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best choice for a 12" horn plans

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_Natty_ View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:12pm
Originally posted by gen0me gen0me wrote:

Forgot that the sims are for 12PR310 but 12mh32 would look almost identical.

Hi gen0me, thank alot for the contribution but things like that are hard for me:
  • -this kind of project is too complicated for me, i can't arrange a project like that is too expensive in term of times and things to do in the carpenter workshop...def. i need something more simple to build
  • -second o i google a lot for finding a demo or a free version of this program but i didnt find anything! so i cant check my result over this.
anyway thanks alot for the contrib

DMmorrison,
dont get me wrong, i take your comments and i try to work over it.

 I splitted the horn problem in 2 part:

  1. find the best back chamber/tuning (sealed or reflex)
  2. move to the horn part

My speakers seem good for reflex loading but starting from sealed seem more easy, and if I keep the low volume it seems that some upper freq can have some benefits.

  • my driver is 3,3L of volume
  •  mt130 have VRC= 14,81 LRC=13,6
  • mt121(both TDA and classic version) have VRC= 17,6 LRC= 14,8
both are suitable for driver like pd121 
so pd121 VS b&c 12mh32 are:
  • fs=53hz ->>>>>>>>>>>>>>>> fs=53
  • vas =66,5L->>>>>>>>>>>>>> vas=63
  • cms = 168.33 µm/N ->>>>>>>>cms= - (value calculated from hornresp)
  • qts = 0.23->>>>>>>>>>>>>>>qts=0,19
  • deep of basket= 115mm->>>>>deep of the basket=133mm
so maybe i need more space on the back due the longest basket, but it seem that i've a lot of benefit in keeping low the value of the volume inside the box something around 11l give me the best benefit but it seem almost impossible to fit a 12" in a little box like that...
So i made some test in between 15 -30l and it seems that something around 20-22l give me good results.
(I try this in winIsd, bass box pro 6 and an online calculator).

is it a good way to proceed?

then i'll move to the horn section, but I need to understand a couple of thing:

  • what is considered ATC or VTC in horn like mt121 tda( http://hornplans.free.fr/mt121tda.html ) ? i cant see any front chamber! is it considerd that the air from the cone surface to the S1?
  • having a tiny duct of some cm in front of the troath  seems to helps a lot the power of the horn or I wrong? -something like the 13cm duct in front of mt130 ( https://www.freespeakerplans.com/plans/15-plans/midtopcab/35-mt-130 )
  • I read that coupling driver can have some benefits but even some big problem on the high freq due phase cancellation; if ill cut from 150hz to 1000hz can phase cancellation for 12" can be considerated as problem? thats for understand if making one big horn for 2 driver is a good choiche... for the back chamber is easy to split in 2 the back chamber or put some braces to avoid reflections...
What Ive decide for now are the dimension:
the box should be 1000mm  X 600mmx 670mm (HxWxD)

So the total mouth will be something like: 552900 mm^2

thanks a lot to all contibutors again!




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gen0me View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:36pm
Originally posted by _Natty_ _Natty_ wrote:

  • what is considered ATC or VTC in horn like mt121 tda( http://hornplans.free.fr/mt121tda.html ) ? i cant see any front chamber! is it considerd that the air from the cone surface to the S1?
  • having a tiny duct of some cm in front of the troath  seems to helps a lot the power of the horn or I wrong? -something like the 13cm duct in front of mt130 ( https://www.freespeakerplans.com/plans/15-plans/midtopcab/35-mt-130 )
  • I read that coupling driver can have some benefits but even some big problem on the high freq due phase cancellation; if ill cut from 150hz to 1000hz can phase cancellation for 12" can be considerated as problem? thats for understand if making one big horn for 2 driver is a good choiche... for the back chamber is easy to split in 2 the back chamber or put some braces to avoid reflections...



