Han wrote:

mac davis wrote in
:

On Tue, 23 Dec 2008 16:53:34 -0800 (PST), Robatoy
wrote:

On Dec 23, 7:44*pm, B A R R Y wrote:
PDQ wrote:

As to fines, the cyclone culls out almost all the big lumps (think
jointer or planer) but does not do as good a job with the fine
stuff as a lot of that still gets to the filters.

That's why John said "properly designed".

My JDS has had over 200 gallons of junk sucked in over the last
three months, with less than 2 gallons in the filter bag.

I use a decent amount of MDF and plywood, and own a 22" drum sander,
so I get plenty of "fine" dust. *It's really obvious just by looking
in the drum how much fine dust the drum catches.

I know you know your dB's. JDS claims 78 dB. Is that even close?

I had a real interesting discussion here about "sound suppressors" a
few years ago, don't know if you remember it..
I was trying to figure out how the DC muffler from Penn State could
lower the DB's 7 to 10 db's for "up to a 50% reduction"..
Sounded like snake oil to me, so I asked here and got lots of answers
that used math to explain it and were beyond my understanding..
Then, someone (Dr. Deb?) said that they had one and it lowered it
nicely..

I bought one and was really amazed at the difference... Cheap "2 hp"
DC from Harbor Freight, went from shouting to someone next to you to
talking in an almost normal tone..

Got explained to me later in terms that I could understand.. Something
about taking even a few DB off the top lowers the "annoying" level
quite a bit.. Anyway, works for me and I'd never run a DC without one
now.. YMWV


mac

Please remove splinters before emailing

Hey mac!

The scale for dB is logarithmic - I think that each increase of 1 means
10 times more, just as the Richter scale for earthquakes. Better look at
wikipedia for more info. How come you need a reduction of 7 to 10 dB for
50% reduction is not immediately clear, unless we have to go back to the
Bel decibel is 1/10 of a Bel). Then 10 dB=1 B, or a factor 2. But maybe
I need more coffee, and then advice from DIL, who teaches physics in a
high school.


In the Decibel scale, a 3 dB reduction equates to a reduction by 1/2. dB
scale is logarithmic. Depending upon whether one is converting from power
or not, the conversion from linear scale to logarithmic scale is either
dB = 10 * log10(P) or dB = 20 * log10(A).


--
If you're going to be dumb, you better be tough