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Crossover efficiency - passive vs active.

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Anonymous
April 25, 2004 4:01:06 PM

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

Hi,

I'm been wondering about this for a few days and hopefully someone can here
can help me out.

Just from a theoretical point of view, I'm interested in the difference
between active and passive crossovers.

I know that active crossover will produce a better sounding, more controlled
and efficient setup but todate I only know this from experience.

I'm assuming 2 things...

The lower current levels in an active device mean that there is less wastage
due to heating etc.

The lower current means that better quality components can be used as the
cost in trying to keep them running at high currents ceases to apply.

I'd like to know if there is anymore to it and if anyone could estimate how
much power a passive crossover is losing?

Thanks
John P.



efficiency?

--
www.lemon-grass.net
Anonymous
April 25, 2004 6:56:03 PM

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

"John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
news:Hzydne9Uao61BxbdSa8jmA@karoo.co.uk...
> Hi,
>
> I'm been wondering about this for a few days and hopefully someone can
here
> can help me out.
>
> Just from a theoretical point of view, I'm interested in the difference
> between active and passive crossovers.
>
> I know that active crossover will produce a better sounding, more
controlled
> and efficient setup but todate I only know this from experience.

That's not necessarily true. with a passive crossover, you can compensate
for some effects that an active one can't come close to rectifying.

>
> I'm assuming 2 things...
>
> The lower current levels in an active device mean that there is less
wastage
> due to heating etc.

AND low voltages. Active crossovers are based on line levels where there is
next to no power involved - just signals.
BUT you have to have twice the number of amplifiers which means that you
will have up to twice the wasted power when running it on zero volume

>
> The lower current means that better quality components can be used as the
> cost in trying to keep them running at high currents ceases to apply.

Here you're barking up entirely the wrong tree. If anything, the passive
crossover wins here because there is no further distortion or noise added
into the circuit by using discreet components.

>
> I'd like to know if there is anymore to it and if anyone could estimate
how
> much power a passive crossover is losing?

I think you're on about the total amount of power converted to sound (a
quantity) as opposed to efficiency ( a ratio).
How a passive crossover works is it takes the voltage amplifier output and
presents it with a varying impedance over frequency - thus drawing far less
current at higher frequencies (in a low pass) hence - the amplifier also
draws less current at higher frequencies. Your only loss in the active
crossover is in the DC resistance of the inductors and in the current passed
to earth in higher order crossovers.

Take a look at this:
http://sound.westhost.com/tweeters.htm
It shows you how typically the power and frequency distribution is divided.
It also tells you that you've only 20% of the power (and voltage) above
1.6kHz for example - meaning you can actually use an amplifier with 1/4 the
power rating for above this frequency - but at much higher gain (since the
ac component above that frequency is also much lower)


John, I think you're taking drivers to be a lot more linear than they
actually are and working with hypotheses that are also flawed say with
respect to driver impedances being constant and there being no compensation
needed for impedance variations (look at Zobel networks for instance). There
is nothing such as a perfect listening environment, perfect speaker, perfect
crossover or perfect amp although some components do get quite close. It's
never the speakers mind you - that's where most of the compromises are -
elsewhere it's just bad design that gets in the way...


cb
Anonymous
April 25, 2004 6:56:04 PM

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

"Chris Berry" <christoforos@Notmail.com> wrote in message
news:c6gcf1$nd4$03$1@news.t-online.com...
>
> "John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
> news:Hzydne9Uao61BxbdSa8jmA@karoo.co.uk...
> > Hi,
> >
> > Just from a theoretical point of view, I'm interested in the difference
> > between active and passive crossovers.
> >

> I think you're on about the total amount of power converted to sound (a
> quantity) as opposed to efficiency ( a ratio).
> How a passive crossover works is it takes the voltage amplifier output and
> presents it with a varying impedance over frequency - thus drawing far
less
> current at higher frequencies (in a low pass) hence - the amplifier also
> draws less current at higher frequencies. Your only loss in the active
> crossover is in the DC resistance of the inductors and in the current
passed
> to earth in higher order crossovers.


Yes sorry if I wasn't clear by efficiency I'm thinking about total system
amplifier watts converted into SPL. I'm used to talking about energy
transfer in terms of ratio but I suppose it would be cool to just use SPL dB
per watt.

