MJK simulations - double mouth back loaded horn help.

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gafhenderson

Member
Joined 2012
hi,

i hate to ask this but could someone please check if i'm using these spreadsheets correctly please? i really don't think i'm doing it right at all.

i've attached the sketchup doodle in the link below, and my 'calculations' for it using the MJK sheet.

relevant driver information, i am also aware that the driver isn't really suited for horn use.

Fs - 50hz
Re - 7.2
Lvc - 1.56
Bl - 12.81
Sd - 530.9cm^2
Vas - 78.06
Qed - 0.72
Qmd - 7.6
Qtd - 0.658

any help is extremely appreciated as always. thanks :)

double back loaded horn.skp

An externally hosted image should be here but it was not working when we last tested it.
 
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gafhenderson

Member
Joined 2012
planet10 said:
MJK doesn't care what we call the box... it is fairly accurate if the geometry is correct.

I do know that when Scott does designs like the 1st he has some home-made tools he also uses.

dave
Click to expand...

thanks again for the watchful eye.

would this be worth building as a practise type exercise? i have utterly no idea what a speaker of this creed actually sounds like (good or bad), everything i'm used to has been generic bass reflex ported things.
 
planet10

planet10

frugal-phile™
Joined 2001
planet10-hifi.com
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A BR is usually tightly tuned to a set of T/S parameters. But T/S are not scalars and they change as a function of how much drive (and weather, and, and...). The BVR & my miniOnken (and some others) essentially add an R to the vent, giving them a greater tolerance to changes in T/S under dynamic conditions (ie music)

dave
 
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gafhenderson

Member
Joined 2012
GM said:
I don't have any MJK software to sim a double BVR, but at a glance I'd start with ~5.52 ft^3 net/35 Hz Fb.

GM
Click to expand...

i'm trying to stay within the 1mm threshold i've set to get reasonable listening volume and enough bass extension to 'blend' in with the sub. designs that go that deep always seem to nuke the budget before any real noise level is reached.

i took on board what you said about being flat from 60hz - 300hz then rounding off to 40hz and tried to find a compromise of that brief based upon my current incompetence.

the curvy one gets me down to 70hz flat(ish) then has dropped 5db by 50hz.
90db simulated @ 50hz, above the bass range it sims flattish @ about 93-95db @ 1watt. if i take it up to the 1mm excursion limit i placed on the design that adds nearly an extra 10db to the numbers. is this a reasonable compromise of your previous design brief?

the sub sims fairly flat from 28-90hz @ 98db for 1 watt. i was thinking that the combination of the 2 would be enough?

thanks for your help :)
 
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GM

GM

Member
Joined 2003
I forget what all I've posted as you've started a number of threads only to abandon them, but IIRC I posted that you ideally want at least an octave of ~flat BW on either side of the XO point, so this requires a good size cab/low tuning plus this high a Qts driver really wants a much larger cab tuned even lower to keep it from sounding 'boomy'/'loose', which will ripple up through the BW even limited to 1 mm if not fairly well damped with stuffing. For sure, the posted sim XO'd to a sub wouldn't sound good in my acoustically larger than average room.

With a sub covering up to at least 60 Hz, its overlapping BW will help with the power handling and probably allow another 10 W or more to reach the 1 mm limit.

Dunno, you don't ever post any useful design data, but short of stuffing the @#$% out of it, I don't see how this driver can be flat enough in any high tuned cab, especially a BVR, which IMNSHO is a waste of time/materials for this app.

GM
 
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gafhenderson

Member
Joined 2012
GM said:
I forget what all I've posted as you've started a number of threads only to abandon them, but IIRC I posted that you ideally want at least an octave of ~flat BW on either side of the XO point, so this requires a good size cab/low tuning plus this high a Qts driver really wants a much larger cab tuned even lower to keep it from sounding 'boomy'/'loose', which will ripple up through the BW even limited to 1 mm if not fairly well damped with stuffing. For sure, the posted sim XO'd to a sub wouldn't sound good in my acoustically larger than average room.

With a sub covering up to at least 60 Hz, its overlapping BW will help with the power handling and probably allow another 10 W or more to reach the 1 mm limit.

Dunno, you don't ever post any useful design data, but short of stuffing the @#$% out of it, I don't see how this driver can be flat enough in any high tuned cab, especially a BVR, which IMNSHO is a waste of time/materials for this app.

GM
Click to expand...

i abandon them as the design etc are deemed fairly useless so i don't see much point in flogging a dead horse. just start fresh and try again.

what data do i need to post for my posts to be more useful? i've only been looking at doing this for a few months, i need some pointers on how to do stuff around here. its enough of a struggle just to keep up with all the abbreviations.

i'll have a go tuning it lower as per your advice and see what happens.
 
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kctess5

Member
Joined 2011
coreyhwalsh.com
Is the geometry on that sim pretty much the same as the previous one only with a lower tuning or is it different? If so would you mind posting it? That looks like a pretty good response for a full ranger, down to 30ish hz you could probably even get away without a sub for music. What driver is this? I saw the t/s specs I'm just wondering the model. I'm wondering how the excursion would do down that low...
 
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gafhenderson

Member
Joined 2012
kctess5 said:
Is the geometry on that sim pretty much the same as the previous one only with a lower tuning or is it different? If so would you mind posting it? That looks like a pretty good response for a full ranger, down to 30ish hz you could probably even get away without a sub for music. What driver is this? I saw the t/s specs I'm just wondering the model. I'm wondering how the excursion would do down that low...
Click to expand...

no, its a very large internal volume increase and the horny bit is different, its also not the curved shape at present. i am awaiting GM's guidance to see if its worth tweaking further around that design etc.

fane sovereign 12-200lt.

it gets fairly low without exceeding the 1mm of excursion with 1watt, i'll post up the excursion figures later when i boot back into linux.

to be perfectly honest, i'm not expecting much from this driver or the cabinet, its purely to test and learn a few things that i'd be looking to employ at a later date on more exotic drivers, mainly cone size and enclosures and the EnABL process.
 
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