New sub design? Constricted Transflex, simple build (series tuned 6th order)

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Hi MMJ - wonder how it would do with K15 input shortening the stub? - K15 has a long "shelf" which forms the lower boundary of its inter-chamber port. I think K15 was tuned around 48Hz - maybe a hair lower. The change in its port from 40sq.in to 32 didn't affect
tuning nor cutoff - but rather how much "back wave fill" was happening (if my assertion makes sense - ?).

is there a scaling factor built into your model for the front aperture area? K15 as below lists 1432 sq.cm.

Would you mind taking say a Delta 10a and coming up with an example?


K15 by Carl's estimation

vf (front chamber) = 2.3 cu ft ~65.13 liters
vb (rear chamber) = 4.0 cu ft ~113.27 liters
sb (inner vent) = 32 sq inches ~ 206 .45 sq.cm after 1956 changeover - 1954 vent was 40 sq. inches -~258.06 sq.cm.)
sf (aperture area) = 222 sq inches ~1432.25 sq.cm.

The rear shelf creates a port area of 52.5 sq inches with the back of the cabinet. This area is sometimes smaller and can be tweaked with good recordings of drum and plucked bass viola.

The front shelf creates an area of 73.5 sq inches with the wings.
 
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if the new model works, then a heavy cone 15 such as B&C 15pzb40 should play pretty well in an 80-some liter Karlflex

MMJ - if you get time, a new thread explaining how to use and adjust the model would be interesting.

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if the new model works, then a heavy cone 15 such as B&C 15pzb40 should play pretty well in an 80-some liter Karlflex

MMJ - if you get time, a new thread explaining how to use and adjust the model would be interesting.


Freddi ,
I can't be sure about the K-15 without seeing a drawing (to determine if we could really find a way to model it) but as far as modeling your B&C 15pzb40 or Delta 10a in a K cabinet with Freddi-Mod Stub it should be no problem at all .. .. It should be straightforward..Lets do it! :happy2:

The only area which we cannot model accurately in Hornresp is the K-Aperture and slot section, but we have a pretty good idea of it's influence and effects in a system like this so we can make this work :) .

A lot of the front chamber's volume can be contained in the Freddi-Mod stub so the driver's baffle should not need to be as deeply recessed as we see in the classic K cabinets .. ..

I can figure out the optimized rear chamber volume, interchamber duct requirements, stub geometry etc, and if you would like to help me come up with cabinet dimensions & layout based upon that data then this should be a fun collaboration :) ...

Let me know which driver you would like me to start with ... The B&C 15pzb40 or the Eminence Delta 10a , pick one and then we will focus on that until we have the plans worked out :smash::wrench:
 
Hi Matthew - since I'd like a two way with K-tube and keep it smalll enough where I might move it, lets go with the Delta10a (maybe it can double with some other 10) It would be nice to have space to internally mount the K-tube. (I would like a 12 or 15 based cabinet at some point)

Here's a Delta10A in a "K10" sized coupler. The front chamber is ~ 0.5 cubic feet and rear about 1cubic feet. There's no front shelf - there is one in the rear. Its heavy being made of 19mm BB. I htink it exhibits a bit too much output around 210Hz.

According to Karlsoin's 1961 letter to the late Martin C. Poppe. I get the idea that these shelf pieces were to lessen the effect of standing waves.

I have one K15 size cabinet without shelf and the front shelf when inserted lessned a response hole in the 200-300Hz region. It had little effect bekiw that point.

Subjectively speaking, although I could not measure significant looking differences from a few mic points, the aperture - espedcially the first ffew inches, had significant effect on the sound - so its good to have removable wings - at least til desired results are obtained. It may alsop be a good idea with K15 sized couplers without the front shelf feature to keep the cavity depth a few inches less than with K15. Lessing the baffle angle to 20-25 degrees can help.

