Mid size 8" Karlson coupler for fullrange

[freddi]

built for me by John Lapaire will examine several aperture including these two wildly different scenario and impedance openings suggested by Carl Neuser. This coupler's hieght is 20" Carl has a 26.5" high coupler with Fe206E. In accordance with Karlson patent 3540544 it features a curved upper reflector, and its rear lowpass choke shelf is variable. There's a slight stub to the shelf to allow adding an incremental front deflection shelf.






Slow taper


Slow taper parameters - 83.6 square inch total aperture

Gap Slope p q Area Length Wmax
0.25 1.5 3 12 83.6 18.5 12


x w
0.00 0.50
1.00 0.50
2.00 0.52
3.00 0.55
4.00 0.62
5.00 0.74
6.00 0.92
7.00 1.16
8.00 1.49
9.00 1.91
10.00 2.43
11.00 3.07
12.00 3.84
13.00 4.74
14.00 5.78
15.00 6.97
16.00 8.29
17.00 9.73
18.00 11.24
18.50 12.00

********************

Fast taper


Fast taper parameters, 131.9 square inch aperture

Gap Slope p q Area Length Wmax
0.5 2.9 1.08 9.5 131.9 18.5 12



Aperture
x w
0 0.50
1 0.78
2 1.10
3 1.43
4 1.76
5 2.11
6 2.46
7 2.81
8 3.17
9 3.54
10 3.91
11 4.30
12 4.72
13 5.18
14 5.73
15 6.43
16 7.38
17 8.72
18 10.69
18.5 12.00

back of cabinet

[GM]

Sweet! Looking forward to your findings!

GM

[Scottmoose]

Looks good to me too.

[j.michael droke]

Hi there: The box and coupler look fantastic. Is the total box volume about 1.5 cf and the back volume (behind the driver board and curved panel) about ).7 cf? How is the back volume calculated from driver T/S parameters? Is the 0.5-inch x 12-inch gap calculated as a port? Hope you will post your listening experiences. ...regards, Michael

[freddi]

hi Michael - you've got a keen eye - that's about the rear volume and that slot will be the rear port - hope its large enough. I had someone's ancient 8" driver coupler laying around about this size that have pretty good impact on a drum. K-builder Carl gives a rough estimate of rear chamber volume to be (Vas*Qts*fs)/50

Carl doesn't post nor give out full details - here's an old Sigma coupler with a 2/3 height slot and another 8"/10" coupler (perhaps 28" tall) with laminated veneer K-tube waveguide. He has a 26.5" tall coupler for FE206E with the same cross-section as the test box being built for me but not seen a picture yet.

radial arc wings will be tested on mine along with those two extremes. I think the fast flare aperture may work with weaker drivers such as B20. Tighter and slower flaring apertures add more mass load so require stronger motor.

Best, Freddy

[freddi]

Here's fresh pictures of 3 apertures for the coupler - I'd expect the fast opening to work with weak motor fullrange (B20?) thanks to John Lapaire for great and patient work.

[borispm]

Can anyone tell me how the Karlson coupler works? It seems to be a pretty popular and successful design long long time ago. Very hard to find the explanation though. It seems to me there are 2 resonators ( 2 chambers)

[freddi]

radial wings in place

FE206EN/etc. coupler on top of John Lapaire's K15 home/pa system

[bentoronto]

Hey Freddi, are you sure that isn't a Tapped Horn?

If I recall my 1957 15 inch, some parts were shellacced and the only damping was a curved segment of paper-covered kapok (ancient house insulation batt?) stapled on the floor of the chamber behind the driver covering maybe 1/2 of the surface.

What a cello sound! Organ music too, at least for E. Power Biggs' low notes of the time.

[freddi]

re: tapped - have to ask Tom Danley on that one but K15 might be looked partly as one with a short path. I've built an 18" driver sealed rear chamber "klam" and as there's no rear wave contribution its working as coupled cavity. Karlson and Wayne Green's K15 had 3 damping pads with the thickest pad under the rear lowpass shelf.