Designing an ULF Karson....
I am interested what an ultra-low frequency (ULF) Karlson might look like. I am planning on building a home theater and I could use some sort of bass system (50 - 200hz which could be OB or K15 Karsons), and Lowthers on OB above that, but I am wondering if I could use something like a Karson for frequencies below 50 hz (i.e., 10 - 50 hz). The other options for ULFs would be an infinite baffle or, I suppose, a tapped horn (the fan subwoofer would be another option, but they are expensive). I am interested in a Karson design because of the ability of the design to minimize cone movement (and thus, reduce distortion) at hte lowest frequencies.
The drivers I have on hand which I would like to use in such a ULF Karson are Avalanche 18s (Xbl2 design) (Qts=0.4, Fs=16, Qes=0.43, Qms=6, Xmax=27mm, VAS=550 liters, Mms=369g, BL=17). These drivers are truly meant for ULFs. I have two drivers so I could either make two separate boxes or put both drivers in one box.
Because I am building the room from scratch, I could build the ULF Karson speakers into the walls.
What are we talking about, a "box" which is about 10 feet high and 3 feet wide? What depth would I need? Would I simply expand the K15 or would the design need to be more sophisticated than that?
Retsel
I am interested what an ultra-low frequency (ULF) Karlson might look like. I am planning on building a home theater and I could use some sort of bass system (50 - 200hz which could be OB or K15 Karsons), and Lowthers on OB above that, but I am wondering if I could use something like a Karson for frequencies below 50 hz (i.e., 10 - 50 hz). The other options for ULFs would be an infinite baffle or, I suppose, a tapped horn (the fan subwoofer would be another option, but they are expensive). I am interested in a Karson design because of the ability of the design to minimize cone movement (and thus, reduce distortion) at hte lowest frequencies.
The drivers I have on hand which I would like to use in such a ULF Karson are Avalanche 18s (Xbl2 design) (Qts=0.4, Fs=16, Qes=0.43, Qms=6, Xmax=27mm, VAS=550 liters, Mms=369g, BL=17). These drivers are truly meant for ULFs. I have two drivers so I could either make two separate boxes or put both drivers in one box.
Because I am building the room from scratch, I could build the ULF Karson speakers into the walls.
What are we talking about, a "box" which is about 10 feet high and 3 feet wide? What depth would I need? Would I simply expand the K15 or would the design need to be more sophisticated than that?
Retsel
Well, its acoustic 'path-length' would be shorter due to venting, but not sure that for a given net bulk that its gain BW/peak power handling will best a simple to design/build T-TQWT. Only one way to know for sure though.
GM
You might want to check out the discussion on the Metro T15 sub in this thread. About 45 Hz extension with broad bandwidth to 150 Hz
A K15 is a ~two octave BP, so at ~2.32 octaves, it would need some EQ or another gain stage. A TH can be stretched to ~three octaves and a FLH can be EQ'd to up to ~five octaves.
Size would be a function of pipe horn tuning [Fp] and driver specs.
GM
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fwiw you could do as Exemplar - use an Altec 515 (whichever model was low fs) or a 416 - tune K15 with two 3"Id right angle pvc elbows - apply some narrow boost at 30Hz - bass is usable to 20-22Hz -to go lower without any significant rear path length would require lower tuning and perhaps something like a transform. I know this approach doesn't seem to make sense but it "sounds good" and John Tucker found it to be a way to augment BR/horn mains
I think the K15 below was Exemplar's first
K15 by itself is a good fullrange coax cabinet
An externally hosted image should be here but it was not working when we last tested it.
I think the K15 below was Exemplar's first
An externally hosted image should be here but it was not working when we last tested it.
K15 by itself is a good fullrange coax cabinet
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As a very rough rule of thumb, when scaling original type Karlsons, the BW gain region typically extends about an octave on each side of the front chamber tuning frequency. You'll probably want to aim for a tuning of about 30Hz. So, assuming the 1/4w mode is dominant (I realize this is a big assumption), it will be about 9.5 feet. Your guess was pretty good. 😉 It would be smaller than a 30hz horn anyway.
There actually was a historical installed Karlson sub-bass contraption of similar size. It's not clear to me if it was ever made.
When I had a pair of K15 boxes running, I had planned to do a near field ML-TL under or behind the sofa for sub bass, but I never got around to it. This is probably a more practical way to go, at least AFA size. There's also TH, or perhaps a scaled up Karlsonator.
