Why do they still make speakers 4ohm?

If you're really concerned, get power resistors to add more "passive" resistance.

 

Sorry, I left out the "also". The Euro wound have had power for both resistance specs. Don't forget, 8 ohms is a standard resistance for power measurements and amplifier specifications, and has been for some time.

jeff

 

Plus of course people are forgetting about what type of 'drive' the speaker system decides to use ....be it -Bass Reflex/ Ascoutic Suspension / Horn Loading.....whatever. The physical movement and behaviour properties of these various 'drives' also make speaker designers have to think and take into considerion : the crossovers, and electrical wiring values they will use.
Some people possibly think that some 2/ 4/6/8/or 16 ohm rated speaker remains at the same pohm rate across the frequency spectrum.
Now take the example I saw once in a respected magazine of a a particular well regarded brand's speaker - its Frequency Range spectrum -sweep , set against its Ohm variation range -supplied test graph.
What was rather startling was that this speaker once it reached down into the 60 -80 Hz bass range, its Ohm rate went up to a colossal 58 ohms. Talk about 'something grabbing - so to speak- and squeezing the amp's power supply'.

 

Actually I thought of that but they said that was a NO NO. Best way would be to add a external switch box that keeps the ohms at 8 to run two sets of 4 ohms.

 

Yes I looked at those charts for my KG4s which have been labled 4, 6 and 8 ohms depending on what market it was sold in. It's really 6 ohms. But on lower freq it would dip below 4 at higher freq it went up above 10 ohms and more. So 58 ohms at that low frequency is strange, thought it went up with increasing frequency.

 

You can hook four speakers to one channel of an amp at a time safely by putting them into two groups of two attached in parallel, with those groups of two attached in series. That will show the same load (in impedance terms) as a single speaker. Whether or not your amp will have enough power to play them all loudly enough is a question, and it's best to have the speakers all be identical, but it can be done - we used to do it for retail background music.

 

The 58 ohm figure is possible, which would be at the system resonance. All drivers have a fundamental resonance (free air resonance) and all speaker systems have a fundamental resonance. The resonant peak is always very narrow band, with the impedance spiking ridiculously high, but normal impedance at all other frequencies. This system resonance does not typically drive an amplifier mad. But, the damping factor can be sloppy at that frequency, and a corresponding increase in bass response. If the system resonance falls between two fundamental notes, the amplifier sees less impedance spike, and the audible effect also lessened. Better speaker design minimizes system resonance.

 

If ever anyone wonders why so many car subwoofer installations sound so boomy, it's their resonance that causes this. When system resonance is excessive, the woofer "wants" to vibrate at that frequency. Other fundamental notes can induce the resonance, like plucking a tuned guitar string that plays only one open note. I call it "one note bass". Smaller enclosures loaded with dual 12's or 15's will resonate like mad. A larger driver is not always better. I have tried to talk my nephews into a smaller single driver in mono, loaded into a larger enclosure, but nada.. Preferred are the LED illuminated 15's playing "one note bass".

 

That's interesting. I haven't personally encountered anyone doing this in about 35 years. I know a bunch of people with multi room systems but they're all in wall distribution amp set ups. I wonder how generally common it is. Certainly I don't see much equipment for sale these days with AB speaker outputs for driving multiple speaker pairs. Perhaps it's more common in your personal circle than it is generally.

Anyway if you want to use an amp for a specific purpose that requires speakers with 8 ohm impedances you can find plenty of 8 ohm speakers to use. I don't know why it follows therefore that all speakers should be designed for 8 ohm nominal impedance. Designers may want to use specific drivers and crossover circuits to get the sound they want and that may mean a finished loudspeaker system of 4 ohms impedance which plenty of equipment can drive just fine.

 

Eeeeh . . . wonder who "They" are.

In any case, I have a system where there's three sets of speakers in the same room for a stereo array. I have two 4 ohm speakers in series, an 8 ohm speaker with an 8 ohm resistor in series to another, more efficient, speaker that's wired in parallel to the other two speakers. This results in something like 5.3 ohms. The system plays as loud and as undistorted this way as any other. Mind you, the amp [an old Kenwood SR 9600] delivers 200 watts into 4 ohms, 160 into 8 so there's no lack of power here.

