monacor advantage system

james, ind.st wrote: "big learning curve" are not inspiring words to be hearing at this point in my life. AJHorn sounds worth a go, but it is off-axis response that particularly concerns me here. what i need to do i think is determine the frequency range the 8" will be playing. i like the idea of the 2" above it playing to around 2k, or just before the sound gets a bit metallic, but will the (active) crossover point with the 12" be determined by the power handling of the 8" horn at lower frequencies? power from the 12" to match can be dialed in to suit. objectives are becoming clearer for this (ambitious) system design, and i'm finding that is really helping my understanding of how to evaluate the specification of various components. i am working towards an ultra-small footprint, high portability, visually imposing stack capable of high spl in small venues and adequate levels for outdoor general public address and sound reinforcement. horn mid and top section to have excellent useable horizontal dispersion to <-10 dB @ 90 degrees across the whole frequency range. excellent separation and clarity in vocal ranges are desired functions, resolution of acoustic instruments and percussion with a bright but not over imposing sound would be nice. the bass section does not need the brutal front and projection of a horn system. for those events i have my other system. high bass will need to match system power from 80-90 Hz (how high should i tune the reflex response of this element in order to preserve low level full range operation?). ultra compact subs to be optimised for high fidelity with useful output down as low as practicable. this will be at the expense of transient response, for hard dance music in a small venue the 12" must take care of the punch. performance optimisation will lean towards fidelity over spl. i love this, the more i look (and ask) the more i see, the more i see, the less i understand. james.

Build a ~400hz conical midhorn and dont worry about dispersion,just copy others like Graeme or Adrian.

the 8" on horn will be loaded to near 400hz,excursion will be minimal,thermal power handling will be the limitation,but because below this theres a 12" direct radiator-the limitation will be the 12"

12" tuning will simply depend on its parameters. What F3 do you desire?Make the response flat to ~70hz etc-this then can form part of the xover function to the subwoofers.

http://www.centauriaudio.com.au/diy

http://www.geocities.com/adrian_mack/homepage.html

having just found the cursor tool on bass box pro, it is indeed 65 Hz. not
good. i have spent ages trying to tune the box lower and am coming to
the realisation that it is too small for that. the Vas of my fanes is quite a
lot more at 444 litres against 333 for the monacors which i don't suppose
helps. firstly, can flat response be managed at reduced output in a box
this small?

then i tried isobaric loading in a 184 sub. mild port tuning rendered +/-
1 dB from 40-110 Hz. not loud, but looking smooth. the 184 is slightly
smaller than 2 advantage subs (good for transport, bad for carrying, less
stacking height) but isobaric loading?

clamshelling drivers has always held a fascination for me, but i know you
do it at the expense of output. better lf response with tighter cone control
are the potential rewards if i remember correctly.

if i'm going to put 2 18" drivers into a box 864 x 615 x 536, that might
not be the best way to do it. imagine an infrabass type arrangement, or
triple chamber bandpass.

the reduced height seriously raises the issue of low mid projection. in
light of that excellent conical horn article (i had assumed tractrix would
be necessary for dispersion) the top might need a bit of layout
modification with the 8" horn going up top. problem then is, where do
you put the slot?

ha! i've also just noticed you can't fit isobaric driver loading in the 184!
back to the drawing board...

james.

There is a trick to tame those becasue they result in really nasty resonances. Drill holes in the port at the presure maximum of the first mode (might require some experimentation to get in just right.

as it happens the drivers in question for this project are the fane classic
kc18-300c, by virtue of the fact that there is a large pile of them
gathering dust in my man's store so the price is right. $58 is good, as are
those dimensions, but i live in the uk.

600 W into the pending isobaric design is looking at producing around
122 dB at 1 m flat from 40-110 Hz. the rcf 12" in the top with Fb 70 Hz
will do that without a crossover when driven with 250 W, crossed with the
subs at 80-105 even response will be achieved with less power still. so
far so good. assuming the port resonances can be tamed during the box
and port tweaking phase, i think i have found my subwoofer element.

it seems odd to sacrifice 124 dB output at 1 m from only 300 W from my
best working of a fane in the single compact box, but that is still only at
65 Hz and by 40 you are 10 dB down. reflex bandpass things don't get
more lf from grouping (?) so if i remember the trick is to tune low.

now i see that the standard monacor sub design is all about output for
size. i want fidelity and extension, if anything just to see what the fuss is
all about.

potential problem. dod active crossover proposed can offer lowest
crossover point of 750 Hz for the mid-high. i was thinking of ~400-2k
for the 8" mid horn. this will determine the demands put upon the 2"
from a passive crossover perspective. the rcf has good rich tone up to
1.5k though, would 750 Hz crossover work?

james.

as vaguely stated elsewhere i have realised that i need to do some
subjective listening tests. i can't ask people here to tell me if a power
trade of for lf response is right for me, but you can keep me in check with
regards the laws of physics and sound reproduction.

i have two workings of the same 150 litre box. one is a slight
improvement on 65-100 Hz response but basically the same as the
monacor box, the other is less output but f3 of 40 Hz. when i have time
they can be prototyped and then i shall report my experiences and
findings.

in the meantime, less dreaming, more woodwork.

james.