Your speaker’s impedance matters!! A very low impedance presents a very difficult, even dangerous task for your amp to drive.
We’re always encouraging amps, like NADs at reasonable pricing, that are able to drive low impedances. With an NAD you can buy whatever speakers you like the sound of, with no worry as to their impedance. But NAD is unusually OUTSTANDING at its price points.
The big box brands like Yamaha integrateds for example, say right on them that you can run 8 or 4 ohms speakers, but you need to use their back panel protection switches based on your speaker choice. Keep in mind, this is for 4 or 8 ohm speakers. What if your speaker is 2 ohms?! YEP.
I’ve had people say, no problem. My speaker says it is 4 ohms, or maybe even 8. So I’m all set. Not so fast….
Your speaker has a rated impedance. It is likely 4 or 8 ohms. But that’s nominal, or average.
What does your speaker show your amp in the most challenging bass frequencies?
I’m sorry to tell you that even if they are rated at 4 or 8 ohms many speakers go FAR lower in their impedance behavior. This is a challenging and sometimes dangerous problem for your big box amp that will begin to current limit, or even shut down and BREAK at impedances under 4 ohms. Indeed, there are many amps with pretentious reputations that go to ashes at 1-2 ohms!
Some customers assume because their speakers aren’t old, the impedance curve can’t be a problem. It CAN.
Let’s take a look at a few measurements- which are different from advertising claims. Stereophile measures impedance and efficiency among other specs. These tests are from speakers in 2021. These concerns are not just for old speakers.
Dynaudio Confidence 30, $21,000 Per Pair
It is rated at 88dB SPL and came quite close to that rating.
It is rated at 4 ohms. “Drops below 2 ohms between 53Hz and 101Hz, and between 228Hz and 372kHz. Value is 1 ohm from 68Hz to 80Hz and 1.28 ohms at 279Hz.”
Focal K2 936, $6000 Per Pair
It is rated at 92dB SPL. It tested 90.
It is rated at 4 ohms. “Drops below 2 ohms in three regions- 27-38Hz, 65-141Hz and 363-895 Hz, with minimum values of 1.8 ohms at 32Hz and .97 ohms between 87 and 90Hz. The Aria 936 must be used with amplifiers that don’t have problems driving 2 ohms loads.”
KEF LS 50 Meta, $1500 Per Pair
This new speaker got a very positive review, but:
It is rated at 85dB SPL. It tested close at 84.5.
It is rated at 8 ohms. “LS50 Meta has minimum of 1.66 ohms between 135Hz and 140Hz and 1.7 ohms between 660 Hz and 725Hz, both regions where the music can have high energy.”
Magico A5, $24,800 Per Pair
It is rated at 88dB SPL. It tested 86.5.
It is rated at 4 ohms. “Drops below 2 ohms between 53Hz and 120Hz, with a minimum value of 1 ohm at 70Hz. The A5 must be used with amplifiers that don’t have problems driving 2 ohm loads.”
PSB Synchrony T600, $8000 Per Pair
It is rated at 89dB SPL. It tested 87.
It is rated at 4 ohms. “Drops to 1.8 ohms at 35 Hz and to 2 ohms between 74Hz and 85Hz, and between 2.3kHz and 3.1 kHz.”
Wilson Sabrina X, $18,500 Per Pair
It is rated at 87dB SPL. It tested 89.
It is rated at 4 ohms. “Has less than 2 ohms between 65Hz and 275Hz, with a minimum value of 1.1 ohms at 90Hz, where the music can have high energy. The partnering amplifier needs to be capable of driving 2 ohms without stress.”
Wilson Alexx V, $135,000-151,000 Per Pair
The reviewer liked this mucho expensive speaker with a highly didactic review.
It is rated at 92dB SPL. It tested close, 90.8.
It is rated at 4 ohms. Impedance “Remains between 2 and 4 ohms for almost the entire audio band, with a minimum value of 1.9 ohms between 242Hz and 270Hz. Drops below 2 ohms over most of the midrange and mid-treble regions, with minimum values of 1 ohm between 50hz and 64Hz, 1.15 ohms between 197Hz and 203Hz, and 1.05 ohms between 3kHz and 3.16kHz. Owners of Alexx V need to match the speakers with amplifiers that are unfazed by very low impedances.”
Summation
We are not saying these are bad speakers.
We ARE saying these are challenging speakers to drive.
As you can see, in discussing most of these speakers the magazine makes a special effort to warn you about the interface with your amplifier!
Your amp may not be up to the task. In fact, your amp may be living precariously if you drive it kinda/sorta hard with speakers like these.
If you are thinking all 8 ohm speakers are easy for your amp to handle, just look at the LS 50 Meta above that drops below 2 ohms for part of its electronic fingerprint. The rating obfuscates the mismatch you may encounter.
We recommend you buy an impedance invariant amp to be safe and get the best sound. NAD is a great place to start. They make a wide line of impedance invariant integrateds and power amps.