F205: How a Small Loudspeaker Sets a New Standard for Sound

What I hear is different, and I realize it is different simply because it is so much better.
Small size, works in ordinary small rooms, decent looks, acceptable price. This, combined with significantly better sound – that is the sound of the future.


A New Standard for Sound

I put on Lyle Mays, the track Ascent from the album Lyle Mays. Master volume up to + 8dB, this is a true pre-loudness-war production, and the bass level is moderate. Here you have to turn it up loud to get the proper physical tactile experience. This is huge – in terms of music experience. Here, the F205 manages to reproduce this masterpiece with dynamics intact, combined with clarity and definition that is not compromised by the somewhat high sound level.

It’s hard to write about things I have made myself. About F205 and the sound. Because I am the one who designed and built it, this is my creation. This will of course color my impressions, and the reader will assume that the story being told is not neutral. And I want to present what I have made in a positive way, but also credible and fairly correct. Therefore, I must try to convey the most balanced impression possible, where both good and bad qualities are included. For F205, this is especially difficult, because I like it so much. It is simply difficult to find something that is wrong.

There is this clarity and openness. Everything is so clear, sharp, defined. Over the entire frequency range, from the top treble, down through the midrange, all the way down to where the bass system takes over. Compared to regular hifi speakers, it is like the F205 removes a cloud in front of the music, everything is much clearer and defined.

Transients have this realism and power that good, large speakers provide. Turn up the volume, and there will be a physical hit from snare drums. It’s not like drums and transients are overexposed, it sounds in a way very natural. A special feature is the ability to keep the drums deep behind in the soundstage, no matter what happens.

Flashbulb, Kirlian Selections album. Autumn Insomnia Session is a kind of dynamic orgy with explosive drums. The F205 manages to reproduce this at full volume, with a power and realism that one associates with huge custom installations. It is also much more than just power and slam, it is strange how the individual sound character of the different drums are preserved, quite clearly and distinctly.

Further out in the album, California Dreaming. Now a more moderate volume is better suited, dynamics and impact is not the focus here. There is a huge room, which extends far, deep forward. Things happen far away, far ahead, there is a huge three-dimensional landscape where these sounds appear like a picture of a solid body, accurately placed.

The violin in Kirlian Selections III. Here a unique combination of soft and rough is revealed. It is soft, but at the same time a kind of pleasant sharpness, as real instruments are. Soft, but never polished.

Voices of Music, Biber Violin Sonata, Gabrielle Wunsch, has the same thing – soft, but not polished.

Billie Eilish. It’s simple, direct. At the same time with nuances and contrasts, which emerge in a magical way, a vocal with a presence that just has to be experienced. It is simply this ability to convey music and atmosphere.

Hadouk Trio, Air Hadouk, track Dididi. Here is this saxophone-like instrument with a distinctive sound, a kind of crispness, which becomes very fascinating on F205.

Treble that is both soft and rough at the same time, I have mentioned. Then there is this with weight – sounds far up in the frequency register get solidity and body.

What is characteristic is that everything is connected in a way, it is homogeneous, nothing stands out. Instruments appear as one body, all the sound over the entire frequency range comes from the instrument. And the instruments retain their own sound, so that there is a great contrast between them.

The sound is magical in the listening position in the center, this is where instruments and sounds appear as real, it does not sound like sound from two speakers. If you move outwards towards the sides, a lot of the magic disappears, but the sound always has reasonable tonal balance, the treble does not disappear, and there is actually a kind of soundstage all the way to the side walls in the room. And this is not due to room acoustics alone, it is the speakers. Other speakers are not like that, the only one I have had here in Room2 with similar properties is the F2.

I end my session with Jøkleba Live, Mayshia. Brutal. Powerful. This reveals an ability to play loud without it becoming sharp or uncomfortable, so that it is actually possible to enjoy this music at loud volume. Even the most powerful parts are reproduced with ease and stability in the soundscape, and the trumpet is never sharp.

In the still of the night..

Dynamics and transient reproduction and capacity are in place. Equally important is that it also works at low volume. Sitting through the evening and listening to music for several hours, finding something new, retrieving old albums, the volume is low and comfortable. This clarity and definition is still present, it is not necessary to play loud to hear everything.

F205 in Room2.

Requires a good amplifier

To unleash the full potential of the F205, puts high demand on the amplifier. Sensitivity is moderate at around 91dB, and it draws a lot of current with impedance below 4 ohms and large phase angles. Therefore, you can not expect to power these well with a small stereo amplifier, or an AV receiver.

This is of course related to how loud you intend to play. At low volume, a 5W tube amplifier is sufficient.

The active version has a good built-in amplifier suited for the F205. This also has all the necessary DSP processing for integration and crossover to the bass-system. A simple, predictable and high value for money alternative.

