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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
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
mid-fi-crisis
71 posts
 
Not sure if it's been mentioned already, and sorry if this is a dumb comment, but just check that the external fabric is not adhered to the speaker membrane anywhere. Often they're kinda stuck here and there and can release by themselves but sometimes don't.
That would deaden a panel. 
You'll know by looking side on to see if the fabric is flat or not.
mozartfan
2,143 posts
 
Are you sure there is not some snakeoil selling going  here?
jonboy
8 posts
 
I had a similar problem with my MMG's last year. I thought the tweeters were blown, however, I took a shot and tried this: I removed the binding post plate and found that the wires from the crossover to the plate were slightly loose. I tightened them up and they're back to normal. I don't know how this happened, perhaps through shipping. Either way, it might be worth looking into. Best of luck.

Jon
gkr7007's avatar
gkr7007
154 posts
 
Sounds to me like you set everything up right.  Those stock steel jumpers are junk.  Pass Labs have plenty of current to drive those ribbons.  Anticables work well with Maggies but maybe you just need more break in time.  You may try tilting forward a couple inches to see if that helps because what you are describing doesn't make sense.  I owned 1.7i's and used Anticables and their jumpers with high current amps and the one thing that was never lacking was upper ranges.  And don't be  influenced by measuring devices.  The two best ones you have are the ones on either side of your head.
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