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NHT Pro M-00 Powered Monitor Review

Krunok

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I think your intuition is correct, but in extreme cases a breakup from a woofer can be well past the crossover point and still high enough in amplitude to create a dip.

As I said, at 4kHz that woofer is at -20dB comparing to the tweeter so I really can't imagine a woofer breakup causing that dip, but anyway, the real issue was (is) incorrect calculation of Early reflection DI in Klippel SW.
 
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Krunok

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Distortion matters a great deal of course. It determines SPL capability, how loud you can play the speakers without the sound falling apart.
The JBL LSR3-5p mkII don't go very loud for instance before distortion becomes well audible, and don't go very loud beyond that point before they fall apart completely.
And IMD is a particularly audible form of distortion which does not always go hand in hand with harmonic distortion with different drivers like it mostly does with for instance DACs.

As for box resonances and some other issues and waterfall plots. A waterfall plot will allow you to identify non-minimal phase issues that you can't differentiate based on the frequency response as it has no time information. The audibility can be much larger for such issues and they can't be EQ-ed out unlike a minimal phase driver response issue.

If you are going to continue to post on speakers topic I strongly suggest you at least read Toole's book otherwise your posts will look like spam.

Once again, for all of you who missed it, here is a summary of 2 pages that he wrote in 500 pages book about the distortion:

"In loudspeakers it is fortunate that distortion is something that normally
does not become obvious until devices are driven close to or into some limiting
condition. In large-venue professional devices, this is a situation that can occur
frequently. In the general population of consumer loudspeakers, it has been very
rare for distortion to be identifi ed as a factor in the overall subjective ratings.
This is not because distortion is not there or is not measurable, but it is low
enough that it is not an obvious factor in judgments of sound quality at normal
foreground listening levels."

And one more thing: waterfall plot will not help you identify non-minimal phase issues - it will help you identify room resonances.
More info in REW help: https://www.roomeqwizard.com/help/help_en-GB/html/graph_waterfall.html
 

Dogen

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Great work Amir...this new direction is very exciting. Might I suggest including a very short text paragraph in the conclusions summarizing each the measurement of each review in plain language? For instance, excess of treble, poor linearity and narrow dispersion (just as an example). It will give each review something easily quotable, and a way for non-technical readers to get the bottom line?

Again, very nice work, and I look forward to future reviews.
 

q3cpma

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Thanks for this, didn't know about this model, but I'll still play the mean ingrate and say that CSD is needed to know if you monitor rings like a bell or comes with a free church organ.
 

JustIntonation

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As I said, at 4kHz that woofer is at -20dB comparing to the tweeter so I really can't imagine a woofer breakup causing that dip, but anyway, the real issue was (is) incorrect calculation of Early reflection DI in Klippel SW.
A woofer breakup can indeed cause that dip. A woofer breakup can give huge peaks and 20dB would not be uncommon in metal drivers though it seems a bit much for this driver substantial peaks can occur and are usually seen around that freq for this size driver. If such a peak is out of phase then it can cause such a dip.
 

folzag

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RE: You wife's subjective response, which I loved by the way

Knowing how sensitive we are to volume -- moar SPL, moar better -- were you leveling matching input signal or SPL?

I'm thinking if one can adjust toe so the listener is getting the flatter off-axis curve (ie. the one w/o the suck-out), and then increase signal so as to level match *SPL*, would there still be a subjective listener preference?

It seems like there might be a situation, esp w/ monitors, where they were designed for a specific listening angle-axis and if you're not listening at that angle, you are not getting the sound the designers intended. This could really bias the results.

Thank you.
 

JustIntonation

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If you are going to continue to post on speakers topic I strongly suggest you at least read Toole's book otherwise your posts will look like spam.

Once again, for all of you who missed it, here is a summary of 2 pages that he wrote in 500 pages book about the distortion:

"In loudspeakers it is fortunate that distortion is something that normally
does not become obvious until devices are driven close to or into some limiting
condition. In large-venue professional devices, this is a situation that can occur
frequently. In the general population of consumer loudspeakers, it has been very
rare for distortion to be identifi ed as a factor in the overall subjective ratings.
This is not because distortion is not there or is not measurable, but it is low
enough that it is not an obvious factor in judgments of sound quality at normal
foreground listening levels."

