C17WH-16-08 + DT300WG
built by Aake, Sweden

Hej Troels!
Nu har jag provspelat mina C17 högtalare, och dom låter helt fantastiskt. Har bara spelat några timmar ännu, men de spelar redan skjortan av mina audiovector K3. Var uppe till kl:2 i går natt skulle upp 07.00 kunde inte sluta. Dom verkar passa mina Audion 300B monoblock perfekt.
Åter kommer med lite bilder om du är intresserad.
Mvh Åke

Thanks a lot to Aake for the report and pics. I wish I had a pair of these 300Bs. My translation below.

(I'm in the process of testing my C17 speakers and they sound just great. Only a few hours old, they leave my former Audiovector K3 far behind. Was up until 2am last night and just couldn't stop. They seem to fit my Audion 300B amps just perfect. I'll mail you some pics if you're interested. Regards Aake.)

As can be read at C17-III, Aake pointed to some problems with the tweeter and the notch filter was changed to make an overall flat impedance, and the level at 500 Hz was reduced further to some 35 dB below average level.
After the mods, Aake made these notes:

Nu har jag provat nya filtret och det blev en klar förbättring, inte bra på lite högra ljud volymer utan även på låg volym. Diskanten spelar helt enkelt lite renare.   Nu när jag har lyssnat på högtalarna ett tag och räknar med att de är inspelade så har jag kommit fram till följande. Det som är riktigt bra med högtalarna är framför allt upplösningen och ljudbilden där djupet är helt suveränt. Högtalarna passar perfekt till akustisk musik.   Det som är mindre bra är basen, som i och för sig är snabb och ren, men spelar lite väl lågt och inte speciellt djup, vilket gör att det låter lite klent. Brukar använda min subwoofer för att få lite mer tyngd i basen, speciellt när jag spelar rock musik. En annan nackdel som bara inträffar när man vill spela lite högre, är att ljudbilden faller sönder och smetas ut.

My translation:
I have now tested the new filter (-for the treble) and this is a clear improvement, not only at fairly loud levels, but also at low levels. The treble is simply cleaner. I have now been listening to the speakers for some weeks and assume they are fully broken in, and this is my conclusion: What is really good with these speakers are first and foremost the resolution and depth to the soundstage. These speakers are perfect for acoustic music. What may be limiting is the bass, which is fast and clean, but may not reach particularly deep and lead to some compression. If I add my subwoofer I get more low-end extension and weight, in particular when I play rock music. Another disadvantage, which occur when you play loud, is that the sound starts compressing and details are smeared.

My comments to Aake's notes:
Thanks for Aake for his notes and I'm not surprised. My younger friend, Martin, came by the other day to hear my latest speakers and Martin usually brings some - well, really difficult CDs, like heavy metal and contemporary rock music, which we play at really loud levels and he was quite surprised to hear the C17-III dealing so well with some of the well-recorded heavy stuff. So much, he's seriously considering building a pair to supplement his Point75s, realising that no speaker does it all.

The C17-work and comments from Aake will bring some writing soon on how we choose speakers and how we "read" a speaker construction in order to suit our needs. In the case of the C17, we have lightweight paper cone drivers with a Fs of 50 Hz and we have a sensitivity of 95 dB/2.8V from a 35-40 litres constructions and the experienced speaker builder will soon know what this means in terms of bass extension. The 1st order filter will also tell that the overlap between drivers is huge, which limits the possibility of playing e.g. rock music at excessive loud levels. What is does bring is the magnificent midrange of the C17 drivers and an unusual level of transparency thanks to the simplicity of the crossover. We are into SET low-wattage amp, high-efficiency paper cone, one-cap territory here and we have to know the pros and cons..