[TenTec] Centaur cooling mod for lower noise?

[Dr. Gerald N. Johnson]

On Sun, 2006-06-18 at 21:07 -0500, Duane A Calvin wrote:
> Jerry,
>         Carl's answer is the short and sweet one.  I had an interesting
> exchange of letters with the TT president about the Centaur when it came
> out and I documented the noise level in my shack caused by it.  No help. 
> However, I did take it in to the acoustic lab where I work and had one of
> their engineers look it over.  I had noticed that with the covers off,
> the fan was relatively quiet, but if you put anything close to the fan
> intake, it got very noisy very quickly.  The engineer agreed and said it
> was the shock wave (if I'm remembering it correctly) from the leading
> edge of each fan blade which was striking the slot openings in the
> cabinet side (which is, essentially, too close to the fan).  Sort of like
> playing cards on a spoked bicycle wheel.  The best answer is to do what
> Carl did and remove the material in front of the fan, or, as one fellow
> did, use a pair of pliers and "twist" each of the bars so that it takes
> on a 45 degree (or so) angle.  The latter option will reduce, but not
> eliminate the noise.  I took the more expensive route, and traded my
> Centaur on a Centurion.  No more noise - hi!
> 
>         73,  Duane

Its hard to quiet a siren (where the fan blades chop off the air flow
through holes), but maybe if the grill was removed and a few feet of 4"
flexible sound silencer duct was attached, it would be passably quiet.
Like used for high velocity air conditioning ducts. Or a box inlet along
side made of fiberglass lined rigid ducting material.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer