Project Description of My Speakers

I want to share more info about this speakers because, after years of experimenting with various types of acoustic design, I have achieved the sound I like. I am proud of this system, and I am confident that it will sound great anywhere.

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Philosophy and Drivers

My approach to sound might be considered somewhat old-school. I believe that nothing has surpassed paper cones, while modern alternatives are often more about impressive data sheets rather than preserving the original sound. We listen to sound, not numbers. You could call me a fan of the golden age of audio from the 60s and 70s, a time without digital sound, loudness wars, and excessive post-processing. The approach back then was more responsible and meticulous, resulting in timeless music like Pink Floyd's "Money," "Time," and others.

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Since I mentioned the material of the cones, let's talk about the drivers. It all started with an 8.5-inch custom full-range driver made by Zsolt Lajcsák (Жолт Лайчьак)  in Serbia, to whom I am very grateful. He selected the right paper for the driver to achieve the desired sound. We discussed every nuance and detail extensively, and his expertise allowed us to reach the result I wanted. These drivers feature a large electromagnet, requiring a power supply. This design not only sounds different from permanent magnet drivers but also allows for fine-tuning the sound with the power supply depending on the acoustic design used. Before these open baffle enclosures, I also made transmission line enclosures for these drivers, which was an interesting project with unique sound. Ultimately, I concluded that these drivers should not be confined to any box and needed an open baffle design.

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Integrating the Bass

A logical question arises: where does the bass come from? While these drivers can play quite low, they can't cover the entire frequency range from 20 Hz to 20 kHz. I considered several candidates for bass support. Initially, I looked at Acoustic Elegance drivers, specifically designed for open baffle with appropriate characteristics, but they had two downsides: high moving mass and cost, along with long shipping times from the USA. Then, I discovered the new Bianco OB series from SBAudience, which met all criteria even better.

After receiving all the drivers, I built several prototype enclosures, conducted numerous measurements and listening tests to find the best way to integrate them, ensuring the full-range driver's character wasn’t lost and the bass complemented it seamlessly.

 

Crossover Design

I started with a classic crossover design, but the result was disappointing as it lost the original magic of the full-range driver. In discussing this with a fellow engineer, he suggested a simple yet challenging idea: leave the full-range driver unfiltered, allowing it to play its entire range, and integrate the bass and midrange from below and above, respectively, with crossovers designed to overlap at the natural roll-off points of the full-range driver in the open baffle design. This approach required extensive measurements, checks, and adjustments to find the optimal crossover points and ensure a coherent sound.

 

Super Tweeter

I decided to add a super tweeter to fully cover the audible frequency range, achieving 29 Hz to 25 kHz (25 Hz to 26 kHz at -3dB). I had three criteria for the tweeter: silk dome, directivity, and sensitivity. The choice was between Audax and Fostex, with Fostex winning due to its directivity, sensitivity, and even frequency response. This allowed me to position it 90 degrees upwards with a diffuser, filling the space with high frequencies without harshness. The super tweeter can also be adjusted!

 

Final Design and Construction

After the plywood prototypes (which ended up in the fire), I moved on to working with wood. There were several iterations before arriving at the final design you see now. All the work, from circular saw cutting to CNC machining, assembly, sanding, polishing, and final oil treatment, was done by me in my home workshop (which is also my garage in it’s previous life).

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Out of various wood options, I chose Suar wood. For the project, I ordered two large slabs, each 62 mm thick, cut to create one speaker with 35-degree angled sides, a top shelf for the super tweeter, and a base. The cut-out discs from the driver placements were also utilized: the larger ones became enclosures for the crossovers, and the smaller ones became shelves for the full-range driver power supplies.

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The final stage involved repeated measurements and adjustments to the crossover designs (currently on the seventh version) to account for the final baffle construction and driver interactions. The speakers operate in bi-amping mode: the bass section is powered by two self-made A/B class monoblocks, while the full-range driver and tweeter are driven by a custom EL34 tube amplifier made several years ago. This setup allowed for load separation between amplifiers, achieving the desired full-range driver sound and ensuring speed and control for the bass.

 

Conclusion

From the start of development to what you see now, the project took about four months. It’s still not entirely finished, with a few minor but necessary tweaks planned. These adjustments are mostly design details and should not affect the sound. Every aspect of this project, from sound to appearance, meets my standards, inside and out.

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Thank you for reading! In case of the the question you can contact me via website contact form!