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reduce the back volume of a mid horn

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Angelow View Drop Down
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    Posted: 24 August 2018 at 2:47pm
I would like to reduce the back volume of an old medium to horn to make the trapezoidal case (smaller to carry).
How much should be the minimum volumw for the 12 "cone?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 25 August 2018 at 3:55pm
Do the 12's have an attached back chamber or are they sealed back drivers? If either of those you could shrink wrap the case around the drivers or even just eliminate the case altogether and just mount the horns on a baffle.
If the driver is a convention open back and has no top hat on it then you can still reduce the enclosure size as much as you want, I bet these are crossed pretty high above 15 mid/bass or similar so low frequency response is of no concern.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Angelow Quote  Post ReplyReply Direct Link To This Post Posted: 26 August 2018 at 2:05am

to tell the truth I do not know how much they should be cut! they have no technical documentation! only a 3-way analogue crossover. They were mounted on a single 18 w-bin! everything is just a closed box, the volume reaches the sides of the horn, but the part with the tweeter is separate.


Edited by Angelow - 26 August 2018 at 2:05am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 26 August 2018 at 3:16am
Pull out one of the mid/horn assemblies and post a picture of it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Angelow Quote  Post ReplyReply Direct Link To This Post Posted: 26 August 2018 at 10:59am
Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 26 August 2018 at 5:52pm
Nice pics... but you forgot the most important part.. the driver.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Angelow Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2018 at 2:26am
the driver is old rcf l12p11 wl, but they have the coil burnt, I think I will use the model rcf mb12n351 that I already have at home, or the eigheensound 12nd610.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2018 at 12:45pm
You should stick with the default membrane shape. Also 12n351 has high mms. So efficiency will drop.
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Angelow View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Angelow Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2018 at 12:56pm
so do you advise me to stay low as mms?
I have 12pr300 of faital and 12hpl64 but they are low power, but could be more efficient?

or I buy the 12nd610 which are pure mid bass?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2018 at 2:29pm
I couldn't find the L12P11 WL but could find the L12P11 W (Fs: 55 Hz, Qes 0.18, Vas 75 L)

Apart from having a similar cone shape, I would look at a driver that firstly has similar Fs, Qes and Vas and secondly similar Le and Mms, thirdly a voice coil between 3" - 4".

I wouldn't rule the MB12N351 out for having a high Mms, especially since the Fs, Qes and Vas are a clear fit. Le and Mms are a bit higher, so you're probably trading extra power handling,for extended frequency response up high.

If I would have both drivers laying around I would first try the 12ND610 as it looks closest to the original overall. But considering you already have the MB12N351 and it would be my second choice on the list of all the drivers mentioned, I would try them first.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Angelow Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2018 at 2:40pm
in fact I did not find any news with that acronym, but it is a woofer produced in 1985

perhaps you should completely redesign the room with a new cone ..


Edited by Angelow - 27 August 2018 at 2:51pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2018 at 4:05pm

Ok this is not the best example because it is mt112 so your flare higher frequency response will be better. I havent used here any sort of damping either that could affect a bit low freq response but not many build straight horns for low frequency resp... if you compare those sims maybe you find something usefull. I will just add that changing shapes of membrane the shape of response changes especially valleys and mountains so if the flare was optimized for a special shape of membrane your ear perception with change will be worse. And as ts parameters you can eq to get needed  overall shape, you cant eq small peaks and depths.
I suggest img editing software with occlusion.


Edited by gen0me - 27 August 2018 at 4:19pm
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