Magnepan 1.7 too bright, HELP

sorry, audioconnection, thats not science. A resistor in series will cause a dB drop thats fairly flat between the crossover point and natural frequency roll off of the tweeter. That means you are using a resistor as an equalizer. If a room is reflective, you kill the reflection with wall hangings, not damage the tonal balance of your speaker.
Calling it bright is a misnomer... its a new level of detail and unfortunately exposed in that detail is distortion thats irritating and which can distract your attention from the additional good you hear until you clean the cause out of your system.

for what its worth, I auditioned the 1.7's with the Rogue Chronus last month. Blissful musical, no listening fatigue factor with musical detail popping out all over. Could be that's all the cure you need

Everyone and his uncle knows that Maggie speakers require lots of current. Anticables are too thin to carry the required current.

Also, regarding the alleged brightness, I have heard 1.7s and believe it is NOT a level issue, it is the effect of the tweeter being much faster than the midrange/bass panels. Not much that you can do to alleviate this problem. Attenuating a fast tweeter with a series resistor will not make it slower, it will still arrive early as compared to the midrange, though attenuated.

I agree with the posts about improving your source. After the music signal gets out of your source, nothing can improve it. Colorations, distortions, time smear and undue emphasys are added by each and every component in your system, including the room.
So, my sure-fire bets would be start with the right source and dampen the room reflections.
Good luck

Try to use Class A amplifier w 100 watt for your 1.7. The Threshold 400A is a very good amp as recommended by HP. I had it once several years ago. I still miss it. Good luck.

I went through same issue. I listened to them through high end ARC tube amps in my dealers showroom. Loved them. Purchased the 1.7's with a new ARC LS17 and brought a pair of BelCanto M3 mono blocs home with them for demo. I hated the sound when I got home and set up. I then went to my other local dealer and purchased a new Bryston 4B SST2 to try with the 1.7's. 10 minutes after installing the Bryston in place of the BelCanto's I loved the sound. The bass was so much warmer and more natural and the highs lost the artificial sheen I was hearing with the class D amps. I also installed two absorbsion tubes in the corners behind the speakers. Everything sounds wonderful now. These are amazing speakers if paired with a tubed pre and a high quality and potent SS amp. As others have made clear, they will show you any mismatches or weak links in your audio chain rather quickly.