Exotic CNC'd 100Hz-600Hz bass horn - help sim please - diyAudio
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Old 19th January 2016, 10:08 AM   #1
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Default Exotic CNC'd 100Hz-600Hz bass horn - help sim please

Looking at a new design for Tractrix base horn, target 100hz to 600hz

Attached, see drawing showing:

Varying mouth sizes from 4032cm sq to 4608cm sq

Throat can be sized to suit driver/horn (notionally 110cm sq to 260cm sq)

Back chamber vol notionally at 22,800 cm cube (0.8 cubic foot)

Three driver specs shown of B&C 8, 10 and 12 inch.

Axial horn length 1.4m (55 inches)

My questions:

Which driver size to aim for given horn range?

What size throat once q1 decided?

What size throat?

What best/max width of can to increase mouth size to suit? (I wish to limit height to 120cm, and prefer to keep width under 42cm.

Any help greatly appreciated.

Andrew.
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Old 19th January 2016, 10:11 AM   #2
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Sorry, pic rotated.
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Old 19th January 2016, 10:17 AM   #3
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The curved sides would cover the chamber for a beat look

My last project Lowther Alfredo used birch ply, ice taken cues from that.

Pics New Lowther "Alfredo" horn using CNC'd Birch Ply
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Old 21st January 2016, 02:34 AM   #4
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Here is the spec for the B&C 10PE driver. Good Fs, good sensitivity, good range to 4,000hz.

Lowish Xmas, so need to take care with EQ if pushing low freq.

B&C 10PE26 10" Professional Midbass 8 Ohm
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Old 21st January 2016, 03:55 AM   #5
GM is offline GM  United States
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Fs wise the 8PE is the best 'fit', but probably a poor choice for what you want to do. That said, setting an arbitrary length, then trying to 'fit' a driver to it to cover a specific BW is well beyond my math skills without access to my various Excel designer programs, so 'sounds' like you need to fire up Hornresp and let its designer help you.

GM
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Old 21st January 2016, 09:11 AM   #6
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Quote:
Originally Posted by GM View Post
Fs wise the 8PE is the best 'fit', but probably a poor choice for what you want to do. That said, setting an arbitrary length, then trying to 'fit' a driver to it to cover a specific BW is well beyond my math skills without access to my various Excel designer programs, so 'sounds' like you need to fire up Hornresp and let its designer help you.

GM
Thanks Greg.

The 'arbitrary' setting of the horn length is just a starting point, as I have some cab size restrictions.

If the exercise yields a smooth horn profile, untruncated, and min 100hz, I'll be happy.

Thanks for the tip on the 8PE....I used this driver once before in a John Inlow horn.

Kind regards

Andrew.
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Old 21st January 2016, 09:14 AM   #7
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GM, one other question I firgot to post, why do you suggest the 8PE is not ideal for the mid bass application I'm looking at? Do you have another driver in mind? Kindly.
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Old 21st January 2016, 09:45 AM   #8
AllenB is offline AllenB  Australia
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I've played with the 8PE on tractrix like horns with closed rear. I could get it on to a 124Hz horn, but with virtually no benefit over something a little higher, say 140-5Hz seeming to be the optimum lower fc.
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Old 21st January 2016, 03:28 PM   #9
GM is offline GM  United States
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Originally Posted by atilsley View Post
GM, one other question I firgot to post, why do you suggest the 8PE is not ideal for the mid bass application I'm looking at? Do you have another driver in mind? Kindly.
In general, the smaller the [prosound] driver, the higher its Fs, ergo the higher its lower and upper mass corners [Flm = Fs*Qts/2, Fhm = 2*Fs/Qts], so for a tractrix the throat size tends to be > driver Sd for an optimum alignment, ergo either dual [or even quad] drivers or a larger driver with different specs is required to keep the horn as short as practical.

In short, you theoretically want a driver with specs that has a ~600 Hz Fhm with a ~1:1 CR that when pre-loaded with a reasonably small rear chamber 'rings' at [~100-600 Hz]^0.5 = ~245 Hz.

At a glance then, an 8 - 10" driver is required since 600 Hz = a ~7.2" dia., though this will make for a long horn, but if we truncate it where the throat is ~1 WL across, then dual 12" or a single 15" with the right specs can be used. This was the 'breakthrough' solution in the '40s to get a low frequency horn in a short enough cab to also be physically time aligned with the HF horn, and why it's still in use today, though DSL's designs and its [illegal] variants are slowly, but surely, going to make them as obsolete as they deserve to be.

GM
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Old 21st January 2016, 07:56 PM   #10
AllenB is offline AllenB  Australia
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With your indulgence, Andrew.
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though DSL's designs and its [illegal] variants are slowly, but surely, going to make them as obsolete as they deserve to be.
Interesting point of view, but I see the co-entrant horn as a separate matter.

If a good way to guide a mid and a tweeter means their horns turn out to be similar, peoples discovery of this through the synergy may be pure coincidence. I may be missing your point.

Otherwise synergy profiles are considered under a more limiting set of constraints, not that that has to be a problem. Why don't you like tractrices in the lower mid band?
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