No, it’s not obvious, and yes – we get asked it all the time. The fact of the matter is: hi-fi is a little… complicated. There are choices, there are preferences, there are brands that are more compatible with other brands and combinations that are more effective than other combinations… and the list goes on (… and on. And on). So it’s no wonder we get asked such things, even by those with the know-how and the passion.
Well, I have good news, and I have bad news… which are both also good and bad in their own right.
Get your head around that.
The bad (… and good!) news is… there is no ‘answer’, not really. There are endless combinations that will work perfectly well together, and much of the finickity stuff comes down to what you prefer to hear.
The good (… and bad!) news is… there are combinations that won’t work at all, or won’t work very well. Which will help you narrow your options down a little.Thankfully, there is some science that will help you on your path to a perfect* speaker/amp pairing.
* … largely dictated by choice, once again. We strongly recommend you demo a few before you make up your mind.
And yes, we have done some digging around and found the science for you.
The Science of Speaker/Amp Pairings
Because it’s generally good practice to do so, we asked our resident techie Richard on the science behind finding a fitting match in a headphone amp, and he had this to say:
“It all boils down to the power output ratio vs the impendence of the speakers. The higher the impedence of the speakers the greater power the headphone amplifier needs to be.”
The more eagle-eyed of our readers may recognise that quote from Richard as very similar from when we discussed headphone and amplifier pairings a little while back. Well, as we said then, headphones are essentially speakers that are strapped to your head. Sure, there is much more to it than that, but the science of amp selection is much the same.
Which means that, once again, we have to revisit our friends…
Ohms & Impedance
We love this graphic.
In short, an ohm is the unit in which impedance is measured, and the property of a pair of headphone that restricts the flow of electrical current. The impedance of a unit is fixed, which means it is a reliable unit of measurement for headphones (and what kind of power they will need). It is pretty imperative to understand the output of ohms from the amplifier and the impedance of the speaker, as not doing so can result in a blown driver. Or worse: poor sound quality !
Ohm’s Law states that in an electrical circuit, current flow is directly proportional to voltage and inversely proportional to impedance. Mathematically, this becomes: Current (in amperes or I) equals voltage (in volts) divided by impedance (in ohms).
By knowing the voltage and the total current, it is possible calculate the total impedance of the headphones by dividing the voltage by the total current. To quote from the above linked article:
‘As an example, if a (solid state) amplifier is producing 10 volts AC to an 8 ohm speaker, the current in the speaker will be 10 volts / 8 ohms or 1.25 amperes. If the amplifier output is increased to 20 volts to that 8 ohm [headphone], the current becomes 20 Volts / 8 ohms or 2.5 amperes. So increasing the voltage increased the current. If the voltage decreases back to 10 volts, the current will decrease back to 1.25 amperes. Now, if our amplifier with 10 volts output is connected to a 4 ohm [headphone], the lower impedance will allow more current to flow. The amount will be found by 10 volts / 4 ohms = 2.5 amperes. If we use a 2 ohm speaker, even more current flows: 10V/2 ohms = 5 amperes.’
The lower the impedance, the larger the strain the speakers place on the amp. Therefore matching the impedance of your speakers to your amplifier is important. Most home theatre speakers will be 6 or 8Ω, as are most home theatre amplifiers. Two-channel amplifiers have a much broader range and single units can be capable of handling impedances from 8Ω t0 2Ω. Because of this,two-channel speakers come in a broader spectrum of of impedances. Choice!
By mismatching the ohms of a amp to the impendance of a speaker, you run the risk of putting more of a load on the amp than it’s designed to handle, and produce less than dynamic sound. And there’s always the chance that the amp will overheat, which can cause all manner of short and long term problems.
Power Handling
Root Means Square. RMS. This strange little acronym is indicative of how much power the speaker can comfortably handle for a sustained period of time. It is also referred to as to as continuous, or nominal power. Just to complicate matters further, some speakers (particularly the older ones) only list a ‘peak’ power rating, which is essentially a rating for the mechanical limit of the speaker, and often represents how much power a speaker can take before it produces audible distortion as opposed to what a speaker should be paired with for the best possible sound.PMPO (peak music power output) is essentially the measure of the speaker operating at its limit. It should never be used as a sensible measure for pairing with an amp… unless you really dig damaged speakers of course.
Sensitivity
Pictured: delicate speakers
The last thing to consider is… ‘sensitivity,’ refers to the speakers ability to turn the power from the amplifier into sound. It’s pretty gosh-darn crucial to the whole ‘hi-fi’ (or even music reproduction) thing. Measured in decibels (dB), the best way to understand it is the higher the rating, the more efficient the speakers are. An incredibly sensitive speaker (90dB or above) is efficient enough that it will need a lower power amp for its optimum. A happy loudspeaker is one which operates at a comfortable level of power.
Pictured: a happy speaker
The bottom line is… yes, there are options. Many, many options. But there are many many ways in which you can cause your system damage if you don’t take some care. All of the units above will usually be stated clearly on the packaging of the items – and a quick google search (or phone call to a handy expert) can put all of your troubles to rest. The best rule of thumb is… a powerful amp is nothing without the speakers to match, and vice versa. Bigger isn’t always best and neither is louder, or more powerful. It’s all about finding the right balance… and only there will you find the right sound.
That right there was an oversimplification of a very complex topic. If you want some genuine, solid advice on which amp/speakers would best suit your speakers/amp, then give us a shout.There aren’t many combinations we haven’t already tried.