Hi Amp discussion Guys,
I've made a new thread for you.
Thanks
Mark.
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Can you explain further?
Never put that in question or else I wouldn't be a lucky owner of MA drivers.
But the question is if we have two driver with identical electrical and acoustical but drifferent mechanical parameters, would that with less damping (>Qms) has more clean and open sound?
I've made a new thread for you.
Thanks
Mark.
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Can you explain further?
Never put that in question or else I wouldn't be a lucky owner of MA drivers.
But the question is if we have two driver with identical electrical and acoustical but drifferent mechanical parameters, would that with less damping (>Qms) has more clean and open sound?
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Qm is largely a measure of the shape of the impedance peak at resonance. The low frequency response of a loudspeaker driven by a currnt amp highly depndnt on the impedance curve. When impedance rises the power output of the amp increases, so to keep flattish LF response you need a speaker system with a flattish impedance curve (ie low Qm, a system Q of 0.5-1 would be ideal)
But the question is if we have two driver with identical electrical and acoustical but different mechanical parameters, would that with less damping (>Qms) has more clean and open sound?
I don't think it is possible to have the former, and since the Qm is a measure that describes the behaviour of the system at resonance, then i would think any effect on clean & open (which is more a MF + HF thing) is indirect, a side effect with no direct correlation to Qm.
dave
Amps are not current source but voltage source, so when impedance rises the power output of the amp decreases which is accordant to resonance theory. But, the truth is that high-end amps with low feedback don't "like" high impedance deviation.
From article: "more clean and dynamic. And when you look at it, you find it is very simple, because they have less loss. The surround is easier to move, the spider is better constructed, they have better air flow, higher sensitivity.". But also stated: "the old drivers (high Qm) were much quicker. They had some resonances, but you could get rid of that in the crossover.". Some resonances? Where? In MF/HF range? If so that would not be good for FR driver.
It seems that MA's choice of Qm~2 is good balance between two extremes.
Most amps are close to voltage sources, but there are solid arguments, that given that a speaker is a current device, they are best driven by current amplifiers. Typical SE amps are often very close to sitting on the border between current sources & voltage sources -- they tend to like flat impedance.
It is vry educational to take a number of spakers & a variable transimpedance amplifier (one that has a knob on it that changes the amp continuaously from voltage amp to current amp. Each speaker tends to have a spot whr it sounds best.
Higher Qms also means that you have a driver that rings more at resonance.
Except for the better sensitivity bit, you have just described an Alpair driver.
What works best is a very complex dance of trade-offs and cannot be considered but as part of a system with the amplifier (and the cable that connects the amp to the speaker).
dave
Ufff, all amps are designed to be constant voltage source and likewise all drivers are designed to give flat(desired) freq response when applied constant voltage. There are only "less ideal voltage source" amps. If you would have ideal constant current source connected to speaker there will be deviation in potential difference on speaker in freq domain. Deviation will be proportional to impedance curve so there will be oscillations in freq response - SPL (power dissipation) gain at speaker resonance(s) and toward HF - some kind of equalizer - unless you have speaker with flat impedance curve. Unpredictable if you don't know impedance curve and some of the best loudspeakers could sound terrible with such amp.
That is not true at all. First Watt F1 & F2 are 2 examples of SS current amps. We have 2 Transamps here, designed first & foremost as current amps. Most SE tube amps are not voltage amps.
I am working on some current drive speakers so that i can take full advantage of current amps. Joe Rasmussen has some done.
dave
I hope to build an F2 that i have a boards for. I will let you now how it stands against the Aleph J, driving the 10.2's. surprising how little power you need to make these babies sound goooood! Everything that i have read suggest that current driven amps are superior in terms of their control over the driver, which in theory, would give a better more accurate response. Just limited in power. I am no expert though, just going on what Mr Pass has said along with some articles from some other semi-smart people.
Side note; Mark, did you haev to come out with a new driver
I already have an itch for the A7.It's subjective. The same why some people prefer a Labyrinth or back loaded horn over an acoustic suspension for bass.Can you explain further?
But the question is if we have two driver with identical electrical and acoustical but drifferent mechanical parameters, would that with less damping (>Qms) has more clean and open sound?
