Plan ! - D-20 (hz) Macro Sub ..tapped horn by moi.

cut a really lopsided pipe - its 138 sq.in. (Sd) right above the cutout, 17.75"wx47.75x15.25" external - not sure what aperture to try first  - its lopsided and still wet - hope it doesn't rattle much

http://img230.imageshack.us/img230/1069/krap15.jpg


Edited by freddi - 27 March 2009 at 2:59am

theres a brace starting at ~19" from the cabinet's floor so I can't go up much - - I usually run TrueRTA sine sweeps outdoors - pc is messed up and lost one channel of a NAD amp - - regular Karlson just about require full height slotting - this one for 18" was 42"H x 22.5W x 16D - just blocking a few inches of the top portion of slot seemed to "slow it down"  -why?  - -its well behaved on big drums - far better than reflex and cleaner sounding in ways than my Klipschorns - there's about 30 sq.in/ of port - it needed to be deeper than the 0.7" material thickness as it was tuned too high  - -- the slotted tube  HF waveguide could go inside  right above the  woofer.   Slotted tube sound good above 1K6 - the board above the 23 degree woofer panel tilt's forwards by ~6 degrees and theres a curved reflector above that panel.   It was an experiment to see what happens going a bit taller aspect-wise than K15 and Fig6 of patent 3540544

one thing I didn't think about whe cutting the panels would be to put an opening on the backside via removable & switchable panels - - that way your inverted tapped horn could also be a regular tapped horn within a couple of minutes

here we go - input impedance of the inverted tapped horn with Martin 1844 for three different rectangular openings - the 3rd Z peak @~124Hz stays "about" the same - what do you think of the Z- curve?  like the idiot I am I undercut the mounting hole so it won't accept my crappy high mass but long xmax B&C - - subjectively its a bit difficult to tell which aperture is best just running YouTube bass tracks - it could use some truncation down from the full opening without the stub - it seems to have good power and not much cone excursion


FWIW = here's a near aperture (rectangular mid-size) graph of the 4.1mH 1844/15269 Martin woofer without and with some polyfill at the line's beginning - my mic moved position so one trace has more dustcap output -- looks like the 3rd Z peak area is about where it gets rough - its got a phat sound and pretty good LF extension-  this was 1/24 octave


with 1/3 octave smoothing it would look like this - LOL


maybe the slotted stub will help too - gotta dig out a couple more woofers

ah - here's an old Dayton 295070 with ~28Hz fs, 2226-like specs - 1.4mH Le, crappy mids run high vs 60g mms woofers compared to the 4.1mH low fs Martin 1844/15269  1/24th octave- - - no slot yet - not too shabby


input Z for 2950-070 with medium rectangular aperture


response 295070 vs 1844/15269



Edited by freddi - 28 March 2009 at 12:21am

Hah.

by pipe you mean the variant of the boxes you built ?

ill look tommorow sometime with the drivers youve tried, specs handy if not readily avail on web.

or the karlson ?
the carlson couldnt really be modelled in horn resp to my understanding..
mind, if anyone knows of an accoustic equivalent for one in akabak, let us know.. as that could be awfully fun if available ;) :)

well, the model seems to correlate to the graphs round about right :)
ill run over the no's tommorow, though you'll never get the sims to match 100% results with things like this; as theres always something odd at play with this sort of box. just expirment :)
kind of an odd choice to tune so high for this fold, may want to drop lower if you can & see what happens; though dont build anything you dont want to :)

well, the most literal way to interprit the size of the mouth is to firstly ignore any slot added, work out the area of the mouth at its narrowest point, & then add this area to that of the slot. this can be taken as the largest area the driver will see the slot as, however it may well behave as slightly less.

however this wont take into account additional loading effects of the slot, which mostly consist of improving the output further up, upon where the loading the air mass infront of the driver comes into play.