Most likely you will get some improvement in the bass at lower levels. But another solution is to add a powered sub and keep your existing amp if you like it.
56 responses Add your response
When I replaced my Bryston 3B w/ a newer 4B ST the bass sounded much fuller. So yes in this instance the increase in watts and a newer more refuned design resulted in a warmer more refined sound w/greater bass. Presently I'm using a Rega Brio 3 which is rated for 49w per ch. It has a wonderful warm sound w/great bass. I'd audition one. If your lacking bass after this amp, you my need to add a sub or buy different spks. Yes, there is a substitute for great bass w/less watts w/the Brio 3.
Generally speaking, a more powerful amp may give better bass but it also depends on the character of the amp itself. I am pretty sure you will get better and more defined bass if you substitute your 35W NAD amp with say a Krell integrated. Also, Jaybo is correct in that you won't need to crank up the volume higher to appreciate more bass with a substantially more powerful amp. Even that, your speakers may be limited in bass response, and the suggestion of adding a subwoofer is good idea if the frequency range of your Rega speakers does not extend down to 35Hz or so. Adding a more powerful amp won't help much if your speakers ain't up to it.
I don't seem to hear much bass until I turn my amp up to a level that doesn't suit my listening habits.
First thing to do is get an SPL meter and some test signals. Pick a comfortable level at say 1KHz and then work down in frequency. You'll then know whether or not your speakers are capable of any real bass. The other thing to consider is that what you are hearing when you turn up the volume is simply woofer distortion. No amp can correct your speakers. A subwoofer is a viable solution.
Ok, fourth time trying to post to this thread. I'm surprised that you haven't been asked yet what speakers you are talking about? Also, this could just be a placement issue. Have you moved your seating position and speaker position around enough to rule this out? If you do not already own the oppo 980 I would suggest getting the new 983,it has better sound quality from the analog audio output.
Something quite basic , that has not been touched upon here , is the configuration of those added watts .
Watts are a result of the amount of volts and amps going through a device . Amps are the driving force of the volts which do the work . It is the amps that will drive the volts through a tough crossover network and into a power hungry woofer .
You can have the same amount of watts with 2 amps (with higher voltage) or 20 amps (with lower voltage). But the 20 amp watts have the ability to do much more with a tough load . This is why some amplifiers will double down as the ohms decrease within a speaker , such as 100 watts into 8 ohms , 200 watts into 4 ohms , 400 watts into 2 ohms and so forth . Where as a low amperage amplifier may do 100 watts into 8 ohms and 125 watts into 4 ohms etc.
And yes , it usually costs more to make high amperage watts than high voltage watts .
Just a though .
Saki, what control over the "configuration," as you call it, do you think we have?
An amplifier is an approximation of a voltage source, the current drawn and thus, the wattage dissipated, is a function of the load across the amplifier's output. The voltage output of the amplifier is a function of its voltage gain and the input voltage.
It makes absolutely no difference whether or not an amp is capable of doubling its power output as its load is halved.
Thanks to all for the responses to this point. Would love to hear any other opinions. Consensus seems to be that more watts will help my situation.
I have considered a digital amp (Trends)as Shiva suggested, not sure if it would deliver the goods on an 89dB-rated speaker. I'd love to try Rega Brio 3 (loved my Brio 2000) but I really want a remote, and again, wondering if "49" wpc will bring the bass to life. How would it work to use the volume control on the Oppo with a Brio having it's volume knob turned up?
Another comment - I've seen it mentioned more than once that an amp that can double its 8 ohm watt ratinginto 4 ohms is regarded as a "high current" amp, as Saki suggests. Bob, are you saying that this characteristic doesn't indicate a high-current design or just that this isn't an indication of bass capability? I'm looking at an amp that does 100 wpc into 8 ohms and 125 into 6, no 4-ohm rating given.
An amp will not correct the physical limitations of a speaker no matter how many watts it's capable of producing.
If the impedance of the speaker is high in the bass region it will not drawn much current and won't require many watts to drive it.
I'm saying that for a given output voltage (this determines the volume level) the impedance of the load determines the amount of current drawn and thus the amount of power (watts) dissipated. It doesn't matter if it's a 50 watt integrated amp or a 600 watt monoblock amp.