>
> Take a look at this:
> http://sound.westhost.com/tweeters.htm
> It shows you how typically the power and frequency distribution is
divided.
> It also tells you that you've only 20% of the power (and voltage) above
> 1.6kHz for example - meaning you can actually use an amplifier with 1/4
the
> power rating for above this frequency - but at much higher gain (since the
> ac component above that frequency is also much lower)
>

Thanks for the link, I'm familiar with the variations in power required
across the frequency range, I should have been a bit more clear...

If you consider the total system for example 2 speakers high and low how
much variation in total amp power would be needed to get the same spl using
active or passive.
e.g a 100W amp might have the signal split using a passive crossover so the
20W goes to the tops and 80W goes to the bass. (the amount going to each
speaker will be less due to losses in the crossover)
If the same speakers were driven using a 20W amp and an 80W amp, would the
SPL big significantly different because in this case there won't be as much
power wasted?

This is the difference I'm trying to discover.

Thanks again
John P.
Related resources
Anonymous
April 25, 2004 8:16:47 PM

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

"John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
news:D zWdnem3lvX_JxbdSa8jmA@karoo.co.uk...
>
> "Chris Berry" <christoforos@Notmail.com> wrote in message
> news:c6gcf1$nd4$03$1@news.t-online.com...
> >
> > "John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
> > news:Hzydne9Uao61BxbdSa8jmA@karoo.co.uk...
> > > Hi,
> > >
> > > Just from a theoretical point of view, I'm interested in the
difference
> > > between active and passive crossovers.
> > >
>
> > I think you're on about the total amount of power converted to sound (a
> > quantity) as opposed to efficiency ( a ratio).
> > How a passive crossover works is it takes the voltage amplifier output
and
> > presents it with a varying impedance over frequency - thus drawing far
> less
> > current at higher frequencies (in a low pass) hence - the amplifier also
> > draws less current at higher frequencies. Your only loss in the active
> > crossover is in the DC resistance of the inductors and in the current
> passed
> > to earth in higher order crossovers.
>
>
> Yes sorry if I wasn't clear by efficiency I'm thinking about total system
> amplifier watts converted into SPL. I'm used to talking about energy
> transfer in terms of ratio but I suppose it would be cool to just use SPL
dB
> per watt.

You're voltage limited - not power limited - so it also depends on the
program.
I think the bigger difference between the 2 systems would be ripple not
affecting high frequency reproduction.
An active crossover can clear that up AND have beneficial effects on phase.

>
> >
> > Take a look at this:
> > http://sound.westhost.com/tweeters.htm
> > It shows you how typically the power and frequency distribution is
> divided.
> > It also tells you that you've only 20% of the power (and voltage) above
> > 1.6kHz for example - meaning you can actually use an amplifier with 1/4
> the
> > power rating for above this frequency - but at much higher gain (since
the
> > ac component above that frequency is also much lower)
> >
>
> Thanks for the link, I'm familiar with the variations in power required
> across the frequency range, I should have been a bit more clear...
>
> If you consider the total system for example 2 speakers high and low how
> much variation in total amp power would be needed to get the same spl
using
> active or passive.
> e.g a 100W amp might have the signal split using a passive crossover so
the
> 20W goes to the tops and 80W goes to the bass. (the amount going to each
> speaker will be less due to losses in the crossover)
> If the same speakers were driven using a 20W amp and an 80W amp, would the
> SPL big significantly different because in this case there won't be as
much
> power wasted?

Maybe 10% or so - you wouldn't be able to hear the difference...


>
> This is the difference I'm trying to discover.

The thing is - what are you trying to do? or argue?
cb
Anonymous
April 25, 2004 8:16:48 PM

