Yep, it's merely a regular K15 Ultra Fidelity. Original size. 
I never tried to sim the FE168 Sigma in the Karlsonator 6, but it looked pretty good for the FE166EN. If you ask nicely, xrk971 might help. He has a much better model than I do.
Here's the link to the karlsonator 6
If you're not familiar with google photos, go to 'more' on the menu to download the image file.
There's also this little modern Karlson type built by AmadeusMozart:
HAK6.5
I never tried to sim the FE168 Sigma in the Karlsonator 6, but it looked pretty good for the FE166EN. If you ask nicely, xrk971 might help. He has a much better model than I do.
Here's the link to the karlsonator 6
If you're not familiar with google photos, go to 'more' on the menu to download the image file.
There's also this little modern Karlson type built by AmadeusMozart:
HAK6.5
Djn,
The K15 is not a sub woofer and probably will never be one as it cannot be scaled up simply to get deeper bass extension - and it really is not good for much below 50 Hz. What it does have is high efficiency and wide bandwidth ( almost full range territory in some cases as I think many run it with a XO as high as 3.5khz. ). The Karlsonator is very scalable on the other hand although to reach 20 Hz the scale would be on the order of a large tapped horn - which it resembles. Simple math would say that the box would be 60 in high (or long) to reach 20 Hz given that the 30 in high box reaches 40hz. If organ music is your thing, what % of the notes or music energy or time is spent at 20 Hz or even below 40hz and how high up do you need this woofer to go? There may be other alignments put there that may suit your needs. I was working on a derivative of the K15 called the T15 that goes to 40hz with 100dB efficiency. Sounds like you need a bass horn or tapped horn - big suckers.
The K15 is not a sub woofer and probably will never be one as it cannot be scaled up simply to get deeper bass extension - and it really is not good for much below 50 Hz. What it does have is high efficiency and wide bandwidth ( almost full range territory in some cases as I think many run it with a XO as high as 3.5khz. ). The Karlsonator is very scalable on the other hand although to reach 20 Hz the scale would be on the order of a large tapped horn - which it resembles. Simple math would say that the box would be 60 in high (or long) to reach 20 Hz given that the 30 in high box reaches 40hz. If organ music is your thing, what % of the notes or music energy or time is spent at 20 Hz or even below 40hz and how high up do you need this woofer to go? There may be other alignments put there that may suit your needs. I was working on a derivative of the K15 called the T15 that goes to 40hz with 100dB efficiency. Sounds like you need a bass horn or tapped horn - big suckers.
My current setup is 4.5 cu ft cabs with Lambda TD15X woofers that go down to f3 45hz, 350hz tractrix horns from 700hz to 5000hz, then the Big A$$ Heils from 5000hz up. I have two front corners that can fit a box 2.5' x 2.5' x 8'. I was thinking of straight tapped horns but now messing with the Ks, it got me thinking.
Here is what I've been looking at.
http://volvotreter.de/th.htm
.
Here is what I've been looking at.
http://volvotreter.de/th.htm
.
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By its bandpass nature, a Karlson will always have a hard time reaching really low. Re-tuning everything for a decent passband in the 20Hz-40Hz area would kill sensitivity and probably not be of any more use than a regular sub. K15's have been used by Exemplar with Altec 416 drivers, re-tuned a bit lower in the 30ies to serve as woofers under large midbass horns. They needed more power than the horns of course, but were said to be one of very few solutions to keep up dynamically, even though extension is not that great.
IG
IG
FE168ESigma in 0.6x scale Karlsonator
Here is the sim of the FE168ESigma in a 0.6x scale Karlsonator. It seems like it can work - very sensitive driver. You have to be careful with max cone excursion though - I would recommend a 65Hz 2nd order high pass filter to control cone excursion - you put 6 volts rms max and this is circa 100dB. This might indicate that the motor for this driver is too strong for this particular cabinet with just simple scaling. The dynamics should be very clean as the impulse response looks quite good.
