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Bass horn project
Bass horn project
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Old 29th October 2013, 10:55 PM   #1
Paul Scearce is offline Paul Scearce  United States
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Default Bass horn project

I've started a new bass horn project. The horn should have roughly the same flare and mouth area as a Klipsch horn. It is intended to be placed in the corner.

I got the curves a little off in this first attempt. I'm pretty sure I now how to correct that for the next try. When the shape is right, I will reenforce it with paper mache, about 3/4" thick and add a sealed chamber for the woofer.

If there is any interest, I will post updates as the project progresses.
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Last edited by Paul Scearce; 29th October 2013 at 11:01 PM. Reason: picture added
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Old 30th October 2013, 01:12 AM   #2
hottattoo is offline hottattoo  United States
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Paul:

WOW ! that is very nicely done. What material did you use ? What frequencies do you want to cover ? What driver do you think you will use ? Your skills are far better than mine. Good luck.

Joe
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Old 30th October 2013, 01:24 AM   #3
POOH is offline POOH  United States
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So the thin wall paper actually directs those long bass waves?
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Old 30th October 2013, 02:01 AM   #4
Paul Scearce is offline Paul Scearce  United States
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hottattoo:

Thank you. The material shown is .1" chipboard. It is basically the same material used in cereal boxes, only thicker. The panels are glued together using hot glue. The form just has to hold its shape while the paper-mache composition dries.

I'm hoping it will sound good up to ~ 500-1000hz range. That is a bit higher than the typical folded corner horn, but I am hoping that the simple path along with efficient woofers will help. The woofers are also home made. They are 15" drivers with very light straight sided cones and electromagnet motors.

POOH:

The thin paper walls will be reinforced to about 3/4" thick. The paper-mache composition I will be using should be as strong as MDF, so the walls should be as effective as most folded horns. Weather or not that is really enough, I will know when they are done.
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Old 30th October 2013, 02:22 AM   #5
halo71 is offline halo71  United States
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Woofer are home made? This project should be very interesting indeed!
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Old 30th October 2013, 02:47 AM   #6
freddi is offline freddi  United States
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Bass horn project
Cool - - folks probably would like to hear about your woofer's motor and how it was made
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Old 30th October 2013, 03:26 AM   #7
POOH is offline POOH  United States
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I like the shape, it looks like it will get pretty high.
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Old 30th October 2013, 07:50 PM   #8
Paul Scearce is offline Paul Scearce  United States
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A few years ago, when you could get old Rola 12" field coil speakers for $20, I got several. I made a pair of 15" woofers by adding plywood extensions to the baskets and replacing the cones with homemade cones made from poster board. I left the spiders and voice coils from the original speakers in place. The cones and voice coils weigh about 35g each.

I am currently running these woofers in 10cu ft enclosures tuned to 40hz with a 145hz tractrix front horn.
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Old 2nd November 2013, 08:25 PM   #9
Paul Scearce is offline Paul Scearce  United States
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Default Cutting curves

Here is a picture of some of the curved panels for the next copy of this horn. I estimated these panels as a series of wedges. For the first iteration I just cut along the straight segments that made up the edges of the panels. For this attempt, I got a set of french curves to use as cutting guides.
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Old 7th February 2014, 03:52 PM   #10
Paul Scearce is offline Paul Scearce  United States
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This project is moving forward at a glacial pace. I wasn't much happier with the mouth shape of the second horn, so I decided to redraw the curves. I also found that I was mistaken about the Klipsch horn flare rate. It turns out they expand at a 47Hz rate, and I had guessed they were around 35Hz. I used this new information when I calculated the new curves. Now, the mouth is closer to 1/8th size for the flare, and the delay from the woofer will be about 2ms smaller.

I was pretty pleased with the new shape, so the next challenge was re-enforcing it. I've tried out a few different recipes, and I think I will use a combination of paper pulp and portland cement. I used this on the horns of the horn-reflex enclosures, and I think it worked pretty well. I will need something better than the paper dust masks i used with them though, as the dust is pretty irritating.

My original thought was to cover the entire horn with the paper composition. I've decided this will not be strong enough at the mouth, so I am working on cutting pieces for that from plywood.

In the meantime, one of the woofers I intended to use began to rub. I think I will take this as an opportunity to rebuild them completely. They lasted a few years, but I think I could do better. For one thing, the original voice-coils had a very small x-max. I think I can increase the x-max without losing too much motor strength.

I'll have updates on the horn, and on the woofer rebuild as they become available.
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