SPL Parametric Equalizer, OPTIMIZER Owner's Manual

OPTIMIZER

parametric equalizer

Owner´s

Manual

Operation

.

Applications

.

Measurements

.

Specifications

©1994 SPL electronics GmbH

OPTIMIZER Owner´s Manual:
Operation, Applications,
Measurements, Specifications

Written by Paul White
and Hermann Gier

Manual version 1.1/94

The information in this document has been
carefully checked and is assumed to be correct.
However Sound Performance Laboratory (SPL
electronics GmbH) reserves the right to modify the
product described in this manual at any time.
This document is the property of SPL electronics
GmbH and may not be copied or reproduced in
any manner, in part or full without the authoriza­tion of SPL electronics GmbH.

Construction and circuit layout are subject to con­stant improvement and development. Changes
will be made without notice.

© 1994 SPL electronics GmbH

All rights reserved

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OPTIMIZER

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INTRODUCTION

4

I

NSTALLATION

7

C

ONNECTORS 7

O

PERATING LEVEL

8

P

OWER SUPPLY

8

R

EAR PANEL 9

I

NPUT & OUTPUT SPECIFICATIONS 9

APPLICATIONS

10

M

ASTERING WITH THE OPTIMIZER 10

O

PTIMIZER USED IN THE INSERTS 11

CONTROLS

12

F

RONT PANEL 12

D

UAL 13

A

CTIVE 13

M

ASTER-EQ 13

P

EAK 13

B

OOST/CUT (+/-) 14

B

ANDWIDTH Q15

F

REQUENCY & FREQUENCY RANGE 16

O

UTPUT 18

N

OTCH 19

P

ARAMETRIC, HIGHPASS, BANDPASS, LOWPASS 20

PHASE MEASUREMENTS

22

NOISE MEASUREMENTS

24

COMMON MODE REJECTION

25

LIMITED WARRANTY

26

4

OPTIMIZER

Congratulations on purchasing the Optimizer, one of the

most advanced and musical sounding parametric equalizer

currently available.

The Optimizer is a highly specialized and creative equali-

zer. In addition to familiar parametric functions, it features

a range of modes that enable it to perform Band-pass, High-

pass, Low-pass and Notch filtering. As you would expect

from SPL - the company that developed the highly acclaimed

Vitalizer psychoacoustic equalizer - the Optimizer is no ordi-

nary equalizer. It excels in both corrective and creative

applications and can produce many effects impossible to

achieve using conventional parametric equalizers. Yet it

remains very simple to operate.

The design of the Optimizer has been based on proven

psychoacoustic principles and particular regard has been

taken to the way the human hearing system perceives

sound, at all stages of development. Rather working out a

theoretically ideal filter response on paper and trying to

emulate it, we have taken a more creative tack, experimen-

ting directly with perceived sound across a wide range of fre-

quencies.

The result of this creative work is an equalizer without

equal, both technically and artistically. Not only does it pro-

vide a powerful, flexible and easy-to-operate means of equa-

lizing sound, but it boasts a noise level approaching the

theoretical minimum for advanced analogue circuit design

and a dynamic range even better than 18-bit digital systems.

The filter circuits are based on an advanced state-varia-

ble filter topography which employs the "proportional-Q"

principle, active output stages for each filter-band and the

new "roll-off"-function to produce a smooth and linear phase

response giving the Optimizer unsurpassed musicality and

sonic transparency.

Rather than employing the standard "constant-Q" equali-

zer design commonly used in sound reinforcement and room

equalizers, the Optimizer works on the proportional-Q prin-

ciple. The advantage of proportional-Q is that it produces a

more musical result and fine tuning of the filters is much

easier. The signal level is dependent of the bandwidth setting

- eliminating the need for constant level readjustment when

The OPTIMIZER is

designed for both

corrective and creative

applications, producing

effects impossible

to achieve using

conventional EQ.

Yet it remains

very simple to operate.

Rather working out a theore-

tically ideal filter response on

paper, we have taken a more

creative tack, experimenting

directly with perceived sound

across a wide range of fre-

quencies.

The Optimizer provides a
powerful, flexible and easy­to-operate means of equali-

zing sound.

The Optimizer produces a

smooth and linear phase res-

ponse giving unsurpassed

musicality and sonic transpa-

rency

The advantage of

proportional-Q is that it

produces a more musical

result and fine tuning of the

filters is much easier.

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OPTIMIZER

The Optimizer comprises four
identical filter stages which
can be configured for 4-band
mono, dual
2-band mono or 2-band ste­reo operation.

