Extended range guitar
An extended range guitar is a guitar with more than 6 strings. For certain microtonal guitars, e.g. the Kite guitar, this may not actually increase the range, because the interval between strings may be smaller than usual.
With more strings, it's important to avoid both a too-wide neck and a too-tight string spacing. The 7-string Russian guitar (now also made in Ukraine and Romania) tends to have a narrower fingerboard and a tighter spacing than a 7-string classical guitar.
General resources
Forums
Models
Sources for 7- and 8-string guitars, both acoustic and electric:
Low-end (US$200-400)
Grote (China)
7-string archtop semi-acoustic
Very favorable review that claims it's a great value for the price:
https://riverheightsmusic.com/grote-guitars-review-7-string-arch-top/
Trembita (Ukraine)
7-string steel string
https://trembita-guitars.com/index
Leo Tone (Ukraine)
7-string steel string with tight string spacing
https://www.amazon.com/Russian-Guitar-Acoustic-Classical-Cutaway/dp/B00L2K6DJY
Somewhat unfavorable review:
https://www.youtube.com/watch?v=NZd1b-yJqrs
Jackson
US$200 7-string electric: https://www.jacksonguitars.com/en-US/guitars/js-series/js-series-dinky-arch-top-js22-7-dka-ht/2910132568.html
Thomann Classica
US$322 7-string nylon: https://www.thomannmusic.com/thomann_classica_fusion_7_string.htm
US$339 8-string nylon: https://www.thomannmusic.com/thomann_classica_fusion_8_string.htm
Mid-range (US$500-1200)
Ortega
7-string model:
https://reverb.com/item/65299164-family-series-pro-7-string-solid-top-nylon-classical-guitar-w-bag
Agile
various 7 and 8 strings, sold in the US by Rondo
https://reverb.com/shop/rondo-music
Ibanez (Japan)
various models
discontinued US$900 7-string classical: https://ibanez.fandom.com/wiki/G207CWC
High-end (US$1200 and up)
Ovation
Discontinued $1200 8-string steel string: musiciansfriend.com/guitars/ovation-1788tx-5-elite-tx-mid-depth-8-string-acoustic-electric-guitar
Discontinued $1600 8-string steel string: sweetwater.com/store/detail/C2088AXPSTB--ovation-exoticwoods-custom-elite-8-string-sapele-tobacco-burst
Try to get an Ovation case, as it won't fit in most other cases.
Rozini (Brazil)
7 and 8 strings
https://rozinibrazil.com/en/categoria_de_produtos/guitars/
Kremona (Bulgaria)
US$1599 7-string nylon: https://www.kremonausa.com/en/performer-series/fiesta-cw-7-kremona
Their website claims they can make any sort of custom guitar, so they might make a microtonal one?
Nut and saddle widths
Nut width #2 and saddle width are both measured from the outside edges of the two outer strings (i.e. the highest and lowest strings).
Nut gap is the average edge-to-next-edge gap (See How to make a Kite Guitar#String Spacing)
12th fret refers to 12edo frets, i.e. midway between nut and bridge.
Saddle gap is the average gap between strings, measured edge-to-edge.
| strings | type | nut width | nut width #2 | nut gap | 12th fret width | saddle width | saddle gap | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Leo Tone L-15 | 7 steel | acoustic | 1.9" | 48.5mm | 1.59" | 40.5mm | 0.48" | 12.4mm | 2.25" | 57.3mm | 2.37" | 60.3mm | 0.36" | 9.1mm |
| Doff | 7 nylon | classical | 2" | 51mm | 1.72" | 43.8mm | 0.53" | 13.6mm | 2.24" | 57.1mm | 2.51" | 63.8mm | 0.38" | 9.6mm |
| Eastman AR810CE | 7 steel | archtop | 2 1/8" | 54mm | 1.86" | 47.5mm | 0.59" | 15.1mm | 2.42" | 61.5mm | 2.39" | 60.7mm | 0.37" | 9.4mm |
| Ibanez G207CWC | 7 nylon | classical | 2.4" | 61.2mm | 2.08" | 52.9mm | 0.65" | 16.5mm | 2.69" | 68.5mm | 2.72" | 69.1mm | 0.41" | 10.5mm |