What are your thoughts on the fornt chamber of a Karlson type in general and what are they with respect to cabity shape and aspect? With Karlson's heritage line, I get the idea that K12 is just getting large enough for the front chamber to do some real upperbass help - and its only around 0.6 cubic feet and K15 with 2.7CF, has a very adept upper bass plus reasonale LF extension.



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Thanks Matthew.

Will the new model's output give a direct translation including port dimensions to a basic Karlflex's construction? (shown sans offset feature below)

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Fred could the stub be removed from the top of the cabinet and placed inside the cabinet with the closed end facing the woofer along with a small bend upward at the back of the box and over all cabinet volume adjusted to compensate for the stub volume? It seems a better or more natural position to me , alternately it could be placed on the bottom of the cabinet with the stub opening at the rear of the cabinet floor directly behind the woofer. What do you think of this idea?
 
hi Moray - seems like that would work although, more coupled to the rear chamber than front and the front can provide the peak. (would that make a difference?)

I'm interested also in the "reflector" in regular K - how should it be shaped and where should it focus?

Here's K15 from the Janyary 1954 issues of Radio & Television News

https://elektrotanya.com/PREVIEWS/6...lson_esearch_k15_loudspeaker-box_sm.pdf_1.png

fwiw I think cavity depth would need to be lessened if making a K15 without fron chamber but one
builder of a "Fig.6" K15 is very happy with the chamber

u52f7AY.png
 
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hi Moray - seems like that would work although, more coupled to the rear chamber than front and the front can provide the peak. (would that make a difference?)

I'm interested also in the "reflector" in regular K - how should it be shaped and where should it focus?

Here's K15 from the Janyary 1954 issues of Radio & Television News

https://elektrotanya.com/PREVIEWS/6...lson_esearch_k15_loudspeaker-box_sm.pdf_1.png

fwiw I think cavity depth would need to be lessened if making a K15 without fron chamber but one
builder of a "Fig.6" K15 is very happy with the chamber

u52f7AY.png

when you say the reflector are yu referring to the horizontal shelf above the woofer and if so the front half, the back half or both sides?
 
if we go by Karlson's 1961 letter to Martin C. Poope then perhaps it included the entire cavity shape so with the 2nd K12 the 10 degree forwards slanted port board is the reflector. Would K15 (1951) and the first K12 (1954) have what we can call a reflector?

In Karlson's final installment of "Acoustic Transducers", JEK said curved reflectors, shown as Fig.6 and Fig.8, could improve response and polars. The "Dutch K12" is an illustration of what Karlson said would have poor response. I'm not so sure on that and might expect a smoother response from the perpendicular panel than an unfavorable cavity shape which could exacerbate a peak.

In some K, port size seems to matter with regards to filling in a potential response hole. Acoustic Control's 115BK being X15 size, has little LF extension, but is quite smooth.

I do think curved reflectors may have use in K-type and may include curving the junction between the sidewalls
and baffle board.

Hopefully MMJ wil have some thoughts on what a favorable front chamber shape might be for the K with stub project.

If one isn't trying to get much LF extension, then Karlson's little K12 is a pretty good pick. Have you heard the Dutch K12 for comparison ?

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Good news .. It does work well .... We have tested it

... could the stub be removed from the top of the cabinet and placed inside the cabinet with the closed end facing the woofer along with a small bend upward at the back of the box ..........alternately it could be placed on the bottom of the cabinet with the stub opening at the rear of the cabinet floor directly behind the woofer. What do you think of this idea?


Moray James ,

What you are describing does work and has been done ... It was what we called the Karlflex (short for Karlson-Transflex) , and i built the prototype and tested it ..... You can find the plans and revisions including the Freddi-Mod stub posted here in this discussion , but it was a while back now..

