In one room of my house I've driven some fairly large (three-way with 10" woofers) four-ohm speakers (R. A. Labs Reference 2A) often quite loudly for over 20 years with eight-ohm receivers and had no problems of any kind. The receivers involved were good ones (none died from this use, I merely upgraded), however, and I suppose something such as an entry-level Sony would possibly have had problems.
Rare indeed is the amplifier that will smoke if the load has a lower impedance than normal, as long as it isn't Too low. Keep the volume well below the point where the amplifier clips, and it will most likely be OK.
Another piece of advice with this. Is to use a cooling fan on the amp, and give it plenty of breathing room. It's not just the power supply the cheap out on. It's also the heatsinking/cooling sometimes.
I ran, for 20 years, a pair of speakers I thought were 8 ohm that were actually 4 ohm. They were single drivers, made in 1957, so I thought the grunge I occasionally heard from them was the voice coil rubbing. I had someone from Great Plains Audio tell me how to test for speaker rubbing, it turns out pushing on the cone with you fingers is not it, and to my amazement, the speakers were fine. I used a 6 watt transistor amp for this test, not the 2 watt triode I bought the speakers for (they are 106db efficient). It was in doing research after this discovery I discovered they are actually 4 ohm speakers. The grunge I was hearing was actually my single ended triode amp oscillating into the low load. After years of this, neither my speakers nor amp were damaged, it just didn't always sound very good. The amp has an 8 ohm tap and I now run it into a 16 ohm load with no problems.
I know that some amplifiers have thermal protection so that if you did overload the amp with low impedance speakers the amp would probably go into protection and shut down. Then you could power cycle the amp to recover after it cooled off. I've placed resistors in series with tweeters that had more sensitivity than the woofers to balance the sound between bass and treble in a two way system. I do like building my own speakers using raw drivers and crossovers.
I needed to tame the high frequency response in my speakers due to room interaction. There's a 3.3 ohm 5W R in series with the tweeter. There's no way I'd put a resistor in series with a woofer though.
Be careful! Those 2 ohm resistors are gonna get mighty hot! Especially at high listening levels. Go for at least a 20 watt 2 ohm resistor. Otherwise, I'm sure your 6 ohm speakers will be just fine. IMO.
Don't put reistors between the speaker and the amp. That will just dull the sound. You should rather just play at rather low volumes. Or better: Get a better amplifier.
You can get resistors with aluminium housings with heatsink fins, but not sure if they will be audio quality. If heat is an issue it is easy enough to rig up a 40mm, 5v pc fan to keep them cool.
Adding resistors in series will ruin the damping factor and that means your speaker cones will not be able to follow the intended wave motion as precisely, e.g. a drum wIl sound more boomy.
True, although the DC resistance of the speaker in fact is also a resistance in series with that speaker coil. A speaker with 6 Ohm impedance rating typically has ˜5 Ohm DC resistance, which is in fact already has a 5 Ohm resistor in series. So adding another 2 Ohm won't change the boomy-ness as much as one would expect.
That doesn't mean everyone will with every amp though. I own a Sherwood receiver that's famous for not being able to work with 4Ohm speakers at all. And remember there's a big difference between an amp that's only rated at 8 Ohms, but can play at 4 Ohms. And one that specifically warns not to use less then 8 Ohms, as is the case with my Sherwood. To be fair though. There aren't many like this, and they're mostly all cheap amps/receivers. But that's the point. They're built to sell cheaply. So they skimp on the power supply, and/or the heatsinks.
It really has more to do with not pushing the amps too hard. Those of us who paid attention to clipping were more successful in not having protection circuits turn on.
If it were he other way around, for example 16 ohms speakers, you'd lose power but even it clipped the amp wouldn't get hot. While a heavy load will greatly increase the heat. I've had friends twist the wires together and hook up 3 sets of speakers to a 8 ohm amp -- something like 100 watts of heat for 5-10 watts out ... maybe you've known a few.
Would've been helpful to say what type of speakers they are for sure. A common case is ported enclosure speakers which have a lot of impedance rise - the drivers and crossover outside the enclosure may measure 4 ohms, but once in that type of enclosure their minimum impedance may be as high as 10 ohms for example! Also would've been good to know what amplifier is being used - some can have a conservatively rated minimum impedance and I have one rated 8 ohms minimum but it doesn't complain driving *sealed* enclosure 4 ohm rated speakers which are much closer to a true 4 ohm minimum impedance.
