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My New Magnepan 1.7i's sound dull and lifeless on the top end...why?

First time Magnepan owner - 5  days old 100+ burn-in hours on them
Associated Equipment:
-Denafrips Terminator Plus
-Holo Audio May KTE version
-Pass Labs X22 Pre-amp
-PrimaLuna EVO 400 Pre-amp
-Pass Labs XA100.8 Monos
-PrimaLuna EVO 400 Monos
-AntiCables interconnects and speaker cables
-Stock tweeter attenuator jumper replaced with AntiCables level 5 spade jumpers on the 1.7i's

My spectrum analyzer indicates both speakers highs are falling off beginning at 1.25K and are 9db down from 2.5K on
Been playing around with speaker placement and room treatments for 2 days now without any remediation. What am I missing? Suggestions appreciated.
128x128nayls02

Showing 1 response by georgehifi

georgehifi's avatar
georgehifi
10,312 posts
 

nayls02 OP

The 1.7I is said to be the same evil load in the HF as the 1.7 with very low impedance combined with high -phase angle makes for nasty EPDR loading.
https://hometheaterhifi.com/wp-content/uploads/2011/09/magneplanar-1.7-speaker-impedance-phase.gif

I wouldn’t expect tubes to have much up there they will sound very rolled off. And Class-D won’t like it either.
Amps to look at are ones that have the reputation for not even breaking a sweat into that kind of loading.
I can think Krell for sure and I’m surprised the Pass mono’s didn’t work a bit, but they are Mosfet, and not quite as muscle bound into those loads as a bi-polar (bjt) Krell.

Cheers George
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