The Parasound JC-1 can double its power from 400 watts into 8 ohms to 800 watts into 4 ohms. A Bryston 7B SST can produce 600 watts into 8 ohms and 900 watts into 4 ohms. Which amp would be considered a "high current" design? The Bryston is capable of sourcing more current than the JC-1 into 8 ohms and 4 ohms, but it does not double its power rating when the load impedance is halved.
The only thing that matters is that the amp is capable of sourcing the amount of current drawn by the load that will provide the volume level you desire and do this with little distortion.
The only way to get bass is with a speaker (or speaker system) capable of producing bass.
I was not addressing the speaker characteristics . Neither was the original poster ! He was asking about watts .
Of course the speaker will make a big difference in the final output . You can't get 20hz. out of a speaker designed to only put out 80hz. I consider that a different topic for discussion !
I was merely trying to show that there are different watts capable of doing different things .
We have a control over the configuration by our purchasing decisions . When one has a tough load to power , doesn't one seek out the amps that will power that load ? There are amps that have a high current output and there are amps that don't ! This is why some amps will power that tough load and others will not , even though they 'seem' to have the same amount of power.
By your way of thinking one could assume that a 100w HT
receiver , such as HK , Pioneer , Onkyo , Denon and etc.(high voltage watts) would have the ability to drive a 1 ohm bass load with a 4th order crossover network of an 80db. speaker . I think that you probably know better than that .
As to your example with Bryston and Parasound , some companies list there ratings conservatively and others exaggerate . Which makes it even tougher to pick the right amp for the job ! That is why we do not use generalities and company spec sheets but specific brands and models .
Saki, I don't mean to be a pain in the rear, but I'm probably not interpreting your comments correctly. So they confuse me...
The OP was asking whether more watts would produce more/better bass for a given volume level. It's the volume level that is critical to his question. If a 50wpc amp is capable of driving your speakers to the desired volume level, having 500wpc will not yield more bass at that same volume level. That is the crux of the question as I understand it.
Since an amp isn't going to yield more bass, what will? A speaker will and that's why speaker characteristics are relevant to the discussion.
I was merely trying to show that there are different watts capable of doing different things .But, the problem is that you can't go out and buy amplifiers with different watts. Maybe I misunderstood what you're saying. It sounds like you think amps by design produce watts with different percentages of voltage and current. They don't.
By your way of thinking one could assume that a 100w HT receiver, such as HK, Pioneer, Onkyo, Denon and etc.(high voltage watts) would have the ability to drive a 1 ohm bass load with a 4th order crossover network of an 80db. speaker . I think that you probably know better than that .
Why would you think it can't? You can do the arithmetic. That 100w receiver can easily drive a 1 ohm load all day long. It just can't drive it to the same volume level that it can an 8 ohm load (assuming the same sensitivity). To dissipate 100 watts across an 8 ohm load you need to source 3.54A, which yields 28.3V. A 1 ohm load drawing the same 3.54A (because that's what our amp is comfortable sourcing) will have 3.54V across it dissipating about 8 watts. Since a speaker is a transducer that converts electric power into acoustic power, 8 watts will not produce as high an SPL as 100 watts. There is no such thing as high voltage watts or high current watts.
Again, maybe I'm misunderstanding what you're saying.
Bob_reynolds has it right. depending on what the speaker impedence is at the bass frequency one is talking about, the speaker determines what wattage (power) is necessary to give the note at the required volume. If 100 watts are necessary into 2 ohms, then that will require so many amps, which will be more amps than if the impedence at that frequency were 8 ohms, but still 100 watts are required.
If the 100 watt amp is capable of delivering the amps at the lower impedence, then a more powerfull amp isn't going to be more capable of delivering more bass.
IOW, if the speaker can't do the job, then a more powerfull amp isn't going to compensate.
Let me try , I could be all wet here , it's been a very long time !
Volts X Amps = Watts , the basic electrical power formula if I remember correctly .
Now you can get 100 watts with 20 volts and 5 amps - 20v X 5a = 100w , high voltage watts .
