Arcam Logo calibration, Phase setting, Volume level setting, Crossover frequency, English

The subwoofer’s has two jobs: firstly to reproduce accurately and with sufficient power the sub-bass that other ‘smaller’ speakers cannot (the centre speaker is almost always a ‘small’ speaker); and secondly to reproduce the ‘.1’ or low frequency effects (LFE) track of 5.1 or 7.1 material.

For optimum results, the subwoofer must be set up in the correct relation to the other speakers in the system. The two relevant controls are the crossover point and the subwoofer level.The crossover point establishes the frequency below which signals are redirected away from ‘small’ speakers toward the subwoofer. Setting the subwoofer level ensures signals that are of equal volume achieve the same sound pressure level no matter what frequency they are or which speaker they come from (i.e. subwoofer or satellite speaker).

In most surround-sound systems, two crossovers are available: one in the surround-sound decoder and one in the Logo unit.

In order to get the optimum sound in a variety of systems, Logo allows these controls to be used independently for systems with ‘Large’ front speakers and an LFE output from the surround-sound decoder.

Recommended settings for use with Muso speakers

Arcam’s Muso satellite speakers ideally complement the sound quality and design values of Logo.The recommended settings of Logo for use with Muso speakers are:

X-OVER FREQ	90Hz
X-OVER Q	0.5
Volume	8
Phase	0°

calibration

English

85	100	115		Crossover frequency
50			140
70			125	setting
X-OVER FREQ
35		160

In most systems, a crossover point for Logo of 90Hz is recommended.

If your satellite speakers are very ‘Small’ (and thus cannot reproduce much bass) you might like to set the crossover point higher than this figure to allow Logo to do more of the work. However, be aware that the higher the crossover point, the more directional the low frequency sounds, thus the more easily identifiable is the subwoofer’s physical position.

If your satellite speakers can reproduce reasonable bass, you can try a lower crossover point. Experimentation and listening will guide you to the right spot.

	0.9
0.7	1.1
0.5			Crossover Q setting
		1.3
0.3		1.5

X-OVER Q

The X-Over Q setting controls the slope of the trace beyond the cutoff frequency, in dB/octave.The aim is to make a ‘mirror image’ match with the slope of the high-pass filter – a steep cut-off of the high-pass filter from the sound processor/receiver should be matched by a steep cut-off of the low-pass filter from Logo. Similarly, if the sound processor/receiver provides a more gradual cut-off, the X-Over Q setting should have a lower value.

4	5	6
3			7
2			8
1			9	Volume level setting
0		10

VOLUME

Accurate volume level setting for a subwoofer ideally requires specialist measuring equipment such as a Real Time Spectrum Analyser or RTA. A regular SPL (Sound Pressure Level) meter will not work for this!

For most systems though simple experimentation by ear will suffice. Start with a medium setting (5) and experiment with Volume until low frequency sounds can be heard as part of the main sound and not traceable to the subwoofer directly. Most sound processors or receivers allow Sub levels to be trimmed ‘on the fly’ to counter excessively high or low levels from particular source material.

	Phase setting
PHASE

This has two settings: with the Phase button out (0°) and with the button in (180°).

A phase delay may be used to counteract the effect of sound waves from Logo interacting with and partially cancelling out or unduly emphasising sound from the satellite speakers.This effect depends critically on the relative positioning of subwoofer and satellite speakers and can also be remedied by relocating the subwoofer a short distance.The phase setting is available if relocation is not possible or impractical.

0

Gain, dB

-12

20 40 60 80 100 120

Crossover frequency, Hz

0

Gain, dB

-12

140 160

Q=1.5

Q=1.0

Q=0.71

Q=0.58

Q=0.49

Q=0.3

Crossover frequency

E-7