I have not built much in the way of audio for a few years, now, but got an itch to lately. I already own enough speakers and amps for my needs, so cannot justify an all-out build. As a flip-side to my more standard speaker design/building efforts, I have stashed away some less orthodox designs such as Karlsons, RJ and Nagaoka-inspired enclosures.
I have this simplified and shortened version of the Karlson SK8 I called the mini-SK8 or mSK8. I designed it hoping it might do well with pro drivers such as the B&C 8PE21 or 8CX21, with some power above 100Hz. I do not have these drivers or other suitable. What I do have is a pair of Faital pro 6FE100, although I measured their T/S parameters to differ from factory specs, namely lower Cms, higher Fs and Qts. I decided to go with these despite not being usual suspects for Karlson.
There exits a high-aspect 6" Karlson dubbed the HAK6.5, but wanted something simpler and a bit smaller, so I designed the below, calling it Tall K6, or TK6 for short.
I wanted to keep the SK8's 20" internal height, but reduce the rear to front chamber volume ratio. I used my adapted BP6 model to design to my 6FE100's parameters. It's also a good occasion to test said model, simple as it is.
BB-ply price having gone way up, I opted to build the outer shell from MDF and used leftover BB-ply for the wings and internal panels. I've also built only one unit, as this is somewhat experimental and I like a single Karlson playing mono as well.
The wings and back panel are unbraced as of yet, but I'll get around to doing so. I have taken a few measurements, which I will post shortly.
I have this simplified and shortened version of the Karlson SK8 I called the mini-SK8 or mSK8. I designed it hoping it might do well with pro drivers such as the B&C 8PE21 or 8CX21, with some power above 100Hz. I do not have these drivers or other suitable. What I do have is a pair of Faital pro 6FE100, although I measured their T/S parameters to differ from factory specs, namely lower Cms, higher Fs and Qts. I decided to go with these despite not being usual suspects for Karlson.
There exits a high-aspect 6" Karlson dubbed the HAK6.5, but wanted something simpler and a bit smaller, so I designed the below, calling it Tall K6, or TK6 for short.
I wanted to keep the SK8's 20" internal height, but reduce the rear to front chamber volume ratio. I used my adapted BP6 model to design to my 6FE100's parameters. It's also a good occasion to test said model, simple as it is.
BB-ply price having gone way up, I opted to build the outer shell from MDF and used leftover BB-ply for the wings and internal panels. I've also built only one unit, as this is somewhat experimental and I like a single Karlson playing mono as well.
The wings and back panel are unbraced as of yet, but I'll get around to doing so. I have taken a few measurements, which I will post shortly.
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As I'll need a tweeter to play above the TK6, I decided to build some K-Tubes. I used to own some Transylvania Power Company "The Tube" and really enjoyed them. I also made some from PVC, alu and brass in the past.
I made one from a schedule 80 PVC threaded fitting and made a crude mount from a threaded adapter, which I somewhat press-fitted on a BMS 4540ND.
The slotted portion is 4.5" long and the threaded portion makes for an unslotted length, which I believe is perhaps not ideal, but that's how this one is for now.
I also made a semi-failed tube from laminated paper and fiberglass tape, and PVA glue. Its diameter turned out a tad larger than 1", but actually fits an Eminence APT50 well, since it is also a bit over 1".
I have worked out a better and more accurate way to implement this construction method.
I made one from a schedule 80 PVC threaded fitting and made a crude mount from a threaded adapter, which I somewhat press-fitted on a BMS 4540ND.
The slotted portion is 4.5" long and the threaded portion makes for an unslotted length, which I believe is perhaps not ideal, but that's how this one is for now.
I also made a semi-failed tube from laminated paper and fiberglass tape, and PVA glue. Its diameter turned out a tad larger than 1", but actually fits an Eminence APT50 well, since it is also a bit over 1".
I have worked out a better and more accurate way to implement this construction method.
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Your K6 has a very nice look as does the elegant tilt-able K-tube holder.
Sealed was recommended in some driver cases back when Karlson was alive and that driver a very healthy xmax.
Will the tweeter roll-in around 2k8 or so ?
Diy you employ hornresp for your modified BP model? Did you adjust the front volume downwards as all may not be active due to the wedge shape tapering in volume downwards towards zero when the aperture width is approaching its maximum.
