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holler
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Redirecting mini siren sound output

Mon Jan 28, 2008 3:05 am

I recently purchased this mini siren off of ebay, and it is has a pretty good sound output but there is one problem, all of the sound output seems to be directed out of the front of the siren, even though the ports are on the side and exposed & you easily feel the air blowing out of them. If I try to force more air into the front of the siren it actually seems to bog down, unlike my hand siren which gets louder when it has "forced induction". Does anybody have any idea why it is doing this? Is the rotor design?

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Justin
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Mon Jan 28, 2008 4:07 am

Which way does the rotor spin?

Did you try reversing the direction?

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holler
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Mon Jan 28, 2008 4:13 am

It is spinning the right direction, but what is causing the bog down when air is forced into the front?

Justin
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Mon Jan 28, 2008 4:17 am

Could quite possibly be the rotor design; you only usually see squared off blades rather than those curved ones (going off those 12V sirens Adam turned into his doorbell).

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holler
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Mon Jan 28, 2008 4:22 am

Justin wrote:Could quite possibly be the rotor design; you only usually see squared off blades rather than those curved ones (going off those 12V sirens Adam turned into his doorbell).
Yeah I know, the rotor on this one looks more like a ducted fan that a true siren rotor.

my other little mini siren has squared off blades just like a "real" siren.

Justin
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Mon Jan 28, 2008 4:25 am

holler wrote:Yeah I know, the rotor on this one looks more like a ducted fan that a true siren rotor.
I've always wondered if that curved blade design translated into more decibels. Notice a difference?

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Daniel
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Mon Jan 28, 2008 4:33 am

It seems that the clearance between the rotor and stator is very large, which will cut down on sound output.
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holler
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Mon Jan 28, 2008 4:34 am

Well it does make a lot of racket, I will make a recording of it sometime this week if I am not too busy. It has a tone very similiar to that of a T-128, nice and low.

Didn't Decot's use slanted rotor blades to get a high output?

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Daniel
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Mon Jan 28, 2008 4:37 am

holler wrote:Well it does make a lot of racket, I will make a recording of it sometime this week if I am not too busy. It has a tone very similiar to that of a T-128, nice and low.

Didn't Decot's use slanted rotor blades to get a high output?
I'm not sure about Decot, but Hedberg sirens had curved blades.
Lex orandi, lex credendi, lex vivendi.

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Mon Jan 28, 2008 1:57 pm

Q2B sirens had curved blades, and Decot sirens had angled blades. However, can you make a video of the miniature siren that you have?

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