Kvålsvoll Design Audio Forum

EnglishEnglish text EN    NorskNorsk text NO
Please or Register to create posts and topics.

F205: Den lille høyttaleren som setter ny standard for lyd

My own black F205 in Room2 got new adjustable bases, and also an upgrade on internals from version 50 to current version 81 - there are changes to the internal iplate and internal damping in both chamber V1 and chamber V2.

So, does it sound better? Hard to say. The difference is measurable, sure, but how audible those differences are, is hard to say exactly.

But - there is another experiment that is now ongoing - analysis and comparison of open ports and closed ports. Does the effort of developing and then building the speakers with this quite complicated construction actually pay off in better sound.

This has of course already been tested and measured, but not in a normal stereo set-up, listening to music.

To measure the difference is easy - yes, there is a measurable difference, but in Room2 this difference is small - to evaluate by listening is difficult. Because obtaining objective data from listening is difficult.

I have just started on this, in Room2, and will continue with both measurements and listening in the media-room, where at least measurable differences are likely to be larger due to lacking room acoustics and speaker placement closer to (reflective) boundaries.

Those initial listening tests in Room2 reveal something quite interesting - yes, there is a difference. If the ports are closed, much of the magic in the F205 is gone.

Vocals - you know when the vocal sort of floats in space, in between the speakers. With closed ports, it still floats, it is still a 3D-image of the singer between the speakers, but - it kind of splashes out of its boundaries, it is not solid all the way, like there is half a singer with head and upper body, and then the rest is kind of blurred. With ports in function, the singer is rendered solid all the way, it is a body with a specific size that sort of solidifies, with clearly defined boundaries. This is more or less lost with closed ports.

Tonality is brighter with ports functional, or darker, warmer with closed ports. The differences in frequency response alone can not explain this.

Everything percussive - like drums - is more sharp and defined and natural with ports. Closing the ports still leaves a holographic image of a drum, precisely placed in 3D, but they are kind of sluggish, they are not "for real", they sound more like drums reproduced by a speaker. It also sounds more dynamic with open ports, drums are not louder, they do not necessarily sound more powerful, they just get this added sense of snap and immediacy on the attack.

With ports functional, there is a sense of presence to all instruments, like they are for real, right there.

Does the directivity control added by the complex acoustic port system pay off?

I have continued the experiments, now on two different systems, both with F205 main speakers, one in room2 and one in the media room with less optimal acoustics.

My conclusion so far, is that those ports are an essential part of the F205. Close the ports, and the magic is gone. With ports operational, there is a huge improvement in perceived dynamic contrast on transient instruments, and imaging also improves so that instruments are more clearly separated and their body is more solid and defined.

Yes, there are measurable differences. There is a small difference in frequency response, since I have not bothered to eq out this difference. In both room there are differences in very early decay, and in the media room resonances from the room are reduced.

So there will not be a down-scaled version of the F205, with a simple sealed cabinet. If you are content with that sound, just buy a different speaker from someone else, there are many excellent options to choose from nowadays.

F205 acoustic port radiation control compared to horn

The acoustic port radiation control in the F205 has an obvious advantage over horns - SIZE.

Since the F205 is actually a quite small speaker even compared to normal hifi-floorstanders, and a horn with pattern control down in the 100Hz - 200Hz range needs to be large - approaching 1m mouth dimensions - this difference in size becomes huge.

A speaker with dimensions more than 60cm wide, and at least equally deep, is not something that can easily be integrated in any small room. So no wonder that those real horn installations are rare. The F205 is possible to place in even very small rooms, it does not take up much space, and it will not be so visually intrusive. So if the most important advantages of a real horn system can be achieved in such a small package, this should be a very interesting alternative for many audiophiles.

And the F205 surely do have impact in transients, realism, clarity. It just can not play equally loud as a huge horn speaker, but it does not have to. It just needs sufficient capacity for a small room, for a typical listening distance around 2m to 3m. And for this, the F205 has plenty capacity, even for full volume. Same sound character, just not enough capacity for a large ballroom - which you do not need, in a small room.