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

"Chris Berry" <christoforos@Notmail.com> wrote in message
news:c6gh6d$ruk$03$1@news.t-online.com...
>
> "John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
> news:D zWdnem3lvX_JxbdSa8jmA@karoo.co.uk...
> >
> > "Chris Berry" <christoforos@Notmail.com> wrote in message
> > news:c6gcf1$nd4$03$1@news.t-online.com...
> > >
> > > "John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
> > > news:Hzydne9Uao61BxbdSa8jmA@karoo.co.uk...
> > > > Hi,
> > > >
> > > > Just from a theoretical point of view, I'm interested in the
> difference
> > > > between active and passive crossovers.
> > > >
> >
> > > I think you're on about the total amount of power converted to sound
(a
> > > quantity) as opposed to efficiency ( a ratio).
> > > How a passive crossover works is it takes the voltage amplifier output
> and
> > > presents it with a varying impedance over frequency - thus drawing far
> > less
> > > current at higher frequencies (in a low pass) hence - the amplifier
also
> > > draws less current at higher frequencies. Your only loss in the active
> > > crossover is in the DC resistance of the inductors and in the current
> > passed
> > > to earth in higher order crossovers.
> >
> >
> > Yes sorry if I wasn't clear by efficiency I'm thinking about total
system
> > amplifier watts converted into SPL. I'm used to talking about energy
> > transfer in terms of ratio but I suppose it would be cool to just use
SPL
> dB
> > per watt.
>
> You're voltage limited - not power limited - so it also depends on the
> program.
> I think the bigger difference between the 2 systems would be ripple not
> affecting high frequency reproduction.
> An active crossover can clear that up AND have beneficial effects on
phase.
>
> >
> > >
> > > Take a look at this:
> > > http://sound.westhost.com/tweeters.htm
> > > It shows you how typically the power and frequency distribution is
> > divided.
> > > It also tells you that you've only 20% of the power (and voltage)
above
> > > 1.6kHz for example - meaning you can actually use an amplifier with
1/4
> > the
> > > power rating for above this frequency - but at much higher gain (since
> the
> > > ac component above that frequency is also much lower)
> > >
> >
> > Thanks for the link, I'm familiar with the variations in power required
> > across the frequency range, I should have been a bit more clear...
> >
> > If you consider the total system for example 2 speakers high and low how
> > much variation in total amp power would be needed to get the same spl
> using
> > active or passive.
> > e.g a 100W amp might have the signal split using a passive crossover so
> the
> > 20W goes to the tops and 80W goes to the bass. (the amount going to each
> > speaker will be less due to losses in the crossover)
> > If the same speakers were driven using a 20W amp and an 80W amp, would
the
> > SPL big significantly different because in this case there won't be as
> much
> > power wasted?
>
> Maybe 10% or so - you wouldn't be able to hear the difference...
>
>
> >
> > This is the difference I'm trying to discover.
>
> The thing is - what are you trying to do? or argue?
> cb
>
>

Hi Chris,

10% - I thought it might be higher than that, but I'm happy to go along with
the need for active units in terms of better signal control.

I'm not really intending to do anything, I just wondered if there was an
issue relating to passive crossover wasting power due to the nature of the
signal they are dealing with compared to the lower levels running through
active units.
I'm curious about things I guess.

Thanks again

John P.
Anonymous
April 25, 2004 9:01:10 PM

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

"John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
news:ezudne4vf_tYTRbdSa8jmw@karoo.co.uk...
>
> "Chris Berry" <christoforos@Notmail.com> wrote in message
> news:c6gh6d$ruk$03$1@news.t-online.com...
> >
> > "John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
> > news:D zWdnem3lvX_JxbdSa8jmA@karoo.co.uk...
> > >
> > > "Chris Berry" <christoforos@Notmail.com> wrote in message
> > > news:c6gcf1$nd4$03$1@news.t-online.com...
> > > >
> > > > "John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message
> > > > news:Hzydne9Uao61BxbdSa8jmA@karoo.co.uk...
> > > > > Hi,
> > > > >
> > > > > Just from a theoretical point of view, I'm interested in the
> > difference
> > > > > between active and passive crossovers.
> > > > >
> > >
> > > > I think you're on about the total amount of power converted to sound
> (a
> > > > quantity) as opposed to efficiency ( a ratio).
> > > > How a passive crossover works is it takes the voltage amplifier
output
> > and
> > > > presents it with a varying impedance over frequency - thus drawing
far
> > > less
> > > > current at higher frequencies (in a low pass) hence - the amplifier
> also
> > > > draws less current at higher frequencies. Your only loss in the
active
> > > > crossover is in the DC resistance of the inductors and in the
current
> > > passed
> > > > to earth in higher order crossovers.
> > >
> > >
> > > Yes sorry if I wasn't clear by efficiency I'm thinking about total
> system
> > > amplifier watts converted into SPL. I'm used to talking about energy
> > > transfer in terms of ratio but I suppose it would be cool to just use
> SPL
> > dB
> > > per watt.
> >
> > You're voltage limited - not power limited - so it also depends on the
> > program.
> > I think the bigger difference between the 2 systems would be ripple not
> > affecting high frequency reproduction.
> > An active crossover can clear that up AND have beneficial effects on
> phase.
> >
> > >
> > > >
> > > > Take a look at this:
> > > > http://sound.westhost.com/tweeters.htm
> > > > It shows you how typically the power and frequency distribution is
> > > divided.
> > > > It also tells you that you've only 20% of the power (and voltage)
> above
> > > > 1.6kHz for example - meaning you can actually use an amplifier with
> 1/4
> > > the
> > > > power rating for above this frequency - but at much higher gain
(since
> > the
> > > > ac component above that frequency is also much lower)
> > > >
> > >
> > > Thanks for the link, I'm familiar with the variations in power
required
> > > across the frequency range, I should have been a bit more clear...
> > >
> > > If you consider the total system for example 2 speakers high and low
how
> > > much variation in total amp power would be needed to get the same spl
> > using
> > > active or passive.
> > > e.g a 100W amp might have the signal split using a passive crossover
so
> > the
> > > 20W goes to the tops and 80W goes to the bass. (the amount going to
each
> > > speaker will be less due to losses in the crossover)
> > > If the same speakers were driven using a 20W amp and an 80W amp, would
> the
> > > SPL big significantly different because in this case there won't be as
> > much
> > > power wasted?
> >
> > Maybe 10% or so - you wouldn't be able to hear the difference...
> >
> >
> > >
> > > This is the difference I'm trying to discover.
> >
> > The thing is - what are you trying to do? or argue?
> > cb
> >
> >
>
> Hi Chris,
>
> 10% - I thought it might be higher than that, but I'm happy to go along
with
> the need for active units in terms of better signal control.

