checking horn measurments are correct

After designing my 6" horn i was not happy with the sound so i decided to double check my original measurments. And you guessed it a fatal error on my part in the original maths. Its been a long time since i left skool but i think they are now correct.... (not). I have used a common equation to work out the throat area.



after working out the maths again i think im doing something wrong!!!!!!! what do you guys think........ 3cm by 3cm seems way too small..... or im a being silly and doing something wrong.

Regarding some Tony Ass advice (many thanks) a throat too small at high frequency cause a lot of resonance.
The math seems correct...I get the same results modelling an horn for an 8"...because ot this little throat I start modelling a simple conical phase plug but it continue to be to small. However the formula to get the phase plug radius on the throat is quite simple.
sqrt(((driver area)-(throat area))/pi())
after that you have to model a cone, so the radius gradually decrease and become 0 at the end of the horn or before if you want but it's only a building issue.
so to get a bigger throat phase plugged or not I search a driver with an higher fs, high qts, ecc...and I found this 8" by rcf www.rcf.it/it_IT/web/rcf/products/precis...-transducers/mr8n301
but for my purpose...a mid high horn from 800 to 2500 hz was a little expensive...and the build not so easy..so now I used a bms 4550 on altec 811 b horn.

cheers, bitzo

thanks bitzo very helpfull.

I've spotted some minor errors in your maths.

In that formula Vas should be in cubic metres, you used litres. To convert litres to m3 you need to divide by 1000.

The area of throat is given in square metres. To convert this to square cm you multiply by 10000.

This gives a throat of 32.61 cm2.

If you want a square throat the size will be 5.71*5.71 cm. A circular throat would be 6.4 cm diameter.

You probably want a phase plug in this horn, this is where the fun starts. Choose your horn throat area (there are a few ways to decide on this), subtract your calculated area (32.61) and you are left with the required plug area. Divide this by pi, square root of this and multiply by two to get the plug diameter.

Have fun!

cheers kieran i new the maths were wrong but i couldnt work out what i had done wrong..... smiley16

because of a fault last nights post have been lost so ill try and remember all that was posted....

this the equation i am using for the horns i am building, this equation is for the throatsize.



the next equation is for the mouthsize.



I think it was jsg that posted a link to a white paper by d.b. keele in regards to horn designs.

www.xlrtechs.com/dbkeele.com/PDF ... 0Paras.pdf

with a little help from kiaran i think my maths are now correct for the throatsize....

i have had a go at the throatsize as well...... its been a while for algebra for me.



i hope it is correct..

Hello again,

How did you choose the flare frquency? This should be the lowest frequency you wish to use, I assume you used the highest frequency?

What range are you hoping to cover? I'm working on a 6" mid horn at the moment, I will be interested to see how yours compares, there are a lot of options to consider as well as a lot of comprimises to be made when building horns.

When choosing mouth area I usually use the good old rule of thumb that the mouth circumference should equal the lowest wavelength, for a horn in free space. Of course there is more to it, look up Keeles 'optimum horn mouth size' paper for (lots) more reading on the subject.

Kieran

thanks again kieran the 6" horn im designing is for my mt121. It will sit above the 12" section and im gonna put a 1.5" in side the 12" section hanging from the top of the 12" (xtro style). What are you planning to use your 6" for........