It is also important to notice that this sound character also makes a difference at low volumes. Perhaps even more important. You get this sense of dynamic contrast and clarity, without needing to turn up the volume, and this virtue is very appreciable, listening at low volume can be very relaxing and pleasant.

It is not the design principle of a speaker that defines how it sounds, it is the resulting sound output - its frequency response, lack of resonances or distortion, and - radiation pattern. It does not matter how a specific radiation pattern is achieved. And replacing a huge horn with acoustic ports reduces the size of the speaker into something that is practical.

The rest of the speaker must of course also be designed appropriately - pattern control is necessary also at higher frequencies, but here the physics allows for much smaller sizes. The elimination of compression drivers and using a medium sized AMT instead, gives the F205 its unrivaled high frequency reproduction with ultra-high definition combined with smoothness.

Compression charts for the F205:

Compression referenced to 75dB, measured at 1m. Mic position vertical height close-to but slightly below HF horn center vertical axis, which means it does not sum up correctly in the 1Khz-2Khz range, this is also measured in-room, so accuracy is not perfect.

Level is slightly lower than labeled - 1dB down - so 75dB is more exactly 74dB, 95dB is 94dB and-so-on.

110dB measured with limited frequency range 120Hz-1200Hz, all 1/6 octave smoothing.

Other than the HF AMT-in-the-horn that simply refuse to compress or show any sign of distress, this is fairly decent, but nothing exceptional. But add in the size of the speaker and that it is also a acoustic-directivity-controlled speaker ("cardioid"), with 2x 5" drivers, it is quite good. Compression is measurable, but it still keeps up at 110dB, the limit is even louder. And the distortion data shows a similar behavior - distortion rises a bit around 85-95dB, but then is sort of "established" and does not go through the roof even at 110dB. Keep in mind this speaker is intended for relatively short listening distance - 2m - 3m, at 110dB/1m it meets the requirements for full-scale music reproduction.

All measurements done with 120Hz high-pass, as the speaker is intended to be used, with a separate bass-system. This induces a roll-off starting right below 200Hz, which reduces the output in the 100hz-200Hz range.

Lines (ref. 75dB): 85dB - 95dB - 100dB - 105dB - 110dB.

Analysis and comparison of open ports and closed ports - measurements and controlled listening test

I can now show measurements that shows the difference between open and closed ports on the F205, this verifies that there is a difference and that this difference is large enough that it is not unlikely there is also a difference in sound.

And, I am looking into how a controlled listening experiment using recordings from the speakers playing, can be used to verify at least some of the differences in sound.

Analysis and comparison of open ports and closed ports - measurements

Waterfall with proper scaling show a difference in early decay - open ports has better reduction in very early sound. In Room2 - Closed ports left, open right:

And the right speaker:

In Room2, the difference in spectrogram view is not large, but still measurable and can be clearly seen:

In the media-room, with less optimal acoustics and placement, the spectrogram shows a larger difference:

And a similar difference can be observed in the waterfall, for the media-room, left speaker:

Left + Right speaker:

Differences can be observed in the 100Hz-1KHz frequency range, where the open ports clearly reduces early reflected sound. It can also be seen that the ports do not have any significant effect on frequency response, the improved radiation pattern does not remove dips and cancellations.

Also note that the graphs show no difference above 2KHz, which is expected, as the only differences between the measurements are ports open or closed. If there was a difference outside the 100-1K range, that would indicate the measurements had insufficient repeatability due to measurement set-up or noise.

So, a measurable difference has been documented. But, you need to know what to look for.

F205 serial number 13 and 14 was delivered to the customer yesterday.

After quality control measurements, I put them up in a close near-field positioning, and placed a pillow on the floor to sit on. I needed to hear them. The F205 works fine at listening distance down to one meter, with a coherent soundstage, a true near-field experience. With amazing rendering of the recording, right in front of me.

They are the last of the F205.