Author Topic: Is LS3/5A 15 ohms speaker better than the 11 ohms LS3/5A speaker?  (Read 26869 times)

Offline james46

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Just wondering if 15 ohm sounds better why don't all the people make 15 ohm as a standard?

ghemml

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Regardless of impedance, the sensitivity is more important.

One reason I can understand for the high impedance is to prevent the amp e.g. class A amp from dying.

Offline Doggie Howser

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actually lower ohm is harder to drive...

I think Audio is approaching it using a different perspective. He's suggesting that if you have a powerful enough amp so the low impedance issue is taken care of, the higher input impedance prevents you from driving the speakers loud. That is a fascinating take on it.

End of Line - Derezzed

Offline joamonte

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Bare in mind that LS3/5a in the beginning is design for monitoring voice in a small enclose area , like inside a Van mobile mixing room or a HDB toilet size monitor room...the BBC engineer never meant to use it listen music, 15 ohm is not a problem because they have a standard transistor amp (make by Quad) to match with it , and the "standard" BBC LS3/5a terminator is using XLR connector for space, safety and easy pluging reason (MIGHT be a reason for higher impedance design)...pls remember it is a just a grade B monitor that "not qualify" as music monitoring,to BBC , it only can be use to check the recording quality of human's speaking for their radio broadcasting.

My guess is some audiophile in the 70's , 80's that using tube amp with the 16ohm output tap accidently discover how good the sound from this speaker, and when more and more home user buy the speaker and drive with solid state amp, BBC/KEF change the design to 11 ohm so that it is more suitable for the budget SS amp...

The official reason BBC change the design to 11 ohm in 1989 is because the 15 ohm design KEF woofer (8 ohm) encounter high rejected rate , so they have to redesign the woofer , the new woofer impedance drop to average 6 ohm, so KEF  have to redesign the crossover , hence the overall impedance of the speaker become 11 ohm.

James , the main attractive point about 15 ohm model is that their crossover are made by different company, despite the values and circuit are the same, but different brand 15 ohm using different component, 11 ohm model all crossover are made by KEF.......and the 11 ohm crossover is not design by BBC famous engineer team , it is design by KEF, while I respect the KEF engineer knowledge, I think you also agree that KEF do not have too much great small speaker in their history ( ok 104/105 is good in old day , but those are floor stander, their own coda small speaker never really made it  :P )
« Last Edit: May 29, 2013, 01:40 by joamonte »

Offline joamonte

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One more thing to add.....

Another reason why earlier 15 ohm LS3/5a have better resale value is because in those days, 70/80s or earlier higher price Hifi are made to last, the maker put in effort in the built quality and workmanship, if you compare the veneer and parts of a good condition 70's Chartwell or Rogers Gold Tag, with the 90's Rogers 11 ohm model, you will realize the later component use is really cheapskate and the cabinet is not as solid, even the veneer don't look as nice....

The reason why 11 ohm Harberth usually can get better biding price is because Harberth have the best workmanship of all 11 ohm batch.

Offline Audio

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I hope by now, most of you should know that how good a speaker or headphone would sound has nothing to do with their impedance.  Don't waste your sleep and worry about such things.   The designers would have done their homework when it comes to this as most power amp nowadays should be able to drive most speaker loads.

My prospective was taken from my experience with the Rogers LS3/5A and I experienced first hand the issues with it.

It also come with dealing with headphone issues at work.  As you are well aware, the airlines introduce electrical headphones for use in the late 80s and a good design would be one with a high impedance because:-

(1) We don't have cost effective, small and powerful magnets as we have today.

(2) The DC supply of aircraft electrical system is 28VDC so, we don't have voltage limitations like what car and other transportation vehicle faces with supply voltage limited to 12VDC.

(3)  A high impedance headphones will consume less current and will be a good safety consideration.

Hence almost all airlines headphones are spec at 300 ohms.  Now imagine what happened when you fit in your everyday 16 Ohms headphones into the system, it will sound very, very loud.   This is the reason why Bose Noise cancellation headphones comes with 2 gain settings.....and the more expensive UE (Logitech) has an special attenuator attachment to be used when the earphones is plug onto the aircraft system.

