4 Apr
2005
4 Apr
'05
11:23 a.m.
Hi all,
Is there a chance that signals generated from software could damage live PA
equipment? I'm guessing not, as there is obviously (I assume) some limiting
built into soundcards, but I'm just wondering what applications do to, if
anything, to help.
It's just something that worries me sometimes when playing live, and
generating particually nasty noises by accident, or design :)
cheers,
dave
4 Apr
4 Apr
11:42 a.m.
Is there a chance that signals generated from software
could damage live PA
equipment? I'm guessing not, as there is obviously (I assume) some limiting
built into soundcards, but I'm just wondering what applications do to, if
anything, to help.
soundcards generally don't put out anything but line-level signals
and/or digital i/o. neither is capable, by itself, of hurting
anything, and it certainly won't power a PA. that job falls to the
amps that take the line level and boost it. if the amp can destroy the
PA, the it can do so with or without the help of the soundcard :)
--p
11:56 a.m.
On Monday 04 April 2005 15:18, Dave Griffiths wrote:
Is there a chance that signals generated from software
could damage live PA
equipment? I'm guessing not, as there is obviously (I assume) some limiting
built into soundcards, but I'm just wondering what applications do to, if
anything, to help.
Its the same noises as in analog-equipment. For ruining the speakers you need
a square wave, the longer the square, the better. The involved
high-frequencies might be to much for the high-freq-speaker as normaly the
signal-amount in this part isn't the same as in the lower parts so
speaker-manufactures don't have to make them to powerfull to get the label
200W sticked on them.
And a real constant value outputted from your self-made-synthesizers will kill
the bass-box...
How to do that in analog? Feedbacks and plugging a battery on the box or
getting a voltage-shift into your equipment...
If this is not correct, please correct me,
Arnold
--
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Universe is for and why it is here, it will instantly disappear and be
replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.
-- Douglas Adams, The Restaurant at the End of the Universe
12:16 p.m.
Hi,
possibly you can inadvertently add a DC-offset in your signal, which
(depending on the soundcard, I guess) could reach your PA unfiltered.
This then can put your speakers in a constant offset-state, limiting
your dynamic range and possibly hurting it.
A simple highpass filter, set to a rather low frequency will rid you of
any DC-offset.
sincerely,
Marije
Dave Griffiths wrote:
Hi all,
Is there a chance that signals generated from software could damage live PA
equipment? I'm guessing not, as there is obviously (I assume) some limiting
built into soundcards, but I'm just wondering what applications do to, if
anything, to help.
It's just something that worries me sometimes when playing live, and
generating particually nasty noises by accident, or design :)
cheers,
dave
1:12 p.m.
I think the main problem that can occur from DC offset is overheating of
the amp, and then heat protection turns the amp of....
A hi pass filter as said is usually the solution.
You also need to check your dynamic range carefully to avoid blowing
people's ears... (thinks sound very differently on the studio than on
the stage regarding dynamic range.)
Andres
On Mon, 2005-04-04 at 09:11, Marije Baalman wrote:
Hi,
possibly you can inadvertently add a DC-offset in your signal, which
(depending on the soundcard, I guess) could reach your PA unfiltered.
This then can put your speakers in a constant offset-state, limiting
your dynamic range and possibly hurting it.
A simple highpass filter, set to a rather low frequency will rid you of
any DC-offset.
sincerely,
Marije
Dave Griffiths wrote:
Hi all,
Is there a chance that signals generated from software could damage live PA
equipment? I'm guessing not, as there is obviously (I assume) some limiting
built into soundcards, but I'm just wondering what applications do to, if
anything, to help.
It's just something that worries me sometimes when playing live, and
generating particually nasty noises by accident, or design :)
cheers,
dave
2:01 p.m.
Andres Cabrera wrote:
I think the main problem that can occur from DC offset
is overheating of
the amp, and then heat protection turns the amp of....
Overheating of the amp is nonsense. Most amplifiers operate in class A
or AB anyway, and maybe in class D. Heat dissipation is independant of
the input signal for these amps. The types that might build up a problem
with heat (e.g. class H) aren't used in PA enviroments. And before the
amp overheats, your speakers will be dead.
