a front shelf deflects certain mid frequencies and some highs from reaching the upper portion of the coupler. - here's ~ground plane (in middle of a rough hill-lol) for a coupler with and without front shelf. I think if the distance from the junction of the baffle & port board had been less then there wouldn't be a hole. A test coupler with hinged baffle while watching pink noise on RTA could make sense. Karlson deleted the front shelf feature (in new/smaller couplers) by 1954 but its still used by hobbyists to fine-tune their couplers.
K15 is smoother than that coupler above with regards to graph - if that matters
Here's K15 vs a similar bulk reflex with large vents. The tradeoff is the reflex goes lower small signal, large signal the Karlson
has more output from ~60Hz up, less than half the cone excursion and about a 9dB advantage in dynamics - if the motor can deliver
on transients.
The yellow trace is ~ ground plane with the baffle perpendicular to the ground and shows no attenuation
of highs
what I don't understand is why K15 had much less cone excursion at 37Hz on sine than a reflex with the same driver, tuning and volume
of its rear chamber
An externally hosted image should be here but it was not working when we last tested it.
K15 is smoother than that coupler above with regards to graph - if that matters
An externally hosted image should be here but it was not working when we last tested it.
Here's K15 vs a similar bulk reflex with large vents. The tradeoff is the reflex goes lower small signal, large signal the Karlson
has more output from ~60Hz up, less than half the cone excursion and about a 9dB advantage in dynamics - if the motor can deliver
on transients.
The yellow trace is ~ ground plane with the baffle perpendicular to the ground and shows no attenuation
of highs
An externally hosted image should be here but it was not working when we last tested it.
what I don't understand is why K15 had much less cone excursion at 37Hz on sine than a reflex with the same driver, tuning and volume
of its rear chamber
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update - building and data gathering work by John Lapaire
looks like the rear vent formed by a gap in the lowpass shelf and the bottom of the reflector could tune a bit lower and to advantage - FE206E has plenty of high frequency extension - it's tempting to think of a mild notch filter
remember this is only 20" tall, 13.5" wide and 12" deep and will be powerful in its range
Curve 1 - most closed
Curve 2 - most open
looks like the rear vent formed by a gap in the lowpass shelf and the bottom of the reflector could tune a bit lower and to advantage - FE206E has plenty of high frequency extension - it's tempting to think of a mild notch filter
remember this is only 20" tall, 13.5" wide and 12" deep and will be powerful in its range
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Curve 1 - most closed
An externally hosted image should be here but it was not working when we last tested it.
Curve 2 - most open
An externally hosted image should be here but it was not working when we last tested it.
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update - this coupler turned out a success and sounds better than a direct radiating Nirvana Super8 in blh - FE206EN represents high cost-performance value for K-coupler applications. Vocals are great - (its excellent on opera voices - Frick, Schock, Pavarotti), highs are extended and highhat cymbals sweet on good recordings. I've run it with two amps so far - a 375W class D Crown and an 8 watt Tec-on EL34 SE amp, with latter providing the best quality and sufficient power - bass seems about right with the low damping factor. Alan Parson's "Soundcheck" test CD tracks 59 onwards is useful for sorting out loudspeaker performance as it has music tracks which are unprocessed.
direct radiators at times have imo a dull symmetric beaming pattern - in contrast if a Karlson-type's chamber and aperture are favorable, a more "live" type sound is produced with better subjective dispersion.
I hope in the future to see more hobbyists give K-coupler a try for fullrange application. It may take some experimentation to refine but that's the cost of most good speakers.
In line with a good Karlson approach, the new coupler borrowed a vent and lowpass scheme from the first Karlson 12 of fall 1954 and the 1/4 ellipse "Fig6" reflector of Karlson's
"Acoustic Transducers" patent 3540544
"SK8" next to a 1960's factory Karlson Eight coupler
direct radiators at times have imo a dull symmetric beaming pattern - in contrast if a Karlson-type's chamber and aperture are favorable, a more "live" type sound is produced with better subjective dispersion.
