Franco Serblin Ktêma - low-frequency compression-loaded & room-interfaced, mid-high cardioid

[tuga]

Interesting controlled-radiation concept by Franco Serblin (creator of Sonus Faber).
It would be interesting see measurements of the Ktêma's off-axis anechoic and in-room responses.

(manufacturer page here)
(Hi-Fi News review in PDF here)

Geometry: four-way topology, five units. The two low-frequency radiators are compression-loaded and room-interfaced at the lower part of the rear of the enclosure. Above the “fusion” frequency, the mid-high cardioid radiators reproduce the significant part of the spectrum, at the top section of the front of the cabinet.

The cabinet is a rigid, triple arch-shaped structure. The two lateral front cheeks are concave, while the woofer compressor is convex.

The tweeter is a well-established and time-proven 28mm soft-dome unit, created by Ragnar Lian, one of the greatest Danish masters of transducer design.

The midrange array consists of two custom-made 4in units in a stepcompensated baffle, in a cardioid acoustic-resistance configuration, for the most accurate reproduction of the musical perspective.

The woofers are custom-made 9in metal cone, piston performanceoptimised units, in a compression-controlled and room-interfaced configuration.

The crossover is a mutational variable slope, coherent spatial radiation design.

 

[sarumbear]

Interesting controlled-radiation concept by Franco Serblin (creator of Sonus Faber).
It would be interesting see measurements of the Ktêma's off-axis anechoic and in-room responses.

(manufacturer page here)
(Hi-Fi News review in PDF here)

Geometry: four-way topology, five units. The two low-frequency radiators are compression-loaded and room-interfaced at the lower part of the rear of the enclosure. Above the “fusion” frequency, the mid-high cardioid radiators reproduce the significant part of the spectrum, at the top section of the front of the cabinet.

The cabinet is a rigid, triple arch-shaped structure. The two lateral front cheeks are concave, while the woofer compressor is convex.

The tweeter is a well-established and time-proven 28mm soft-dome unit, created by Ragnar Lian, one of the greatest Danish masters of transducer design.

The midrange array consists of two custom-made 4in units in a stepcompensated baffle, in a cardioid acoustic-resistance configuration, for the most accurate reproduction of the musical perspective.

The woofers are custom-made 9in metal cone, piston performanceoptimised units, in a compression-controlled and room-interfaced configuration.

The crossover is a mutational variable slope, coherent spatial radiation design.

The website says:

The two low-frequency radiators are compression-loaded and room-interfaced at the lower part of the rear of the enclosure.

All I see is dual woofers mounted at the back of a ported enclosure.

Small & Thiele have analysed everything about how electromagnetic low frequency speakers work, but they have not mentioned “compression loading” as one of the options. Is that a marketing term or an invention of Sonus Faber?

But I loved this:

The crossover is a mutational variable slope, coherent spatial radiation design.

 

[voodooless]

Small & Thiele have analysed everything about how electromagnetic low frequency speakers work, but they have not mentioned “compression loading” as one of the options. Is that a marketing term or an invention of Sonus Faber?

Normal people call this slot loaded, and it’s not all marketing. It basically lowers the fs a bit, so you get a bit more bass extension. It however does not control directivity.

 

[sarumbear]

Normal people call this slot loaded, and it’s not all marketing. It basically lowers the fs a bit, so you get a bit more bass extension. It however does not control directivity.

If the woofers are slot loaded, why are they visible?

 

[Jim Matthews]

If the woofers are slot loaded, why are they visible?

I believe the rear panel has been removed, for illustration.

 

[sarumbear]

I believe the rear panel has been removed, for illustration.

From what I read about slot loading, in order to create the compression, woofers face each other and the sound comes out of the slot. Like below.

 

[voodooless]

From what I read about slot loading, in order to create the compression, woofers face each other and the sound comes out of the slot. Like below.

View attachment 160551

Almost. In slot loading, the only prerequisite is a slot.. you can do this with a single driver, but two opposed also work. In essence a doe firing subwoofer is also slot loaded, it’s just that the floor and lower surface of the sub make the slot.

 

[tuga]

The website says:



All I see is dual woofers mounted at the back of a ported enclosure.

Small & Thiele have analysed everything about how electromagnetic low frequency speakers work, but they have not mentioned “compression loading” as one of the options. Is that a marketing term or an invention of Sonus Faber?

But I loved this:

The crossover is a mutational variable slope, coherent spatial radiation design.

Did you look at the design or just read the marketing BS?

The woofers are facing a baffle which is open to the sides, thus creating a sort of “chamber”. Whether that can be considered compression-loaded... Not too dissimilar to what Genelec did.
And like in the 8c the midrange is cancelled to the sides using slots.

 

[tuga]

If the woofers are slot loaded, why are they visible?

Pay a bit more attention perhaps?

 

[SDC]

Put dd8c close to wall, dial in the numbers to the dsp, passive cardioid midrange with slot loaded room-interfaced bass done. This speaker is pretty but interesting?

 

[tuga]

Put dd8c close to wall, dial in the numbers to the dsp, passive cardioid midrange with slot loaded room-interfaced bass done. This speaker is pretty but interesting?

You can do the same with this speaker and a miniDSP or REW + HQPlayer or the RME EQ DAC.

And you need an amplifier

 

[sarumbear]

Pay a bit more attention perhaps?

If I was not paying attention why am I pursuing the subject? I may say the same thing to you, the manufacturer or anyone else to explain themselves better. It was the following image you posted that tricked me. It was not clear that it was a picture of a dissembled speaker. Otherwise all it showed was dual woofers in a ported enclosure. Nevertheless, thank you for persevering with me.

 

[mocenigo]

From what I read about slot loading, in order to create the compression, woofers face each other and the sound comes out of the slot. Like below.

View attachment 160551

It is just one way of implementing it. You can also have a single driver. Or two drivers one above the other in a taller slot, thus with a reduced profile.
The compression happens when the driver fires into a small chamber, with a small opening. This is how compression drivers work.

 

[mocenigo]

But I loved this:

The crossover is a mutational variable slope, coherent spatial radiation design.

You know, it is expressed in a fancy way, but it makes sense. It may refer to the mix of different orders, and perhaps of the combination of electric and physical slopes to get specific variable slopes (as opposed to many stupid crossovers that are done with simple calculators) and therefore having the electric f3s not at the same exact values for two adjacent ways. Also the choice of the orders will affect lobing - and it is not easy to design it in a way that off axis response does not have sudden dips at some frequencies. I only considered some of these parameters in the design of the crossover of the speakers I am using now and that was painful enough.

 

[Geert]

Normal people call this slot loaded, and it’s not all marketing. It basically lowers the fs a bit, so you get a bit more bass extension. It however does not control directivity.

In the . pdf brochure they refer to the slots, and/or the grid in the slots, as a "wave guide". Not sure what to think of that, as a slot results in a 180° wave front if I'm not mistaken. The HiFi-news article calls it ‘a cardioid acoustic-resistance configuration’. Although a bit further in the article they state "While very low frequencies are
largely omni-directional here, most of the energy is guided along the convex sides of the speaker, with only a small fraction transmitted directly through the rear, via the slits in the back panel". So it seems the slits in the back panel also play a role.

Crossover frequency between the back firing woofers and the mids in the front is 135Hz. Makes me wonder in what frequency range the system is cardiode.

 

[BvanHorck]

I heard the Ktema’s against the Sonus Faber Serafino, same room, source and amp. The Ktema blew the Serafinos away. No muddled mid, tighter bass