It would be disappointing if the BHK 250 couldn’t drive Magnepan’s least expensive speaker. If the amp checked out after going to PSA. the next logical step would be to make sure there isn’t anything wrong with the speaker.
The memory is the first thing to go.
Glad it is not my hearing 
My B&W 800 Matrix are 4 ohm speakers they are quite efficient at 93 db per watt though. I do not know how low their impedance may drop to but I have no issues with the 250 driving them to deafening levels is so desired. Some speakers have terrible impedance drops and are difficult for many amps to drive. Paul has mentioned some infinity’s that used to kill amps. It the Magnepan LRS are that difficult to drive I would bet even the 300’s would not like them very much. I guess the choice has to be do you want a high quality amp or do you prefer to keep your speakers which really are nothing outstanding. The amp has protection circuitry for a reason.
And some speakers become particularly nasty to drive when pushed to play loud, more common among smallish speakers.
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With the LRS, it’s not about watts per channel, it’s about the type of power current. For instance, an entry level 60 watt Hegel can drive the LRS wonderfully, while a 1000 watt amp may struggle.
I agree. Iam driving the LRS now with a pair of Stellar M1200’s and they sound great.
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Really late to the show, but wanted to touch base on this subject as I’m kind of in the same situation as the OP, but not as bad.
As you may know, I’m running a pair of Schiit Aegir amps (Class A “Continuity”) amps in mono, which published on their site are only rated for an 8 ohm load mono at 80 watts. However, original spec sheet for the amp also confirms that these amps are in fact stable into a 4 ohm load in mono mode, producing 160 watts.
My Martin Logan SL3’s are nominally 4 ohms and rated at 89 dB @ 2.83v. They have phase and impedance swings that look like massive waves in a roaring ocean. All of these massive swings happen between 50 Hz - 8.5 kHz, right where 99% of the sound is happening. They dip as low as 1.5 ohms at 20 kHz which isn’t too much of a concern, not as much as all of the other things going on down in the meat of the audio spectrum. And that’s not including the fact that they actually measure in at 85 dB @ 2.83v.
To my amazement, the little Aegir amps handle the ML SL3’s quite nicely. They even getting plenty loud enough, more than I would ever normally listen to. However, there are only two times I’ve had my amps shut down, going into over current protection mode…
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Watching the movie “Underwater”… Very good movie I might add. My brothers were over and I had the volume up quite loud. The movie is one and a half hours long, and there’s plenty of near constant bass, explosions, crashes, etc, etc going on. It wasn’t until the last 16 minutes of the movie where there was a really large explosion that taxed the amps current limits and the went into protect mode, meaning all I had to do was switch them off from the back panel main switch, turn them right back on and everything was fine. And to even more amazement, the amps were no warmer than normal!
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Playing a jazz album, unfortunately I don’t remember which one it was. However, in the beginning of one of the tracks, there’s a light drub solo, and I turned up the volume some. It wasn’t even all that loud, yet it was just one little snare hit that made the right amp shut down. Again, just a simple flip of the main rear switch on the rear panel and all was good.
Anyway, my point, in my case, my amps shut down due to over-current draw (those crazy impedance and phase swings I mentioned above), and maybe to a lesser extent, over-power draw (from that explosion possibly), though never any distortion or signs of distress. Just super clean sound then nothing when the amps shut down.
With the BHK/LRS combo, it could very well be that the OP was pushing the BHK into clipping, making the amp shut down before damage to either. Since the Maggies are nearly a pure resistive load, they’re a nominally measured 3.3 ohms with a slight dip to 2.8 ohms between 400 Hz - 600 Hz, and that dip starts and ends between 100 Hz - 2 kHz, again, right in the meat of the audio spectrum. Depending on the current capabilities of the BHK, the Maggies could simply be pulling too much current from the amp, especially in that 2.8 ohm range, causing it to shut down. And because the LRS’ are so inefficient at 80 dB @ 2.83v, the power demands ramp up quickly when more is asked from them, even with 500 watts on tap. Those Maggies can easily soak up 500 watts without issue on peaks.
Now that the OP is powering them with more than double the power with the M1200’s, he has no issues. And I’m sure those monoblocks have more current capabilities as well.
I too was thinking about having to upgrade my amps, but considering the SL3’s get plenty load enough in my small room, and the amps down have any problems playing music and movies at the “normal” levels that I typically listen at, there’s really no reason to upgrade.
I don’t know if it was ever mentioned, but we don’t know what size room the OP was trying to fill, nor do we really know how hard he was trying to push them. I have more efficient speakers in a more than likely smaller room, so I can a reach higher SPL or the same with less power demands with a lot less powerful amplifiers.