I interpret what i read a bit differently. Control over the loudspeaker -- as in amp has an iron grip on the speaker -- is actually non-existant. Hence the need for a low system Q (impedance is flat at bass resonance -- or complementary to the bass roll0off). What a current amp does, is since the speaker isn't being asked to be a (poor) voltage-to-current converter, you loose the back EMF that the speaker feeds back to the amplifier. If we ignore that some amps actually become unstable from this feedbackm I see this back EMF as an overlaid signal component that cause an "infinite" regress time-smeared fog that decreases downward dynamic range.
If you haven't gotten ETM's book on the subject well worth a read... some tips in there on making spakers (typically dsigned for voltage drive) for current drive. Nelson's article also good. Have a look at Joe Rasmussen's latest speaker too. He uses an aperiodic TL to control the drivers resonant peak. The lower a driver's Qm the easier the task is.
With your Pensils you may find the need for more damping, maybe even worth getting a bale of Ultratouch, a very good damping material for this kind of thing. If you have the ability to measure impedance (most computer based measure systems), you ar looking to flatten the impedance curves, A rising impedance at the top end may have to be dealt with as well.
dave
Trick question? With no speaker connected you have no circuit and both current & voltage are zero.
dave
Forgive me if I'm wrong, but I think he wants to know what the amplifiers voltage is without a load. As in does the voltage drop when connected to a load. A before and after?
Dave, sorry, you are wrong - you still have circuit but with load that is infinitely large. Hint: open circuit for current source is like short circuit for voltage source, so think again. I must note that everything that I said before is based on my own thinkings as an electrical engineer. I didn't know about Nelson Pass experiment with current source amps so I read his "Current Source Amplifiers and Full Range Drivers" article and I'm glad that I can say that I WAS RIGHT.
In real world even voltage amplifier with lowest impedance could be considered as current source BUT ONLY FOR LOADS THAT ARE MUCH SMALLER THEN SOURCE IMPEDANCE. As speakers impedance varies from couple ohms to couple tens ohms such amp would act as constant voltage source for that load. But tube amps have higher impedance and Son of Zen even greater (16 ohms!). So SoZ could be considered as non-ideal voltage source OR non-ideal current source, basically it's the same thing.
Nelson: "Remember, you don’t have to own a current-source amplifier to put this information to work. Placing R0 in series with the output of a powerful voltage -source amplifier instead of in parallel with a current source will give similar results.".
As I stated before, speaker fed by current source amp would result in some kind of auto-tunning equalizer effect - gain at speaker resonance(s) and toward HF.
Nelson: "Driven by a current source, we note that the bottom end is bumped up at resonance and the top end is increased when compared to the performance of the voltage source...We can trim the damping "Q" of the low frequency roll-off knee by trying different values for R0 (L0 = 0 in this case) until it flattens out to our taste. Most of the drivers we worked with were happy with values from about 22 ohms to about 47 ohms...Usually we also want to adjust the upper midrange and high end. Often these drivers will exhibit an upper-mid peak followed by a decline before the upper-most treble is reached. We can compensate for this by our selection of R1, C1 and L1, which can be used either to create a shelf or a dip to flatten out the response."
Nelson didn't directly mention that gain is accomplished with higher power applied to speaker at resonant freq in opposite to voltage source and therefore higher cone displacement. That's why he insist for high-efficiency FR driver. With MA drivers that could be a problem. If there is too much gain for specific speaker/enclosure configuration he add R0 in parallel to current source amp - basically converting almost ideal current source toward non-ideal voltage source. Not necessarily but the problem could also be with any speaker alignment that has two resonant systems.
Also gain in HF could be bonus for FR drivers with early drop in HF extension but with FR drivers that already have good HF extension like MA drivers you should add R1,C1,L1 for compensation.
I think that current source amp idea has great potential but until speaker manufacturers start to adjust freq response for constant current source we are in muddy waters.
Mark, sorry for going off topic.
Maybe you should open new thread.I believe that the speaker using dynamic speaker amplifier should only be a voltage constant, but not current constant. Since the force of the coil depends on the current, in the extreme positions of the diffuser at a constant current strength decreases due to the decrease of the magnetic field, which leads to the growth of the third harmonic in the sound pressure. At a constant voltage reduction of the impedance in the extreme positions of the diffuser leads to an increase in the coil current, and accordingly to compensate for the reduction of force coil.
