Game of Tones
How to expand classic Fender amp sounds with different speaker configurations.
As you know, replacing or augmenting the speakers of your Fender amps is the easiest way to organically change your guitar tone. So, let’s discuss some alternative speaker configurations for classic Fenders. We’ll also explore some basic knowledge about resistance, current, and power distribution along the way, which will enable you to safely experiment.
If you are replacing or adding speakers, it is important to verify that all speakers are in phase and that you wire the plus and minus terminals correctly. Otherwise, the speakers will cancel each other out and the result will be a thin, weird tone without much bass or character. This rule applies to all speakers in the main amp and in extension cabinets. For all the examples in this column, I will refer to 8-ohm speakers wired in parallel, if not explicitly mentioned otherwise. I will also use both the terms “impedance” and “resistance,” which are commonly used in these conversations, even though the correct term for speaker resistance is impedance. Got that?
Now, let’s use a Deluxe Reverb as an example. The most common trick to create a bigger tone and more spread from a Deluxe is adding a second cabinet with a 12" speaker. The Deluxe has just enough power to drive them both. However, I’ve found that the Deluxe’s 22 watts is not enough for adding a 15" speaker. The bottom end gets too loose and farty. For that option—which features a full clear bottom end and opens up the array of overtones—I would typically recommend a bigger, 35- to 40-watt amp. But there is an option for adding a 15" speaker to a lower-powered Deluxe. You can replace the 6V6s with 6L6GC tubes for more power. Then, adding a 15" speaker makes sense.
“It is important to verify that all speakers are in phase and that you wire the plus and minus terminals correctly.”
Here comes a few even-more-advanced tricks with the Deluxe Reverb. The first: Replace the original 1x12" baffle with a 2x10" baffle for snappier low-end response, more sparkle, and a more scooped tone. It is very easy to cut out a solid pine board and staple grille cloth onto it. With two 10" speakers, the total speaker impedance also changes from 8 to 4 ohms, and will suit the 6L6GC tubes better, since they have a lesser output impedance than the 6V6 tubes. After that mod, if I want to play at lower volumes, I unplug one speaker and use the Deluxe Reverb as a single 1x10".
An even more creative and rarer variant is to use both 10" speakers together with a 15". In this setup, you have to wire the two 10" speakers in series and connect the 15" via the external speaker output. The amp will then see two resistance branches in parallel:
- Branch 1: the two 10" speakers = 8 ohms + 8 ohms, for 16-ohms resistance.
- Branch 2: the single 15" speaker = 8-ohms resistance.
The current always wants to follow the path of least resistance, so the second branch with the 15" speaker will get twice the amount of power and current as the first branch. And since there are two speakers in the first branch, that total branch’s power is divided equally between them. This results in a roughly 67 percent + 17 percent + 17 percent power distribution for the three speakers. This is a healthy and good-sounding balance, since a 15" speaker requires and can take a lot more power than a relatively tiny 10" speaker. Be aware that you must not use the amp in this configuration without the 15" plugged in, or you will damage the power tubes. The amp expects a 4-to-8-ohm impedance with the 6L6GC tubes. The two 10" speakers alone at 16 ohms is too far outside the safe operating range.
I will also briefly mention a change-up for the 2x10" 35-watt Vibrolux Reverb. If you want more punch and a bigger low end from this model, you can replace one of the 10" speakers with a powerful and efficient 12". I have had great fun fitting a 12" Celestion Alnico Gold on the preamp side of the amp and a lighter, neodymium Jensen Jet Series Tornado 10" on the power transformer side of the amp, where there is less physical space for a big speaker magnet. You now have three power levels: the 10" alone, the 12" alone, or both together for maximum punch. I can even add another 12" external speaker cabinet via the external speaker output for a mega spread on big stages. If I want to add a 15" extension speaker, I prefer to disengage the internal 10" and use the 12" and the external 15" together. My favorite modern 15" is the Eminence Legend 1518. It is impressively responsive. Also, it balances nicely with a classic vintage black-panel Fender tone.
I hope these ideas and tricks inspire you to experiment with speakers.
Speaker Geeks: The Lowdown on Power Handling
Here’s what you need to know to avoid blowing a guitar speaker.
Power handling. It’s one of the most fundamental loudspeaker specifications, and yet one of the most misunderstood. Here’s what you really need to know about choosing the right speaker for your setup.
As guitar players, we’re all comfortable with the idea of our amp’s power rating. It’s a handy means of quantifying how much “boost” we can apply to our guitar signal, how much bigger we can make the output. A guitar speaker’s rating considers power from the opposite direction. This rating represents the maximum amount of amplifier power the speaker can safely tolerate over a period of time. If the power input from the amp to the speaker is lower than the specified power-handling figure of the speaker itself, then the speaker ought to deliver trouble-free operation for a lifetime. But if you feed a speaker anything beyond its stated maximum, problems can occur.
In practical terms, this means if you connect a 50-watt amp to a speaker rated at 50 watts (or more), then you’re good to go. However, connect a 20-watt speaker to the same 50-watt amp and you run an increased risk of the speaker failing at some point down the line ... probably in the middle of your showpiece solo.
Avoiding disaster. Operationally, choosing a speaker you can safely use is simply a matter of getting to know which speaker is going to work with your amplifier without breaking. For that 50-watt amp, a 50-watt speaker will work fine, but so will any speaker with a power rating greater than 50 watts. It could be 60, 75, 100, or even 150 watts. In terms of functionality, it doesn’t matter. Beyond that it’s simply down to your tonal preference as to which speaker you select.