So what I’m getting at is that the OP’s amp/speaker combo was just being asked too much to do, likewise with my system when I was playing it louder than I normally do. So nothing wrong with the BHK amp or LRS speakers, or my Aegir’s and SL3’s.
Anywho…
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The point is the BHK 250 is not to blame for poor equipment matching. 80 db per watt sensitivity is terribly low that combined with very low impedance dips is the real source of the problem. You need to drive speakers like this with a higher current output lower performance amp. Why would one want to use inexpensive speakers on a $7500 amplifier? There are many speakers out there that will be much more capable of allowing one to hear what the BHK250 is capable of doing.
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A lower performance amp?
What I mean is an amplifier that was designed for the purpose of driving difficult loads as a priority over sound quality. The BHK 250 is designed for sonic performance. It does have good current drive capability into 4 ohms and is stable into 2 ohms. Some speakers have impedance issues that challenge the protection circuitry or in some instances threaten the output stage. Paul has mentioned some Infinity’s that were amp killers.
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I wonder which ones those would be. LOL
I wouldn’t say all high current amps are lesser in sonic performance. Well maybe “average” price ones are, but the good ones that can do both?.. Yeah, those are something like the big Mark Levinson’s and such at $30k a pair.
Who can afford a $30,000 amp clearly not someone running $600 hard to drive speakers.The BHK 250 is no slouch it drives my B&W 800 Matrix with ease they are 4 ohm nominal and I am sure at some frequencies they fall to 3 ohms or less. The key is not to design speakers with super low sensitivity that suffer from extremely low impedance swings that occur right where allot of energy occurs in the music.
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I suspect a part of the problem is people trying to get more sound out of the LRS than they are designed to produce.
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That’s pretty much what every magneplanar design is, as well as most all electrostatic designs as well. There’s an amp for every speaker. And if you have to compromise, then learn the limits of your setup and keep things below that limit.
Exactly what I was getting at in my post.
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Agreed, Elk.
I’ve been using Maggies since the 1970s and am currently using LRS speakers with PS Stellar M700 amps. Work and sound great together. IMHO, the LRS is by far the best entry level speaker Magnepan has ever made.
Bigger Maggies will play louder because the panels are larger and thus move more air.
Shoot, while I was waiting for the M700 amps to arrive I used a Sprout100, McIntosh MC-30s and Dynaco Mk. IIIs all with good results on the LRSs. I don’t listen at extremely loud levels.
If you want loud, the LRS is not the right speaker. It is not alone in that regard. The same can be said for Rogers LS3/5a, KEF LS50, and Quad ELS speakers. Doesn’t mean they aren’t great speakers, just not made to play loud.
BTW, I’ve had no reason to measure the impedance of the LRS, but Maggies have historically been known to present a pretty static and stable impedance load to an amplifier. Most amps are much happier with a static impedance load rather than driving a speaker with wild impedance changes. Of course, over driving any amplifier or speaker is guaranteed to lead to a less than optimum result.
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Yeah, the polar opposite of my Martin Logan’s, ranging from nearly 16 ohms all the way down to 1.5 ohms. An amplifier’s dream… LOL
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I have a pair of M700’s driving the 97db Sonist Audio Concerto 4 which average 8 ohms and at worst dip to 6 ohms. The M700’s have never come close to shutting down 
It’s not the speaker that has the problem in the combination, it’s the bhk250. Stop making excuses for it.
This is proven by user statements that more budget PSA amps like m1200 and m700 can handle the LRS just fine.
Doesn’t mean the bhk250 is a pile of junk, but just admit it can’t adequately drive the LRS and move on. So it’s not capable of driving that speaker - Ok, but don’t blame the speaker.
I’d be hesitant to blame either component without first testing each one with different partners - like the BHK with a different speaker, or the LRS with a different amp. See how they each fare under different circumstances, and then draw conclusions. I suspect what you would learn is that neither one is “deficient” in any way - they may simply not pair well together. No one amp is all things to all people (or all speakers), and neither is a single model of speaker all things to all amps.
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I agree about the pairing being incompatible.
But in a speaker/amp relationship, it is customary to pick the speaker you want (everything derived from the speaker - most important), and THEN consider appropriate amps for that speaker.
In this case, apparently the bhk250 is incapable of driving that speaker, per the reports. So choose a different amp.
And if the bhk250 is incapable of adequately driving the LRS, sorry but it is deficient with regard to that speaker. It’s fine for many other good speakers (and deficiency with regard to LRS won’t detract from compatibility with these other speakers), of course, but that is not the subject of this thread.