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A Speaker that Kicks Butt in Large Spaces
A Speaker that Kicks Butt in Large Spaces
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Old 9th February 2019, 02:27 AM   #1241
perceval is offline perceval  Taiwan
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Woah!

There's a guy here who's building cabinets for K-12 and K-15.

He's asking $8,400 (that's USD) for a pair.
Ouch!

And that's not including the driver.
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Old 9th February 2019, 09:28 AM   #1242
xrk971 is offline xrk971  United States
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There is a market for old style K15’s in Taiwan?

That pricing is aimed at audiophiles with bank. The cabinets do look beautiful though - are they veneered or is that solid cherry or walnut? In which case, the price may not be unreasonable as it is like furniture.
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Old 13th February 2019, 05:45 PM   #1243
freddi is offline freddi  United States
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A Speaker that Kicks Butt in Large Spaces
Default "Stubby - K" perhaps someone will experiment with a smoothing stub

an extra chamber ("side-branch" I guess would be the term) at the top of the box couples to the K's front chamber. MMJ modeled this in akabak, but also came up with a double-fudge model for Hornresp. I think the extra chamber tends to add some front chamber volume plus can be stuffed with polyfil to absorb some reflections and further smooth response.

maybe someone will do some experimentation.

also, I pretty sure K's can be done well as originals with no damping in their front chamber. Maybe a vent at the top of the front chamber is helpful. (Acoustic Control's 115BK was pretty smooth with no damping anywhere including the back chamber) My tall K18 with traditional vent placement and a large curved reflector is smooth.

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Old 15th February 2019, 12:50 PM   #1244
KaffiMann is offline KaffiMann  Norway
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How do you calculate the K-coupler itself?
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Old 15th February 2019, 04:14 PM   #1245
freddi is offline freddi  United States
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A Speaker that Kicks Butt in Large Spaces
for the original Karlson, its probably easiest to look at it from the standpoint (at least in a certain frequency range) as a higher than normally tuned series bandpass cabinet and in that limited LF range, its response probably not terribly different with a rectangular opening than with the tapered aperture. If you look at K15 and K12, their front chamber is about half volume of the rear chamber and a 2:1 ratio used in other bandpass alignments.

off axis radiation from the cone/coax horn/K-tube will bounce around and some energy will escape from higher up the slot. Places where the slot width is smaller than the wavelength, horizontal polars can be wider than a direct radiator. I suspect cavity shape and its various depth vs width, height and distance to the tapered aperture play some role but I don't have the skill/brains to model it.

K15 and K12 seem well picked for size. Fixing driver size and making them larger in the original form may not be productive overall. I would say there's sweet spots for sizing. At some given point in bulk, a horn or 1/4 wave type (or even reflex) will go lower and for small horn and a cut in sensitivity a direct radiator will outperform the horn.

It could be useful to try several variations in aperture as that can affect the subjective impression of a Karlson type - also play with the initial gap. Even one set of test wings could be swiveled upon cleats a bit to get some adjustments including the starting (top) aperture gap.

If MMJ and xrk971 had some spare time, I'm sure they could elaborate past my crude ramblings. It would be interesting to have MMJ look at the new feature in hornresp and see if his model for the Acoustic Control 115bk Karlson cabinet can be further adjusted to see effects of vent size, etc. With the current MMJ/115BK model, I think it may be pretty accurate but when the little 115BK is scaled to K15 bulk, the resultant "cabinet" will be tuned a bit lower than K15 so there could be a droop in LF if a low mass low Q 15 were employed vs the same speaker in K15. A 1.2 scaled 115BK does look pretty good for some 18" speakers. (X would know what might be changed in 115bk' form to raise tuning a bit)

High moving mass drivers didn't exist when Karlson and Wayne Green made K15 in the summer of 1951.

although MMJ's schematic doesn't look like a K - it seems to behave pretty close to a real 115BK
(it would be good to get MMJ to explain the areas - I of course can see the ~27 sq.in. vent part)

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Last edited by freddi; 15th February 2019 at 04:23 PM.
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Old 15th February 2019, 04:25 PM   #1246
xrk971 is offline xrk971  United States
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There is a non-dimensional curve (somewhere in one of my K threads) that I fitted to the original K15 aperture that I use in the sims. But in practice, I find that it is easy to free-hand it with an arc tangent to cusp slot and transecting the speaker driver surround near the 10 and 2 o'clock positions.
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Old 15th February 2019, 07:30 PM   #1247
freddi is offline freddi  United States
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back in the days when Job Ulfman's Karlson Speaker Project's forum was open, Ken Lehman was experimenting with what was called "trax30" and "trax60" apertures. Carl Neuser iirc, would make up sets of radial, exponential, P=1/Q= 1.7 (which like Karlson's X15 aperture, opened faster than strict radial arc starting around the half way point down - maybe Karlson did that to better fit X15' Ktube into the aperture) and P=1, Q= 3 curve (a tighter curve). I have a little DOS routine where one enters the type of curve, 1/2 the starting width, 1/2 the final width, aperture height and increments.

also an aperture as below could be useful in some circumstances (w8-1772 sounded better to me in that little cabinet than in the old 1955 Karlson 12.
I did like FFE206en in that K12/"Karlsonette"

Click the image to open in full size.

Here's an SK6.5 with curved reflector - that was scaled from one of Carl's HAK8
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

Last edited by freddi; 15th February 2019 at 07:49 PM.
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Old 16th March 2019, 10:04 PM   #1248
freddi is offline freddi  United States
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I wonder with smaller Karlson if the "Dutch K12" approach with no "upper reflector" board and no tilt on the port board gives less ripple than canting the port board 10 degrees forwards as with the 1956 - onward K12 ? Seem like a "cupped" upper portion of the cavity could invite stronger resonances (?) With my 41.5" tall K18, a curved reflector seems good and may subjectively enhance its sound. (I could use a "Dutch K12" as a reference - maybe might try to convert one of the first K12 to its vent would be close enough -?)

X -what's your views on how one might make a small K that measures nice without deep dips or ripple ? Adding a stub to the front chamber is one way - - Acoustic Control's 115BK , the Transylvania Produce and other X15 derivatives built like 115BK are pretty smooth.

I'd like to get some of this solved while still alive
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Old 17th March 2019, 04:23 AM   #1249
xrk971 is offline xrk971  United States
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Anytime you put a K aperture in front of a driver, it won’t be free of dips. But those dips are narrow enough that musically, we don’t seem to miss them. The benefits of increases cone control, and enhanced polar directivity seem to be greater benefits than monitor studio response.

As far as compact and deep bass, pick a driver with a lower Qts and smaller Vas and low Fs. Hard to find maybe but those are what will do the trick.
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Old 17th March 2019, 04:38 AM   #1250
freddi is offline freddi  United States
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in little K's and a long time ago, Carl Neuser was using a 10" Scan Speak
woofer. His direct radiating boxes used 4 per side and with "Variovents".

I think Acoustic's 115BK is very smooth - but don't know if it would directly scale up or down and still stay that way. (maybe - to a point ?)

- dunno if thejessman is accepting any builds or not - I might have missed the window of opportunity for this year.

The late Ernst Beck made a little K like the Transylvania Power Company, Westwood, Acoustic , KK and others (whew!)

in this picture the coupler looks larger than that little box - but may be a camera perspective

Click the image to open in full size.

Last edited by freddi; 17th March 2019 at 04:41 AM.
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