1 plus 1, Various, add subwoofer SPW-1

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Jim Mullin2004-02-24 15:24

Andy, I have a pair of 1+1\'s and would like to add a subwoofer. I have found an Acoustat SPW-1 in excellent condition. What would be your recommendation regarding the addition of this sub to the 1+1\'s. I own 4 monoblock amps so biamping would appear to be the way to go. What\'s the best way to crossover the unit? Do I need an electronic crossover? Any suggestions would be much appreciated. Thanks, Jim

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Andy Szabo2004-02-24 15:25

The Acoustat SPW-1 Woofer should be an excellent match for the Model 1+1. It has a fairly ”fast” response, due to its use of four small drivers. Furthermore, even though it is a single cabinet system, it preserves some of the stereo information by employing two side-firing woofers per channel.

The cabinet contains its own 100 Hz crossover, I think at -12 or -18 dB per octave. A switch on the cabinet allows use of either the internal passive crossover, or an external active (electronic) crossover.

At the very least, you'll need to provide a crossover for the 1+1, to roll-off below 100 Hz. I would recommend a simple -6 dB (first-order) filter, same as is used on the Spectra series. This can be accomplished passively(*), or better still, with an electronic crossover. Since you already have the required four channels of amplification, this may be the best way to go. An electronic crossover will also allow you to adjust the relative levels going to the 1+1's and the woofer, since they are probably not the same efficiency.

You may need to do some experimenting with crossover frequency, slopes, levels, and phasing to get the combination just right.

(*) The simplest way to roll-off the 1+1's at -6 dB per octave is to change the input coupling capacitor on the corresponding amplifier channels. The capacitor value will depend on the input impedance of the amplifier: it's best to consult the amp's manufacturer on how to do this.

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