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Kick Bin Design Idea B&C 15ndl76

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luthier View Drop Down
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    Posted: 04 January 2019 at 10:40pm
Hi all,

I'm in the very early stages of designing a kick bin section for a 3way mid to based around the B&C 15ndl76. I'm aiming to use it for between 100-300hz. I'm hoping for an average sensitivity of 102db -3db in the pass band. It will be going below a sonitus mr8xt and Beyma cd10fe (one cabinet).

I know it's a gargantuan task but, I've seen it done on this forum a few times before (Davey's Mid Top for example) . If anyone has any pointers I'd be very happy to hear them, I'm not easily offended. 

I'm very comfortable with the woodworking aspects and expecting to be making a fair few prototypes, as well as spend a good deal of time on Solidworks. 

Here's some of the hornresp sims so far in 4pi:

Any advice would be greatly appreciated! 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 04 January 2019 at 10:48pm
Here's 2pi


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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 04 January 2019 at 11:09pm
Plots don't look unreasonable but do you have any sketches of how that will fit in a cabinet with the mid and high sections?  Are we talking a straight horn or folded?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 04 January 2019 at 11:22pm
Haven't started drawing the cab in solidworks yet. Wanted to wait to see if anyone could spot any obvious mistakes at this stage. 

Folded horn, but only two folds. Straight horn like the coffin bin would be impractical. 

Ideally the cabinet would be trapezoidal. Height around the 1200 mark, width  552 narrowing to 344 for a 28 degree splay angle with 445mm depth.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 04 January 2019 at 11:53pm
Just some very (VERY) rough sketches of what I'm thinking. I'm sure it's no surprise to anyone.

Hopefully it won't be too honky. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 04 January 2019 at 11:56pm
Here's the hornresp schematic.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mikkel Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2019 at 12:24am
Hi luthier. I think to model s1 correctly you got to take the whole baffle into account not just the driver aperture. So to accomodate a 15" driver i would think it would need to be atleast 40x40cm, so probably closer to 1600cm2?

Also i dont know if it would reach 300hz with a fold, from what ive read bandbass horns like that dont like to play that high. A straight horn like hornresp the model would probably be better .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2019 at 1:04am
The Es18bph only has 801cm2 for the S1 and that's for an 18. My design has 1144cm2. I'm not too worried about that. 

I''ve designed my own straight horn for this driver based on the coffin bin project posted by another member. However, with no folds it ended up being over 800mm in length.

There are a fair few BPH in production that play 300hz and above. I'm hoping to be able to the same.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2019 at 10:26am
There has been a lot of discussion in the distant past about whether the length of the throat chamber (between the baffle and the fold in this case) counts as part of the length of the horn, or whether the horn flare itself starts at the narrowest section.  I see you've chosen to model the throat chamber as the first horn section which is not something I've ever tried.  Could be valid.

Something I have found useful in the past when testing designs like this is to compare the impedance plots between the simulation and the real cabinet.  Best way to analyse how close to the theory you've got.

I'm quite interested to follow this because firstly I'm quite familiar with those midrange horns but also I've tried a few similar low frequency designs in the past and not come up with anything worthy of building into a complete cabinet.  You are definitely right to expect a few rounds of prototyping!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mikkel Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2019 at 8:06am
Originally posted by luthier luthier wrote:

The Es18bph only has 801cm2 for the S1 and that's for an 18. My design has 1144cm2. I'm not too worried about that. 

I''ve designed my own straight horn for this driver based on the coffin bin project posted by another member. However, with no folds it ended up being over 800mm in length.

There are a fair few BPH in production that play 300hz and above. I'm hoping to be able to the same.






Yea your right in saying the es18 is modeled with s1 of 800cm2 but thats because s1 in that simulation is taken from where the front chamber ends (s2 in your simulation). It might be worth trying to sim using the fromt chber value in hornresp and removing the first section of the horn to compare sims.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote corell Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2019 at 9:11am
Originally posted by ceharden ceharden wrote:

There has been a lot of discussion in the distant past about whether the length of the throat chamber (between the baffle and the fold in this case) counts as part of the length of the horn, or whether the horn flare itself starts at the narrowest section.  I see you've chosen to model the throat chamber as the first horn section which is not something I've ever tried.  Could be valid.

Simulating the throat chamber as a negative expansion horn segment or a throat chamber (with correct vtc/atc = length of throat chamber!) yields nearly identical results in honresp. i have been curious myself sometime ago and compared a few designes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mikkel Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 9:43pm
Originally posted by corell corell wrote:

Originally posted by ceharden ceharden wrote:

There has been a lot of discussion in the distant past about whether the length of the throat chamber (between the baffle and the fold in this case) counts as part of the length of the horn, or whether the horn flare itself starts at the narrowest section.  I see you've chosen to model the throat chamber as the first horn section which is not something I've ever tried.  Could be valid.

Simulating the throat chamber as a negative expansion horn segment or a throat chamber (with correct vtc/atc = length of throat chamber!) yields nearly identical results in honresp. i have been curious myself sometime ago and compared a few designes.



There you go! Ive wondered myself a few times, good to know the two meathods agree.
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