Sign in with
Sign up | Sign in
Your question

Using a limiter to protect speakers?

Last response: in Home Audio
Share
Anonymous
January 22, 2005 5:38:03 PM

Archived from groups: rec.audio.pro (More info?)

Howdy,

I've a custom-built pair of LS3/5A's....I worked very hard to build them
attractively and exactly to spec and it would be a shame for them to be
accidentally blown up by one of my dumbass friends or by my own dumbass. I
understand these speakers shouldn't be driven beyond about 90dB (I'm
assuming that's SPL)....so I'd like to put a limiter on them after the power
amp stage to hard limit the signal at a certain dBV ....I don't need any
fancy compression or ADSR type functions, it doesn't even need to sound good
when the limiter is ON as long as it's quiet when the limiter is OFF. What
do ya'll recommend? The cheaper the better! Thanks!

PS: power amp is an adcom 535II

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com
Anonymous
January 22, 2005 5:44:50 PM

Archived from groups: rec.audio.pro (More info?)

On second thought, why not wire fuses in between the power amp and the
drivers/crossovers? What value/type of fuse would I use? Thanks!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote in message
news:WbOdnRRxWLU9fm_cRVn-vg@comcast.com...
> Howdy,
>
> I've a custom-built pair of LS3/5A's....I worked very hard to build them
> attractively and exactly to spec and it would be a shame for them to be
> accidentally blown up by one of my dumbass friends or by my own dumbass. I
> understand these speakers shouldn't be driven beyond about 90dB (I'm
> assuming that's SPL)....so I'd like to put a limiter on them after the
power
> amp stage to hard limit the signal at a certain dBV ....I don't need any
> fancy compression or ADSR type functions, it doesn't even need to sound
good
> when the limiter is ON as long as it's quiet when the limiter is OFF. What
> do ya'll recommend? The cheaper the better! Thanks!
>
> PS: power amp is an adcom 535II
>
> --
>
> Jonny Durango
>
> "Patrick was a saint. I ain't."
>
> http://www.jdurango.com
>
>
>
>
Anonymous
January 22, 2005 6:40:30 PM

Archived from groups: rec.audio.pro (More info?)

I'm unaware of any post-amp limiters - after all it would need to drive
the speakers itself, right? I'm guessing you could insert some sort of
limiter right before the amp, but dialing it in for an EXACT level to
limit to speaker voltage - hmmmm - that would be hard to do without a
voltmeter or scope to actually measure it.
Related resources
Anonymous
January 22, 2005 7:09:25 PM

Archived from groups: rec.audio.pro (More info?)

Limiting is not a good idea because it clips the signal -- and that's something
you don't want to do, especially at high volume levels. Go with fuses.
Fast-blow. Though I'm not sure what value. Try two amps and see what happens.

One of the "nice" (?) things about the LS3/5as is that they sound "gagged" at
only moderate volume levels. If you're not inebriated, that alone should keep
you from turning up the volume too far.
Anonymous
January 22, 2005 8:06:16 PM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote:
> Howdy,
>
> I've a custom-built pair of LS3/5A's....I worked very hard to build them
> attractively and exactly to spec and it would be a shame for them to be
> accidentally blown up by one of my dumbass friends or by my own dumbass. I
> understand these speakers shouldn't be driven beyond about 90dB (I'm
> assuming that's SPL)

Why not pick up an analog SPL meter from Radio Shack ($50) and find the 90
dB SPL point. Place the SPL meter one meter distance from one speaker and
drive that speaker (other one muted) at a low volume with a 1 kHz sine. Turn
up the volume on the Adcom until the 90 dB point is reached. Note the
position on the Adcom and never turn it up past that point. Repeat the
procedure with the other speaker for a verification. If an AC RMS voltmeter
is available, measure the voltage across the speaker terminals at this
volume with the 1 kHz sine playing and use ohms law to infer the current
drawn, assuming 1 kHz wasn't at a complex impedance peak for the speaker.
Then use an AGC fuse rated for 125% of the inferred current to avoid trouble
from momentary lapses of reason.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com
Anonymous
January 22, 2005 9:07:22 PM

Archived from groups: rec.audio.pro (More info?)

> Howdy,
>
> I've a custom-built pair of LS3/5A's....I worked very hard to build them
> attractively and exactly to spec and it would be a shame for them to be
> accidentally blown up by one of my dumbass friends or by my own dumbass. I
> understand these speakers shouldn't be driven beyond about 90dB (I'm
> assuming that's SPL)....so I'd like to put a limiter on them after the
> power
> amp stage to hard limit the signal at a certain dBV ....I don't need any
> fancy compression or ADSR type functions, it doesn't even need to sound
> good
> when the limiter is ON as long as it's quiet when the limiter is OFF. What
> do ya'll recommend? The cheaper the better! Thanks!
>
> PS: power amp is an adcom 535II
>
> --
>
> Jonny Durango

You will need to determine how many watts your speakers can conservatively
handle. Then, pop one of these into the circuit (before the passive x-over
or drivers):

http://www.partsexpress.com/webpage.cfm?webpage_id=3&SO...

Craig
Anonymous
January 22, 2005 9:25:51 PM

Archived from groups: rec.audio.pro (More info?)

"Bob Smith" <rsmith@1nospam2.bsstudios.com> wrote in message
news:cpidnVAgVMwFZW_cRVn-vg@comcast.com...
> "Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote:
> >
> > I've a custom-built pair of LS3/5A's....I worked very hard to build them
> > attractively and exactly to spec and it would be a shame for them to be
> > accidentally blown up by one of my dumbass friends or by my own dumbass.
I
> > understand these speakers shouldn't be driven beyond about 90dB (I'm
> > assuming that's SPL)
>
> Why not pick up an analog SPL meter from Radio Shack ($50) and find the 90
> dB SPL point. Place the SPL meter one meter distance from one speaker and
> drive that speaker (other one muted) at a low volume with a 1 kHz sine.
Turn
> up the volume on the Adcom until the 90 dB point is reached. Note the
> position on the Adcom and never turn it up past that point. Repeat the
> procedure with the other speaker for a verification. If an AC RMS
voltmeter
> is available, measure the voltage across the speaker terminals at this
> volume with the 1 kHz sine playing and use ohms law to infer the current
> drawn, assuming 1 kHz wasn't at a complex impedance peak for the speaker.
> Then use an AGC fuse rated for 125% of the inferred current to avoid
trouble
> from momentary lapses of reason.

