What’s the difference between a hex core and a round core string?

GHS Roiund Core strings laid on relic'd Fender Stratocaster

Today, electric guitar and acoustic guitar string sets comprise of a mix of plain steel strings and wound strings. Plain steel strings are simply one piece of cylindrical steel wire running the entire length of the string. However, when we refer to strings that have a central core, we’re referring to the thicker ‘wound’ strings. These strings are (in almost all cases) made up of two parts: a central core wire and an outer wrap which travels around the core. This central steel core wire can come in two main shapes: hexagonal shaped and round shaped (or more commonly referred to as hex core and round core). But what’s the difference? Is there a difference? How do they compare in playability and sound? We’ll try and tackle all these pressing questions below to help improve your ‘core knowledge!’

Round Core Strings

If we were to slice through a round core string, you’d notice that the core is (as the name suggests) round shaped. Because of its smooth edge the outer wrap wire travels around the core and remains in complete contact with the core’s entire surface.

“That’s great, but what exactly does this mean from a tone and playability standpoint?” we hear you ask. Well, because these two components are in complete contact, when you strike the string and it vibrates, the core and wrap wire move ‘as one’ which gives a nice flexibility to the string. We liken the core and wrap wire of a round core string to two professional salsa dancers… both in sync with each other, they move with a lot of fluidity and flexibility. Another advantage this property gives is that when you strike the string, this “togetherness” delivers a big, boomy tone.

Above: The outer wrap wire remains in contact with the entire surface of a round core string.

Many years ago, strings were exclusively wound over a round core, however, in recent times hex core strings have become the most popular choice for most string manufacturers. Despite being less favourable, round core sets are still available today from brands including Thomastik, Pyramid, Martin and DR strings. In fact GHS Boomers (the company’s flagship electric string line) are constructed using round cores too. This is actually quite unusual as most of the sets on the market today utilise hex cores…

Hex Core Strings

As you will have probably guessed, instead of being circular, the core of a hex core string is shaped like a hexagon with 6 sides and 6 corners. Because of its shape, the outer wrap wire doesn’t make complete contact with the core’s entire surface, instead it digs into its corners.

Above: As you can see the wrap wire only makes contact with the hex core’s six corners rather than being in complete contact with its entire outer surface.

This gives the outer wrap wire and the core a “tighter” bond which makes the string feel slightly stiffer but also gives the string a brighter tone.

This tighter grip also means that hex core strings benefit from greater tuning stability. That’s not to say round core strings inherently have tuning issues, however, on the whole hex core strings do tend to stay in tune a little better. In fact, GHS state on their website that “round core strings need larger core wire diameters to equal the same amount of stability and strength as hex cores”

Elixir acoustic string pack - hex core illustration

As mentioned earlier, hex core strings are more or less the norm nowadays when it comes to the manufacturing of guitar strings. Most of the popular brands including D’Addario, Ernie Ball, Elixir and Rotosound favour a steel hex core for all of their strings whether they be for electric guitar, acoustic guitar or bass guitar and there is good reason for this.
As you can imagine, for manufacturers the benefits of increased tuning stability is a massive advantage, not to mention, the production process for round core strings is more time consuming so hex core strings have also helped improve manufacturer’s efficiency too.

If you’re not sure whether a set of strings has a hex core or a round core, be sure to check out the listing on our website as we specify this attribute on each of our sets.

Hex Core / Round Core property displayed on Strings Direct website

Don’t trim too early!

Being made aware of when to trim your guitar strings is something that may seem unrelated to a blog explaining the differences between the types of core, however, it is quite a significant matter.

As explained earlier, hex cores ‘grip’ hold of the outer wrap wire much tighter than a round core guitar string does. So, if you were to trim a hex core string the wrap wire is able to maintain its strong hold on the inner core and therefore its ability to stay in tune effectively.

However, when you trim a round core string, if care is not taken, the tension holding the core and the wrap wire can easily be lost and as a result these two parts become detached from one other. Tonally the string sounds ‘dead’ and unfortunately this cannot be recovered and therefore a new string will be required. When these two parts do become detached, we’ve seen instances where you can actually slide the winding up and down the length of the string, almost like a sock running over the core.

