What would be the result of connecting 4-ohm DIY speakers to my Onkyo amplifier which specifies a 6-ohm minimum speaker impedance?
I know it's something you're not *supposed* to do, but what's the real deal? I'm no serious audiophile, and I don't listen loud. Just looking ahead at my next couple of projects and evaluating options.
Thanks much,
Cam
I know it's something you're not *supposed* to do, but what's the real deal? I'm no serious audiophile, and I don't listen loud. Just looking ahead at my next couple of projects and evaluating options.
Thanks much,
Cam
If you really want to find out open up that Onkyo amp so you can measure the supply rail voltages and see what output devices are used. Look up the datasheet for the devices and determine if they can source/sink current that will be drawn by a lower impedance load while being operated at the amplifier's supply voltage.
If you don't want to do all that I would wager that the Onkyo amp will be ok driving a lower impedance load as long as you don't push it. If you find yourself turing up the volume and it starts sounding worse then the amp just wasn't designed to be worked that hard.
If you don't want to do all that I would wager that the Onkyo amp will be ok driving a lower impedance load as long as you don't push it. If you find yourself turing up the volume and it starts sounding worse then the amp just wasn't designed to be worked that hard.
I'm sorry but I don't agree at all with allowing a receiver that was designed to run a 6 ohm load running a 4 ohm load. The engineers that designed it came up with the minimum load specification and that should be followed to the letter.
Prior logic and reasoning is like saying that its ok to play with fire as long as the fire is small because you might only get burned a little. Well, you play with any fire and you will get burned. You overload any amplifier that is NOT designed for it and it will sooner or later let out the magic smoke.
I suggest that if the amplifier is NOT designed to run the load you take it to the local flee market and promptly sell it and purchase one that will.
Prior logic and reasoning is like saying that its ok to play with fire as long as the fire is small because you might only get burned a little. Well, you play with any fire and you will get burned. You overload any amplifier that is NOT designed for it and it will sooner or later let out the magic smoke.
I suggest that if the amplifier is NOT designed to run the load you take it to the local flee market and promptly sell it and purchase one that will.
Consider that loudspeakers do not present a flat impedance vs frequency and that some speakers will actually have a much lower impedance than nominal at certain frequencies and the nominal load specs are more like guidelines than set in stone rules.
That is basically what I was saying. You can safely use lower impedance loads as long as you don't overload the amplifier. Distortion will increase rapidly as the amp becomes overloaded, so trust your ears and turn it down if you start hearing a lot of distortion. Simple as that.
That is basically what I was saying. You can safely use lower impedance loads as long as you don't overload the amplifier. Distortion will increase rapidly as the amp becomes overloaded, so trust your ears and turn it down if you start hearing a lot of distortion. Simple as that.
Hi,
Amplifiers rated as 8 or 6 ohm loads generally have aggressive
protection to stop them thermally overheating. They will struggle
with 8 ohm reactive loads just as much as 4 ohm resistive loads.
Generally speaking the protection works and if you use 4 ohm
speakers with 8 ohm amplifiers you do not get any more power,
in some cases less, depending on the protection.
Its not a good idea if your a party animal, but generally it is OK.
/sreten.
Amplifiers rated as 8 or 6 ohm loads generally have aggressive
protection to stop them thermally overheating. They will struggle
with 8 ohm reactive loads just as much as 4 ohm resistive loads.
Generally speaking the protection works and if you use 4 ohm
speakers with 8 ohm amplifiers you do not get any more power,
in some cases less, depending on the protection.
Its not a good idea if your a party animal, but generally it is OK.
/sreten.No, No, No!!!!
When you use a lower impedance load you are overloading the amplifier.
The amplifier was rated for a load not to be less than 6 ohms period.
Where does it state you can use a 4 ohm load?
It surely also doesn't state that if you don't push it a 4 ohm load is ok.
The only instance where you can get away with this is with a tube amplifier.
Since I do this for a living I do take the numbers seriously. The load is no different than what it would be if the amplifier was driving a 70 volt transformer and a run of 70 volt speakers.
If for example the amplifier was driving a 70 volt transformer and the amplifier was rated to drive a 50 watt load and the load on the amplifier was say 75 watts the amplifier would be overloaded.Therefore the 4 ohm load does in effect present an overload to the amplifier when the amplifier is rated for a 6 ohm load.
The amplifier was rated for a specific minimum load and saying that I'm not pushing it hard therefore I can run a load that I choose to run just plain isn't smart. It certainly isn't good advice to give someone when they deserve an honest answer to a question.
Hmmm..........
Someone seems to think rating an amplifier at 8 or 6 ohms is a get-out
clause for the manafacturer such that if too low impedance speakers
are connected its not their fault if the amplifier blows up.
This not generally true, most commercial mainstream amplifiers are
protected against any load, the rating is recommended loading.
70V/ 100V line systems are a classic case where you cannot have your
cake and eat it, power limiting is effected by the step-up transformer
rather than overloading the amplifier.
The simple fact is an easy non-reactive 4 ohm load is easier than a
highly reactive 6 ohm load, the truth is not told by the numbers. One
should always regard an 8 ohm (resistively) rated amplifier with deep
suspicion as to it load driving capability and one should also think
about what 8 / 6 / 4 ohm nominal impedance actually means.
sreten.
