I own a pair of M5si, two pairs of M3si and one pair of M1si. I had a pair of M5, which I sold to my neighbor.
Another forum member messaged me and asked me about the differences, so here was my reply:
They are all similar in the midrange and highs, the bass is where they all differ. Let me start with the Mirage basics in the line; I once had some Mirage M5's as well. They had the 3/4" soft-done tweeter. The si series has the 1" titanium dome tweeter. Some will tell you the older soft tweeter is best (hand matched, etc.) but I MUCH prefer the si series tweeter. It has more clarity and detail to my ears.
Concerning the M5si: The biggest difference (compared to M3 and M1) is that the M5si lacks a large woofer or woofers. It's biggest drive is a a pair of 6 (or maybe 6.5") drivers. For that reason, I always like to pair them with a good, fast subwoofer. It images almost as well as the other (M3si/M1si) speakers if you put the sub right next to the cabinet, but it doesn't "blend" as well as the M3si or M1si since they have built in woofers and you can cross them over with a sub (if desired) at a lower frequency (50 or 60 Hz) than with the M5si, where you must cross it over at around 80- Hz. M5si's have no foam surrounds; they are neoprene so you never have to worry about deterioration.
The M3si's are amazing. I own two pairs. The problem with the M3si's as well as the M1si's is the midrange...it has a foam surround, which deteriorates and falls apart over time. I installed new surrounds on BOTH my M3si pairs, and it made a huge difference, as the old surrounds were shot and were not suspending the midrange properly. Once I fixed the surrounds, the speakers became amazing. My M1si surrounds are still good, but I will replace them soon, as they are getting quite soft. It is not hard to do if you are mechanically inclined and can solder, and the surrounds are easily available on the internet. You can also hjave them "professionally" re-done.
The mid and upper frequencies in the M3si and the M1si are very similar, as the tweeters and midranges are identical.
The difference is in the bass and how it blends. The M3si has a single 10" woofer on the front of the cabinet and the M1si has a pair of woofers, one front and one rear, but they are 8" woofers. If you do the math on the surface area of the woofers, you get 78.5" for a single 10" woofer and 50.26" for each 8" woofer (100.5" total since each M1si has two), so the M1si has 22" more woofer surface area. The M1si plays flat (within 2dB) down to 25 Hz. The M3si plays flat down to 30Hz. The M1si does this by using both a larger cabinet as well as the increased surface area.
So...on to listening. Can you hear the difference? Yes you can. The M1si plays deeper and is tighter than the M3si, and your ears can hear that difference. That also makes sense because the 8" woofers are smaller and therefore faster. With that stated, the M3si, with its larger, single woofer, almost seems to my ears to accentuate the bass a bit more; I would not really call it "boomy", but it is not as tight and "sterile accurate" as compared to the M1si. I can see how some people's ears might actually like the M3si bass better, even though it does not play as deep and is not as tight and accurate. I like them all. Back when they were new, I can imagine a person listening to both and making the decision that they like the M3si bass as much (or even more) than the M1si, and also - knowing that they are cheaper - deciding that they are the best value. With that stated, the M1si's are so amazingly accurate, tight, detailed, and pleasant to listen to...and they play deeper, so for very detailed music like classical, vocal, opera, spanish guitar, jazz and other detailed music I would give the edge to the M1-si's over the M3si's. . For rock and roll, I think the M3si's are excellent, and in fact they excel in the other genres I mentioned as well, but a slight edge goes to the M1si's in all forms of music in my opinion. They are simply more accurate and detailed due to the smaller, dual woofers and bigger bass surface area of the drivers, which is what my ears prefer.
The M1si's are closer to a "full range" speaker than the M3si's are. I think rock requires a subwoofer with the M3si's...and in full disclosure, I run a pair of 1000 watt (each) 15" subwoofers crossed over at 50 Hz as I like my music full range with a very deep bottom end. If you get a chance to buy any of them at the right price, I say go for it. They are not fatiguing at all. In fact, for extended listening, I prefer them to my Goldenear Triton Ones. They are not as detailed in the highs as the GE's which are almost "clinical" in nature. Modern (lousy, compressed) recordings are terrible in the Golden Ears as they fatigue my ears, but the bipolar effect of the Mirages actually makes some not-so-good recordings sound tolerable. I hope that helps.