Trimming the string correctly is particularly significant for players with instruments that have slotted (vintage style) machineheads. These machineheads require the string to be trimmed prior to winding them around the post. So does this mean that you can’t use round core strings on guitars with these machineheads? The answer is actually no, you can use round cores, you just need to be mindful to take an extra step prior to fitting your strings. So rather than just trimming your string at the desired point, before you do this, be sure to bend the string at 90 degrees and trim the string about 1 inch beyond this point. This bend maintains the tension between the core and wire ensuring it doesn’t slip when the string is trimmed.

So it’s a case of ‘bend then trim’ not ‘trim then bend’ when it comes to round core strings.

Trimming round core strings before fitting

As you can see there’s a little bit more to cores than initially meets the eye. Both types of strings certainly have their advantages and individual quirks and you may find that one particular type lends itself more to your style of playing. Although there is a far greater choice of gauge and wrap material on the market when it comes to hex core strings, round core strings certainly offer something different in terms of feel and tone so it’s certainly something worth exploring further.

Be sure to check in with us next time where we’ll be talking more about cores and in particular the ratio in size between the central core and the outer wrap wire.

Thank you so much for reading our blog in 2018 and thank you for all your comments. We always love to hear from everybody and look forward to writing more this year. Happy New Year from all of us here at Strings Direct.



  • Michael Neve

    Very well explained & interesting,well done,Happy New Year.

    • stringsdirect

      Thanks Michael, Happy New Year to you too 🙂

  • Bruce Gill

    Really interesting! Thanks for the info. Always wondered about round core. Think I’ll try some. I’ve been using EJ16s or John Pearse 600L…

    • stringsdirect

      Both great sets Bruce. If you’re looking for some round core acoustic sets DR, Thomastik and Pyramid make some round core sets worth trying. Will be interested to see what you think.

  • Terry Lewis

    Interesting article! I never paid attention to the core before. Intrigued to try some round cores now.

    • stringsdirect

      Hi Terry, good to hear from you. Sure, let us know if you wanted to try some and we’ll happily help out. GHS are always a good set to try first. Speak soon. Thanks. Lee

  • Red Baron

    Thanks Guys,
    An interesting and useful article, by halfway through you had almost got me converted to the concept of round core strings.
    However, on reading the piece in it’s entirety I’ve decided to stick with hexagonals. Keep it coming!

    Red Baron

    • stringsdirect

      Hi Red, was it the potential tuning issues that put you off? Granted, they’re not to everybody’s tastes. Thanks

      • Don Ramsburg

        Ive been searching low and high for the right roundcore strings.. I want my epiphone dc pro to be happy so instead of tuning down (drop A) and using THICK strings (wich is where i believe i fell in love with roundcores, dean markley nickelsteel 13-56 to be exact, boy they felt and sounded perfect) ive opted to get 9s or 10s and and stay in drop D to save my guitar neck lol.. Could you point me in the right direction? My studys are never conclusive and my guitar clerk cant stop scratching their head either. Thank you

        • stringsdirect

          Hi there, if you are tuning down to drop D abd wish to use 9’s or 10’s, you probably would want to opt for a 9-48 gauge. The GHS Thick Core Boomers are a round core set that may be of interest. Otherwise if you wish to go heavier, the 10-52 set may be something to look at. Here’s a link to some 10-52 round core sets. It’s worth noting that Hex core strings would certainly help stability if you are tuning down but of course, see how you get on with the round cores and play it by ear from there

  • Steve John George

    Straight to the point. All good stuff, no padding out on your articles to make them look more academic, cheers. Steve.

    • stringsdirect

      Haha thanks Steve. Our first drafts often need a bit of editing for this reason 😉

  • Baz Klarnett

    Very interesting. One learns something every day.

    • stringsdirect

      Thanks Baz, Happy New Year to you

  • Steve

    What’s the shape of flat wound core then of flat wound strings ?. Also what’s the best use of flat wound, eg can the be used on an acoustic guitar as well as solid or semi hollow guitars. This is an interesting subject so thanks for the information. On a similar note, I string Tennis/ Squash / Badminton Rackets, now that a mine field too Steve

    • stringsdirect

      Hi Steve, the shape of the core on a flatwound string varies according to the manufacturer. For instance, D’Addario will use Hex on their flatwounds whereas Thomastik use round…I think that’s what you were asking? Let me know if this hasn’t answered your question.
      Flatwounds can be used on acoustic guitars. Ideally you’d need a bronze set and again D’addario make a set specifically for acoustics called Flat Tops. You can see them here; https://www.stringsdirect.co.uk/search/eft1
      Can’t help you out on the Squash Rackets I’m afraid haha. Hope this all helps. Lee. SD

  • Don Dickson

    Interesting, as a person who uses Gibson strings on my LP what should I make of this description “Gibson Humbucker strings utilize a special composite core wire and a specially formulated wrap wire. “?

