Round core vs hex core guitar strings
Most guitar players have heard the terms round core and hex core. Fewer players know what those words mean, and fewer still know why it changes the way a string feels under your hands.
The difference is simple. It refers to the shape of the steel wire at the centre of a wound string. That hidden piece of wire carries the tension. The wrap wire is wound around it. The shape of that core affects how the wrap wire grips, how the string settles, how it responds to bends and vibrato, how it ages, and how annoying it is to manufacture properly.
A round core string uses a round steel wire at the centre. Because the wrap wire is sitting on a smooth cylinder, the string can have a little more flexibility along its length. When it is made well, the core and wrap can settle into a more even relationship under tension. Players often describe round core strings as smoother, more responsive, more open, and richer in harmonic content. That is not magic. It is mechanics.
A hex core string uses a six-sided steel core. The corners of the hex shape bite into the wrap wire and help lock it in place. That makes the string easier to manufacture at speed, easier to handle, and more forgiving when players cut the string during installation. Hex core strings often feel tighter, stiffer, more immediate, and more focused. In heavier gauges and lower tunings, that can be a very useful thing.
This is where people get weirdly loyal. Round core is not automatically better. Hex core is not automatically better. They do different jobs.
Round core can give you a smoother feel, easier bends, a less rigid response, bigger bloom, and more harmonic overtones. Hex core can give you more mechanical grip, a sharper attack, tighter control, and a more dominant fundamental.
I like round core for almost everything. The exception is the lowest string on a drop-tuned metal set, where a hex core can help keep the low end tighter and more controlled. If you are tuning down to C# or lower and hitting hard, that extra grip can be your friend. This is what we have started doing in in our SONIC MAUL drop tuned strings.
The right answer depends on the string, the guitar, the tuning, and the player.
At the same gauge and tuning, the measured tension is mostly governed by physics. Scale length, pitch, and string mass do the heavy lifting there. What changes is feel. A round core string can feel more flexible even when the tension number is similar. That matters because players do not play tension charts. They play guitars.
Manufacturing is where round core gets interesting. With a hex core, the corners help hold the wrap in place. With round core, the maker has to do more of the work. Winding tension, wire condition, handling, and the final twist all matter. If you wind it badly, the string will tell on you. Round core rewards careful manufacturing and punishes lazy manufacturing. That is part of the appeal.
There is also an aging argument. A round core gives the wrap wire a continuous surface to sit on. A hex core has alternating high points and small spaces created by its shape. Those spaces can give moisture and contaminants somewhere to hide. That does not mean every round core string outlives every hex core string. It means the interface between the core and wrap matters, especially once sweat, humidity, and time get involved.
This is one of the reasons we use zinc-plated high-carbon steel core wire. The core is hidden, but it is not secondary. Zinc plating gives the steel a more corrosion-resistant surface, which helps slow aging where players cannot see it: under the wrap. We also care about the surface quality and consistency of that core wire because the wrap wire needs a clean foundation. The string starts at the centre, not at the package.
The goal is not to win an argument about core shape. The goal is to build the right string for the job. Sometimes that means round core. Sometimes that means hex core. The player should feel the result, not the marketing argument.
Pro tip: If you have not used round core strings before, there is one important installation detail: do not pre-cut a wound string unless you put a bend in it first.
Round core strings do not have the sharp edges of a hex core to mechanically lock the wrap wire in place. That is part of what gives them their feel, but it also means the wrap needs to stay secured during installation. If you cut a wound round core string before it is bent, tensioned, or locked at the post, the wrap can loosen from the core. Once that happens, the string is done. Tiny, expensive lesson.
If you mess up your first round core install, don't panic. Our no-fault warranty has you covered. Tell us what happened and we will send you a replacement. We would rather help you get it right than leave you annoyed at a good string.
I have not made a 6ix String installation video yet, but this one demonstrates the correct process well.
— Vincent Danger