A system with T6-Flat-A uses the amplifier in T6 to drive F205. Not very powerful, but good, and easily drives the somewhat difficult load that the F205 constitutes. This amplifier is more than powerful enough to drive the F205 when used with the T6, because the subwoofer limits the capacity.

Some will want to use other power amplifiers, experiment with different models. With F205 this is possible, because the F205 itself has a passive crossover implementing all corrections, you can connect an ordinary amplifier. F205 combines the benefits of an active system and the traditional where it is possible to choose and experiment yourself.

A Buurion, a Guurion, and one more Guurion. All very well suited to power the F205.

Developed for use at home in normal rooms

Such a small speaker must have limitations, no matter how good it is. And it has – it does not have quite the same output capacity as larger speakers built according to the same principles can have – like large horns, something with 12″ or larger in the lower midrange. The F205 is not suitable as a PA system in a ballroom. But it does not need to be able to fill a ballroom, when a normal listening room is so much smaller, and the typical listening distance is around 2.5 meters. What you can achieve with a larger speaker is an even more relaxed character on powerful transients in the midrange, a bit cleaner and more powerful. But it depends – with a powerful amplifier, and favorable placement and room acoustics, then there may not be much improvement compared to the F205.

It is voiced quite flat, and combined with the controlled radiation, this can give a response with the impression of slightly low level in the lower midrange. This is because the sound is not colored as much by reflections and resonances as with other speakers.

Whether it can be done better? Yes, I believe so. I am convinced that the reproduction of sound has not yet reached a level where there is nothing more to find – even with the F205. The F205 now represents a major step towards better sound, with technology and solutions that future speakers will benefit from. But right now, I’m happy with the F205, and do not sit back and wonder what could have been better, when I hear music.

This sound makes it very engaging to listen to music, it becomes in a way addictive. So captivating, makes you keep on listening to hear and wonder, for several hours, with all kinds of music. And bad recordings, those are now scarce, most productions can be played and can enjoyed as they are.

But are there more people who like this?

There have been some visits to Rom2 now, where people have heard the wonder. Some impressions recur, while of course it is not possible for me to get a complete picture of another person’s experience of the sound.

That it also works at low volume is something several have noticed. And then there is this holography, how one senses that one can get up and walk around among the instruments, this is something new for most people.

One goal is to create something that is so good, that it opens up new customer groups, simply make the market for audio products larger. Get those many who are not very concerned about sound quality, to want this at home. Then the sound must give something more than small improvements that only a sound enthusiast can notice, it must give an experience that differs significantly from everything else, and we must like it.

The Sound of the Future

Small size, works in ordinary small rooms, decent looks, acceptable price. This, combined with significantly better sound – that is the sound of the future.

Now I have finished my attempt to describe what the F205 is. The rest here is about technical solutions and how this speaker came to be.

F205+T6-Flat-A System

Design Requirements

A very small speaker with the same sound as a large one, with the only limitation that it does not have to play loud in large rooms. This is a brief summary of the requirements specification for F205.

In the article  Can a small speaker be as good as a large summarized properties such a small speaker must have:

  • Separate bass system
  • Dimension for sufficient capacity
  • Transient reproduction
  • Radiation control

The entire construction, with the horn on top and cabinet with acoustic ports for radiation control, came to life like this because the sound field from the speaker must satisfy specific technical requirements.

The development of such a speaker is a combination of art and science.

Behind the technical requirements is an idea of ​​how the sound should be. Kvålsvoll Design products have their distinctive sound – it should have a natural sound, with dynamics and realism. Ideas like “everything sounds the same”, “it does not work”, do not fit in here. Achieving this has previously been synonymous with huge speakers. And getting everything to work simultaneously is difficult. Then it turns out that if you manage to get capacity and radiation control in a small speaker, then you also solve some problems that large constructions cause.

How it was done

Only as strong as the weakest link. There is no point in making one brilliant solution for one particular problem, if the rest of the design is just average.

The radiation control is achieved using horn for higher frequencies, and acoustic ports on the side of the cabinet at lower frequencies.

The crossover is special. At the bottom, actively crossed over to a bass system at 120Hz. This crossover is made so that flat phase is possible and no time discontinuity occurs in the important upper bass area.

Crossover between midrange and tweeter is passive, with extremely sharp cutoff and controlled phase and time behavior. F205 is not phase linear, this is due to the AMT driver, the passive filter in itself is close to linear phase. This ensures sound never comes from different speaker drivers at different time in the same frequency range, and this is of great importance for perceived soundstage and resolution.