And you can get 100 watts with 5 volts and 20 amps - 5v X 20a = 100w , high amperage watts .
Further , really going out on a limb here ... I believe that the differences in these two examples is achieved within the power supply , ie. the output transformer , and the way that it is constructed .
I believe that the transformers' size and configuration will govern how much amperage is produced with a given amount of voltage . It takes a larger/heavier transformer to make big amperage as opposed to a smaller/lighter transformer to make small amperage .
Isn't this the reason that a 5.1 A/V receiver , with its smaller transformers , can weigh in at 25lbs. and a 2 channel amp , with larger transformers , can weigh in at 50lbs. while both putting out 100 watts/channel ? The A/V receiver will give you anemic sound under a tough load whereas the 2ch. amp is capable of giving sound with much more drive and authority .
These transformer primary and secondary windings , and their proportions , are the reason that when you cross the speaker cables on that receiver you get a light show and probably trip a breaker or blow a fuse . Do it on a welder and you can melt metal together . Both driven by a 120v/20a circuit .
Now I understand that the speaker will require X number of watts to operate that tough load . But it is the configuration of those watts that determines how that tough load is handled .
Am I making any sense here ? Kindness counts !
Volts X Amps = Watts , the basic electrical power formula if I remember correctly .
Yes, that is correct. But, the thing that you are missing is that amps are voltage sources (better ones are termed "constant" voltage sources). We want the output voltage to remain the same regardless of the load. Having a low output impedance works in our favor here. The output voltage is determined by the input voltage (where we set the volume control on the preamp) and the voltage gain of the amp. The current drawn from the amp is determined by the load and the power dissipated by the load is determined by the voltage across the load and the current through the load (as your formulas show).
Once you pick a volume setting you have locked the output voltage -- it's not going to change. The only variable is the load and it alone will determine the amount of current drawn and power dissipated.
As an example. Let's say that 5 volts drives your speakers to the desired SP level. If I create those 5 volts with a 20 watt amp or a 2000 watt amp, it makes absolutely no difference. The amount of current drawn from both amps is exactly the same and the power dissipated by the speakers is exactly the same. So having more watts on tap can not create more bass (or more of anything else for that matter) because nothing has changed.
As I said the key to the OP's question is that the volume level did not change.
I believe that the transformers' size and configuration will govern how much amperage is produced with a given amount of voltage .
Sorry, but it doesn't work that way. The voltage is determined by the user adjusting the input voltage as she changes the volume setting on the preamp. The current then drawn is determined by the load. The power supply (and the output section as well) can either source the required current or not.
Yes, you are correct that it takes a larger/heavier power supply to source large amounts of current, but what that provides is higher SP levels (larger output voltage) into lower impedance loads. If I don't require the higher SP levels I gain nothing.
But it is the configuration of those watts that determines how that tough load is handled .
In theory yes, but unfortunately, we have no control over the configuration. The only control we have is over the output voltage and the load. In this discussion we are nt changing the load (using the same speakers), the output voltage is the only variable. It makes no difference how large or small the amp is as long as it can create an output voltage to create the SP level we desire.
Bob_reynolds, we *do* have some control over that 'configuration' of voltage vs. current. It has to do with the output impedance of the amp.
A higher output impedance can deliver excellent bass if properly matched with the speaker; conversely an amplifier with very low output impedance will deliver poor bass if poorly matched with the speaker.
However it is more than just a conversation about equipment matching; there are two different paradigms that are in common use in high end audio:
IOW, getting bass out of the speaker is not a function of the amplifier **or** the speaker, it is a function of how well they work together. This comes about out of intention- for example, the ability to double power as impedance is halved is not the same thing as saying that the amp will play bass.
Furthermore, amps that are direct-coupled from input to output (and in a very non-intuitive way) are often at a disadvantage in playing bass as they have the ability to modulate their power supplies. As soon as they do this the bass dries up. This is due to the fact that the amplifier LF pole is lower than that of the power supply, when it should be the other way around (something that you can't do with direct-coupled amplifiers unless you use a battery).
Correct. In the old days, some amplifiers had a 'Damping' control, which was a potentiometer that allowed you to adjust current feedback (not voltage feedback). Essentially, this allowed you to get a better match between the amp and speaker.
