tractrix horn

How I tweaked my full range Back Loaded horn speakers

Almost 4 years after the construction of my Back Loaded Horn speakers, I decided tweaked them adding tractrix horns using compression drivers for the high frequencies.
Searching the web and asking friends who had already experimented with such drivers, I decided to implement a structure based on a tractrix horn using an 1" (inch) High Frequency compression driver.
For this purpose I chose a cheap but very good European driver the BMS 4524. Another reason why I chose the particular driver was the low cost which is around 80 euro / pair , so I can comfortably experiment without wasting a lot of money...

According to the manufacturer (BMS) the 4524 driver achieves a linear frequency response up to 20 kHz, featuring 113 dB sensitivity 1 W / 1 m.
The specific drivers were placed in a pair of horns ( tractrix ).
I got the tractrix horns from Rainer Flock, model T 1040. The horns are made from solid maple. The diameter of the neck is 1 inch while the diameter of the mouth is 10.4 cm.

More info about the tractrix could be found at Rainer's web site.

Next step was the construction of the crossover. The crossover point is at 2600 Hz (1st order butterworth design). A 1st order crossover filters 6 db / octave and has good behaviour in transients. ( c1=7.5 uF L1=0.5 mH )
While not expecting the BMS driver is a diamond. The sound in my living room has changed completely. High frequencies became more clear, sweetest and most relief, while mid frequencies sound more plausible.
It is amazing that a budget less than 180 € You can upgrade a pair of BLH and listen even more quality sound.

costas sarris

acknowledgements :

  • Rainer Flo for his effort