It was optimized using Akabak ... The rear section was basically an offset-driver QWP (OD-QWP or OD-"TL") so a quarterwave based cabinet but in the form of a series-tuned 6th order design because there was also still a front chamber section...... This front chamber section was given it's own stub (which we called the Freddi-Mod stub because it was his idea to place the stub in the front chamber , and it really did help the design , especially because the earlier revisions of the design had initially lacked front chamber volume) .....

The stubs were stuffed with fibrous damping material ..

What we found out through lots of modeling is that the offset stub in the rear chamber section isn't as necessary (is somewhat redundant) when we are already using the Freddi-Mod stub in the front chamber section ..
 
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Hi Matthew - since I'd like a two way with K-tube and keep it smalll enough where I might move it, lets go with the Delta10a

Ok , Delta 10a it is! :)



What are your thoughts on the fornt chamber of a Karlson type in general and what are they with respect to cabity shape and aspect? extension.

I think the front chamber/aperture/slot in the K cabinets is a clever way to accomplish a series-tuned 6th order cabinet in which wide bandwidth is made possible because of the the way the higher frequencies are allowed to propagate through the slot which also happens to make our horizontal coverage more consistent at the cost of some amplitude in the upper midrange (thus the need for drivers with abundant upper midrange sensitivity in order to balance the system out and give us the useful upper extension) ..

...

Freddi, We should probably stick with the classic chamber volume ratio , which if i remember correctly you said is around a 2:1 ratio in the traditional cabinets, but it is important to keep in mind that the Freddi-Mod stub counts as part of that front chamber volume so the proportions of our cabinet design may look a little different than a classic K, but really aren't different :p , we will actually be sticking to the classic formula in that regard. :checked:
 
If a Karlflex 10 is pursued, then hope the resultant speaker will be able to sound good on bowed and slapped bass viola plus things such as Beethoven's sonatas for cello and piano. Also it must play the drumkit at high levels

My Karlsonator12 is tuned around 37Hz - far too low for some 10 inch drivers such as Beta10cx, plus unnecessarily large.

Delta10A played free air with pink noise and without a lowpass filter is an awful sounding thing. Matthew - do you think careful selection of a lowpass filter will corerse it into playing nice? (its cousin a Deltalite, has been used in Econowave builds)

Also can you envision a way to internally mount a compression driver for a K-tube? Transylvania Power's "The Tube" had a length of about 5.3" so a short stub to lengthen the K-tube would allow it to reach into the main aperture;s plane. Alternately , its easy to mount on top and that of course removes the K-tube from influence of the front chamber.. (They sound fine "IN: the front chamber). Since K-tubes are dinkyh things with little surfacce area, when using a tube on top, a baffle at the driver's exit plane could probably improve the blend with the woofer K-coupler.

For fullrange 10 , my old AN10 could be tried.

For some reason, it might be easier find 12: which have potentially better sound quality than 10" but something like 12LTA would be trounced by a good 10 for dynamic attack. For heritage Karlson type a 10" seems about the smalliest driver which can play a drumkit's mounted tom.

5/8 plywood has some flex - folded horns pretty much self brace. It would be nice weight wise to do the cabinet in 1/2" Baltic birch provided it can be kept from undue flexing with 200 watt input peaks. 19mm for a little cabinet with small spans can get by without much bracing.

I also have some old P-Audio neodymium SN10C coaxial which could work. I think their motors are a bit stronger than spec - but still rather moderate-high in qts.

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1 15 inch Karlflex coud be interesting - guess it would be in-betweem X15 and K15 size. Here's asim with JBL's 2035H (which I have in 4638) - its rated only to about 1200 but sill might sound decent. Re is rather low at 3.9 ohms so might be called a 6 ohm driver.

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Peerless's Tymphany 10 should make a good little Karlflex for sub sat setups

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The 15 inch cabinet might be reduced to 97 liters airspace. With a 46 liter rear chamber
I don't know if the real LF would be as good as the model. From what I've seen with Akabak,
Akabak can miss the mark for a K's low and and input impedance. A fudged hornresp model
might (?) be better - haha

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