Is it safe to use a 6-8 Ohm rated AVR with 4 Ohm speakers?

[sensite]

Hi everyone,
Recently I've bought a pair of Dynaudio Focus 140 in excellent condition, currently driven by my Yamaha R-S700. While the combination already sounds great, I still have an old Denon AVR-X1000 sitting in my attic, and I'm considering giving it a second life.
The main reason would be to take advantage of Audyssey room correction and to integrate my Klipsch Synergy Sub-10 more seamlessly.
However, I'm a bit concerned because the Dynaudio Focus 140 are rated at 4 Ω, while the Denon AVR-X1000 manual states that it is intended for 6–8 Ω speakers.
My listening habits:
Mostly music in stereo, but I also enjoy watching action movies.
I like listening at fairly high volumes.
The Klipsch subwoofer would handle the low bass, so I'd probably set a crossover around 80 Hz, reducing the load on the AVR.

My questions are:
Is it actually safe to run the Focus 140 with the AVR-X1000?

Do you think Audyssey and proper bass management would be worth the switch from the Yamaha, or should I just stick with the stereo receiver?

 

[DonH56]

While rated 4 ohms, the impedance curve from Stereophile* shows they are mostly above that. They are also rated at 86 dB/2.83 V/m, not very sensitive, as is typical for bookshelf speakers. Worst case the receiver will run hot and shut down. Chances are you'll be OK but you will have to test and see under your listening conditions. Make sure there is plenty of space around the receiver for airflow, and you may (or may not) need a fan on it.

As for Audyssey, I'd be inclined to use it, mainly to simplify the task of integrating the subwoofer. Offloading deep bass from the Dynaudio's is a good plan IMO.

FWIWFM - Don

* https://www.stereophile.com/content/dynaudio-focus-140-loudspeaker-measurements

 

[OldTimer]

You will damage the amp, not the speaker. The amp will run hotter, sometimes turn-off. Please try to run the amp at high volume for a few minutes if it becomes hotter or not.

 

[Redacted]

Try it and see. In the end, it's a spare amp and most current is expended at low frequencies which you are trying to dial out. It's current that makes an amp hot. The only other thing is the possibility of oscillation (instability), but I'd be surprised. Just make sure you have a big bucket of water nearby

 

[amirm]

As a general matter, the impedance rating of speakers is nonsense marketing number. As Don says, the actual impedance is a curve, not a single value. Same is true of the specs for the specs of AVR. As noted, if the amp doesn't like the load, it will shut down.

Of course there are crazy speakers that are in reality 2 ohm or lower. Those are special cases/exceptions.

 

[DonH56]

What @amirm says about speakers and, as he notes, a similar analysis applies to amplifier ratings. Most amplifiers are rated fairly conservatively to meet FTC standards that require preconditioning and full-power distortion testing. Designers also realize that in the real world a 6-ohm nominal speaker could easily drop to 3 ohms or less at certain frequencies. An amplifier's ratings are usually based upon current, distortion, and thermal limits for long'ish-term performance and not short peaks or narrow impedance dips. An amplifier rated for 8-ohm loads will generally easily tolerate a minimum of 4 ohms as long as it is not constant and at high levels (e.g. loud, high SPL). Very low impedances are usually OK at low listening levels, and at high levels current or thermal limiting may activate to protect the amp (and speakers). If you have trouble holding your hand on the top of the amplifier during or at the end of a listening session, even if the amp does not shut off, a fan cooler is a good idea IMO. There are AVR-specific fan plates, but IME a large but fairly slow (quiet) computer fan running off a simple wall wart power source is much cheaper and just as effective. Since hot air rises, and I do not relish blowing dust into the amp, I would place the fan(s) on top of the amplifier blowing upward to pull cool air in from below.

Below is the impedance curve from the Stereophile article. Above 1 kHz, it is essentially an 8-ohm speaker, falling below 6 ohms around 500 Hz, then to 4 ohms around 170 Hz or so. Phase is inductive (positive, an easier load) until about 200 Hz, then drops to a capacitive low around 90 Hz, which is probably about the worst-case load for the amp. At that point, your subwoofer is taking over, so the Dynaudio will need less power from the AVR. If you can place the subwoofer between the speakers, albeit not necessarily the best spot for flattest bass, then you could raise the crossover a bit to 90 or 100 Hz to make it easier on the AVR. But you may find that unneccessary unless you sit fairly far away and listen at very loud levels.

All a long way of saying you'll probably be fine, give it a go and find out. The Dynaudio's look like very nice speakers, though you did not say what you are using now.