Freq Response, Impedance, Cone Displacement w 65Hz HPFat 6vrms, Impulse Response
Here is the sim of the FE168ESigma in a 0.6x scale Karlsonator. It seems like it can work - very sensitive driver. You have to be careful with max cone excursion though - I would recommend a 65Hz 2nd order high pass filter to control cone excursion - you put 6 volts rms max and this is circa 100dB. This might indicate that the motor for this driver is too strong for this particular cabinet with just simple scaling. The dynamics should be very clean as the impulse response looks quite good.
Freq Response, Impedance, Cone Displacement w 65Hz HPFat 6vrms, Impulse Response
Attachments
Kool. Gotta love that impulse response.
Just for disclosure - the 'Karlsonator 6' plans I linked to are essentially a .67x scale Karlsonator, though it's fudged very slightly wider for slightly more volume. I forget why, probably because it looked nicer with the FE166.
RE excursion - it's an issue but probably fine for most home users. They could always be highpassed to a TH sub built under the couch.
Gotta love that impulse response. Just for disclosure - the 'Karlsonator 6' plans I linked to are essentially a .67x scale Karlsonator, though it's fudged very slightly wider for slightly more volume. I forget why, probably because it looked nicer with the FE166.
RE excursion - it's an issue but probably fine for most home users. They could always be highpassed to a TH sub built under the couch.
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fwiw here's tuning of the Karlsonator 6 prototype - don't think there was really any polyfill in the the driver section - I'll have to play with the polyfil and give it a listen
Green = 1950's Karlson K8 with Panasonic metal whizzer 8, Purple = Art Welter's dad's interpretation of a K8 based on the K12 and loaded with a BetsyK, Blue = Karlsonator 6 prototype loaded with modified FE164. There's a LOT of vent area in the little Welter coupler but it tunes a bit lower than the factory K8 - I think the front aperture can have quite a bit of influence on system tuning - assuming the vent is near the top.
Greg B's old de-whizzered FE164 in the prototuype - a vintage K15 on the right loaded with P-Audio `15" coaxial
Green = 1950's Karlson K8 with Panasonic metal whizzer 8, Purple = Art Welter's dad's interpretation of a K8 based on the K12 and loaded with a BetsyK, Blue = Karlsonator 6 prototype loaded with modified FE164. There's a LOT of vent area in the little Welter coupler but it tunes a bit lower than the factory K8 - I think the front aperture can have quite a bit of influence on system tuning - assuming the vent is near the top.
An externally hosted image should be here but it was not working when we last tested it.
Greg B's old de-whizzered FE164 in the prototuype - a vintage K15 on the right loaded with P-Audio `15" coaxial
An externally hosted image should be here but it was not working when we last tested it.
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Not sure I follow there.
Do you mean "just make it big" to reach low? I could see this, but we'd be talking pretty darn big at this point. I guess a Karlson with a BP4-like config might be better suited to reach low than what is usually more of a BP6 slope. I think the required size for a front chamber to tune really low would be quite large with a regular K-slot; one might need more restriction as to make it not so much of a Karlson anymore.IG
Designing a speaker that goes very low and still sounds good in the midbass is often a challenge. Pipes and TLs have to be optimized for one or the other, IME.
If something that goes to say 25-30Hz, yet still sounds reasonably punchy is required, the best results I've had in this particular issue have been: either an ML-TL, or a low tuned BR loaded into a corner.
Perhaps a conventional upscaled K15 would perform well. I know some have built K18 cabinets.
If something that goes to say 25-30Hz, yet still sounds reasonably punchy is required, the best results I've had in this particular issue have been: either an ML-TL, or a low tuned BR loaded into a corner.
Perhaps a conventional upscaled K15 would perform well. I know some have built K18 cabinets.
Hmm, who said anything about mid-bass? These are 2-3 octave alignments at best, so the entire BW gets shifted downward. You want a whole decade at a K's narrow band efficiency, then some form of compression horn is required. That, or add several more chambers to the K15 using a very low Fs, Qt driver that can handle a high CR.
GM
GM
No one did, that's why I brought it up....
The original K15 operates more or less as a stand alone full range cabinet. The gain BW essentially fills in the baffle step. If we start talking about supersizing a Karlson type and optimizing for say 20-60hz, it's going to be a subwoofer only. It would be interesting to experiment with your multi chamber idea though.