Ok, with a little trouble I found some impedance curves for two versions of
the LS3/5A. Both show 10 ohms at 250 Hz. Both show something above 25 ohms
at 1 kHz, therefore 1 kHz would be not be an ideal frequency to infer a max
current by measuring the RMS voltage. 1 kHz appears to be near an impedance
peak (800 Hz and 900 Hz depending on version). I also found some specs that
referenced 95 dB SPL max, two speakers driven at a distance of two meters.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com
Anonymous
January 22, 2005 10:34:58 PM

Archived from groups: rec.audio.pro (More info?)

Bob Smith wrote:

> Turn up the volume on the Adcom until the 90 dB point is reached.
> Note the position on the Adcom and never turn it up past that point.
> Repeat the procedure with the other speaker for a verification.


Problem is, this will change with different sources. Even different
passages of the same piece. (except maybe for something "modern")
Anonymous
January 22, 2005 10:34:59 PM

Archived from groups: rec.audio.pro (More info?)

"Joe Sensor" <crabcakes@emagic.net> wrote in message:
> Bob Smith wrote:
>
> > Turn up the volume on the Adcom until the 90 dB point is reached.
> > Note the position on the Adcom and never turn it up past that point.
> > Repeat the procedure with the other speaker for a verification.
>
>
> Problem is, this will change with different sources. Even different
> passages of the same piece. (except maybe for something "modern")

It's not perfect but better than knowing nothing. The speakers probably can
handle some extra SPL before something catastrophic happens. Swept sines and
an RTA would certainly be better. If 1 kHz is on an impedance peak pick some
other frequency away from the crossover and the resonant frequencies.

bob

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com
Anonymous
January 23, 2005 11:01:57 AM

Archived from groups: rec.audio.pro (More info?)

Jonny Durango wrote:

> I've a custom-built pair of LS3/5A's....I worked very hard to build
them
> attractively and exactly to spec and it would be a shame for them to
be
> accidentally blown up by one of my dumbass friends or by my own
dumbass.. What
> do ya'll recommend? The cheaper the better! Thanks!

buy a boom box or a pair of cheap speakers,
use it when you and friends are being dumbasses
any cheap solution, in fact most expensive solutions will color the
"sound" of these speakers
and that "sound" is what you worked so hard to get

dale
Anonymous
January 23, 2005 11:36:35 AM

Archived from groups: rec.audio.pro (More info?)

Well, let's see. An LS3/5a puts out about 80dB at a nominal 2.8V input,
which is the equivalent of 1W if the speaker was a resistive 8-ohm load.
(Hah!) So 90dB would be the equivalent of 10W power input, which into 8 ohms
(again, hah!) is (click, click) about 1.12A.
Anonymous
January 23, 2005 12:51:23 PM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote in message
news:WbOdnRRxWLU9fm_cRVn-vg@comcast.com...
> Howdy,
>
> I've a custom-built pair of LS3/5A's....I worked very hard to build them
> attractively and exactly to spec and it would be a shame for them to be
> accidentally blown up by one of my dumbass friends or by my own dumbass. I
> understand these speakers shouldn't be driven beyond about 90dB (I'm
> assuming that's SPL)....so I'd like to put a limiter on them after the
> power
> amp stage to hard limit the signal at a certain dBV ....I don't need any
> fancy compression or ADSR type functions, it doesn't even need to sound
> good
> when the limiter is ON as long as it's quiet when the limiter is OFF. What
> do ya'll recommend? The cheaper the better! Thanks!
>
> PS: power amp is an adcom 535II

I can't believe that nobody has mentioned the obvious solution: A PTC
thermistor in series with the speaker. Yes, the cold resistance has to be a
small fraction of the speaker resistance, and the thermal time constant has
to be less than that of the voice coil, but that shouldn't be much of a
problem.

Norm Strong
Anonymous
January 23, 2005 2:15:22 PM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango"

>
> I've a custom-built pair of LS3/5A's....I worked very hard to build them
> attractively and exactly to spec and it would be a shame for them to be
> accidentally blown up by one of my dumbass friends or by my own dumbass. I
> understand these speakers shouldn't be driven beyond about 90dB (I'm
> assuming that's SPL)....so I'd like to put a limiter on them after the
> power
> amp stage to hard limit the signal at a certain dBV ....I don't need any
> fancy compression or ADSR type functions, it doesn't even need to sound
> good
> when the limiter is ON as long as it's quiet when the limiter is OFF. What
> do ya'll recommend? The cheaper the better! Thanks!
>
> PS: power amp is an adcom 535II
>


** Light bulbs are well proven for this job.

Just put one or two 12 volt, 18 (CP) watt automotive tail/brake lights
bulbs wired in series with the speaker.





................. Phil
Anonymous
January 23, 2005 2:15:23 PM

Archived from groups: rec.audio.pro (More info?)

> Just put one or two 12 volt, 18 (CP) watt automotive tail/brake
> lights bulbs wired in series with the speaker.

That will make these speakers sound even more compressed than they already do.
Anonymous
January 23, 2005 2:38:28 PM

Archived from groups: rec.audio.pro (More info?)

It's sounds like I could use a combo of your thermistor and Bob Smith's SPL
meter to determine the max dBV I want travelling through the speakers and
then get a thermistor rated to about 110% of that value....

so just to clarify, these are the 15 ohm version of the LS3/5A's, using the
original B110A and T27A drivers....max wattage for ls3/5a's is 25W via 8
ohms ....i'm not sure what that translates into for the 15 ohm version

would you recommend seperate thermistors after the Xover stage for high and
low end drivers?

Also, these sound very similar to the "breakers" craig recommended

http://www.partsexpress.com/webpage.cfm?webpage_id=3&SO...
jectGroup_ID=568

Is the whole idea that thermistors have less resistance at normal levels?