With better control (such as phase control) also goes the user's ability to
use the things...

>
> I'm not really intending to do anything, I just wondered if there was an
> issue relating to passive crossover wasting power due to the nature of the
> signal they are dealing with compared to the lower levels running through
> active units.
> I'm curious about things I guess.

Know what curiosity did to the cat?
just kidding...
cb
Anonymous
April 25, 2004 9:06:30 PM

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

"John P" <pinchin@notthispinchin.karoo.co.uk> skrev i en meddelelse
news:Hzydne9Uao61BxbdSa8jmA@karoo.co.uk...
> Hi,
>
> I'm been wondering about this for a few days and hopefully someone can
here
> can help me out.
>
> Just from a theoretical point of view, I'm interested in the difference
> between active and passive crossovers.
>
> I know that active crossover will produce a better sounding, more
controlled
> and efficient setup but todate I only know this from experience.
>
> I'm assuming 2 things...
>
> The lower current levels in an active device mean that there is less
wastage
> due to heating etc.
>
> The lower current means that better quality components can be used as the
> cost in trying to keep them running at high currents ceases to apply.
>
> I'd like to know if there is anymore to it and if anyone could estimate
how
> much power a passive crossover is losing?
>
> Thanks
> John P.
>
>
>
> efficiency?
>
> --
> www.lemon-grass.net
>
> Alan.T.wrote:
Surely the major advantage of the active crossover is that the
crossover frequencies remain constant ,regardless of voice coil temperature
and the resulting change in impedance.
Alan.
atls2004@mail.dk (remove year)


---
Outgoing mail is certified Virus Free.
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Anonymous
April 25, 2004 11:15:32 PM

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

> Hi,
>
> I'm been wondering about this for a few days and hopefully someone can
here
> can help me out.
>
> Just from a theoretical point of view, I'm interested in the difference
> between active and passive crossovers.
>
> I know that active crossover will produce a better sounding, more
controlled
> and efficient setup but todate I only know this from experience.
>
> I'm assuming 2 things...
>
> The lower current levels in an active device mean that there is less
wastage
> due to heating etc.
>
> The lower current means that better quality components can be used as the
> cost in trying to keep them running at high currents ceases to apply.
>
> I'd like to know if there is anymore to it and if anyone could estimate
how
> much power a passive crossover is losing?

John, I understand your question, but it's a tough matter to quantify.

First of all, passive crossovers can be used for both preamp level signals
and speaker level signals. I presume you're referring strictly to the
latter.

Anyway, the amount of loss passive crossovers exhibit is a function of
several factors: crossover alignment and slope (which together sort of
specify the degree of overlap between the two pass-bands), whether or not
there are resistive circuits incorporated (L-pads or zobel networks, for
instance) and driver impedance. A rough estimate can probably be obtained
from that power distribution plot already referenced. The estimate is rough
because it doesn't take into account any of the things I listed above and it
also depends greatly on program material (and, IMO, the plot itself isn't
all that indicative of true power distributions, especially when you take
into account things like crest factor as a function of frequency).
Anonymous
April 26, 2004 11:31:54 AM

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

"John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message news:<Hzydne9Uao61BxbdSa8jmA@karoo.co.uk>...
> Hi,
>
> I'm been wondering about this for a few days and hopefully someone can here
> can help me out.
>
> Just from a theoretical point of view, I'm interested in the difference
> between active and passive crossovers.
>
> I know that active crossover will produce a better sounding, more controlled
> and efficient setup but todate I only know this from experience.
>
> I'm assuming 2 things...
>
> The lower current levels in an active device mean that there is less wastage
> due to heating etc.
>
> The lower current means that better quality components can be used as the
> cost in trying to keep them running at high currents ceases to apply.
>
> I'd like to know if there is anymore to it and if anyone could estimate how
> much power a passive crossover is losing?
>
> Thanks
> John P.
>
>
>
> efficiency?