This was at the time that the Voltage Paradigm was evolving. Once the ground rules were laid out, the 'Damping' controls disappeared- everybody just used a lot of feedback and called it good. The problem is that feedback itself functions at low frequencies (bass region) as a dynamic compression device. You simply aren't going to get good bass (or **as good** bass) if you are running a lot of feedback, even if your system is matched within the Voltage Paradigm.
This is why a smaller amplifier that has little or no feedback can often seem to play better bass (more impact, more definition, more articulation) than larger 'powerhouse' amplifiers that would seem to have it all over the said smaller amplifier. Of course, such an amplifier itself has to be able to operate properly with the speaker in order to revel these traits, but its not that hard to find speakers that are compatible and capable of delineating the differences between amplifiers that I defined above- the speaker *does not* have to be full range.
I find that class of operation plays a role too- class A amplifiers will have more authority; as you move more towards class B (AB1 and AB2) the authority (especially at low volume levels) goes away.
So- to play bass well, power output is irrelevant, instead the amplifier ideally is low or zero loop feedback and class A, given that such an amplifier also works well with the speaker being used. This of course assumes that the amplifier does not have a low frequency cutoff that interferes with bass reproduction.
Yes, tubes and transistors; the jury is out on Class D as it inherently is not Class A.
Tubes generally are usually operated closer to Class A than transistors usually are; most transistor amplifiers are biased at such low idle currents that its driver transistors (not the output transistors) are actually what is driving the speaker at low volumes. Tubes are inherently more linear than transistors, especially triodes, so tube circuits tend to be simpler and operating with less feedback, in fact I think its safe to say that the majority of triode amplifiers don't run loop feedback at all.
So your "punch and body" is coming from the reduced levels of negative feedback and the additional authority gained by operating at or near class A.
Atmasphere, please correct me in any of the following...
An amp with a low output impedance (a fraction of an ohm) approximates a voltage source when used with conventional speakers whose impedance is several ohms. The reason for this is that the output impedance of the amp is a very small percentage of the total impedance of the amp/speaker circuit. Thus, the impedance of the speaker approximates the total impedance and determines the amount of current drawn from the amp. The voltage drop across the output impedance of the amp will be small and the voltage applied to the speaker will effectively be constant regardless of the speaker's impedance curve. This implies that there is less concern of choosing speakers for this type of amp.
An amp with a highish output impedance (several ohms) makes a rather poor voltage source because its impedance is a significant proportion of the total impedance of the amp/speaker circuit. As the impedance of the speaker changes, the voltage drop across the output impedance can become significant so that the voltage applied to the speaker is not constant, but is in fact determined by the impedance curve of the speaker. This implies that choosing speakers for this type of amp is more difficult.
It seems to be well accepted that when matching source components to preamps and preamps to power amps that the input impedance of the load be at least 10 times that of the output impedance of the source. Why is this not the rule for matching power amps to speakers?
A question... I have it in my head that a speaker converts electrical energy into acoustic energy. Power, Voltage, Current and Resistance are all algebraically related.
So let's say that my speaker has to dissipate 20 watts to produce a desired SP level and that my speaker is effectively an 8 ohm load. As Saki70 pointed out, those 20 watts can be comprised of 2 volts and 10 amps or 4 volts and 5 amps or an infinite number of combinations such that the product equals 20. Well, which combination is the "right" one?
Since P = I^2 * R, I = SQRT(P / R). Thus, I = SQRT(20 / 8) = SQRT(2.5) = 1.58 amps. The voltage is then, V = 20 / 1.58 = 12.66 volts.
It doesn't appear to have anything to do with the amp, high impedance or not. What's wrong with this picture?
It doesn't appear to have anything to do with the amp, high impedance or not. What's wrong with this picture?
If you think of the amp output impedance and the speaker load as a very simplistic set of resistors in series then you will see that the output impedance has a big influence on the power ultimately reaching the speaker.
Imagine if you were to increase the output impedance to infinity, then the voltage across the resistor representing the speaker would be close to zero - so almost no power reaches the speaker. Conversely, if you assume the output impedance of the amplifier is Zero, then the voltage across the resistor representing the speaker will be a maximum and it will see maximum power.
