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  • Martin Authentic Acoustic Flexible Core 13-56 Acoustic Guitar Strings, Medium
  • Martin Authentic Acoustic Flexible Core 13-56 Acoustic Guitar Strings, Medium

Martin Authentic Acoustic Flexible Core 13-56 Acoustic Guitar Strings, Medium

(6 Reviews)
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Authentic Acoustic / Flexible Core
Set gauges
13, 17, 26w, 35w, 45w, 56w
Wrap material
Phosphor Bronze
Round Wound
Core shape
Hex Core
Plain Steel
Number of strings
6 string
Optimal tuning
Plain wound 3rd
Wound 3rd

The idea behind these Martin Flexible Core sets is to have strings that sound and last as long as the standard SP’s but with a much softer, springier feel under your fingers. They should be easier to play for longer and easier to bend too!

This is achieved by using a thinner gauge of core wire and thicker gauge of wrap wire. Naturally this affects the tone a bit; adding a little extra low-mid warmth while rolling off the low-end slightly. The brightness seems to be smooth which I can only assume is due to offset of more bronze and less core. Good strings, and Tommy loves them (as you’ll find out below).


The blurb from Martin:

It isn't just about flexibility; it's about bending the note till it rings true. 

Martin SP Flexible Core strings have a thin but strong core wire and a thicker wrap wire which allows them to be flexible and easy on the fingers while holding standard tension. SP Flexible Core strings feel soft to the touch, making them ideal for beginners. But don't be fooled by comfort! Just ask Tommy Emmanuel who performs with Martin's SP Flexible Core strings night after night. With SP Flexible Core, you get total flexibility and total control.

Martin & Co. designs and manufactures the strings themselves. Like their guitars, each string is made with patience, care, and precision with only the highest quality materials producing strings with exacting tone and superior performance. Not only are their packaging materials minimised and 100% recyclable, but the envelopes reduce the tarnishing effect on the strings.


Re: Delivery. All orders placed on weekdays before 3:45pm will be despatched that same day.  All of our delivery options can be found at checkout or on our delivery page.

Re: Returns. We have a 30-day return policy, which means you have 30 days after receiving your item to request a return. To be eligible for a return, your item must be in the same condition that you received it, unworn or unused, with tags, and in its original packaging. You’ll also need the receipt or proof of purchase.

To start a return, please contact us at info@stringsdirect.co.uk.

For further information visit our Returns & refunds page.

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