7 and 8-String Guitar Care: Extra Strings, Extra Tension

What Actually Changes on a 7 or 8-String

A 7-string adds one extra string past standard tuning (usually a low B); an 8-string adds two (B and F#). Each extra string means more total pull on a neck and body built for six, so relief drifts faster, fanned-fret models need per-string setup instead of one relief number, and a pickup calibrated for six strings can leave the extra string uneven in volume.

What the Extra String Actually Does to the Neck

Adding a seventh or eighth string doesn't just add a note to reach for — it adds another string's worth of tension pulling against a neck that's often the same size as a six-string's. It's the same arithmetic behind why a 12-string's total tension runs roughly double a six-string's on a similarly sized top, just a smaller jump: one or two more strings' worth of pull instead of six. Smaller doesn't mean free, and not every guitar in this category was engineered around the total from the start — some are closer to a six-string neck with an extra string added than a neck sized for the load it now carries.

Wikipedia's entry on the eight-string guitar ties the instrument's characteristic tuning problems partly to exactly that kind of construction shortcut: "The main design issue faced with an eight-string guitar is tuning stability with the lower strings. This is due to the neck being constructed too short, bridge problems such as improper intonation, uneven spacing for floating bridges, or the use of wrong string gauges." None of that is something a player causes, but it means the low strings are where a rushed setup shows up first — and where a generic six-string check is least likely to catch it, since there's nothing in a standard procedure that singles out the added string for extra attention.

In practice, that means checking relief every time you change gauge or tuning, not on the seasonal schedule our string gauge guide describes for a single jump on a six-string. The extra string leaves less margin before a small shift in relief turns into buzz on the string already carrying the most load. Our DIY setup guide covers the feeler-gauge procedure itself — nothing about the mechanics changes here, only how often it's worth running and which string to check first.

Fanned Frets: One Relief Number Doesn't Cover the Neck

Many 7 and 8-strings use a fanned-fret or multiscale board, where the bass strings run a longer scale than the treble strings instead of one straight scale across the neck. Strandberg's explanation of the design is direct: "The solution is to create a multi-scale instrument, where each string has its own scale length," built by laying the frets "in a fanned manner." Their Boden 8-string spans a 28″ scale on the low string down to 26.5″ on the high string — a difference big enough that the truss rod still works as a single rod, but the string-to-string setup no longer does.

Wikipedia's entry explains why builders bother: multiscale construction "helps with proper intonation of the lower strings, improves string tension balance across the strings, improves harmonic overtones, overtone series, and improves inharmonicity," and it changes the intonation math specifically, since "the bass strings on an 8 string typically require the saddle to be pulled back a bit more than the other strings to properly set the intonation." Harley Benton's rundown of the tension side explains the payoff: because the longer bass scale keeps low-string tension closer to the shorter treble scale's, "since all the strings have consistent tension, pressing down on the notes, as well as bends and vibrato, feels consistent across the different strings" — and a detuned low string benefits specifically, since "the added tension allows for tighter detuned notes, offering a cleaner definition and note clarity."

None of that averages into one number you can set once and trust across the neck. Our setup guide's feeler-gauge procedure still applies, but on a fanned board you're running it string by string, and the 12th-fret octave check for intonation has to happen on every string rather than a representative one or two — the whole point of the design is that each string is its own small setup problem.

Pickup Height Needs the Same Per-String Attention

The same logic carries over to pickups. Our pickup height guide covers the standard starting point — roughly 3/32″ from pole to string, measured separately on the bass and treble sides — but that guide is written assuming those two reference points are enough to judge everything between them. A 7-string has five strings between those two edges instead of a six-string's four, and an 8-string has six — and a pickup built around six-string pole spacing doesn't always spread its magnetic field evenly across the extra width.

Polepieces exist for exactly this. As one pickup-height guide puts it, "by adjusting each screw pole, you can balance the output of each individual string," raising them "into an arc matching the string radius" so the gap between each string and its pole stays even. Checking only the two outer strings and assuming the middle ones fall in line skips the check that matters most on an extended-range instrument — the added string is often the one that ends up over- or under-adjusted, without a symptom more specific than "this one string sounds a little different."

Why Generic Six-String Advice Falls Short Here

Every piece of this points the same direction: a 7 or 8-string isn't a six-string with extra notes, it's an instrument where relief, intonation, and pickup balance all need to be checked per string and more often, not read off one number that worked on a smaller neck. A fresh set and a feeler gauge handle the mechanics; what actually changes is the habit of checking the added strings specifically instead of assuming a standard setup pass covers them the way it would on six. Get that habit right once and the extra strings stop being a maintenance liability and start being just more guitar to work with — and if you'd rather keep the per-string numbers in one place than re-derive them at every setup, our care guides collect them alongside the rest of the setup spec tables.