Back with another newbie question! Having recently converted to a valve amp Im looking to improve on my speakers (MS Mezzo 2's). It's not that Im particularly unhappy with them but I like to try to keep a level of symmetry in my system and as i've also upgraded my CDP (Merdian G07). I cant help thinking the speakers might be a 'weak' link. Having a amp with 17 or 40W I've come to understanding the sensitivity of speakers and understand Im looking for a high sensitivity but what im struggling to understand is Ohms. I can find plenty on the net but none of it explains simply enough (for me anyway!) the difference say between 4 and 8 and what is best to go for with my kind of amp. Im planing on listening to a few anf high on my list are the Dali ikon 6 and PMC TB1i two very different speakers I know and rather than show my lack of knowledge at my dealers I thought I would come on here and share it with the world Any 'laymen' explanations would be gratefully receveid Thanks windy
Ohms?
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OK, in very very broad terms...
The principle purpose of the Ohm rating of a speaker is to try and describe the load (or impedence) presented to an amplifier. The lower an Ohm rating, the more resistive the load of the speaker is and the more current it will (try) to draw from the amp.
In practice, speakers never present an consistent load and will vary from a low figure to a high figure depending on a number of factors such as the sound frequency the speaker is being asked to reproduce. So the figure quoted tends to be an averaged figure (which is often described as the 'nominal' figure) while some manufacturers describe the lowest point of the impedence (such as B&W).
If your valve amp will produce 40 watts per channel I would suggest that this figure is the one you should take most notice of rather than the sensetivity - unless you are intending to play at very high volume levels.
The principle purpose of the Ohm rating of a speaker is to try and describe the load (or impedence) presented to an amplifier. The lower an Ohm rating, the more resistive the load of the speaker is and the more current it will (try) to draw from the amp.
In practice, speakers never present an consistent load and will vary from a low figure to a high figure depending on a number of factors such as the sound frequency the speaker is being asked to reproduce. So the figure quoted tends to be an averaged figure (which is often described as the 'nominal' figure) while some manufacturers describe the lowest point of the impedence (such as B&W).
If your valve amp will produce 40 watts per channel I would suggest that this figure is the one you should take most notice of rather than the sensetivity - unless you are intending to play at very high volume levels.
hi im no expert but basicaly 4 ohm speakers are harder to drive than 6 or 8 ohm speakers, most modern speakers are now 8 ohm, but also you have to consider sensitivity some are aroun 86db again affecting amp power, for example a speaker rated 8 ohm and 90 db sensitivity will be easy to drive and would require a lower power amp.
so if you have an 8 ohm speaker with 90 db sensitivity it will run well with a lower power amp.
another thing to consider is amp power ratings, some are not what they seem a sony amp may state 100w but i promise you it will not have the power of a nad 100w amp...... power sells general rule is rms. not pmpo. rms is true power rating and if in doubt check what hi-fi they will give you the the tru power rating. choose your speakers to match your amp, you should be fine ask a dealer or audition them.
to give you an example i have a nad c355 amp rated 80w per channel but im sure other will agree the nad will drive almost any speaker
hope this helps and read bod fish he know what he is on about
ROB
so if you have an 8 ohm speaker with 90 db sensitivity it will run well with a lower power amp.
another thing to consider is amp power ratings, some are not what they seem a sony amp may state 100w but i promise you it will not have the power of a nad 100w amp...... power sells general rule is rms. not pmpo. rms is true power rating and if in doubt check what hi-fi they will give you the the tru power rating. choose your speakers to match your amp, you should be fine ask a dealer or audition them.
to give you an example i have a nad c355 amp rated 80w per channel but im sure other will agree the nad will drive almost any speaker
hope this helps and read bod fish he know what he is on about
ROB
robg1976:hi im no expert but basicaly 4 ohm speakers are harder to drive than 6 or 8 ohm speakers, most modern speakers are now 8 ohm, but also you have to consider sensitivity some are aroun 86db again affecting amp power, for example a speaker rated 8 ohm and 90 db sensitivity will be easy to drive and would require a lower power amp.
so if you have an 8 ohm speaker with 90 db sensitivity it will run well with a lower power amp.