Thanks a ton Norm I really appreciate the help!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



<normanstrong@comcast.net> wrote in message
news:9MmdnblBY7iHeW7cRVn-qA@comcast.com...
>
> "Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote in
message
> news:WbOdnRRxWLU9fm_cRVn-vg@comcast.com...
> > Howdy,
> >
> > I've a custom-built pair of LS3/5A's....I worked very hard to build them
> > attractively and exactly to spec and it would be a shame for them to be
> > accidentally blown up by one of my dumbass friends or by my own dumbass.
I
> > understand these speakers shouldn't be driven beyond about 90dB (I'm
> > assuming that's SPL)....so I'd like to put a limiter on them after the
> > power
> > amp stage to hard limit the signal at a certain dBV ....I don't need any
> > fancy compression or ADSR type functions, it doesn't even need to sound
> > good
> > when the limiter is ON as long as it's quiet when the limiter is OFF.
What
> > do ya'll recommend? The cheaper the better! Thanks!
> >
> > PS: power amp is an adcom 535II
>
> I can't believe that nobody has mentioned the obvious solution: A PTC
> thermistor in series with the speaker. Yes, the cold resistance has to be
a
> small fraction of the speaker resistance, and the thermal time constant
has
> to be less than that of the voice coil, but that shouldn't be much of a
> problem.
>
> Norm Strong
>
>
Anonymous
January 23, 2005 2:40:04 PM

Archived from groups: rec.audio.pro (More info?)

Do you know how these affect the impedence/resistance when the speakers are
driven to normal levels? Thanks Craig!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



"ceedub" <craigmw@EFOFFSPAMcox.net> wrote in message
news:lFDId.13350$nt.3327@fed1read06...
> > Howdy,
> >
> > I've a custom-built pair of LS3/5A's....I worked very hard to build them
> > attractively and exactly to spec and it would be a shame for them to be
> > accidentally blown up by one of my dumbass friends or by my own dumbass.
I
> > understand these speakers shouldn't be driven beyond about 90dB (I'm
> > assuming that's SPL)....so I'd like to put a limiter on them after the
> > power
> > amp stage to hard limit the signal at a certain dBV ....I don't need any
> > fancy compression or ADSR type functions, it doesn't even need to sound
> > good
> > when the limiter is ON as long as it's quiet when the limiter is OFF.
What
> > do ya'll recommend? The cheaper the better! Thanks!
> >
> > PS: power amp is an adcom 535II
> >
> > --
> >
> > Jonny Durango
>
> You will need to determine how many watts your speakers can conservatively
> handle. Then, pop one of these into the circuit (before the passive x-over
> or drivers):
>
>
http://www.partsexpress.com/webpage.cfm?webpage_id=3&SO...
jectGroup_ID=568
>
> Craig
>
>
Anonymous
January 23, 2005 2:49:49 PM

Archived from groups: rec.audio.pro (More info?)

> Ok, with a little trouble I found some impedance curves for two versions
of
> the LS3/5A. Both show 10 ohms at 250 Hz. Both show something above 25 ohms
> at 1 kHz, therefore 1 kHz would be not be an ideal frequency to infer a
max
> current by measuring the RMS voltage. 1 kHz appears to be near an
impedance
> peak (800 Hz and 900 Hz depending on version). I also found some specs
that
> referenced 95 dB SPL max, two speakers driven at a distance of two meters.
>
> bobs

I'm using the oldschool 15 ohm version w/ the original B110A and T27A
drivers and falcon 23T Xover....I checked out the impedance curves also (for
the 11-ohm version I think) and there are spikes all over the map. Would it
be best to determine max dBV and dB SPL using white noise? If not, what tone
would you recommend? Also, should I go with Norm's thermistor or Craig's
partsexpress breakers? Thanks a ton Bobs!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



"Bob Smith" <rsmith@1nospam2.bsstudios.com> wrote in message
news:hfOdnbnsAt6hlm7cRVn-jQ@comcast.com...
> "Bob Smith" <rsmith@1nospam2.bsstudios.com> wrote in message
> news:cpidnVAgVMwFZW_cRVn-vg@comcast.com...
> > "Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote:
> > >
> > > I've a custom-built pair of LS3/5A's....I worked very hard to build
them
> > > attractively and exactly to spec and it would be a shame for them to
be
> > > accidentally blown up by one of my dumbass friends or by my own
dumbass.
> I
> > > understand these speakers shouldn't be driven beyond about 90dB (I'm
> > > assuming that's SPL)
> >
> > Why not pick up an analog SPL meter from Radio Shack ($50) and find the
90
> > dB SPL point. Place the SPL meter one meter distance from one speaker
and
> > drive that speaker (other one muted) at a low volume with a 1 kHz sine.
> Turn
> > up the volume on the Adcom until the 90 dB point is reached. Note the
> > position on the Adcom and never turn it up past that point. Repeat the
> > procedure with the other speaker for a verification. If an AC RMS
> voltmeter
> > is available, measure the voltage across the speaker terminals at this
> > volume with the 1 kHz sine playing and use ohms law to infer the current
> > drawn, assuming 1 kHz wasn't at a complex impedance peak for the
speaker.
> > Then use an AGC fuse rated for 125% of the inferred current to avoid
> trouble
> > from momentary lapses of reason.
>
> Ok, with a little trouble I found some impedance curves for two versions
of
> the LS3/5A. Both show 10 ohms at 250 Hz. Both show something above 25 ohms
> at 1 kHz, therefore 1 kHz would be not be an ideal frequency to infer a
max
> current by measuring the RMS voltage. 1 kHz appears to be near an
impedance
> peak (800 Hz and 900 Hz depending on version). I also found some specs
that
> referenced 95 dB SPL max, two speakers driven at a distance of two meters.
>
> bobs
>
> Bob Smith
> BS Studios
> we organize chaos
> http://www.bsstudios.com
>
>
Anonymous
January 23, 2005 3:15:06 PM

Archived from groups: rec.audio.pro (More info?)

"Bob Smith"
>
> Why not pick up an analog SPL meter from Radio Shack ($50) and find the 90
> dB SPL point. Place the SPL meter one meter distance from one speaker and
> drive that speaker (other one muted) at a low volume with a 1 kHz sine.
> Turn
> up the volume on the Adcom until the 90 dB point is reached. Note the
> position on the Adcom and never turn it up past that point. Repeat the
> procedure with the other speaker for a verification.


** Errrr - what sort of twisted logic is behind this drivel ???




> If an AC RMS voltmeter
> is available, measure the voltage across the speaker terminals at this
> volume with the 1 kHz sine playing and use ohms law to infer the current
> drawn, assuming 1 kHz wasn't at a complex impedance peak for the speaker.


