Neumann KH 80 DSP Speaker Measurements: Take Two

[hardisj]

Is this really as simple as finding a large open area, setting the speaker on the ground, setting the mic 1m from the speaker on the ground and running a sweep using REW?

Yes. It really is. Normally the mic is placed at 2 meters to offset the 6dB gain from 2-pi space. But it doesn’t change the shape as long as the free field distance is met. As long as you are not trying to achieve accurate response above a few hundred hertz, ground plane measurements are by far the easiest way to capture frequency response. If you want above that... that’s a different ballgame. Speaking from a lot of experience here.

Edit: The larger the free space, the flatter and more reflective the surface, the better, though. You want at least 30-40 feet of nothing around you. But even in my backyard with taller grass and typical ground unevenness and a fence about 35-40 feet, I trust the data from 20hz up to 500hz; having baselined it against a large empty church parking lot up the road from my house.

 

[spacevector]

Yes. It really is. Normally the mic is placed at 2 meters to offset the 6dB gain from 2-pi space. But it doesn’t change the shape as long as the free field distance is met. As long as you are not trying to achieve accurate response above a few hundred hertz, ground plane measurements are by far the easiest way to capture frequency response. If you want above that... that’s a different ballgame. Speaking from a lot of experience here.

Way cool. I might try this one of these days although I don't have much open space where I live. How far away does the closest surface (apart from the ground) need to be for accurate results to say 200Hz?

 

[napilopez]

Guys, a simple (and proper) ground plane measurement will tell us all we need to know regarding the bass of this sample unit. This is the easiest part of measuring a speaker. Whoever is in possession of the speaker at this point can conduct an on-axis GP measurement in minutes and report the data here.

All you need is a mic and REW. Don’t need levels. Don’t need accuracy above 400hz. Just need shape of the bass. A large backyard or parking lot will suffice.

Summoning @LeftCoastTim too, who sent in this second sample. =]

 

[echopraxia]

Both Neumann and its fans should have celebrated these measurements. Instead, a few of you decided to get out the pitchforks and go after me, Klippel, the phase of the moon, etc. You are welcome to continue but just keep in mind any down side will be straight at your feet.

FWIW, for most of the comments here, the tone I read into them is just genuine academic/scientific curiosity towards understanding the discrepancy. Maybe I'm being too optimistic, but I don't think anyone here intended to insult or attack you personally.

It's not like you designed the Klippel yourself, anyway. If it does turn out that there are discrepancies between Klippel rigs, I see this as room for Klippel to improve their system and its calibration/configuration -- and I hope Klippel sees it this way too! If in the end it is determined that your Klippel rig has a notable inaccuracy here accounting for the bass response discrepancy, I certainly wouldn't see this as an attack or even criticism of you or ASR. Instead, fully understanding the source of the discrepancy would just be an important piece of data for Klippel to improve their system, and for ASR to contextualize the currently captured data.

 

[hardisj]

Way cool. I might try this one of these days although I don't have much open space where I live. How far away does the closest surface (apart from the ground) need to be for accurate results to say 200Hz?

It’s the other way around.

Reflection path length distance Vs direct mic distance dictates low frequency cutoff for accuracy. For quick estimate, convert distance of reflection to DUT to frequency. 1125 ft/s speed of sound for estimate. For 200hz that’s a distance of 5.625 feet. For 20hz that’s 56.25 feet.

For upper frequency limit it depends on the surface. Grass is different than concrete a Live about 400hz based on my studies. And aiming matters as well. As well as ambient conditions (temp, humidity).

But for bass, it’s a cakewalk. Ground plane is by far the easiest method here.

 

[ctrl]

So we test two different speakers -- products that naturally differ from each other -- and your simplest explanation was that???

I swear some of you are just motivated to make this situation worse....

Actually, I am just trying to tell you, with justification, that there is a problem with your measurements in the bass range. My motivation is to achieve the best possible quality of the measurements and not to sabotage them.

As already shown in this thread, your measurements of the KH80, the Genelec 8341A in low bass differ considerably from other (manufacturer, Klippel, Sound&Recording, @napilopez ) measurements.

There are also many other ASR measurements of loudspeakers that show the same behaviour. Only as an example the measurements of the Revel F208 and F35 differ considerably from the manufacturer's measurements.

