After quite some time, Neumann finally released a new model in late 2022.
What makes this one especially exciting is that it neatly fills the gap between the KH80 (4") / KH120 (5") and the KH310 (8") — at a very versatile 6.5" size.
The back panel follows Neumann’s traditional style.
With the XLR connector mounted from the bottom up, you can place the speaker flush against a wall or bracket without interference — a thoughtful touch.
Frequency Response
As expected from a professional monitor, performance is excellent.
The overall balance is flat and smooth, with the -6 dB low-end extension measured at 39.4 Hz.
For reference, my graphs use 1/24-oct smoothing. (The CEA-2034 standard specifies a minimum of 1/12-oct; a larger denominator means higher resolution in the data.)
Cross check with ASR Data
I overlaid my results with the official measurements from Audio Science Review.
The two sets of data match extremely well, except for the low-end extension.
The Klippel NFS system used by @amirm is especially reliable in the low-frequency range.
Nearfield Measurements
As you’d expect from Neumann, all responses are clean and well-controlled.
The woofer shows no signs of breakup modes at higher frequencies, and the port is free from pipe resonance noise.
Let’s take a closer look at that last point.
In the rear-panel teardown photo, note the white section I’ve outlined.
This is an effort to control the inherent pipe resonance that can occur in any port design.
For a more detailed explanation of this topic, please see my article here:
https://audiore.kr/스피커-성능-측정-보고서/
Interestingly, there’s an opening at roughly one-quarter of the port’s length, backed with acoustic damping material to absorb resonances.
On closer inspection, there’s also a layer of black foam sandwiched between the white foam and the port opening — with each layer having noticeably different density.
This appears to be a multi-stage acoustic impedance transition.
By gradually increasing the acoustic impedance between the port air column and the damping material, the design likely improves absorption efficiency and reduces internal reflections.
In simple terms:
When sound travels through different media, the more similar their acoustic impedance, the more easily it passes through.
A sudden mismatch in impedance causes reflections instead of transmission.
Neumann’s layered approach likely minimizes these reflections and boosts damping efficiency.
CEA-2034
The on-axis response is smooth, but the Listening Window curve is even smoother and flatter.
This suggests Neumann may have designed and tuned the KH150 with the Listening Window in mind, rather than focusing solely on the exact 0° axis.
Directivity
Even with no smoothing applied, the response is smooth across nearly all angles — it almost looks smoothed.
Classic Neumann performance.
Vertical directivity is also excellent: narrow, consistent, and stable well into the top end.
(The apparent widening above ~17 kHz is due to a slight dip in the 0° response at that frequency.)
Beamwidth
The beamwidth narrows gradually and evenly, making it difficult to pinpoint the woofer–tweeter crossover just from the curve — a sign of a finely tuned waveguide and excellent driver matching.
Polar Plots
Among enthusiasts, there’s ongoing debate over whether narrowing or constant beamwidth is preferable.
Here, Neumann has gone for a gently narrowing pattern, achieving remarkably uniform attenuation at almost every radiation angle — even to the sides and rear — except for a small section in the extreme treble.
Vertical polar results are also tightly clustered within the intended radiation angles, with only a slight narrowing around 2 kHz due to the non-coaxial layout.
THD
As a reviewer, I try to avoid bias — but with brands like KEF, Neumann, and Genelec, it’s hard not to expect excellence even before measuring.
Fortunately, my microphone and test rig are free of such bias, so you can trust the objectivity of the data.
Performance is impressive across the board, especially the low distortion even below 100 Hz — notable for a speaker capable of solid output in the 30 Hz range.
3rd harmonic distortion is practically at the noise floor.
When increasing the measurement output, I noticed something odd in the 150–400 Hz range — not only visible on the graph, but also audible as a noise during playback.
First, the sharp spikes in the THD curve at those points are not part of the speaker’s intrinsic response; rather, they are the result of an interaction between my measurement stand and the speaker itself.