** 1kHz is close to an impedance peak.





............ Phil
Anonymous
January 23, 2005 3:15:07 PM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message news:35gc4sF4jhdbfU1@individual.net...
>
> "Bob Smith"
> >
> > Why not pick up an analog SPL meter from Radio Shack ($50) and find the 90
> > dB SPL point. Place the SPL meter one meter distance from one speaker and
> > drive that speaker (other one muted) at a low volume with a 1 kHz sine.
> > Turn up the volume on the Adcom until the 90 dB point is reached. Note the
> > position on the Adcom and never turn it up past that point. Repeat the
> > procedure with the other speaker for a verification.
>
>
> ** Errrr - what sort of twisted logic is behind this drivel ???


Better logic than changing light bulbs every 5 minutes.
Anonymous
January 23, 2005 6:39:16 PM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote in message
news:WbOdnRRxWLU9fm_cRVn-vg@comcast.com...
> I've a custom-built pair of LS3/5A's....I worked very hard to build them
> attractively and exactly to spec and it would be a shame for them to be
> accidentally blown up by one of my dumbass friends or by my own dumbass.

MANY manufacturers have attempted to find a way to do this and failed over
the years. Used within their limits, I think LS3/5As are among the best
sounding speakers ever designed but there's no free lunch and the limits
remain very real.

--
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
615.385.8051 http://www.hyperback.com
Anonymous
January 23, 2005 7:19:20 PM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote:
> > Ok, with a little trouble I found some impedance curves for two versions
of
> > the LS3/5A. Both show 10 ohms at 250 Hz. Both show something above 25
ohms
> > at 1 kHz, therefore 1 kHz would be not be an ideal frequency to infer a
max
> > current by measuring the RMS voltage. 1 kHz appears to be near an
impedance
> > peak (800 Hz and 900 Hz depending on version). I also found some specs
that
> > referenced 95 dB SPL max, two speakers driven at a distance of two
meters.
> >
> > bobs
>
> I'm using the oldschool 15 ohm version w/ the original B110A and T27A
> drivers and falcon 23T Xover....I checked out the impedance curves also
(for
> the 11-ohm version I think) and there are spikes all over the map. Would
it
> be best to determine max dBV and dB SPL using white noise? If not, what
tone
> would you recommend? Also, should I go with Norm's thermistor or Craig's
> partsexpress breakers? Thanks a ton Bobs!

The original BBC LS3/5 appears to be spec'd at 82 dB SPL /W/m. They also
suggested using an amplifier with no more than 50W max. A 15 ohm nominal
load at 50W would require 1.83A. I'd be inclined to use a 1.75 A AGC fuse to
be conservative as a starting point. I've never used either the thermistor
or breaker approach for speaker protection so I am not in a position to make
a recommendation for either. I'll leave that for folks more knowledgable
than I to discuss. I have used AGC fuses and try keep the I^2T of the fuse
lower than that of the speaker voice coils.

White noise is great for measuring circuits but I prefer pink noise for
speaker measurements when using an RTA. It's easier on both the tweeters and
my ears even with hearing protection. Pink noise would be good for SPL
measurements but I'd stick to sines for rms voltage measurements. It appears
that most of the versions of the LS3/5 are near nominal impedance around 250
Hz. For the 15 ohm version at 1W it should be approx 3.87 Vrms across the
speaker terminals. At 50W this should read approx 27 Vrms across the speaker
terminals.

Whatever you do, an inexpensive SPL meter with an analog display is a handy
item to have. Try setting up for an average SPL of 78 dB, 83 dB and 85 dB at
the listening position and hear how each feels. Also useful for walking the
room with a given frequency playing and see how the SPL corresponds to what
your ears are hearing, especially at single tones below 300 Hz in small
rooms as one walks between peaks and nulls of standing waves. Use one of the
room mode calculators available on the internet with a tape measure to
calculate the tones that will be useful in this experiment for your given
room.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com
Anonymous
January 23, 2005 7:51:56 PM

Archived from groups: rec.audio.pro (More info?)

"Bob Smith" <rsmith@1nospam2.bsstudios.com> wrote:

> The original BBC LS3/5 appears to be spec'd at 82 dB SPL /W/m. They also
> suggested using an amplifier with no more than 50W max. A 15 ohm nominal
> load at 50W would require 1.83A. I'd be inclined to use a 1.75 A AGC fuse
to
> be conservative as a starting point. I've never used either the thermistor
> or breaker approach for speaker protection so I am not in a position to
make
> a recommendation for either. I'll leave that for folks more knowledgable
> than I to discuss. I have used AGC fuses and try keep the I^2T of the fuse
> lower than that of the speaker voice coils.

Addendum. Just after hitting reply I found yet another site that shows an
impedance curve with the nominal minimum at 250Hz near 8 ohms, not 15. So
the figures above are off accordingly. 20Vrms across an 8 ohm load will be
50W. 2.83Vrms with same load will be 1W. I'd still be inclined to start
with a 1.75A fuse which would be approximately 25W and work up to 2A (32W)
and then maybe to 2.5A (50W) for 8 ohms.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com
January 23, 2005 10:12:26 PM

Archived from groups: rec.audio.pro (More info?)

> would you recommend seperate thermistors after the Xover stage for
high and
> low end drivers?
>
>

Yes!!!! whichever devices you decide to use (PTC, fuse, circuit
breaker, whatever) using one sized for the woofer and another one sized
for the tweeter will eliminate some of the compromises and will give
you much better protection and probably less coloration of the sound.
Mark
Anonymous
January 23, 2005 10:42:26 PM

Archived from groups: rec.audio.pro (More info?)

On Sun, 23 Jan 2005 12:15:06 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"Bob Smith"
>>
>> Why not pick up an analog SPL meter from Radio Shack ($50) and find the 90
>> dB SPL point. Place the SPL meter one meter distance from one speaker and
>> drive that speaker (other one muted) at a low volume with a 1 kHz sine.
>> Turn
>> up the volume on the Adcom until the 90 dB point is reached. Note the
>> position on the Adcom and never turn it up past that point. Repeat the
>> procedure with the other speaker for a verification.
>
>
>** Errrr - what sort of twisted logic is behind this drivel ???
>
>

THX mixing rooms have one level. Period. It's not at all out of line
to find a level and stick to it.