The biggest problem regarding DC offset (and clipping) is the fact that
speakers are not made to cope with DC signals. They heat up very quickly
under DC load, and on top of that there is no air movement in the
speaker itself to cool it somehow (athough this last effect isn't that
important).
the following links provide quite some info regarding distortion,
clipping and DC offsets:
http://sound.westhost.com/clipping.htm
http://sound.westhost.com/tweeters.htm
The remark regarding the dynamic range is right though: the only time I
ever seen a blown up PA speaker was due to the dynamic range of the
music involved. It started with a very silent intro of a minute or so,
but then it contained a full-scale bassdrum. Nice to get a 'surprise'
effect, and probably nice in a silent studio enviroment with moderate
listening levels. But in a live situation there is a lot of enviroment
noise, which tempts the PA engineer to crank up the volume on silent
intro's so that the people are able to hear them. You can guess what
happens once the bass drum kicks in. Even when using a limiter this can
destroy speakers, because of its attack time. It's also not very healthy
for the public.
My recommendations:
- Be sure to do a decent sound-check: have a full-scale piece of music
ready for the PA engineer to set the PA desk incoming level, and be sure
not to change your volume when soundcheck is done.
- Adapt the dynamic range of your music to the live enviroment, e.g. by
using a compressor plugin just before the soundcard output.
Greets,
Pieter
3 p.m.
On Mon, 04 Apr 2005 18:01:02 +0200, Pieter Palmers wrote
the following links provide quite some info regarding
distortion,
clipping and DC offsets:
http://sound.westhost.com/clipping.htm
http://sound.westhost.com/tweeters.htm
interesting articles
My recommendations:
- Be sure to do a decent sound-check: have a full-scale piece of
music ready for the PA engineer to set the PA desk incoming level,
and be sure not to change your volume when soundcheck is done. -
Adapt the dynamic range of your music to the live enviroment, e.g.
by using a compressor plugin just before the soundcard output.
so it isn't so much of a software problem, but rather the responsibility of
the artist to keep the dynamic range down, and the sound engineer to set the
levels sensibly?
it's interesting though, as a lot of performers who use computers eschew the
soundcheck these days, thinking just a line test, or just plugging in and
setting the volume, is enough.
so, would it be a good idea to purchase a small compressor, if using homemade
analogue synths, or even software capable of producing nasty signals?
cheers,
dave
3:45 p.m.
On Mon, Apr 04, 2005 at 05:55:12PM +0100, Dave Griffiths wrote:
On Mon, 04 Apr 2005 18:01:02 +0200, Pieter Palmers
wrote
A compressor might not be fast or hard enough to buy you much safety.
For that, better would be a good fast limiter and a subsonic filter.
The filter is pretty easy and cheap (see e.g. the Harrison Labs Fmod),
but I don't happen to know of a really good inexpensive brick-wall
limiter first-hand. I've heard that the Aphex Dominator isn't bad, but
it's hardly cheap. Maybe one of the DBX models? *shrug*
If I owned a venue or rented a sound system I'd probably provide my own
anyway, but I don't know how many do that.
--
Paul Winkler
http://www.slinkp.com
the following links provide quite some info
regarding distortion,
clipping and DC offsets:
http://sound.westhost.com/clipping.htm
http://sound.westhost.com/tweeters.htm
interesting articles
My recommendations:
- Be sure to do a decent sound-check: have a full-scale piece of
music ready for the PA engineer to set the PA desk incoming level,
and be sure not to change your volume when soundcheck is done. -
Adapt the dynamic range of your music to the live enviroment, e.g.
by using a compressor plugin just before the soundcard output.
so it isn't so much of a software problem, but rather the responsibility of
the artist to keep the dynamic range down, and the sound engineer to set the
levels sensibly?
it's interesting though, as a lot of performers who use computers eschew the
soundcheck these days, thinking just a line test, or just plugging in and
setting the volume, is enough.
so, would it be a good idea to purchase a small compressor, if using homemade
analogue synths, or even software capable of producing nasty signals?
4:38 p.m.
Paul Winkler wrote:
On Mon, Apr 04, 2005 at 05:55:12PM +0100, Dave
Griffiths wrote:
Behringer offers an active crossover with limiters on each band +
subsonic filter (CX3400), at a very nice price (€150).