 

[QUOTE="chervokas, post: . Perhaps it's more common in your personal circle than it is generally.
[/QUOTE]

You have to get out of the house more often man

I just bought a brand spankin new outlaw with A/B switch. I see the A/B being used not just in people I know but in many many stores. I think maybe its less common in this niche group on the net. People here probably are more into high end audio than the general public which would explain why a/b sounds so strange to them.

 

Some interesting thoughts regarding the Current vs. Voltage Paradigm by Ralph Karsten....

The Voltage Paradigm
The Voltage Paradigm is that reigning design, test and measurement paradigm for amplifiers and loudspeakers, and is seen in many audio magazines. It assumes that the voltage response of an amplifier is the only aspect of the amplifier that matters. If a speaker is being tested, the test signals will be voltages (the power of the test signal is not considered). The ideal Voltage Paradigm amplifier produces zero THD, has wide bandwidth and is "Load Impervious".

Being Load Impervious is not exactly what it sounds like! It is called load impervious as the amplifier will make the same voltage regardless of load; it has a "constant voltage" characteristic (hence the title 'Voltage Paradigm'). It works like this: if a 'constant voltage amplifier' were to produce 100 watts into 8 ohms, it could produce 200 watts into 4 ohms, possibly 400 watts into 2 ohms (and 50 watts into 16 ohms). In all of these cases the output voltage is about 28.28 Volts RMS. We are very familiar with these charcteristics, typical of solid state amplifiers. Under this model, to be 'load impervious', the amplifier will make different amounts of power depending upon the load impedance.

Loudspeakers designed under this paradigm are said to be 'voltage driven', as they expect the amplifier driving them will produce constant voltage despite the speaker's variable load impedance.

Voltage Paradigm amplifiers inherently employ a fair amount of negative feedback. However, as General Electric has proven, negative feedback is out of sync with the the rules of human hearing, due to added odd-ordered harmonic generation. It may seem like a subtlety, but how we detect loudness is arguably the most important rule of human hearing; in other words we are violating the most important aspect of hearing in our quest for 'good' bench specification!


The Power Paradigm
The Power Paradigm assumes that amplifiers produce power and speakers are power-driven. Current produced by a power amplifier is not ignored and is considered in the amplifier's power response. Under this model, the ideal amplifier will make the same power into all loads, 4, 8 and 16 ohms. The typical amplifier, in this case, is a vacuum tube amplifier which usually makes its power into these loads via taps of its output transformer. There are a small number of transistor amplifiers that are designed with this behavior in mind also. Ideally amplifiers under this paradigm have little or no feedback. The Voltage Paradigm refers to such amplifiers as 'current source' amplifiers but the term is not accurate; in reality they are what they are called - power amplifiers.

Zero feedback power amplifiers have seen a resurgence in the last two decades, based mostly on their sonic character. Voltage Paradigm adherents will state that that character is based on distortion, but the truth of the matter is that what is really at the heart of it is the lack of distortions that humans find objectionable. In other words, this approach is based on the reality of the rules of human hearing, rather than bench specification.

In addition to a constant power characteristic, the ideal Power Paradigm amplifier will be low in objectionable distortions, while otherwise having similar qualities to Voltage Paradigm amplifiers if possible: wide bandwidth being an example.

Loudspeakers that operate under Power Paradigm rules are speakers that expect constant power, regardless of their impedance. Examples include nearly all horns (currently the Avantgarde Trio is the only known exception), ESLs, magnetic planers, a good number of bass reflex and acoustic suspension designs. Horns, ESLs and magnetic planers do not get their impedance curve from system resonance and so benefit from a constant power characteristic and indeed, many of these speaker technologies are well-known as good matches with Power Paradigm amplifier designs.

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

 

Why stop at 4 ohms, why not shoot for zero electrical impedance and drive with current ?

It's a bit of an artificial construct '4 ohms' because much of it derives from intentionally added coil resistance rather than a true reflection of mechanical power coupling into the air. What we see today is a legacy of decades of voltage drive, it's the way the way evolution took us - but it ain't necessarily optimal, it's just 'compatible' with conventional amplifiers as I see it. If one explores outside the box, there's still opportunity in the future for current-driven speakers to outperform voltage-driven speakers - but one has to design the drivers and amplifiers from scratch to achieve gains IMO. Just my 2p worth.