You could use an auto transformer and virtually eliminate losses you would incur using a resistor. Another benefit of the auto transformer is that you get the benefit of the full damping factor of the amplifier that the resistor would likely adversely affect. The full back emf of the speaker would work against the amplifier’s low internal impedance resulting in greater control of transients. A 48V-115V control transformer wired in an auto-transformer configuration is nearly perfect to couple your 8 ohm rated output to a 4 ohm speaker load. For a 100 watt amplifier, the transformer would only need to be 30 VA rated. I’ll bet some specialty transformer company probably makes a transformer that already does this trick.
If you add 2 Ohms of resistance in front of the speaker it will have a significant impact on the bass response of the speaker, outside of the drop in volume. The Q of the speaker will change and the cabinet that was designed for it will no longer be appropriate, less of an issue in sealed enclosures than ported ones. The bass will likely be less well damped, more "boomy". There is DC resistance in the crossover components going to the woofers but this has been accounted for in the design in any competent speaker design. Admittedly the resistance goes up in the speaker as the voice coil heats up at higher volumes but this is again a design consideration and is small by comparison.
I used a 100 wpc $100 Sherwood receiver 11 years ago to check the phasing after recapping the crossover network on my 4 ohm speakers while the woofers were out for reforming and even at low level and the woofers disconnected the receiver shut down after just a few moments every time to protect itself.
Disclaimer - I’m not even close to being an electrical/electronic engineer-- I’ve been running the nominally rated 4 ohm unifi ub5 in the 8 ohm setting for the past month. I don’t listen at ear splitting levels so it sounds great and the receiver never gets hot. It’s always been warm to the touch but never got hot and the auto shut down never engages. The receiver I’m using now is the Yamaha r-n803. Based on what Audioholics.com said those amps that have that feature of switching ohms from 8 to 4 are just to meet certain safety inspections (think CE and UL) and to do so moving that switch over to 4 ohms is crippling the amplifier so it holds back the electrical current driving the speakers. They have run tests on the Yamaha a-s801 amp section running 8 and 4 ohm on an 8 ohm load. Anyway take this with a grain because do not know what I’m talking about. Not really. Also wanted to add a speaker is nominally rated. Speakers will perform dependent upon the music - ohms will fluctuate. Again I don’t know what I am really talking about. Anyway I have experienced nothing bad from running a 4 ohm inefficient unifi un5 on an 8 ohm load.
I have my 4 Ohm Speakers connected to an Amp min. 8 Ohm and it works fine for 3 Years now even at loud volume. The only thing I noticed is that there's more heat dissipation. I read a little about building an amp and when you calculate the heat sink the dissipation value is inversely proportional to the lmpedance of the speaker, as far as I know😅, because a 8 Ohm 100 Watt amp could serve for ex. 150 Watts at a lower impedance if turned up fully. Also the 4 Ohms mean that that's the lowest impedance of the speaker but with different frequencies the value may be higher, without an Impedance Correction circuit of course, so there shouldn't be much trouble. My amp still works fine. Just be cautious that the amp doesn't over heat. Im from Germany, so I hope my English isn't to bad :) and I didn't explain it to complicated. Have a nice day 👌
"Also the 4 Ohms mean that that's the lowest impedance of the speaker..." Actually it doesn't. The "nominal" impedance is as several speaker designers have stated is a somewhat fictitious number arrived at to keep the users of equipment happy. A "4 ohm" speaker's _measured_ impedance will nearly always dip below 4 ohms at some frequency.
"I don't know how the national standard, but in Germany there is a DIN standard which states that the Impedance of a 4 Ohm speaker cannot drop lower than 3,2 Ohm (one with 8 Ohm not lower than 6,4 Ohm)." That doesn't contradict what I wrote. The critical things here are that the amplifier's output devices dissipate more energy the lower the impedance. And some amplifier designs become unstable if the speaker impedance is too low. That is, the amp oscillates and energy dissipation skyrockets.
@@jonathansturm4163 I totally agree with you, but what I wanted to say is that in most of the frequency range the impedance doesn't drop that low, especially in the bass region where most of the power is drawn from the amp.
@@hififriend4512 This is true which is why I drew attention to the stability problem. When an amp goes into oscillation it's often at a very high frequency but nevertheless draws the excessive current that should trip the protection circuit built into modern amps. Heck, even back in the 1970s we had fuses for that purpose.