This is what I've heard (I run active filters myself):

Active - positive:

- Less power needed, simpler power amps, less possibility of clipping
artefacts
- Stable impedance seen by the filter
- Less impact of voice coil temperature and filters - bigger advantage
if complex filters
- Often adjustable levels of tweet/midrange. Good if cross-over is set
properly. Can be used to adjust for some room acoustics (bright/dull
room)

Active - negative:

- More power amps = more expensive
- Often less protection of tweeters (DC)
- Lower distortion possible with passive filters, often with tweeters
(impedance matching). Can be done actively also, but needs
impedance-matched outputs of power amp. Sometimes a resistor in series
with the tweet may reduce impedance-related distortion, but will also
change fr resp. Colloms says something about this in his loudspeaker
book. Have too little knowledge to say how much it will affect.

T
Anonymous
April 26, 2004 12:18:49 PM

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

John P wrote:

> I'd like to know if there is anymore to it and if anyone could
> estimate how much power a passive crossover is losing?

That varies quite a bit. For example, tweeters in systems with passive
crossovers are as a rule, more efficient than the woofers they are used
with. Efficiency matching is traditionally accomplished with attenuators
that are associated with the tweeters.. In these cases, power en route to
the tweeter MUST be wasted in order to produce flat frequency response.

A few speakers have been built that use tapped transformers to reduce the
power delivered to the upper-range drivers. This could reduce the amount of
power being wasted that way.

There's no doubt that active crossovers minimize actual power loss, other
than then power they themselves use.
Anonymous
April 26, 2004 1:55:26 PM

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

John P wrote:

> Hi,
>
> I'm been wondering about this for a few days and hopefully someone can here
> can help me out.
>
> Just from a theoretical point of view, I'm interested in the difference
> between active and passive crossovers.
>
> I know that active crossover will produce a better sounding, more controlled
> and efficient setup but todate I only know this from experience.

This is exacly my experience as well.

> I'm assuming 2 things...
>
> The lower current levels in an active device mean that there is less wastage
> due to heating etc.

Well, there are no losses at all with an active filter - that is - if we
are talking about loss of power between the power amp and the speaker
driver(s). Since there are no components between the amp and the speaker
when you use an active filter, the only possible loss is in the speaker
cable, which should be close to nothing.

A passive crossover needs to loose a lot of power, because the network
must equalize the frequency reponse as well as just crossing over. A
typical mid/woofer driver has a frequency reponse that rises several dB
from the bass (~100 Hz) and up through the midrange.

> The lower current means that better quality components can be used as the
> cost in trying to keep them running at high currents ceases to apply.

> I'd like to know if there is anymore to it and if anyone could estimate how
> much power a passive crossover is losing?

It depends a lot on the application!

An example: a typical small two-way speaker needs to drop the midrange 6
dB to obtain a flat response. That's 75% power loss.

Regards,
Stig Erik Tangen
Anonymous
April 26, 2004 1:55:27 PM

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

Or to say it more simply -- all of the power not transmitted through the Low
Pass or High Pass section of a passive filter is dissipated into the
atmosphere as heat.

Of course, most active (non FDNR) crossovers use feedback ...

