AsciLab F6Bs Review

[Nuyes]

The F6Bs is a budget model from AsciLab, featuring a 6.5-inch driver with an impressively slim profile—only 15.5 cm in depth.


Before we begin, a quick note:
The version I measured is an early production unit with sharp corners, not the rounded version currently being distributed globally.





Impedance

No unusual resonances or anomalies were observed. The minimum impedance measured was approximately 3.65 ohms.





On-Axis Frequency Response

This speaker was clearly designed with shallow applications in mind—such as ceiling or rear channel use—given its 15.5 cm depth.
As expected, the bass roll-off begins relatively early, around 100Hz, but maintains a gentle slope of approximately 6dB/oct before steepening to 18dB/oct near 60Hz.
The final low-frequency extension reaches -6dB at 65.3Hz.


The on-axis response is generally well-balanced with minimal ripples. There’s a noticeable dip starting around 5kHz, which I’ll address later in more detail.

Although I use a Klippel system for speaker measurements, I do not use an NFS scanner, which makes it difficult to generate clean Spinorama plots.
Technically, it’s possible—but the post-processing is too time-consuming to keep up with regular review publishing.
That said, I’ve finally created a Python script with the help of ChatGPT that processes and organizes my measurement data. This means I can now include Spinorama plots moving forward!


But that’s not the main point...

By analyzing the Listening Window (±30° horizontal, ±10° vertical) and Directivity Index (DI), it becomes clear that this speaker is tuned more for a smooth listening window rather than targeting a razor-flat on-axis response. This is a smart and user-centric design choice.





Nearfield Measurements

Clean and well-defined—excellent performance.
Once again, the crossover frequency appears to be set quite low.
However, based on AsciLab’s proven track record with higher-end models, this doesn’t raise any immediate concerns.
We’ll confirm this further in the distortion section.





Directivity

As expected, the speaker delivers very smooth directivity.
I once said something similar in an older review—maybe about KEF or Genelec; I can’t quite recall. But to be honest, speakers from manufacturers like Neumann, Genelec, and KEF, known for their strong engineering, often don’t leave much “room” for criticism in reviews.
Why? Because they’re already extracting near-maximum performance from each design class.


And AsciLab seems to be following the same path.


That’s great news for consumers.

The vertical directivity is also superbly controlled—almost too perfect to comment on.





Beamwidth

The beamwidth remains stable around 60 degrees, maintaining excellent neutrality throughout.





Polar Plots

Absolutely outstanding.
The gently widening dispersion in the upper treble is particularly elegant.

Vertical polar performance is just as impressive—smooth and consistent across the entire frequency range with no abrupt changes.





THD (Total Harmonic Distortion)

Overall distortion is excellent, but I did identify the first true flaw.


A slight mechanical noise appears around 250–300Hz, which I was able to confirm audibly during signal playback.



To investigate further, I measured the second unit of the pair (provided by a client), but the issue did not occur in that sample.
In practice, the noise is barely audible—if at all—but it’s worth noting.

This is, in fact, the only sign that this is a budget-class product.



Important note: The unit I measured was an early pre-distribution version.
I’ve since received confirmation from the manufacturer that the issue was identified and has been completely resolved in current production.

Aside from that, the F6Bs delivers distortion performance on par with professional studio monitors.

Even at 95dB SPL, its composure remains intact—an impressive feat.





Multitone Test

Again, this speaker is outstanding.


Multitone distortion is heavily influenced by low-frequency excursion.
While the limited bass extension (around 65Hz) certainly helps the plot, the speaker still performs exceptionally well considering this constraint.


For a deeper explanation, see the MD section in my Arendal 1961 Bookshelf review.

After my review of the 1961 Monitor, I received a critique from a user on another forum questioning the objectivity of the review.
The main point of criticism was:


“Multitone distortion is heavily influenced by driver excursion. Since this speaker has limited bandwidth, it's naturally at an advantage in multitone tests.”


This is, in general, a valid observation.
However, the fact that multitone distortion is affected by excursion does not, in itself, disqualify it as a useful metric for evaluating or comparing speaker performance.


With few exceptions, driver excursion across frequencies below the resonance point is largely consistent (excluding low-frequency creep due to the suspension’s mechanical compliance).
In other words, if two speakers of similar diaphragm area (i.e., in the same class) are outputting the same SPL at their respective driver’s resonance frequency, their excursions will also be nearly identical.
This is because acoustic output is primarily determined by diaphragm area × excursion.


(I say “nearly” because even among same-sized drivers, effective radiating diameter may vary slightly. Strictly speaking, factors such as resonance characteristics, diaphragm geometry, and baffle conditions also play a role.)


Now, let’s imagine placing only the woofer drivers of two such speakers into the same infinite baffle with identical enclosure conditions and output level.
Would their multitone distortion results be similar, given comparable diaphragm areas?


Not necessarily.
And this is precisely why multitone distortion can offer insight into the overall build quality and execution of a finished speaker system.
(Of course, it is not sufficient on its own for evaluating a loudspeaker in its entirety.)


When two or more tones—including both high and low frequencies—are reproduced simultaneously (i.e., multitone testing), the resulting distortion is influenced by much more than just excursion-induced Doppler distortion (i.e., frequency modulation / 2nd-order IMD).
It also reflects effects from voice coil position, nonlinearities in the suspension system, inductance modulation, and various other non-ideal behaviors.


Therefore, as long as the resonance region is adequately stimulated, comparing multitone distortion between speakers of similar size and diaphragm area can be meaningful as a measure of driver and system build quality.


Naturally, when significant issues are observed, the root causes are often complex and not directly identifiable from the multitone plot alone. So caution is required in interpreting these results in isolation.