The same principle of maximum amp power also applies to multiple speakers. If you run a 2x12 cab with that 50-watt amp, I’d recommend using a minimum of two 25-watt speakers. Similarly a 2x12 cab with dual 60-watt speakers provides you 120 watts to play with, which is still great.
It’s perfectly okay to mix two speakers of differing power ratings. If you do this, then the overall cabinet rating will be twice the lowest rated value. So a 2x12 cab loaded with both a 25- and a 60-watt speaker will have an overall power rating of 50 watts.
lowest rated value.
Where to draw the line? There’s a school of thought that suggests you need to be driving a speaker to a certain level—perhaps somewhere between half and full power—to make it “do its thing.” The best option, so the thinking goes, is to choose a speaker with a power handling close to the max power output of the amp. While it’s true the more you crank up the power, the more gnarly (I believe that’s a technical term) the speaker output will likely become, the truth is a guitar speaker actually begins adding its tonal mojo at very low levels—mere fractions of a watt. So whatever level you’re playing at, you can be sure you’re already getting oodles of the lovely speaker tone you crave. Ever wondered if you could use that cute little 5-watt lunchbox amp with a 90-watt speaker? Sure you can, and I bet it’ll sound fantastic.
What dictates power handling? Testing a speaker to find its power handling gives us an insight into how the speaker copes with a sustained input both mechanically (in the repeated back-and-forth motion of the cone, voice coil, and suspension) and thermally (with the heat generated when you send a powerful signal into the speaker) over an extended period of time.
At Celestion, we test speakers in a number of ways: We play guitar through them, we play recorded music through them, and basically we do everything possible to find the limits of the speaker’s performance and what it takes to break it. More scientifically, we also feed the speaker with an RMS test signal—random noise with a consistent level of sound energy that’s averaged over time.
By subjecting the outcomes of these tests to experienced interpretation, we can arrive at a meaningful power-handling value. “Averaged over time” is perhaps the most critical statement here. For example, if we know that a guitar speaker can cope both mechanically and thermally with a constant 50-watt input signal for 100 hours with no adverse effects, then we can safely assume that the same speaker will have little problem withstanding a cranked 50-watt tube-amp signal that’s apt to produce higher transients from time to time.
Power handling needn’t be a barrier to speaker choice. In fact, once you’re armed with the knowledge of what it is (and isn’t), you can confidently choose from a bigger selection of speakers, and that can only broaden the range of tonal possibilities available to you.
Speaker Geeks: Alnico or Ceramic ... What Gives?
Weber Speakers guru C.J. Sutton demystifies magnet lore in the second installment of our new column series.
I’m going to tell you something you already know: People like different things. Shocker, right? Apples or oranges, cake or pie, Strat or Les Paul … the list goes on. And it seems the more polar opposite things are, the more likely a person may gravitate toward one choice and show disdain for the other. Like the English and Scottish in Braveheart, guitarists can end up on opposing sides ready to do battle over such life-or-death issues as whether to use tube or solid-state amps. That said, I urge us all to agree on one thing: Amplifiers don’t make sound without speakers. Even the simplest amplifier can be an extremely complex piece of electronics, but a speaker is a very basic electromagnetic motor (Fig. 1).
When you apply signal to a speaker, the voice coil begins to move in and out in response to that signal. As a result, the voice coil creates a magnetic field of its own, which works against the magnet and tries to demagnetize it. However, the magnet generates energy in the opposite direction, and it becomes a back-and-forth struggle. Gluing a cone to a moving voice coil harnesses this motion and makes it audible. That’s the basic idea behind a speaker.
A voice coil is like an electric motor. The bigger the voice coil and the more wire used, the more torque or pulling power you have to move the cone. With the proper match of components, you can get more sensitivity, wider frequency response, and more power-handling ability. The size and type of magnet also affects a speaker’s sound. There are two major types of magnets used in loudspeakers: alnico and ceramic. These magnet types differ and this difference affects a speaker’s overall tone. Let’s take a closer look.
The first crop of speakers in the early 1950s used alnico magnets, which is why some people say they sound more “vintage” than speakers built with ceramic magnets. An alloy comprising aluminum, nickel, and cobalt, alnico demagnetizes relatively easily, which gives a smooth response with compression at higher average volumes.
As the voice coil’s effect lowers the available magnetic field of the alnico magnet, the speaker becomes less efficient, and the voice coil moves less. The physics of it is that the small magnets near the surface of the magnet poles (called “domains”) begin to change state, or flip directions. The result is smooth compression, which is the same kind of operating-curve compression that occurs in a tube amplifier.
During the 1960s, the popularity of speakers with ceramic magnets increased. The most common type of ceramic magnet is strontium ferrite, which demagnetizes much less easily than alnico. The domains change state much faster, so there is little to no compression as the voice coil moves to its mechanical limit. Because the ceramic magnet isn’t introducing compression, the result is a cleaner sound in comparison to alnico.
Some folks might liken the difference between alnico and ceramic speakers to the difference between tube and solid-state amplifiers, where one compresses smoothly and the other gives all it has and then clips hard. I don’t know that it’s a fair comparison because the differences between the speaker types aren’t as starkly contrasted as the differences between the two amp types. Furthermore, by varying the size of the magnet, it’s possible to build very efficient alnico speakers, as well as very inefficient ceramic speakers.
Now that you know the reasons why the two magnet types do what they do, you can decide which side of the battlefield you want to be on. Or you can decide that it doesn’t have to come to war at all. That maybe it’s best to have each type of speaker, so you can be ready for whatever tone might be necessary at any given time. Some players even mix alnico and ceramic speakers in the same cabinet. Though different in the way they operate, their purpose is the same: to supply energy to the motor, so the cone will move and thus everyone will hear whether you’ve been practicing or not.