Re: My version! [message #16533 is a reply to message #16531] |
Mon, 24 May 2004 05:06 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Adrian Mack
Messages: 568 Registered: May 2009
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Illuminati (1st Degree) |
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Yeah, I'll change the throat. I couldnt decide if I should have a round throat 20cm diameter (for 400cm^2 area) or if I should make it a sort of rectangular or oval shaped throat. Cuz both drivers need to share the throat, I was thinking that a round throat would be the least best of the three, and a rectangular or oval throat the best to get as much surface from both woofer cones as possible in the throat - what do you think? > I personally like equiangular and nearly equiangular folding. I think its one of the most efficient/smallest/waste-free folding methods too, at least out of the various ones I've tried.
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How did Kirk defeat Khan? [message #16537 is a reply to message #16534] |
Mon, 24 May 2004 14:43 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Bill Fitzmaurice
Messages: 335 Registered: May 2009
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Grand Master |
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Because Khan used battle tactics that relied on two dimensional thinking, as in Chess. Kirk, a master at 3 level chess (though no match for Spock) thought in 3 dimensions. Khan never saw that last Photon Torpedo coming. The same applies to horns. All of your diagrams are two-dimensional, which infers that your thought process behind them is also two dimensional. When you lose that second driver you halve the required space for the rear chamber, space that can be added either to your pathway for a lower Fc or to the mouth area for a higher SPL or both, or just subtracted from the box for net size savings. Don't sweat standing waves in basshorns; they don't exist where surface to surface dimensions are 1/4 wavelength or less. A quarter wavelength at 100 Hz is about 2.8 feet; you do the rest of the math. Also forget both reflectors and damping; both the Tuba 18 and Tuba 24 don't use either, with no degradation in performance. Standing waves for the most part only exist in the minds of advertising executives. The poster who noted that SPL was the same from an indentical box with either one or two drivers was correct to a point. While wattage sensitivity renains the same, voltage sensitivity does go up by 3dB, as the halving of impedance doubles the wattage in for a given voltage. By the same token total output power is up 3dB, due to the doubling of PMax. However, what you don't get is the 6dB voltage sensitivity/power output gain that direct radiators acheive from doubling drivers. That because doubling cone area in a direct radiator acheives an effciency gain of 3dB from the doubling of radiating area, but in a horn the radiating area is the horn mouth, and since doubling or quadupling or googleplexing the mumber of drivers at the throat does not change the throat size the horn efficiency remains the same, only the input power capacity changes.
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Re: How did Kirk defeat Khan? [message #16538 is a reply to message #16537] |
Mon, 24 May 2004 16:22 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18758 Registered: January 2001
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Illuminati (33rd Degree) |
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I don't really think that either Adrian's or Mike's thinking is two dimensional, it's just that their horns are probably of uniform width so a two-dimensional CAD drawing has everything needed to describe them. As for standing waves, you're right about doing the math. No matter how it's folded, if you have three sections of approximately three feet each, I'd expect the horn to work well up to about 100Hz. So as long as output is limited to 100Hz, it should be alright. Still, one thing that's attractive to me about the equiangular spiral is that the radius is constantly increasing. When a horn is folded to approximate this shape, each section's length is different and that tends to break up the standing wave modes along the long dimension.
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Re: How did Kirk defeat Khan? [message #16542 is a reply to message #16538] |
Tue, 25 May 2004 06:05 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Bill Fitzmaurice
Messages: 335 Registered: May 2009
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Grand Master |
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My point was that if you do all your designing/thinking from a standpoint of two dimensions that you can overlook the benefits of going off on a tangent, literally. Keeping the horn uniform width is logical from both a design and a construction standpoint, and in basshorns is also sonically sound practice. However, sometimes your design goal can better be achieved by sending the pathway at a right angle to its nominal direction, or for that matter by loading the driver from the side of the box rather than the front or rear. I can't say if I first used that method, but I've been using it since Snail III back in '96, and that one simple concept has made possible and been used in every horn I've built since then. The equiangular spiral I agree is the best folding method from a variety of standpoints for basshorns. It's the foundation for my Tuba sub series for just that reason.
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Re: How did Kirk defeat Khan? [message #16545 is a reply to message #16542] |
Tue, 25 May 2004 07:58 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Adrian Mack
Messages: 568 Registered: May 2009
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Illuminati (1st Degree) |
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> However, sometimes your design goal can better be achieved by > sending the pathway at a right angle to its nominal direction, or > for that matter by loading the driver from the side of the box > rather than the front or rear.I too considered something like this, but seems like a lot more work - mostly because I dont know how I would draw it up in CAD. Now thats a basshorn which really needs a lot of thinking! ~could it be more space-efficient than the spiral method?
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Throat hole [message #16546 is a reply to message #16534] |
Tue, 25 May 2004 08:03 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Adrian Mack
Messages: 568 Registered: May 2009
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Illuminati (1st Degree) |
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> I don't think its shape or proximity to the apex are terribly > important because the frequencies you'll be using the horn for are > so low. Cut it round or square, whichever is easiest for you to > do. I would position the woofer(s) near the apex and cut a hole > for each woofer, located centrally, just over the dust cap. Are you sure that doing a seperate hole for each woofer is OK? What you are saying makes sense, just want to make sure - I guess the horn wouldn't know where the drivers at this low freq's + close spacing.
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Re: How did Kirk defeat Khan? [message #16548 is a reply to message #16545] |
Tue, 25 May 2004 13:23 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to previous message](/forum/theme/AudioRoundTable/images/down.png) |
Bill Fitzmaurice
Messages: 335 Registered: May 2009
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Grand Master |
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First, don't think that I mean going with a terribly convoluted design; not only would it be hard to design, it might be impossible to build. But at the immediate throat area there's potential to use right angle pathways where cross-sections are small. One problem I've encountered with radial designs is that you can end up with rear chambers too large for effective reactance annulling, and some right angle paths close to the chamber can help make it smaller and put some of that area into the horn. One thing about McBean- keep trying smaller and smaller rear chambers; curiously the longer the horn the smaller rear chamber you need, relatively speaking. Can't help you with the CAD thing- I don't have it. I'm just at the point of giving serious consideration to a graphics program so I can finally retire the pad and pencil.
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