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Old 17th January 2014, 06:03 PM   #1
jerryo is offline jerryo  Isle of Man
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Default Torus

Hi,
just a quick question: "Has anybody any experience or thoughts about using a torus/doughnut shape as an open baffle for a wide band/full range driver?

I only ask as the shape seems to me to offer two possible advantages:

1: a degree of waveguide type loading
2: the longest possible path from the front to the rear of the driver for any given baffle size.

(a torus having an overall width of 3 x the central hole diameter)
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Old 17th January 2014, 07:37 PM   #2
GM is online now GM  United States
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A pity that 'JohninCR' is no longer active in DIY audio [at least here] to tell you about his, but then again it's at least partly because after many speaker alignment experiments from the mundane to the bizarre, he decreed his rolled over dipole waveguide was the 'light at the end of the tunnel' or some-such, ‘disappearing’ shortly thereafter.

Best then to design a proper WG such as a 180 degree rolled over LeCleac’h than just accept a specific mathematical shape.

GM
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Old 17th January 2014, 08:40 PM   #3
xrk971 is offline xrk971  United States
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Put two LeCleac'h with roundovers back to back and you have a dipole torus speaker...
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Old 17th January 2014, 08:50 PM   #4
chrisb is offline chrisb  Canada
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Greg - yes, John was lots of fun - bless him where / whatever he's up to
- maybe he created his own acoustic even horizon and is inside enjoying the hell out of his system, just can't report back
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Old 17th January 2014, 11:40 PM   #5
GM is online now GM  United States
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Quote:
Originally Posted by xrk971 View Post
Put two LeCleac'h with roundovers back to back and you have a dipole torus speaker...
Isn't that what I suggested?

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Old 17th January 2014, 11:58 PM   #6
wesayso is offline wesayso  Netherlands
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Is that even possible in foam core?

Last edited by wesayso; 18th January 2014 at 12:11 AM.
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Old 18th January 2014, 08:15 AM   #7
jerryo is offline jerryo  Isle of Man
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Hi,
of the two points that I mentioned the second maybe the more interesting, in that, for any open baffle the baffle width is important for the lower frequencies and the torus shape allows the longest path from front to back of any given baffle diameter. Also the dispersion from the driver will be very similar to that of a sphere initially.
To make a torus is considered difficult but I thought I would try the following method:

Take one wheelbarrow/cart tyre inner tube for a 10" wheel (they approximate a torus) remove the air valve from the valve stem and fill the inside of the tyre with expanding cavity foam (a little water needs to be put into the tube for the foam to cure) The expansion of the foam should fill the rubber inner tube to its full shape with some exiting throughout the valve stem. The volume of the torus can be easily calculated so enough foam is added!
When it has set one could trim the valve stem flush and leave the rubber, this would be hidden by the driver mount. It might be possible to remove the rubber tube by cutting through the rubber and peeling off. I'm not sure how well expanding foam sticks to rubber so it might be prudent to oil the interior of the rubber tube before filling with foam if the rubber is to be removed.
I thought of this method of making a close approximation of a torus some time ago and I will try it one day. It would not take long at all.
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Old 18th January 2014, 03:19 PM   #8
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by wesayso View Post
Is that even possible in foam core?
Yes, with gore shaped panels scored and curved and hot melt glued.
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