The Martin Acoustic SP line of strings is great, and not just for your Martin guitar. They will also sound excellent on your Yamaha, Takamine, or Taylor just the same.
Not only does Martin make outstanding guitars, but they also apply the same talent and care when constructing their strings.
The construction on these strings is pretty standard. It is available in two configurations, specifically an 80/20 bronze and a 92/8 phosphor bronze.
They have a standard steel core, with a bronze or phosphor bronze wrap wire. In this case, as is the status quo for Martin, there is elegance in simplicity.
There is nothing groundbreaking in terms of the way these particular strings are made.
Martin relies on high-quality materials and old-fashioned attention to detail, and as per the usual, it works for them. There are no special coatings or fancy gimmicks; these are just good solid strings.
My first thought when playing these strings is that they are very well-balanced.
They don’t accentuate the bass or the treble too strongly. They have a rather bell-like sound when strumming softly, but if you lay into them they will reward you with a little bit of twang and snarl.
In terms of brightness, the bronze and phosphor bronze is about right for their respective niches.
These strings are tonally comfortable for playing a variety of genres and styles from mellow jazz to gritty blues. If you are a very niche player that tends to play only one guitar style exclusively, you might find these a bit too nondescript for your taste.
They don’t really lean any certain way such that I could recommend them for one specific style of playing. Because of their well-balanced nature, they will essentially maintain the natural tonal tendencies of your guitar body.
That is to say that if your guitar body emits strong bass, these strings won’t compensate and reduce this in relation to the treble, and this is similarly true for guitars that naturally have strong treble.
These strings have a middle-of-the-road lifespan.
They do pretty well for bronze, but can’t compare to a coated set. The plain bronze degrades a touch quicker than its phosphor bronze counterpart, as is to be expected.
When comparing the two, the tones are similar enough that I would opt for the phosphor bronze over the normal bronze due to the fact that they will last longer.
As mentioned previously, the Martin Acoustic SP Strings can be had in standard bronze or phosphor bronze.
They are also available in a variety of sizes ranging from the typical extra light through to medium, in addition to some interesting hybrid string choices such as custom light, high tuning, and bluegrass.
You can also get these strings for a 12 string guitar and an acoustic bass.
All in all the Acoustic SPs are a well-rounded set of high-quality guitar strings.
They are middle of the road tonally and from a longevity perspective. They are relatively inexpensive and represent a good value.