I think with some idea of how to fudge its chamber dimensions' inputs that it may approximate some Karlson types. MMJ did a fudge for Acoustic Control's 115BK Karlson cabinet which looks very close to what I've measured with a real 115B
A long time ago I posted Carl's specs of volumes and areas for K15 -maybe they still reside at Audioasylum (?)
Sealed was recommended in some driver cases back when Karlson was alive and that driver a very healthy xmax.
Will the tweeter roll-in around 2k8 or so ?
Diy you employ hornresp for your modified BP model? Did you adjust the front volume downwards as all may not be active due to the wedge shape tapering in volume downwards towards zero when the aperture width is approaching its maximum.
I think with some idea of how to fudge its chamber dimensions' inputs that it may approximate some Karlson types. MMJ did a fudge for Acoustic Control's 115BK Karlson cabinet which looks very close to what I've measured with a real 115B
A long time ago I posted Carl's specs of volumes and areas for K15 -maybe they still reside at Audioasylum (?)
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I have yet to measure the 4540ND on that K-Tube, so I'm not sure how low I can take that one, but I think I could play it down to 2kHz since it won't be seeing much power in my house. I might also give this one a shot above my 5cu.ft TD15M box for fun, a bit like ReinoutdV runs his over the Supravox 12". The power response will be terrible compared to the QSC waveguide though, but technical perfection is not a goal this time around. 
I used WinISD, even though it cannot do series BP6. I worked backwards from my Karlsonette and SK8 measurements to tweak the various parameters in line with reality. This TK6 is a bit stretched vertically, but perhaps no so much as to entirely invalidate my method.
IIRC, the SK8 had a smaller front/rear chamber ratio compared to K12 or K15 and behaved somewhat better in its upper bandwidth, so I went for a smaller volume when thinking of the mSK8 and carried the idea over to the TK6. I may also have been inspired by any of the X15/115BK sized couplers that measured well. I think I was cooking up something in that size range some years back before losing interest.
I used WinISD, even though it cannot do series BP6. I worked backwards from my Karlsonette and SK8 measurements to tweak the various parameters in line with reality. This TK6 is a bit stretched vertically, but perhaps no so much as to entirely invalidate my method.
IIRC, the SK8 had a smaller front/rear chamber ratio compared to K12 or K15 and behaved somewhat better in its upper bandwidth, so I went for a smaller volume when thinking of the mSK8 and carried the idea over to the TK6. I may also have been inspired by any of the X15/115BK sized couplers that measured well. I think I was cooking up something in that size range some years back before losing interest.
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with Transylvania's "The Tube" I've run the old Dayton polyamide 1"CD -BM450,etc.with Eminence's generic "1K6" 8uF-0.8mH-24uF highpass and no audible strain with percussion. Oddly, I have heard strain with that
highpass using coaxial speakers. The Tube and De250 kept up with my double JBL 2035 box.
My 41" high K18 with curved reflector was really good.
Here's something to try with your APT50
highpass using coaxial speakers. The Tube and De250 kept up with my double JBL 2035 box.
My 41" high K18 with curved reflector was really good.
Here's something to try with your APT50
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I think it slipped over the APT3 adapter's plastic threads making tube length a bit more than 3.5" . (later versions of APT had their 1 3/8"threaded section integral with the body rather than the odd APT3 adapter.
- guess the final width of the slot is 1.5" They used it I think with Eminence's 3K5 network (~4uF/0.4mH/12uF IIRC) on Beta 8cx that rolled in around 2k8 with APT50 - I really like some phenolic drivers including the old APT50
Have you put some music through it yet?
- guess the final width of the slot is 1.5" They used it I think with Eminence's 3K5 network (~4uF/0.4mH/12uF IIRC) on Beta 8cx that rolled in around 2k8 with APT50 - I really like some phenolic drivers including the old APT50
Have you put some music through it yet?
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those Foster horns seemd still iin production many years past the Allegro.
A late friend who was a very good guitarist had an Allegro system in the
early 1970's and it sounded pretty good in ways.
I've been staying with my kid for a long time and he threw a fit when I said I wanted to get a 20 inch tall / 15 inch driver
cabinet built to sit under the K8MR (which sits in a wire shelf unit-presently there's Art Welter's Dad's "K8" on the bottom shelf -
I've not played with my toys for 2 years)
A late friend who was a very good guitarist had an Allegro system in the
early 1970's and it sounded pretty good in ways.
