KS-1804 mk2

mk2/IMG_1258.JPG mk2/IMG_1269.JPG

Introduction
Enclosure
Crossover
Simulations
Measurements
Sound
Summary


Introduction

KS-1804 mk2 is finalized version of KS-1804 prototype.

Technical specifications

General 3-way, resistance enclosure WW,
horn-loaded MTT
Dimensions WW: 490 x 940 x 533 mm (W x H x D)
MTT: 490 x 455 x 592 mm
Volume WW: 90+90 liters
X/O frequencies 420 Hz and 6500 Hz
acoustically 18 dB/oct and ~30 dB/oct
Drivers BMS 18N840
BMS 4590 + SL250-2, front
BMS 4550-16 + SL600-1, rear
Impedance 4 / 13 ohm (WW / MTT)
Sensitivity MTT: 100 dB/2.83V/1m
Plate amp Hypex PSC2.700d


Enclosure

mk2/IMG_1242.JPG

mk2/IMG_1238.JPG mk2/IMG_1239.JPG

mk2/IMG_1251.JPG mk2/IMG_1255.JPG

mk2/IMG_1259.JPG mk2/IMG_1261.JPG

mk2/IMG_1231.JPG mk2/IMG_1265.JPG

Enclosure drawing: KS-1804mk2.pdf


Crossover

Crossover is semi-active.

Woofer section

Low-passed and equalized with Hypex PSC2.700d.
mk2/KS-1804mk2-WW_Gain-LF.png

Upper BMS 18N840 has lattice all-pass filter to produce about 86 mm delay, compensating different distances from woofers to listening point (upper woofer is closer). Phase alignment improves integration around lower X/O frequency.
KS-1804_XO_WW.GIF

Horn section

High-passed and fine equalized with Hypex PSC2.700d.
Left:
mk2/KS-1804mk2-MTT_Gain-HF_L.png
Right:
mk2/KS-1804mk2-MTT_Gain-HF_R.png

Horn unit has also passive crossover including rough equalization for mid-range, sensitivity dropping from 115 to 100 dB/2.83V/1m and high-pass for rear tweeter.

Filter schematic of horn section:
mk2/KS-1804mk2_XO.GIF

Capacitors: MKP, 250 V or more

Coils (by AlphAudio):
L1021, L1041; air core, wire 1.00 mm
L2021, L3021; air core, wire 0.71 mm

Resistors:
R1021, R2011, R3011: 10W
R1041, R1051, R2031; 5W

Passive filters are located in woofer cabinet on the back side.
mk2/IMG_1247.JPG

Terminals from left to right (both speakers):
- Front horn midrange (outer/front terminals of BMS 4590).
- Front horn tweeter (inner/back terminals of BMS 4590). Polarity is reversed by speaker cable!
- Rear horn tweeter (BMS 4550).
mk2/4590+4550_cabling.jpg

PSC2.700d connection

mk2/PSC2700d_connection.jpg
Single pair (red & black) is connected to 'High channel' of PSC.2700d (upper UcD700). Red to red, black to black.
Double pair (red+magenta & black+cyan) is connected to 'Low channel' of PSC.2700d (lower UcD700). Red+magenta to red, black+cyan to black.

DSP settings for Hypex PSC2.700d

KS-1804TA_20140101.dsp

Preset #1 is for "Left channel" where front horn is on the right and rear tweeter is back left corner:
mk2/Left_horn.jpg

Preset #2 is for "Right channel" where front horn is on the left and rear tweeter is back right corner:
mk2/Right_horn.jpg

Simulations

Frequency response of horn section

RMS sum -45...+45 deg (black), on-axis (magenta) and off-axis
- measuring distance 170 cm, mic elev. 110 cm
- time window 6.0 ms, no smoothing
Left:
mk2/KS-1804mk2_FR-simu_170cm_-45+45deg_6ms_L.png
Right:
mk2/KS-1804mk2_FR-simu_170cm_-45+45deg_6ms_R.png


Measurements

Frequency response

On-axis response; Left, Right
- measuring distance 230 cm
- time window 5.6 ms, no smoothing
mk2/KS-1804mk2_FR_230cm_0deg_5.6ms_th_L+R.png

Directivity pattern horizontal 0...180°, steps 5°
- measuring distance 175 cm, mic elev. 100 cm
- time window 6.00 ms, smoothing 1/12 oct.
- Right channel
mk2/KS-1804mk2_DP1_175cm_6ms_hor.png

Same as previous
mk2/KS-1804mk2_DP2_175cm_6ms_hor.png

Average pressure red, axial blue
- measuring distance 170 cm, mic elev. 100 cm
- time window 6.0 ms
- includes 74 horizontal measurements
- Right channel
mk2/KS-1804mk2_Axial+Average_170cm_6ms_hor.png

Directivity Index

- measuring distance 170 cm, mic elev. 100 cm
- time window 6.0 ms, smoothing 1/6 oct.
- includes 74 horizontal measurements
- Right channel
Note! Vertical directivity increases total DI within 200...800 Hz
mk2/KS-1804mk2_DI_170cm_6ms_hor.png

Step response

- measuring distance 230 cm, on-axis
mk2/KS-1804mk2_SR_230cm_0deg_L.png

Excess group delay

- room measurement at 230 cm, on-axis
- time windows about 60 & 70 ms
- Left, Right
mk2/KS-1804mk2_GDx_230cm_0deg_60ms_L+R.png

Impedance response

Woofers
mk2/KS-1804mk2_ZR_WW.png

Horns
mk2/KS-1804mk2_ZR_MTT.png


Sound

See KS-1804


Summary

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Created 16.11.2013
Updated 11.07.2014