep. @amirm can further elaborate if he does anything in addition to that.
the Klippel just graphs the amplitude response of the measurement. Nothing any of us can't do at home with a calibrated microphone.
This increases signal to noise ratio and direct sound to reflections ratio significantly. but is completely useless when it comes to measuring the response with the baffle step or with any additional drivers.
I understand the mechanics as the chart title says it’s near-field response. I also know that as per Keele, near-field output must be adjusted to find the level at far-field. Are you saying that for some reason @amirm adjusts the levels for the drivers but not for the port?
However, that adjustment does not alter the shape of the response. Keele’s formula doesn’t use frequency. It only shifts the curve. As the argument on this particular speaker is port resonance, what will that level shift change?
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That's just it, the scl-4 is NOT designed to be active.
On the residential side, there is no formal recommendation or even a mention in the user manual that the scl-4 can be, or should be improved with “anechoic eq” filters.
On the Pro side, it's made very clear that without proper DSP, you are not listening to the speaker as it was designed (708i/M2).
In fact, I wasn't even able to PURCHASE the M2 speakers without getting on a 3 way conference call with Harman so that I could explain to them that I wasn't planning on hooking up the M2 to any old amplifier and that I already had on hand the necessary crown DSP amps.
I'm not sure why anyone who wants a high end theater should be required to spend $20,000 on a single component (AVR).
ROOSKIE
Major Contributor
This was not taken via Klippel. It is a manual near field measurement to get the basic idea of individual driver and port response.The only charts I had been seeing since @amirm purchased a Klippel system are like this one. Can you explain what you mean by "just sticking the microphone sensibly closed to the driver" please?
An old method used by many.
I will agree that it is not exactly correct in the way it appears to have been implimented(combined) here.
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I'm far from an expert on speaker design and digital signal processing, but it's my understanding that it is possible to shape more than just frequency response with modern DSP (not just simple PEQ). They are indeed the same speaker though.
Not exactly. people are saying that Amir does not adjust the levels at all (which is fine, the far-field response is what matters and we have that in full resolution) and as a result the ratio of driver output to resonance in these graphs may not be perfectly representative.
The near-field chart is shown for analysing individual driver & part responses only. There’s no summation offered, hence no level error exists. What is it that people are asking for adjustment?
The level error is inherent to the measurement technique, not to the summation.
Amir eyeballs it and makes the fc peak of every transducer equal. Which is just to make it more readable but that can be far off of the actual response in the far field.
The correct (but unnecessary tedious way) is to sum the response and apply baffle step correction and check how much the summed response differs from the Klippel NFS far-field response and adjust the levels accordingly.
Can you clarify this further please? According to Keele the far-field response needs to be adjusted as per the emitter's size. If you are not going to sum multiple editors why do you have to adjust the levels? You are only looking at the FR of the emitter not its efficiency hence the SPL level is irrelevant. Unless I am missing something what @amirm does is just cosmetic. He just presents the curves roughly where they will be.
Hence, the question why bother with the levels?
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