As with the KH120’s upgrade to the “II” version, the KH150’s enclosure has also been switched to plastic.
Because of this, the speaker’s total weight is relatively low compared to the strength of its woofer, meaning that if it’s placed directly on a perfectly smooth, flat surface, a certain resonance can cause the cabinet to “walk” at specific frequencies.
This is not unique to the KH150 — I’ve occasionally encountered other models with similar issues.
These days, when such problems arise, I apply additional damping measures during testing.
However, when I measured this unit back in 2023, my view at the time was that “the interaction between the product and the test environment is inevitable, and maintaining consistency is more important.”
So I decided to record the data as-is.
That said, the issue can be mitigated by placing a heavy book on top of the speaker (to add mass) or by putting a layer of felt or EVA foam sheet under the base.
Aside from this artifact, performance is excellent.
Woofer Measurement
With the owner’s permission, I opened the unit to examine the woofer in more detail.
Close-mic measurements of 3rd harmonic distortion showed similar trends to the far-field results (blue trace).
LSI(Large Signal Identification)
This might be the first time I’ve shown this type of graph in my speaker review series.
The Klippel measurement system includes a module called LSI (Large Signal Identification), which is a useful tool for observing the driver’s state in real time, by displacement, when the driver is operating at large excursions.
For this review, I’ve brought in only two parameters: Bl(x), which represents the force from the voice coil and permanent magnet, and Kms(x), which represents the restoring force of the suspension.
Since these graphs may look unfamiliar, let me explain briefly:
The x-axis indicates the distance the speaker cone moves forward or backward from the center position of 0 mm (measured in millimeters).
The y-axis shows the magnitude of each force (Bl and Kms) when the speaker is displaced by that amount.
If a speaker could maintain its best performance whether stationary or in motion, that would be ideal — but reality is different.
Because the voice coil moves and the permanent magnet remains fixed, Bl(x) will vary in real time depending on the coil’s position.
The same is true for the restoring force of the suspension.
In a loudspeaker, this role is handled by the surround and the spider.
The further these parts move away from rest, the greater their restoring force becomes by nature.
(Think of pulling on a piece of fabric or a rubber band!)
For this reason, even in well-made speaker drivers, the Bl(x) curve typically takes on a smooth inverted-U shape, and the Kms(x) curve takes on a smooth U shape.
(The example above shows the LSI measurement results for a KEF R-series 6.5-inch driver.)
The narrower and sharper these curves become, the more the 3rd harmonic distortion component will increase relative to displacement.
The more asymmetric the curves become, the more the 2nd harmonic distortion component will increase relative to displacement.
It’s a slightly difficult topic, but thank you for following along.
Now, let’s look at the KH150’s case.
Even over a very large displacement range, the KH150 shows almost no change in the values of Bl(x) and Kms(x), maintaining a consistent shape.
In the small displacement range, the symmetry is also excellent.
This, I believe, is the secret to how this speaker can reproduce frequencies in the 30 Hz range while maintaining clean quality.
Multitone Test
Multitone distortion performance is generally very strong.
It is especially impressive below 500 Hz.
Above that, the gradual rise up to around 1.7 kHz is likely dominated by Doppler-related IMD (Intermodulation Distortion), caused by the woofer handling upper midrange content in a 2-way design.
80Hz~
That’s pure strength, through and through.
In the mid-to-low frequencies in particular, I don’t think there’s anything in its class that can match it.
Compression Test
No words needed — it’s a beast, delivering well beyond what its size might suggest.
Deviation between 2 samples
“Neumann being Neumann.”
From the KH80 through the KH120 II, the integration of DSP has pushed their QC standards to an exceptional level.
Final Thoughts
In closing, here are my personal thoughts.
Once again, Neumann has lived up to expectations, delivering top-tier engineering.
That said, with all this added muscle paired to a lighter body, it might need just a little helping hand from the user.
That’s all.
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