SC-IW Setup, Measurments and Analysis

The SC-1250 amplifier is extremely connection flexible and can be configured for just about any type of installation. The most common approach would be to use your receiver’s LFE subwoofer pre-output jack and connect it to the SC-1250’s LFE input. If your receiver or processor handles the entire subwoofer crossover duties you can disable the SC-1250's low-pass crossover to prevent cross over cascading. In my multi-channel system, a subwoofer LFE cross over setting of 60-Hz worked best and is the setting I used on my receiver setup for this review. The SC-1250 amplifier can control and power a variety of different subwoofers. The amplifier needs to be programmed for the specific type of subwoofer installation; this is achieved by powering up the amplifier while pressing any of the buttons on the front panel. After the amplifier boots up you can choose SC-in-wall (IW), SC-in-floor (IF), SC-in-ceiling (IC) or Generic Subwoofer (GS). Since this is an in-wall subwoofer the selection of the (IW) setting is the correct choice. Calibration is very easy thanks to the remote included with the SC-1250 amplifier. I calibrated the SC-IW subwoofers SPL to match the level of the speakers in my system using my trusty Radio Shack SPL meter. The amplifier has an adjustable phase setting of 0-90-180 and 270. The proper setting for the phase would be the setting in which you hear or measure the most even bass at your listening position. Unfortunately the phase setting is not independent for the two subwoofers and is applied to both “A” and “B” subwoofer output speaker terminals on the SC-1250 amplifier. I wanted to measure the response of the subwoofers with the two subwoofers out of phase. I mechanically reversed the phase of one of the SC-IW subwoofers at the amplifier’s subwoofer speaker terminal. Reversing the phase effectively placed one of the SC-IW subwoofers 180 degrees out of phase. After going through the multitude of phase settings with both subwoofers’ wire in phase and out of phase, I found the best setting for the room to be both subwoofers wired in phase and the amplifier phase setting at 0. Connecting the small supplied omni-directional microphone and pressing EQ on the remote enables the Automatic EQ program. The amplifier/subwoofer emits 12 “Sweep Tones” from 20-150Hz. After the amplifier completes and processes the measured information, the amplifier returns to normal operation and is now configured for your room. The SC-1250 has four preset EQ settings, for reference level the Jazz/Classical level applies no EQ or Volume Differential.

Measurements & Analysis

In-room measuring conducted at the listening position should not be considered a good indicator of how well the subwoofer system will perform in your room and should be used as a reference only. Just keep in mind that subwoofers will perform differently due to room dimensions, listening position, subwoofer placement, and room acoustical properties. I used the Rives Bass and Room Evaluation (BARE) analyzer with the omni-directional microphone placed at the primary listening position, with the SC-1250 amplifier set to the Reference Level EQ setting for all recorded measurements. All of the surround sound speakers were deactivated so they wouldn’t interfere with the subwoofer measurements. The Rives BARE system is fairly basic, giving me only two frequency response graphs to work with (5-50Hz and 5-500Hz) I decided to measure the response using both for a more accurate representation of how the subwoofers measured.

The first measurement taken 5-50 Hz, to my surprise measured fairly flat from about 18Hz-50Hz. As you can see the response dropped off rapidly at about 16Hz. Considering the SC-IW has an advertised low frequency cut off of about 22Hz I would say these subwoofers actually exceeded the manufacturers low frequency specification in my room. The second measurement of 5-500Hz shows a very similar response from 5-50Hz, a 10dB dip at 55Hz and then a gradual roll off at 60Hz. This is exactly what I expected as the receiver’s internal x-over is set for 60Hz. The dip at 55Hz is a characteristic of the room, as this room has absolutely no acoustical treatment in it at this time. Considering the less than perfect room conditions and the subwoofer placement issues I had to deal with, I was quite surprised to see the relatively good frequency response measurements.