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Old 22nd September 2005, 01:22 AM   #1
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Default Rear Loaded Smooth Bass?

Hello all, I believe this is my first post here.

I am experimenting with rear loaded horn building using a JBL E140 15" speaker. for a two way design. The E140 is a powerful magnet, low qts design with about a 35hz resonant frequency. I am wondering how I can manage the cancelations / reinforcements of a rear loaded horn design when the waves from the horn meet the waves from the cone and get a smoother response. My first try was nice and punchy with some peaky midbass. My second design is longer, about 4 meters or 10'-12'. This one is more extended in the lows, but seem to be missing something in the midbass area and some efficiency. Can I remedy this by making adjustments to the throat and compression chamber?
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Old 22nd September 2005, 04:47 AM   #2
GM is offline GM  United States
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Greets!

Yes.

GM
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Old 23rd September 2005, 12:30 AM   #3
Mark Kravchenko --- www.kravchenko-audio.com
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Default Yes ^2

GM speaks the truth.

A tip is that if you are not to far off the ideal rear chamber you can use stuffing to change the air resistance. It looks like a larger enclosure to the driver.

Mark
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Old 27th September 2005, 03:32 PM   #4
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Default rear chamber

In my previouse design (much shorter path length) I had a some success extending the throat and making the rear chamber really small. Is there a rule of thumb regarding rear chambers? Bear in mind that I got average grades in math and never took calculus. Attached is a sketch of my design. Although it appears the first section gets smaller as it goes away from the driver, in actuality, there is a diaginal baffle in the other plane, making the the "throat" area 5"x13" and the end of the first section 24"x3". The bent section is made form 1/4" masonite. glued and braced.

Thanks,

Mark
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Old 28th September 2005, 12:44 PM   #5
Mark Kravchenko --- www.kravchenko-audio.com
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Default Check this out and your math worries are lessened

http://www.users.bigpond.com/dmcbean/

Read the manual acouple of times. It takes that many to let it all sink in. Then you can fool around with the program and change the horn design at will and come up with something that is a better compromise.

If you have this program great. If you don't it will be a big help as you can see what happens without making sawdust.

If your drawing is to scale there is a constriction just before the mouth that will cause pretty bad reflections back into the horn. THat maybe a source of your problem.

Mark
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Old 28th September 2005, 04:18 PM   #6
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Default thanks for the tips

I tried stuffing, and it seems to have improved things. (1 fleece pullover, and 2 t shirts) I put them in the corners of the chamber behind the speaker, except for the 4th corner, which does not exist, because this is where the sound goes out into the horn.

I'll try the software when I get a chance.

Thanks
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Old 29th September 2005, 03:07 PM   #7
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Mark,

What part of NJ? I'm at GSP Exit 105.

I personally prefer TL systems.

Larry
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Old 29th September 2005, 03:28 PM   #8
Mark Kravchenko --- www.kravchenko-audio.com
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Default Get stuffed

Your stuffing choice may not be the best.

Try some dacron fibre fill. It's used for pillows and blankets. Face it man you have to go to wall mart and visit the crafts section. It's a dirty job but it's for a good cause.

Mark
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