That said, exceptionally low multitone distortion remains a strong indicator of a well-engineered driver and a well-integrated system.


To partially decouple the effect of low-frequency tuning decisions made by manufacturers, I’ve also included distortion data starting from 80Hz, which may provide a more neutral basis for comparison.

80Hz~

Multitone Performance

No unusual behavior detected—everything remains clean and stable.





Compression Test

Frankly, the results are laughably good.


Around 1kHz, the slightly lowered crossover frequency means compression is mostly governed by the tweeter, but even so, it's within 0.5–0.7dB, which is excellent.


In the woofer range, the results are surprisingly strong—far exceeding what I would expect at this price point.





Deviation between 2 samples

If I hadn’t measured these myself, I’d suspect the manufacturer sent me hand-selected golden samples.


For a passive speaker in this class, such consistency is truly exceptional.


I doubt they’re individually matched before shipping. More likely, AsciLab simply starts with high-quality components and assembles them with great care.


It’s fantastic.





Conclusion
Let me wrap up with a personal thought:

It might be time to redefine what “cost-effectiveness” means in the speaker world.
This speaker was measured using the CEA-2034 standard.
It offers not only a solid on-axis response but also refined performance across the Listening Window, DI, mechanical stability, and minimal unit-to-unit variation—all at this price point.


I’ll let the results speak for themselves.
That’s all.

 

[kharan]

Nice, we can see how close these samples measure compared to both Amirm's and Ascilab's own measurements.

 

[Curvature]

I like your consistency across reviews, particularly the different distortion charts. They really help illustrate where speakers diverge in their engineering.

 

[eyke]

@AsciLab will there be some kind of user manual/guide?

 

[rubendub]

This is my first post here on ASR, and I thought I’d begin by sharing an experience that left a deep impression on me.

With a free day after my concert in PyeongChang, I had the privilege of visiting the Ascilab workshop. As someone who has followed their work with great interest for some time, it was a rare opportunity to see the place where their designs are developed, prototypes are built, and measurements are conducted — not just to confirm performance, but to keep questioning it, even when the results already look excellent. That, to me, was the most striking part.

Meeting Jinsung in person was one of the highlights of the visit. It’s rare to encounter someone with such a profound technical mind who is at the same time so humble, kind, and grounded. He’s so quietly confident in what he does that he feels no need to defend or assert anything — instead, he shares his thoughts with striking generosity and calm clarity. And no, he didn’t try to sell me anything.

I listened to the full Ascilab lineup — from the compact 5-inch model to their largest systems, including the prototype of the upcoming cardioid flagship. Hearing them in Jinsung’s carefully prepared room was a rare experience: each speaker showed a remarkable consistency in tonal balance, clarity, and spatial precision across very different sizes and designs. The cardioid prototype, in particular, revealed a level of transparency in the cello and double bass range that I had never encountered before — not even in the professional recording studios where I’ve produced my own albums.

What stood out to me was how precisely Jinsung translates measurements into design. In theory, the data is available to anyone — but few invest in the tools to capture it properly, and even fewer are willing to stick with it long enough, free of dogma, until the design has been refined to the edge of what’s possible.

I left the visit with great respect for the clarity and depth behind Ascilab’s work.

 

[totti1965]

This is my first post here on ASR, and I thought I’d begin by sharing an experience that left a deep impression on me.

With a free day after my concert in PyeongChang, I had the privilege of visiting the Ascilab workshop. As someone who has followed their work with great interest for some time, it was a rare opportunity to see the place where their designs are developed, prototypes are built, and measurements are conducted — not just to confirm performance, but to keep questioning it, even when the results already look excellent. That, to me, was the most striking part.

Meeting Jinsung in person was one of the highlights of the visit. It’s rare to encounter someone with such a profound technical mind who is at the same time so humble, kind, and grounded. He’s so quietly confident in what he does that he feels no need to defend or assert anything — instead, he shares his thoughts with striking generosity and calm clarity. And no, he didn’t try to sell me anything.

I listened to the full Ascilab lineup — from the compact 5-inch model to their largest systems, including the prototype of the upcoming cardioid flagship. Hearing them in Jinsung’s carefully prepared room was a rare experience: each speaker showed a remarkable consistency in tonal balance, clarity, and spatial precision across very different sizes and designs. The cardioid prototype, in particular, revealed a level of transparency in the cello and double bass range that I had never encountered before — not even in the professional recording studios where I’ve produced my own albums.

What stood out to me was how precisely Jinsung translates measurements into design. In theory, the data is available to anyone — but few invest in the tools to capture it properly, and even fewer are willing to stick with it long enough, free of dogma, until the design has been refined to the edge of what’s possible.

I left the visit with great respect for the clarity and depth behind Ascilab’s work.

Thank you so much for your thoughts, Ruben! Much appreciated - and a warm welcome here!

I spent a whole hour yesterday watching a full YouTube video of a Factory Tour:
Dan D'Agostino

Man, what an inefficiency!

Then half a factory tour video about Accuphase......

Man, tight as a birdcage with them.....

I'd love to take a look at the Chinese factories. Topping, SMSL, Fosi and then of course the factories where all the 70s clones are made....

Or even the AsciLab Production in Korea.

But I only found a picture gallery at L7 (member @WolfX-700) for Moondrops in-ear production:

MoonDrop Factory Tour - L7Audiolab

访谈、随笔、观点

www.l7audiolab.com

We're talking about 50 year differences in production methods....

I pretty much assume, we are on the modern, the 21st-Century-side, with AsciLab!!!

 

[totti1965]

@AsciLab; @Nuyes: Even though the AsciLab C6C won't be released until October or so, can you still tell me the exact dimensions (length, width, height) now?