Kingshead: Sorry that I have to correct you again, but on the OMs the magnet is part of the body, not of the needle. B50 once disassembled an OM body to finally clear up that question, but unfortunately the photos in the particular thread over on VE got lost and B50 himself unfortunately also doesn't have 'em anymore...
Greetings from Munich!
Manfred / lini
As stated in my last post I pulled that from the interweb to save time, any incorrect info was already there. The point is still valid, LOMC designs having less mass attached to the cantilever and will react quicker to groove modulations and the reason they sound better for the most part. I have a Grado Platinum so am familiar with moving iron cartridges, there design is also to remove mass compared to MM, but still have more mass than a quality MC but with more usable output.
Martin
More from the interweb.
Moving Magnet & Moving Iron
In a stereo moving-magnet cartridge (MMC), a miniscule permanent magnet rests on the end of the stylus cantilever suspended between two coils—one for the left and one for the right audio channels (Fig. 5). As the name suggests, the magnet moves (vibrates) between the two coils and, in so doing, induces a small current in them. Since the magnet is extremely small it weighs very little, requiring a lower downward (tracking) force to accurately travel the record grooves.
5. The stereo moving-magnet cartridge design places a tiny permanent magnet on the end of the stylus cantilever, where it is suspended between two coils.
The only marked difference between an MMC and a moving-iron cartridge (MIC) is a tiny piece of iron or other light, ferrous alloy that replaces the magnet on the end of the cantilever (Fig. 6). In this case, the iron is lighter than the magnet, further reducing tracking force while boosting tracking accuracy.
6. Moving-iron cartridges are pretty much the same as moving-magnet types except that a piece of iron or other similar material sits on the cantilever.
Moving Coil
A moving-coil cartridge (MCC) uses an inverted moving magnet design (Fig. 7). The coils attach to the stylus cantilever, and the permanent magnet resides near the coils. Since space is beyond extremely limited, the coils are tiny, using extremely fine wire. This limitation on coil size results in an extremely low output, i.e., in the microvolt range.
7. A moving-coil cartridge basically reverses the moving-magnet design by attaching the coils to the stylus cantilever while the permanent magnet is positioned in close proximity to the coils.
With an output of around 100 µV to 300 µV, MCCs are very susceptible to noise and hum. In addition to an RIAA preamp, these cartridges require an additional amplifier stage or step-up transformer prior to the RIAA frequency-compensating preamp. There are, however, high-output MCCs on the market capable of delivering output levels comparable to MMCs.
Moving Micro Cross
A somewhat proprietary design patented by Bang & Olufsen and not a general consideration, the moving micro-cross cartridge is a spinoff of the moving-magnet/iron topology. During playback, a miniature metal cross ungulates between stationary coils and magnets in sympathy with the stylus. According to its inventor, the moving micro cross eliminates many magnet and coil mass concerns and exhibits far better channel separation because left and right channel motion occurs on separate axes.
The Great Debated
There is still a rather large market for phono cartridges that is both profitable and viable in terms of future developments. This market is truly passion-driven by knowledgeable and opinionated audiophiles, the curious novitiates who are venturing into the dark worlds of analog audio for the first time, and those who are both maintaining and expanding their investment in vinyl recordings.
Once audio aficionados and budding audiophiles have settled on a turntable, they have the daunting task of choosing the phono cartridge. Now this task is daunting only because of the abundance of choices and circulating opinions.
Move The Magnet, The Iron, Or The Coil?
Aside from their differing design concepts, MMCs, MCCs, and MICs each have their pros and cons. If one views them objectively, then it should be fairly easy to make a subjective purchase—maybe. But there is a bottom line, which we can save for last.
Any one of the three cartridge types does a fine job if it’s well designed and constructed, which is usually the case even in lower priced, entry-level components. They only require three things for competent electromechanical performance, i.e., performance up to their measured specs.
First, the cartridge needs a comparable turntable/tonearm. In other words, don’t slap a $40 cartridge on a $4000 turntable or vice versa. Second, the cartridge requires competent installation and alignment to manufacturer spec. Third, the cartridge requires a quality-comparable RIAA-compensated preamp, whether it’s in a receiver, integrated amp, or dedicated preamplifier/controller.
MMCs are generally simpler and less expensive to use than MCC designs. Electronically, they only need the phono preamp. Yet, as previously stated, the magnet placed on the cantilever exerts a bit more tracking pressure on the vinyl recording, which some users believe influences the playback’s sonic quality and incurs a bit more wear on the vinyl.
MICs resolve the tracking pressure issue somewhat because iron is lighter than the magnet. This also sets up debates about the quality of playback. Some listeners claim the moving iron is sonically superior to the moving magnet, while others claim the reverse or hear no difference at all.
Stated earlier, MCCs require a front-end amplifier prior to the RIAA preamp. This front-end amp is flat, not frequency compensated. This adds another layer of cost and a layer of installation complexity. But with cost and complexity come fruits. The moving-coil design requires less downward tracking force than either the moving-magnet or moving-iron components.
Perhaps because of the well-known pressure differential, a larger number of audiophiles seems to agree that the moving-coil approach is sonically the best. Getting them to agree on which moving coil is best is another story, which is a good thing in the grand scheme of market health.