This is possibly the #1 question that I get asked, and I have two answers.
1) Short answer: Celestion G12H 30W for british/overdriven tones. JBL E120 for cleaner tones. This is entirely my own subjective preference; you may hate them!
2) Longer answer: The speaker and its cabinet is a very significant factor in the sound of any guitar amp. Guitar speakers and cabinets don’t have a flat frequency response; and all of them can accentuate or suppress certain parts of the audio spectrum.
For example, I find the G12M 25W ‘Greenback’ to be quite mid-focused, and quite ‘nasal’ in an open-back combo cabinet. I think that suits the classic ‘British invasion’ tone of the mid-to-late ’60s. But if I dial in a later ’70s hard rock tone with the amp, the same cabinet doesn’t sound right to my ears. And I end up back with the G12H 30W cabinet that I mentioned above.
It is 100% subjective though, and what I don’t like might be your tonal ‘sweetspot.’ I’ve never got on with 10-inch speakers, for instance, whereas some guys just love them.
Think about this… it’s no coincidence that the speaker is every bit as important in shaping YOUR own tone as the other wire+magnet you use – right at the other end of the signal path is your guitar pickup. Some guys love the articulation of their noisy single coils, others prefer the thicker tone of humbuckers. And I would never presume to tell a guitarist which pickups to use for his tone!
If you’re choosing a speaker for your amp kit, and really don’t know
where to start, my recommendation is to start with a speaker that
already works for you.
For me, it’s a ’70s Marshall 4×12 with G12H 30W speakers. I experiment a lot, but I always seem to come back to this – it’s become my reference cabinet for every kit I build and every amp I own.