I've been staying with my kid for a long time and he threw a fit when I said I wanted to get a 20 inch tall / 15 inch driver
cabinet built to sit under the K8MR (which sits in a wire shelf unit-presently there's Art Welter's Dad's "K8" on the bottom shelf -
I've not played with my toys for 2 years)
To my ears and withmeasurements, GregB's "Karlsonator 6"was a success.
The prototype worked well with both my high-ish Qts LCao F6 and de-whizzered Fostex FE164. I'm saddened that there have not been many builds.
You mentioned slumming it a bit with Beta 8cx for another project. They can.sound pretty darn good Eminence's 2k5cx network values might choke it a bit. I did not like that crossover withBeta10cx in the Karlsonator 12.
Mike Chua is picky so bet his Osprey networks for Beta10cx are better if you use their10cx.
The prototype worked well with both my high-ish Qts LCao F6 and de-whizzered Fostex FE164. I'm saddened that there have not been many builds.
You mentioned slumming it a bit with Beta 8cx for another project. They can.sound pretty darn good Eminence's 2k5cx network values might choke it a bit. I did not like that crossover withBeta10cx in the Karlsonator 12.
Mike Chua is picky so bet his Osprey networks for Beta10cx are better if you use their10cx.
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The Karlsonator does look like a good design, though I have not tried it. I could modify my TK6 to make it closer to a Karlsonator, a bit like when I added a vertical partition to the SK8 - which did not work out well back then though. At the very least, I plan to try venting it at the top of the reflector, as it now vents at the shelf.
yeah - in some cases of higher tuning, that could be accomplished just with a "sub-baffle" spaced on cleats - even the baffle in front could use a slot.
GregB's original "Karlsonator" for 12"tunes about 37Hz-which is good for higher q speakers such as 12LTA. Karlsonator 8 tunes 41Hz-perhaps a bit low for some 8" Karlsonator 6 tunes 60Hz - snappy with6 Fostex yet controlled with my 0.7 qts L Cao F6. (The Fostex sounds better with slapped upright bass)
I think the Karlsonator with driver offset plus ability to damp the stub makes it less prone to a cancellation.
Art Welter's Dad's "K8" is tuned around 95 Hx with large distributed slot vents. Note how low Karlsonator6 goes with F6--and F6 is a bit louder than Eminence's Delta Pro 8A (again-higher q drivers just seem to lack "snap")
GregB's original "Karlsonator" for 12"tunes about 37Hz-which is good for higher q speakers such as 12LTA. Karlsonator 8 tunes 41Hz-perhaps a bit low for some 8" Karlsonator 6 tunes 60Hz - snappy with6 Fostex yet controlled with my 0.7 qts L Cao F6. (The Fostex sounds better with slapped upright bass)
I think the Karlsonator with driver offset plus ability to damp the stub makes it less prone to a cancellation.
Art Welter's Dad's "K8" is tuned around 95 Hx with large distributed slot vents. Note how low Karlsonator6 goes with F6--and F6 is a bit louder than Eminence's Delta Pro 8A (again-higher q drivers just seem to lack "snap")
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The old-school RJ (not Supravox-style) is already a bandpass like a Karlson, save for a much smaller front chamber, so I suppose it might turn out to be a BP8. I don't know if this would be worthwhile.
What could be interesting IMO is a PPSL in a Karlson for midbass duty.
hey IG81 -
how far off is TK6's maiden voyage into music-land?
are you going to use a 2nd order highpass to the K-tube? - how about the Faital 6?
Here's a little drumkit -underdamped kick tuned "70Hz"-simple micing
Steve Maxwell Vintage Drums - Gretsch G4160B 5x14" USA Custom Snare Drum - Bronze - YouTube
how far off is TK6's maiden voyage into music-land?
are you going to use a 2nd order highpass to the K-tube? - how about the Faital 6?
Here's a little drumkit -underdamped kick tuned "70Hz"-simple micing
Steve Maxwell Vintage Drums - Gretsch G4160B 5x14" USA Custom Snare Drum - Bronze - YouTube
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Here are a few measurements. All were taken with the cabinet elevated 40cm from the floor, on the driver's axis, 50cm away and 1/12 smoothing applied. The SPL is not calibrated as the drive level was not verified, only set to REW's liking above the noise floor.
