Spectra 33, Various, Spectra 33 and SWP-1

Read more on the Acoustat Spectra 33 in our home audio section

Roger Crowe2004-02-23 22:21

Andy, you have been of great help to me in the past and I thank you for it. I have acquired a pair of Spectra 33\'s and am enjoying them immensely. They are currently being run with a Sonographe SA-120 and sound very nice. Most recently, I have purchased a SPW-1 and plan on running it with this system.

Here is my question; Do I obtain another SA-120 and bridge them both and run a right channel/left channel setup with one SA-120 powering the speaker/sub on each side, or am I better off to purchase a TNT-200 and use that to power the SPW-1 exclusively and continue to use the SA-120 to power the panels. Thank you, Roger Crowe

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Andy Szabo2004-02-23 22:21

It is not necessary to use additional amplification when using the SPW-1 woofer system with the Spectra series. Using the 100-Hz crossover in the Spectra, and connecting the SPW-1 to the Spectra\'s ”woofer output”, will present essentially the same load to the amplifier as if you were using the Spectra by itself. In fact, the load may be even a little easier on the amplifier, due to the less severe impedance of the woofer vs. the ESL. (Adding a woofer to the system does not require more power: the power below 100 Hz that was going to the ESL is now being diverted to the woofer.)

The SPW-1 is intended to be connected in this manner, and I would recommend you try that before investing in another amplifier.

If you are set on the idea of adding amplification for the SPW-1, I do not recommend any arrangement involving bridged amps. Each channel of a bridged amp ”sees” only half the load impedance. If you bridge an amplifier into a 4-ohm load like the Spectra, then each channel will be loaded to 2-ohms. Few amplifiers perform well at that low an impedance, and some may even exhibit instability (oscillation or thermal shutdown).

For a multi-amplifier set-up, your best bet is to use two matched amplifiers: one running in stereo for the ESL\'s, and the other running in stereo for the woofer. If you use mismatched amplifiers, you may have level matching problems, due to the likelihood that each amplifier will have different gain. If the amplifier with the higher gain does not have level controls (enabling you to reduce the overall gain), then it will be difficult to match the levels.

Another (and probably better) approach is to obtain a single, larger amplifier. I wasn\'t able to find any information on the SA-120, but based on other models in the SA series, I will assume this is a 60-watt per channel amplifier. That\'s not a lot of power when it comes to driving ESL\'s. If you are not satisfied with the total sound output with a single SA-120 driving both the ESL and the woofer, then adding another SA-120 for the woofer will add very little to the total system output. If it\'s more volume you\'re after, then a single stereo amp of 150-200 watts per channel is the way to go. (In which case, that TNT-200 you mentioned would be an excellent choice.)

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