Okay, so you are, basically, wondering about pairing together speakers and amplifiers - good question! Let me start with the short and quick answer that may annoy you – 95% of consumer-grade/home speakers out there will work and perform admirably with 95% of consumer-grade amplifiers out there and you probably don’t need to worry excessively about it, particularly if you’re spending less than $500 on your equipment. Cool?
Okay, if you’re still feeling clueless and want to understand better… read ahead, then! I warn you, this gets a little technical, but you may still find it interesting. I’ll end with some fringe cases where speaker/amplifier mating will matter more.
Let me clear up some of those complexities – it’s not nearly has complex as it seems. The first thing to clarify here is… it doesn’t matter as much as you think it would and you shouldn’t sweat it much. There are a bunch of numbers on a set of speaker specifications, but only three of them really matter to you, the consumer, and I’ll take a minute to remove some of the mystery.
Power Handling – This number is the recommended maximum number of watts that should be input into the speaker, and usually is expressed as two numbers - peak and RMS. Peak is what the speaker can handle for shorts burst and dynamic peaks, and RMS is what is can handle for a long period of time. For example, if a speaker says its power handling is "peak 800 watts/100 watts RMS," don’t feed it an extended 800 watt signal unless you don’t care about them and you enjoy watching smoke pour out from them (NOTE: To actually do this, you'd probably have to have inefficient speakers and cranking them way past 100 db). Now… this is only part of the story. If you have a set of speakers that say they have a power handling of 60 watts, maximum, you can absolutely still hook them up to an amplifier or AVR that puts out at 100 watts/channel. You can do this and get away with it because the vast majority of your listening occurs at far below peak power... and is likely less than 2 watts per channel (see the bit below on sensitivity to understand why you don't need that much power for normal listening levels). However, you, as the user, will just have to be more judicious and careful with the volume knob; so long as you listen at “normal people” volume levels and don’t regularly crank it up to eleven, your speakers will probably be just fine and will suffer no ill effects. The vast majority of home users will never push their speakers to their maximum sound pressure levels (SPL’s).
“But!” you exclaim, “I love listening to my music at 100 db all the time! Are you SURE that it will be okay?!” Firstly, I doubt that, Mr. Deaf McDeaf-face… but even if that is true, yes, I am still sure that everything will be okay… or at minimum, you’ll know if you’re doing something stupid. Speakers have a maximum excursion level (basically, how far they go back and forth) that comes into play when they are really being pushed at high volume levels –this is known as an “xmax,” and you’ll see it listed on some woofer/driver specifications. When a speaker is hitting its maximum excursion limits, you’ll know it… because it will sound distorted and awful. 90% of people will never push their speakers to their maximum levels anyway, so don’t lose sleep over it.
“Well… I’m still nervous. I’ll just buy an amplifier that puts out less than max power handling of my chosen speakers!” Fun factoid: it’s more dangerous to your speakers to underpower them than it is to overpower them. When an amplifier is pushed too hard, it begins to “clip,” causing flat direct current (DC) to flow into your speakers and bottom out your drivers if you’re turning them up too loud. This is not only dangerous to your speakers (it will cause them to bottom out and start to cook your voice coils), but your amplifier as well (it overheats and burns it up). Like I said at that beginning of the Power Handling section… don’t overthink this. If you have an amplifier that puts out 200 watt or less per channel, you’re likely golden for 95% of speakers out there. If you have to err on one side, lean toward too much power and don't lose sleep on it.
Nominal Impedance – This number describes how hard a speaker to drive. You’ll generally see a number here that ranges between 4 ohms and 8 ohm. The majority of speakers’ impedance is 8 ohms, with a much smaller amount of speakers at 4 and 6 ohms. Occasionally, if you’re dealing with vintage units, you may find a speaker that is rated at 16 ohms, but this is rare. Correspondingly, some subwoofer drivers may have 2 ohms, but again, this is more of r/diysoundor engineering situation, and not something you’re likely to deal with as a home user.
If your speakers have a nominal impedance of 8 ohms or more… don’t worry about a thing. Buy any amplifier that fits your budget, power, and use needs, and rock out! If your speakers are 4 ohms, make sure you buy an amplifier that can drive them. The pertinent specifications will be listed on your amplifier sheet, usually something like, “40 watts into an 8 ohm load, 70 watts into a 4 ohm load,” or similarly stated. If it says something like that, great, you’re good. If an amplifier doesn’t list a 4 ohm wattage load, or tells you that you shouldn’t do it… well… I don’t advise that you do it. If you hook up a 4 ohm speaker to an amplifier that only supports 8 ohm loads, it might be fine… or it could overheat and destroy itself.
Technically, this question could go really, really deep, but that is not the point of this guide. If you want to read more, check out this guide or do additional Google research. Like I said, earlier, this is meant to be more of a broad guide than a specific case… don’t overanalyze it. Read the manual for your potential amp purchase and follow its guidance.
Sensitivity – This spec may occasionally also be listed as efficiency. It’ll be listed as “X db/watt,” or “X db efficiency” (these would mean the same thing). This basically describes how much SPL (or how loud) the speaker can generate with a given amount of input power. It is usually between 82 – 100 db/watt, although it is possible that you may find lower or higher in very rare cases. A speaker of higher efficiency is usually better at recreating extreme dynamics in your music, and can be driven to higher volumes with less input. Given that the majority most most people's listening occurs far below 95 db, you're probably not actually using nearly as many watts as you think you are... likely less than 1 watt for most of your listening! Read here for more information..
FRINGE CASES: Okay, fine, lets cover these, knowing these are not common.
Occasionally, depending on speaker selection and use case, you may really, genuinely need a good, specialized amplifier to drive them properly. First, if you are using a single stereo amp to drive multiple sets of speakers (most stereo amplifiers have multiple taps on the back for a second set), you need to be very careful that you read the directions carefully about what impedance speakers you hook up. Usually, you shouldn’t use 4 ohm speakers in this situation. Your amp may be able to handle a single set of 4 ohm speakers, but if you try to drive TWO sets of 4 ohm speakers… it may go very poorly.
Also, another fringe case is unique or special speakers… for example, electrostatic loudspeakers (ESL’s) and magnetic planar loudspeakers (MPL’s). ESL’s and MPL’s can have wildly swinging impedance, and can drop as low as 1 ohm impedance. If you don’t have a powerful and capable amplifier that can handle such impedance drops, your amplifier could well be diving into a world of hurt.
This post originally appeared on r/BudgetAudiophile.