And one more thing: waterfall plot will not help you identify non-minimal phase issues - it will help you identify room resonances.
More info in REW help: https://www.roomeqwizard.com/help/help_en-GB/html/graph_waterfall.html
My posts will look like spam? Please behave yourself, I'm not interested in such nonsense.
And I'm well aware of Toole's writings and he talks about the general public in the 80's or so. I think in this day and on a forum such a this a very different subjective finding of audibility and influence of distortion will be found.
On top of that I specifically mentioned max SPL being related to distortion.
Please have your cup of coffee or whatever is causing your bad mood..
 
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amirm

amirm

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Btw, as bass suck out from 200 to 900Hz exists in all 3 (4) curves would you say it can be corrected via EQ? Following that logic dip at 4kHz seems more problematic..
Looks like a bug. From start I have been wondering why the Early Window DI looked so smooth but couldn't put the finger on it until you pointed this out. I have submitted a bug to Klippel. Given the time difference, it will take a couple of days to get some feedback on it.
 

napilopez

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Distortion matters a great deal of course. It determines SPL capability, how loud you can play the speakers without the sound falling apart.
The JBL LSR3-5p mkII don't go very loud for instance before distortion becomes well audible, and don't go very loud beyond that point before they fall apart completely.
And IMD is a particularly audible form of distortion which does not always go hand in hand with harmonic distortion with different drivers like it mostly does with for instance DACs.

As for box resonances and some other issues and waterfall plots. A waterfall plot will allow you to identify non-minimal phase issues that you can't differentiate based on the frequency response as it has no time information. The audibility can be much larger for such issues and they can't be EQ-ed out unlike a minimal phase driver response issue.

Oh I definitely agree about the utility of SPL limits information, mainly when it comes to compression/SPL limiting for active speakers. And certainly, if distortion rises to crazy high levels it can be an issue.

As for resonances... loudspeakers behave as minimum-phase devices though. When would they show non-minimum phase issues? Genuinely asking, I'm here to learn. Maybe I'm misunderstanding. From section 5.8 of Toole's book:

"The persistence of a bump in the spatially averaged curves [of the spinorama] is confirmation. There is no need to look at a waterfall diagram, because if there is a resonant peak, there will be ringing; no peak, no ringing. As was reported in Toole and Olive (1988) and discussed here in Section 4.6, it is the spectral bump that is the most reliable indicator of audibility. Loudspeaker transducers behave as minimum-phase devices, and therefore resonances in them can be attenuated by (minimum-phase) parametric equalization in the electronic signal path. Done correctly, the amplitude and phase response of the loudspeaker is corrected: the resonant peak is reduced, as is the time-domain misbehavior."

My posts will look like spam? Please behave yourself, I'm not interested in such nonsense.
And I'm well aware of Toole's writings and he talks about the general public in the 80's or so. I think in this day and on a forum such a this a very different subjective finding of audibility and influence of distortion will be found.
On top of that I specifically mentioned max SPL being related to distortion.
Please have your cup of coffee or whatever is causing your bad mood..

Toole's book is replete with citations though and many studies there were certainly made after the 80s. Distortion is important, especially as it related to SPL limits as you noted. Just again, a matter of what's worth the time investment. From Olive's seminal paper coming up with the generalized equation for predicting loudspeaker preference:

"The effects of nonlinear distortion on preference are not factored into our model. Listeners did not report
nonlinear distortion as factoring into their preference ratings, except in the one or two cases reported in Part One. In other large loudspeaker studies conducted by Toole [12]-[13] and Klippel [14] both authors concluded that nearly all of the variance in listener sound quality ratings can be explained by frequency response. Still, nonlinear distortion can be a factor and should not be ignored."


I'm pretty sure there's research to suggest that audiophiles aren't all that much better at picking out good sound than regular listeners, though don't quote me on that and I don't know if that applies to distortion. Also note that by audiophiles I mean the audio enthusiasts that comprise this forum as opposed to trained listeners who've actually taken training to point out these issues.
 
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amirm

amirm

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RE: You wife's subjective response, which I loved by the way

Knowing how sensitive we are to volume -- moar SPL, moar better -- were you leveling matching input signal or SPL?
It was listening level of course. These are active speakers so input matching is useless given the different gains. The difference was not sensitive to level though.
 

NTK

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@amirm I remember Dr Toole said that an important advantage of having a loudspeaker's anechoic measurement is that you can use the information to EQ the on-axis response to be flat.

Have you contemplated doing such an experiment and see how your NHT sound (subjectively) after EQ?
 