 

You have to get out of the house more often man

I just bought a brand spankin new outlaw with A/B switch. I see the A/B being used not just in people I know but in many many stores. I think maybe its less common in this niche group on the net. People here probably are more into high end audio than the general public which would explain why a/b sounds so strange to them.[/QUOTE]

Fair enough. I just looked at the top 20 selling integrated amps at Audio Advisor. 40 percent of them are set up to drive two sets of speakers -- so less than the majority but a significant portion. Of course it used to be a very common function on receivers back in the day so I suppose people using vintages stuff also may be doing it. No shortage of 8 ohm speakers of course out there if you want to drive two pairs (harder to find 16 ohm stereo loudspeakers these days), though, and it looks like any of 'em will handle a single set of 4 ohm speakers (is it correct that with two 4 ohm speakers you in the A/B set up you basically have 'em in parallel so you're presenting a 2 ohm load to the amp? Not too many amps are going to be happy driving a 2 ohm load).

 

Pure nonsense. GE had a lot to do with the design of polyphase large motors and generators, turbochargers, gas turbines, and semiconductor power control but they never wrote or did much with audio, aside from a few consumer items and a few broadcast bits.

Stan White was saying all this in the fifties and it was one of those things that amounted to "If the queen had......" Either a current amplifier or a voltage amplifier will work with easily understood, designable crossover networks. The constant power paradigm was feasible for single driver applications but with multiple drivers and crossovers you got in trouble quickly, designers realized this, and that was the end of that. Every once in a while some DIYer builds the old Powertron amplifier and finds it okay with a single driver system or for a midrange on a bi-amped system.

http://www.stan-white.com/a_doc_pwtr_1.htm

Ralph Karsten has invested a lot in his OTL circlotron products and he is going to keep pounding that drum forever (his patents, never all that resistant to challenge in the first place, will be expiring shortly), but most of us quit listening a while ago. It's like the Dvorak keyboard, the Deseret Alphabet or the hydraulic suspension on Citroens.

 

Well, if you listen to what any of these manufacturers have to say long enough, you realize that they all have their own agenda, and certain philosophies they adhere to, somewhat rigidly at times. The Circlotron may be going the way of the Do-do Bird for all I know, but in certain situations, I've actually heard it sound good, odd as that may seem. FWIW Roger Modjeski has described Ralph's thoughts on the subject of voltage/current paradigm as "unusual," and disagrees with Ralph quite a bit. Roger seems to favor the Futterman configuration of the OTL because of its low output impedance (high damping), and in contrast he describes the Atma-Sphere as "a constant current amplifier [with] high output impedance and poor damping."

However, I respect both manufacturers based mostly upon what I have heard of their designs, and not necessarily what they have to say about it. Or at least not all of it.

 

I remain optimistic that an ultimate speaker/amp drive interface is yet to be implemented, and so ultimate speaker performance as a class is yet to be realised.

For example, ever considered what a 'dip' in speaker impedance to below that of the coil resistance actually means ? Like how would one achieve it if one wanted to? Without getting heavy, the speaker must be contributing at least some element of negative resistance as part of 'active' or mechanical impedance. Star trek aside, it's not nice behaviour, yet common enough IME.

I think some aspects of the Karsten extract might at least point in the right direction, even if not there yet. Sure there's lots to disagree with too IMO.

 

The Circlotron was invented when Karsten was in grade school and is, as Norman Crowhurst explains, a circuit topology invented to get around other patented circuits doing similar things with regards to suppressing crossover distortion, e.g. the McIntosh Unity Coupled circuit. It originally used an output transformer, albeit one much smaller and of lower turns ratio than the common output transformer in use in the conventional circuit. Electro-Voice manufactured the original Circlotron amplifiers commercially. The circuit is well documented in the Audio Cyclopedia and was at least ten years old then.

http://www.tubebooks.org/Books/Atwood/Crowhurst Cooper 1956 High Fidelity Circuit Design.pdf

Karsten basically realized a derivation could be built making the output transformer unnecessary, and did so. Those of a certain age will remember that there was a big dispute between Karsten and someone else when Ed Dell published an OTL design Karsten believed infringed on his patents, and he has been involved in many controversies since. He appears to be a litigious fellow.

