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Old 15th July 2003, 11:07 AM   #1
advisd is offline advisd  Chile
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Lightbulb Front Horn

Hello :

I have 8 inch Loud Speakers .
I really like to make a front tractriX Horn and a rear compression box, for this drivers .
I Donīt know nothing about Horn Speakers built.
I donīt know the cutoff frequency for the horn Speaker.
The Raw Drivers parameters are :
Fs: 32.55 Hz
Qts: 0..2256
Qes: 0.2559
Cone Area : 0.0263 m^2
Vas : 78.5 liters or 2.77 cubic feet
Re: 6.4 ohms
BL : 12.29
Rmax 55.87 ohms
Le : 0.9908mH
Efficiency 92.07 dB 1w/1m

For the hi-frequency a Beyma Driver (fs: 970 hz , 9,5BL)
I donīt know the cutoff frequency for the horn Speaker.....

Do you think is a good idea a frontal horn and 600Hz frequency cutoff for the Beyma?

Thank ..
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Old 16th July 2003, 04:29 AM   #2
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http://melhuish.org 'single driver website' theres lots of info there.

use hornresp to model response. it isnt so easy but is ok when you know what all the things do.


www.volvotreter.de <tractix horn>
http://hem.passagen.se/sajberrapid
<home made basshorn,midrange horn also>

there is a few links around for hornspeakers and info on them if you look in yahoo.com
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Old 16th July 2003, 01:26 PM   #3
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Hi.
Cutoff frequency of front horns means Low cutoff.
In a thin craft manual of Fostex, I found formulae for front horns.
To make it easy to understand, I simulated in place of you.
Setting cutoff at 250Hz, which seems suitable.

Cut off : 250Hz
Sound speed : 34,400 cm/s

Exponential modulus = 4*3.14*250/ 34400 = 0.091
Radius of exit (if it were a round exit) = 2 / 0.091 = 22 cm
Superficies of Exit = 22*22*3.14=1520 scm

If you take 80% of Cone area for Hornfs entrance, 210.4 scm,
Length of horn = (1 / 0.091)*log (1520 / 210.4) = 21.7 cm
Sectional superficies at each X cm length, scm = 1*exp(0.091*X)*210.4

At first I tried this simulation on Microsoft Excel,
but it was not correct in calculating LOG.
I donft know why. Then, I used a scientific calculator.

And you mean Rear compression box for back-loaded horn?
Formula for back-loaded horns is common with frontal one.

It's only to adapt the formula of Sectional superficies.
Length of back-loaded horns; you can set it at your liberty.
(2-3m is supposed to be good.)
Then, simulate until you get suitable numeric.

Formula to calculate the Hi-cut of back-loaded horn;
Cross over frequency(Hz) = 10*So / V
So : superficies of entrance (scm)
V : Volume of compression chamber (litters)

In both front and back horns, its proper entrance superficies
is supposed to be 70-90% of cone area.
In my experience of building back-loaded horns, 80% seems innocuous.

Optimum cross over shifts by which driver you use.
In average back-loaded horns, proper range is 150-200Hz.
But if you reinforce this range by front-horn
or using woofers for the driver, maybe it is better to be lower.

Good luck in your plan!
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Old 16th July 2003, 02:24 PM   #4
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if you use hornresp,you can input these formula numbers,see what the response is.


if i have some spare time in the next week,il model it,see how it goes ,as a favour ,since i enjoy people with more experience doing stuff for me too!
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Old 17th July 2003, 07:45 AM   #5
advisd is offline advisd  Chile
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Hello :

This Pictures are the SPL response for 8 inch woofer made by hornresp Software ( thankX mikee12345 for the information )

The first picture:
Is Cutoff frequency 200 HZ , Internal TractriX Horn area 100 , external TractriX Horn area 2354,21 , angle 90°, Rear compression Chamber volume 2.8 liters.

The second picture:
Is Cutoff frequency 600 HZ , Internal TractriX Horn area 23,58 , external TractriX Horn area 249,68, angle 90°, Rear compression Chamber volume 15 liters.

Cutoff frequency of front horns means Low cutoff and 2-3m is supposed to be good for rear chamber (thankX Odio Yayakoshi )

I really like 200Hz for the Horn Speakers.
If I was typing the correct data in the Software parameters, the second picture looks like better and works more frequency than 200HZ simulation.

I like to Know what picture is not correct ...
I mean I want the better performance for the 8inch driver.

ThankX
AdvisD
Attached Images
File Type: jpg woofer8inch.jpg (84.9 KB, 689 views)
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Old 18th July 2003, 03:27 AM   #6
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I'm awfully sorry I introduced exponential one,
not tractrix. I regret my mistake.
If my simulation was accepted something like as
nipping to mikee, or made a confusion, I apologise.
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Old 18th July 2003, 08:08 AM   #7
advisd is offline advisd  Chile
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This are the pictures:

****************************************
*Odio Yayakoshi ; NO hay problema , no problem *
* *
*AdvisD fom Chile. *
****************************************
Attached Images
File Type: jpg woofer8inch2.jpg (47.1 KB, 668 views)
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Old 2nd December 2003, 03:51 PM   #8
advisd is offline advisd  Chile
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Default Front Horn part II

Attached Images
File Type: jpg proyectosm-118.jpg (67.4 KB, 521 views)
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Old 3rd December 2003, 04:47 AM   #9
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No problem

is that picture of the previously modeled horns!

you have nice response

Note-Mcbeans hornresp doesnt take into account increasing directionality at high frequencies,so HF may be looking low.

Cheers!

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Old 3rd December 2003, 03:47 PM   #10
advisd is offline advisd  Chile
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The Hornresp SPL-response pictures are from 8 inch Loud Speakers previous simulation.

For this designs, I changed this 8 inch driver and assembly 18 inch woofer in a ported gabinet
In the last pictures Beyma Sm118 woofer
Beyma CM-250 driver , 650 Hz Tractrix Horn.
The small round Tractrix Horn, normal dome tweeter installed.

Daniel.
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