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Buchardt S400 Speaker Review

GelbeMusik

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I'm not sure ... but masking thresholds are well-researched and documented in the field of psychoacoustics (which fwiw I am not in). There's not a lot of mystery left.

So, the mystery to me is simply that us should rely on a hobbyists attempt to derive the said thresholds from somewhere else. With crude methods and lesser success, I assume, unverified, though.

Could You provide some of the reference, You cited above? It would help a lot, really.
 

andreasmaaan

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Nope, only at 90dB.
In the test field of the nine 6-6.5'' bass-midrange units, the SB17NBAC35-8 driver had the lowest harmonic distortion at 90dB in the said frequency range.

Yeh, that's where it excels.

FWIW, the bass distortion in the S400 is more or less what I would expect from this woofer. It has an exceptional midrange, but unexceptional (albeit decent for it's size/price) bass performance.

And at 96dB in 4pi space, it is at or possibly even just over Xmax in this enclosure at around 70Hz (and ofc way over Xmax below the passive radiator's tuning frequency).
 

andreasmaaan

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So, the mystery to me is simply that us should rely on a hobbyists attempt to derive the said thresholds from somewhere else. With crude methods and lesser success, I assume, unverified, though.

Could You provide some of the reference, You cited above? It would help a lot, really.

I'm afraid I don't have anything in soft copy. Zwicker and Fastl's Psychoacoustics goes into it in some detail. I can pm you some of the most illustrative graphs from it later if you like? (Not possible just at the moment)
 

QMuse

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@Juhazi, unless I am mistaken, I believe Buchardt is saying that this is a setting in the software, not that the physical mic in the real world has to be further. I mean, measuring at 2m isn't exactly nearfield and seems to somewhat negate the point of getting the NFS. Such a distance is never showed in Klippel's videos, and I'm not even sure the arm goes that far.

Is this correct @Mads Buchardt ?

True, 2m seems a bit too far for the arm. But 30cm also seems a little too close to handle rear port of a subwoofer, don't you think?
 

Juhazi

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About NFS, I don't know if the loudspeakers's (DUT's) dimensions, driver and port location geometrics are given to the software - obviously not. It just measures at two distances from the DUT around it and calculates. Response above say 500Hz seems to be pretty valid, but at lower freq (below baffle step) longer distace would be better. Large speakers with multiple drivers for bass and midrange or panels like Magnepans are very tricky to measure.

Anyway, be it anechoic chamber, quasi-anechoic with summed nearfield, ground plane 2m or NFS they all give different result/response at low freq. Just makes comparison difficult and stimulates my imagination... :cool:
 

napilopez

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About NFS, I don't know if the loudspeakers's (DUT's) dimensions, driver and port location geometrics are given to the software - obviously not. It just measures at two distances from the DUT around it and calculates. Response above say 500Hz seems to be pretty valid, but at lower freq (below baffle step) longer distace would be better. Large speakers with multiple drivers for bass and midrange or panels like Magnepans are very tricky to measure.

Anyway, be it anechoic chamber, quasi-anechoic with summed nearfield, ground plane 2m or NFS they all give different result/response at low freq. Just makes comparison difficult and stimulates my imagination... :cool:

I do not think the complexity of the device itself really matters, that's kind of the point of the NFS. It looks at the sound field, not what's emitting it. AFAIK the only thing you have to worry about with the Klippel is where the high frequency driver is to begin the field expansion and the dimensions of the unit so the microphone doesn't hit it during measurements.:)

Maybe there's some error or not in the bass. Like like you said, different sources give different results, and I've learned to mainly look for the rough contour of the bass rather than exact contours when comparing among sources. But what were discussing doesn't really have to do with that - Amir hasn't measured any particularly complex speakers. The discussion is whether given the data the klippel machine already has, can we adjust some parameters in the software to get a more relevant result.

When Mads said the data should be referenced to 2m, I don't think he was saying the speaker should be physically measured at 2m, just the expansion should be set to 2m in the software. But I'll await his response.
 