F208

Deviation manufacturer measurement from ASR:

F35

Deviation manufacturer measurement from ASR:

These ASR measurements also show considerably too little low bass compared to the manufacturer measurements.

Now the question arises if there is a worldwide low bass conspiracy of the manufacturers or if it is possible that something is still going terrible wrong with at least a few measurements.

 

[Pio2001]

But for bass, it’s a cakewalk. Ground plane is by far the easiest method here.

Ground plane measurements of the KH80 have been published above in this discussion, by ctrl in message 433 : https://www.audiosciencereview.com/...asurements-take-two.11323/page-22#post-425441

They match Neumann's own measurements.

 

[napilopez]

Ground plane measurements of the KH80 have been published above in this discussion, by ctrl in message 433 : https://www.audiosciencereview.com/...asurements-take-two.11323/page-22#post-425441

They match Neumann's own measurements.

I think HardiSJ was referring to the two people that have sent KH80s in

 

[hardisj]

Ground plane measurements of the KH80 have been published above in this discussion, by ctrl in message 433 : https://www.audiosciencereview.com/...asurements-take-two.11323/page-22#post-425441

They match Neumann's own measurements.

I think HardiSJ was referring to the two people that have sent KH80s in

Yup.

Amir has shown his aggravation that Neumann did not let him test the samples they provided test data for here. Most here believe (as well as do I) that the most likely answer for the difference between the samples Amir tested vs Neumann's provided is not due to sample variation and rather due to the NFS implementation. But one cannot rule the former out entirely until it is verified as a non-issue. Thus, my recommendation to conduct a simple GP measurement on the test sample provided to Amir by whoever is in possession of it currently. That will lay to rest any concerns regarding unit-to-unit consistency.

 

[Pio2001]

Thus, my recommendation to conduct a simple GP measurement on the test sample provided to Amir by whoever is in possession of it currently. That will lay to rest any concerns regarding unit-to-unit consistency.

Oh, ok. I understand now.

 

[somebodyelse]

Way cool. I might try this one of these days although I don't have much open space where I live. How far away does the closest surface (apart from the ground) need to be for accurate results to say 200Hz?

There's a whole load more detail here about @hardisj's methodology, and what did and didn't affect the results.

 

[LeftCoastTim]

Summoning @LeftCoastTim too, who sent in this second sample. =]

I've been summoned, but I don't have the space to do a proper ground plane measurement (10 meter from any boundary according to http://www.mh-audio.nl/Acoustics/Groundplane.html)

Besides, I think the only way to settle the whole NFS issue is to measure the exact same speaker multiple ways, which is what Amir is suggesting when he wants Neumann to ship him the unit they measured.

Also, I think it's not Amir's job to calibrate the NFS, it's Klippel's. If Neumann's and Amir's NFSs measure differently, then it's Klippel's job to assure quality control.

 

[napilopez]

I've been summoned, but I don't have the space to do a proper ground plane measurement (10 meter from any boundary according to http://www.mh-audio.nl/Acoustics/Groundplane.html)

Besides, I think the only way to settle the whole NFS issue is to measure the exact same speaker multiple ways, which is what Amir is suggesting when he wants Neumann to ship him the unit they measured.

Also, I think it's not Amir's job to calibrate the NFS, it's Klippel's. If Neumann's and Amir's NFSs measure differently, then it's Klippel's job to assure quality control.

Totally fair, it was just in case you had a big back yard. As someone who lives in NYC, the concept is alien to me . To be clear though, Neumann doesn't have an NFS(as far as I know), but rather Neumann sent the speaker to Klippel.

Doesn't much change your point, though what HardiSJ was suggesting is that if your speaker showed different results in a ground plane measurement, that would suggest something is off. Ground plane measurements are supposed to be reliable and repeatable.

 

[test1223]

Hello,

@GuyLayfield I really appreciate that you and your Neumann team provided the measurements of the KH80 and KH120.
The measurements of the Neumann KH120 which you can find at the Neumann homepage didn't show the 55Hz bump. I assume that Neumann upgraded the measurement system since the loudspeaker development was some time ago? I like that the development process never comes to a stopp and everybody tries to become better every day. It would be really great and beneficial, if more technical details are published by Neumann eg. Klippel measurements like you posted here. Or more advanced distortion measurements like IMD plots and such stuff. I think it would help to get a lot more sales since the achieved goals of the speakers are much more clear and visible. Technical influencer are more important than ever and with good data you will get things moving.