@@jonathansturm4163 true All in all I think it's not to dangerous to connect lower impedance, if you are careful of course 👍 Thanks for the good discussion, that's sadly something rare nowadays. Have a nice day!
At lower impedances the amp will get hot. Get yourself some 120mm computer case fans, they normally run at 12V DC but you can run them at less voltage to make them quieter (I run mine on an 8V wall wart and they are silent). Just point them at the heat sinks for cooling.
I found a small personal desk fan at Walmart for something around 5 bucks. It's got rubber feet, can be rotated for direction control, as in pointing up to extract heat and is 120 volts, so I have it plugged into a switched receptacle on my amp. Keeps it nice and cool and a lot cheaper than computer fans.
It would help to have more details. Many amps require a minimum of 8 ohm speakers if you connect 4 speakers and plan to play all four at the same time. I have rarely heard of speakers rated at 6 ohms. Using series resistors is not recommended because it will dissipate power as heat and affect the damping (control) of the speaker. Of course you can try and if the sound is OK with the person it is OK. Four ohm speakers will draw more current from the amp and may cause the signal to clip when played at the higher volumes if the power supply cannot handle the current draw. This is not good for the amp or speakers. Keep in mind the impedance ratings for speakers are "nominal" and vary greatly over the audio frequency range. Typically there will be points in the plot that are lower than the rated impedance. At one time I had a Marantz model 15 power amp. It was hooked up to AR-3a speakers that were rated at 4 ohms. The impedance curve of these speakers actually dips close to 3 ohms at some frequencies depending on how the mid-range and tweeter controls are set. At the resonance frequency it is slightly over 20 ohms. I was getting red lights on the amp when playing them moderately loud. I traded the amp in for a model 250 and had no more problems. Back in the day Acoustic Research published full specifications of the response curve, dispersion, and impedance characteristics of their products.
This is a good question to ask, and relevant to my setup. I have a pair of Plinius SA-50 amplifiers, which are stereo A/AB but can be switched into monoblock mode (hence why I have two). Now the manual states that in stereo mode I can connect speakers from 4 to 8 ohms nominal, but in monoblock mode only 8 ohms. I currently have speakers that are 8 ohms but have considered replacing them. GE Tritons have a nominal impedance of 8 ohms but reviews warn they can dip down to the 4 ohm region or lower. In Class A operation the amps are already running hot. Now I assume the speakers spend most of their time around the 8 ohm region and only dip part of the time, hence the 8 ohm nominal spec from GE so it should be a non-issue. Any thoughts Paul?
I connected 4ohm speakers to my 8ohm receiver and when I cranked up the volume the receiver went into protect. So now I only search for power amplifiers that can support down to 2ohm loads and only use 4ohm minimum speakers.
Is it Okay to turn of my Integrated Amp from the wall, without pressing the off button on the amp itself first. My parents keep offing the main plug at night without switching things off firat and my stereo amp turns off with it.
FWIW, I picked up a pair of Audio Physic MkII's (4 Ohm), and in my excitement to hear them, connected my cheap Onkyo TX-8555 (8 Ohm minimum) to listen to them. All I can say is, at "listening level", a puff of dense smoke was emitted, along with a wonderful burning electronics smell. I could have toasted bread on the top of it. That amp is now sitting on the dead component shelf.
What bullshit is this I see before me? From the Onkyo TX-8555 user manual: "If you make an incorrect setting for the speakers or the impedance values, the built-in protection circuit may be activated resulting in no sound output from speakers." www.manualslib.com/manual/115491/Onkyo-Tx-8555.html?page=13#manual
@@hom2fu Sorry guyz, that's what happened. I don't mean to spread any misinformation. I upgraded to a Yamaha RX-A1000 after that and the circuit protection worked just fine. I got tired of that tripping after a while though so I finally moved to an Emotiva A300 and haven't had a problem since. It just seemed like everything got really hot running an 8 Ohm amp into 4 Ohm speakers.
@@jonnyz69 Er... you did say "8 ohm minimum" and nowhere in the user manual does it say that. It does tell you how to connect a 4 ohm speaker with the warning that the protection circuit will trip if you get that wrong. There's any number of possibilities here: 1. You didn't set the switches correctly for 4 ohm operation 2. The protection circuit was faulty and failed 3. Your 4 ohm speakers' minimum impedance was lower than the average ... Yes an amplifier will run hotter into a 4 ohm load than an 8 ohm load. That's physics for you. My amp dissipates 100 W into 8 ohms and was measured to be dissipating ~175 W into 6 ohm speakers which is what I possess. The measurement was done almost 20 years ago and I cannot remember the exact figure.
