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Kick Bin Design Idea B&C 15ndl76

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luthier View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2019 at 11:01pm
some more sims




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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2019 at 11:17pm
Had a go at porting the horn again with fairly nice results, gained some low end with only a little lost sensitivity and much better xmax control.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 20 January 2019 at 12:06am
Excuse the F1 style front panel, it wasn't intentional, but it makes it really easy to get the 15" in and out! 

This is the cabinet matching the last and most recent plot, I've got the excursion under control down to 101hz and the 15 just about makes it to 370hz. So not absolutely perfect for meeting the sonitus mr8xt but acceptable. 






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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 2:49pm
So I played around with porting a bit more but couldn't get rid of the dip at 250hz. I've decided to move the STH100 up 15mm, this is to allow me to increase the size of the small  fibreglass chamber in front of the driver. The sweet spot seems to be between 12l and 15l. 

In the current format I can always go ported later in real life testing and make various chambers to play with tuning. 

I will also experiment with some different drivers at some point in Hornresp. 




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Post Options Post Options   Thanks (0) Thanks(0)   Quote JulianDA Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 4:02pm
Dont you think the sudden jump in area at the bend of your horn will cause unwanted resonances? maybe you should try to implement this in your simulation before building a prototype :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 4:28pm
Originally posted by JulianDA JulianDA wrote:

Dont you think the sudden jump in area at the bend of your horn will cause unwanted resonances? maybe you should try to implement this in your simulation before building a prototype :)

I have simulated the full horn in Hornresp as it is drawn in CAD and haven't been able to notice and resonances at this time. If you have any suggestions on how I might go about simulating this differently or more accurately? in hornresp or any other software I'd be interested to know!?

My hope is that mouth area is large enough and cabinet construction rigid enough that resonances do not occur in the passband. I would fully expect to see them higher up but I only plan on using this section of the cabinet between 120 - 400hz. 

In an ideal world I would be able to get the horn with -3db to 80hz, at the movement I can get down to 100hz -3db but I run out of xmax at 105hz so plan on passing at 120hz to be safe. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 4:37pm
One question I have been racking my brain over recently is if this section of the vtc chamber is counted as the LRC or the S1 path length? At the moment (shown in grey) it is modelled as the lrc. The red line shows if I where to sim it as the s1.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 10:25pm
You're actually starting to look like a design that mykey did back in the day, just minus the phase lug.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 10:27pm
I'll take that as a compliment! Always loved Mykey's work. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 10:59pm
Here are some simulations with different drivers:

Most simmed like the Faital pro hp1020 but the ndl88 and Oberton 15b450 looked slightly better than the ndl76. I'm trying to stick to neodymium drivers to keep the size and weight of the enclosure down. The tops will probably weigh 40-50kg plus so any weight saving is a plus. 

So far I have simmed: FP 15fh520, FP 15fhp1020, Beyma 15lw30, B&C NDL88, B&C NDL76, emi kappalite 3015lf, Oberton 15b450


B&C 15ndl76 - Grey 
Faital Pro hp1020 - black

B&C 15ndl76 - Grey 
B&C 15ndl88 - Black



B&C 15ndl76 - Grey 
Oberton 15b450 - Black



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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2019 at 11:12pm
Oberton 12b450- grey
Pd.153er - Black
Pd.153er - Grey
Pd.1550 - black

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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 23 January 2019 at 12:39am
So after spending more time reading and experimenting on hornresp. I have come to a few conclusions on this design. 

As it is with my current horn path length my pass band is limited to 112hz - 400hz within +/-3db which is 12hz higher than my ideal high pass and 100hz higher than my orginal low pass.

With the Oberton 15b450 and pd.153er I can gain slightly higher lowpass at around 500hz although this is not nessecary for my design requirements. However, given the low price of the Oberton, £121.45 (bluearan) I will definetley keep it as a possible future option. The NDl88 also simmed well.

The cabinet in it's current layout seems to like drivers with a small Vas, Bl around 20, large xmax and relativley large VC.

To gain a better response below 105hz without going into the xmax I need to increase the horn length, which I'm reluctant to do as it does not seem to provide any significant improvement. For a few extra hz - around 10 - I reduce the low pass and lower overall sensitivity.

Porting gets me down to 85hz but the trade-off with sensitvity and lpf doesn't seem worth it. My average sensitivity is around 100.5db and the xmax is still too high. 

In terms of concerns, the off-axis response is around 3db higher between 200-400hz the the standard plot and the response is a bit peaky at max spl, looks a little like the golden arches!  

My cabinet dimensions are  H x 1036mm W x  537mm D x 472mm which is very close to my orignal size parameters, which I'm very happy about. 

I also set out to acheive 102db sensitivy +/-3db in the pass band which I have managed. 

Here's my proposed crossover points, simmed in hornresp.






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