another thing to consider is amp power ratings, some are not what they seem a sony amp may state 100w but i promise you it will not have the power of a nad 100w amp...... power sells general rule is rms. not pmpo. rms is true power rating and if in doubt check what hi-fi they will give you the the tru power rating. choose your speakers to match your amp, you should be fine ask a dealer or audition them.
to give you an example i have a nad c355 amp rated 80w per channel but im sure other will agree the nad will drive almost any speaker
hope this helps and read bod fish he know what he is on about
ROB
as already said above, impedance is measured on a curve against frequency, with the average being quoted as a nominal value. A speaker that is nominally 8ohms might dip to under 4ohms for a certain frequency band. If it does, when the music demands such frequency reproduction, the amp has to suddenly deliver a large amount of current, usually pretty quickly (low resistance value means that more current will flow, high resistance value and less will flow). Depending on how well the amp is designed and spec'ed, it may or may not be able to cope with this demand. If it struggles then the sound suffers as the amp's grip and control over the drive unit weakens resulting in distortion. You can find amps of the same Watt rating but one may be able to deliver far more peak current. Such amps are often referred to as having stiff power supplies.
Sensitivity is a different matter and really represents how many volts a speaker is going to need to go loud (forgive the naff description there). My Spendors are very low in sensitivity but have an easy load (impedance curve), so whilst I need plenty of volts to get volume, they don't need unusually large amounts of current to sound controlled and balanced.
So, now that I've confused things even more, rely on your ears to determine what sounds ok.
so if you have an 8 ohm speaker with 90 db sensitivity it will run well with a lower power amp.
another thing to consider is amp power ratings, some are not what they seem a sony amp may state 100w but i promise you it will not have the power of a nad 100w amp...... power sells general rule is rms. not pmpo. rms is true power rating and if in doubt check what hi-fi they will give you the the tru power rating. choose your speakers to match your amp, you should be fine ask a dealer or audition them.
to give you an example i have a nad c355 amp rated 80w per channel but im sure other will agree the nad will drive almost any speaker
hope this helps and read bod fish he know what he is on about
ROB
as already said above, impedance is measured on a curve against frequency, with the average being quoted as a nominal value. A speaker that is nominally 8ohms might dip to under 4ohms for a certain frequency band. If it does, when the music demands such frequency reproduction, the amp has to suddenly deliver a large amount of current, usually pretty quickly (low resistance value means that more current will flow, high resistance value and less will flow). Depending on how well the amp is designed and spec'ed, it may or may not be able to cope with this demand. If it struggles then the sound suffers as the amp's grip and control over the drive unit weakens resulting in distortion. You can find amps of the same Watt rating but one may be able to deliver far more peak current. Such amps are often referred to as having stiff power supplies.
Sensitivity is a different matter and really represents how many volts a speaker is going to need to go loud (forgive the naff description there). My Spendors are very low in sensitivity but have an easy load (impedance curve), so whilst I need plenty of volts to get volume, they don't need unusually large amounts of current to sound controlled and balanced.
So, now that I've confused things even more, rely on your ears to determine what sounds ok.
Frank Harvey
Well-known member
- Jun 27, 2008
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This how I'd basically put it:
4ohm speakers need more current and grip than 8 ohms ones.
Many speakers, even if they say they're 8ohms, dip to 5, maybe 4 (or sometimes less) when asked to reproduce lower frequencies. As mentioned, impedance isn't a constant thing, it varies with frequency.
4ohm speakers need more current and grip than 8 ohms ones.
Many speakers, even if they say they're 8ohms, dip to 5, maybe 4 (or sometimes less) when asked to reproduce lower frequencies. As mentioned, impedance isn't a constant thing, it varies with frequency.
totaly agree with igglebert its not as straight forward as it should be, im my opinion get a good amp the best you can for your budget and you should be fine. and if you can audition them with a set of speakers ofr your choice you should be o.k then. you havent mentioned your budget if you go for the tryed and proven NAD, cambridge audio, Marantz or arcam if your budget can allow you should be fine they make all make quality gear and have years of experience, it then comes down to personal choice on the sound.
Bodfish:
OK, in very very broad terms...
The lower an Ohm rating, the more resistive the load of the speaker is
WRONG. The HIGHER the Ohm rating is, the more resistive the speaker is.