Like many professionals, actual working engineers prefer not to put
more circuitry (often the lowest common denominator) in the signal
chain just to protect speakers. High standards and all that.

Some idiots actually would go so far as to put automotive lights in
the signal path!!!! HAH!!! Can you believe it? That was discounted
decades ago as introducing distortion and was never a credible
solution. Man, some people.

Well, at least you're not that stupid.



Kurt Riemann
Anonymous
January 23, 2005 11:50:52 PM

Archived from groups: rec.audio.pro (More info?)

"Mark" <makolber@yahoo.com> wrote in message
news:1106536346.048883.227120@z14g2000cwz.googlegroups.com...
>
>
> > would you recommend seperate thermistors after the Xover stage for
> high and
> > low end drivers?
> >
> >
>
> Yes!!!! whichever devices you decide to use (PTC, fuse, circuit
> breaker, whatever) using one sized for the woofer and another one sized
> for the tweeter will eliminate some of the compromises and will give
> you much better protection and probably less coloration of the sound.
> Mark

I agree with Mark. This is a better solution. A protective device for each
driver instead of one to cover everything. Tweeters typically have a lower
power rating than woofers.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com
Anonymous
January 24, 2005 12:06:25 AM

Archived from groups: rec.audio.pro (More info?)

"David Morgan (MAMS)"
>
> "Phil Allison"
>
>> "Bob Smith"
>> >
>> > Why not pick up an analog SPL meter from Radio Shack ($50) and find the
>> > 90
>> > dB SPL point. Place the SPL meter one meter distance from one speaker
>> > and
>> > drive that speaker (other one muted) at a low volume with a 1 kHz sine.
>> > Turn up the volume on the Adcom until the 90 dB point is reached. Note
>> > the
>> > position on the Adcom and never turn it up past that point. Repeat the
>> > procedure with the other speaker for a verification.
>>
>>
>> ** Errrr - what sort of twisted logic is behind this drivel ???
>
>
> Better logic than changing light bulbs every 5 minutes.
>


** In that case your "logic" is even more fatally flawed than Bob's.

Folk with nothing to say best say nothing - David.




........... Phil
Anonymous
January 24, 2005 12:10:56 AM

Archived from groups: rec.audio.pro (More info?)

"William Sommerwerck"
>> Just put one or two 12 volt, 18 (CP) watt automotive tail/brake
>> lights bulbs wired in series with the speaker.
>
> That will make these speakers sound even more compressed than they already
> do.



** At very high volumes, sure - but not permit destruction.




............... Phil
Anonymous
January 24, 2005 8:26:41 AM

Archived from groups: rec.audio.pro (More info?)

I think the original poster is way off-base.

Brief, high-level bursts of signal are not usually sufficient to damage a
speaker (unless they push the suspension to the point of damage, which is
exteremely uncommon). There is little or no need to protect electrodynamic
speakers from high-level transients. (Electrostatic speakers are another
matter.)

Speaker damage is almost always the result of overheating, caused by sustained
playback at an excessively high level. A fuse is a perfectly satisfactory way to
protect the speaker from this sort of damage, because the fuse fails in much the
same way the speaker fails.

Classical and jazz listeners rarely damage their speakers. It's rock listeners,
who crank up the volume without paying attention to the high levels of
distortion, who burn out the drivers. (If I had time, I'd tell you Mike Wright's
stories about having to keep the power-handling capacity of his speakers ahead
of rock listeners.) So...

I would suggest that the original poster simply stick a 1A fast-blow fuse in the
speaker line, and live with it for a while. If turning up the volume blows the
fuse _before_ the speaker audibly distorts, the fuse is too small.

PS: When I worked at Barclay Recording & Electronics, we sold speakers made by
Transduction, Ltd. One of them was their version of the Rogers LS3/5a, using the
same KEF drivers in a larger cabinet . It was superior to the Rogers in every
way, except for a slight midrange "boxiness". On one occasion I drove them with
the Audio Research D-400, a huge solid-state amplifier. During one very loud
passage, the output power meter on the amp kicked all the way into the red, but
the Transduction speakers handled the power with aplomb and without being
damaged. Those drivers can handle quite a bit of power; you don't need to worry
(much) about the LS3/5a being damaged.
Anonymous
January 24, 2005 9:09:43 AM

Archived from groups: rec.audio.pro (More info?)

<Kurt Riemann> wrote in message
news:r9u8v0l9blv0ig9ehn9q288n60dug4pugu@4ax.com...
> THX mixing rooms have one level. Period. It's not at all out of line
> to find a level and stick to it.

Not out of line if you are mixing at the same level that it is going to be
played back in a theater.

If you are mixing music for the home, boombox or car, it's a really good
idea to KNOW what it's going to sound like at lots of different levels.

--
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
615.385.8051 http://www.hyperback.com
Anonymous
January 24, 2005 11:46:20 AM

Archived from groups: rec.audio.pro (More info?)

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10v9tsssi43p9c8@corp.supernews.com

> I would suggest that the original poster simply stick a 1A fast-blow
> fuse in the speaker line, and live with it for a while. If turning up
> the volume blows the fuse _before_ the speaker audibly distorts, the
> fuse is too small.

FWIW, this has been essentially my approach.

I favor separate fuses for each driver.

My paradigm for fuse-sizing is pick something I think is probably too small
(say 1 amp for tweeters, 3 amps for woofers), and then increase the size of
the fuse in logical steps as it blows in more-or-less normal use, until I
decide that the fuse blew in a situation that I think is *exceptional*.

This paradigm has "personal judgement" written all over it. The decision
about what constitutes *exceptional* has a lot of subjectivity in it,
perhaps. OTOH, many exceptional cases are pretty clear with 20-20 hindsight.
For example, plugging and unplugging cables with the power on. Listening
loud while, err... ...distracted. Obviously dumb stuff, but stuff happens.
The blown fuse enables the hindsight-based decision to be made and acted on
quickly and cheaply, instead of having to first fix the blown speaker.

This approach got me through three teenaged sons. Two of them also had their
own systems that were not so carefully protected. They blew their speakers,
left and right. One does so to this day. The speakers involved were cheap
when they were new. IMO, no great loss. It's now on his nickel, not mine.
That's a choice he gets to make! ;-)
Anonymous
January 24, 2005 12:31:03 PM

Archived from groups: rec.audio.pro (More info?)

