Is my amp the problem?

OK. The 2x4HD has a rated maximum output of 2 volts, which should be fine relative to the 0.775 volt sensitivity the Crown is set for.

However the 2x4HD’s input impedance of 10K is still fairly low. And if I’m correct in understanding that you have been connecting the LS100 to both the miniDSP and the Modwright amp, the LS100’s output stage is most likely seeing the combined parallel impedances of the miniDSP (10K) and the Modwright amp (23K). That combined impedance would be (23K x 10K)/(23K + 10K) = 6.97K, which again could very well be too low for the LS100 to drive without significant rolloff in the deep bass region. And with adverse effects perhaps resulting at higher frequencies as well, that are handled by the Modwright amp and the mid/hi drivers.

That would most likely be the case regardless of whether you have been using the LS100’s XLR output or its second RCA output to drive the Modwright amp, because its XLR output is described as being driven with a single-ended signal. Which I would feel very confident means that the same output stage (and output coupling capacitor) is driving both of the RCA connectors AND the XLR connector.

So that’s one more reason why eliminating the mini may very well be helpful.

Regarding your question about a Zobel network, as Auxinput indicated I believe what that would make possible is just a reduction or elimination of the impedance rise of the woofer that occurs at midrange and treble frequencies, as a result of its inductance. I don’t think, though, that a Zobel would allow you to reduce the relatively narrow impedance peak I referred to that occurs in the vicinity of 30 Hz. But that peak may very well not be an issue anyway, its only significance perhaps being that the maximum power capability of the amp at frequencies in that vicinity would be a good deal less than its 8 ohm rating.

Good luck. Regards,
-- Al

Good comments by Auxinput.  I just noticed something further about the Modwright amp.  I had stated its input impedance as being 23K, because the impedance is indicated on its webpage as "Min. 15K 50Khz; 23K 1Khz," and I considered the 50 kHz impedance to be irrelevant.  Although I wondered a little why he would bother specifying a 50 kHz impedance.  However I now see that its manual (in contrast to the webpage) indicates an input impedance of "Min. 15K at 50Hz [not kHz]; 23K at 1Khz."

So that makes it all the more important to avoid requiring the LS100 to drive a low input impedance device in addition to the Modwright amp.  My suggestion at this point is that you communicate with Dan and ask him what minimum load impedance he would recommend be used with the LS100.  While you're at it, also ask him to clarify if the amp's specified input impedance applies to its balanced input or its unbalanced input or both.

Regards,
-- Al
   

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