Bodfish:and the more current it will (try) to draw from the amp.
CORRECT. Ohm's Law V=IR states for a given voltage V applied across a resistance, or impedance, R, a current I will be drawn. If V is increased, and R is constant, then the current will increase proportionally. The fly in the ointment is that R is not constant for a speaker, varying according to frequency.
Your amp will only be capable of delivering so much current, so the sound will not reach full volume if R is or drops too low. Hence power amps usually have huge capacitors capable of delivering huge current "punches". A valve amp current delivery is limited by the current that the valves will pass without burning out.
Bodfish:In practice, speakers never present an consistent load and will vary from a low figure to a high figure depending on a number of factors such as the sound frequency the speaker is being asked to reproduce. So the figure quoted tends to be an averaged figure (which is often described as the 'nominal' figure) while some manufacturers describe the lowest point of the impedence (such as B&W).
Correct.
Now for your speakers:
Mordaunt-Short speakers are not known for their sensitivity (my last pair were Mezzo 6's), and I would go for something with a higher sensitivity around 90 dB. Incidentally, a rise in sensitivity of 3 dB, from 87 dB to 90 dB actually represents a near-doubling of sensitivity, as the decibel scale is logarithmic not linear.
If you've invested in a valve (like trading your car for a horse and cart IMHO, but your choice) amp I would suggest changing your speakers, and then your ears and taste take over.
OK, in very very broad terms...
The lower an Ohm rating, the more resistive the load of the speaker is
WRONG. The HIGHER the Ohm rating is, the more resistive the speaker is.
Bodfish:and the more current it will (try) to draw from the amp.
CORRECT. Ohm's Law V=IR states for a given voltage V applied across a resistance, or impedance, R, a current I will be drawn. If V is increased, and R is constant, then the current will increase proportionally. The fly in the ointment is that R is not constant for a speaker, varying according to frequency.
Your amp will only be capable of delivering so much current, so the sound will not reach full volume if R is or drops too low. Hence power amps usually have huge capacitors capable of delivering huge current "punches". A valve amp current delivery is limited by the current that the valves will pass without burning out.
Bodfish:In practice, speakers never present an consistent load and will vary from a low figure to a high figure depending on a number of factors such as the sound frequency the speaker is being asked to reproduce. So the figure quoted tends to be an averaged figure (which is often described as the 'nominal' figure) while some manufacturers describe the lowest point of the impedence (such as B&W).
Correct.
Now for your speakers:
Mordaunt-Short speakers are not known for their sensitivity (my last pair were Mezzo 6's), and I would go for something with a higher sensitivity around 90 dB. Incidentally, a rise in sensitivity of 3 dB, from 87 dB to 90 dB actually represents a near-doubling of sensitivity, as the decibel scale is logarithmic not linear.
If you've invested in a valve (like trading your car for a horse and cart IMHO, but your choice) amp I would suggest changing your speakers, and then your ears and taste take over.
Good explanation darren, if thats the case then do you think my amp ( 36 watts ) is a good match for the speakers ?
Thanks, john.
Thanks, john.
Correct me if i'm wrong hear. The Bijou power amp is a valve amp and like most single ended valve amp's they require sensitive speakers to be heard at there best. The reason for this is the small amount of current going to the speakers from the amp. The more sensitive the speaker the more current can pass through. The Spendor's sensitivity is 86db which is quite tough for a single ended to drive. Speakers with a sensitivity reading of 90bd or more would gain better results. Sugden produce there own speaker's, these could be a better match that the Spendor's even though they are very nice.
shooter69:Correct me if i'm wrong hear. The Bijou power amp is a valve amp and like most single ended valve amp's they require sensitive speakers to be heard at there best. The reason for this is the small amount of current going to the speakers from the amp. The more sensitive the speaker the more current can pass through. The Spendor's sensitivity is 86db which is quite tough for a single ended to drive. Speakers with a sensitivity reading of 90bd or more would gain better results. Sugden produce there own speaker's, these could be a better match that the Spendor's even though they are very nice. Shooter, the bijou pre-amp is class A and the power amp is class A/B. Don,t think sugden make valve amps.
johnnyjazz:shooter69:Correct me if i'm wrong hear. The Bijou power amp is a valve amp and like most single ended valve amp's they require sensitive speakers to be heard at there best. The reason for this is the small amount of current going to the speakers from the amp. The more sensitive the speaker the more current can pass through. The Spendor's sensitivity is 86db which is quite tough for a single ended to drive. Speakers with a sensitivity reading of 90bd or more would gain better results. Sugden produce there own speaker's, these could be a better match that the Spendor's even though they are very nice. Shooter, the bijou pre-amp is class A and the power amp is class A/B. Don,t think sugden make valve amps.