In article <LqmdnVBoqNamlmncRVn-oQ@comcast.com> jonnybush_from_officedurango1@comcast.net writes:

> It's sounds like I could use a combo of your thermistor and Bob Smith's SPL
> meter to determine the max dBV I want travelling through the speakers and
> then get a thermistor rated to about 110% of that value....

Honestly, if you're going to all that trouble, you're probably going
to run them dangerously close to the limit too often. Determine when
they're getting close to blowing, get a sense of how loud that is, and
just don't turn them up any louder. If it's not quite loud enough for
you, get some other monitors and don't try to push the little LS3/5As.
Either your protection will fail at some time or you'll discover that
it wasn't adequate.



--
I'm really Mike Rivers - (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
January 24, 2005 2:15:19 PM

Archived from groups: rec.audio.pro (More info?)

I doubt they'd change the impedance by much. I'm not sure how these work;
they are either a standard fuse, or more likely, they have a bimetal contact
strip. As the former heats up due to too much current, it burns out. This
small wire will impose its own resistance, but I doubt very much since it's
so short. The latter works by differential expansion of the two metals in
the bimetal contact. When this happens, the contact moves away from its
connection, breaking the circuit. I'd bet these work this way. If this is
the case, I doubt they have any significant effect on the resistance in the
circuit. However, they have a potential problem in that contacts can oxidize
over time, possibly leading to some distortion. But, I doubt that would be
much of a problem either.

Craig

--


---------------------------------------------------------------------
"Are you still wasting your time with spam?...
There is a solution!"

Protected by GIANT Company's Spam Inspector
The most powerful anti-spam software available.
http://mail.spaminspector.com


"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote in message
news:EPednTjNc454kGncRVn-tQ@comcast.com...
> Do you know how these affect the impedence/resistance when the speakers
> are
> driven to normal levels? Thanks Craig!
>
> --
>
> Jonny Durango
>
> "Patrick was a saint. I ain't."
>
> http://www.jdurango.com
>
>
>
> "ceedub" <craigmw@EFOFFSPAMcox.net> wrote in message
> news:lFDId.13350$nt.3327@fed1read06...
>> > Howdy,
>> >
>> > I've a custom-built pair of LS3/5A's....I worked very hard to build
>> > them
>> > attractively and exactly to spec and it would be a shame for them to be
>> > accidentally blown up by one of my dumbass friends or by my own
>> > dumbass.
> I
>> > understand these speakers shouldn't be driven beyond about 90dB (I'm
>> > assuming that's SPL)....so I'd like to put a limiter on them after the
>> > power
>> > amp stage to hard limit the signal at a certain dBV ....I don't need
>> > any
>> > fancy compression or ADSR type functions, it doesn't even need to sound
>> > good
>> > when the limiter is ON as long as it's quiet when the limiter is OFF.
> What
>> > do ya'll recommend? The cheaper the better! Thanks!
>> >
>> > PS: power amp is an adcom 535II
>> >
>> > --
>> >
>> > Jonny Durango
>>
>> You will need to determine how many watts your speakers can
>> conservatively
>> handle. Then, pop one of these into the circuit (before the passive
>> x-over
>> or drivers):
>>
>>
> http://www.partsexpress.com/webpage.cfm?webpage_id=3&SO...
> jectGroup_ID=568
>>
>> Craig
>>
>>
>
>
Anonymous
January 24, 2005 2:26:00 PM

Archived from groups: rec.audio.pro (More info?)

normanstrong@comcast.net
>
> I can't believe that nobody has mentioned the obvious solution: A PTC
> thermistor in series with the speaker. Yes, the cold resistance has to be
> a small fraction of the speaker resistance, and the thermal time constant
> has to be less than that of the voice coil, but that shouldn't be much of
> a problem.
>


** Problems with PTCs include finding the right one for the job, the
strict voltage limitation when in high impedance mode and not least the fact
that sound stops completely when they trip.






............. Phil
Anonymous
January 24, 2005 2:55:41 PM

Archived from groups: rec.audio.pro (More info?)

On Mon, 24 Jan 2005 06:09:43 GMT, "Bob Olhsson" <olh@hyperback.com>
wrote:

><Kurt Riemann> wrote in message
>news:r9u8v0l9blv0ig9ehn9q288n60dug4pugu@4ax.com...
> > THX mixing rooms have one level. Period. It's not at all out of line
>> to find a level and stick to it.
>
>Not out of line if you are mixing at the same level that it is going to be
>played back in a theater.
>
>If you are mixing music for the home, boombox or car, it's a really good
>idea to KNOW what it's going to sound like at lots of different levels.

True.




Kurt Riemann
Anonymous
January 24, 2005 4:34:42 PM

Archived from groups: rec.audio.pro (More info?)

"Actually, fusing can colour the sound slightly. The fuse is more than
just
a conductor. Since it is designed to melt at it's maximum rating, and
on
loud passages, that maximum rating is theoretically approached, the
temperature of the fuse element will vary (taking into account its
thermal
lag) with the envelope of the signal.

Since the resistance of most metals goes up as they are heated, this
becomes a variable resistor that is program dependent in series with
the
speaker. To some small extent, this would compress the signal coming
out of
the speaker. As the signal got louder (overall) the temperature and
resistance of the fuse would go up and looking at the fuse and the
speaker
as a voltage divider, the percentage of the signal at the speaker
terminals
would go down."

dale
Anonymous
January 24, 2005 8:54:02 PM

Archived from groups: rec.audio.pro (More info?)