No topology of OTL amps can get around the fact that the vacuum tube is inherently a high voltage, low current device. They (OTL tube amps) work in hi-fi service because, and only because of the high crest factor and low average power used. Owners of the original Futtermans who played hard rock (compressed low crest factor) music loud through them into low efficiency speakers will tell interesting stories of catastrophic meltdowns. If memory serves, Dave O'Brien refused to test them after one went nuts on the Mc portable test bench.

 

I am corrected, thankyou, John M.

 

Yes. Then that means the magnitude of the speaker's impedance must 'dip' lower than the resistance of the voice coil! It's easy enough to say '2 ohms', but conceptually it's a bit of a toughy I reckon. Here's my 2p worth as to why:

Speaker impedance say '4 ohms' is taken to mean the magnitude of impedance - but actually it's not that simple and there is always time element involved (lead or lag) for at least part of the impedance. Convention terms the resistive element of speaker impedance 'real' and it can dissipate energy or get hot, but not store it - and this part has no time lag. The time lead/lag element is termed 'imaginary' and it can store energy but not dissipate it. Real and imaginary components of impedance aren't equivalent or interchangeable. But must be combined by calculation to properly express overall impedance a magnitude and a phase angle. So when we abbreviate impedance to say '4 ohms' we mean the magnitude and assume that's the 'real' element. Usually it is, because coil resistance dominates, but we can't really properly express impedance this way because it ignores the time or lead/lag aspect which matters a lot.

When we say a '4 ohm' speaker dips to '2 ohms' what we mean is that the magnitude of the impedance has become 2 ohms. But since we know that the 'real' voice coil resistance might be say 3.8 ohms, we can say that the speaker has contributed a negative 'real' resistance. ie the speaker has acted as a real source of energy ! Aside as to what is going on mechanically to make this appear to happen, it really can't be good and the energy had to come from somewhere. How and whether a conventional amplifier copes depends much on its topology, and also on the 'imaginary' or lead/lag element of the '2 ohm' impedance. Not all '2 ohms' are equal, and not all amplifiers are equal.

I just see the whole issue as non-ideal and potentially avoidable one day perhaps.

To keep maths out of the way, here's a mathy link which sets out some of the concepts and terms

http://en.wikipedia.org/wiki/Electrical_impedance#Complex_impedance

Just my 2p worth.

 

The graph I originally referred to , was for a pair of big English KEF's that had the strange 58 ohm resistance rate in its speaker system's bass region

 

I would love to know what manufacturing speaker company actually made pairs of the English built, 2 way -( 4 ohm rating, too !) neophene -rubber speaker surrounds / bookshelf size /ascoutic suspension Sony SS -85's speakers - for Sony. . The cabinets were also nicely finished and solidly constructed. I originally brought 3 pair - and let a friend have, for free - one pair to complete their system. I still have the other 4 - and would not ever part with them. It is always a pleasant listening surprise when they are asked to perform on organ music. Used in a small 11 by 9 foot spare room - they 'load' the room perfectly. Brought years ago for under $200 a pair- brand new- for use in one of my four current home operating Hi Fi systems : I consider them , one of the best buys I ever made , with Hi Fi equipment.

 

If I am correct, the old hi-fi axiom was: amplifier power was dear to produce, so go instead with big cabinet - highly efficient speakers - that had minimal physical speaker "flex" movement - that were cheaper to produce. Usually 15/16 ohm speaker rating was also then , the norm.
Then came the days of high power cheaply - produced high transistor amplifier power....and small inefficient ascoutic suspension speakers like AR with large air push movement 'flex' to produce bass in a smaller space, became more both the requirement and as much a viable practical option. We started seeing accompanying messages in ad blurbs for speakers "To be used with AT LEAST .....an amp of ....such & such.... power watts rating"
Can someone inform me if I am I correct , thinking .THAT IS :...."it was due to the new imperative - of now extra- considering , keeping the speaker pole piece WELL WITHIN the speaker's windings / working magnetic gap area.... and to stop any 'open circuits' happening from over extension movement? Since -now, 'floppy speaker cone' principles etc. were being used so often? .