Cool.
I wasn't sure on the Bijou.
Cool.
I wasn't sure on the Bijou.
johnnyjazz:
Good explanation darren, if thats the case then do you think my amp ( 36 watts ) is a good match for the speakers ?
Thanks, john.
In reality most people don't tend to play loud enough to need masses of Watts. You'll find that dynamic peaks of music at higher volumes will result in some clipping. You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character. Of far more importance to the output is the current loading of the speakers and the amp's ability to fulfill it. Spendor's current speakers are a pretty easy drive, as you might expect from a well designed pair of speakers.
Good explanation darren, if thats the case then do you think my amp ( 36 watts ) is a good match for the speakers ?
Thanks, john.
In reality most people don't tend to play loud enough to need masses of Watts. You'll find that dynamic peaks of music at higher volumes will result in some clipping. You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character. Of far more importance to the output is the current loading of the speakers and the amp's ability to fulfill it. Spendor's current speakers are a pretty easy drive, as you might expect from a well designed pair of speakers.
igglebert:You find that dynamic peaks of music at higher volumes will result in some clipping. You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character.
I'm sure sure how clipping is a good thing!
If your speakers are clipping it's because the amp doesn't have enough power to drive them. John the speakers you have at the moment are very nice as i've put before. Sensitivity ratings of speakers range from around 85db to 115db so as you can see the Spendor's are at the bottom of the scale. If you were to use more sensitive speaker you would get more volume from using the same amount of current. Your Spendor's are rated at 86db if you were to use the Sugden's they are rated at 90db. There is a 4db difference here. You would use less current/volume driving the Sugden's as if you were to drive the Spendor's to the same volumes thus giving greater volumes overall to the Sugden's. I've noticed your speakers have a power handling of 200 watts but what i cant find is the minimum amount of power required to drive them. Maybe there is no minimum and a low output amp like the Bijou with 18 watts/8ohms would work fine but using a more sensitive speaker would give you greater volume.
I'm sure sure how clipping is a good thing!
If your speakers are clipping it's because the amp doesn't have enough power to drive them. John the speakers you have at the moment are very nice as i've put before. Sensitivity ratings of speakers range from around 85db to 115db so as you can see the Spendor's are at the bottom of the scale. If you were to use more sensitive speaker you would get more volume from using the same amount of current. Your Spendor's are rated at 86db if you were to use the Sugden's they are rated at 90db. There is a 4db difference here. You would use less current/volume driving the Sugden's as if you were to drive the Spendor's to the same volumes thus giving greater volumes overall to the Sugden's. I've noticed your speakers have a power handling of 200 watts but what i cant find is the minimum amount of power required to drive them. Maybe there is no minimum and a low output amp like the Bijou with 18 watts/8ohms would work fine but using a more sensitive speaker would give you greater volume.
igglebert:You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character.
Yup, I go for that sound of tweeter voice coils about to fuse together every time...
Yup, I go for that sound of tweeter voice coils about to fuse together every time...
Andrew Everard:
igglebert:You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character.
Yup, I go for that sound of tweeter voice coils about to fuse together every time...
Maybe I misuse the term clipping here. Wasn't it the basis of the large power Musical Fidelity amps that without such high power, dynamic peaks of music are generally clipped or limited? Such limitation adds colour to the sound.
igglebert:You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character.
Yup, I go for that sound of tweeter voice coils about to fuse together every time...
Maybe I misuse the term clipping here. Wasn't it the basis of the large power Musical Fidelity amps that without such high power, dynamic peaks of music are generally clipped or limited? Such limitation adds colour to the sound.
