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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
nayls02's avatar
nayls02 OP
17 posts
 
russ691,216 posts07-29-2021 12:28pmI just wanted to add, make sure your banana plugs are not inserted too far. They can sometimes foul some wiring or reach the panel. Also take a flashlight and look at the wiring near the crossover and see if you see something disconnected. I seriously doubt both panels would be a problem but it is possible that a new guy mis-wired them.  
Apologies for the delayed response. We have a winner! Banana plugs were inserted too far. Backed them off a 1/8", and the magical highs appeared. I must say, these Maggie's deliver incredible musicality and detail. 

Thanks again for all the suggestions and the fix from russ69.
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
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