Photo 1: Despite the ornamental look of this golden Celestion speaker from 1924, its main components are essentially the same as today's.
A rumination on the history of bass speakers and how they compare to their guitar-amplifying kin.
Musicians rarely see the huge effect a speaker or cabinet has on their sound, as our relationship to our instrument is way more emotional and intense than with what comes after the output jack. In 1915, Peter Jensen perplexed those who attended his Magnavox speaker demonstration with the amplification of a human voice. The construction of that speaker—a conical membrane and a voice coil in a magnetic field—is principally the same as what we use today, although the Celestion speaker from 1924 looks quite different to what we are used to seeing (Photo 1). The tonal goals in the world of hi-fi speakers are pretty clear: a wide frequency range and high linearity, which is far from what our rigs require.
While the membrane of a guitarist's speaker is almost always made from paper or cellulose, bass speakers also sport carbon, Kevlar, or polypropylene for enhanced stiffness. Added mass and stiffness contribute to frequency response in the bass range. Extra ribs on the conical membrane and chemical coatings can further enhance stiffness and rigidity. And, as opposed to our instruments, where we often have tonally dominating parts like the pickups, almost all parts of a speaker are interacting.
On a guitar speaker, the shell of the voice coil is most often made from paper, making it both light and sensitive, with a detailed upper range, but highly sensitive to heat. The bass version sports bigger voice coil diameters, for better thermal flux, and Kapton or fiberglass shells. As guitarists initially swore on alnico and, later, ceramic ferrite magnets, the bass world has now moved on to neodymium—which is 10 times as powerful and more lightweight than a ferrite magnet—as the norm. As we know, compared to guitar gear, ours is typically bigger, heavier, and way more powerful.
Another common difference is that guitarists mostly rely on one speaker size for their whole rig—mainly 12". Bassists, on the other hand, are used to mixing several sizes, using crossovers, or even bi-amping, mainly because of the hard realities of reproducing a good low end.
In the heyday of our instrument, those huge and heavy Ampeg SVTs and their 9x10 cabinets were at the heart of many a bassist's dream rig. The 300W SVT came in around 88 pounds, while a modern 300W class D head might be just a mere 3.3 pounds. The evolution of speaker cabinets is quite similar, with lighter cabinet enclosures sporting highly efficient speakers. If we want to quantify efficiency or sensitivity per watt, we have to look at their sound pressure level (SPL) and remember what logarithmic scales mean for perceived loudness and necessary wattage: Raising SPL by 3 dB requires twice the wattage. Or, similarly, a speaker's 3 dB of higher efficiency is like doubling an amp's power.
Image 1: Here are two almost identical SPL and impedance plots, despite their fundamentally different magnet materials, with neodymium shown in blue and ferrite in red. The SPL plots are the wild upper curves, while impedance curves have just one peak.
Copyright SICA/Jensen Speakers, Italy
SPL measurements are most often shown as frequency response curves in the audible range of 20 Hz to 20 kHz, with decibel (dB) versus frequency (Hz). Image 1 shows a comparison of two 12" guitar speakers with an additional impedance plot in ohms (Ω). The two speakers use different magnet materials, with neodymium shown in blue and ferrite in red. Since neodymium is 10 times as powerful, that means a speaker's heaviest part, the magnets, can be 10 times lighter without much of a different tone and efficiency. Notice that both materials create almost identical results.
While frequency response curves are a common way to compare speakers, they can be misleading. Once SPL ratings are just given as one value in decibels, they are either measured as the level resulting from 1 watt at 1 kHz in 1 meter distance from the speaker—an old and not very helpful standard from the days of portable transistor radios—or as an average of a frequency range. Some manufacturers use complete audible range or parts of the prominent midrange in their spec info. So, as valuable as these frequency response curves can be, keep in mind that, without knowing the details, comparability between manufacturers has its limits.
Straight from the builder’s bench: Here are some tools that might just make your life a little easier.
Straight from the builder’s bench—these are the cool tools you need to keep your workflow moving along smoothly.
Guitar gear, by nature, regularly requires a bit of maintenance. So whether you’re a guitarist, builder, or both, having good tools makes it easier to stay on top of seasonal or technical changes. Any endeavor that requires mechanical or electrical maintenance is subject to what I call the 80/20 rule. This axiom refers to how we can spend 80 percent of our time fixing and 20 percent enjoying the fruits of our labor. You probably have a screwdriver or some wrenches, but there are a few neat little bits that make life on the workbench more pleasant and maybe shift the percentages of that rule.
