New sub design? Constricted Transflex, simple build (series tuned 6th order)
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Matthew Morgan J
diyAudio Member

Join Date: May 2011
Location: Arizona
Quote:
 Originally Posted by freddi Questions MMJ - what are we looking at with Ap1 and its length vs the schematic and does its identity explain why there's little variance in response as Ap1 is varied over a 3 to one ratio?

Freddi and Bp1Fan,

Ap1 is the duct's area so if we increase it beyond the area of S2 we will see less effect at some point ...

 21st June 2019, 12:44 AM #2202 freddi   diyAudio Member     Join Date: Aug 2005 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. Last edited by freddi; 21st June 2019 at 12:47 AM.
 23rd June 2019, 07:58 PM #2203 freddi   diyAudio Member     Join Date: Aug 2005 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.
Matthew Morgan J
diyAudio Member

Join Date: May 2011
Location: Arizona
Quote:
 Originally Posted by freddi 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!

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

BP1Fanatic
diyAudio Member

Join Date: Jan 2009
Location: Columbus, Ohio
Quote:
 Originally Posted by Matthew Morgan J 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 :
How about breaking the slot up into stepped sections × the thickness of wood?

 28th June 2019, 05:14 PM #2206 freddi   diyAudio Member     Join Date: Aug 2005 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.
moray james
diyAudio Member

Join Date: Aug 2003
Location: Calgary on the Bow
Quote:
 Originally Posted by freddi 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)
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?
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moray james

 28th June 2019, 07:31 PM #2208 freddi   diyAudio Member     Join Date: Aug 2005 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/63...x_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 Last edited by freddi; 28th June 2019 at 07:58 PM.
moray james
diyAudio Member

Join Date: Aug 2003
Location: Calgary on the Bow
Quote:
 Originally Posted by freddi 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/63...x_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
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?
__________________
moray james

 28th June 2019, 09:26 PM #2210 freddi   diyAudio Member     Join Date: Aug 2005 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 ? Last edited by freddi; 28th June 2019 at 09:30 PM.

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