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hardisj

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The entire purpose of the NFS is that it physically measures in the nearfield, thus allowing it to remain reflection-free to a low enough wavelength that the data is not corrupted and thus allowing you to measure in a room and not need a huge anechoic chamber. It then uses holography to calculate soundfield expansion at whatever distance you tell it to. That is the NFS' bread and butter. There is all sorts of information on Klippel's site. Here's one for example: https://www.klippel.de/know-how/mea...n-and-propagation/near-field-measurement.html

For example, in this case Amir's spectrogram shows "r = .6614277 m" in the title. indicating the result shown is based on what the soundfield would look like at 0.66 meter. This was the issue Mads has with the result; that it's not in far-field equivalent. Whereas, if you look at the Kef R3 spectrogram measurement, the title shows "r=1 m", indicating the result shown is based on what the soundfield would look like at 1 meter. This matters especially for vented enclosures or multi-bass enclosures where the bass contributors will not have 'summed' correctly in the nearfield and you need to be in the farfield for them to do so. This is the exact reason why measuring in the nearfield can give inaccurate bass results.
 

NTK

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@amirm Does your Klippel NFS package include 2520-019? If it does, and if you are willing to share the data, I think we can devise some math tools and use the data to recreate "measurements" anywhere. That will help answer a lot of the questions raised in this thread and in the future.
https://www.klippel.de/fileadmin/kl...D_System/PDF/C8 Near Field Scanner System.pdf

NFS-Prices.PNG


NFS-01.PNG NFS-02.PNGNFS-02.PNG
 

QMuse

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Maybe there's some error or not in the bass, like you said, different sources give different results, and I've learned to mainly look for the rough contour of the bass rather than exact contours when comparing among sources.

Well, that indicates you don't have much confidence in LF measurements, do you? Besides, the first floorstander that was measured had not so simple LF design as all the bookshelves and the LF looked weird. I think this deserves to be investigated. And now, SW cannot really be compared with floorstander as it is basically a compact bookshelfe optimised for LF and thus different from floorstanders.
 

QMuse

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Honestly, I'm not sure, I'm just speculating. Because response from the rear port doesn't produce relevant pressure so close?

It would be great if you could ask Klippel why was the response of that floorstander so weird at LF.
 
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amirm

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I meant that soundwaves from two radiators and port don't sum "right" before reaching the mic. Interference is excaggerated. That's why NFS gets poor data to extrapolate. That's also seen in Mads's 0,7m vs. 2m graphs.
Interference exist between two drivers all the time. That simply changes the complexity of the soundfield which is compensated for with more measurement points and higher order expansion.

The port is a problem for traditional near field measurements but not NFS.
 
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amirm

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Honestly, I'm not sure, I'm just speculating. Because response from the rear port doesn't produce relevant pressure so close?

It would be great if you could ask Klippel why was the response of that floorstander so weird at LF.
I asked about Revel F35 measurements. The architect absolutely stood by the measurements being correct in this regard.
 

QMuse

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I asked about Revel F35 measurements. The architect absolutely stood by the measurements being correct in this regard.

Well, in that case it would be interesting to hear what F35 designer/Harman would say, but I doubt we'll hear anything from them.
 
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amirm

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As has been pointed out many times previously (by me and others), there is still an objection because the axis used for the centre of expansion is not the same thing as the reference axis used for post-processing calculations (e.g. spinorama computation). So far I've only seen you tweak the former, with predictably disappointing results. Everyone agrees that's the wrong thing to do, including @Mads Buchardt himself.
I gave you the real data and you are asking for a computed/simulated one??? The fact that accuracy was reduced with different axis point is a side-effect for which I have partially compensated by using higher order expansion and more measurement point. Results have less accuracy past a point since even more measurement points are needed. But below that, accuracy is maintained and is precisely what you are asking:

index.php


Mads is not a designer/engineer, nor has run these measurements so please don't pull him into your argument.

Mads however has confirmed the issues we have found and therefore the measurements are validated due to design changes and mode inside the cabinet.

As I have said, the notion of mid-point between drivers is something that is assumed. I have yet to see a proof point of it being optimal and my measurements above shows that it is not.
 

MZKM

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I gave you the real data and you are asking for a computed/simulated one??? The fact that accuracy was reduced with different axis point is a side-effect for which I have partially compensated by using higher order expansion and more measurement point. Results have less accuracy past a point since even more measurement points are needed. But below that, accuracy is maintained and is precisely what you are asking:

index.php


Mads is not a designer/engineer, nor has run these measurements so please don't pull him into your argument.

Mads however has confirmed the issues we have found and therefore the measurements are validated due to design changes and mode inside the cabinet.

