Karlson couplers - who is foolhardy enough to try them? - diyAudio
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Old 15th January 2007, 08:12 PM   #1
freddi is offline freddi  United States
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Talking Karlson couplers - who is foolhardy enough to try them?

coupled cavity device with indirect radiation. no real gain above a point. chance of holes in response/firewood (& Kerosene)

hit region on some coupler could be good. cone excursion can be low for relatively high outputs vs reflex or even some horn.

had horrible-horrible sound on some - some k-coupler = "pretty good"

vent placement and slot opening (especially in upper half of couler) can affect "tone"

a rear lowpass board giving ~0.2-0.38Sd was sometimes used to improve large signal transient response

3rd Z peak might be of interest and can occur ~135-160Hz for K15 size coupler, ~225Hz for X15 size (~1 cubic foot front chamber)

smaller couplers might be tricker

not much dialogue on Karlson=type and examples appears to pop up more in Europe than US.

any k activity?
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Old 15th January 2007, 08:43 PM   #2
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hey freddy....long time no talk since the K forum went down. anyway, i never finished mine over the summer and then i had to go back to school...besides, my university house probably doesn't have the room for a pair of K15s. I'm stuck with my trusty old Wharfedales for now.

I got a little intimidated by crossover design and sensitivity matching with compression drivers so i decided i would triamp. i am going to be covering the mids with an original spec Smith Horn and might try a K-tube for 5-8khz on up. power'll be provided by a fully regulated LM3875 dual mono gainclone for the woofs, and a pair of modded T-amps for mids and highs. how have your experiements been? and health?
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Old 18th January 2007, 11:52 AM   #3
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I'm thinking about them. Been re-reading Poppe's short paper recently. Wonder what Martin would make of it -I'll have to ask him.

I'd love to play with Karlson enclosures at some point. Maybe drop some 201s into one of the 12in designs out of interest & see what happens. Any thoughts?

I've got some other dark plans afoot, but it depends if I can figure out how best to size / tune the coupler to a specific frequency more accurately than I can at present. I don't like trial and error as I don't have the time, facilities or the money to do physical experiements, so I prefer to use computer modelling based on solid formulas initially.
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Old 18th January 2007, 06:31 PM   #4
freddi is offline freddi  United States
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Hi Scottmoose

I'm not faimilar with 201

a Karlson coupler probably should have hard finish in the front chamber to aid with "reverb". This gives them (on a good day/recording)) a more live and palpable character than direct radiator The effect is adjusted by baffle angle, slot gap at top, coupler width, wings taper.

according to one builder, slot's inductance is one part of the low prequency behavior and that rough model might be in Karlson's 1952 Audio Engineering article.

the original Karlson with good 15" coaxial is not a shabby thing and can play good kick drum and bowed bass which seem to be sticking points for reflex..

I don't have saw, etc to build new test-couplers. A few variants were built and I tested 32x16x21 coupler with 23 degree baffle and 10 degree port board using 15 and 18. RTA is nearly useless besides seeing general LF.

a new test-mule k-coupler should have removable wings and other adjustments available. The upper board may have some forwards cant and an upper reflector might be of benefit .

there will be very little damping in the rear chamber and damping beyond this can kill the sound..

drivers with weak power response like B20 are not suitable.

I don't know how good small coupleres might be made.

besides MJK, Martin Poppe is very alive and well and would converse on Karlson.

K15 was finalized in the summer of 1951 and had 30 degree baffle tilt, dimensions of 33x18x18 (possibly 17 depth for first model), ~40 sq.in. vent and a front deflecting board to partially cancel a 250Hz null. This board never appeared in smaller coupler.

here's a couple of coupler built by Carl N. for look at aspect which might be tried

8" Fostex coupler by CN - later had thicker panels due to flex and Carl probably ran slot all the way up with "V" above the ~1/2" aperture gap

10" test coupler by CN about 10 years ago - later would have "V" extenstion

my 18"K with de-Q-ing V slit

if you have a strong and good 15" coaxial then K15 might be a good start and fun. Then see if it could be "beat" within the same bulk as maxium.

K15 plans

hi bikehorn - dunno - hope i make it
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Old 19th January 2007, 01:40 AM   #5
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I think it's a lack of understanding of exactly what that vent shape does that holds back their popularity. Steve Deckert has use the Karlson slot shape with success on a couple of designs. As you know, I've even used it for a different reason, which seems to work.

