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Bertha BH-882 Build

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Ricky2023 View Drop Down
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Joined: 01 December 2023
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ricky2023 Quote  Post ReplyReply Direct Link To This Post Topic: Bertha BH-882 Build
    Posted: 01 December 2023 at 3:41pm
Hey does anyone have plans for mini Bertha looking to use a 12” subwoofer using it for outside movie nights and maybe some party’s probably going to use a sundown audio EV4-12 or a SA 12” or does anyone have a better solution for a portable subwoofer enclosure preferably a mini w bin or mini folded horn that is portable cheers Ricky 

currently using a sundown audio EV3-12 in a 6th order parallel band pass for inside the house it does really well for movies and music it’s on roughly 750w 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 7:39pm
If huge SPL is not your main aim low tuned reflex would be my first choice. BMS18N862 is one option with its huge x-max.

Flat 25Hz Front loaded horns are going to be huge


Edited by csg - 08 January 2023 at 8:10pm
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zitikaz Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 5:50pm
Originally posted by csg csg wrote:

Regardless of the change of scale, what exactly are you trying to achieve using 21” drivers in a box of this style?


HI

I would like to reach 25hz with good response natural bass, 21lw1400 seems suitable driver. Plan is to use Levan ext aswell
Maximum spl isnt primary goal, trying to get 25-60hz flat response.


or better look Rcf 18x401 and forget upscaling to 21"?



 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 11:46am
Regardless of the change of scale, what exactly are you trying to achieve using 21” drivers in a box of this style?

The function of a horn is to provide a better match between the driver and the air it is trying to move. In essence a horn increases the effective size of the drivers you are using. This makes the coupling between the box and the outside world more efficient.

Bigger drivers in a horn does not automatically mean lower frequency response or more output, although this may be possible with good design. But merely scaling up or down an existing design to suit your purposes does not automatically work, there are far too many variables for that.
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BigSoundNorthWest Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 11:27am
Originally posted by Twintub Twintub wrote:

21"/18" = 1.1667
Multiply all dimensions by 1.1667Smile

Nope.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 10:39am
Originally posted by Twintub Twintub wrote:

21"/18" = 1.1667
Multiply all dimensions by 1.1667Smile

 Very bad idea. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jo bg Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 9:52am
Scaling everything will make a dfferent horn and lower the tuning. If you want to keep same tuning you have to keep same horn length and just find a way tofit bigger driver - check rear chamber too.
27 is already a low tuning, lowering it will probably lower efficency in exchange for not so useful 23hz output - unless you are going for cinema fx
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Twintub Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2023 at 12:14am
21"/18" = 1.1667
Multiply all dimensions by 1.1667Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zitikaz Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2023 at 11:29am
Can someone help me to scale up drawings so i can use 21" driver?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote APC321 Quote  Post ReplyReply Direct Link To This Post Posted: 29 December 2022 at 7:51pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 29 December 2022 at 11:43am
Bertha Hints - Make sure all internal Joints are Air tight.....I coated all Joints with Epoxy after building the Horn....A small Air leak will reduce Bass Output.....Make sure to get rear door very tight....The Klipsch Audio Papers has a Paper were Klipsch writes about Air Leaks....I found I like the Sound of two 1/2 Berthas better than one dual 18 Bertha......1/2 Berthas are also a lot less work moving.....VECTORSONICS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zitikaz Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2022 at 10:21am
Originally posted by Lee In Montreal Lee In Montreal wrote:

Originally posted by nomercy82 nomercy82 wrote:

Post pictures when you're done. I'm curious about your design. How does a 1 foot extension of horn length make up for a 3 foot hyperbolic extension?


Like that. With a 36" deep extension, it makes it "theorically" a 21Hz horn once the back chamber and throat size are tuned for a JBL 2242. Without the extension, it is a 27Hz horn for a 1/4 wave. Theorically. ;-)



How was the real results?
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