In practice, there is no such thing as infinity or zero - typically a rule of thumb is 1 to 10 => if the amp output impedance is a tenth of that of the speaker minimum resistive load then to a first order approximation amp ouput impedance can be ignored and the speaker sees all the intended drive voltage (based on the source signal and your volume setting).
What gives tubes the "punch and body" at lower volumes ?
If you understand the above and you think about a typical woofer with a resonance peak at the low end of the bass response (where the impedance may rise from 4 Ohms to 20 Ohms) then it is obvious why a high output impedance amplifier such as one with an 8 ohm output transformer) will sound punchy in the bass, as more voltage/power will reach the woofer at the resonance frequency than in the lower impedance midrange. So in a relative sense the high impedance points get more juice...
Probably the most straightforward and effective solution to get better bass to your hearts content at low volumes is to add a carefully matched, adjustable sub. ACI and REL are the ones I would consider personally. OR if you are comfortable going used, a second hand M&K might do the job for lower cost.
I cannot live without a full and extended low end and I use a vintage M&K sub for this exact reason with a pair of otherwise fairly bass challenged Triangle Titus monitors positioned way high up in cabinets (~6 feet off the floor) in my 2nd music/A/V system with excellent results. Your system appears much less bass challenged than mine, so I think its a pretty easy, slam dunk solution for you.
Hi Bob, If you've not looked at
maybe now would be a good time.
Of course it is quite true that if you make 100 watts into a given impedance, it doesn't matter what made the power, the current and voltage will be the same.
Where things get interesting is when you have an amplifier that makes constant power, as opposed to constant voltage. What happens here is that as the load varies, the current and voltage both change with it to that effect. This is what I was referring to in my posts above.
It is **not** true that all speakers are "voltage" driven, in fact before the Voltage Paradigm was developed, tubes (and often zero feedback tubes) were the only game in town. Designers had to accommodate constant power so to get flat response; they had to be a little more careful.
Some examples of where constant voltage is not so helpful:
ESLs- Constant Voltage amplifiers have trouble making bass while too bright for comfortable listening due to the impedance curves typical of ESLs: high impedance in the bass, almost none in the highs. You need constant power to make that sound right.
Full-range drivers/horns- Most high efficiency speakers have tighter voice coil gaps (hence their cost) which creates higher reactivity. The reverse EMF thus generated can wreck havoc upon an amplifier with lots of negative feedback. The result is excess harshness (ringing) at high frequencies; the main source of many listeners opinion that horns are brash, honky and the like.
Its not difficult to choose a speaker for such an amplifier with a high output impedance (also known as a 'current source' amplifier to use Voltage Paradigm vernacular). All you have to do is look at the intention of the designer. Some examples: Merlins, Sound Lab, most horns (except Avantgardes), Lowthers, Fostex, PHY and the like, The original AR-1, Audiokinesis, Coincident Technology, Rogers LS3/5A, headphones, Magnepan, Reference 3A Loudspeakers, to name a few.
If the impedance curve operates independently of resonance, you can count on the speaker being a Power Paradigm device rather than Voltage Paradigm. Nearly all planars are Power Paradigm devices. Of course, a smooth impedance curve makes the speaker available to both camps- Avalon is a good example of that.
The two paradigms are responsible for a lot of debate in audio- tubes vs transistors, objectivist vs subjectivist...
What is really going on is that the Power Paradigm nowadays operates around the idea of the rules of human hearing, where the Voltage Paradigm operates around the concept of bench measurement. I hope it is obvious that understanding the rules of these two paradigms creates also a means for using transistors in a musical way- Pass 1st Watt amps and Ridley Audio are good but rare examples.
I am of the opinion that when it is possible to quantify the right measurements on the bench, such as the amount of odd-ordered content generated with a dynamically changing waveform, then a new and encompassing paradigm will emerge. Until then, we are stuck with two schools in competition- and the continuing need to match equipment properly and audition it at home.
is it accurate to say that a higher current amp with wattage X will generally produce as good as or better bass than a lower current amp also of wattage X, depending on load, and all other factors aside?
