Turn a 1meg pot to 50% (whether that's actually at '5' or elsewhere depends on the taper of the pot) and you've got the same sound as a 500k pot on '10'.
If you have the pickups running through multiple pots, they'll have the same affect on tone as if you had fewer lower-resistance pots. E.G. having two 1meg pots on a pickup has the same effect as one 500k pot. You can also think of it in reverse: if you have a guitar with two 500k controls on a pickup, and you remove one of those controls, you get the same effect as if you kept both controls but changed them to 1meg.
Using these guidelines, you can estimate what sound you'll get by switching to 1meg pots. Obviously, every single individual pot can vary in resistance, just as every pickup will vary from the advertised spec a little bit. So expect +/- 5-10% variation. (Higher-quality pots tend to be made to within 5% spec; some cheap pots may be as much as 20% off; most are made with a manufacturing tolerance of 10% variation.)
The above comments about the taper of 1meg pots are simply irrelevant; you can get logarithmic 1meg pots, linear 1meg pots, reverse-log, and there are all kinds of custom tapers being made. The resistance value has nothing to do with it. Simply get a pot—whatever the resistance—with the taper which best fits how you use your controls. (General rule: clean amps where you are controlling the actual volume of your sound from guitar = log volume control; dirty amp where the volume will be staying basically the same but you'll be cleaning up by reducing output = linear volume control.)
If you're unsure and have never tried single-control guitars or higher-resistance pots before, what I suggest you do is wire it up with 500k volume and tone pots, but leave out the tone control from the circuit; have it ready to go, but don't attach it. That way you can test out how you like the sound with just a 500k volume pot, which is what you'd get if you used 1meg pots for both volume and tone. If you like it with just the one 500k pot, you know you can swap in 1meg pots. If you don't like it then you've got the tone control ready to be connected right away.
That said, the 'bell' tone doesn't have much to do with what controls you use. It's more about pickup construction. Telecasters don't actually have that much treble, in terms of overall signal strength; they just lack mids, which makes the higher frequencies stand out more. The same way that chambered and hollow bodies don't have more mids, they just have less treble. (Though don't worry, chambered swamp ash is still fairly bright.)
'Bell'-like tone is typically ascribed to the following pickup constructions:
- A5 or A3 humbuckers with exceptionally mis-matched coils.
- A5 single coils.
- 'Wide Range' humbuckers.
- Firebird pickups.
The Seths are none of those, and using 1meg controls won't make them so.
A SD Jazz is much closer to the 'bell' sound, though the Full Shred is actually the closest SD to that kind of sound. (The Full Shred is a Jazz/Custom 5 pair, with the normal slugs and screws replaced with black hex poles.) Of course those are also higher in output. The DM Air Classic Neck, PAF Master Neck, and EJ Custom Bridge/Neck are also all much closer.
Swapping the Seth's magnets for A5 or A3 would help, if you already have those. But if you've not already bought them then there's no point buying them to mod them, instead of just buying something which gives you that sound right out of the gate.
Much better results would come from using a pickup which uses separate magnetic pole pieces, or a bar magnet directly under the strings, rather than a normal humbucker construction. Seymour Duncan make the Stag Mag, which can be wired parallel for a very tele-humbucker hybrid sound, or wired series as normal for a 'Wide Range' humbucker tone. Various boutique pickup winders make humbuckers with magnetic pole pieces or direct bar magnets; personally, I like The Creamery's take on Wide Range humbuckers in a normal humbucker size, and Catswhisker pickups have made some very nice normal-sized Firebird pickups for me in the past. Many others also make similar designs; shop around to see who's most local/cheapest for your area.
If you wanted to stick with the Seth humbuckers, then again I'd strongly advise swapping the magnets. With that done I'd make sure to place them much further from the strings than you'd usually set your pickups. For controls I myself would use one 550k pot (they're rare but basically it's just a guarantee that you'll get at least 500K, as opposed to regular 500k pots which may come in lower than that), or if you insist on having a tone control, I'd use a 500/550k for the volume and a 1meg for the tone.
Oh, and being potted or not really does not matter. It only comes into play if you play at significant volume and with a fair bit of distortion or compression; even then, it just means a few of the really high harmonics come through stronger. It doesn't transform the tone and it doesn't give you any more chime. FWIW I have a solid mahogany (no maple) Les Paul with a potted Full Shred at the neck (single 500k volume control) and an alder Telecaster with an unpotted medium-wound A2 PAF copy (500k individual volume and 1meg master volume) and the Full Shred has more treble, is much clearer and chimey, and is generally all-round much better for clean tones with lots of 'bloom'; precisely what makes up the 'bell' sound. I can not stress enough how important a clearly defined magnetic field is for that tone, more than any other element.