Each filter covers the same
enormous frequency range
10Hz to 23kHz.

Each filter has its own mode
switch, so complex combina­tions of filter types can be
used in the same signal path.

changing the filter settings. When broadening the band-

width, the boost or cut will be reduced proportionally, so

that the subjectively perceived loudness remains constant.

The proportional-Q principle operates according to the way

our hearing system perceives sound.

With constant-Q equalizers there is often only a limited

range of useable settings. Sometimes this is so narrow, you

may wonder why the Q-control was not permanently fixed

at the point it sounds really good. Above that position it

often starts to sound harsh and peaky, and below with the

broad bandwidth, the sound is colored so you need to con-

stantly re-set the boost/cut control. Not so with proportional

Q. The Q-control provides useable settings over the entire

range - giving you more versatility to be creative.

The Optimizer comprises four identical filter stages

which can be configured for 4-band mono, dual 2-band

mono or 2-band stereo operation. The front panel Dual

switch selects between 4-band or dual 2-band operation.

Both balanced XLR and unbalanced jacks are provided for

signal connections to and from the Optimizer. In Mono

mode, the filters are all connected in series, but the outputs

from each pair of filters remain accessible, so you can get

two differently filtered versions of the same signal which can

be useful when you are creating special effects.

Each filter covers the frequency range 10Hz to 23kHz in

four switched frequency ranges to give fine frequency con-

trol, regardless of which part of the audio spectrum is under

process. Tuning the equalizer is very intuitive because the

frequency control law has been designed to match the cha-

racteristics of the human hearing system.

Being able to equalize starting at 10Hz with full

boost/cut power gives a new dimension for mixing and pro-

ducing of subwoofer-compatible soundtracks.

The frequency response of the circuitry used in the audio

signal path exceeds the limits of human hearing by a consi-

derable margin, effectively eliminating undesirable phase

shifts which, even when relatively small, can seriously

impair the high frequency transparency of a less well-desi-

gned equalizer.

Each filter has its own mode switch to select between

High-pass, Low-pass, Band-pass and Parametric modes. In

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OPTIMIZER

addition each filter is equipped with a notch-filter. Selecting

the Notch mode overrides the mode switch selector. So com-

plex combinations of filter types can be used in the same sig-

nal path. For example, a parametric filter could be combi-

ned with a High- and Low-pass and Notch filter.

When working in Notch, Band-pass, High-Pass or Low-

Pass modes, you have a choice of roll-off characteristics

which greatly extends the tonal capabilities of the

Optimizer. For example, in the Notch filter mode, you have

control over frequency and bandwidth and also over the

steepness of the sides of the notch. The depth of the Notch is

in excess of 60dB, providing an extremely high degree of

rejection compared with conventional parametric filters.

The subjective performance of certain classic equalizers is

highly dependent on the roll-off characteristics of their filter

circuitry. These equalizers sound excellent, but their circuit

topography imposes a rather fixed character on them. By

contrast, the Optimizer´s proportional-Q parametric filter

design, combined with its switchable alternative filter

modes, gives you the flexibility to emulate many different

types of equalizer. In addition, you can set up further equa-

lization types that even the best conventional equalizers can-

not provide.

To keep the control layout simple, the BoostCut control

used in Parametric mode becomes the Gentle/Steep control

in Notch, Band-Pass, High-Pass or Low-Pass modes. Turning

the control fully anti-clockwise produces a gentle roll-off

while turning it fully clockwise produces a steep-sided res-

ponse. If the control is set in the center position, the input

signal will cancel itself out completely, resulting in no out-

put. Settings between the extremes and the center (null) posi-

tion produce further useful variations in filter slope charac-

teristic, though you may need to compensate for the level

loss incurred by settings close to the center position, by tur-

ning up the Output level control.

Selecting a steep filter characteristic produces a tightly

focused, punchy tonal characteristic while choosing a gentle

slope produces a subtle change in tonality which has the

effects of adding a sonic gloss to the programme material.

We have invented a new all active output stage approach

to mixing filters: Commonly filters in parametric or graphic

equalizers mix passively resulting in increased phase distor-

The depth of the Notch

is in excess of 60dB

The Optimizer´s proportional-

Q parametric filter design,
combined with its switchable
alternative filter modes, gives

you the flexibility to emulate

many different types of equa-

lizer.

