Jim Lesurf wrote:
I don't know the details of the crossover networks in question.
However if you are going to bi-amp the system it may make sense to
remove some/all the networks between power amps and speakers and,
instead, use networks at the inputs to the power amps. Done
correctly, this may well give much better results that networks that
have to work at high powers in the complex loads.
The plan so far is a low-pass filter before the bass amp, with full range
going to the mid/top through a conventional crossover. There are two
circuits for the B110, depending on whether it's in a 3-way or 2-way setup.
I'm considering copying the 2-way version and rolling off the B110 low end
using cabinet damping. The filter on the bass amp would be configured to
match this roll off.
Am I right in thinking that air-cored inductors are better than those
with some sort of ferrite(?) core?
Depends upon your definition of 'best' and the circumstances.
Better than the ferrite-cored ones in the original DN12. I need to make new
crossovers anyway, and it looks like I can wind my own coils for less than
half the cost of ready-made ones.
Ferrite cores mean you can reduce the length of wire required. This
can mean a physically smaller coil and/or a lower coil resistance
and/or lower resistance due to internal impedance, etc. Hence the
ferrite may improve things on the conductor side. However it may,
itself, increase magnetic 'singing' of the coil and/or introduce some
non-linearity.
Is that an effect the coil has on itself (so to speak)? Can I counteract it
with suitable construction and physical layout?
(That said, it may well be that the speaker units
introduce more distortion than the use of a suitable ferrite.) Sizes
and shapes also affect the amount of coupling from/to a coil and
surrounding components. Ferrite non-linearity or saturation may not
matter much in some circumstances, but make ferrites a poor choice in
other circumstances.
If ferrites either don't matter much, or are a poor choice, does that mean
that air-cored will always be similar or better?
So, "It depends"... :-)
Aye. :-)
For the same value, would an air-cored version be physically larger?
If so, is that because it requires more turns?
and/or a larger cross-sectional area.
Do you mean thicker wire, or something to do with the dimensions of the
coil?
What is the best type of capacitor to use wthin sensible cost limits?
Answer similar to the above. :-)
I think I'm trying to spec the crossover compoenents such that likely
compromises with these are eliminated - it seems that decent parts aren't
too expensive, so, rather that get into esoterica like how much distortion
my old drivers have, I'm tempted to over-engineer the crossovers by using
'known good' stuff.
Are you wishing to compare bipolar electrolytics with other types, or
are you excluding them?
I'm willing to consider anything that will do a good job without being
hugely expensive or overly time-consuming. Maybe I should establish the
shortcomings of the various types...
The advantage of using crossover/equalising networks between pre and
power amps is that you can avoid a lot of the above problems as the
required voltage and current levels in the components will be much
lower. This means you can use smaller, cheaper, and better perfoming
coils/caps.
Since there will be two amps, but 3-way speakers, I'd have to tri-amp to
fully implement the crossovers before the power amps (which would wipe out
the saving). In practical terms, how much improvement is there likely to be
by driving the B110 and T27 from separate amps, compared with using a single
amp to drive both through a conventional crossover built with components of
good repute?
I should mention that the reason for bi-amping is to provide enough power to
the bass speakers and to account for the change in impedance. Making new
crossovers is kinda a knock-on effect from that.
The disadvantage is that producing the correct network may involve a
fair bit of work as it won't be a simple 'copy' of the speaker
arrangement.
But there should be fairly standard circuits/methods out there which will
give similar crossover points and slopes.
--
Wally
www.artbywally.com
www.wally.myby.co.uk/music
Crossover questions
Linear Mode
