XKi - X's ab initio Karlson 6th Order Bandpass

[freddi]

the size is good enough - how does power handling compare to W8-1772 in say a 2 cubic foot reflex/MLTL? I also have Beta8cx which might make something.

[xrk971]

The Beta 10CX can go into the same 60 liter box that the W8-1772 uses but with slightly longer vent of 9in. Should hit 110dB at xmax and f3 of 44Hz. In practice, I think the f3 goes down maybe 5 to 10Hz when actually used with a Karlson aperture.

Here is predicted SPL at xmax without Karlson aperture. The peak will flatten out and the HF's bandwidth will be higher.

[xrk971]

Originally Posted by freddi

the size is good enough - how does power handling compare to W8-1772 in say a 2 cubic foot reflex/MLTL? I also have Beta8cx which might make something.

For a direct comparison, if I remove the front chamber and K-aperture and let it operate as a bass reflex with the same vent, you can't drive it as hard. max SPL is now about 98dB at xmax.



As a comparison, from earlier post as a BP6, you can drive up to 9.2v and get 103dB:

[freddi]

thanks - that's a very useful comparison. What happens in the BP model if the rear chamber is reduced to 35 liters and tuning moved up a bit?

[EddieT]

X, you have hit the mother lode with this innovation. Your seemingly tireless effort and willingness to share with all is commendable. I am reminded of this comment you made a little while back.

Originally Posted by xrk971

. . . I should model this one day so we can all make tiny 4 inch K4's that reach 55 Hz!

Just from appearance it would appear that Karlson designed the front chamber to be fed at the apex of the angle, but if so he kind of blew it with the later K12 slots.

[freddi]

there was a point in the 1950's where distributed vents were popular among several manufacturers - perhaps due to Karlson enclosures being sold primarily without drivers and wide variance in driver characteristics, the distributed slot vent was chosen for K12 to allow a better overall fit. Fb at small signal was kept the same as the 1954 "Karlsonette" K12 which had a 15/16" high, horizontal slot vent bounded on the bottom by a rear lowpass shelf. Distributed vents like the later (perhaps 1956 onwards) K12, distort a lot if driven by sine wave. Karlson used a mix of "de-Q-ing holes" and a rectangular vent in several of the rare X15 systems seen. Besides XRK971's cool proof of concept mini XKi with Dayton, lets hope the diyaudio community finds other drivers appropriate for these BP alignments.

[xrk971]

Originally Posted by EddieT

X, you have hit the mother lode with this innovation. Your seemingly tireless effort and willingness to share with all is commendable. I am reminded of this comment you made a little while back.Just from appearance it would appear that Karlson designed the front chamber to be fed at the apex of the angle, but if so he kind of blew it with the later K12 slots.

Thanks for the kind words. I forgot I actually said that and it seems to have come true.

[xrk971]

Here is an example of this cabinet for a PA application using a B&C 8CXN51 coaxial driver. It makes for a pretty small cabinet with internal dimensions of 10in wide x 16in tall x 9in deep. With 0.5in ply, the external volume is exactly 1 cu ft. I modeled it using 18 liters active volume and added vent volume as well as driver volume. With a 10in x 1.0in x 15in long vent, the tuning freq fb is 56Hz with an f3 of 52Hz. This little box is capable of 112dB when driven by 32 volts to hit an xmax of 6mm.

Here is the sketch:



This is predicted frequency response of the just the band pass 6 before the Karlson aperture is added to smooth things out and allow HF's to escape:



Here is the vent velocity at max SPL in case you are concerned, just at the limit of what is acceptable - noise will be reduced as it is shaded by the K-aperture:



I think this may be a nice unit with even polar response over 90 deg full angle. This SPL is also suitable for use in THX certified HT applications.

[freddi]

wow!!! - wish their coax weren't so pricey - that is really punchy and compact - how about a beer budget version with Eminence's Beta8CX? - with ASD1001S as the compression driver, Beta8cx would be about 1/3 the price of the B&C

[xrk971]

Originally Posted by freddi

wow!!! - wish their coax weren't so pricey - that is really punchy and compact

The B&C stuff is top notch with a cast frame, Nd magnets, super durable thick paper cones treated for water repellency, and a surround and spider that lives forever. Don't forget this includes a nice compression driver for a complete system. Plus, they sound very smooth and nice. It's just money... I can't find a budget coax that will be this compact and deliver this much punch. For most music you wouldn't need a sub.