"Mechano22" - new version of a small 2-way speakers, with linear on-axis and power response characteristics.

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Not so long ago, I made a small 2-way speaker design with the following goals: f6 around 40Hz with  8 liters BR 45Hz enclosure, generally balanced on-axis response and close to linear frequency power response.

Experience gathered with that design led me to a conclusion that maybe it could be done a better and cheaper. And here is the new version, codemame "Mechano22". 

It is based on  relatively inexpensive set from Dayton: ND25FW-4 tweeter with waveguide and DSA135-8 midwoofer.

The box is really simple: rectangular 18mm birch plywood panels assembled (glued) with overlaps. Box dimensions: HxWxD: 290x174x263mm. The Box is filled with polyester fiber.

Pic 1. Box dimensions (mm)

The woofer has a flat basket edge, which, according to the manufacturer's note, allows application without flush so it wasn't implemented but there is a chamfer on the inner side of the mounting hole.


Pic2. System on-axis and power response characteristics in comparison with target lines. For power response calculation +-180deg measurements were taken in H and V planes (10deg step):



Pic3. frequency response for DSA135-8 (orange) and ND25FW-4 (gray):


Pic4. Crossover schematic:

Pic5. VituixCad, schematic and 6-pack for double check:


Pic6. Filters assembled on a scrap of plywood (for 1 unit):

Pic7. Units assembled (need sanding and waxing; the port visible in the photo was replaced with Monacor MBR-35 adjusted to 14cm length). 


Pic8. Mesured on-axis dBspl (both units, 5dB/div).  f6=40Hz if I did not messed up the measurements.

Pic9. Measured system impedance (both units).Nominal impedance is 6R (considering 5R minimum for 200Hz):
    
Following is a version of HP filter without the 100R resistor. So it can be removed but to keep +-1dB alignment with the target, C5 should be changed from 2.7u to 3.3u and r3 from 12R to 11R. This version wasn't implemented nor tested but should be ok.

Pic9. Optional version of the HP filter. 


List of components used (for one unit):

  • Dayton Audio DMPC4.3 / 4.3 uF / 5% / 250 V / Polypropylene capacitor MKP 
  • Capacitor Jantzen Audio CrossCap 0.47uF / 400VDC / 5% / MKP /
  • Dayton Audio DMPC8.2 / 8.2 uF / 5% / 250 V / MKP  2 pcs.
  • Capacitor Jantzen Audio Cross-Cap 9.1uF / 400VDC / 5% / MKP 
  • Dayton Audio DMPC-2.7 / 2.7 uF / 5% / 250 V / MKP polypropylene capacitor (3.3uF in the optional HP filter version)
  • Ty-Ohm ceramic resistor 22ohm / 22R0 / 20W 5% SQP 
  • Ty-Ohm  ceramic resistor 4.7ohm / 4R7 / 5W 5% SQP
  • Ty-Ohm  ceramic resistor 100ohm / 100R0 / 5W 5% SQP (omit this in the optional HP filter version)
  • Ty-Ohm 12ohm / 12R0 / 5W 5% SQP (11ohm in the optional HP filter version, or 10+1 or 2x22 in paralell)
  • Jantzen Audio core coil 0.68mH / cylindrical / 0.162ohm / dr.1mm Fe 0.021kg / dia.20, length 40mm / 
  • Jantzen Audio core coil 0.82mH / reel / 0.22ohm / dr 0.8mm Fe 0.056kg / dia.24 length 33mm / 
  • Jantzen Audio Air coil 3.7mH / 3.25ohm / dr 0.5mm / dia.33, length 15mm 
  • Jantzen Audio Air coil 2mH / 3.21ohm / dr 0.4mm / dia.31, length 8mm 
  • Jantzen Audio air coil 0.12mH / 0.26ohm / dr 0.7mm / dia.27 length 8mm 

VXP with off-axis measurments (+-180deg, H and V orbits): link

The measurements were taken with Clio Pocket measurement system using simple manual rotating table: link

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