Atma-sphere S-30 with Reference 3A?

Eyeballing the impedance curve and frequency response curve measured by SoundStage, I think this speaker would work quite well with the S-30. The impedance curve is admirably smooth, and the impedance rise around 2.5 kHz is just about centered on the off-axis dip from the midwoofer beaming. So the interaction with the high output impedance of the S-30 will give about one dB more output in that region, which will not be a problem because the speaker's power response is down several dB in that region already.

Between 70 and 90 Hz, you'll get about 2 dB more output than what SoundStage measured, again as a result of the interaction between the speaker's input impedance and the amplifier's output impedance. In most cases, this will be welcome - if not, stuff some polyfill into the port.

It looks to me like the impedance stays above 6 ohms, and the actual sensitivity is 89 dB/2.83 volts according to SoundStage:

http://www.soundstagemagazine.com/measurements/reference3a_mmdecapo/

In my opinion, this amp/speaker combination will work fine. The speaker is not within the "ideal" range for that amp, but the impedance curve is benign and zigs where the power response (summed omnidirectional response - not shown but can be guesstimated) zags. I would guess that the midwoofer will begin to exceed its linear excursion limits and start to compress and lose clarity several decibels below the theoretical amplifier clipping threshold of about 103 dB.

Duke
dealer/manufacturer

I used an S-30 with the deCapo for about 2 years and it worked very well. The deCapo has a wonderful mid band and the S-30 shows that to great effect. But, but, but...

the speaker has no deep bass and is a bit lean up into the mid-bass, Notwithstanding Duke's observation, above, IME the S-30 will do nothing to ameliorate that. The tonal balance of the speaker was pretty consistent with all of the amps I paired it with, but struck me as "even more evident" when paired with the S-30.

Good Luck,

Marty

Marty, thanks for posting your observation. I would guess that the gentle, fairly broad increase in energy in the 2 kHz region psychoacoustically more than offsets the fairly narrowband increase in energy in the upper bass region. I hadn't thought of that.

Duke

If Sean wanted to stick with Atma-sphere would a Speltz transformer to raise the impedance be adviseable, or the S-30 just less than ideal for the DeCapo?