Loudspeaker Impedance 4-Ohm vs 8-Ohm: Which is Better?

okay I think we're live it is Saturday 11:15 p.m. and forgive me guys I have not used OBS Studios in in quite some time I've been using stream yards but since this is a solo stream I wanted to give you guys better quality so I would like to talk about speaker impedance I've seen several questions come up on the forums about what's the difference between an 8 ohm speaker and a 4 ohm speaker so I wanted to kind of do a very basic video here we could do something that's more in detail at a later date I'm gonna keep this pretty short and concise I hope everybody could see me okay so what I'd like to do is do some screen sharing with you on speaker stuff so I think there's a misconception sometimes when people think an 8 ohm speaker is better than a 4 ohm speaker or a forum speakers better than an 8 ohm speaker it's really it depends on the design it depends on the engineers goal when they made the speaker it depends how it's gonna be used and I wanted to kind of drop some knowledge on you guys about that so I'm hoping right now that you're seeing my screen share because I don't really have a way to monitor this but anyways we have an article called loudspeaker sensitivity and impedance explained I will link it up in this video I do recommend you read it it's important and one thing that really kind of stands out about this article is about the impedance of a speaker and how you can't just go by a single number when you look at a manufacturers website and they say a speaker is 8 ohms or a speaker is 4 ohms without actually seeing an impedance graph it's a pretty useless speaker spec because you don't know how they're measuring the impedance you don't know what frequency that rating is from because the only time a speaker is is a constant load at one particular rating is at DC basically and you don't listen to a speaker at DC you listen to a speaker from 20 Hertz to 20 kilohertz and over that range the impedance fluctuates it goes up and down the pin whether it's inductive or capacitive or how the drivers interact with the crossover so it's interesting to note that there are speakers that are 8 ohm rated and forum rated and the sensitivity also changes on that as well so if you look at if you keep things everything constant except for the impedance of the speaker and for argument's sake you have two identical speakers 1 speakers 8 ohms rated the other speakers forums rated with any given voltage if you keep voltage fixed they'll say a 2.8 3 volts if that 8 ohm speaker is rated at 87 dB at 2.8 3 volts then that equivalent speaker in a 4 ohm version would be rated at 90 DB so you gain 3 DB of sensitivity with or 3 DB of loudness what all other things being equal so that's kind of an important thing to note and people ask well why are some speakers 8 ohms and some speakers for arms and sometimes that has a lot to do with the driver specs that they're using the system if you take a speaker that has for example 3 8 inch woofers in the cabinet and each woofer is rated at 12 ohms well if they put all three of those woofers in parallel with each other then the equivalent impedance of those 3 woofers in parallel would be 4 ohms it's basically the reciprocal sum of the resistances of the reciprocated resistances so 1 over 12 plus 1 over 12 plus 1 over 12 you sum that up and you take the inverse of that and you get 4 ohms well that's fine like in a consumer speaker with 3 8 inch drivers but when you're dealing with commercial or you're dealing with large powered systems that have woofers with larger voice coils like a 3/4 inch voice coil and and the speaker is designed to handle a lot more power the wire that goes around the voice coil tends to be lower gauge and as a result these woofer impedance tends to be lower in resistance so you might use in that case 3 6 ohm woofers and when you put 3 6 ohm woofers in parallel you get a 2 ohm equivalent so you can start seeing how a speaker impedance can go really low and we'll talk about what the hell that could affect the amplifier now there are there are tricks around that manufacturers can do they can put speakers they could put woofers in series as opposed to parallel but then again you're reducing sensitivity because if you put two Eitan woofers in see in series that's an equivalent resistance of 16 ohms as opposed to two 8 ohm offers in parallel which is 4 ohms so of course if you go across 2.8 3 volts and you do that it's it's V squared over R so you do 2.83 and you divide that by 4 that gives you 2 watts but a 2.8 3 and you divide by 16 and that gives you half a lot so that's a difference of fourfold in terms of how much power that they an amplifier is dissipating just by how they're wiring the woofer