Another thing is because the low impedance headphones is so efficient, which means it is more sensitive, the residue noise of the aircraft sound system (buzz, hiss, 400Hz aircraft AC supply pickup) will be heard more clearly and loudly then from a pair of high impedance insensitive headphones. 

And because your iPad , ipod, Iphones and other mobile devices have limited supply voltage, that is why your everyday headphones / earphones need to have a low impedance or else it will not sound loud enough.  Some Audiophile headphones are still designed with high impedance because they expect you to use a good headphone amp to drive it.....one with higher supply voltage or one with a switching power supply.

So, what speakers and headphones are easier to drive??  Low Impedance ones and please don't lose sleep over it.  We, after all, are already in the 21st century...... 

(Audio)
 

Offline jerome_the_lang

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I hope by now, most of you should know that how good a speaker or headphone would sound has nothing to do with their impedance.  Don't waste your sleep and worry about such things.   The designers would have done their homework when it comes to this as most power amp nowadays should be able to drive most speaker loads.

My prospective was taken from my experience with the Rogers LS3/5A and I experienced first hand the issues with it.

It also come with dealing with headphone issues at work.  As you are well aware, the airlines introduce electrical headphones for use in the late 80s and a good design would be one with a high impedance because:-

(1) We don't have cost effective, small and powerful magnets as we have today.

(2) The DC supply of aircraft electrical system is 28VDC so, we don't have voltage limitations like what car and other transportation vehicle faces with supply voltage limited to 12VDC.

(3)  A high impedance headphones will consume less current and will be a good safety consideration.

Hence almost all airlines headphones are spec at 300 ohms.  Now imagine what happened when you fit in your everyday 16 Ohms headphones into the system, it will sound very, very loud.   This is the reason why Bose Noise cancellation headphones comes with 2 gain settings.....and the more expensive UE (Logitech) has an special attenuator attachment to be used when the earphones is plug onto the aircraft system.

Another thing is because the low impedance headphones is so efficient, which means it is more sensitive, the residue noise of the aircraft sound system (buzz, hiss, 400Hz aircraft AC supply pickup) will be heard more clearly and loudly then from a pair of high impedance insensitive headphones. 

And because your iPad , ipod, Iphones and other mobile devices have limited supply voltage, that is why your everyday headphones / earphones need to have a low impedance or else it will not sound loud enough.  Some Audiophile headphones are still designed with high impedance because they expect you to use a good headphone amp to drive it.....one with higher supply voltage or one with a switching power supply.

So, what speakers and headphones are easier to drive??  Low Impedance ones and please don't lose sleep over it.  We, after all, are already in the 21st century...... 

(Audio)

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Offline james46

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Thats what I thought that in general impedance have nothing to do with sound quality.

Offline flowerpot

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Low impedance is easier to drive is wrong im afriad... not here to prove anything but is a matter of fact low imepdance as seen by the amp is harder to drive....

A simple fact is low imepdance draws much higher current, the amp have to source more current just to drive the speakers to the same level as a higher imedance load...

Thats why you see power ratings of 50W@8ohm, 100W@4ohm etc... The very reason being the amp is having to pump out more power to drive the lower imepance load....

A simple ohms law even tell you that a higher imedance load will see a higher voltage across it as compare to a lower impedance load...

Also the output impedance of the amp is often preferred to be as low as possible... so that the speakers impedance is "significantly higer"

If the theory of lower impedance is eaiser to drive is true than i be glad to buy the HE-6 to use it on my iphone... 

Offline fgchong

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Low impedance is easier to drive is wrong im afriad... not here to prove anything but is a matter of fact low imepdance as seen by the amp is harder to drive....

A simple fact is low imepdance draws much higher current, the amp have to source more current just to drive the speakers to the same level as a higher imedance load...

Thats why you see power ratings of 50W@8ohm, 100W@4ohm etc... The very reason being the amp is having to pump out more power to drive the lower imepance load....