    • stringsdirect

      Hi Donald, this description baffled us too when trying to decipher what shape the core was. We’re still unsure, but, if we were to guess we’d say hex core…just a guess though!

  • Steve

    I use Martin SP light and after reading this article checked the core ( round ) I love them, for me they are better than Elixir ( only my opinion ) I use them on my Taylor 514 and Several high end Takamine’s. I have the Elixir on my Tom Anderson that it came with, but I’ve never played it. I also have a Yamaha sa2200 brand spanking new, they are for my retirement if i live that long. So the question is, do Martin or anyone else make hex core bronze acoustic sets ? Steve

    • stringsdirect

      Hi Steve, I actually believe that the majority of the Martin sets are wound over a hex core. Their Retro sets, Silk and Steel, Silk and Phosphor and Titanium Core sets use round cores. Btw, definitey start playing that Tom Anderson. I’m sure you’ll love it. I have a Hollow T, absolutely fantastic!

  • Jim

    I play my guitars for fun and often wonder what was meant by hex and round string.
    Now I know, very well explained.

    • stringsdirect

      Thanks Jim. Happy New Year to you. All the best

  • stringsdirect

    We’ve had an interesting e-mail from one of our good customer’s Chas who also had this interesting information to contribute. Some of you may find this info useful;
    “Piano strings and other classical strings have been round core for centuries. This article may be of interest. https://pianopricepoint.com/mapes-piano-string-company-how-piano-strings-are-made/

    Piano strings are expected to have far greater tuning stability than guitar strings, which is why they use roundwound

    The reason that guitar string manufacturers switched to hex core was that it made it easier to manufacture strings and there was a lower percentage of dud strings failing to get through quality control. Hex core vs round core was nothing to do with tonality differences and all about making strings cheaper to manufacture.

    For the same wound string gauge a string with a round core would be expected to have lower tension than a hex core string (as you note). This makes it slightly easier to bend and also means that you can go up to a slightly thicker string gauge in round core and have the same feel as a thinner hex core string. This then means that you have more mass moving in the magnetic field over the pickups which generates a higher electrical output from the pickup.

    The real downside of hex core vs round core for guitarists (or any situation where the player’s skin is in direct contact with the strings – unlike a piano) is that sweat and body oils from the skin and string cleaners (like Fast Fret) permeate between the coils of the outer wrap of the wound string and accumulate in the voids around the hexagonal core. Crud builds up inside the string, which can’t then be cleaned and the string goes dull more quickly than with a round core string, which doesn’t have those voids for muck to build up inside.

    Pre hex core strings were always round core. If you go back to the early days of the Beatles, Paul McCartney was known to have cut piano strings out of an old upright piano in Hamburg to restring his bass”

  • Tom

    I have the retro monel Strings on my Martin 000-17 which were factory installed. Since then I bought a new Martin 000-28 that has the same neck as the 000-17. I had the 17 set up when I bought it but wasn’t able to do that with the 28 because of Sweetwater being short handed because of the virus lockdowns. I love the way the 17 plays. The 28 seems a tiny bit harder as far as playability. The sound is immensely different but that’s attributable to the rosewood b/s as opposed to mahogany on the 17. After reading your article I’m inclined to try a set of models on the 28 or at least round wounds. Have a set of silk and steel. May try them. Thanks for the info

  • Really interesting article so thank you. I was about to order new strings for my mandolin from Newtone and they offer both round and hex core which foxed me…for a moment. Now I know what I am asking for?

  • Many years ago I (unknowingly) put a new set of hex core strings (same gauge as usual) on my main gigging bass. After the first gig with those strings (and subsequently) the finger tips of my fretting hand hurt. I had not experienced this before. So I checked the string type and found it was hex core. Since then I am much more aware of the core types and almost always (continue to) use round cores.
    There are a few points in your article that allude to why this is so, e.g. where you say “makes the string feel slightly stiffer”.
    Thanks for your info.

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