Superscooper 18 Discussion/Scoop Design

I used measure suggested by you. smiley2
gap 20.2
width 60
throat 10.5
compression ratio 0.191:1
vtc without driver 68 liter

As obvious.. only difference between "A" and "B" is slightly changed angle of panel "g" and "d" and enlarged corner pieces on version "A" to act as "reflector" rather than bend so this causes some more noticeable area unevenness and bit of "negative expansion".

In theory bent-reflector approach makes sense if we trying to improve higher freq. range of that horn (by reflecting/inverting higher freq. waves to prevent self-cancellation within horn due to path length differences created by folding)
quick googled example;
www.volvotreter.de/downloads/Edgar-Monolith-Horn.pdf
community.klipsch.com/forums/p/126438/1278103.aspx

In simulations (theory) all differences in bass response graph are so minor (considerable same built quality, throat/horn length/mouth unchanged) ..that it is really doubtful will it even be noticeable in practice... but, than considering experiences, seeemms that there may be "something" :think:

Even considering that bit with negative expansion (ignoring "reflector") may act a bit as low pass filter while bass waves will "ignore" such slight unevenness in horn area.
..Than looking that from bass-reflex (weird:) ) point of view smaller duct area brings lower resonance (but in horn.. theory says that this effect will be swamped by whole horn air mass..) ..etc smiley23

Appears that scoops are very interesting and brings so much "emotions" because of fact that some little important details and behavior cant be fully simulated and universal simple recipe written.

My general thought.
Such old and simple design.. but each builder builds in little part of own ideas (and soul smiley1 ) which theory and/or own experience tell him will do the trick.. at the end we have overall very similar but in final tonal character different cabinets which can be looked more as fine tuned personal instruments than "just another bass cabinet" .. same as wit drum set , each drummer will tune them according some general rules but that final personal tune-touch and way that they play set will make them recognized as "their" sound.
Maybe that makes scoops so interesting ...

bitzo wrote: I calculated the throat from db keele formulas and it's really smaller than 10 cm for pd1850, about 5 cm for pd186 is 9 cm so I get this result but the cab is really deep about 90 cm.

So I have to work another time on pd1850 but to get the best efficient throat using keele's formula I'm thinking to change the layout. Dogleg returns..... smiley15

As a I said....dogleg return I calculated the throat from keele formula and modeled the cab...with a smaller horn I can reach more spl with less horn lenght (about 130 cm) using same vtc and mouth.
on the left rcf lf18n451, on the right b&c 18sw115

what you call negative and what I call negative are two different things, but this is your negative expansion see diagram. What you call negative expansion is two positive expansions connected in series

what I call negative would be a area 'the same' at the beginning to an end before positive expansion, like 10 to 10 along a given length then expand, or, 10 to a lower number then expanding again like Ligwa scoops :oops:

should say "your negative expanding scoop'

I mentioned a month or so ago to lev that the Emi scoop was about 3 db down on a positive layout. So maybe not as loud but sounds warmer, psycho acoustics again or a BP effect smiley20

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So in in staip scoop version A we have a jbl-Ass style right? version b is traditional scoop?

yes, exactly right

I always use B layout for my scoop designs

an obvious question.... why?

because you never see brass instruments (trumpets) with kinks in them or negative expansion smiley20

so in order to avoid any negative o jbl expansion you don't have to use 45° corner braces but particularly degreee for each corner brace

mykey- wrote:
I mentioned a month or so ago to lev that the Emi scoop was about 3 db down on a positive layout. So maybe not as loud but sounds warmer, psycho acoustics again or a BP effect smiley20

Remember Mykey, the "only" reason Reggae/dub sounds "still" use scoops is the unmatchable efficiency.

No one I know would want "quiet" scoops :lol: , or would it would mean taking out more cabs, and then problems powering them on UK 13A sockets.

Especially as shortman mini can keep up with many full scoops.