Andrew Virnuls wrote:

My wife had a Denon system with Denon/Mission speakers when I met her. I
thought it sounded quite good, but wondered what it would sound like with
different speakers. So I tried it with the Rogers LS4as that I used to use
as my main speakers and now use as rear speakers in an AV setup.

I thought it sounded worse with the Rogers - the midband seemed to
disappear, which made me wonder whether the supplied speakers are somehow
tailored to the frequency response of the unit.

The Rogers are pretty good speakers, though without any extreme bass.
There's some detail of the mark 2 he
http://www.mhennessy1.f9.co.uk/rogers/brochures.htm

It's possible that the Denon system has a frequency response tailored to
the supplied speakers. Maybe it has a loudness control (boosted bass and
treble at low volumes) that gives the effect of quiet midrange on good
speakers. Does it have some preset equalizer settings? You need to do
some measurements.

--
Eiron.