Model: Blocku Doku
Type: Four-way large, separated and fully customizable loudspeaker
Enclosure type: Bass-reflex
Woofer driver unit: Eton 11-612/C8/50 RP paper cone
Midwoofer driver unit: Scan Speak 18w-8531g00
Mid driver unit: Scan Speak 12mu-8731t00
Tweeter driver unit: Bliesma T25S-6
Frequency response: 30-25000Hz -3dB
Sensitivity: To Be Defined with passive oxvr
Impedance: 4 Ohm
Overall Enclosure dimensions: (height x width x depth): 1135 x 300 x 436 mm
Concept:
The idea comes from my visit to the Audio Show in Warsaw 2022. In fact I went there to find inspiration and what design brings the sound I like. My favorite sound is: full – meaning from very bottom to the top(min 30Hz bottom end), fast bass (I enjoyed deep and slow hip hop bass when I was young and I have enough of it:) ), even SPL – no ups and downs, limited directivity (sitting in one specific point to have good phase response is NOT for me), smooth and delicate sound (mainly paper membrane).
Above characteristics were shown by speakers with more than 2 way drivers, big enclosures and great paper based transducers. Examples:
Loudspeaker driver units selection
target frequency band to cover = 2,5kHz and up
Bliesma T25S-6
http://www.bliesma.de/Datasheet%20T25S-6.pdf
Small 19mm covered silk dome which gives reasonably good transparency and damping. Always wanted to try Bliesma. They are well made and tiny, really tiny. This makes them look like Focal design.
target frequency band to cover = 0,2kHz – 2,5-2,7kHz
Scan-Speak 12MU/8731T00
The best sounding neutral midrange I had. Some may say that it is boring but I love it!. Blends well with other paper drivers. It has a reasonably flat cone which makes it easy for phase alignment.
Madisound recommends: a 2 liter sealed enclosure, loosely filled with wool. Your F3 in this enclosure is 185 to 200Hz, depending on the amount of stuffing.
target frequency band to cover = 0,8kHz – 1,5kHz
Scan Speak 18W 8531G00
I want to make it a closed box. To support the bass driver with a quick kick.
Troels uses it in SP38/13 in 22 liters.
target frequency band to cover = up to 150-250Hz
Eton 11-612/C8/50 RP
I was looking for an approx 30cm bass driver that will go well in Bass Reflex design, will be reasonably fast and will deliver high SPL.
Bass reflex design – Suggested Box Alignments:
Madisound:
43l vented with a 3″ dia x 9.5″ long vent for a F3 of 38Hz
56l vented with a 3″ dia x 8.8″ long vent for a F3 of 35Hz
Some experiments:
- Closed box
34l internal volume, lightly damped
Quick and responsive bass.
- Vented box
34l Bass reflex
BR size 6,8 x 22cm
-3dB 43Hz
Nearfield measurements result from an experimental box.
Black = Closed Box, Red = Bass Reflex Box.
My final conclusion is to go for a smaller bass reflex box with low tuning.
Version 1
V = 50l
Fs = 23Hz
Vent rectangle = 2,5 x 35 x 190cm
-3dB 43Hz
-6dB 32,5Hz
Version 2
V = 50l
Fs = 27Hz
Vent rectangle = 2,5 x 35 x 136cm
-3dB 39,69Hz
-6dB 31,73Hz
This is the selected version.
In making
Sound center alignment
Results for the boxes sloping:
- 200cm distance, 98cm height listening position cabinets setup:
92mm bass
42mm midbass
32mm mid
23mm tweeter
- 280cm distance, 98cm height listening position cabinet setup:
72mm bass
42mm midbass
22mm mid
22mm tweeter
Measurements
Measurements results:
Measurements for xovr design 2m distance, microphone on the height of tweeter
Bass Eton with directivity 0;10;20;30;40;60 deg
Impulse response
Impedance
Nearfield bass speaker = RED, Bass Reflex = BLACK
Nearfield bass speaker = RED, Bass Reflex = BLACK, with active xovr 200Hz 24dB/oct
Midbass 18W with directivity 0;10;20;30;40;60 deg
Impulse response
Step response
Impedance
Midrange 12MU with directivity 0;10;20;30;40;60 deg
Impulse response
Step response
Impedance
Tweeter Bliesma with directivity 0;10;20;30;40;60 deg
Step response
Impedance
Active design using SURE Wondom JAB4 amplifiers
This is version 21 (yes 21) after a lot of measurements and tests. Very nice and even sound.
Block design with parameters from Sigma Studio
SPL measurements results 2,8m distance
Impulse response
Passive crossover simulation
VituixCAD https://kimmosaunisto.net/
Now assembling the xovr to make the tests and listening.
RESULTS
Unfortunately I lost a lot of time and money.
I did a bad import to Vituix by uploading the .txt files from CLIO. I was looking for an error for days. Eventually I did it according to the manual from Vituix by importing chirp files. Basically the result should be the same but it’s not.
This the result:
Disaster in 4-9kHz region.
Additionally it was one more disaster in impedance – min 2.6Ohm, average 3.5 Ohm.
One more time
In fact, it took 5 iterations to get to this point. Number of hours of listening, testing, measuring. This is why good designs cost so much…
Ok, this is the final result for crossover:
I am super happy with this crossover.
Great speakers division, impedance on average 5 Ohm, very linear.
And now comes the game changer. I did alignment of the speakers – that was the idea for the Blocku Doku name. You can move them as you wish, adapting to the room, distance, phase.
The result in my room is super! Check the measurements: super flat, good phase alignment, tonal balance.
+/- 1dB variance for complete listening range!
inverted MID
Inverted tweeter
inverted MidBas
RESULT: I love those speakers. I worked for this result for many many years!
They even look nice!
