So right now I've been playing through a blackstar ht40 (40 watt tube amp woth 1x12 speaker combo) and it's held up well in my band while we've been in the studio. The other guitarist has a 120 watt head and 4x12 cabinet but he doesn't turn up too loud in oiur space anyway so the volumes match about evenly.

However we're going to start playing live gigs soon and I don't want to be drowned out by the other instruments, so I'm looking to upgrade my setup. I would prefer to just get another 1x12 cabinet for my current amp, as that would be cheaper and easier to carry. However I've been told that this wouldn't increase the volume, but would only spread out the sound, and that latency could be a problem. I could also just get a full half stack like the other guitar has, but that would be significantly more expensive and a bigger pain to transport.

So I wanted to know objectively what are the pros and cons of each setup?

Hi mate,

Honestly if you're playing through a 40 Watt Tube amp then there shouldn't be any problem competing with your band for sound. Your mate has a more powerful amp for sure but you only ever need to be as loud as your drummer is going to be. When you're gigging the amps and drums will most likely be mic'd up and will go straight through the PA system. Stage sound does matter but often takes a back step from the overall live mix and PA sound.

If you want to get another amp then cool but I don't imagine you'll need them.

You can play a fairly sizeable club now with a 15 watt tube amp as long as it gets mic'd up and gets sent through the PA.

The cab does make a difference. A 4x12 will be significantly louder, with the exact same preamp and poweramp, than a 1x12 combo.

There is also more to amp loudness than simply watts. An Engl Fireball 60 (which is powered by two 6L6GC valves, so it's 50w) isn't nearly as loud as a Marshall JCM800 powered by two EL34 valves (which also means 50w power). In my band, the former is barely loud enough with a 2x12 cabinet. There is no headroom for lead boost left. A 100w Marshall JVM or an Engl Powerball 2, or a 50w Engl Screamer, however, is loud enough.

In OP's situation, I'd probably save for a 2x12 cab. I wouldn't be too worried about latency. It should be possible to disconnect the combo speaker and only use the cab anyway.

Cabs do make a difference, not just in volume but in clarity too. Think about it--are you spreading an army of wattage and wild harmonics across two or four paths, or are you trying to bottleneck all that sonic information into a single road? If you want something smaller and light then a 2x12 will do wonders. You can also put it on its side so that the speaker go up vertically, might be easier to hear onstage. Once you get into higher volumes (ie when the speaker cones start to really move at a high volume then your cabinet material and construction can colour your sound in cool ways too. Plus, if you're recording with multiple speakers you'll be able to pick and choose the best sounding speaker instead of being stuck with whatever condition your combo is in. Every speaker is different.

If you're in a touring band, you might consider having both guitarists use 2x12s with an amp head. Save a bit of space but still have solid tone. My 4x12 sounds killer but sometimes you gotta think about where you can make compromises.

Gotta say if you are gonna use a 2x12 just use a 4x12. I've seen hundreds of bands and the one thing that turns me off more then weak drummers are bands that have small gear/aren't loud enough. This is metal, it's all about volume. I'd play a full stack every show if I could and we usually take two cars every show we play locally but it's worth it because we know that we will be loud enough if we need to and will look good. For real, we were going to set up a show last year for this pretty bad grind band but it was only until we played a fest they also played that we found out they use a practice amp and a toy drumkit (I am not exaggerating in the slightest) and if I saw them set up with that I would have told them they can't play. Recording/practicing is a whole different thing, do whatever works best but I can't take a band seriously (within metal/punk/grind/etc.) if they don't have serious gear.

If you are playing in a place that has any kind of monitors for the band, why do you need to have loud amp on the stage? Guitar sounds better to the audience from the pa as the sound is spread more evenly and the sound guy can actually do something. I think I've had best guitar sounds at gigs where I used cab-modelled line output, taken between the power amp and cab, with amps volume being just enough for me to hear something and listening mainly monitor speakers.
And mostly when gigging, if you are not the only band of the night, it's usually easier just to bring your on amp head and have some local band to bring the cabs.

But for the cabs, I have a bit oversized 2x12 and normal 4x12 cabs. The sound difference between them isn't that massive, and other one can be carried with one hand and only takes one persons space in a car, so if I need to bring my own cab, the decision is quite easy.