Two drivers one above another:
If they are in one enclosure there are no cancelations but effect you can see on the graphs. The vertical dispersion is narrowing with frequency. Look at the patterns. With one speaker per box dispersion wouldnt narrow that fast.
The duct shape is for dispersion. Kind of same reason as above but with one speaker. I guess it could contron disperion a bit better.
S1 would be on last plans 184x74 (x2 its half of hole) that for one speaker.
Vtc volume between cone and S1.
Atc in this case is just a rough shoot.
All the plans are too complicated?
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_Natty_ View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:38pm

this is the sims of mt121 with a back chamber of 22L and some Fr and Tal that give me a smoother and flatten response:

are there too optimistic? to me seems a good result or I wrong? real world tells different?





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gen0me View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:40pm
Change angle to 4pi.
Atc technically should be smaller than Sd.
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_Natty_ View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:46pm
Originally posted by gen0me gen0me wrote:

Originally posted by _Natty_ _Natty_ wrote:

  • what is considered ATC or VTC in horn like mt121 tda( http://hornplans.free.fr/mt121tda.html ) ? i cant see any front chamber! is it considerd that the air from the cone surface to the S1?
  • having a tiny duct of some cm in front of the troath  seems to helps a lot the power of the horn or I wrong? -something like the 13cm duct in front of mt130 ( https://www.freespeakerplans.com/plans/15-plans/midtopcab/35-mt-130 )
  • I read that coupling driver can have some benefits but even some big problem on the high freq due phase cancellation; if ill cut from 150hz to 1000hz can phase cancellation for 12" can be considerated as problem? thats for understand if making one big horn for 2 driver is a good choiche... for the back chamber is easy to split in 2 the back chamber or put some braces to avoid reflections...



Two drivers one above another:
If they are in one enclosure there are no cancelations but effect you can see on the graphs. The vertical dispersion is narrowing with frequency. Look at the patterns. With one speaker per box dispersion wouldnt narrow that fast.
The duct shape is for dispersion. Kind of same reason as above but with one speaker. I guess it could contron disperion a bit better.
S1 would be on last plans 184x74 (x2 its half of hole) that for one speaker.
Vtc volume between cone and S1.
Atc in this case is just a rough shoot.
All the plans are too complicated?

thanks again
 you show me horns with almost 2 segments even more...
having 2 different segments means a lots of different angles.
For me is a lot of work around cnc cutter, and due a friend that will help me to cuts all, -in the free time of cnc- i need to be faster as i can for cutting! So simple is the way... to me easyest way is to go sealed or reflex, but I play almost the last 10 years with this configuration, and I'd like to improve a little bit my knowledge in speaker building!
I will read more carefully your suggestion about phase canc and i will check even the projects... im not so good in understanding dispersion right now...
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_Natty_ View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:50pm
Originally posted by gen0me gen0me wrote:

Change angle to 4pi.
Atc technically should be smaller than Sd.

yesssssss
sims in 4pi give me back silly results!

directivity give me back an higher response but still not good and flat like before in 1pi.

The data for 121 tda version data was taken from the "database simulation post" from this forum... so are wrong?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 2:57pm
If you do multiple speakers:2 it would look like simulating in 2pi so a bit better for 2 speakers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 3:25pm
So correct me if im wrong:
so almost every horn have a VTC and ATC part that by default is the air from the cone surface to the S1.  and my speaker will have is own right?

needs to work on it... for better understand how to set.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 5:25pm
Yes.
Dont worry. Usually those arent very important values.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 5:45pm
Its change a lot from result with or without this part...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 8:51pm
Nvm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 9:10pm
Originally posted by _Natty_ _Natty_ wrote:

So correct me if im wrong:
so almost every horn have a VTC and ATC part that by default is the air from the cone surface to the S1.  and my speaker will have is own right?

needs to work on it... for better understand how to set.


For the mt121 I presumed as its rear mounted the atc would be the same as sd and vtc is calculated by using the wizard (double clicking in vtc). correct me if I'm wrong.
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