@amirm @GuyLayfield From my point of view the start was not the best. I hope that you will be talking with another. I think it is such a great opportunity to get audio enthusiasts joined together. So please make it a win win situation. Everyone who did speaker measurements knows there is often not only one "true" measurement and little mistakes and deviations of components happen all the time.

Is ist possible that the limiter causes the deviations in the bass since the speaker is very small and the measure process of the Klippel system is long maybe some protection stage was fading in?

As other already mentioned, I think the deviations in the higher frequencies are most likely due to the deviations in the distance and height of the displayed measurements, since there is a small diffuser in front of the tweeter which causes a very complex wave front.

It would be really great to show the deviations of the frequency response from different listening distances much more often in the future. It is a underrated topic.

Best
Thomas

 

[QMuse]

Also, I think it's not Amir's job to calibrate the NFS, it's Klippel's. If Neumann's and Amir's NFSs measure differently, then it's Klippel's job to assure quality control.

Sure, only Klippel can solve it, but they won't raise their little finger unless Amir contacs them expressing his concern of LF innacuracy, and it is hard for him to do that without measuring identical speaker on 2 NFS'es. So, as long as Amir doesn't have a solid case that LF part of the measurement is not ok things will stay as they are.

 

[QMuse]

To be clear though, Neumann doesn't have an NFS(as far as I know), but rather Neumann sent the speaker to Klippel.

Which is even better, as Klippel can't claim there was something wrong with their measurement. The only way out of this seems to be that the same speaker measrued by Klippel is sent to Amir for measurement.

 

[echopraxia]

Is ist possible that the limiter causes the deviations in the bass since the speaker is very small and the measure process of the Klippel system is long maybe some protection stage was fading in?

I highly suggest at least reading the first post (review) of this thread before posting suggestions/questions that were already addressed there.

 

[echopraxia]

@GuyLayfield, I hope you know your silence here is very concerning to your customers (like myself) and this community as a whole.

Please do not make me eat my words where I stated how much a Neumann fan I am, in response to your initial post (which contains very helpful data!) I had assumed you would be sending your test sample to @amirm for testing as well, since you already apparently went to great lengths to send it to Klippel.

You should know that if you refuse to send this sample to Amir, this changes the tone and impact of your measurements contribution drastically, in contrast to what I had assumed would be the start of a wonderful collaboration.

If you cut off ASR from this experiment, this would demonstrate that — while you are willing to go to great lengths to make Neumann look better, you refuse to put in an additional 1% of effort required to turn this experiment into something that benefits the community far more (by simply shipping the sample to Amir so he can work with Klippel to debug any discrepancies). I really hope this is not the case.

Cost is not a factor here; many of us here would gladly donate the cost of shipping. For the record, I would gladly do so myself, if shipping cost were somehow the only concern here.

While measurement data contributions are always helpful for consumers in a broad sense, it is not helpful to this community (to which you posted) if you perform this experiment with Klippel, and cut ASR out of the equation. What ASR is doing here is a vastly more important contribution to the audiophile and pro audio world than any one set of measurements for any one manufacturer could ever be.

So please understand that while your contribution of measurements individually is much appreciated, posting here on ASR does add some implicit responsibilities on your part to contribute constructively to this community, if you want to maintain a positive relationship with your customers (like myself).

 

[Deleted member 16502]

If it's feasible financially, what about raising funds to buy @amirm a KH 80 off the shelf for testing and having the unit measured by Klippel (they do offer measurement as a service)? No second thoughts about golden sample then and Klippel sure will be more interested in demonstrating their product produces reliable and repeatable data than Neumann.

Could also be done with any other speaker @amirm has already measured.

PS: If you need a guy in Germany to deal with Klippel formally I'd help.

 

[pozz]

So please understand that while your contribution of measurements individually is much appreciated, posting here on ASR does add some implicit responsibilities on your part to contribute constructively to this community

Well said.