Hey Bob I can't thank you enough....this technical electronics stuff tends
to escape me so the help is GREATLY appreciated. I think I'll try both the
1.75A fuses and thermistors (they are both cheap, what the hell) and find
the best performing and perhaps more important the best sounding solution. I
usually like to monitor at 80-85dB so I might try some 1.85A +/-
fuses/thermistors also. Again, the help is greatly appreciated!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



"Bob Smith" <rsmith@1nospam2.bsstudios.com> wrote in message
news:zfSdnT5v9v4g22ncRVn-rg@comcast.com...
> "Bob Smith" <rsmith@1nospam2.bsstudios.com> wrote:
>
> > The original BBC LS3/5 appears to be spec'd at 82 dB SPL /W/m. They also
> > suggested using an amplifier with no more than 50W max. A 15 ohm nominal
> > load at 50W would require 1.83A. I'd be inclined to use a 1.75 A AGC
fuse
> to
> > be conservative as a starting point. I've never used either the
thermistor
> > or breaker approach for speaker protection so I am not in a position to
> make
> > a recommendation for either. I'll leave that for folks more knowledgable
> > than I to discuss. I have used AGC fuses and try keep the I^2T of the
fuse
> > lower than that of the speaker voice coils.
>
> Addendum. Just after hitting reply I found yet another site that shows an
> impedance curve with the nominal minimum at 250Hz near 8 ohms, not 15. So
> the figures above are off accordingly. 20Vrms across an 8 ohm load will be
> 50W. 2.83Vrms with same load will be 1W. I'd still be inclined to start
> with a 1.75A fuse which would be approximately 25W and work up to 2A
(32W)
> and then maybe to 2.5A (50W) for 8 ohms.
>
> bobs
>
> Bob Smith
> BS Studios
> we organize chaos
> http://www.bsstudios.com
>
>
Anonymous
January 24, 2005 8:58:44 PM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1106530985k@trad...
>
> In article <LqmdnVBoqNamlmncRVn-oQ@comcast.com>
jonnybush_from_officedurango1@comcast.net writes:
>
> > It's sounds like I could use a combo of your thermistor and Bob Smith's
SPL
> > meter to determine the max dBV I want travelling through the speakers
and
> > then get a thermistor rated to about 110% of that value....
>
> Honestly, if you're going to all that trouble, you're probably going
> to run them dangerously close to the limit too often. Determine when
> they're getting close to blowing, get a sense of how loud that is, and
> just don't turn them up any louder. If it's not quite loud enough for
> you, get some other monitors and don't try to push the little LS3/5As.
> Either your protection will fail at some time or you'll discover that
> it wasn't adequate.

Indeed, for those nights of drunken partying, perhaps a pair of cheap,
raucous and hard-to-blow speakers is in order. After a couple of beers, you
don't notice the difference anyway.

Peace,
Paul
Anonymous
January 24, 2005 9:32:09 PM

Archived from groups: rec.audio.pro (More info?)

"Paul Stamler" <pstamlerhell@pobox.com> wrote in message
news:o HaJd.20672$8u5.1398@bgtnsc04-news.ops.worldnet.att.net...
>
> "Mike Rivers" <mrivers@d-and-d.com> wrote in message
> news:znr1106530985k@trad...
> >
> > In article <LqmdnVBoqNamlmncRVn-oQ@comcast.com>
> jonnybush_from_officedurango1@comcast.net writes:
> >
> > > It's sounds like I could use a combo of your thermistor and Bob
Smith's
> SPL
> > > meter to determine the max dBV I want travelling through the speakers
> and
> > > then get a thermistor rated to about 110% of that value....
> >
> > Honestly, if you're going to all that trouble, you're probably going
> > to run them dangerously close to the limit too often. Determine when
> > they're getting close to blowing, get a sense of how loud that is, and
> > just don't turn them up any louder. If it's not quite loud enough for
> > you, get some other monitors and don't try to push the little LS3/5As.
> > Either your protection will fail at some time or you'll discover that
> > it wasn't adequate.
>
> Indeed, for those nights of drunken partying, perhaps a pair of cheap,
> raucous and hard-to-blow speakers is in order. After a couple of beers,
you
> don't notice the difference anyway.
>
> Peace,
> Paul
>
>

True...but it's not so much the partying I'm worried about as it is the
accidental DEAFENING feedback loop or volume spike at some point in the
signal path....you know what I mean, these anomolies happen to the best of
us =)

Jonny Durango
Anonymous
January 24, 2005 9:34:55 PM

Archived from groups: rec.audio.pro (More info?)

> speaker. To some small extent, this would compress the signal coming
> out of
> the speaker. As the signal got louder (overall) the temperature and
> resistance of the fuse would go up and looking at the fuse and the
> speaker
> as a voltage divider, the percentage of the signal at the speaker
> terminals
> would go down."

True, but again, if I can find thermistors with the proper value, then they
shouldn't start to affect the impedence until they get close to dangerous
levels, which is the whole point....Either I won't notice the difference in
sound, in which case, great, or I will notice it and it will serve as a
warning that I'm overdriving the speakers...either way, great....I shouldn't
be driving them past 85dB SPL (as a pair) anyhow...I've asked some ppl on
the LS3/5A yahoo group for some safe level recommendations, so I'll just get
thermistors to match their recommendations and expiriment around w/ the
values. Thanks a ton for the input, it's been a great help!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



"dale" <dallen@frognet.net> wrote in message
news:1106602482.924767.216470@z14g2000cwz.googlegroups.com...
> "Actually, fusing can colour the sound slightly. The fuse is more than
> just
> a conductor. Since it is designed to melt at it's maximum rating, and
> on
> loud passages, that maximum rating is theoretically approached, the
> temperature of the fuse element will vary (taking into account its
> thermal
> lag) with the envelope of the signal.
>
> Since the resistance of most metals goes up as they are heated, this
> becomes a variable resistor that is program dependent in series with
> the
> speaker. To some small extent, this would compress the signal coming
> out of
> the speaker. As the signal got louder (overall) the temperature and
> resistance of the fuse would go up and looking at the fuse and the
> speaker
> as a voltage divider, the percentage of the signal at the speaker
> terminals
> would go down."
>
> dale
>
Anonymous
January 25, 2005 4:43:15 AM

Archived from groups: rec.audio.pro (More info?)

Jonny Durango wrote:

> On second thought, why not wire fuses in between the power amp and the
> drivers/crossovers? What value/type of fuse would I use? Thanks!

There are issues with fuses like their resistance and thermal modulation of
same. Not advised for a decent monitor speaker.

Graham
Anonymous
January 25, 2005 4:52:15 AM

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> normanstrong@comcast.net
> >
> > I can't believe that nobody has mentioned the obvious solution: A PTC
> > thermistor in series with the speaker. Yes, the cold resistance has to be
> > a small fraction of the speaker resistance, and the thermal time constant
> > has to be less than that of the voice coil, but that shouldn't be much of
> > a problem.
> >
>
> ** Problems with PTCs include finding the right one for the job, the
> strict voltage limitation when in high impedance mode and not least the fact
> that sound stops completely when they trip.
>
> ............ Phil

The typical application note for Polyswitch PTCs from Raychem suggests an R in
parallel to limit the attenuation.