Someone seems to think rating an amplifier at 8 or 6 ohms is a get-out
clause for the manafacturer such that if too low impedance speakers
are connected its not their fault if the amplifier blows up.
This not generally true, most commercial mainstream amplifiers are
protected against any load, the rating is recommended loading.
70V/ 100V line systems are a classic case where you cannot have your
cake and eat it, power limiting is effected by the step-up transformer
rather than overloading the amplifier.
The simple fact is an easy non-reactive 4 ohm load is easier than a
highly reactive 6 ohm load, the truth is not told by the numbers. One
should always regard an 8 ohm (resistively) rated amplifier with deep
suspicion as to it load driving capability and one should also think
about what 8 / 6 / 4 ohm nominal impedance actually means.
sreten.The only way I can see this is that the speakers are 4 ohm nominal impedance which I see as a load that could very well dip to 2 ohms or so on the low end.
Still want to gamble? Its your amp and I'm sure it can be rebuilt again.
However its an Onkyo and that isn't the most robust unit around.
diesel_88 said:
The arithmetic mean is "do it if you want and don't blame me if it breaks
"There are too many "if's" in the question. Which 4 ohm speakers, which amplifier, how low a level?
I ran an older Onkyo with an 8 and 6 ohm rating (it was rated for "dynamic power" into 4 and 2 ohms) with a pair of 4 ohm speakers. I listened at very low levels (<80-85dB most of the time) and had 97dB sensitive speakers. The speakers would get reasonably loud driven by a walkman. Looking at the board, there are some small value resistors (~1 ohm/1watt IIRC) that at some point got hot enough to darken the board. They were obviously intended to get hot as they were mounted above a hole in the board.
The only times I played loudly was for ~5 minutes at a time to shut up my noisy neighbors. One time an upstairs neighbor played the Eagles Hotel California loudly about 6 times in a row, so I played it at ~12 o'clock on my receiver and I never heard loud music from that neighbor again.
About 116dB in room on that one I had a speaker protection relay failure at 4 years, not caused by overloading, AFAIK. The amp still works, but one of the channels cuts out every now and again after 20 years of use. Turn it up a bit and the channel comes back because the protection relay contacts arc. I'd replace the relay, but it is a pain to get at. Maybe I'll pull off the relay cover and see if I can burnish/clean the contacts.
Cal Weldon said:
Playing around with ohms law, say you have a 50W / 8ohm amp.
50 Watts Rms at 8 ohms is 20Volts Rms.
20/8 (or 50/20) is 2.5 amps Rms
2.5 amps Rms into 4 ohms is 4*2.5^2=25 Watts Rms
Resistively, you are in the same operating window a long as you are under 25Watts at 4 ohms. To give yourself some kind of safety factor you might then derate the amp by a factor of between 2-4 (consider your 50W 8ohm amp to be a 12.5-25 Watt / 4ohm amp) and my opinion is that you will probably be safe in doing this. The trouble is knowing where 25 watts is for whatever music you are listening to. To be really sure you need to monitor operating temps, etc. In the end, buying an amp that is rated to handle the load is probably simpler
BTW, full output from a typical receiver from a CD source is frequently reached with the volume control at the ~10 o'clock position, and actually lower for much music recorded recently. This is quite hard to gauge with newer digital readout volume controls. In other words, half way up is not half power. Half way up is most likely "nasty clipping" level. Volume control position has little or no consistently predictable relation to power output, and it is most definitely not a linear relation.
I used a test CD and a calibrated VU meter to test the output of my old Onkyo amp for various level control settings. Rated power was reached when the amp volume control was set to 14 out of 40 (3.5 of the once common 10) divisions, with a full scale CD signal at 1kHz. Much of the music I had at the time was recorded at around -20dB, but over the full range of frequencies, for about the same average power demand. Modern pop music is often recorded 6-10dB louder and has a demand much (4-10 times, in this example) higher. For example, what would have been within power limits with old recordings at a setting of 14 on my volume control now needs a setting of 6 or 8 out of 40 with new music to prevent clipping. So you may not think you are listening "loudly", based on volume control position, when in fact you really are.
I can definitely vouch for what Ron E is saying. I used to own a set of decent HiVi Aluminum 8" woofers in my home studio. This studio is driven by a large QSC PLX2402 amplifier capable of delivering up to 2400 watts in bridged mono mode. As anyone who has used Pro-Audio gear before knows, typically, amps of this nature have two gain controls that vary the INPUT sensitivity, not the OUTPUT gain. I had it in stereo mode with a couple nice DIY studio monitors rated at 230 watts each @ 6ohms, at about 1/2 max input gain - no sweat for this amp, and speakers should have been safe.
One evening, while listening to some music in the basement at moderate levels (wife was asleep upstairs), I decided my beer was getting low, so, I decided to venture upstairs for a refill. Before I made it back to the basement, the randomizer on my PC (which was the DJ for the evening) decided to pick some Jurassic 5, which was recorded at significantly higher gain than the early Floyd before it.
Needless to say, the amp, without modification of any volume adjustments, managed to literally hammer the voice coil through the aluminum cones - leaving a perfect cylinder imprint in the cone. Pretty neat in hindsight.
Not all music is recorded the same, and even if your speakers claim to be 4ohm, they'll probably be more like 2-3ohms at certain frequencies, and a setting of "low" on the amp volume control doesn't always mean "low." I learned this the hard way...
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