 

[Redacted]

As I recall saying, just try it...
You'll be fine.
I've done all sorts of weird Frankenvolt experiments to see if I can start a fusion reaction and have failed. Or, put it another way, for the last 50 years I've always been a fixed 20 years from fusion.

 

[Beave]

While rated 4 ohms, the impedance curve from Stereophile* shows they are mostly above that. They are also rated at 86 dB/W/m, not very sensitive, as is typical for bookshelf speakers. Worst case the receiver will run hot and shut down. Chances are you'll be OK but you will have to test and see under your listening conditions. Make sure there is plenty of space around the receiver for airflow, and you may (or may not) need a fan on it.

As for Audyssey, I'd be inclined to use it, mainly to simplify the task of integrating the subwoofer. Offloading deep bass from the Dynaudio's is a good plan IMO.

FWIWFM - Don

* https://www.stereophile.com/content/dynaudio-focus-140-loudspeaker-measurements

JA estimated sensitivity at 86dB, that's 86dB/2.83V/m.

 

[Holmz]

…
However, I'm a bit concerned because the Dynaudio Focus 140 are rated at 4 Ω, while the Denon AVR-X1000 manual states that it is intended for 6–8 Ω speakers.
…

There is a reason for having specs.
The Denon says it’s rated for 6-8 ohms, and the speakers say “4 ohms”.

It does not seem like a mathematically difficult concept.

 

[Mr. Swordfish]

How loud are you planning to push your system? A typical home speaker will produce something like 85 dbSPL at 1 watt 1 meter, so unless you're a metal head you're only asking for a watt or two for normal listening. The amp should handle that, even at loads that are below 4 ohms.

I don't know what the rated output for that amp is, but if you're pushing it's limits, it will probably run out of current at 4 ohms, with distortion and overheating the usual symptoms. So, if you're going to be listening at 105db SPL, you'll be asking for 100 watts there will probably be "issues". If not, it's highly unlikely to break.

.

 

[DonH56]

JA estimated sensitivity at 86dB, that's 86dB/2.83V/m.

Corrected, thanks.

 

[Mr. Swordfish]

The Denon says it’s rated for 6-8 ohms, and the speakers say “4 ohms”.

It does not seem like a mathematically difficult concept.

If only it were that simple.

Real world speakers have an impedance curve that varies with frequency, so an "8 ohm" speaker may have an impedance of half that at certain frequencies. And since impedance is a complex number with a "real" part (resistance) and an "imaginary" part (reactance), with amplifiers often having trouble driving highly reactive loads, modeling it as a simple integer inequality is, well, simplisitic.

BTW, I have 2 Denon receivers, both of which happily drive 2.7 ohm loads (a pair of 8 ohm and a pair of 4 ohm speakers in parallel).

To oversimplify things somewhat, it's basically about whether the amp can provide enough current into a low impedance load at the specified voltage. If you're listening at a normal domestic volume, the voltage is low and so is the current; the amp can probably handle that.

 

[Holmz]

If only it were that simple.

Real world speakers have an impedance curve that varies with frequency, so an "8 ohm" speaker may have an impedance of half that at certain frequencies. And since impedance is a complex number with a "real" part (resistance) and an "imaginary" part (reactance), with amplifiers often having trouble driving highly reactive loads, modeling it as a simple integer inequality is, well, simplisitic.

BTW, I have 2 Denon receivers, both of which happily drive 2.7 ohm loads (a pair of 8 ohm and a pair of 4 ohm speakers in parallel).

To oversimplify things somewhat, it's basically about whether the amp can provide enough current into a low impedance load at the specified voltage. If you're listening at a normal domestic volume, the voltage is low and so is the current; the amp can probably handle that.

^Yeah probably.^

But it gets more certain when an amp rated for 4 ohms, happens to be powering an 8 ohm speaker pair.

In the OP’s case it may work at lower volumes and it may even work at higher volumes.
It is just far from being “guaranteed” to work at the higher volumes.

Hi everyone,
Recently I've bought a pair of Dynaudio Focus 140 in excellent condition, currently driven by my Yamaha R-S700. While the combination already sounds great, I still have an old Denon AVR-X1000 sitting in my attic, and I'm considering giving it a second life.
….

Sure… try it.

You’ll either give a second life, or remove the current one.

You options seem to be:
- try it.
- sell it.
- or use it for some other room.

 

[amirm]

It is just far from being “guaranteed” to work at the higher volumes.

It is a de-facto guarantee as just about every speaker I have tested, has a minimum impedance of around 4 ohm. If AVRs had trouble with 4 ohm, they wouldn't have had a single happy customer!

 

[Redacted]

It's worth finding out at which frequencies a given speaker dips to a low impedance, because big current is only really needed at low frequencies, so 3 ohms at 15khz for example is not going to matter much.