{"id":6373,"date":"2017-04-01T08:55:23","date_gmt":"2017-04-01T08:55:23","guid":{"rendered":"http:\/\/www.audioexcite.com\/?page_id=6373"},"modified":"2020-11-28T14:39:35","modified_gmt":"2020-11-28T14:39:35","slug":"kensho-two-m3","status":"publish","type":"page","link":"https:\/\/www.audioexcite.com\/?page_id=6373","title":{"rendered":"Kensho Two \u2013 M3"},"content":{"rendered":"

Updated 20170416!<\/span><\/strong><\/p>\n

Concept:<\/strong><\/span><\/h3>\n

<\/a><\/a><\/a><\/p>\n

Kensho Two \u2013 M3<\/strong><\/span> is a small sized 2-way stand-mount bass-reflex loudspeaker. It\u2019s ideal for small to medium sized listening room. The tweeter level can be fine-tuned according to personal preferences and taste.<\/p>\n

“Kensho” is Japanese for “seeing nature.” It means seeing one’s true nature; perceiving the self, but can also in Zen Buddhism mean “a brief experience of enlightenment”. <\/em><\/span><\/strong><\/p>\n

Loudspeaker driver units:<\/span><\/h3>\n

 <\/p>\n

Kensho Two \u2013 M3<\/strong><\/span> uses a 5″ mid-woofer and a 1″ soft dome tweeter from SB Acoustics.<\/p>\n

The SB15NRXC30-4 is a low distorting 4\u2126 mid-woofer with a coated Papyrus fiber cone.<\/p>\n

The SB Acoustics SB26STAC-C000-4 is a 4\u03a9, 1″ coated textile dome tweeter.<\/p>\n

For further details see:<\/p>\n

SB Acoustics SB15NRXC30-4<\/a>
\nSB Acoustics SB26STAC-C000-4<\/a><\/p>\n

Cabinet:<\/span><\/h3>\n

 <\/p>\n

The Kensho Two \u2013 M3<\/strong><\/span> uses a 11 liter \u201cDayton Audio\u201d enclosure. This is a very nicely built curved cabinet with a 25mm (1\u2033) MDF front-baffle. The enclosure walls are made of 18mm MDF as well as a 15mm brace from the bottom to the top. The enclosure net volume is approximately 10 liters (enclosure volume \u2013 drivers, filter and port).<\/p>\n

Cabinet drawing: Dayton 11 liters Curved Cabinet #302-711<\/a><\/p>\n

\u00a0Baffle drawing and driver unit layout:<\/strong><\/p>\n

<\/a><\/p>\n

Box simulation:<\/span><\/h3>\n

 <\/p>\n

<\/a><\/p>\n

Bass-reflex 11 liter Fp=43Hz
\n<\/strong><\/p>\n

-6dB = 37Hz
\n-12dB = 32Hz<\/p>\n

Bass-reflex port:<\/strong> 45x155mm<\/p>\n

Impedance measurements:<\/span><\/h3>\n

 <\/p>\n

<\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Blue:<\/strong> Left loudspeaker<\/p>\n

Green:<\/strong> Right loudspeaker<\/p>\n

Minimum impedance of 3,28 Ohm @ 170Hz.<\/p>\n

Cross-over design:<\/strong><\/span><\/h3>\n

<\/p>\n

The Kensho Two \u2013 M3<\/strong><\/span> have an acoustical fourth-order Linkwitz-Riley (LR4) filter topology.<\/p>\n

The mid-woofer cross-over filter section is an electrical third-order and consists of two coils and a cap (L3+L4+<\/strong>C4<\/strong>) that shapes the cross-over slope to\u00a0an acoustical LR4 roll-off with a targeted 2.1kHz cross-over point. The mid-woofer cross-over filter section also have a frequency response shaping circuit (C5+L5+R<\/strong>4<\/strong>). The L3<\/strong> and L4 <\/strong>coil should have a summed total series resistance of 0.4 Ohm +\/- 0.1 Ohm.<\/p>\n

The summed resistance of the L5<\/strong> coil and R4<\/strong> resistor should have a summed total resistance of 11.38 Ohm +\/- 1 Ohm.<\/p>\n

The tweeter cross-over filter section consists of two resistor (R1<\/strong>) and\u00a0(R2<\/strong>), together with a third-order electrical filter (C1 + L1+C2<\/strong>) that shapes the cross-over slope to an acoustical LR4 roll-off with a targeted 2.1kHz cross-over point. (C3+L2+R<\/strong>3<\/strong>) flattens out the tweeters impedance peak at the resonance frequency and it\u2019s necessary in order to shape the filter to a LR4 filter slope.<\/p>\n

Mid-woofer frequency response shaping circuit:<\/strong><\/p>\n

<\/a><\/p>\n

Tweeter frequency response shaping circuit:<\/strong><\/p>\n

<\/a><\/p>\n

Cross-over simulation:<\/span><\/strong><\/h3>\n

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<\/a>
\n<\/a><\/a>
\n(click on picture to zoom)<\/p>\n

Top:<\/strong> 15deg off-axis frequency response.<\/p>\n

Left:<\/strong> 15deg off-axis frequency response, reverse polarity.<\/p>\n

Right:<\/strong> Individual driver unit phase tracking.<\/p>\n

The reverse polarity simulation shows a deep reverse null indicating an excellent phase tracking between the two driver units. The tweeter has a rising response above 12kHz.<\/p>\n

Frequency measurements:<\/span><\/h3>\n

 <\/p>\n

The following frequency measurements of the finished loudspeaker are made at a 2m distance.<\/p>\n

All frequency response charts are presented in a 50db scale with 1\/24 octave smoothing and the measurements are valid down to 375Hz.<\/p>\n

<\/a><\/a>
\n<\/a><\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Upper Left:<\/strong> On-axis frequency response @ 2m.<\/p>\n

Upper Right:<\/strong>\u00a0On-axis frequency response, tweeter reverse polarity @ 2m.<\/p>\n

Lower Left:<\/strong> 15deg off-axis frequency response @ 2m.<\/p>\n

Lower Right:<\/strong> 15deg off-axis frequency response, tweeter reverse polarity @ 2m.<\/p>\n

The dip around 3.5kHz is caused by baffle diffraction and smooths out in the off-axis frequency responses.<\/p>\n

<\/a><\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Left:<\/strong> On-axis, 15 and 22.5deg off-axis frequency response @ 2m<\/p>\n

Right:<\/strong> 30, 45 and 60deg off-axis frequency response @ 2m<\/p>\n

 <\/p>\n

Baffle Step Compensation (BSC):<\/strong><\/p>\n

The following near-field frequency measurements are made at a 0.25m distance at woofer-axis. The measurements are valid down to 140Hz.<\/p>\n

<\/a><\/p>\n

(click on picture to zoom)<\/p>\n

Blue:\u00a0<\/strong> Mid-woofer frequency response without cross-over.<\/p>\n

Red:<\/strong>\u00a0 Mid-woofer frequency response with cross-over.<\/p>\n

This near-field frequency response plot shows the mid-woofer cross-over effect on the loudspeaker baffle step.<\/p>\n

Distortion measurements:<\/span><\/h3>\n

 <\/p>\n

Measurement setup:<\/strong><\/p>\n