"Stig Erik Tangen" <stigerik@newsguy.com> wrote in message
news:Mf3jc.226$Yc.2320@news4.e.nsc.no...
> John P wrote:
>
> > Hi,
> >
> > I'm been wondering about this for a few days and hopefully someone can
here
> > can help me out.
> >
> > Just from a theoretical point of view, I'm interested in the difference
> > between active and passive crossovers.
> >
> > I know that active crossover will produce a better sounding, more
controlled
> > and efficient setup but todate I only know this from experience.
>
> This is exacly my experience as well.
>
> > I'm assuming 2 things...
> >
> > The lower current levels in an active device mean that there is less
wastage
> > due to heating etc.
>
> Well, there are no losses at all with an active filter - that is - if we
> are talking about loss of power between the power amp and the speaker
> driver(s). Since there are no components between the amp and the speaker
> when you use an active filter, the only possible loss is in the speaker
> cable, which should be close to nothing.
>
> A passive crossover needs to loose a lot of power, because the network
> must equalize the frequency reponse as well as just crossing over. A
> typical mid/woofer driver has a frequency reponse that rises several dB
> from the bass (~100 Hz) and up through the midrange.
>
> > The lower current means that better quality components can be used as
the
> > cost in trying to keep them running at high currents ceases to apply.
>
> > I'd like to know if there is anymore to it and if anyone could estimate
how
> > much power a passive crossover is losing?
>
> It depends a lot on the application!
>
> An example: a typical small two-way speaker needs to drop the midrange 6
> dB to obtain a flat response. That's 75% power loss.
>
> Regards,
> Stig Erik Tangen
>
Anonymous
April 26, 2004 1:55:28 PM

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

> Or to say it more simply -- all of the power not transmitted through the
Low
> Pass or High Pass section of a passive filter is dissipated into the
> atmosphere as heat.

Well, no. Power output is further attenuated by the increase in impedance
associated with introducing a passive crossover. The bulk of this is
reactive, not a matter of heat dissipation.
Anonymous
April 26, 2004 2:02:49 PM

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

Chris Berry wrote:
> That's not necessarily true. with a passive crossover, you can compensate
> for some effects that an active one can't come close to rectifying.

Such as?

> Here you're barking up entirely the wrong tree. If anything, the passive
> crossover wins here because there is no further distortion or noise added
> into the circuit by using discreet components.

Yes there is. An iron-cored coil may add several percent of harmonic
distortion.

Regards,
Stig Erik Tangen
Anonymous
April 26, 2004 2:02:50 PM

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

Depends upon the material you choose for the core AND the
application/current.

> Yes there is. An iron-cored coil may add several percent of harmonic
> distortion.
>
> Regards,
> Stig Erik Tangen
>
Anonymous
April 26, 2004 5:30:23 PM

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

"Stig Erik Tangen" <stigerik@newsguy.com> wrote in message
news:Hm3jc.229$Yc.2313@news4.e.nsc.no...
> Chris Berry wrote:
> > That's not necessarily true. with a passive crossover, you can
compensate
> > for some effects that an active one can't come close to rectifying.
>
> Such as?

Zobel?

>
> > Here you're barking up entirely the wrong tree. If anything, the passive
> > crossover wins here because there is no further distortion or noise
added
> > into the circuit by using discreet components.
>
> Yes there is. An iron-cored coil may add several percent of harmonic
> distortion.

No-one's forcing you to use iron or ferrite cores. I don't.
cb
Anonymous
April 26, 2004 5:30:49 PM

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

Or you could use air-core coils to eliminate that particular problem
(and potensially introduce some new problems...)

Stig Erik Tangen

John Walton wrote:

> Depends upon the material you choose for the core AND the
> application/current.
>
>
>>Yes there is. An iron-cored coil may add several percent of harmonic
>>distortion.
>>
>>Regards,
>>Stig Erik Tangen
>>
>
>
>
Anonymous
April 26, 2004 5:44:22 PM

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

Chris Berry wrote:
> Zobel?

Usually a Zobel network is used at the amp output to protect the amp
against difficult capacitive loads. This has nothing at all to do with
the speaker crossover. Some do use a Zobel to equalize the impedance of
the speaker, to make it easier to design a passive crossover. With an
active crossover you dont need a flat speaker impedance.

> No-one's forcing you to use iron or ferrite cores. I don't.

I know... I never use them, but they are very common even in high-end
speakers. There is no way around ferrite cores if you want a small and
cheap 10 mH inductor. with low DCR.

Stig Erik Tangen
April 27, 2004 6:56:19 PM

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

On 26 Apr 2004 07:31:54 -0700, Thomas_Akerlund@hotmail.com (Thomas A) wrote:

>"John P" <pinchin@notthispinchin.karoo.co.uk> wrote in message news:<Hzydne9Uao61BxbdSa8jmA@karoo.co.uk>...
>> Hi,
>>
>> I'm been wondering about this for a few days and hopefully someone can here
>> can help me out.
>>
>> Just from a theoretical point of view, I'm interested in the difference
>> between active and passive crossovers.
>>
>> I know that active crossover will produce a better sounding, more controlled
>> and efficient setup but todate I only know this from experience.
>>
>> I'm assuming 2 things...
>>
>> The lower current levels in an active device mean that there is less wastage
>> due to heating etc.
>>
>> The lower current means that better quality components can be used as the
>> cost in trying to keep them running at high currents ceases to apply.
>>
>> I'd like to know if there is anymore to it and if anyone could estimate how
>> much power a passive crossover is losing?
>>
>> Thanks
>> John P.
>>
>>
>>
>> efficiency?
>
>This is what I've heard (I run active filters myself):
>
>Active - positive:
>
>- Less power needed, simpler power amps, less possibility of clipping
>artefacts
>- Stable impedance seen by the filter
>- Less impact of voice coil temperature and filters - bigger advantage
>if complex filters
>- Often adjustable levels of tweet/midrange. Good if cross-over is set
>properly. Can be used to adjust for some room acoustics (bright/dull
>room)
>
>Active - negative:
>
>- More power amps = more expensive
>- Often less protection of tweeters (DC)
>- Lower distortion possible with passive filters, often with tweeters
>(impedance matching). Can be done actively also, but needs
>impedance-matched outputs of power amp. Sometimes a resistor in series
>with the tweet may reduce impedance-related distortion, but will also
>change fr resp. Colloms says something about this in his loudspeaker
>book. Have too little knowledge to say how much it will affect.
>
>T

All agreed, but while "often less protection of tweeters (DC)" is true, there's
more to it. Even with an active xover it's a good idea to isolate the tweeter by
a cap to protect it against DC amp faults. And all tweeters need protective
devices anyway (polyswitch, PTC, lamp, etc). But at least with an active xover
you can size the power amps reasonably (eg 1kW for sub, 500+500 for mid-bass,
100+100 for horns), whereas with a passive xover even a 1000+1000W amp won't
give the same output or clarity, and someone waving a mic in front of the FOH
can take out the horn drivers very quickly.

I'll have to follow up on the reduction of distortion by impedance matching -
I've never heard that before, and it sounds counter-intuitive.

Tony (remove the "_" to reply by email)
Anonymous
April 27, 2004 6:56:20 PM

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

much snipped...


> >
> >This is what I've heard (I run active filters myself):
> >
> >Active - positive:
> >
> >- Less power needed, simpler power amps, less possibility of clipping
> >artefacts
> >- Stable impedance seen by the filter
> >- Less impact of voice coil temperature and filters - bigger advantage
> >if complex filters
> >- Often adjustable levels of tweet/midrange. Good if cross-over is set
> >properly. Can be used to adjust for some room acoustics (bright/dull
> >room)
> >
> >Active - negative:
> >
> >- More power amps = more expensive
> >- Often less protection of tweeters (DC)
> >- Lower distortion possible with passive filters, often with tweeters
> >(impedance matching). Can be done actively also, but needs
> >impedance-matched outputs of power amp. Sometimes a resistor in series
> >with the tweet may reduce impedance-related distortion, but will also
> >change fr resp. Colloms says something about this in his loudspeaker
> >book. Have too little knowledge to say how much it will affect.
> >
> >T
>
> All agreed, but while "often less protection of tweeters (DC)" is true, there's
> more to it. Even with an active xover it's a good idea to isolate the tweeter by
> a cap to protect it against DC amp faults. And all tweeters need protective
> devices anyway (polyswitch, PTC, lamp, etc). But at least with an active xover
> you can size the power amps reasonably (eg 1kW for sub, 500+500 for mid-bass,
> 100+100 for horns), whereas with a passive xover even a 1000+1000W amp won't
> give the same output or clarity, and someone waving a mic in front of the FOH
> can take out the horn drivers very quickly.
>
> I'll have to follow up on the reduction of distortion by impedance matching -
> I've never heard that before, and it sounds counter-intuitive.

There is a chapter which I read in the Colloms "High Performance
Loudspeakers" book, and I've been talking to some other people about
this. It is possible to reduce distorsion by some kind of impedance
matched output (going from voltage to more current drive?). I'm sure
there are people here that can explain it better than me.