A simple ohms law even tell you that a higher imedance load will see a higher voltage across it as compare to a lower impedance load...

Also the output impedance of the amp is often preferred to be as low as possible... so that the speakers impedance is "significantly higer"

If the theory of lower impedance is eaiser to drive is true than i be glad to buy the HE-6 to use it on my iphone... 

+1.  Another point to add on is that impedance varies with frequency.  What is stated on the speaker is nominal impedance and depending on design of the speaker, the actual impedance at lower frequency can dip to very low,  thus drawing very high current from the amplifier and can result the clipping of the amplifier, causing damage to the speaker and or amplifier itself.

« Last Edit: May 29, 2013, 10:07 by fgchong »
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Offline Audio

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A simple fact is low imepdance draws much higher current, the amp have to source more current just to drive the speakers to the same level as a higher imedance load...

Thats why you see power ratings of 50W@8ohm, 100W@4ohm etc... The very reason being the amp is having to pump out more power to drive the lower imepance load....


This alone has proven my point, you drive 8 ohms you get only 50W...hard to drive. right.?...The same amp (of this era) also give you 100W@4 ohms....easier right?  you got 100W from that same amp...no need to upgrade...easier to drive the 4 ohms than the 8 ohms.

You must not stick to old-time thinking, need lots of current, cannot provide, means hard to drive low impedance.  Times had changed.

(Audio)

Offline Audio

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If the theory of lower impedance is eaiser to drive is true than i be glad to buy the HE-6 to use it on my iphone... 

Which again proved my point.  Iphone can drive your everyday low impedance headphone  / earphones, (10 to 24 ohms, low  impedance) but harder to drive HE6 (50 ohms, higher impedance)...
 
(Audio)

Offline watchdog

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Let me give this a shot.

High impedance speakers may not make full use of the amplifier power. Most amplifiers can deliver more power into loads below 8 ohms compared to an 8 ohm load.

However, as more current is being drawn by a low impedance load, the amplifier must be able to deliver sufficient current. If you look at independent tests on amplifiers in magazines, it is usually the beefy solid state amps that can continue to deliver double the power into each halving of load.

Car amplifiers are designed to drive fairly low impedance loads. The car guys tend to use low impedance speakers (especially subs) like 2 ohms to drag as much power as possible (assuming the amp can cope with the load).

In respect of damping factor, I don't think it makes an incredible amount of difference between 11 and 15 ohms if you are talking about a solid state amplifier. If based on damping factor alone, most class D amplifiers would win the game.
Less is more !

Offline flowerpot

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This alone has proven my point, you drive 8 ohms you get only 50W...hard to drive. right.?...The same amp (of this era) also give you 100W@4 ohms....easier right?  you got 100W from that same amp...no need to upgrade...easier to drive the 4 ohms than the 8 ohms.

You must not stick to old-time thinking, need lots of current, cannot provide, means hard to drive low impedance.  Times had changed.

(Audio)

maybe you misunderstand my point....

very clearly i states that

"Thats why you see power ratings of 50W@8ohm, 100W@4ohm etc... The very reason being the amp is having to pump out more power to drive the lower imepance load...."

power is not free... nothing to do with "no need to upgrade" you get 100W...the amp has to work for it to reach it... if the amp is not capable of sourcing the require current it will struggle to drive the speakers...

the fact that the amp has to double the current output in order to drive the lower load is simple enough to understand...

a very simple example...drive 8 ohm u need 1A... 4 ohms u need 2A.. which is easier to source from the amp... 1A or 2A...

its up to you... im here to states the correct fact from electrical point of view.. nothing to do with old thinking.. im still pretty young... if you insist 50W@8ohms and 100W@4ohm means easier to drive for lower impedance from the amp pov then thats fine for me...




Offline Audio

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Why is the assumption always not having enough power , not having enough current, if we have lousy amplifier and assume so many other variables tp distort the case then how can we be decisive in anything at all?

Same amp, drive 8 ohms only 50 watts, drive 4 ohms 100w, 4 ohm speaker easier to drive. Period.  Simple.

(Audio)