In my case, I can vouch for the fact that a 100 w/ch Musical Fidelity A3CR (higher current) produced better bass at all comparable volumes than a 350 w/ch Carver m4.0t (lower current) with my notoriously power and current hungry Ohm Walsh 5s, which also have a reputation, similar to electrostats, as having a harder load to handle than many designs.
With my other speakers, Dynaudio Contour 1.4mkII, Triangle Titus Ohm Ls, and smaller Ohm Walshes, all of which I believe provide less difficult loads to drive, the difference in bass levels between the same two amps at same volume levels was not nearly as noticeable.
Mapman, no, however the match between the speaker and amplifier is paramount. If the speaker has a low impedance at low frequencies, you are going to have to provide the current that making power into that load demands by law (Ohm's Law- no pun intended). The Ohms were always a difficult load! As you have seen, with less difficult loads the requirement for high power at low impedance is less important.
The flip side of the coin has a question- why go where angels fear to tread? IOW **if** the best sound is your goal, it has been shown that higher impedances favor transistors as well as tubes. A transistor amp driving a 16 ohm speaker will sound better (smoother, more detailed, more impact) than it will driving 4 ohms, all other things being equal. So the argument of current, insofar as the goal of 'best sound' is concerned, would seem to be moot.
Saki70, as Bob pointed out above, it takes both voltage and current to make power. The issue is that if we are to make 200 watts into a set of Ohms which might be 3 ohms, the voltage and current can be easily calculated (assuming for the moment that there is no phase angle which there always is in inductive devices).
So you can also look at it as being able to make the Voltage into a load like that- which will only be possible if you can also make the current.
The use of the term 'voltage source' I think can be dangerous without the understanding of the accompanying engineering principles for which the term is a sort of shorthand. You have to keep in mind, IOW, that regardless of the amount of current or voltage that you are making, that the end result is power which is composed of both.
Low impedance amplifiers (Voltage source) *can* make constant voltage with respect to the load. Not all do.
Higher impedance amplifiers (Current source) *can* make constant power with respect to the load. Not all do.
You **must** match such amplifiers with speakers that are designed with intention to work with that particular kind of amplifier that you are using. If you do not tonal aberrations will occur.
It is true that some constant voltage amplifiers can deliver lots of current. It is not true to say that that is the same thing as having lots of bass authority. IOW any kind of amplifier can be perceived as being wimpy in the bass if not set up properly. OTOH, some amps will not play good bass no matter what you do.
In my personal case, because I like amplifiers to be relaxed at all volume levels, I will not use one that has negative feedback, as that design element adds loudness (harshness) cues. So I work with speakers that are designed for amps that have a higher output impedance. So on my speakers there are no 'voltage source' amps that will play the speaker with the authority that my 60 watt triode amps will. But that could be very different on other speakers- my bone of contention is that because the use feedback, as far as I am concerned they will never sound like real music, so who cares :)
Atmasphere, I've read your paper on more than one occasion and I probably didn't appreciate most of it. I've been tied up with other things the last few days, but I intend on reading it and I have a couple of questions I hope you'll address.
BTW, I really appreciate your contributions and patience to this forum.
First off...I would like echo Bob's accolades and offer our thanks to you for your patience and diligence in this thread ! You are one of a very few gentlemen that would not only offer some input but also stick it out for a myriad of questions as we try to learn a thing or two . A true industry leader !!!
I understand that it takes both voltage and amperage to make watts (E x I = W). And that you can have different kinds of watts ie. "voltage source" and "current source" depending on the impedence of the amp .
Can you tell us if the 'ratio' of volts to amps is the same for both types ? IOW do the watts from a "voltage source" amp generally contain more volts , than the watts from a "current source" amp ? And conversely do the watts from a "current source" amp generally contain more amps , than the watts from a "voltage source" amp ?
As you stated , "It is true that some constant voltage amplifiers can deliver lots of current." Would this be an example of a ratio difference ?
Thank you .
Saki70, thanks for your comments.
What we are talking about is 2 things: 1) output impedance as an actual raw impedance, not complicated by negative feedback (IOW 'open loop') and 2) servo gain- the amount of negative loop feedback employed.
