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Old 23rd November 2012, 08:18 PM   #1
jan1 is offline jan1  Netherlands
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Default 8x12" horn sub

Hello,

I would like to explore the idea of a 8x12"horn sub (see attached sketch).
I don't know enough about horn theory, can someone help me where to start / proceed. Target is to make a super powerful horn and to go as low as possible in a group of 4 or more.

Some parameters I have:
* cabinet size 60x48x28 inch
* possible horn lenght 137 inch according the fold in the sketch.
* 1/4 wavelength of 25 Hz is 135,6 inch
* 8 cabinets in a row make for a circumfence of 544 inch (whole 25Hz wavelength is 542,4 inch)


What would be suitable drivers?
How to determine the flare of the horn?
Wil the drivers withstand the pressure at the beginning of the horn?
How to determine the size of that beginning?
How to get on?

these??
FaitalPRO - Professional Loudspeakers Made in Italy
or:
B&C SPEAKERS

thanks
best regards
Jan
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Old 23rd November 2012, 08:24 PM   #2
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You might wish to consider tapped horns. Most bang for the buck as you are using both sides of the woofer so you can almost cut the number of drivers in half. What are you using these for?
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Old 23rd November 2012, 08:38 PM   #3
jan1 is offline jan1  Netherlands
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Hello Cal, I would like to proceed with a horn loaded sub.
I hope someone around here can give me some direction how to proceed.
Jan
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Old 23rd November 2012, 09:10 PM   #4
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I would think you would want to search around the web for plans. The plans usually include what driver the cabinet is designed for.

The drawback I see in your design is that you will have to leave two panels removable to mount and access the drivers. Not terrible but a little tight to get your hands/tools in there to do the fastening.
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Old 23rd November 2012, 09:15 PM   #5
xjr100 is offline xjr100  Europe
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Quote:
Originally Posted by jan1 View Post
Add to you list Volt drivers:
Volt Loudspeakers - Studio Range
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Old 24th November 2012, 12:14 AM   #6
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Originally Posted by Cal Weldon View Post
You might wish to consider tapped horns. Most bang for the buck as you are using both sides of the woofer so you can almost cut the number of drivers in half. What are you using these for?
This is not how tapped horns work. The mouth side tap contributes very little, it's only used to fill in normal tl nulls - it doesn't help at all in the lower bass. In fact, if the driver is mounted right at the beginning of the line (which is tough to do physically in the tapped horn but can be simulated easily) the results are exactly the same whether the driver is mounted on the outside (tl) or inside (tapped horn). Switch between Nd and TH in Hornresp and there's no difference at all.

Also, tapped horns are no more sensitive or loud (max spl) than front loaded horns. In fact, I can systematically beat tapped horns with front loaded horns of the same size (in simulation at least) using the same driver, tuning and low end rolloff. Every time. The front loaded horn might need to be unconventionally shaped for best response in order to compare with small tapped horns but I can always get the front loaded horn to beat the tapped horn.

Last edited by just a guy; 24th November 2012 at 12:26 AM.
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Old 24th November 2012, 12:24 AM   #7
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Quote:
Originally Posted by jan1 View Post
Hello,

I would like to explore the idea of a 8x12"horn sub (see attached sketch).
I don't know enough about horn theory, can someone help me where to start / proceed. Target is to make a super powerful horn and to go as low as possible in a group of 4 or more.

Some parameters I have:
* cabinet size 60x48x28 inch
* possible horn lenght 137 inch according the fold in the sketch.
* 1/4 wavelength of 25 Hz is 135,6 inch
* 8 cabinets in a row make for a circumfence of 544 inch (whole 25Hz wavelength is 542,4 inch)


What would be suitable drivers?
How to determine the flare of the horn?
Wil the drivers withstand the pressure at the beginning of the horn?
How to determine the size of that beginning?
How to get on?

these??
FaitalPRO - Professional Loudspeakers Made in Italy
or:
B&C SPEAKERS

thanks
best regards
Jan
This is probably not a good project for your first diy horn. At this size there's a lot of things that even experienced horn designers don't usually have to consider. For example, if your mouth gets too big it's going to narrow your dispersion, so you have to be aware of that.

Having said that, since this is meant to be a full system with several modular boxes, personally I would design it as a single stack, like Danley did with the Labhorn, and then divide it up physically into several boxes instead of designing a small horn and just building a bunch of them.

It's absolutely essential to use Hornresp (or similar) software to help you design. There are no rules of thumb that will get you an acceptable horn. If you can't or don't want to learn proper horn design it's probably best to just build a stack of Labhorns, but I would recommend some modifications to the plans.
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Old 24th November 2012, 05:43 AM   #8
epa is offline epa  Netherlands
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so you want 8 cabs of 1300 ltrs each loaded with 4 12"drivers?
so 32 x12"in total.
ambichious project.
like just a guy says, you need to simulate a proper horn.
i can asist with a sim or model.
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Old 24th November 2012, 06:54 AM   #9
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Originally Posted by epa View Post
i can asist with a sim or model.
That's the easy part, just load your drivers into hornresp. For Nd, select the total amount of drivers to be used (32 in this case although that seems like a lot more than necessary). Set the Ang to the proper boundary loading and then select "system design - with driver". Select a desired bandwidth (but remember that hornresp has a mouth size limit so you might have to play around with that - you may need to select a higher tuning or more boundary reinforcement to get the simulation to run). Make sure the the throat is a reasonable size (so it won't destroy the drivers or cause tornado turbulence in the throat), the previously selected bandwidth may need to be reconsidered if it generates an undersized throat.

That will give you a proper full size classical horn. You can tweak it further from this point by simply exporting the flare dimensions as a txt document and reentering it with parabolic segments. When it's all tweaked out, simply divide the cross sectional area dimensions by the desired amount of cabs and you have the details of the individual boxes.

Before you get too far you need to consider dispersion. If the mouth gets too big dispersion will become increasingly narrow. Also, the further away from round the mouth gets, the faster dispersion will narrow. The mouth needs to be large enough to support the tuning frequency but small enough to allow the higher frequencies to be distributed properly.

Then it needs to be folded, which is a huge topic by itself. I don't even want to get into folding right now. This is the hard part, although it gets exponentially easier if you plan ahead.


I'm sure epa knows all about all of this, I'm just posting to let the OP know what is involved here. (And note this is only one way to proceed.)

Last edited by just a guy; 24th November 2012 at 06:58 AM.
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Old 24th November 2012, 07:15 AM   #10
jan1 is offline jan1  Netherlands
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Hello epa and just a guy thanks for you're input

Designing it as a single stack is what meant, indeed exactly like danley did with the Labhorn. but it takes 8 cabs in row to get the circumfence of the mouth opening to be approx 540 inch (25hz wavelength)
I would prefer max performance in a 4 block but that would give a much to small circumfence of the hornmouth 320inch??

epa if you would like to assist me with a sim / model that would be great!
for now i dont know how to proceed? do i need to choose a driver first? or model the horn first? I downloaded hornresp it asks for both?

I don't know what driver parameters make for a good horndriver especially in this horn since the beginning seems to become pretty small so high pressure.

As for the horn the size of the mouth opening is known, but how to start the horn is a mistery to me? Can it start like in my scetch or does it need a chamber first like the labhorn?

thanks
Jan
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