I think we're confusing two forms of "clipping" here. Correct me if I'm wrong, but "clipping" in the hifi sense occurs when the either the voltage generated by the amp causes too much current to be drawn, or when the impedance of the coil drops too low, again drawing too much current. Both cause the speaker coils to "bind up", a bit like compressing a coil spring so that the coils begin to touch each other. Like the suspension "bottoming out" in your car, the audio jolt can be very nasty and very harmful. Basically, a speaker coil that binds shorts out. Nasty.
On the other hand, a power amp that can't provide sufficient current in response to a sudden demand, disappoints because the sudden "oomph" isn't there. Now, I'm a mechanical engineer (well, at least that's what my degree certificate says), but if I remember correctly, the maximum power is transferred when the impedance of the source matches the impedance of the load. Don't know if that helps much, mind.
In response to the OP's question, I cannot answer. The last valve amp I ever heard was the 1960s home-made (yes home made) one my dad tossed in the shiny round metal thing outside the back door (remember them?) when he came home with a wizz-bang transistorised Goodmans Module 90 from Comet in about 1975. All I can say is let your ears be your guide and listen to the more knowledgable contributers round here.
On the other hand, a power amp that can't provide sufficient current in response to a sudden demand, disappoints because the sudden "oomph" isn't there. Now, I'm a mechanical engineer (well, at least that's what my degree certificate says), but if I remember correctly, the maximum power is transferred when the impedance of the source matches the impedance of the load. Don't know if that helps much, mind.
In response to the OP's question, I cannot answer. The last valve amp I ever heard was the 1960s home-made (yes home made) one my dad tossed in the shiny round metal thing outside the back door (remember them?) when he came home with a wizz-bang transistorised Goodmans Module 90 from Comet in about 1975. All I can say is let your ears be your guide and listen to the more knowledgable contributers round here.
shooter69:igglebert:You find that dynamic peaks of music at higher volumes will result in some clipping. You may actually like the sound that this produces as it will go some way towards giving your amp and speaker combo character. I'm sure sure how clipping is a good thing! If your speakers are clipping it's because the amp doesn't have enough power to drive them. John the speakers you have at the moment are very nice as i've put before. Sensitivity ratings of speakers range from around 85db to 115db so as you can see the Spendor's are at the bottom of the scale. If you were to use more sensitive speaker you would get more volume from using the same amount of current. Your Spendor's are rated at 86db if you were to use the Sugden's they are rated at 90db. There is a 4db difference here. You would use less current/volume driving the Sugden's as if you were to drive the Spendor's to the same volumes thus giving greater volumes overall to the Sugden's. I've noticed your speakers have a power handling of 200 watts but what i cant find is the minimum amount of power required to drive them. Maybe there is no minimum and a low output amp like the Bijou with 18 watts/8ohms would work fine but using a more sensitive speaker would give you greater volume. Sorry shooter, i think it,s 36 watts ? I,ve also had comparisons with other well known branded amps of supposedly more power, but they have not sounded nearly as lively as the little sugden.
johnnyjazz:Sorry shooter, i think it,s 36 watts ?
Sorry, i was referring to on-line info showing the Bijou power amp rated at 8 Ohm 16 Watts/4 Ohm 23 Watts and 2 Ohm 22 Watts respectively.The 18 i quoted was also wrong.
johnnyjazz:I,ve also had comparisons with other well known branded amps of supposedly more power, but they have not sounded nearly as lively as the little sugden.
I'm sure the Sugden perform's amicably and surpasses other brands with ease they are very nice Class A machines. I wasn't trying to belittle the Sugden in anyway shape or form just trying to answer your OP. : )
Sorry, i was referring to on-line info showing the Bijou power amp rated at 8 Ohm 16 Watts/4 Ohm 23 Watts and 2 Ohm 22 Watts respectively.The 18 i quoted was also wrong.
johnnyjazz:I,ve also had comparisons with other well known branded amps of supposedly more power, but they have not sounded nearly as lively as the little sugden.
I'm sure the Sugden perform's amicably and surpasses other brands with ease they are very nice Class A machines. I wasn't trying to belittle the Sugden in anyway shape or form just trying to answer your OP. : )
Thanks for the input everyone. Im a lot clearer now on the Ohm's issue.
Cant wait to hear some different speakers now!
cheers
Cant wait to hear some different speakers now!
cheers
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