Bose Speakers Again

alan cordeiro alancordeiro at
Mon Dec 16 22:19:50 EST 2002

Hi Derek,

The squawking you described is similar to the sounds my left door speaker
made before I removed it. It old fashioned terms the symptoms were described
as "motor-boating" usually as a result of insufficient decoupling on the
supply feeding the amplifier active devices.

Electrolytic capacitors seem to last a lot longer these days, but they tend
to dry up slowly over many years. Its not the same effect, but is similar
to the way a battery gets "old" after four or five years, as it loses its
plate surface area. For electrolytic capacitors, slow drying up of the
electrolyte (with no visible external signs, unless the cap springs
a big leak with overheating) is similar to grease in bearings going slowly
dry over many years. The capacitance slowly decreases until it hits the
threshold where positive feedback occurs, hence the "motor-boating".

85 degree C caps will do fine for the auto environment, will get you
probably 8-10 years..... I would not worry about insisting on the higher
temperature type. Yes, in the long run, the higher temperature types
are built of better sealing materials, and have some overdesign in
internal working surfaces, better chemicals etc, but, the parts are
12 years old already. Personally, I would wait to get the higher
temperature parts, but, that's like using synthetic oil on a non-turbo car,
the extra improvement will make a small difference in the long run,
but barely noticeably.

I remember someone had some extra capacitors left from an earlier bulk
buy from DigiKey, but I cannot remember who. Perhaps they could send you
a few directly........

Good luck,

Bose on three good speakers, (one in the garage)

----- Original Message -----
From: "Derek Pulvino" <dbpulvino at>
To: <brett at>; <200q20v at>
Cc: <sscalmanini at>
Sent: Monday, December 16, 2002 9:30 PM
Subject: Re: Bose Speakers Again

> Ye gats!  God knows I'm not equiped for that temperature range.  I was
> thinking about the "microclimate" inside the speaker/amp.  I have no idea
> what operating range inside the speaker is and so wonder if that might be
> near the tolerance.
> dp
> >
> >From a strictly armchair-engineer standpoint, I'd say 85 degree rating is
> >probably fine.
> >
> >Brett
> >--
> >----
> >"They that give up essential liberty to obtain temporary
> >safety deserve neither liberty nor safety." - Ben Franklin
> >
> >
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