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best choice for a 12" horn plans

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DMorison View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 2:42pm
Originally posted by _Natty_ _Natty_ wrote:



For mids, you should really model in 4pi (full space) not 1pi (corner space) unless you have a very specific fixed installation location that you're designing for.

I'm not sure how you got 1444 as S1 - from the pic you posted it looks like S1 would have to be bigger than the combined area of the two 12's without any constriction at all - which would be over 2048 (32
x 64cm).

Also, it'll be very difficult to make a rear chamber as small as 7.2 l for two 12" drivers - and if you succeed, there's the chance you'll have overheating problems from them being in such a small closed space. Try doubling that at least.

Might be worth searching for the input parameters for the SMT212 design to see how to at least start getting some realistic numbers for your model.

HTH,
David.


Edited by DMorison - 19 October 2017 at 2:49pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 2:52pm
ok sorry you told me already, it was just a quick test... my fault next result
next result:


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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 3:19pm
the air volume occuped by my driver is 3,3 liters
I've found a project that used a sealed box for this driver of 0,13 cubic feet, using google converter i got:  3,68liters
So i put X2 and thats is the back...
even smt 12 seems to have a little space for the 12" section.


I'm not sure how you got 1444 as S1 - from the pic you posted it looks like S1 would have to be bigger than the combined area of the two 12's without any constriction at all - which would be over 2048 (32
x 64cm).

As i said the pic is just to have an idea! the s1 is smaller, and again as I said I'd like to test an horn not  a wave guide like smt
I start from sealed back chamber then ill made some test with reflex too.


I need to understand if its the right way to simulate a x2 12" enclosure!
and if its possible to add the air reduction of the horn in the caulculation
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 4:09pm
Acoustical power:
Tools>>directivity>>response.
But it is just rough idea to see if driver will work.

I have plans for 2x12 but this one is HUGE.


Cant give you phase plug part though.

Keep in mind dimensions on the right are half of a horn.
Placing Hf inside horn obviously will something as its source of standing waves.

Edited by gen0me - 19 October 2017 at 4:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 4:15pm

to high! ive maybe 100/110cm to use for all the cab!
some place where I play are so small!

what is this program for simulating?

cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 4:17pm
Abec.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 4:22pm

thanks ill take a look...but seem expensive license
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 20 October 2017 at 1:48pm
Originally posted by _Natty_ _Natty_ wrote:

the air volume occuped by my driver is 3,3 liters
I've found a project that used a sealed box for this driver of 0,13 cubic feet, using google converter i got:  3,68liters
So i put X2 and thats is the back...

OK, rule 1: don't believe everything you read on the internet ;-)

Let’s do the math for ourselves:

You’re using the B&C 12MH32 IIRC, which has a chassis diameter of 316mm and an overall depth of 133mm.

So, assuming you build a rear chamber that is square & reaches to within a few mm of the driver itself, you’ll have, at the very smallest, 32 x 32 x 14cm gross, or 14.33l, before you subtract the 3.3l for the driver to get 11l net.
(That means my earlier recommendation to double up to about 7l per driver was already optimistic - an example of why you should always do the math and check for yourself - see Rule 1 ;-) )

But, most modern drivers rely on cooling the voice coil through vents in the pole piece to the rear of the driver, so we can’t just put the back wall of the rear chamber only 7mm from the back of the driver. That will almost certainly be too close to allow good cooling. I couldn’t see any guidance on B&C’s website, but JBL recommend 76mm minimum for effective cooling of their 2206 model, also a 12”.

So, if you take that into account and build your rear chamber to 32 x 32 x 21, you’re up to 21.5l gross or 18.2l net, for each driver.

Tapering the sides of the box like the SMT will help a little (and Stipe didn't use quite as much depth as 21cm, but still more than 14cm) but the rear chamber volume in that is still 29l (before subtracting the drivers and brace) or about 22l net.


Quote I need to understand if its the right way to simulate a x2 12" enclosure!
and if its possible to add the air reduction of the horn in the caulculation

Fundamentally, once you get the realistic values in place, yes, you would model a dual driver horn this way.
For the volume of the horn, you would ideally work out how much cross sectional area it has as you progress down its length and subtract that from the areas in your model. You'd be best to do a multi segment model to help make it more realistic.
For example, if the back of the CD is 20cm in front of the 12" drivers, then S2 would be whatever area your main horn has at that point and L12 would be 20. IF the CD+Horn has a smooth expansion then you might get away with just doing one further segment, with the final area being your 4000 minus whatever the area of the mouth of the 2" horn is. You may need to pick a different expansion type to match whatever the actual change in area is in this segment.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 21 October 2017 at 3:05pm



4pi simulation. Asymetry is from uneaven outside enclosure.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 21 October 2017 at 3:48pm
Wider dispersion


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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 21 October 2017 at 6:27pm

Sometimes all the efforts are just waste of time. Gained 100-200hz for uneaven char. Should get back to beginning.
Here is the reason of asymetry.

And comparison to straight mt's:



Edited by gen0me - 21 October 2017 at 7:17pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 22 October 2017 at 8:43am
Forgot that the sims are for 12PR310 but 12mh32 would look almost identical.
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