Choice of parameters and properties for the drivers is responsible for much of the sound in the F205. The HF driver in the horn is a medium-sized AMT, it has exceptionally low distortion and decent capacity. The LF drivers have very good transient reproduction and high sound pressure capacity, as well as covering their range completely without resonances from diaphragm or other moving parts. This is possible because they do not play bass, and they only work up to 1700Hz where the HF section takes over.

Sound from the rear of the drivers is acoustically filtered inside the cabinet, and radiates out through the holes on the side. This sound, combined with the sound from the front, creates radiation control down in the mid- and upper bass frequency range. To achieve this, there are three chambers inside, with four different types of acoustic damping material, there are acoustic ports inside the cabinet. The radiation pattern gradually widens downwards in frequency, like a normal large speaker, only slightly narrower so that less sound is sent backwards and out to the sides. In front of the speaker, towards listeners, the radiation is smooth and even.

An important part of the internal acoustic construction is how reflections from the sound inside the cabinet are handled. Many standard box speakers have a deep cabinet filled with damping material, this can work quite well. In F205, the cabinet is far too shallow for this procedure, where dimensions are a consequence of the requirements to get correct response of the sound coming out of the acoustic ports. Simulation is useful in the design process here, and analysis of the cabinet when built, to see that it actually works as intended.

Analysis of the sound in the nearfield in front of the cones of the loudspeaker drivers and the acoustic ports reveals resonances or unwanted reflections. Here the response is completely smooth. The consequence is that the midrange retains all the clarity and definition that these small speaker drivers can deliver.

The horn with the AMT driver is designed for a very precise radiation pattern, where sound is evenly distributed over a large area forward into the room towards listeners, and sharp cut-off outside, across the entire frequency range from 1700Hz to the top. A challenge here is the size of the speaker, which limits the size of the horn – it is a very close fit. Horns can also be used for the rest of the frequency range downwards, but then the speaker will become very large, with dimensions close to 1 meter in width.

The entire speaker is simulated in a computer program, prototypes are built for parts such as the horn, then those parts are tested and measured and simulated again. Then the entire speaker is built, with new rounds of simulation and measurement and adjustments. Finally, I have prototypes that are finished to a level that I can put on music and listen. Then there are fine adjustments, with a lot of listening and a lot of measurement in different rooms with different positioning. Very many measurements, and many days of listening, so that the person who buys the speaker does not have to do this – just unpack, place it and connect, and it works.

All this is costly to make. The cabinet is complicated, the drivers are quite expensive. The price is therefore a bit higher than a medium plastic box or soundbar, but then the sound is so much better, that the extra cost makes sense. If you compare to very expensive speakers, it gets interesting. Because the F205 has qualities that surpass even the most expensive hifi speakers, so that a downgrade in price actually leads to a upgrade in sound.

F205 in Color


Product page: F205 Loudspeaker
Specifications on product page: F205 Loudspeaker Specifications

Model: F205 / F205-A Loudspeaker


Freestanding active (F205-A) or passive (F205) speaker for music and entertainment in small and medium-sized rooms, for use in stereo pairs, integrated with bass system for low-frequency reproduction.

Frequency range

120Hz – 20KHz


91dB / 1m / 2.83V

Nominal impedance

4 ohms (Minimum 3.6Ω @ 196Hz)

Recommended amplifier power

5W to 400W

Power capacity

300W AES (AES2-1984) / 600W Program (Normal music signal)

Sound pressure capacity

111dB / 1m /> 120Hz

LF section

2 × 5 ″ high-capacity drivers in small cabinet with damped acoustic ports and internal chamber.

HF section

Medium-sized AMT driver and horn with controlled radiation.

Crossover frequencies

LF section to HF section: 1700Hz controlled phase, extremely sharp slope.
F205 to bass system: 120Hz active dsp-controlled.

Recommended listening distance

1.6m – 3.2m

Tilt adjustment for vertical listening height

0 ° – 2 ° – 4 °

Horizontal coverage

± 42 °


949mm (floor-to-top) / 162mm (baffle width) / 182mm (cabinet depth). Base 232mm (width) / 204mm (depth)


F205 dimensjoner

F205-A Active Version


Internal Hypex nCore FA251.

DSP functionality

Processing for bass-system crossover and integration, eq, delay, programmable.

Amplifier output power

250W / 4Ω


+ + +

  • Soundstage
  • Realism and dynamics
  • Size and design
  • Price – performance ratio

– – –

  • Insufficient capacity for larger rooms and long listening distance

Simply a new standard for sound. This sound makes it very engaging to listen to music. That this is possible in such a small size is new.


Lyle Mays, Lyle Mays

Flashbulb, Kirlian Selections

Voices Of Music, Biber Passacaglia, Gabrielle Wunsch


Hadouk Trio, Air Hadouk

Jøkleba, Live



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