Is it an international convention, for all time, that if short duration plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N_Cook wrote:
Is it an international convention, for all time, that if short duration plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?

That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass
driver. Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.

Ron

"N_Cook" wrote in message
...
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



I've always used this convention.

In article , "Paul Miller" wrote:

"N_Cook" wrote in message
...
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



I've always used this convention.


It would probably be safer to say, away from the magnet, just in case
the driver is reverse mounted in an enclosure or used in a isobarik
design. Knowing the DC movement may have little bearing
on the AC movement at any paticular time.

greg

"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?

That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.



Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.



That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.



Gareth.

In article , "Gareth Magennis" wrote:

"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?

That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.



Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.



That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.

There were many speakers that had inverted polarities on the tweeter.
You would not get a total null. Often there was a choice
of -3 db or + 3 dB. Neither were a good choice.

You have to know the phase at whatever frequency its at, plus
the crossover effects. Some speakers
make use of this and use the falling or rising phase of the driver
along with the crossover characteristic. And, your usually
assuming your on axis, but not always.

greg

GregS wrote:
In article , "Gareth Magennis" wrote:
"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?
That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.


Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.


That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.

There were many speakers that had inverted polarities on the tweeter.
You would not get a total null. Often there was a choice
of -3 db or + 3 dB. Neither were a good choice.

You have to know the phase at whatever frequency its at, plus
the crossover effects. Some speakers
make use of this and use the falling or rising phase of the driver
along with the crossover characteristic. And, your usually
assuming your on axis, but not always.

greg

I was told--way back when--that reversing the polarity of the middle
driver in a three-way system 'could' smooth out the response. As you
say, it's a tossup; but in many cases I found it to be true. In my
understanding (without doing actual measurements) it was always to
reduce the level in the area where the drivers in the system overlapped
in response. IOW, instead of reinforcing each other in that area and
producing a hump in response, the anti-phase component would negate it.

jak

In article ,
jakdedert wrote:

There were many speakers that had inverted polarities on the tweeter.
You would not get a total null. Often there was a choice
of -3 db or + 3 dB. Neither were a good choice.

You have to know the phase at whatever frequency its at, plus
the crossover effects. Some speakers
make use of this and use the falling or rising phase of the driver
along with the crossover characteristic. And, your usually
assuming your on axis, but not always.

greg

I was told--way back when--that reversing the polarity of the middle
driver in a three-way system 'could' smooth out the response. As you
say, it's a tossup; but in many cases I found it to be true. In my
understanding (without doing actual measurements) it was always to
reduce the level in the area where the drivers in the system overlapped
in response. IOW, instead of reinforcing each other in that area and
producing a hump in response, the anti-phase component would negate it.

If I recall correctly, this is due to the phase-shift/delay
characteristics of certain types of crossover.

I'm working from hazy memory here, but here's how I recall it: in
theory, a second-order crossover circuit (low-pass or high-pass)
introduces a 90-degree phase shift in the signal delivered to the
load, at the point at which the output to the load is 3 dB down from
full scale (the nominal crossover point). The phase shifts are in
opposite directions for low-pass and high-pass crossover elements.
Hence, if you use second-order crossover, and wire the drivers "in
phase", the signals to the drivers will actually be 180 degrees out of
phase at the -3 dB crossover point. Instead of summing to deliver
full power, they'll exactly cancel, resulting in a deep notch in the
frequency response.

By inverting the wiring to one driver or the other, you ensure that
the driver outputs are actually in-phase at the crossover frequency
and sum correctly rather than adding.

This theoretical analysis is, of course, muddied up in practice by
the nasty details of physical reality. It assumes that the drivers
are presenting purely resistive loads to their crossovers (uncommon
unless you've added a Zobel), that the drivers themselves aren't
adding any phase shift to the signal, and that their acoustic centers are
aligned so that their waveforms aren't being phase-shifted due to
physical offset (and this, again, is not the common case).

So, in practice, whether a two- or three-way system using second-order
crossovers will have a flatter frequency response or a better over-all
sound with "in-phase" or "out-of-phase" wiring of the drivers will
depend very much on the specifics of that speaker system... the
drivers, crossover, and physical mounting of the drivers (and probably
a dozen other factors as well).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article , jakdedert wrote:
GregS wrote:
In article , "Gareth Magennis"
wrote:
"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?
That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.


Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.


That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.

There were many speakers that had inverted polarities on the tweeter.
You would not get a total null. Often there was a choice
of -3 db or + 3 dB. Neither were a good choice.

You have to know the phase at whatever frequency its at, plus
the crossover effects. Some speakers
make use of this and use the falling or rising phase of the driver
along with the crossover characteristic. And, your usually
assuming your on axis, but not always.

greg

I was told--way back when--that reversing the polarity of the middle
driver in a three-way system 'could' smooth out the response. As you
say, it's a tossup; but in many cases I found it to be true. In my
understanding (without doing actual measurements) it was always to
reduce the level in the area where the drivers in the system overlapped
in response. IOW, instead of reinforcing each other in that area and
producing a hump in response, the anti-phase component would negate it.

jak

You NEVER want a peak in the 1-3 kHz area. Makes for a harsh speaker.
Polarities usually make a big difference in the sit down stand up test.

greg

Gareth Magennis wrote:
"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?
That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.



Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.



That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.

Indeed

Ron

In article , Ron Johnson wrote:
Gareth Magennis wrote:
"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?
That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.



Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.



That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.

Indeed

One thing not mentioned, time delay. A long horn
is going to shift the center line. So will the vertical axis.

greg

GregS wrote:
In article , Ron Johnson wrote:
Gareth Magennis wrote:
"Ron Johnson" wrote in message
...
N_Cook wrote:
Is it an international convention, for all time, that if short duration
plus
DC is appled to red or plus terminal, relative to the other one, then the
cone will move outwards ?
That seems to be the general rule, tho some loudspeaker manufacturers -
notably JBL - have in the past been known to wire their cabinets the
opposite way so that + on the input socket produces - at the bass driver.


Also some cabinets are wired with the horn driver in opposite
polarity to the bass driver.


That is because some crossover topologies require this to be the case.
Connecting the horn with the same polarity of the bass driver would result
in a Null at the crossover frequency.
Indeed

One thing not mentioned, time delay. A long horn
is going to shift the center line. So will the vertical axis.

greg

Also if you reverse polarity to the speakers you will have less dust
accumulate on the grille. Be sure to reverse both channels to preserve
proper phasing.

Ronbo wrote:

Also if you reverse polarity to the speakers you will have less dust
accumulate on the grille. Be sure to reverse both channels to preserve
proper phasing.

And protect your cat from being sucked into the boxes.

Regards,
H.

Hi Dave, in this case your memory is still good.

Choong

Dave Platt wrote:


I'm working from hazy memory here, but here's how I recall it: in
theory, a second-order crossover circuit (low-pass or high-pass)
introduces a 90-degree phase shift in the signal delivered to the
load, at the point at which the output to the load is 3 dB down from
full scale (the nominal crossover point). The phase shifts are in
opposite directions for low-pass and high-pass crossover elements.
Hence, if you use second-order crossover, and wire the drivers "in
phase", the signals to the drivers will actually be 180 degrees out of
phase at the -3 dB crossover point. Instead of summing to deliver
full power, they'll exactly cancel, resulting in a deep notch in the
frequency response.

By inverting the wiring to one driver or the other, you ensure that
the driver outputs are actually in-phase at the crossover frequency
and sum correctly rather than adding.

This theoretical analysis is, of course, muddied up in practice by
the nasty details of physical reality. It assumes that the drivers
are presenting purely resistive loads to their crossovers (uncommon
unless you've added a Zobel), that the drivers themselves aren't
adding any phase shift to the signal, and that their acoustic centers are
aligned so that their waveforms aren't being phase-shifted due to
physical offset (and this, again, is not the common case).

So, in practice, whether a two- or three-way system using second-order
crossovers will have a flatter frequency response or a better over-all
sound with "in-phase" or "out-of-phase" wiring of the drivers will
depend very much on the specifics of that speaker system... the
drivers, crossover, and physical mounting of the drivers (and probably
a dozen other factors as well).