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BC horns from standard FLHs
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BP1Fanatic View Drop Down
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Points: 107 		Post Options Post Options   Thanks (0) Thanks(0)   Quote BP1Fanatic Quote  Post ReplyReply Direct Link To This Post Posted: 29 January 2025 at 8:00pm
Great thread fellas!
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snowflake View Drop Down
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Points: 3443 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2025 at 3:47am
Originally posted by Keen Keen wrote:

I'm not referring to the baffle arrangement per se, just that horn resp should be capable of recognising expansion rates and providing an appropriate power response. I mean that's what the program does. 

 



it might get the power right but doesn't calculate the directivity. using 1pi rather than 2pi might get close but won't be quite right. the amount of time I have spent thinking about how this works might just cannibalise some speakers - replace the grill with some 18mm ply and cut a hole in the side and take some measurements. LOL
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Points: 13 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Hallowell Hi Fi Quote  Post ReplyReply Direct Link To This Post Posted: 31 January 2025 at 6:44pm
Yea snowflake I used to think simming in 1pi would be more accurate but there's a few different things at play. The theory as I understand it is you can get both boundary gains and better impedance matching gains for more than just a 6dB boost going from half-space to quarter-space.

The larger the stack face/baffle the closer you get to a flush mounted speaker in 1pi and the lower the frequency that gets a boost up to 6dB. Then depending on how well you're able to actually couple the internal horn to the baffle, you'll see additional sensitivity gains (not sure what the theoretical maximum is here.) This is the real art of the design where apparently even Akabak doesn't quite get it right.

With that in mind, this design still has benefits over conventional FLH arrangements even if no additional coupling to the baffle is achieved. You can achieve deeper extension with less wood in the same size cab if you're willing to put up with a slight increase in group delay, and you can balance that by playing with the size of the new mouth (smaller = more extension and more group delay).
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Points: 1271 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 01 February 2025 at 3:19am
Can’t see the point of 1pi, it’s assuming an infinite boundary which even the big 4packs don’t even come close. The low end of the wavelengths being are 13-14m long. 2pi seems the most realistic to me. Also, as a punter, directivity is lower down the priority list (perhaps I don’t understand it). Fast punchy subs that operate within their design limits and are built logically regarding transport, driver access, folding etc are all more important than directivity as a punter. 

Love your work Stu, but I do think the current box is a bit half baked. 
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Points: 3443 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 02 February 2025 at 11:13am
Originally posted by Keen Keen wrote:

Can’t see the point of 1pi, it’s assuming an infinite boundary which even the big 4packs don’t even come close. The low end of the wavelengths being are 13-14m long. 2pi seems the most realistic to me. Also, as a punter, directivity is lower down the priority list (perhaps I don’t understand it). Fast punchy subs that operate within their design limits and are built logically regarding transport, driver access, folding etc are all more important than directivity as a punter. 

Love your work Stu, but I do think the current box is a bit half baked. 


directivity reduces bass going onto the stage, indoors it stops reflections off the rear wall, outside it reduces noise pollution, and it reduces the number of boxes and amps required.
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Points: 1271 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2025 at 1:29am
cheers, so in bigger setups there appears to be significant advantages to sub directivity 
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Points: 207 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Racks&Stacks Quote  Post ReplyReply Direct Link To This Post Posted: 13 February 2025 at 4:03pm
directivity has advantages in smaller sytems, too, otherwise cardioid setups would not be a thing. punters may not care about noise pollution, but neighbors do, and there isnt a party if the neighbors are too adversely affected
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Points: 1271 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2025 at 2:35am
True, but cardioid and end fire are different approaches to controlling directivity obviously using multiples of much smaller boxes. The point was this box layout has the potential to offer advantages separate from directivity if so desired. 
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Hallowell Hi Fi View Drop Down
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Points: 13 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Hallowell Hi Fi Quote  Post ReplyReply Direct Link To This Post Posted: 16 October 2025 at 1:03am
Just wanted to report back that I'll probably keep future updates going over in the https://www.diyaudio.com/community/threads/bc-horn-inspired-hbh15.423181/#post-7937782 - diyaudio thread here

The All_1 BC118 thread is also well worth looking through!


Edited by Hallowell Hi Fi - 16 October 2025 at 1:04am
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steve winner View Drop Down
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this build is nice
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Points: 1271 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2025 at 12:54pm
Can’t stand designs with wasted space/cavity’s. Drives me nuts. Not to mention that chipboard. Criminal 
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Points: 1271 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2025 at 1:24pm
final boss lurker cred though Steve - joined 2006, first post 2025. Impeccable! Clap
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