2×12 cab wiring: Parallel versus Series

Though I feel my amp is at its potent, smoldering best lately, I am a human man, and make it my business to find dissatisfaction wherever contentment looms. I’d begun thinking some element was a little masked under all that warm, crunchy, modded-Plexi magic (I’m mostly playing 1st Gear with the gain maxxed on a Splawn Competition head.) A couple days ago when I picked out the intro to ‘Bigfoot’ by Alcatrazz (TAB) it just wasn’t jumping out enough, the notes getting muddled on their journey, and when thinking about how to open up the sound in a more holistic way than aggressive EQ tweaks, I remembered some experimenting I’d done a year ago, wiring the speakers of my 2×12 cab differently to affect the sound.

Guitarists don’t talk about it much, and the majority probably don’t give it a second thought, perhaps buying sealed cabinets and never knowing what the wires are doing inside, but the choice of parallel or series speaker wiring does make a difference to your guitar tone.

On my road to find out what the established differences were last year, before actually getting in there and moving wires around, I ran into a passage on the subject in a book on Google Books called The Guitar Amp Handbook. The author explained simply what I needed to know: parallel is tighter due to increased damping; series is looser.

And it’s true.

I opted, back then, for series, desperate as I was to do anything to ease the forever tense muscles of the super tight Splawn and buy myself a spongier, more forgiving tone. In 22 years I’ve never played an amp that sounds as good as a Splawn, but they can be merciless on the player.

I’ve since learned to control the amp better, attenuating it to allow the master volume to come up into the friendly zone, where it gets easier to play, sounds warmer, and just bleeds harmonic richness. The series wiring, I reasoned, may no longer be necessary, and could be combining to muddy up my tone and response, so I got in there one night recently and changed it back to parallel, the standard wiring for modern 2×12 cabs. Then… back to series, back to parallel, series again, back and forth several times (thank God for quick release clips and open back cabs), playing largely the same riffs and solos at the same volume, paying attention to what was happening tonally.

Parallel felt less gainy or saturated than series, making it a mite tougher to play, though it was definitely, as hoped, more open, more detailed. Notes seemed less round and warm, but attained a clearer crunch in chords, riffs and double-stops that was addictive, the bass becoming less boomy and fat, feeling more tightly attached to the fingers.

I focussed on this last area specifically while swapping the wiring back and forth, because bottom end is something I have trouble getting right. Palm-muted neck pickup stuff on the low E around the 12th-15th frets was less floor shaking in parallel, more separate and distinct. Fast neck pickup playing lower down the neck, such as thundering around the bottom end of an A Minor scale, had more openness than series wiring provided; I could hear the pleasant scratch of the pick attack clearer on top of the notes, a la good Yngwie.

Less uncontrolled bloom to the bass and more damping in parallel equals less warmth, though, a little less grease in the cogs of your playing, demanding more work than the intuitive and easy series set up, which felt more fluid and offered seemingly endless sustain. Hard things to give up, but cleaning off the mud could make it worthwhile, depending on your approach and sensitivity to such things. I felt I could throw myself recklessly and passionately into my playing in series, whereas parallel took more concentration but emerged clearer from the speakers.

Ultimately, I opted again for series wiring, for the time being. It just felt more natural and expressive. I realize I’m giving away some clarity and zing for that liquid sustain and warm growl, but everything is a compromise. Broadly, parallel wiring was better for rhythm while series was better for leads, and I couldn’t help feeling that playing two 2×12 cabinets simultaneously, one wired each way, would be the perfect blend, but that may not be the case…

Contrary to the explanation in The Guitar Amp Handbook and elsewhere, it’s possible the difference you hear is not actually due to parallel or series wiring itself, but the point at which the amplifier’s output transformer is tapped (which has to change at the same time). For example: my two 8 Ohm speakers connected in series present a 16 Ohm load to the amp, so the control on the back is set to 16 Ohms; the same two 8 Ohm speakers connected in parallel equate to a 4 Ohm load, and so 4 Ohms is selected. This taps the output transformer at a different stage in its circuit, and some people tell us this is what we’re hearing — how our amps sound when their OTs are tapped at various stages — rather than the cabinet wiring that necessitates it.

It’s probably a bit of both. Speaker genius Ted Weber described the effects of parallel and series speaker wiring on his Q&A page (upsettingly without an index; find the question from Gerald C. Lopez, about one third down the page), but made sure to point out the myriad other factors at play.

It’s interesting to note that Ted said of the series option:

Many players prefer the series connection, as it gives them a more textured tone, enhanced breakup, and overall a more desirable tone for guitar work.

Weird, then, that series is not the default wiring of 2×12 or 4×12 cabinets. Oh yes, 4×12 people can play this game, too. Everything here about the tonal differences between parallel and series wiring also applies to 4×12 cabs, though the wiring itself is more complex, and the effects are sometimes said to be subtler. ‘Series/parallel’ will give you the warmer, looser effect we’ve talked about, and is how vintage Marshall 4x12s were wired up. ‘Parallel/series’ will give you the tighter, zingier crunch — this is how 4×12 Marshall cabs are wired today. See page 225 in the Desktop Reference of Hip Vintage Guitar Amps (scroll down to Marshall).

Wiring diagrams are all over the web, but I like to refer to Celestion’s. Look there if you are planning to make any changes. Remember to photograph or otherwise document your original wiring first!

So there we go: a largely unacknowledged, free, easy and reversible way to alter our tone, however subtly. Guitarists will talk endlessly about the tiniest attributes of tubes, controls, wires, woods, magnets, cloths, metals, paints, but rarely mention speaker wiring. Maybe we can add a new question to preface the pedantry: What are you — series or parallel?

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