As I have said, the notion of mid-point between drivers is something that is assumed. I have yet to see a proof point of it being optimal and my measurements above shows that it is not.
I think what was pointed out which seemed interesting is that for the polar plot, yours shows a shorter distance (<1m) and theirs shows 2m, and what is assumed is that the software is showing performance at those distances.

So, is that correct, or is that distance figure irrelevant and the plot is always showing far-field performance?
 

ctrl

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So, the mystery to me is simply that us should rely on a hobbyists attempt to derive the said thresholds from somewhere else. With crude methods and lesser success, I assume, unverified, though.
I rarely deal with psychoacoustic, so please correct me if I'm talking crap.

Sources: Zwicker, Fastl - Psychoacoustics, researchgate.net, hifi-selbstbau.de
(with additions by me)

First we consider how well a masker-tone with 1kHz theoretical can mask a test tone at 2kHz, which corresponds to second harmonic distortion (HD2) - depending on the masker-tone sound pressure. This is really the worst case scenario. This would mean, for example, that only a single test tone is played at 90Hz and you would see when HD2 becomes theoretically audible at 180Hz.

If our fictitious chassis produces a 1kHz sound with 60dB (see no. 1 in the diagram), then HD2 is masked at 2kHz up to a sound level of 8dB (test tone level). Which corresponds to a perceptibility threshold of -52dB/0.25% HD2 at 60dB.

At a sound pressure of 70dB@1kHz of our chassis, HD2 is masked up to -42dB/0.8%.

At a sound pressure of 90dB@1kHz from our chassis, HD2 will be masked up to -35dB/1.8%.

1588264575685.png


Zwicker continues:
1588271745866.png



If very narrow-band noise is used as masker-tone noise, masking works better and at [email protected] HD2 would be masked up to about 8%.

1588268791001.png



When critical band wide noise is used, it is found that the masking of HD2 (or higher order distortion) works better towards lower frequencies.
In blue is the masking limit of HD2 (2.2%) at 250Hz and 60dB critical band wide noise. HD2 (0.3%) masking at 1kHz is shown in green.
1588271820535.png



The "hobbyists" of hifi-selbstbau.de, to whom I referred in Post#490, have taken a program published in DIN 45631, which can calculate the phonecurves developed by Zwicker and Feldtkeller, and have calculated the masking curves at different frequencies and sound level.

If I have understood it correctly, the program uses one-third octave bands. So a one-third octave band was used as a masker and the masking for HD2 at different frequencies and sound pressure levels was calculated - see the diagram in Post#490 (or below).
Similar to the above with the masker-tone at 1kHz (the sound produced by our fictitious chassis) and the masking at 2kHz (the HD2 of our chassis).

Because the masker consists of a one-third octave band instead of a single tone, the masking for HD2 is somewhat higher:
1kHz@90dB masking of HD2 with single tone is about 1.8%, with third octave band excitation about 2.7%.

Thus the masking of harmonic distortion is certainly higher than with a single tone as a masker. But as already said in post#490, it's about the tendency and not whether the masking of HD2 is 30% or 20% at 90Hz with 96dB sound pressure (where Amir measured the harmonic distortions).

1588272619435.png


Would also assume that the values above 90dB are pure estimations of Zwicker, because certainly no test participants could be found who had their ears destroyed with 120dB ;)

Hope, however, it has become clear that the masking limits were not simply pulled out of a hat by "hobbyists".

The limits shown are certainly not valid for a single tone masker, so everyone has to decide for himself what is more realistic when stimulated with music (more single tone or more third band stimulation).
 

LTig

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Crossover frequency change.

Further, it has been noticed, that the SP dip indicates acoustic x-over frequency is slightly higher than the initial posted 2kHz. We did a minor change to the x-over after our first batch, because we found the 19mm dome in some extreme cases could be thermally damaged. After the change we do not recall a single tweeter has been replaced in field. The change was done silently because we evaluated the performance change very well and found it insignificant. We did not see a reason to disturb market with this update, as it was way below what could justify a MKII update. However, we did see some comments on why we do not use the waveguide fully down to its optimum frequency range. This is the reason.
I would assume that with a higher x-over frequency you could use a smaller wave guide and hence move both drivers closer together which should improve vertical DI. Is this correct, or are there any other advantages I don't know of?

You wrote that you could not justify an MKII upgrade. I assume creating and testing a new waveguide is expensive. Would you think about doing this for a later model?
 
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