I hope in the future to see more hobbyists give K-coupler a try for fullrange application. It may take some experimentation to refine but that's the cost of most good speakers.
In line with a good Karlson approach, the new coupler borrowed a vent and lowpass scheme from the first Karlson 12 of fall 1954 and the 1/4 ellipse "Fig6" reflector of Karlson's
"Acoustic Transducers" patent 3540544
"SK8" next to a 1960's factory Karlson Eight coupler
An externally hosted image should be here but it was not working when we last tested it.
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since the "SK8" coupler was built there's been a new eight inch driver testbox with FE206EN and a 6.5" testbox which will run (stock) FE166EN. Greg B. came up the folding scheme and is reported to work well. The 8 inch coupler (~28" high x 13.5" wide x14' deep) keeps up with JL's K15 2-way system and outperforms it on vocals and things like flute.
here's the first pic of the 6.5" coupler (in the middle) loaded with Fe167. It's reported as promising and the size is very nice.
here's the first pic of the 6.5" coupler (in the middle) loaded with Fe167. It's reported as promising and the size is very nice.
An externally hosted image should be here but it was not working when we last tested it.
I have built a K8 for the FE167e and maintain interest in the build technique. It looks elegant to me but on setup of the K8 and with the three narrow vents plus recommended wing design what I heard rather than read about was a sound that emphasized all the cavities within. IOW not a clear sound at all. For now I reinstalled the 167e in a BR with factory recommended port (but different dimension box than that of the spec sheet.)
I do have a baffle board cut for a 8" open baffle and prepared to cut down for my future attempt at a K12.
Yes there is interest in the Karlson design but my attempt was left wanting.
Next operation (I think) will be with a Mark Audio for a BIB. Supplies of those are pretty scarce.
I do have a baffle board cut for a 8" open baffle and prepared to cut down for my future attempt at a K12.
Yes there is interest in the Karlson design but my attempt was left wanting.
Next operation (I think) will be with a Mark Audio for a BIB. Supplies of those are pretty scarce.
got some pictures for a kritique? - the original K8 size is "touchy" and the factory models will sound only good with certain drivers. (Panasonic's "Metal" sounds pretty good but is lacking on top octave energy)
I've not mounted FE206EN into factory K8s due to the way Fostex builds the front raised rim. The recent "SK8" project with FE206EN was very good with all three apertures tried with any(*) music and all of Alan Parson's test tracks. GB's SK6.5 should be good too and will have to wait for reports and testing when FE166EN arrive. JL liked it with FE167 but doesn't like a certain spot in 167 no matter how its mounted. I like SK8 but will probably go with a pair of high-aspect 8 cabinets for FE206EN based upon GB's SK6.5
I would avoid recommendation of the original 8s because it can be done in a more neutral fashion - but that said - it may be an empirical process to make a really nice small coupler. SK8 sounded better than my K-horns and faux La Scala and K12 can sound good with certain drivers.
(*I like opera, percussion music, classic blues, funky hammond organ, harpsichord, etc.)
I've not mounted FE206EN into factory K8s due to the way Fostex builds the front raised rim. The recent "SK8" project with FE206EN was very good with all three apertures tried with any(*) music and all of Alan Parson's test tracks. GB's SK6.5 should be good too and will have to wait for reports and testing when FE166EN arrive. JL liked it with FE167 but doesn't like a certain spot in 167 no matter how its mounted. I like SK8 but will probably go with a pair of high-aspect 8 cabinets for FE206EN based upon GB's SK6.5
I would avoid recommendation of the original 8s because it can be done in a more neutral fashion - but that said - it may be an empirical process to make a really nice small coupler. SK8 sounded better than my K-horns and faux La Scala and K12 can sound good with certain drivers.
(*I like opera, percussion music, classic blues, funky hammond organ, harpsichord, etc.)
AFAIK, all JEK produced kouplers had radial (or very close) wings. Some have experimented with tractrix and other profiles as well. One thing that is important IMHO is to keep some driver overlap; the aperture width at driver intercept (on-axis) determines the dispersion characteristics to some extent.
IG
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