BANDPASS FILTER CIRCUIT DESIGN

The Design of Active Crossovers

The Design of Active Crossovers is a unique guide to the design of high-quality circuitry for splitting audio frequencies into separate bands and directing them to different loudspeaker drive units specifically designed for handling their own range of frequencies. Traditionally this has been done by using passive crossover units built into the loudspeaker boxes; this is the simplest solution, but it is also a bundle of compromises. The high cost of passive crossover components, and the power losses in them, means that passive crossovers have to use relatively few parts. This limits how well the crossover can do its basic job.
Active crossovers, sometimes called electronic crossovers, tackle the problem in a much more sophisticated manner. The division of the audio into bands is performed at low signal levels, before the power amplifiers, where it can be done with much greater precision. Very sophisticated filtering and response-shaping networks can be built at comparatively low cost. Time-delay networks that compensate for phyical misalignments in speaker construction can be implemented easily; the equivalent in a passive crossover is impractical because of the large cost and the heavy signal losses. Active crossover technology is also directly applicable to other band-splitting signal-processing devices such as multi-band compressors.
The use of active crossovers is increasing. They are used by almost every sound reinforcement system, by almost every recording studio monitoring set-up, and to a small but growing extent in domestic hifi. There is a growing acceptance in the hifi industry that multi-amplification using active crossovers is the obvious next step (and possibly the last big one) to getting the best possible sound. There is also a large usage of active crossovers in car audio, with the emphasis on routing the bass to enormous low-frequency loudspeakers.
One of the very few drawbacks to using the active crossover approach is that it requires more power amplifiers; these have often been built into the loudspeaker, along with the crossover, and this deprives the customer of the chance to choose their own amplifier, leading to resistance to the whole active crossover philosophy. A comprehensive proposal for solving this problem is an important part of this book.
The design of active crossovers is closely linked with that of the loudspeakers they drive. A chapter gives a concise but complete account of all the loudspeaker design issues that affect the associated active crossover.
This book is packed full of valuable information, with virtually every page revealing nuggets of specialized knowledge never before published. Essential points of theory bearing on practical performance are lucidly and thoroughly explained, with the mathematics kept to an essential minimum. Douglas' background in design for manufacture ensures he keeps a wary eye on the cost of things.
Features:
Crossover basics and requirements
The many different crossover types and how they work
Design almost any kind of active filter with minimal mathematics
Make crossover filters with very low noise and distortion
Make high-performance time-delay filters that give a constant delay over a wide range of frequency
Make a wide variety of audio equaliser stages: shelving, peaking and notch characteristics
All about active crossover system design for optimal noise and dynamic range
There is a large amount of new material that has never been published before. A few examples: using capacitance multipliers in biquad equalisers, opamp output biasing to reduce distortion, the design of NTMTM notch crossovers, the design of special filters for filler-driver crossovers, the use of mixed capacitors to reduce filter distortion, differentially elevated internal levels to reduce noise, and so on.
Douglas wears his learning lightly, and this book features the engaging prose style familiar from his other books The Audio Power Amplifier Design Handbook, Self on Audio, and the recent Small Signal Audio Design.
*It is unique; there are no other books wholly on this subject, which is increasing in relevance and popularity *It contains never-before-published information *The author has practical experience of electronic crossover design for quantity production.

The Sanctuary of Gethsemane
Gethsemane from GAT + SHEMANIM, means "(Olive) Oil Press". It is the name of a natural grotto next to the "Tomb of Mary" and her Assumption. Jesus often visited the grotto and it was here that He was betrayed and arrested. In time, however, the entire area at the foot of the Mt. of Olives was called GETHSEMANE.
The Garden of Olives - Located above and to the right of the Grotto of Gethsemane (to the left of the Basilica, facing the facade) and enclosed by a fence. Here there are eight olive trees held by tradition to be the silent witnesses of Jesus' prayer and suffering the evening before His crucifixion.
The Basilica of the Agony was built to recall how Jesus agonized over us to the point of sweating blood (Luke 22:44). This is the third basilica built on this site:
The Bizantine [sic] Basilica. Constructed in the time of Theodosius (AD 380), it had, at the center of the apse, the "Rock of the Agony" which is still conserved. It was smaller than the present basilica, had a beautiful mosaic floor, and was destroyed in AD 614.
The Crusader Basilica was erected in the 12th century. Remains are still visible to the south (left) of the present church. It was destroyed around AD 1200.
The New Basilica. Begun in 1919 after the design of the Biyzantine [sic] Basilica and planned by architect Antonio Barluzzi, it was completed in 1924. Natural light filtered by alabaster windows creates a climate of prayer and invites one to prostrate oneself before the "Rock of the Agony" which has been conserved directly in front of the altar. This basilica is also called "The Church of All Nations" because of the contributions offered by different nations for the mosaics of the apses and cupolas, in order they are:
Forward Mosaics: IRLANDIA - The Kiss of Judas, M. Barberis
UNGHERIA - Christ in Agony, D'Achiardi
POLONIA - "I Am" "Ego Sum" M. Barberis
Overhead Cupolas: ARGENTINA, BRAZIL, CHILE, MEXICO, ITALY, FRANCE, SPAIN,
ENGLAND, BELGIUM, CANADA, GERMANY, UNITED STATES
The wrought iron work surrounding the "Rock of Agony":AUSTRALIA
The Mosaics of the Facade are by Bergellini. Pieces of the original Byzantine mosaic floor are visible under glass panels.

Sign at Gethsemane

Trust you all must be quite sick of my St Peter Cathedral shots by now haha! Hopefully this will be the final one in my series for now. This photo is shot at the side of the cathedral with great emphasis on the pillars and the well defined arches. I intentionally took this photo with a crazy angle in mind. This shot is taken on my tripod tilted about 60 degree to the ground. Its toppling down with the weight of my cam on it but i was pressing it hard to the floor while kneeling down. I bet people must be thinking how lovely is this guy... praying at one corner while still taking this shot. LOL! :P

-----------------------------------------------------------------------------------------

About

St. Peter's Cathedral is the mother church of the Anglican Diocese in South Australia. This Cathedral was started in 1869 and the first section was completed and opened fully for services in 1877

The shot

Standard 3 exposures HDR shot (-2..0..+2EV) with tripod using the Canon EF-S 18-55mm lens and a polarized light filter

Photoshop

- Added a layer effect of 'curves' to increase the overall contrast.
- Added another layer effect to decrease saturation of reds and yellows.
- Dodged a bit to highlight the light reflection on the floor
- Used unsharp mask ( as always ) on the background layer

You

All comments, criticism and tips for improvements are ( as always ) welcome.

-----------------------------------------------------------------------------------------

This book presents the design of active RC filters in continuous time.
Topics include:

filter fundamentals

active elements

realization of functions using opamps

LC ladder filters

operational transconductance amplifier circuits (OTACs)

MOSFET-C filters
Continuous-Time Active Filter Design uses wave variables to enable the reader to better understand the introduction of more complex variables created through linear transformations of voltages and currents.
Intended for undergraduate students in electrical engineering, Continuous-Time Active Filter Design provides chapters as self-contained units, including introductory material leading to active RC filters.

<< Arhiva >>