Speakers better without subwoofers? Crossover and synchronization issues? What do you do

@emergingsoul I do believe that is a Franco Serblin stunt. What they are doing is relieving the front woofers from having to make long excursions which lowers their distortion dramatically. This is what subwoofers do when used with a two way crossover and not just the low pass filter installed in most subwoofers. These added woofers are almost subwoofers. That speaker is capable of prodigious volume and they would normally require at least two 15" subwoofers to keep up in terms of getting down to 20 Hz with the required boost. You could probably EQ the Fabers to make that kind of boost, but you would not be able to play the system very loud. So, the internalized low frequency woofer is more a solution to lowering distortion than it is for extended and powerful low frequency reproduction. I have a friend who has Franco Serblin K'temas that do the same thing and they are wonderful sounding loudspeakers. Franco eventually left Sonus Faber to start his own company. He passed away not long ago. Do the K'temas require subwoofers? This depends on your view of the universe. My friend says no. I say yes, but I would cross much lower than I usually do. Large spaces breath at low frequencies. Even with your eyes closed you can tell you are in a large space. You can feel it. Many recordings of live performances have enough of that information present to fool you into thinking you are in a large space, if your system can reproduce it. My system is down 6 dB at 16 Hz, The subsonic filter is at 10 Hz 14th order. From a simplicity perspective my friend's solution is superior. It is much easier to screw up a system with subwoofers than it is to make one better and most subwoofers are not what I would call high fidelity. Have a look at this https://imgur.com/gallery/building-resonance-free-subwoofers-dOTF3cS

@mijostyn 

Impressive reply. And very helpful.

Curious that you cannot biwire,biamp ktemas which is sad. They don't want you messing around back there with their crossovers.  

I did look at the ktemas, very very heavy not terribly expensive in the scheme of things.

The friend drives his K'temas with a Bricasti Design M25 and I have not heard a dynamic speaker sound better. In this regard I would not change a thing. Up against speakers like Magicos and Wilsons they are dirt cheap and an amazing value. I also think they are cool looking. I also would not add a subwoofer unless you were going to do it right, which means a digital processor and two of the best DACs

@knotscott - I agree with everything you said, and one thing people tend to forget is that when the main speakers can run full range, its probably a good idea to use most of that range on the main speakers, unless you are having problems getting loud enough with the current amp speaker combo. Sometimes cutting the mains back to 80 Hz will reduce distortion in the upper bass because the lower frequencies and increasingly larger cone excursions that go with them tend to raise overall distortion on that low frequency driver in the mains. But its something definitely worth testing if there is any question. For my own part, most of my speakers are full range so the crossovers to the subs get set around 40 hz or so...and then its time to do some level matching to get the subs integrated. Not to hard if you are systematic about it. Just time consuming.

The second reason to set that crossover as low as possible is to retain the directionality of the bass from the mains as much as possible, maintaining coherency, phase, etc. At very low frequencies it probably doesnt matter, but at midbass frequencies it very much does matter

When I first tried to set up my sub (REL T9), the result was a hot timing mess, so I let it gather dust. Main speakers are PearlAcoustics Sibelis SG. A year later I gave it another go, and got it to work where the sub is not audible directly, but I notice the difference turning it on on/off. I have no clue what I did differently. I am not interested in window-rattling bass, am actually rather bass averse, yet a bit of low frequency condiment makes the overall musical experience more tasty.

I would venture to guess that the allure of a sub is BASS!!! and that leads to bad quality sound. After all, when spending money you want something for it. However, restraint is key to success. Less is more.