yif Posted September 5 Share Posted September 5 Hi, I am having difficulty understanding amplifier power ratings, especially if impedance is brought into the picture. For e.g. I note that the Cyrus i9 XR is rated 91w into 6ohm, while the Hegel H190 is rated 150w into 8ohm. What would the maths be here to equalise the two measures please? Thanks! Link to comment Share on other sites More sharing options...
andyr Posted September 5 Share Posted September 5 1 minute ago, yif said: Hi, I am having difficulty understanding amplifier power ratings, especially if impedance is brought into the picture. For e.g. I note that the Cyrus i9 XR is rated 91w into 6ohm, while the Hegel H190 is rated 150w into 8ohm. What would the maths be here to equalise the two measures please? Thanks! Aah OK - unfortunately Cyrus. for some reason (marketing??) has decided not to use "power into 8 ohms" - which is the standard. The Hegel is 150w into 8 ohms. The Cyrus i9 XR is 91w into 6 ohms. The maths says that this will probably be 91 x (6/8) = 68w into 8 ohms. So it looks like the Hegel is quite a bit more powerful than the Cyrus. However which one will drive your spkrs better ... is not just a matter of the power rating into 8 ohms. The lowest impedance of your spkrs comes into play. If your spkrs drop to, say, 4 ohms and the Cyrus can deliver 136w (91 x 6/4) into 4 ohms ... then this shows it has a good PS - so will drive 4 ohm spkrs well. So whether the H190 is better for your 4 ohm spkrs depends on what it's rated as, into 4 ohms: 300w into 4 ohms means it is excellent 280w is good but, say, 225w is not. Link to comment Share on other sites More sharing options...
NewbieAudiophileEnthusiast Posted September 5 Share Posted September 5 (edited) Well it has to do with how the resistance (ohms) of a speaker affects the amount of current that is able to pass through the speaker. The higher the voltage the less the resistance can inhibit the current. That's why setting an amp to 6 ohm mode from 8 ohm mode drops the voltage down by a few volts... so that less current (amps) can pass through the speaker and it uses less power, since wattage = potential difference (volts) x current (amps) Edited September 5 by NewbieAudiophileEnthusiast Link to comment Share on other sites More sharing options...
Phil K Posted September 5 Share Posted September 5 Also to consider is how the amp is measured. Peak watts, continuous into 1 channel or two. 20hz - 20khz or 1khz ? We likely all know of inexpensive avr's rated at 170w p/c that sound weedy next to a Nad 3020 ( rated 20 wpc ) or a 30w valve amp. An amp that is rated say 70% or more into 4 ohm vs it's 8 ohm rating, will be relatively higher current and cope with harder speaker loads better. This is why an amp conservatively rated can sound clean and powerful Link to comment Share on other sites More sharing options...
yif Posted September 5 Author Share Posted September 5 Feels like what everyone is saying just makes things more confusing 1 Link to comment Share on other sites More sharing options...
Phil K Posted September 6 Share Posted September 6 Take measurements with a grain of salt. A demo with your gear or similar will quickly demonstrate enough power, or a lack of, with any given Amp Link to comment Share on other sites More sharing options...
yif Posted September 6 Author Share Posted September 6 7 minutes ago, Phil K said: Take measurements with a grain of salt. A demo with your gear or similar will quickly demonstrate enough power, or a lack of, with any given Amp Therein lies the problem. It’s not like I can cart my speakers in store to audition! Link to comment Share on other sites More sharing options...
aussievintage Posted September 6 Share Posted September 6 (edited) What has not mentioned yet, is how this relates to how loud your system will sound. To figure that out, you need to look at a different specification - the speaker efficiency, usually stated in decibels for 1 watt at 1 metre. Even with only one set of speakers, you need to take this into consideration in any discussion of how powerful (in watts) your amplifier needs to be. Edited September 6 by aussievintage Link to comment Share on other sites More sharing options...
andyr Posted September 6 Share Posted September 6 2 minutes ago, yif said: Therein lies the problem. It’s not like I can cart my speakers in store to audition! Then see if retailers will let you audition a power amp at home, with your spkrs. As you are in Melbourne, perhaps I could bring over 2 different (stereo) power amps to try with your spkrs: one is 40w into 4 ohms, Class A - and stable into 2 ohms the other is 75w into 8 ohms and ~130w into 4 ohms Class AB and stable into 2 ohms. I'm not interested in selling either of them (as they are my 'summer' and 'winter' amps - the Class A gets too hot to use in summer! ) but they might give you an idea of what you need in an amp, to drive your spkrs well. PM me if you're interested. 1 Link to comment Share on other sites More sharing options...
Phil K Posted September 6 Share Posted September 6 11 minutes ago, yif said: Therein lies the problem. It’s not like I can cart my speakers in store to audition! Why not? Unless they're massive/heavy. It's a hassle granted, but I've taken small floorstanders to dealers to dem an amp, and I've also taken my own amp to hear speakers I subsequently bought. In both cases I purchased said equipment with a much clearer understanding than if I hadn't demoed. There also may be an option to borrow from the dealer or purchase with refund if not happy with the sound. Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted September 6 Volunteer Share Posted September 6 Comprehensive set of measurements here: https://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=2822:cyrus-audio-i9-xr-integrated-amplifier-dac-measurements&Itemid=154 1 Link to comment Share on other sites More sharing options...
andyr Posted September 6 Share Posted September 6 ^ ^ ^ Well found, Trev! 1 1 Link to comment Share on other sites More sharing options...
davewantsmoore Posted September 6 Share Posted September 6 (edited) 15 hours ago, yif said: What would the maths be here to equalise the two measures please? It is the wrong question, because the answer will not help you figure out which amplifier suits which speaker. .... and even if you did - it is hard to answer - because comparing them ends up in a "it depends on the specifics of the amplifier" situation. Questions to ask instead. What is my speaker impedance? (this is ideally a range, eg. minimum and maximum... rather than a single number) How much power do I need? (to get the SPL that I want) Does the amplifier deliver more power than I need, at my speaker impedance (or at a higher impedance)? Do not think that "more power is better". ie. if you were to take an amplifier which has X watts for Y impedance... and an amplifier with A watts for B impedance ... and compare them by "correcting" the values to their equivalents (as you were asking in your initial post) ...... then simply choosing the more powerful (corrected) one is a mistake. Also do not think that "too much power is bad". If your speaker can handle 200w, then it is ok to use an amplifier which can deliver 300w. Choose any amplifier which delivers more power than you need (into your speaker impedance/s) .... and reject any amplifier which doesn't. 6 hours ago, yif said: Feels like what everyone is saying just makes things more confusing Understandable. The above questions are the ones you need to ask... and seek help on, if you are struggling to figure out the answers. Edited September 6 by davewantsmoore Link to comment Share on other sites More sharing options...
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