The only drawback is that it isn't a real brickwall limiter, the system
behind this limiter still has to be able to cope with signals that are
+6dB higher than the 'limit'.
On Mon, 04 Apr 2005 18:01:02 +0200, Pieter Palmers
wrote
A compressor might not be fast or hard enough to buy you much safety.
For that, better would be a good fast limiter and a subsonic filter.
The filter is pretty easy and cheap (see e.g. the Harrison Labs Fmod),
but I don't happen to know of a really good inexpensive brick-wall
limiter first-hand. I've heard that the Aphex Dominator isn't bad, but
it's hardly cheap. Maybe one of the DBX models? *shrug*
the following links provide quite some info
regarding distortion,
clipping and DC offsets:
http://sound.westhost.com/clipping.htm
http://sound.westhost.com/tweeters.htm
interesting articles
My recommendations:
- Be sure to do a decent sound-check: have a full-scale piece of
music ready for the PA engineer to set the PA desk incoming level,
and be sure not to change your volume when soundcheck is done. -
Adapt the dynamic range of your music to the live enviroment, e.g.
by using a compressor plugin just before the soundcard output.
so it isn't so much of a software problem, but rather the responsibility of
the artist to keep the dynamic range down, and the sound engineer to set the
levels sensibly?
it's interesting though, as a lot of performers who use computers eschew the
soundcheck these days, thinking just a line test, or just plugging in and
setting the volume, is enough.
so, would it be a good idea to purchase a small compressor, if using homemade
analogue synths, or even software capable of producing nasty signals?
If I owned a venue or rented a sound system I'd
probably provide my own
anyway, but I don't know how many do that.
All PA companies I've worked with have limiters installed, especially
the rental companies. Most of the time they are installed in the same
flightcase as the amps, and sometimes they are integrated into a
'speaker management' device.
Pieter
4:49 p.m.
Dave Griffiths wrote:
On Mon, 04 Apr 2005 18:01:02 +0200, Pieter Palmers
wrote
Indeed. But the sound engineer can't do miracles. The problem with
computer music is that the engineer has very little knobs to turn. It's
all coming in on one channel, so no freedom at all.
I, as a hobby-PA engineer, have the impression that a lot of computer
musicians don't realize that live work is different from studio work.
But maybe it's the same way around for studio engineers and live bands?
Also in some musical genres the gap between live and studio is larger
than in others.
the following links provide quite some info
regarding distortion,
clipping and DC offsets:
http://sound.westhost.com/clipping.htm
http://sound.westhost.com/tweeters.htm
interesting articles
My recommendations:
- Be sure to do a decent sound-check: have a full-scale piece of
music ready for the PA engineer to set the PA desk incoming level,
and be sure not to change your volume when soundcheck is done. -
Adapt the dynamic range of your music to the live enviroment, e.g.
by using a compressor plugin just before the soundcard output.
so it isn't so much of a software problem, but rather the responsibility of
the artist to keep the dynamic range down, and the sound engineer to set the
levels sensibly?
it's interesting though, as a lot of performers who
use computers eschew the
soundcheck these days, thinking just a line test, or just plugging in and
setting the volume, is enough.
That was the case at the gig I was talking about.
Basically the soundcheck is a lot easier for a computer (almost no
freedom), but it stays important to set the levels right.
so, would it be a good idea to purchase a small
compressor, if using homemade
analogue synths, or even software capable of producing nasty signals?
If you're using homemade analog synths, I would recommend the use of
decent filters (a subsonic for <25Hz and a lowpass for >20kHz) after
this synth. Maybe the easiest solution would be to put an equaliser
behind it. They tend to incorporate both a subsonic and a lowpass filter
on top of their graphic eq.
But for me the bottom line is: if the sound kills PA speakers, it will
certainly damage your ears. So be carefull what you're doing.
Pieter
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linux-audio-dev@lists.linuxaudio.org
9 comments
7 participants
participants (7)
-
Andres Cabrera -
Arnold Krille -
Dave Griffiths -
Marije Baalman -
Paul Davis -
Paul Winkler -
Pieter Palmers