is whether they're doing them in series of parallel so you can see the lower impedance speaker has a sensitivity advantage and that's why you get some of the pro speakers or some of the large scale speakers that have a lot of output capability tend to be lower impedance so I wanted to show you what an impedance graph would look like on a speaker because most manufacturers don't give you this most manufacturers will literally give you just one singular rating so you look at this speaker from infinity this is like a $400 Tower it's an infinity primus p 363 I think this I think this model might be discontinued now but it was actually pretty well rated people liked this speaker it's a good speaker for what it is for a 400 all a tower and they rated this at 8 ohms and if you look this is 8 ohms right here 8 is the line here so this is the impedance and this is the face I don't want to talk too much about phase but in general if you have too much of a sharp phase angle at a very short distance in frequency that could cause amplifier problems but I don't want to get too far into that I want to keep this pretty general let's just focus on the impedance you can see here you have a saddle point because this what this system is tuned and this is about where the tuning frequency is which looks like it's about 45 Hertz so in order to meet an 8 ohm spec if you go by IEC standard which is a standard measurement method for measuring loudspeaker impedance and sensitivity they want you they want to see whatever this the loudspeaker company rates the speaker let's say they rated it 8 ohms they want to see that impedance being no less than 80% that rating from 300 Hertz to 3 kilohertz so in this case an 8 ohm speaker should have no dips lower than about 6.4 ohms you can see in this case that's the infinity is really not it's it's it dips down to about five and a half ohms that it's tuned of frequency then over here and around 100 to 200 Hertz it goes well below 4 ohms here so they they could have optimized this cross over a little bit better but this is the interesting thing at 10 kilohertz this is something that you that's unexpected to see the impedance of the speaker dip down to 4 ohms for an 8 ohm system when everything else is pretty close to 8 ohms up here if you take the kind of magnitude of this what this what's happening here is Harman was being very clever they try to use the cheapest tweeter possible in this case because of budget and what they try to do is they try to increase the system sensitivity by going to a 4 ohm tweeter in an 8 ohm system and the reason why they did that is if they were to use an 8 ohm tweeter and wanted to get the kind of output and sensitivity from an 8 ohm they would have had to use a tweeter that had a larger motor structure and maybe even a bigger waveguide on it and those kind of things cost more money so they went with a 4 ohm tweeter and they stuck it into an 8 ohm speaker I don't agree with this kind of design philosophy I think they probably should have spent a couple more bucks and put a motor structure that was a little bigger and a better tweeter but overall the speaker is a good speaker and to their defense there's not a whole lot of program material you know above 10 kilohertz so you don't dissipate a lot of power so most amplifiers can handle a forum load like this there's only very few exceptions some of the earlier class D amplifiers like the older ice modules they did not like a low impedance above about 5 kilohertz so this speaker on an older pioneer ice amplifier could potentially be a problem when driven at full power they could potentially shut the receiver off and that's an important thing to know - is the receivers today have a lot of short-circuit protection a lot of nanny control over thermal protection you're probably not going to blow out a receiver driving it with a forum load if it's not fully capable of driving that forum load but you might shut it off and you might be at a party you might be cranking it up and all this on the receiver shuts off and this is a potential reason why because here's the deal when you're looking at most AV receivers on the market at 1 watt at 2.8 3 volts an amplifier will operate like an ideal voltage source so if you supply 2.8 3 volts to an 8 ohm speaker you'll get 1 watt if you supply to 23 volts to a 4 ohm speaker you'll get 2 watts you've doubled your power and that happens on amplifiers in ideal circumstances it happens at 1 watt and virtually every amplifier I've ever seen but when you get to the amplifiers limits whether it's the power supply limits or it's the thermal limits of the actual amplifier module itself it starts becoming thermally limited or power limited so if that receiver is rated at 150 watts at 