Yes, as I showed in a sim, a scaled up Karlsonator can make a nice sub. This one is 34 in long x 7 in wide and uses a couple of 5.25 inch drivers. Reaches 35 hz flat - really close to a tapped horn. This actually does not use the K aperture - just a rectangular opening.
here's the 12 foot klam drawings - -these are from notes from John Karlson left to Marty Poppe
http://img503.imageshack.us/img503/183/apt12ci5.jpg
http://img99.imageshack.us/img99/8914/ts26hx.jpg
http://img503.imageshack.us/img503/183/apt12ci5.jpg
http://img99.imageshack.us/img99/8914/ts26hx.jpg
Thanks for the responses guys for ULF Karlson
So an extra long/large Karlson is a possible strategy, and would have to be much larger than a conventional K15. Based on what I have read, the drivers I have would be better for a Karlson than a tapped horn (0.4 Qts instead of <3, and a BL of under 20 instead of greater than 20). I realize that I may be in trial and error territory if I wish to experiment with this route.
When I read through the literature, it seemed that the low frequency cutoff is a function of both the "pipe" length (front chamber), and size of the opening to the room. Thus, the aperature would have to be wider and longer to allow for lower frequencies. The crude sketches which Freddy has seems to bear that out. From what I can see, the sketches don't seem to have all the dimensions on them. Freddy, do you have any other drawings for the extra large Karlson? If the drawings are to scale, I could estimate the width from the length which is dimensioned.
I recall that one of the patent documents stated that smaller drivers (which this could be in this case) can be mounted further up the front chamber if the driver size is small relative to the aperature. That is perhaps why the drivers seemed to be mounted higher up.
Retsel
So an extra long/large Karlson is a possible strategy, and would have to be much larger than a conventional K15. Based on what I have read, the drivers I have would be better for a Karlson than a tapped horn (0.4 Qts instead of <3, and a BL of under 20 instead of greater than 20). I realize that I may be in trial and error territory if I wish to experiment with this route.
When I read through the literature, it seemed that the low frequency cutoff is a function of both the "pipe" length (front chamber), and size of the opening to the room. Thus, the aperature would have to be wider and longer to allow for lower frequencies. The crude sketches which Freddy has seems to bear that out. From what I can see, the sketches don't seem to have all the dimensions on them. Freddy, do you have any other drawings for the extra large Karlson? If the drawings are to scale, I could estimate the width from the length which is dimensioned.
I recall that one of the patent documents stated that smaller drivers (which this could be in this case) can be mounted further up the front chamber if the driver size is small relative to the aperature. That is perhaps why the drivers seemed to be mounted higher up.
Retsel
Why don't you just make a rolled up bass horn? The size would be a little larger than a tapped horn. Here is an excellent guide.
Folded bass horn - The Paper Horn by Inlow Sound
Folded bass horn - The Paper Horn by Inlow Sound
Yeah, those are the Giant Klams!
I have to say I disagree. There's a lot of stuff in the original patents that doesn't hold up to modern scrutiny. If scaling, I'd stretch the height, but determine the width and depth to based air volume requirements for the driver.
Before making huge investments in time and materials, consider making some computer simulations.
If it were me, I would run those Avalanche drivers in 1.5+ scaled Karlsonators. They'd be about 16 cu feet each. Of course, I am very biased towards this design. 😉
Room modes are really as important as anything else once you get down into sub territory. That being so, two subs will help spread the null/peaks around a bit more than one big one.
As an aside, I guess from here on out, anything drafted by hand is "crudely drawn". 😱
I have to say I disagree. There's a lot of stuff in the original patents that doesn't hold up to modern scrutiny. If scaling, I'd stretch the height, but determine the width and depth to based air volume requirements for the driver.
Before making huge investments in time and materials, consider making some computer simulations.
If it were me, I would run those Avalanche drivers in 1.5+ scaled Karlsonators. They'd be about 16 cu feet each. Of course, I am very biased towards this design. 😉
Room modes are really as important as anything else once you get down into sub territory. That being so, two subs will help spread the null/peaks around a bit more than one big one.
As an aside, I guess from here on out, anything drafted by hand is "crudely drawn". 😱
BTW, I'm pretty sure those giant klams are open to the back, so it's an IB variation. Some people do similar stuff today, but with the drivers feeding a BP box in the attic or basement.
yeah - many years ago in Speaker Builder (IIRC), there was an article on a simple bandpass speaker - - the rear chamber was the house crawlspace, the front chamber was a plastic 55 gallon barrel. The vent went between the barrel and a floor duct.
ULF Karlson et al
Thanks again for the great responses. The giant klams are indeed interesting. Imagine, I could have the only giant klams on the planet, perhaps in the whole universe!!! Ok, I guess I should not get ahead of myself....
That is a great point Greg about having multiple subs instead of one big one. Multiple 1.5+ Karlsons may be better, and I could boost the low end if I would want deeper response. If I figure out where to place them, I could mount those in the wall as well (saves floor space). For sizing them, do I simply increase all the dimensions (width, height, depth) by 1.5? I could also add the elbows like Johnny Tucker did (thanks Freddy for the idea), which could help to get deeper bass.