There is no such thing as an 8 ohm amplifier. An amplifier's output performance varies with the load connected. A simple review of the owner's manual will tell you what loads are compatible with the amp's maximum output capabilities. I would never recommend adding series load resistors. Amps and speakers are either compatible with each other or not. At typical listening levels there is seldom an issue as described. Proper ventilation is always important.
You could have an amp with an 8 ohm output impedance, but it wouldn't be hifi. Ideally an output transformer-less amp would have an output impedance of 0. Most modern amps are some small fraction. And didn't tube amps with output transformers have taps for different loads? They might very well match the speaker impedance for maximum power transfer, but I'm not sure.
Sorry Paul I would NOT run a system i that matter. I know personally that will not work. I Fired 2 of Sony s top -of-the-line receivers A top-of-the-line Marantz In a matter of four weeks running 4 ohm speakers. So I replaced them with the anthem MRX 1120 was specifically stated that it could handle a 4 ohm load and paired it with a Rotel RB 1582 mk ll amp rated at 4 ohm
Speakers do not possess "an" impedance, they have a "nominal" impedance, a somewhat fictitious number. Nearly all speakers of interest to the audiophile have a nominal impedance of either 6 or 8 ohms and every amplifier I have come across is happy to drive either. This doesn't mean there are _no_ amplifiers so badly designed they are going to go up in a puff of smoke with 6 ohm speakers, but they are unlikely to have been manufactured for audiophiles' needs. There's a good explanation in _How to stop worrying about speaker impedance_ by ELAC's Andrew Jones: www.cnet.com/news/how-to-stop-worrying-about-speaker-impedance/
25 watt wire wound and non inductive would be best . Failing that use a 50 watt L-pad attenuator or even try two 4 ohm speakers ( they gotta be the same btw !! ) connected in series ..!
Suggestion - by all means, Do as Paul suggested, No resistors. But, "near field" Only ! That will force you to play at a "moderate" level … Loud for you; But NOT for your room. Just sayin'. ;-)
Modern digital amps have a protect mode. If the amp doesn't like the speakers impedance, then it will likely trip the protection mode. If it doesn't then you will want to watch temps. Rather than a resistor to match ohm rates. Just add another 4 ohm speaker to each channel in series. Wasted energy with resistance.
It does. For the same voltage output on the power amplifier, half the load impedance (like going from 8Ω to 4Ω) takes twice the power. Most amps just handle that, but not all.
So we add a say 10w 2ohm resistor in series. There goes the 12 gauge 99.9999999999% pure speaker wires purchased to get mightly good sound out of the system 😂🤣
BAD Advice. It depends on the quality of the amp and the actual minimum impedance of the speakers. The given Ohms are the nominal. Current drain will double - see Ohms Law - which can put a large strain on the amp, as well it can be influenced by the speaker cables since their effective resistance will double (again, see Ohm's Law)
At 28C inside (37C in shade outside) in middle England my Amps been off for a few days :-( I do have AC Infinity T8 ‘top to rear flow’ fan unit, however, as not used to this heat all day and night long I’m not in the mood to listen to music anyway. Looking forward to cooler times. As for ohm matching, my Amp can be configured for 4/6/8 ohms using the lowest setting for mismatching AV speakers but it’s left at 8 even when surround speakers are engaged - all reviewer folk seem to advise not setting below 8 as it can affect sound quality. Does it create more heat, not really sure but does seem to lose some dynamic power if set to match the 6ohm lowest pair. I hope there’s not a new trend in this low ohm matching, seems to lower voltages so you don’t get the power for transients even at moderate volumes.
Could 10W 2 ohm resister get hot enough to start a fire on a carpet, by doing what Paul said in this video? Come on Paul, I want PS audio focusing on making great audio gear at great price and not waste lots of money getting sued by people with burnt down homes. Take down this video, or at least edit it with stronger warnings. Or are you certain that what you said people can do in this video will not cause any fire? What's the highest temperature the 2 ohm resister could reach following what you said in this video? Could something people have in their homes catch on fire at that temp? If people put 1W 2ohm resister instead and burn their house down, can you win in court?
