Speaker Efficiency And Tone

Written by
Dave Hunter
Published on
January 21, 2021 at 2:01:58 PM PST January 21, 2021 at 2:01:58 PM PSTst, January 21, 2021 at 2:01:58 PM PST
Guitarists are frequently chatting about how swapping speakers in any given amp or cab can quickly change up your tone, and for many years the topic trended toward the way in which more-efficient speakers can make an underpowered amp louder. That’s certainly true; changing a speaker with a 95 dB rating for one with a 100 dB rating can sound like you’re suddenly using a much more powerful amp.
It's worth considering, though, that you can get a lot of tone-tweaker mileage out of going the other way, and that seeking out less efficient, less sensitive speakers might actually achieve the results you’re looking for. Put simply, a speaker’s efficiency (also expressed as sensitivity) determines how much volume it will put out for any given input. Which simply means that less efficient speakers are not as loud as those with higher efficiency ratings, given the same wattage pumped into them from the same amp. (Note that ,for the sake of consistency, a speaker’s “sensitivity” or “efficiency” rating indicates the decibel level the speaker will achieve when measured at one meter from the cone with a signal input of one watt, a figure generally listed as “1 watt/1 meter” or “1W/1M”.)

There’s definitely an enhanced awareness of stage volume these days, and a general move toward acquiring great tone at suitable volume levels. The old-school method of “decibels be damned”—using a huge amp that only sounds its best when you get it cranked up way too loud for the gig, and blowing everyone’s hearing to shreds in the process—is pretty widely frowned upon. Instead, guitarists who want the cranked-up sound without the oppressive volume levels are searching high and low for effective ways of getting there, and dialing in your tone via carefully considered speaker efficiency is one way of getting there.
With this in mind, let’s consider that, as well as using a more efficient speaker to make a small amp louder, you can use a less efficient speaker to make a great but too-loud amp less loud. In essence, you make your speaker choice work something like an attenuator. The trick is, you still want good all-round tone, and choosing a speaker according to its sensitivity rating can limit you somewhat in that respect. Of course, swapping in a new speaker is always a little bit of a crap-shoot anyway if you don’t have the privilege of trying it with your own amp before buying it. But by reading the reviews, checking out the speakers your guitar-playing pals and band mates are using, and always keeping an eye peeled for the well-regarded speakers that carry slightly lower specs for efficiency, you can at least narrow down your selection.
Many vintage Jensen speakers typically have lower sensitivity ratings, and many reproductions, including some of the new ones in the Italian-made Jensen Vintage Reissue series, follow suit. The reissue alnico P12R and P12Q are both rated at 95 dB, which is fairly inefficient by today’s standards, and their ceramic counterparts the C12R and C12Q are even lower, at 93.8 dB and 94.6  dB respectively (consider these against the 98.4 dB rating of the P12N and C12N). Also, the new Jensen Jet Tornado neodymium-magnet speaker has a good all-purpose tone with plenty of warmth and roundness, and rates at 97.3 dB, while handling 100 watts of power. The Indiana-based speaker manufacture Weber Speakers also makes a number of good reproductions of vintage US-made speakers, and although they don’t publish their sensitivity figures, I know many of them fall in line with the lower ratings of the originals.

Celestion is perhaps best known for two great-sounding, classic high-efficiency speakers, the Alnico Blue and G12H-30, both rated at 100 dB, as are newer additions to the lineup such as the Alnico Cream and Gold. If you like that tone you might just have to make do with a loud amp. But the British company does have a range of great, if different, sounding drivers with lower ratings.
The legendary G12M Greenback comes in at 98 dB in the Chinese-made Classic Series and a mellower (and more authentic) 96 dB in the English-made Heritage Series (similarly, Mojotone’s own Greenback-inspired BV-25M comes in at a comfortable 97 dB). It’s a fantastic rock lead and rhythm speaker and an undeniable classic, although it doesn’t have the firm lows or snappy high-end twang that some players also need in a guitar driver, and it handles only 25 watts. The Heritage G12-65, however, offers much of the Greenback’s sweet midrange grind, but has a fuller bass response, clear, sweet highs, and handles 65 watts with an efficiency rating of 97 dB (original examples from the early ’80s are also often readily available on the used market, frequently offered up by players breaking up the big old 4x12 cabs the came in).
Note that the big American speaker maker Eminence makes some excellent sounding units these days, in their Legend, Patriot, and Red Coat series, although they are usually aiming for higher sensitivity specs than the speakers I have focused on so far. I do find, however, that some of them don’t sound quite as loud as their three-figure ratings might imply. The great Red Fang alnico speaker is spec’d at a whopping 103 dB, for example, but it sounded no louder than other 98-100 dB speakers I tested it against, so something like their 98.8 dB Legend 1218 or 99 dB Texas Heat might not be quite as blasting as you would expect.
In addition, Eminence released the FDM (Flux Density Modulation) series a few years back which includes the Maverick and the Reignmaker, both of which have adjustable voice-coils to allow the user to dial in their efficiency from 91.5 – 100 dB. The difference between the higher and lower of those figures represents a far more significant volume reduction than it might appear on paper.

Explore the speaker market—there are a ton of options out there these days—and pay close attention to write-ups, reviews, and sound samples that exhibit each make and model’s sonic characteristics, while also paying close attention to their efficiency ratings.
Overall, you still need to select your speaker with tonal considerations at the top of your list. But if the driver sounds right to you and also drops your output down just a little, ideally allowing you to play right in the sweet spot without the sound guy and your band mates constantly shouting at you to turn it down, that’s a double bonus in my book.