Modern mid-size Karlson: the SK8

[IG81]

Built according to the plan laid out by members of the Karlson forum as well as other K-builders, is the SK8 koupler. I built it to use with my Philips AD9710 fullrange drivers. It remains to be seen if they will work well in there, if they don't, I will likely get some FE206EN, as they worked very well in freddy's example.















IG

[ultrakaz]

Thanks for posting your build. The Karlson is a cab that I've wanted to build over the years but never got around to it. The size of the original for the 15" is a bit daunting as I already have too many large speakers. The SK8 is much more manageable. Please post your impressions/comments on the SK8 and if you have heard the K15, does the SK8 have that Karlson punch(?).

[ultrakaz]

Oh yeah, great pictures, though the first few seem to make the SK8 look like it was built in the floor(!).

[Nanook]

mainly because of the very nice build (and are SO much nicer than anything I can do). Very nice. I've often thought about Karlson enclosures. I bet the Pioneer B20FU20-51FW would be fun (if parameters are suitable , I know nothing about K-slots and the desired parameters..) if eNABLed with a coax tweeter added if need be.

[IG81]

Originally Posted by ultrakaz

Oh yeah, great pictures, though the first few seem to make the SK8 look like it was built in the floor(!).

I thought the same when I first looked at this pic where the back of the curved reflector, made of oak ply almost blends with the floor.

While I have not heard K15, I have my K12 which have a nice punch with mid-Qts Richard Allan CG10T. Karlson usualy will do better with lower Qts, stronger motor, low Mms drivers, which I cannot I have tried yet in a larger K. I did not expect the high-ish Qts AD9710 to be perfectly at home in the 1.88cf SK8 as it did quite well in the 3.27cf K12. Will see how much tweaking it will take to make it sound decent if at all possible. Plan B is either FE206EN or AN Super8 CF.

IG

[IG81]

Originally Posted by Nanook

mainly because of the very nice build (and are SO much nicer than anything I can do). Very nice. I've often thought about Karlson enclosures. I bet the Pioneer B20FU20-51FW would be fun (if parameters are suitable , I know nothing about K-slots and the desired parameters..) if eNABLed with a coax tweeter added if need be.

BOFU might lack top-end behind the wings, so a HF supplement might be good, either K-tube for the purist, or a coax tweeter, or a suitable horn on top, with a good blend to the Karlson.

IG

[freddi]

- ran a genuine BOFO in a "K10" size coupler and it sounded pretty good with a Karlson open ended waveguide on top. SK8 is little - going taller with the same footprint might give more punch

[Greg B]

I bet the Pioneer B20FU20-51FW would be fun (if parameters are suitable

The parameters are not suitable. Try them in a TQWT, BIB, etc.

The SK8 is more suited to the Fostex FE206EN, or a driver with similar specs.

Frankly, Karlsons get trickier as they get smaller. IMO it's better to build a K15 or K12 for a first one.

[kenpeter]

Fig 6 curved reflector focuses to a horizontal line,
but exit between the K wings is a vertical line.
this will emphasize frequencies where horizontal
high order mode has a hot spot in the center.

If you make two curved reflectors face each other,
such the profile looks like a cukoo clock or old radio.
Then the focus becomes a vertical stripe, and won't
matter so much where the hotspot occurs, anywhere
upon the focus line will line up with the front exit.

You still need a wedge or scoop in there to knock any
sounds out that might otherwise resonate in a front to
back parallel wall mode. Though this is a much shorter
parallel wall problem than side to side modes were.

Three curved walls would be even better for purpose
of detuning high order junk, but the upper chamber
then becomes too small. We don't want to change
the original upper chamber internal volume so much.

I thought my Fig 666 was a good compromise? The
wings and back are better braced too. But nobody
has ever attempted to build one that I know of.
I am not in a favorable situation for woodworking
to test this theory anytime soon.

[freddi]

A rough estimate of rear chamber size for moderate qts driver might be (Vas*fs*qts)/50 - without 9710 specs at hand I'd guess it would want ~K12's rear chamber volume. FE206EN in the Karlsonette is very punchy, FE206EN in SK8 is light on bass but very good in mids and highs. Somewhere there's a sweet spot for FE206EN and we've not quite hit it yet. The taller version of SK8 was prototyped and run in two configurations with the builder John Lapaire favoring the version based on Greg B's SK6.5 idea. I wonder how SK8 would do with FE166EN - ?

HAK8 thread (High Aspect K8) with pix and some measurements - JL thinks its got enough punch. GB's six inch K-coupler (which is about the same bulk and size as SK8) was roughed out too and under tweaking http://gainclone.com/Karlson/index.php?topic=1299.0

HAK8 and SK6.5 next to K15 Neither HAK8 nor SK6.5 have upper reflectors as their vents are at the very top of the front chamber.