Atma-Sphere S 30 & Zero Autotransformer Boxes

Wilsynet and Clio09,
John Atkinson's measurements of my Joseph Audio Pulsars stated: "However, as indicated by its plot of impedance magnitude and electrical phase against frequency (fig.1), the Pulsar is an easy load for the partnering amplifier to drive. Not only is the phase angle relatively low, the impedance remains above 8 ohms for most of the audioband, dropping below that value only in the lower midrange, to reach a minimum magnitude of 6.5 ohms at 210Hz."

Here is a link to those measurements:

http://www.stereophile.com/content/joseph-audio-pulsar-loudspeaker-measurements

Wilsynet and Clio09,
Thank you for your informative posts. The speakers are 8 ohm with an impedance curve no lower than 6.5 ohms. Do you think the Zero Autotransformer will solve the problem? I do not listen to unreasonably loud music since my hearing is very sensitive. I am uncomfortable with the high volume levels that others are often able to tolerate.

Looking at the graph from the Stereophile review the impedance curve has a couple spikes in the bass region under 100 Hz. Other than that it is quite smooth. Using a 1:2 ratio on the autoformer would mean that the S-30 power would be around 45 watts for the most part. Those two spikes notwithstanding which appear to be just over 20 ohms. So at those points you might get slightly less than 45 watts, but at moderate listening levels should be just fine. Probably no different than my experience with my Spendor's.

My advice would be to try it standalone first and see how the amp fares. I think you might be fine. If you feel more power is needed then you can try the autoformers. If you live in the US and would like to try my set then contact me offline and maybe we can arrange for you to borrow them.

Clio09,
Thanks for your informative post -- greatly appreciated. This confirms Ralph's feeling and my own. That's what I was planning to do -- try the S-30 on its own and then add the Zero boxes if needed. I am looking for a pair on the used market. Regarding those spikes, it might help that I have REL sub.

Thank you very much for your kind offer. I would like to be able to take you up on it but I live in Asia which is a big problem when trying to put together a high end system. If I want to audition good equipment it means flying to Hong Kong, Bangkok or Singapore. I get to audition equipment infrequently and end up flying blind most of the time. I have had phenomenal success but have ended up selling off a lot of equipment over the years.