I don't know how much ( if any ) better they sound than series fuses or bulbs (
parallel R often helps here too ) with their thermal resistance modulation
issues.


Graham
Anonymous
January 25, 2005 7:52:54 AM

Archived from groups: rec.audio.pro (More info?)

Jonny Durango wrote:

> Hey Bob I can't thank you enough....this technical electronics stuff tends
> to escape me so the help is GREATLY appreciated. I think I'll try both the
> 1.75A fuses and thermistors (they are both cheap, what the hell) and find
> the best performing and perhaps more important the best sounding solution.

I know this is might not be a little over-complicated, but if sonic
transparency is the goal, what about building some kind of device
that would monitor the line-level inputs to the power amp and then
just switch a relay (on the power amp's outputs) if things get out
of control? You could isolate this circuit from the amp's inputs
with a line-level amplifier. As for how to trigger the relay, I'm
thinking something simple like a light bulb and a photoresistor
in series with the relay's coil. Or just use a noise gate, set
the threshold really high, and put the relay on its outputs. (This
is where I'm overstepping my knowledge of electronics greatly, but
maybe you need to convert whatever powers the relay's coil to
smoothe DC first.)

Yours in electronic ignorance...

- Logan
Anonymous
January 25, 2005 11:04:54 AM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote in message
news:yoadnWUZqfHyIGjcRVn-iQ@comcast.com...

> > Indeed, for those nights of drunken partying, perhaps a pair of cheap,
> > raucous and hard-to-blow speakers is in order. After a couple of beers,
> you
> > don't notice the difference anyway.
> >
> > Peace,
> > Paul
> >
> >
>
> True...but it's not so much the partying I'm worried about as it is the
> accidental DEAFENING feedback loop or volume spike at some point in the
> signal path....you know what I mean, these anomolies happen to the best of
> us =)

Indeed, they do. That's why my 3/5a's are powered by a Dynaco Stereo 70
which is almost as old as I am. They run off the 4 ohm taps (cleaner bass),
and on a good day the Dyna puts out about 20W max in that hookup. Safe.
Course I don't listen real loud.

Peace,
Paul
Anonymous
January 25, 2005 4:33:11 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear"
>
> Jonny Durango wrote:
>
>> On second thought, why not wire fuses in between the power amp and the
>> drivers/crossovers? What value/type of fuse would I use? Thanks!
>
> There are issues with fuses like their resistance and thermal modulation
> of
> same. Not advised for a decent monitor speaker.
>


** Bullshit- what a liar Pooh face is.




............... Phil
Anonymous
January 25, 2005 4:36:18 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear"

>>
>> ** Problems with PTCs include finding the right one for the job, the
>> strict voltage limitation when in high impedance mode and not least the
>> fact
>> that sound stops completely when they trip.
>
> The typical application note for Polyswitch PTCs from Raychem suggests an
> R in
> parallel to limit the attenuation.
>
> I don't know how much ( if any ) better they sound than series fuses or
> bulbs (
> parallel R often helps here too ) with their thermal resistance modulation
> issues.
>


** There is no modulation issue with using a fuse.




................. Phil
Anonymous
January 26, 2005 2:17:10 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear wrote:
> Phil Allison wrote:
>
>
>>"Pooh Bear"
>>
>>
>>>>** Problems with PTCs include finding the right one for the job, the
>>>>strict voltage limitation when in high impedance mode and not least the
>>>>fact
>>>>that sound stops completely when they trip.
>>>
>>>The typical application note for Polyswitch PTCs from Raychem suggests an
>>>R in
>>>parallel to limit the attenuation.
>>>
>>>I don't know how much ( if any ) better they sound than series fuses or
>>>bulbs (
>>>parallel R often helps here too ) with their thermal resistance modulation
>>>issues.
>>
>>
>> ** There is no modulation issue with using a fuse.
>>
>>................ Phil
>
>
> Fuses are somehow immune to the effects of the thermal coefficient of resistance
> of the fuse wire and I^2R heating effects ?

A better question is if it could be audible to the human ear? If not,
then there is no modulation issue, as Phil said.
Anonymous
January 26, 2005 6:10:27 AM

Archived from groups: rec.audio.pro (More info?)

> Fuses are somehow immune to the effects of the thermal
> coefficient of resistance of the fuse wire and I^2R heating effects?

I don't know if the modulation of the fuse resistance is audible, but note that
the fuse on Hafler amplifiers was inside the feedback loop.
Anonymous
January 26, 2005 6:11:22 AM

Archived from groups: rec.audio.pro (More info?)

> A 1.6 amp fuse has only 1 or 2 % of the resistance of an 8 ohm driver -
> even when operated at rated current - so NO audible effect on output level.

That isn't the issue. It's IM distortion.
Anonymous
January 26, 2005 7:17:29 AM

Archived from groups: rec.audio.pro (More info?)

Bob Smith wrote:

> "Mark" <makolber@yahoo.com> wrote in message
> news:1106536346.048883.227120@z14g2000cwz.googlegroups.com...
> >
> >
> > > would you recommend seperate thermistors after the Xover stage for
> > high and
> > > low end drivers?
> > >
> > >
> >
> > Yes!!!! whichever devices you decide to use (PTC, fuse, circuit
> > breaker, whatever) using one sized for the woofer and another one sized
> > for the tweeter will eliminate some of the compromises and will give
> > you much better protection and probably less coloration of the sound.
> > Mark
>
> I agree with Mark. This is a better solution. A protective device for each
> driver instead of one to cover everything. Tweeters typically have a lower
> power rating than woofers.

If you want to use fuses, separate fuses, appropriately rated for each driver,
is the only solution that makes sense.

Count me in too !


Graham
Anonymous
January 26, 2005 12:57:11 PM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>Fuses are somehow immune to the effects of the thermal coefficient of resistance
>of the fuse wire and I^2R heating effects ?

No, but they are a lot more immune than some of the alternatives, like light
bulbs and Polyfuses.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!