For owners of Music Reference RM-200 power amps, a bit of clarification: Al's input impedance figure for the amp is correct for only the original incarnation of the amp---30kHz balanced, 15k per leg. In the Mk.2 (current) version of the amp, RM-200 designer Roger Modjeski increased the figure to 60kHz, 30k per leg. That's better for use with some tube pre-amps, which often have somewhat higher output impedances than most solid state pre's.
Passive high pass filter - Marchand XM446XLR-A
So, I am about to set up a new pair of monitor speakers and fill in the lower frequencies with two subs. The monitors are Aerial LR5s and the subs will be two Aerial SW12s with internal 400 wpc amps. The LR5s weigh 105 pounds each and play flat to just a bit above 40Hz (-6dB at 35Hz). The Aerial subs are fast, powerful and musical and should integrate well with the LR5s. My pre and power amps are solid state, fully balanced and the power amps provide 300/600 wpc into 8/4 ohms. I will be running separate ICs from the preamp to my power amps and a second set from the preamp to the input on the subs.
My first question is whether I would benefit from using a high pass filter between the preamp and amplifiers to limit the low frequencies going to the LR5s so the amps are not trying to drive them full range.
I didn't find a DIY design that I was comfortable with but I did run across several posts by people using a Marchand passive high pass filter. The Marchand XM446XLR-A is fully balanced and has a high pass corner frequency of 80Hz (i.e., the frequency that is down by 3dB). The Marchand has a standard slope of 24dB/octave but can be made for other slopes.
My second question is whether anyone out there has experience with the Marchand passive high pass filter and is it sufficiently transparent or should I expect to hear unwanted artifacts with the filter in my system?
Finally, is there a higher quality alternative or should I simply play with the low pass on the sub and forget about filtering the signal to the main speakers?
http://www.marchandelec.com/xm46.html
My first question is whether I would benefit from using a high pass filter between the preamp and amplifiers to limit the low frequencies going to the LR5s so the amps are not trying to drive them full range.
I didn't find a DIY design that I was comfortable with but I did run across several posts by people using a Marchand passive high pass filter. The Marchand XM446XLR-A is fully balanced and has a high pass corner frequency of 80Hz (i.e., the frequency that is down by 3dB). The Marchand has a standard slope of 24dB/octave but can be made for other slopes.
My second question is whether anyone out there has experience with the Marchand passive high pass filter and is it sufficiently transparent or should I expect to hear unwanted artifacts with the filter in my system?
Finally, is there a higher quality alternative or should I simply play with the low pass on the sub and forget about filtering the signal to the main speakers?
http://www.marchandelec.com/xm46.html
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- 18 posts total
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Thanks Eric (bdp24). I’m wondering, though, if the change you referred to from 15K/30K to 30K/60K might have been introduced sometime after the Mk.II was initially marketed. The Stereophile review I referred to indicates in numerous places that it is a review of the Mk.II version, and describes various changes and improvements that were made relative to the original version. The photo of the amp on the first page of the review also shows "RM-200 Mk.II" as being marked on its panel. As I mentioned, that review indicates a measured balanced input impedance of 29K (JA’s measurements of balanced input impedances always represent the sum of the two legs), and also indicates a spec of 15K ("one leg driven")/30K (balanced). Also, Roger’s website still indicates 15K/30K, although he has not updated the amp's description to say "Mk.II." Best regards, -- Al |
FWIW, I have used one of Marchand Electronics’ active crossovers here in the home office for over 8 years. This unit is the XM66, which has a variable crossover frequency (user variable, no cards/"inserts" required). I can’t hear this device when it’s in the circuit--it makes zero noise and has no noticeable sonic effect. But I certainly hear what happens when it’s not in the circuit (ie, when the big 2-ways on desktop [currently the Harbeth 30.1s] overlap frequencies with the JLAudio e110 sub). Let’s just say the crossover makes every clearer, more distinct, and more settled. Other than that, I’m hardly an expert on crossover. Never tried any of the others, nor have I experimented with passives. Very happy with the XM66 and wouldn’t hesitate to recommend it. |
- 18 posts total