A lot of designers see these two as the same, but they are not. A variety of Voltage Paradigm speakers *require* that the amp have some sort of feedback to accommodate the otherwise improbable impedance curves that have resulted. The feedback is part of mechanism that allows the amplifier to accommodate peaks as well as dips in the curve. You can do this with raw impedance alone, but feedback makes it easier- your amp does not have to have such a low open loop impedance.
With higher impedance amplifiers, in order to get flat frequency response on such speakers, the role of feedback becomes more prodigious. However, many of these amplifiers are probably tubes, and often tube designers will eschew large amounts of feedback as the amplifier will often exhibit some linearity without, something that is rare in the transistor world. Their hope is that you will do the right thing and use these amps on a speaker that has a higher impedance. FWIW the thinking here revolves entirely around sonic performance rather than the ram ability to simply drive a low impedance, something that usually has little to do with overall sound quality.
So we are talking about a spectrum- as output impedance is increased and servo gain decreased, the voltage/current ratio that describes the output of the amplifier changes with it. So there is not a hard and fast rule.
In the past I've seen a lot of DIY hobbyists try to add loop feedback to a 'current source' amplifier with the hopes of getting it to play a four ohm load better- with more power. It does not work. That is because the open loop impedance of the amplifier is too high to be adequate for four ohms. You can reduce distortion and flatten the frequency response using servo gain, but you can't change the power. That is why I say that open loop output impedance and servo gain are different phenomena.
The pity of this whole thing is the idea that the ability to drive 4 ohm loads is a sign of being 'beefy' or 'gutsy' (somehow better anyway) in the amp. The fact of the matter is no transistor amplifier sounds right on 4 ohms, nor does any tube amp. If you want to really see what either one is really capable of, you need a higher impedance -16 ohms is nice- to do that.
At higher impedances speaker cables are far less critical in the overall sound and all amplifiers will exhibit less colorations due to reduced distortion. Transistor coloration BTW is the harshness caused by odd-ordered harmonics at very low levels. Tube coloration is the added 'warmth' or 'bloom' that is a product of even-ordered harmonics that are at a more pronounced level. So transistors will sound smoother with more detail and tubes will sound more neutral with more detail. Win win.
Sorry there was not a simple answer to your question!
Saki70, in the old days you did. Then transistors came along, and the industry figured out that it could charge almost the same money for the transistor amps, while in fact they were costing only about 1/10th as much. Suddenly power was cheap.
It was not long before the speaker manufacturers realized that they could take advantage of this, because they could make lower efficiency speakers that also cost about 1/10th as much to make. To make them seem more efficient, 4 ohm speakers began to appear.
Its all about money IOW. But- if sound quality is your goal, then 4 ohms is right out.
So synergy is the only constant and wattage takes a backseat to circuit design for both amp and speaker . Is this a correct summation ?
Up for some more questions ?
Are global feedback , negative feedback , loop feedback , and zonal feedback all names for the same thing ?
How close to zero should we get ? I noticed that you offer up to 2? of feedback adjustability on your amps .
And what is your opinion of the use of 'autoformers' to achieve the higher speaker resistance that the amplifier will see ?
Thank you .
Saki70, I don't like the word 'synergy' as it suggests that we are going to balance one defect against another, and I think that in the case that we are talking about, the word is 'compatible' and the answer is 'yes'.
Loop and global feedback are the same thing. Zonal is usually the same as 'local' and may or may not be loop feedback, it could also be degenerative feedback. They are all forms of negative feedback, and there is a lot of verbal shorthand around, so you have to be careful.
I think what is important if you use feedback is that a) the amplifier must be fast and low distortion to begin with and b) the feedback be low enough that the odd-ordered harmonic enhancement is kept out-of-band. That really does not allow for very much feedback in practice.
The ZERO is the only autoformer I know of (we used to make a similar product called the Z-Music autoformer years ago). The concept is all about problem solving- this or that amp can't drive a speaker load that low so here's a solution to that problem. Given that that is the case, they work very well indeed. But if you had a 16 ohm speaker to start with that would be better :)