T

>
> Tony (remove the "_" to reply by email)
Anonymous
April 27, 2004 6:56:21 PM

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

"Thomas A" <Thomas_Akerlund@hotmail.com> wrote in message
news:9a6b3d08.0404270255.3fa0ff6d@posting.google.com...
> much snipped...
>
>
> > >
> > >This is what I've heard (I run active filters myself):
> > >
> > >Active - positive:
> > >
> > >- Less power needed, simpler power amps, less possibility of clipping
> > >artefacts
> > >- Stable impedance seen by the filter
> > >- Less impact of voice coil temperature and filters - bigger advantage
> > >if complex filters
> > >- Often adjustable levels of tweet/midrange. Good if cross-over is set
> > >properly. Can be used to adjust for some room acoustics (bright/dull
> > >room)
> > >
> > >Active - negative:
> > >
> > >- More power amps = more expensive
> > >- Often less protection of tweeters (DC)
> > >- Lower distortion possible with passive filters, often with tweeters
> > >(impedance matching). Can be done actively also, but needs
> > >impedance-matched outputs of power amp. Sometimes a resistor in series
> > >with the tweet may reduce impedance-related distortion, but will also
> > >change fr resp. Colloms says something about this in his loudspeaker
> > >book. Have too little knowledge to say how much it will affect.
> > >
> > >T
> >
> > All agreed, but while "often less protection of tweeters (DC)" is true,
there's
> > more to it. Even with an active xover it's a good idea to isolate the
tweeter by
> > a cap to protect it against DC amp faults. And all tweeters need
protective
> > devices anyway (polyswitch, PTC, lamp, etc). But at least with an active
xover
> > you can size the power amps reasonably (eg 1kW for sub, 500+500 for
mid-bass,
> > 100+100 for horns), whereas with a passive xover even a 1000+1000W amp
won't
> > give the same output or clarity, and someone waving a mic in front of
the FOH
> > can take out the horn drivers very quickly.
> >
> > I'll have to follow up on the reduction of distortion by impedance
matching -
> > I've never heard that before, and it sounds counter-intuitive.
>
> There is a chapter which I read in the Colloms "High Performance
> Loudspeakers" book, and I've been talking to some other people about
> this. It is possible to reduce distorsion by some kind of impedance
> matched output (going from voltage to more current drive?). I'm sure
> there are people here that can explain it better than me.
>

I think you're on to Zobel networks there.
Look it up and see if it's what you're looking for.
cb
Anonymous
April 27, 2004 6:56:21 PM

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

Thomas A wrote:

> much snipped...
>>>- Lower distortion possible with passive filters, often with tweeters
>>>(impedance matching). Can be done actively also, but needs
>>>impedance-matched outputs of power amp. Sometimes a resistor in series
>>>with the tweet may reduce impedance-related distortion, but will also
>>>change fr resp. Colloms says something about this in his loudspeaker
>>>book. Have too little knowledge to say how much it will affect.
> There is a chapter which I read in the Colloms "High Performance
> Loudspeakers" book, and I've been talking to some other people about
> this. It is possible to reduce distorsion by some kind of impedance
> matched output (going from voltage to more current drive?). I'm sure
> there are people here that can explain it better than me.

Current drive is equal to using an amplifier with infinite output
impedance. There are no problems using this in combination with active
crossovers.

Putting a resistor in series with the drivers is NOT equal to current drive.

Stig Erik Tangen
Anonymous
April 27, 2004 6:56:22 PM

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

Stig Erik Tangen <stigerik@newsguy.com> wrote in message news:<iLrjc.394$Yc.5479@news4.e.nsc.no>...
> Thomas A wrote:
>
> > much snipped...
> >>>- Lower distortion possible with passive filters, often with tweeters
> >>>(impedance matching). Can be done actively also, but needs
> >>>impedance-matched outputs of power amp. Sometimes a resistor in series
> >>>with the tweet may reduce impedance-related distortion, but will also
> >>>change fr resp. Colloms says something about this in his loudspeaker
> >>>book. Have too little knowledge to say how much it will affect.
> > There is a chapter which I read in the Colloms "High Performance
> > Loudspeakers" book, and I've been talking to some other people about
> > this. It is possible to reduce distorsion by some kind of impedance
> > matched output (going from voltage to more current drive?). I'm sure
> > there are people here that can explain it better than me.
>
> Current drive is equal to using an amplifier with infinite output
> impedance. There are no problems using this in combination with active
> crossovers.

Yes, agree.

>
> Putting a resistor in series with the drivers is NOT equal to current drive.

But can it reduce distortion?

T
>
> Stig Erik Tangen
Anonymous
April 28, 2004 2:19:26 AM

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

Thomas A wrote:
>>Putting a resistor in series with the drivers is NOT equal to current drive.
>
>
> But can it reduce distortion?

Current drive will eliminate the power compression caused by heating of
the voice coil. A (small) resistor will not. *IF* you use a resistor in
series to simulate current drive (or more corrrectly; a transconductance
amplifier), the resistor value must be much larger than the speaker's
impedance; Colloms suggets 100 times or more.

Stig Erik
!