Not everyone has perfect vision, and little things like guitar parts can be hard to see. Eyesight—which includes the brainpower to decipher what the eyes register—is one of the most energy-intensive things we do. Scientists say that vision uses somewhere between six and 20 percent of our brain’s resources. Even if you’ve got eyes like a hawk, it’s important to be kind to your system when manipulating tiny guitar parts like screws and strings. At the risk of sounding like your parents, I suggest you invest in some good lighting and a headband magnifier like the one Leo Fender wore. If you’re concerned about looking like a dork, remember that Leo invented the Stratocaster. I’ve got a few of these scattered about my shop at stations where vision is critical to the task, like adjusting intonation and bridges. They’re great for checking frets for high and low spots, too.
One of the most inexpensive and brilliant tools you can buy are good tweezers. Don’t bother with the junk from the health care aisle at Walmart. Go straight to McMaster-Carr’s website and get a couple differently shaped industrial-quality stainless steel ones. Once you get used to them, you’ll never turn back. And, of course, they also fit into your guitar case. I have a pair on almost every bench and desk in my shop—but then again, I’m a tool addict. The bent-tip tweezers are extremely useful for all small jobs including handling small screws. The ones with serrated gripping surfaces are great for threading strings through bridge and tuner holes. If you have champagne taste, go for the titanium solder-resistant pair for ultimate bragging rights.
I could be recommending old-school biker jeans from the ’60s, but this is about shrink tubing. I’ve been using this stuff for all kinds of jobs since before Jimi Hendrix played with Wilson Pickett—and I still haven’t run out of new uses. Basically, it’s rubberized tubing that shrinks 50 percent in diameter when heated. It’s made for insulating wire splices. You slip it over the splice and blast it with a heat gun (another great tool) until it shrink-wraps itself around the joint. But that’s not the only thing it can do. You’ve probably encountered high-dollar guitar cables with shrink tube reinforcing the ends. You can upgrade your everyday cables for pennies by adding those reinforcements yourself. I’ve also used it to protect parts from abrasion. The material is tough and can also be used to prevent scratching on certain parts. Buy an assortment of diameters so that you have the proper size for any job. You can also layer diameters to get a custom fit. There is even a shielded version, which is perfect for audio wiring. This miracle part is available at vendors from Amazon to Zoro, in sizes up to 2" diameter. If you want to get into the weeds with this stuff, McMaster-Carr is once again the rabbit hole of choice.
We’ve all had our lives improved by drywall screws. Anything and everything you need to assemble quickly can be done with these little black wonders. Still, I’ve a new love, and its name is Spax. This German-designed, multi-purpose fastener is the Acropolis of quick-screws. The secret in each screw is three-fold: superior strength, multiple thread pitches (one for drilling, one for fastening), and a self-countersinking head. From hardwood furniture building to use with medium density fiberboard, these superior fasteners are self-drilling and reduce splitting when used without a pilot hole. After discovering these wonderful screws, everything else is Mickey Mouse—they’re great for repairing cabinets, cases, pedalboards, and more. Builders will love it for temporary tooling.
I hope a few of these items make your repair and build time more enjoyable. Nobody likes to have to fix stuff when they’d rather be banging out a tune. I still struggle with the 80/20 rule, but I have the tools to fight back. I’ve spent decades looking for the easier way around, and so should you.
In a message posted to its website, Electro-Harmonix has stopped taking any new orders and fulfilling back orders on all Russian vacuum tubes. This is due to a ban that Russia has imposed on over 200 types of goods.
Here’s the statement from EHX founder Mike Matthews:
On March 11, 2022, Russia imposed a ban on the export of some 200 goods in response to the sanctions imposed on it over the current conflict in Ukraine. We have confirmed that the ban applies to our seven brands of Russian tubes. Currently, the ban is set to remain in effect until the end of the calendar year.
Given this export ban, we will not be receiving any further tube inventory for these brands. A myriad of pressures — including continued strains on the supply chain, escalating internal expenses, mounting inflation, and an ever-evolving legal landscape (particularly in light of the Ukraine conflict) — have created a very fluid and ambiguous environment. Until we can properly assess the impact of these factors, we will not honor any new orders or ship any more Russian tubes on back order.
The brands affected by this ban include Svetlana, Sovtek, Mullard, Tung-Sol, Electro-Harmonix, EH Golden, and Genalex Gold Lion.