8 ohms most receivers will not give you 300 watts at 4 ohms that might give you 250 watts at forums and then when you start driving a couple of channels you start getting into the area where it starts going into its nanny control because it just can't dissipate that much heat and that's what you got to be careful about with lower impedance speakers so I wanted to show you a couple more examples here we had we recently reviewed the SVS pinnacle prime speaker and I'm going to show you their manufacturers page right here so this is a tower that has three I think these are six and a half inch woofers and five and a quarter inch mid and a tweeter so you got three bass drivers in parallel you got the mid-range that's probably in parallel but it's got a high-pass on it so at low frequencies it doesn't the equivalent impedance of this speaker is not going to have four woofers in parallel because they put a capacitor there too that problem and that is a problem with some tower speakers I've seen I've seen some pretty sloppy designs that have no high-pass on the mid-range driver so at DC it's essentially for drivers in parallel and that P dance of that speaker dips down to like 2 ohms some receivers will have a problem at near DC at a couple of Hertz especially if you're hitting bass and they're not they don't have a high pass on this receiver if you're not bass managing that could cause receivers are shut off as well so at the very low end of the spectrum that could be a problem too that's why when a speaker manufacturer gives you impedance back I'd like to personally see a graph but if they don't give you a graph I'd like to see a nominal rating I'd like to see a DCR rating of the system and I'd like to see a minimum rating usually the minimum rating tends to be the DCR of the system but you rarely see that SPECT in the manufacturers website so SPS here they tell you the nominal impedance is 8 ohms and that's in my opinion a useless rating I'm sorry SPS I'm not bashing you but most companies do this but what is interesting is they actually give you a real sensitivity spec so they rated IEC from 300 Hertz to 3 kilohertz and we went and we measured this speaker and I want to show you the measurements here this is a very interesting phenomenon here so if you look at this impedance graph this is the impedance that's the phase if you look at the impedance graph here this is really not an 8 ohm system you could see it dips below 5 ohms I would really consider this a 6 ohm because if you do point eight of 6 it goes down to about four point eight homes so I would really consider this a 6 ohm maybe even a 4 ohm speaker but I would tell it I would tell you it's a 6 ohm speaker it's really not an 8 ohm speaker but the interesting thing is they rated at 88 DB sensitivity at 2.83 volts we measured 90 DB sensitivity so that almost compensates they were like overly conservative with the sensitivity rating but they were not conservative at all with the impedance rating I'm if I knew SVS well and I know the guys there I would almost think that the engine hearing people wanted to rate the speaker a 6 ohm speaker but the marketing people wanted to call it an 8 ohm speaker so the engineering said ok well let you rate it as an 8 ohm system but we're gonna dere 8 the sensitivity rating and I think that's why they came out with the 88 D because if you work out the math and you switch from 6 ohms from 8 ohms to 6 ohms you get your 90 DB which is what we measured so this is a pretty benign load to drive it's not a hard speaker to drive in most cases if you're driving a tower like this with multiple woofers and the sensitivity is 90 DB or so you'll probably be ok with a normal mid-price receiver but I would caution you if you're running a receiver that has 9 or 11 amplifiers built in I would use a separate power amp in this case for a big Tower like this especially if you're not based managing it so I want to show you a bookshelf speaker from Revell and I believe they rated this as a 6 ohm speaker and you can see here it is about a 6 ohm it's a it's it's a little shy of it so 6 ohm shouldn't dip below I'm sorry it shouldn't dip below 4.8 ohm so this is actually closer to an 8 ohm speaker this is a conservatively rated speaker you can see the saddle points here are above 6 ohms the whole system itself especially at high frequency is very high impedance like 12 ohms so I would really call this an 8 ohm speaker this is a real easy load to drive it's got decent sensitivity at 86 DB for a bookshelf that's pretty good or actually if they measured it at 88 DB even though Revell spected at 86 so that's you know this is pretty much the pinnacle of engineering and a bookshelf speaker is here and it's a high-end speaker and there was