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amirm

amirm

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Thanks for this, didn't know about this model, but I'll still play the mean ingrate and say that CSD is needed to know if you monitor rings like a bell or comes with a free church organ.
It is very easy to show misleading CSD graphs. Setting the minimum level easily changes the look of it. The software generates them but whatever I post I like to be able to defend. Here is a snapshot of it for the NHT:

1578941284246.png


I should note that the NHT also buzzes at certain frequency during the sweep at pretty high levels. It is not loud as the JBL but it is clearly there in the back. I have not had time to play with it and find the frequency and correlation with CSD graph.

A somewhat related concern is if it makes the measurement fixture resonate. So far I have been able to verify that is not the case by lifting the speaker and seeing if the problem persists. But that is not a solution of course.

I may just have to measure the cabinet resonances differently using MEMS sensor that stereophile uses or similar.
 
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amirm

amirm

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@amirm I remember Dr Toole said that an important advantage of having a loudspeaker's anechoic measurement is that you can use the information to EQ the on-axis response to be flat.

Have you contemplated doing such an experiment and see how your NHT sound (subjectively) after EQ?
Yeh, the thought occurred to me but have had no time.

Note that what Dr. Toole says is that if the off-axis response is similar to on-axis, then you can do that. Otherwise the disparity between the two cannot be fixed by EQ. You would be adjusting both graphs at once, resulting in no gain. Practical experiments have shown limited success however even in this case.
 
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amirm

amirm

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On distortion, it plays a minor role between two different speakers sine linear differences in frequency response is often so large. That large difference sets preference scores. Now, if you have two identical speakers with same linear responses, the distortion may matter.
 

NTK

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Yeh, the thought occurred to me but have had no time.

Note that what Dr. Toole says is that if the off-axis response is similar to on-axis, then you can do that. Otherwise the disparity between the two cannot be fixed by EQ. You would be adjusting both graphs at once, resulting in no gain. Practical experiments have shown limited success however even in this case.
Thanks for the reply. Yes, I totally agree. The only fix for a speaker with poor directivity is to get a better speaker.
 

Krunok

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loudspeakers behave as minimum-phase devices though. When would they show non-minimum phase issues?

In a room. But you certainly wouldn't see it looking at waterfally graph as that one will show room resonances. Instead you would need to generate minimum phase from a sweep and display excess phase.
 

Krunok

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Looks like a bug. From start I have been wondering why the Early Window DI looked so smooth but couldn't put the finger on it until you pointed this out. I have submitted a bug to Klippel. Given the time difference, it will take a couple of days to get some feedback on it.

Yes, it looks like a bug. Let's wait and see what will they say..
 

MZKM

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It is very easy to show misleading CSD graphs. Setting the minimum level easily changes the look of it. The software generates them but whatever I post I like to be able to defend. Here is a snapshot of it for the NHT:

View attachment 45710

I should note that the NHT also buzzes at certain frequency during the sweep at pretty high levels. It is not loud as the JBL but it is clearly there in the back. I have not had time to play with it and find the frequency and correlation with CSD graph.

A somewhat related concern is if it makes the measurement fixture resonate. So far I have been able to verify that is not the case by lifting the speaker and seeing if the problem persists. But that is not a solution of course.

I may just have to measure the cabinet resonances differently using MEMS sensor that stereophile uses or similar.
It is possible to generate the CSD such that it is in reference to Time 0, meaning the it starts out completely flat; that way it is much easier to identify resonances and uneven decay.

The same could be said for showing off-axis graphs, much better at showing what can be EQ'd than actual SPL, though the Spinorama also shows that so no real need.
 

Krunok

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It is possible to generate the CSD such that it is in reference to Time 0, meaning the it starts out completely flat; that way it is much easier to identify resonances and uneven decay.

Resonances and/or uneven decay are either incorporated into magnitude graphs or they are not relevant.

The same could be said for showing off-axis graphs, much better at showing what can be EQ'd than actual SPL, though the Spinorama also shows that so no real need.

Exactly.
 

StevenEleven

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Awesome review--the first and second graphs told me everything I wanted to know about the objective data and the listening test write-up was interesting and well-done. A ton of progress in just one iteration.

I think if you start to get speakers that are pretty close in quality the listening tests will become more onerous and will need to be more rigorous to be helpful.

IMHO your wife is right--instruments from the performer's perspective (or a few feet away) are going to sound much brighter (more mid and upper treble). Just based on my personal experience. IME an acoustic guitar has way more bite to the performer than the listener.
 
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