Rather than the idea I mooted recently about making compact tranmission
lines using Kef B139s and driving them with a filtered signal to provide
lift where the speakers roll off, I have another option - I have a total of
four B139s, two in the existing speakers, and two bought as spares and/or
drivers for the future bass units.

Am I right in thinking that some sort of push-pull set up will give me a
shallower roll-off for a given size? What design approaches are there, and
how do they compare?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

Wally wrote:

Am I right in thinking that some sort of push-pull set up will give
me a shallower roll-off for a given size? What design approaches are
there, and how do they compare?

Been reading this...

http://www.maximacar.com/isobaric.htm

It says that having the drivers facing towards or away from each other, as
opposed to facing the same way, gives the "benefit of push-pull operation".
Does this have something to do wth the driver having a different response
when the cone moves away from the magnet compared to towards the magnet,
such that having the pair of drivers doing one half of each movenment
reduces the variation in a single driver. Ie, a bit like the idea of matched
valves in a push-pull amplifier giving less variation between the +ve
and -ve halfs of the waveform?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

Wally wrote:

Am I right in thinking that some sort of push-pull set up will give
me a shallower roll-off for a given size? What design approaches are
there, and how do they compare?

Been reading this...

http://www.maximacar.com/isobaric.htm

It says that having the drivers facing towards or away from each other, as
opposed to facing the same way, gives the "benefit of push-pull operation".
Does this have something to do wth the driver having a different response
when the cone moves away from the magnet compared to towards the magnet,
such that having the pair of drivers doing one half of each movenment
reduces the variation in a single driver. Ie, a bit like the idea of matched
valves in a push-pull amplifier giving less variation between the +ve
and -ve halfs of the waveform?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

In message , Wally
writes
Wally wrote:

Am I right in thinking that some sort of push-pull set up will give
me a shallower roll-off for a given size? What design approaches are
there, and how do they compare?

Been reading this...

http://www.maximacar.com/isobaric.htm

It says that having the drivers facing towards or away from each other, as
opposed to facing the same way, gives the "benefit of push-pull operation".
Does this have something to do wth the driver having a different response
when the cone moves away from the magnet compared to towards the magnet,
such that having the pair of drivers doing one half of each movenment
reduces the variation in a single driver. Ie, a bit like the idea of matched
valves in a push-pull amplifier giving less variation between the +ve
and -ve halfs of the waveform?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.




Got it in one! Exactly analogous to push-pull cancelling out even
harmonics in a class-A amp.
--
Chris Morriss

In message , Wally
writes
Wally wrote:

Am I right in thinking that some sort of push-pull set up will give
me a shallower roll-off for a given size? What design approaches are
there, and how do they compare?

Been reading this...

http://www.maximacar.com/isobaric.htm

It says that having the drivers facing towards or away from each other, as
opposed to facing the same way, gives the "benefit of push-pull operation".
Does this have something to do wth the driver having a different response
when the cone moves away from the magnet compared to towards the magnet,
such that having the pair of drivers doing one half of each movenment
reduces the variation in a single driver. Ie, a bit like the idea of matched
valves in a push-pull amplifier giving less variation between the +ve
and -ve halfs of the waveform?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.




Got it in one! Exactly analogous to push-pull cancelling out even
harmonics in a class-A amp.
--
Chris Morriss

Chris Morriss wrote:

Got it in one! Exactly analogous to push-pull cancelling out even
harmonics in a class-A amp.

So, improved fidelity of the bass waveform, then. Do drivers typically have
inconsistencies in response that are dependent on the direction the cone
moves in?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

Chris Morriss wrote:

Got it in one! Exactly analogous to push-pull cancelling out even
harmonics in a class-A amp.

So, improved fidelity of the bass waveform, then. Do drivers typically have
inconsistencies in response that are dependent on the direction the cone
moves in?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

In message , Wally
writes
Chris Morriss wrote:

Got it in one! Exactly analogous to push-pull cancelling out even
harmonics in a class-A amp.

So, improved fidelity of the bass waveform, then. Do drivers typically have
inconsistencies in response that are dependent on the direction the cone
moves in?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.




Well they shouldn't have of course!

In general the magnetic flux isn't symmetrical each side of the cone
resting position, so drivers do produce even-order distortion even at
low levels. At high levels more non-linearities come into play of
course as the cone hits mechanical limits, and the coil comes out of the
main flux area of the magnet gap.
--
Chris Morriss

In message , Wally
writes
Chris Morriss wrote:

Got it in one! Exactly analogous to push-pull cancelling out even
harmonics in a class-A amp.

So, improved fidelity of the bass waveform, then. Do drivers typically have
inconsistencies in response that are dependent on the direction the cone
moves in?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.




Well they shouldn't have of course!

In general the magnetic flux isn't symmetrical each side of the cone
resting position, so drivers do produce even-order distortion even at
low levels. At high levels more non-linearities come into play of
course as the cone hits mechanical limits, and the coil comes out of the
main flux area of the magnet gap.
--
Chris Morriss

Chris Morriss wrote:

So, improved fidelity of the bass waveform, then. Do drivers
typically have inconsistencies in response that are dependent on the
direction the cone moves in?

Well they shouldn't have of course!

In general the magnetic flux isn't symmetrical each side of the cone
resting position, so drivers do produce even-order distortion even at
low levels. At high levels more non-linearities come into play of
course as the cone hits mechanical limits, and the coil comes out of
the main flux area of the magnet gap.

Got the idea. Many years ago, I once heard a pair of Linn Isobariks in Russ
Andrews and thought the bass was amazingly solid and clear. Someone else was
auditioning, I was just milling about. I think it was a jazzy track with
acoustic bass.

Maybe this isobarik idea is worth pursuing instead of the transmission
lines...


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.