With the examples you give that it works well for a 15, but not with smaller drivers, that tells me it's just not understood enough to optimize the design for different size drivers. Maybe what is needed is to get back to basics and start with what it does in simple terms.

For example, I use a K-slot on the side of a short pipe. When I put my ear near the point of the slot, I hear only higher frequency content and more balanced content where the slot is wider. Does a K-slot just act as a different size BR vent with the effective size dependent upon frequency?
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Old 19th January 2007, 01:58 AM   #6
freddi is offline freddi  United States
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Hi John - from what little reports, CN"s 10" coupler bsaed on box above was good and he kinda liked 208 sigma in high aspect k8. C-N feels taller/narrower aspect could be of advantage.

I'm not a good carpenter and lack tools/skills to to nice work

here's a 5" k built by C-N's son based on Karlson's little "Rocket"/asymmetric projector - may sport a k-tube from coaxial's dome

angles on coupler's taper look like 6 & 12
Click the image to open in full size.

maybe someone besides C-N will eventually look at various Karlson and Fulmer & perhaps from a different viewpoint. C-N may offer some info in the future and has worked with K's for a long time.

a K10 should be able to pack a good whallop - I didn't have a grat small coupler going scale with Emiennce 10cx but doesn't mean someone esle might do somewhat better - although rough, mine played strong.

for K10 one might try 14 x 27 13 or so ?


ps a few patents related plus Karlson's stuff



W.O Swinyard US 2020166 filed 1935 “Sound Reproduction Apparatus” - a wedge-shaped 20 degree coupler with “V” deflector having non-parallel walls -

N.C. Fulmer US 2787332 filed 1952 “Loud-Speaker System” - a folded 1/4 wave pipe with last section broadbanded with tapered slot - Fulmer’s patent apparently conflicted with Karlson’s 1st “Acoustic Transducers” and RCA . One story says RCA and Olson went against Karlson and JEK won producing the earliest lab notes.

R-J Enclosure (just for a reference of what was happening in those days)

(1) "The R-J Speaker Enclosure" by William Joseph and Franklin Robbins. Published in Audio Engineering Magazine December 1951.
(2) "Practical Aspects of the R-J Speaker Enclosure" by William Joseph and Franklin Robbins. Published in Audio Engineering Magazine January 1953.

"Acoustic System for Loud-Speaker" US# 2694463; Robbins et al filed April 17, 1952 granted 11/54

J.J. Baruch US2766839 "Loudspeaker System" Filed March 16th 1953, granted Oct. 16th 1956

John A. McKenzie US 3590941 filed 1969 “Speaker Enclosure” - a dual mouth K-coupler like stacked “Asymmetric-Projector” having a final deflector at each mouth

Robert W. Reams US 4196790 filed 1978 “Acoustic Transducer having Multiple Frequency Resonance” - novel use of Karlson’s slot to create a broad-banded throat in a PA-application quasi-scoop horn..

Rodden, M. Raymond US 4313521 filed Feb. 2 1982 "Speaker Housing"

Sapkowski September 3, 1996 "Exponential multi-ported acoustic enclosure" United States Patent 5,552,569

Weiss et al US 5943431 August 24, 1999 “Loudspeaker With Tapered Slot Coupler And Sound Reproduction System”


J.E. Karlson US 2586827 “Directive Radiating System” Filed March 31 1945 - a Parabolic dish microwave antenna with variable directivity pattern

J.E. Karlson “Acoustic Transducers” US 2816619 filed Dec. 1951, granted 6 years later - deals with broadbanding slot both in loudspeakers and musical instuments.

J.E Karlson “Acoustic System” US 2896736 filed Aug. 1955 - use of a modified Karlson laying on its back using either corner or wall to create a diffused sound image

J.E. Karlson “Open End Waveguide Antenna” US 3445852 filed 1968 - essentially analogous with the K-tube waveguide used in Karlson’s X15 2-way speaker ~1966.

J.E. Karlson “Acoustic Transducers” - US 3540544 filed 1968 - concurrent with X15 and described Karlson’s use of ellipse based reflectors to improve the Ultra-Fidlety type.

J.E. Karlson “Jet Engine Silencer Nozzle...) US 3543876 filed 1968 - jet engine muffler and rocket nozzles.


