Why Do Passive Radiators Require Spiders? And Has Anybody Made Their Own? - Page 2 - diyAudio
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Old 9th February 2003, 03:43 AM   #11
Wizard of Kelts
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Much obliged, Ken.

I must admit, that is an odd way to do a Passive Radiator.
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Old 9th February 2003, 03:44 AM   #12
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I thought it was a bit odd too, I don't know the reason for the vents and it sure is loose and moves very easily.
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Old 9th February 2003, 10:24 AM   #13
7V is offline 7V  United Kingdom
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Not so odd really, Keltic. That's exactly what I was attempting to describe (badly) by saying: "I could cure this with another piece of material with another surround, connected to the first a little distance away. The passive radiator would then be a cylinder".

The purpose is to keep the radiator straight and stop it wobbling as it goes backwards and forwards. The cylinder must have some depth - the deeper it is, the more stable.

I hadn't seen this Celestian passive when I came up with my cylinder proposal - honest!

As for the vent, I don't know. If the foam plug on the inside is attached to both the back and front of the radiator, it should do nothing at all.
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Old 9th February 2003, 12:07 PM   #14
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Default Spiders

Yeah, using a spider also absorbs some of the acoustic load from the woofer. That is, the passive radiator doesn't just flop all over the place outside of its proper vertical alighnment, and higher masses can be used. I have some crappy passive radiators made by Pioneer that only had one surround, and they flopped around terribly. Definitive Tech uses a passive radiator that is 8" and has a surround on each side of the membrane, rather than just one surround. This does a better job of symmetrically supporting the weight.

I remember reading a web page about this somewhere real recently.

What someone needs to do is build an 18" passive radiator with a Blueprint 1803's basket and surround and dual spiders and a flat diaphragm for an ultra-excursion passive radiator to work with the Tumult.
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Old 9th February 2003, 01:27 PM   #15
tvi is offline tvi  Australia
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The following might be of interest.
<a href="http://www.danmarx.org/audioinnovation/flatpassives.html">Flat Passive Radiators ~ Tricks & Methods</a>
<a href="http://www.earthquakesound.com/slaps.htm">SLAPS12 & SLAPS15</a>
and the patent is here
<a href="http://164.195.100.11/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=6044925.WKU.&OS=PN/6044925&RS=PN/6044925">US Patent 6,044,925 &nbsp; &nbsp;&nbsp; Sahyoun &nbsp;&nbsp;&nbsp; April 4, 2000 &nbsp;&nbsp;&nbsp; Passive speaker </a>



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James
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Old 9th February 2003, 02:45 PM   #16
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Interesting sites TVI but considering that celestion has been making PR's since the very early 70's with almost the same method I have to wonder why celestion never applied for patent.
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Old 9th February 2003, 03:41 PM   #17
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In fact, is the patent even valid?
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Old 9th February 2003, 03:49 PM   #18
tvi is offline tvi  Australia
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I think the patent office considers an idea "novel" and therefor patentable if it not in the first 10 hits from Google.

James
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Old 9th February 2003, 04:38 PM   #19
kneadle is offline kneadle  United States
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Quote:
Originally posted by kelticwizard
Ken:

Something like this?

LOL, MS Paint doesn't circles. which leaves me to do it Freehand, with all too predictable results.

Sure it does circles...
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File Type: jpg mspaint.jpg (8.0 KB, 203 views)
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Old 9th February 2003, 05:27 PM   #20
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Thanks, Kneadle.

Only thing is, that tool draws not only circles, but ovals as well. Whenever I get the shape to where I want it to be positioned, it's an oval, and whenever I get it to be a circle, it isn't in the position where I want it to be.

So I settled for Freehand.
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