Specifications

reversed.

I next turned the main speakers back on and proceeded to smooth the response around

the crossover frequency using the polarity, phase and low-pass crossover controls on the

SMS-1. These can be found on the second OSD screen page which is entered by selecting

NEXT.

This screen initially looks quite complicated, but if you restrict yourself to making changes

in the Setup column only to start with, these get copied automatically across all the

presets. Later on, when you get more adventurous, you can start changing settings for

each individual preset.

I mentioned earlier that the SMS-1 can be connected into an existing setup in several

different ways. For example, where the front left/right speakers are full range, the

system may sound best if they receive a full range signal and the sub merely fills in the

extreme bass where the main speakers naturally start to roll off. Achieving a seamless

transition between the sub and main speakers in this scenario requires the sub’s low pass

crossover frequency and slope to be perfectly mated to the natural in-room roll off from

the main speakers. This is an area where the SMS-1 excels because it provides precise

control over both parameters. Moreover, this is performed in the digital domain and will

typically be more accurate than the equivalent analog crossover circuit in most

subwoofers. The SMS-1 allows the low-pass crossover to be precisely set in 1 Hz steps in

the range 15 Hz to 199 Hz. By default, it is set to 80 Hz. The filter slope can be set to

values of 6, 12, 18, 24, 30, 36, 42 or 48 dB/octave, with a default setting of 24

dB/octave.

I chose to disable the Low-Pass Crossover in the SMS-1 by setting it to OFF, leaving my

SSP to supply a suitably low-pass filtered subwoofer signal. However, this is by no means

prescriptive. The tools are there to be used, and in some circumstances it may be

desirable to use the LPC in the SMS-1 in conjunction with that in the SSP. The excellent

article Bass Management Woes: Trouble on the Slopes gives some reasons why this may

be necessary, and although it is probably not the right fix for the problem, the SMS-1

may still be able to help.

You can set a suitable subsonic filter frequency to help protect the subwoofer from trying

to reproduce signals below its design limits. By default, this is set to 15 Hz with a

24dB/octave slope, but you can set the frequency in the range 15 Hz to 35 Hz, and the

slope can be 6, 12, 18, 24, 30, 36, 42 or 48 dB/octave. I decided to set it to 20 Hz to

match the tuning point of the sub and left the default slope alone.

I then tried both settings for polarity (+/-) followed by each phase setting from 0° to

180° in 15° steps, using the TEST key on the remote control to flick to the sweep screen

and check the response each time. I was looking for settings that gave the flattest sweep

response around the crossover frequency region (63 Hz). I finally settled on polarity +

and phase 90° settings to obtain a basic system response.

So far, so good. There was already some improvement from my original response and I

had yet to apply any equalization.

Click Here to Go to Part IV.

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