The Boost/Cut control beco-

mes the Gentle/Steep control

in Notch, Band-Pass, High-

Pass or Low-Pass modes.
Turning the control fully

anti-clockwise produces a

gentle roll-off while turning it

fully clockwise produces a

steep-sided response.

The Optimizer has active

output stages for each filter

increasing phase stability

dramatically.

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OPTIMIZER

tion as each filter is added to the signal path. The Optimizer

overcomes this fault by using controllable all active output

stages resulting in a significantly improved phase response,

even when all four filters are linked up. The Output control

allows level adjustments to compensate for level changes due

to dramatic boost or cut adjustments.

The Optimizer is designed for standard 19” rack moun-

ting and occupies 2U of rack space. Avoid mounting the unit

directly above power amplifiers or power supplies that radia-

te significant amounts of heat and always connect the mains

earth to the unit. Fibre or plastic washers may be used to pre-

vent the front panel becoming marked by the mounting

bolts. Care must be taken when rack mounting the unit to

support the rear of the case, especially in mobile systems.

The Optimizer has connectors for unbalanced as well

balanced operation.

The XLR inputs and outputs are electronically balanced

on conventionally wired XLRs (pin 1 screen, pin 2 hot and

pin 3 cold). Unbalanced inputs and outputs are also availa-

ble on mono, quarter-inch jacks.

The signal connected to the jacks will always be prefer-

red. A connection set-up with XLR´s and jacks can remain

connected. Unplugging the jacks will select the XLRs as pri-

mary inputs.

The XLR inputs and outputs can be unbalanced by

connecting the pin 3 to the ground terminal (pin 1). For pro-

per wiring see figure below.

The operating level is switchable between High and Low

(nominally 0dBu or -10dBv). Choose the High position for all

pro-audio applications. Select the -10dB when the input sour-

The OPTIMIZER offers XLR
connectors for balanced ope­ration and quarter-inch jacks

for unbalanced use.

How to unbalance balanced
XLR connetors.

The operating level is
switchable between High and
Low (nominally 0dBu or ­10dBv)

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8

OPTIMIZER

ce is not driving Optimizer´s filters sufficiently with the pro-

viso that the Peak LED on the front panel is not continually

flashing. This will achieve equalization at a lower signal

level and will result in a more intensely processed sound.

Note: this level change also effects the signal when the filters

are in bypass, so you will loose direct comparability as the

listening level changes.

Based around a toroidal transformer, the integral power

supply is designed to minimize induced hum and noise due

to the non existence of an air-gap. The primary voltage may

be selected between 230V/50Hz and 115V/60Hz by means of

a recessed slide switch on the rear panel.

A Ground Lift switch is provided to assist in the eliminati-

on of ground loop induced hum in complex installations. If

ground loop problems remain after activating the Ground

Lift switch, do not disconnect the mains earth. Instead try

disconnecting the signal screen at the end the cables that

connect the outputs of the Optimizer to the patchbay. If such

measures are necessary, balanced operation is recommen-

ded.

When the Ground Lift switch is set off, the circuit ground

is connected to the chassis ground.

The mains fuse should be rated at 800mA. A detachable

3-wire, U-ground power cord is included in the packaging.

A Ground Lift switch is provi-

ded to assist in the eliminati-

on of ground loop problems.

PP

OOWWEERRSSUUPPPPLLYY

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OPTIMIZER

Input- & output

specifications

XLR - balanced:
Inputs:
Electronically balanced
(differential) transformerless
Impedance: = 20kOhms
Nominal
input level: +6dB
Input level
selector: HIGH (0dB)

LOW(-10dB)
Maximum
input level: +22dBm
Input peak: LED indica­tes potential peak 3dB before
actual clipping.

Outputs:
Electronically balanced
(differential) transformerless
Impedance: < 75 Ohms
Nominal
output level: +6dB
Minimum
load ohms: 600 Ohms

Connectors:
Type: Neutrik NC 3 XLR
Pin wiring:

Pin 2 = high (+)

and Pin 3 = low (-)

Jacks - unbalanced:
Inputs: unbalanced
Impedance: = 20kOhms
Nominal
input level: 0dB

Outputs: unbalanced
Impedance: < 600 Ohms
Nominal
output level: 0dB
Minimum
load ohms: 600 Ohms

Connectors:
Type: 1/4" Jacks (6,25mm)
Pin-Wiring:

Tip = high (+)

and Sleeve = GND

GND-LIFTswitch:

off = chassis ground
on = ground lift

Power selector: 115V / 60Hz

230V / 50Hz

Fuse: 800mA fast

RR

EEAARRPPAANNEELL

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