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Old 8th March 2011, 04:54 PM   #531
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Here are the new path dimensions for the box drawing in post #521.

S1=462.90cm2, S2=512.37cm2, S3=793.55cm2, S4=1901.20cm2, and S5=2413.70cm2
L12=17.15cm, L23=128.9cm, L34=83.50cm, and L45=22.225cm
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Old 8th March 2011, 04:58 PM   #532
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Quote:
The over all path leght is about 97.875" long, but do you do the box resonance from S1 to S5 or S2 to S4 in a tapped horn.
Is this question to simple or to hard to have no replys yet?
Andy
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Old 8th March 2011, 06:44 PM   #533
tb46 is offline tb46  United States
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Hi 4pyros,

If you are thinking about a resonance frequency as in a bass reflex enclosure, the tapped horn doesn't work that way. Take a look at the impedance curve in Hornresp, it may help. Otherwise, maybe these threads by Don Snyder will be of use:

Elements of a Tapped Horn

Evolution of the Tapped Horn

Regards,
__________________
Oliver
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Old 8th March 2011, 07:41 PM   #534
Djim is offline Djim  Netherlands
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Hey 4Pyros,

I don’t know how accurate your drawing is but it looks like your corner corrections (corner bracing) can be improved.
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Old 8th March 2011, 07:46 PM   #535
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Quote:
If you are thinking about a resonance frequency as in a bass reflex enclosure, the tapped horn doesn't work that way. Take a look at the impedance curve in Hornresp, it may help. Otherwise, maybe these threads by Don Snyder will be of use:
Thanks Oliver I will look at that. Ya the mouth area thru me off to. Andy
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Old 8th March 2011, 08:04 PM   #536
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Quote:
I don’t know how accurate your drawing is but it looks like your corner corrections (corner bracing) can be improved.
OK Djim; A peeny for your thoughts. The braces in the corners were put there to stiffen the box, eliminate parallel sides and take up some of the volume in the big corners. The top one may not even be needed now that I added the extra angled board in the middle. They were not dimensioned because thay will be made from what ever is left over after the rest of the box is cut. I dont think the dimensions are critical as long as the angel is graiter than 11 degrees.I also plane on doing some central bracing from the back, across the lower part of the speaker mount piece, to the bottom. Its just not on the drawing. What are your thoughts? Andy
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Old 8th March 2011, 09:31 PM   #537
Djim is offline Djim  Netherlands
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Andy, a couple of months ago there were some discussions about bending in TH’s (Jbells "flute theory") Since then I have read a lot about bending in 'big' flutes/horns. Besides that I also have been talking to instrument makers and engineers that are involved with butane gas installation (high pressure) who also work a lot with bending.

Anyways, it’s not the parallel walls (resonance) you should worry about but it’s about so called ‘non-gentle-bending”. This is often represented in 90 degree bends in TH’s. Instead of resonances it’s the difference in speeds of the air molecules (high mass - low mass as result of those speed differences) that can cause errors in the output. For instance if you have two 180 degree bends in a ‘S’ form construction, they both will equalise the speed as result of the ‘S’ form (opposite bending construction). You can call such construction a gentle bending.

But many TH designs have often two 90 degree bends that are not the opposite of each other. They bend in the same direction and therefore amplify the speed differences. In that case your bends can benefit from corner corrections to optimise the pathway.

Instead of one corner brace I use at least two braces per corner to get a more ideal pathway. In realy big corners I use at least 3 bracings to come closer to the ideal path. I'll use your drawing as an example...


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Old 8th March 2011, 11:31 PM   #538
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In regards to grills, I read jbell's intention of using the Dayton square grill: http://www.parts-express.com/pe/psho...62-898&scqty=1
You get 1 pair - each grill is just 2 inches shy of getting 2 SS15 grills from 1 Dayton grill for $55. You've got quite a bit left over... Looks like a bit of wasted grill..

Has anyone had success with other gill material/brand?


Justin

Last edited by CRESCENDO; 8th March 2011 at 11:35 PM. Reason: Clarity
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Old 8th March 2011, 11:32 PM   #539
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Djim; So you are saying the additional deflectors would keep the air molecules moving faster around the outside of the bends? I read that 45 degree deflectors are no good, your thoughts? Should I do the corners of the other 180 degree bend as well? Would it be worth it to use one half of a 10" pipe in that bend?
Thanks Andy

Last edited by 4pyros; 8th March 2011 at 11:35 PM.
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Old 8th March 2011, 11:41 PM   #540
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Quote:
Has anyone had success with other gill material/brand?
Justin; I am using expanded and flattened aluminum with 1 X 3/8 slots mainly to keep the mice out. Picked up 2 4'X8' sheets from a local aluminum supplyer for $75 total. Its listed in McMasterCarr for a lot more.
Andy

Last edited by 4pyros; 8th March 2011 at 11:57 PM.
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