As an alternative, I could do a scaled down infinite baffle Klam (like the sketch, but smaller - an infinite baffle is an option with the audio room I am planning). However, if the drivers are loaded on one side, I would think that this would increase the distortion.
Hey xrk971, I am still less interested in a bass horn because the Avalanche drivers don't seem to be suited for horn duty - I would have to abandon them, right?
I do recall that someone put the Avalanche drivers in a sonotube and got a great subwoofer.
Retsel
Thanks again for the great responses. The giant klams are indeed interesting. Imagine, I could have the only giant klams on the planet, perhaps in the whole universe!!! Ok, I guess I should not get ahead of myself....
That is a great point Greg about having multiple subs instead of one big one. Multiple 1.5+ Karlsons may be better, and I could boost the low end if I would want deeper response. If I figure out where to place them, I could mount those in the wall as well (saves floor space). For sizing them, do I simply increase all the dimensions (width, height, depth) by 1.5? I could also add the elbows like Johnny Tucker did (thanks Freddy for the idea), which could help to get deeper bass.
As an alternative, I could do a scaled down infinite baffle Klam (like the sketch, but smaller - an infinite baffle is an option with the audio room I am planning). However, if the drivers are loaded on one side, I would think that this would increase the distortion.
Hey xrk971, I am still less interested in a bass horn because the Avalanche drivers don't seem to be suited for horn duty - I would have to abandon them, right?
I do recall that someone put the Avalanche drivers in a sonotube and got a great subwoofer.
Retsel
Those Avalanche drivers have a Qts of 0.4 and a high Bl - seems well suited for bass or tapped horn actually. Only was to tell is to run a sim. Use the Hornresp input page from the link I gave earlier and substitute with your driver.
Hmm, can't see the big klam's drawings very well....... is it literally just a super sized, dual driver, 4th order BP?
GM
GM
If ~accurate, the Avalanche’s specs means it will make for a 'jack o' trades, master of none' true sub, so most any type alignment including horns can be used, it just needs to be big, so IB would be ~ideal for movies, pipe organ symphonies with output to near DC and use multiple smaller subs distributed around the room for ‘fill’. These probably need to be different type alignments depending on their locations or just go low Q sealed and use EQ to get the best blend to the IB.
If IB isn’t practical, then a ~10 Hz TH/~1000 L ‘buried’ in a wall, second tier seating, raised front ‘stage’/whatever is viable for a ~60 Hz XO ideally, but could be ‘stretched’ to 80 Hz if narrow enough band-width EQ is available, thought its ‘klam’ aperture wouldn’t be all that large/imposing.
Larger will of course gains you more efficiency and/or a lower tuning, but at this point an IB is probably best overall SQ wise unless a true front [or even back loaded] compression bass horn combined with sufficient electronic delay is viable.
So, do you perchance live in a large stone castle, bomb shelter or similar capable of containing several acoustic watts of infra sonic dinosaur stampede, rolling thunder, space shuttle lift-off, multiple depth charge or similar detonations? 😉
GM
edit: This really needs to be split off to the 'subwoofer' forum.
If IB isn’t practical, then a ~10 Hz TH/~1000 L ‘buried’ in a wall, second tier seating, raised front ‘stage’/whatever is viable for a ~60 Hz XO ideally, but could be ‘stretched’ to 80 Hz if narrow enough band-width EQ is available, thought its ‘klam’ aperture wouldn’t be all that large/imposing.
Larger will of course gains you more efficiency and/or a lower tuning, but at this point an IB is probably best overall SQ wise unless a true front [or even back loaded] compression bass horn combined with sufficient electronic delay is viable.
So, do you perchance live in a large stone castle, bomb shelter or similar capable of containing several acoustic watts of infra sonic dinosaur stampede, rolling thunder, space shuttle lift-off, multiple depth charge or similar detonations? 😉
GM
edit: This really needs to be split off to the 'subwoofer' forum.
I was actually suggesting ~1.5 scaled Karlsonators, which is not technically a Karlson, but a modern design with a different rear loading. Yes, I was suggesting to take the Karlsonator, and scale all dimensions by 1.5 or slightly more.
Considering the expense in time and materials, it will worth your time to do a simulation. For your purposes, the Karlson exit shape could be ignored, and the boxes modeled as tapped horns in hornresp or whatever.
If you wanted to scale the 'traditional' Karlson K15 to work in sub bass, I'll stick to my recommendation to stretch vertically by 3x or more. Alternatively, you could tune one low and EQ the hell out of it like Exemplar. It won't go as low as your desired BW though, unless you scale the whole thing up drastically. IIRC Exemplar used them to supplement approximately 100hz midbass horns - totally different requirements.
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To be honest, if it were me, I'd just put them in a floor or ceiling mounted IB and be done with it. Maybe a long TL if I felt really ambitious.
But the question was how to make a Karlson cover the 10-50Hz BW...
But the question was how to make a Karlson cover the 10-50Hz BW...
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