First up, sealed rear chamber.
Second, vented rear chamber, by way of removing the small horizontal shelf board, so a 9" by 0.5" slot.
Third, vented once more, but with short lateral shelf boards, leaving a central 3.9" slot. Fb is a bit more in line to what I aimed for here.
I've flattened the inductance with a Zobel so as to more easily work out a simple crossover and actually listed to it with a tweeter.
It lines up well enough with my adapted BP6 simulation. The mid-300Hz peaking may be related to the internal 20" dimension. It is somewhat worse on the sealed box; opening the vent might de-Q the half-wave mode. I lost most of my old K12 and SK8 measurements, so can't compare.
First up, sealed rear chamber.
Second, vented rear chamber, by way of removing the small horizontal shelf board, so a 9" by 0.5" slot.
Third, vented once more, but with short lateral shelf boards, leaving a central 3.9" slot. Fb is a bit more in line to what I aimed for here.
I've flattened the inductance with a Zobel so as to more easily work out a simple crossover and actually listed to it with a tweeter.
It lines up well enough with my adapted BP6 simulation. The mid-300Hz peaking may be related to the internal 20" dimension. It is somewhat worse on the sealed box; opening the vent might de-Q the half-wave mode. I lost most of my old K12 and SK8 measurements, so can't compare.
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Taken on the 9" wide slot vented, here is a near-cone as well as ground plane - perhaps questionable as taken indoors.
The mid-300Hz peaking still shows-up, lesser in magnitude.
My BP6 model assumes a quarter-wave mode for 90-905% of the front chamber's height, which might line up with the near-cone trace's mini 180Hz dip. The impedance minima in that region is actually 171Hz, but tunings and near-cone dips don't always line up. I'm just not certain why the distanced FR traces show a large suck-out at 180Hz, perhaps floor bounce or another room effect? It is somewhat diminished on the ground plane trace, which might suggest so.
The mid-300Hz peaking still shows-up, lesser in magnitude.
My BP6 model assumes a quarter-wave mode for 90-905% of the front chamber's height, which might line up with the near-cone trace's mini 180Hz dip. The impedance minima in that region is actually 171Hz, but tunings and near-cone dips don't always line up. I'm just not certain why the distanced FR traces show a large suck-out at 180Hz, perhaps floor bounce or another room effect? It is somewhat diminished on the ground plane trace, which might suggest so.
Gee -port position seems to matter.
A couple of those are promising-and pretty good.
If you put some stuffing in the very top of the front chamber, might that improve response around 300Hz? I'd guess a pipe stub could be put in the rear chamber instead.
-don't know if these old plots from my 0.62 scale K15 (also around 20" high) tell anything comparable or not.
A previous K10 of similar height had a peak around 210Hz
A couple of those are promising-and pretty good.
If you put some stuffing in the very top of the front chamber, might that improve response around 300Hz? I'd guess a pipe stub could be put in the rear chamber instead.
-don't know if these old plots from my 0.62 scale K15 (also around 20" high) tell anything comparable or not.
A previous K10 of similar height had a peak around 210Hz
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We clearly see the typical W-effect on your trace at ~250Hz. I think my TK6's W is from 350Hz-1kHz, I'd just like to figure out the 180Hz dip.
I may have a few old SK8 traces still up on various forum, I should look them up to compare.
Here is the BMS 4540ND with 4.5" PVC K-tube.
Naked versus tube-on:
FR at 50cm, straight on the tube's axis versus tube firing slightly above the mic, perhaps 20 degrees or so, I'll take more precise measurements of that later.
It's quite well-behaved above 3-4kHz. I should probably not try to take it much below 2.5kHz or so in any case. The 800Hz peaking might show up if I use a shallow slope.
I may have a few old SK8 traces still up on various forum, I should look them up to compare.
Here is the BMS 4540ND with 4.5" PVC K-tube.
Naked versus tube-on:
FR at 50cm, straight on the tube's axis versus tube firing slightly above the mic, perhaps 20 degrees or so, I'll take more precise measurements of that later.
It's quite well-behaved above 3-4kHz. I should probably not try to take it much below 2.5kHz or so in any case. The 800Hz peaking might show up if I use a shallow slope.
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