^ this is correct, but isn't quite practical yet. The guitarist of a local band I know uses solely a Line 6 Helix into the board, no cabs. In a venue that has an adequate sound system to support that, it sounds great, and I'm sure the gear load he doesn't have to deal with is awesome. I use a Kemper these days so I've contemplated it, but I decided I need that feeling of air pushing behind me, it would be too weird without it, so I have it plugged into a power amp and cab.

Anyway, if you're worried about volume and space, a 2x12 is actually a perfectly fine solution. I notice a lot of bands moving to 2x12s, they're a pretty good compromise between the two, and with the smaller size you can focus on getting one with higher quality speakers. There's Harley Benton cabs that come with V30s, the standard metal speaker, for pretty cheap, and you aren't going to find a better solution for a similar price unless you manage to snag a Mesa 4x12 for a ludicrous price like I did (they occasionally come up used in the $400 region).

Well as a rule of thumb I usually go with: whatever weights less for live and whatever is heavier for the studio.

When playing live most people won't really care about what gear you are using, so whatever digital modeler can be a lifesaver. As for recording I always go with the 120w heads with the oversized cabs, but of course most professional studios will have those already.

My advice: go digital for increased practicality , however, if you must by all means utilize a full analog set, a 50w head with a 2x12 also go a long way.

Just a reminder: some manufacturers, like Peavey and Engl, advertise some of their amps as 120w, when they're actually powered the same as amps such as 100w Marshall or Mesa amps. A Peavey 6505 is advertised as being 120w, but it's actually powered by four 6L6 valves, which are 25w each, making it equally powerful as a Dual Rectifier, which is 100w, for example. A 100w Marshall valve amp may be powered by either similar valves, or the equally powerful EL34 valves, which, when saturated, produce a more cutting tone than 6L6, meaning that a 100w Marshall may actually appear noticeably louder than a "120w" Peavey, or Engl.

Not like it actually matters too much, because from a practical standpoint you're never going to come close to using the full capability of the amp. I barely pushed my Savage 60, the master at 3 was enough to compete with a drummer, and it's pretty similar with my Peavey 50w power amp loaded with EL34s. A 120w is stupid loud and totally unnecessary unless you're in serious need of headroom.

Depends on the kind of shows you play - last tour I went on, we had a few shows where the PA wasn't up to much/vocal only, so we were having to crank the amps pretty hard. My drummer is super loud, and my bass rig is hugely powerful, so we were running our 100w Marshall pretty close to cranked at times. Sometimes it's the PA shortcomings, sometimes it's the room, but having the extra watts does help. One venue we've done a few times (the Meatlocker at Temple of Boom in Leeds, for any UK folk), we struggled when we were using a 50w head - even maxed out, it wasn't getting over the drums. We've since run a couple of 100w+ heads, and it's been way easier for all of us on stage, as well as better out front.

Gigging is never exactly convenient - it's always easiest to drive. Taking a guitar on public transport sucks enough, let alone amps. And if you have a decent amount of merch, or a backdrop, or any lights/stage props? You need to drive. So if you're driving anyway, it's not that big a deal to have a bigger rig.

The same tubes can run at different plate voltage and thus create different amounts of output. Four EL34s running at a higher plate voltage will go much louder before they start to distort than four EL34s at a lower plate voltage.

That's a good point; it didn't occur to me. Some amps, like the Mesa Rectifier line, are biased very cold out of the box (this is apparently so that they can advertise that you can swap power valves in their amps without re-biasing), whereas others may have more appropriate settings.

Bias and plate voltage aren't quite the same. Bias is a measure of how much current a tube draws; plate voltage is electrical potential difference between the plate and the cathode. When you change an amp's bias, you're not changing the plate voltage. I don't think I've ever seen an amp with adjustable plate voltage.

Generally, if an amp has a high plate voltage, that means it's intended to run with lots of pre-amp distortion and a clean or mostly clean power section (most Engls and 6505s fall into this category). If it has a lower plate voltage, that means it's meant to run with a distorted power section (most Marshalls, Dual Rectos). Also, more plate voltage will generally be tighter and brighter, and less plate voltage will typically be saggier and darker.

Fun fact -- amp output is measured pre-distortion... but, as we all know, on an amp that's designed to distort its power section, when you're at your top edge of clean, you can still put out a lot more power if you want to distort it. A cranked Marshall Plexi typically puts out about 180 watts!

After thinking it over I think I'm going to upgrade to a 50 watt head with a 2x12 cab.

Cynical, thanks for clearing that up, that's very informative. That explains why Plexis are so deafeningly loud!