no reason to make this a forum speaker I mean it just that's how it worked out with the woofer itself didn't need to be a super low in resistance coil and whatever they chose here I don't know if it's a 2 inch or three inch coil this thing handled plenty of power it had a lot of sensitivity and you know it plays loud and plays clean so that's why I just wanted to show you and then here's one more example here's an rbh tower that's rated at 4 ohms and you could see I have a dotted line here the IEC minimum for 8 for 4 ohms is 80% of 4 so it's 3 point 2 ohms that's where this dotted line is an RB H speaker doesn't dip below basically about 3.8 ohms this is a conservatively rated Borum speaker so the only other thing I wanted to talk to you about let me stop sharing my screen here for a minute and I'm back ok so I know there's a temptation despite the fact I've done tons of articles tons of videos on the receiver impedance which people still ask me I have a six ohm speaker from Brand X should I set the impedance switch on my receiver to 8 ohms or should I set it to 4 ohms and I will tell you every single time it's asked always leave your receiver on the high setting on the a dome setting or the 6 ohms and more setting never set that switch to the low setting that switches there for one purpose only that switch is there so it lowers the output voltage when ul or CSA or whoever's doing the thermal tests on that receiver and they want to stamp a 4 ohm rating on that receiver they D rate the power so they make that amplifier clip soon or at lower voltage so that receiver dissipates less power and it meets their thermal requirements so they could say this receiver is capable of handling 4 ohm speakers you're actually gonna cause more clipping and you get a reduce your dynamics more by using the low setting regardless of your speaker impedance always keep the switch on the high setting so I think that's all I wanted to cover about this I hope you guys found this useful the difference between 8 ohm and 4 ohm speakers it doesn't mean that one speaker is better than the other just because of the impedance it's just really about design compromises and design considerations about really about the impedance of the drivers about the woofers about how many woofers are in parallel versus doing series connections inside the speaker and it's about getting as much sensitivity out of that system as you can so I would again say if you're getting forum speakers and you're running them full range in most cases you don't want to use a receiver to power them when that receiver internal amplifier is doing is basically powering all the other speakers in your system unless you're getting like a 60-pound receiver from 10 years ago that had huge power supplies in it multiple output devices per channel and could really handle driving a low impedance loads I would almost tell you to always get a separate amplifier when you're driving a forum a real forum speaker especially if the sensitivity is below like 90 DB and you like a lot of bass and you like to play it loud go with a separate amplifier amplifier power is cheap really not that big of a problem these days and in fact in most cases you can reassign on unused amplifiers and a receiver to say the back channels or another zone and then preamp out to a 2-channel amplifier from model price or outlaw para sound you know there's so many brands out there excuse me so guys I think that sums it up here I hope I answered your questions on the difference between eight ohm and 4 ohm speakers if you like this video please thumb it up please share it YouTube's algorithm change now so if you don't get a lot of shares on videos within 24 hours then that just dies you just the traffic stops on it so hope you guys share this video and if you want us to discuss this topic more I'll have Matthew posed on here again and we'll talk about loudspeaker sensitivity loudspeaker phase we could go real nuts on this we could do an hour broadcast if you want no big sweat I just like to keep things simple right now so don't forget about our patreon channel at patreon.com slash audio holics you can go and submit your questions there if you want us to do dedicated videos on any particular topic we also give you the content sooner there than you often see it on youtube or an audio Hulk's comm and until next time my friends keep listening

Channel: Audioholics

Views: 99,338

Rating: 4.8784142 out of 5

Keywords: audioholics, video review, home theater, audiophile, tech, headphones, speakers, amplifier, movies, music, audio, video, projection, bass, subwoofer, hdtv, blu-ray, dolby, atmos, speaker impedance, amplifier load, hifi

Id: V5ym0o43t4M

Length: 19min 47sec (1187 seconds)

Published: Sat Oct 19 2019