J.E. (Edward) Karlson

1. ELECTRONIC POTENTIOMETER. A variable element which is capable of linear variations of resistances with infinitesimal mechanical motion yet also have capabilities of broad variations in resistance.
2. CAPLESS DISPENSING TUBE. This device permits the use of toothpaste tubes, etc. without the necessity and bother of removing and replacing the cap after each usage.
3. GEOLOGICAL PROSPECTING SYSTEM. A system for use in the prospecting for oil, minerals, etc. This system may also be used for radar applications.
4. RADAR ANTENNA WITH AUTOMATICALLY VARIABLE BEAM PATTERN. This invention provides a simple means of automatically changing the beam pattern of a radar antenna from a pencil beam to a cosecant beam.
5. DIELECTRIC ANTENNA. This invention provides a technique for designing commercial and military antennas which will have overall dimensions than conventional antennae, and yet have equivalent gain and directivity characteristics.
7. ASHTRAY. An extremely simple design for an ash tray which quickly extinguishes cigarettes.
8. PRECISION DELAY CIRCUIT. This circuit provides a delayed pulse at a precise interval following an initial pulse.
10. TELEVISION ANTENNA. This invention provides a simple, low cost antenna which can be readily hidden or obscured in the average room and is suitable for both F.M. and television.
11. SLOT ANTENNA. This design provides a slot antenna with broad band matching possibilities.
12. HYBRID WAVEGUIDE JUNCTION. This is a wave guide section which has variable propagation characteristics dependant upon the direction of propagation.
13. R.F. TUNER. a simplified tuner for F.M. and television use.
14. ADVERTISING SIGN. Novel electric sigh with quick change possibilities.
16. ACOUSTIC TRANSDUCER. A novel loudspeaker enclosure with improved matching characteristics and controlled reverberation.
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Old 19th January 2007, 02:20 AM   #7
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What I need is the simple physics, and I don't need the math, leave that to the math guys. eg Drop and apple it falls. Drop it from higher at it is going faster when it gets to the ground. It doesn't take much trial an error to drop it so it hits someone on the head who is walking by, despite the fairly complex math that we get a feel for intuitively. With Karlsons, I don't think the numbers guys have been able to reduce their behavior to the math, so they don't have much interest. How about starting from a different viewpoint? In simple terms, what do the darn things actually do?
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Old 19th January 2007, 02:54 AM   #8
freddi is offline freddi  United States
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karlson are coupled cavity devices with flared aperture which opens as the wedge shaped chamber's volume is going to zero.

Karlson's first "Acoustic Transducers" patent from the early 1950's give his explanations so that might be a start to understand.

Karlson having speaker back iin chamber add a type of "reverb" which by K's reasoning was desirable to enhance reallism - K15 can sound pretty good.

any driver external to the cabinet will change the mix and some builders like horn on top (or open baffle as in Magnetar's "Rosie" klam with 2-170MO and tweeter)

vented originals (K15/K12 then K8) ran ~2:1 rear chamber over front chamber volume ratio.

with strong motor and light cone, Karlson seem to damp cone excursion on hard transients

I think the LF vs T-S may roughly follow a bandpass simulation. IIRC their 3rd Z peak comes in around 300/225/160Hz as size goes down from K15-K12-K8 - - if one made a rouhd or rectangular hole roughy the size of a K's aperture then would guess the result would be a high tuned bandpass enclosure. Are Karlson more than that?

a tapered slot on a pipe might effectively shorten the pipe (a guess)

C-N has designed camshafts plus re-worked Poppe's paper so has ways of looking at things.

I think orginal style Karlson couplers have size restaints and size-cutoff tradeoffs within those restants.

there ain't much volume to a coupler - only about 0.6 cubic feet on K12, 1 cubic foot on X15 and ~2 cubic foot on K15 and maybe 1.6-2.5 cubic foot for 18".

for simplicity of cabinet there's possiblities of strong output - Im not sure if the air on small K's goes into diestortion at very high spl (?)

not sure if K's can be made to go naturally "deep" although Exemplar uses K15 re-tuned and boosted to augment horn speakers.

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Old 19th January 2007, 03:40 AM   #9
freddi is offline freddi  United States
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"distortion" - might be an inbalance heard in some small coupler where could use a midrange. a regular K12 size with 5% efficient woofer won't go low but can have good punch with 250W input peaks and hit >120dB at 1M. Acoustic Control 115BK with EV15L had similar range - we're looking at back chamber volumes of 1.3 and 1.9 CF - don't get something for nuttin' when building loud small cabinets
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Old 19th January 2007, 03:23 PM   #10
doggy is offline doggy  Canada
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I still have 2 k-15's. Crossed over with a EV tweeter on top worked. They need a fair bit of space.
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