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Category: Speakers

Mimì two way compact speakers

Many hears ago, in a Hi-Fi show, I listened the ProAc Response Two speakers and I was really impressed by their performance. These speakers just simply disappeared, leaving behind an ambient soundfield that changed very little with head movement. Driven by an excellent Audio Reserch tube pre/power amplifier, they had put the singer right here in the room with me!! Also all acoustic instruments like the guitars, violins, percussions were played with a breathtaking sense of 3-D realism. In last September I saw among ads sale two 6.5″ Scanspeak 18W8543 polypropylene bass/midrange drivers and two ¾” dome tweeters D2010  Scanspeak and remembering the previous ProAc listen experience ( Response two speakers were equipped with these drivers ) I thought….mmh…..why not?


To build the cabinet I choose 19 mm thick marine type plywood. To compensate the time delay tweeter-woofer emission I adopt a sloping baffle. Furthermore, I put  a 30x30mm battens in the internal rear perimeter to allow the removable rear panel ( to adjust crossover, damping and so on ). A 19x80x200 mm bracing is put between the two sides to minimize the box vibrations and silicone sealant on all internal edges to seal any micro cracks. The single front-mounted tuning port is a slot 12 mm height and width as a baffle ( 200 mm ). The total length is 140,2 mm. As you can see in the photos, the internal sides ( excluding the front panel and the bottom ) are coated with 30mm dacron fibre mat. In the tweeter cell crossover I suggest to use 5 W non inductive resistors  and MKP high quality capacitors as Mundorf, AuriCap, Multicap or similar. The coil for woofer cell MUST BE air wrapped, 1.4 mm Cu to minimize series resistance. For the other coil is sufficient 0,5-0,6 mm Cu diameter. The red soft carpet put in the baffle smooth out the 6 mm speaker edges.






New Crossover for K2 Klipschorn clone

During the last year of listening my K2 Klipschorn super clone speakers (info and specs here) I put the attention on some point to upgrade. I focused my attention on the crossover frequency on both low-mid and mid-high cells. After many weeks of listening session I found some benefits to lowered both crossover frequency.

The inductor in series to K33e woofer is now 8,2 mH ( old value 3,6mH ) put in a separate plastic case very near the woofer, and the capacitor in series with Gauss HF 4000 driver is increased now to 68 uF ( two paper in oil capacitors 66uF + 2 uF in parallel ).


The mid-bass region is now clearer and the dirty, muddy of K33e break up cone less unpleasant. The 0,25 mH inductor in the mid cell lowers the cut of frequency of mid-high range and the 3636 autotransformer is set to -6dB of attenuation for the Gauss HF 4000. In the high section, I increased to 1 uF the capacitor and I put a 8 ohm L-pad for the tweeter Coral 104 to optimize the audio level.

I found some benefit to adopt the dielectric polarization technique in this section, instead of 1 uF capacitor I put two 2 uF capacitor in series with a +9V bias pole battery in the common point ( see JBL, Infinity…, on their best crossover a DC bias is used on capacitors to reduce the effects of dielectric absorption ).

K2 Klipschorn (super) klone…

This is my reference speakers……
I heard hundreds of speaker systems but at last….I always return at my Klipschorn super clone. Why super ? OK bass bin is almost identical to original Klipschorn, also fitted with original K33E Klipsch woofer but mid-high section is very different.



I use high-end expensive component like Gauss HF4000 as midrange assembled with JBL 2350 aluminum horn. Gauss HF4000 2”compression drivers are very impressive components: heavy (13 Kg ), alnico magnet, large aluminum diaphragm, wide frequency response ( 500 to 15.000 Hz ) excellent matched with JBL 2350 40×90 radial horn with 220 Hz taper cutoff frequency. This excellent heavy ( 16.3 Kg ) aluminum horn measure 80,3 x 50,8 x 20,3 cm and so match very well with size of bass cab Klipschorn. For high range I chosen the Coral H-104 horn tweeters.
This big ( 3.5 Kg ) alnico tweeter is mounted in the same vertical plane of the Gauss driver diaphragms for best time alignment mid-high response. The crossover filter is an variant of Klipsch type-A. I choose first order slope crossover for his best sound. I tried various crossover type also electronic ( tube and solid state ) but I returned back to the simplest 6dB/oct in the schema. Be carefuI on quality components: for mid-range I use paper in oil capacitors, in the high section copper MKP I found has more detailed sound. 10 Ohms resistor must be metal/oxide 1%, 10W. The 3,6mH inductor for low pass filter must be high quality, low RDC, ferrite ( or best transformer ) core with almost 1,4 mm copper section.
Mid range level , due very efficient Gauss driver, must be attenuate with an autotransformer ( like model 3636 from B&K Sound ). In my system I use pin 0-5 as input and 0-3 as output. These speakers have a first rate SPL factor. 3 W of 2A3 SE tube amplifier, are sufficient to produce a powerfull, open, deep sounstage. It is very difficult for any speaker to play music as a live session….. these speakers are among the very few that succeed in this uneasy task.