The negative output impedance equal to the resistance of the speaker wire gives an even better result.
best regards
Petr
The negative output impedance equal to the resistance of the speaker wire gives an even better result.
best regards
Petr
Mark, sorry for going off topic.
Hi Dj, Guys,
No problems, this is a separate thread so please feel free to continue debating. I'm busy most of the week so will snatch time to read the posts, as I'm reading the variety of thought with much interest
Thanks
Mark.
Speaker Driver Q and amp damping factor
Here's something that I thought was a rule of thumb with amp and speakers in layman's terms:
With a valve amp ideally, you would want speaker/drivers with low Q, like <0.3 (to compensate/offset lower damping of valve amp)
With S.S you might want speaker/drivers with higher Q: >0.3 because amp S.S generally provides more damping
What do people think about this? Reasonable/logical, True or False, over simplification, matter of personal taste/preference...comments?
Here's something that I thought was a rule of thumb with amp and speakers in layman's terms:
With a valve amp ideally, you would want speaker/drivers with low Q, like <0.3 (to compensate/offset lower damping of valve amp)
With S.S you might want speaker/drivers with higher Q: >0.3 because amp S.S generally provides more damping
What do people think about this? Reasonable/logical, True or False, over simplification, matter of personal taste/preference...comments?
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Hi Djanci, Guys,
Thanks for your input, but please show all members your sources to back up your claims.
Member Djanci's post 13 has referenced Nelson Pass, useful and informative, but please include the web-links to these sources, or state the publications from which they came. Give members the opportunity to read/check/interpret and evaluate references for themselves.
I'm all for debate but I'm not in favour of statements made to look "factual", or being argued on any authoritative basis, unless they come with a well researched credible references.
Anyone is welcome to offer their opinion/thinking and beliefs but if the debate moves to a "statement making phase", such comments that come without researched sources, will generally carry less credibility.
One of the best features of the Markaudio section on Diyaudio is that most contributors recognise the benefits to all when comments are technically accurate (much as possible) and easy for others to understand/follow. This way, everyone benefits in better knowledge sharing and we stay better protected from misleading information, trolling and similar.
Thanks
Mark.
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Hello Tim,
As interesting set of thoughts. They are an "over-simplification" but you've done the right thing by using the suggestions to encourage more thinking. Many thanks for doing this.
Cheers
Mark.
Ok, I don't mean to categorise/pigeonhole drivers by any singular specification; '0.3' is kind of just a general sort of arbitrary number to explain the idea.
For example; take a solo Mozart flute motif/phrase: the precise stop/start, the timing of the rhythmical punctuation of the flute notes express the 'musicality' of the phrase as much as the harmonic realism, clarity etc. So for me they're should be some tension, control/damping in the component and in between the components.
Just from my listening between S.S vs. valve amp. Just for myself - I love the 'sound' of valves, but prefer the 'feel' of S.S. This is the best way I can explain it. How does one explain/express this more technically? Is it in T/S parameters like 'Qts' and damping factor of an amp?
I guess the goal (for me) is to try to find a happy medium. I'm interested in defining/understanding the factors/parameters/measurements that determine the 'feel' of sound; numerical definitions for dynamic articulation, rhythmical punctuation - this is something I'd like to understand better. In context of dynamic/coil speakers.
For example; take a solo Mozart flute motif/phrase: the precise stop/start, the timing of the rhythmical punctuation of the flute notes express the 'musicality' of the phrase as much as the harmonic realism, clarity etc. So for me they're should be some tension, control/damping in the component and in between the components.
Just from my listening between S.S vs. valve amp. Just for myself - I love the 'sound' of valves, but prefer the 'feel' of S.S. This is the best way I can explain it. How does one explain/express this more technically? Is it in T/S parameters like 'Qts' and damping factor of an amp?
I guess the goal (for me) is to try to find a happy medium. I'm interested in defining/understanding the factors/parameters/measurements that determine the 'feel' of sound; numerical definitions for dynamic articulation, rhythmical punctuation - this is something I'd like to understand better. In context of dynamic/coil speakers.
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Here's another way of expressing it: Driver 'compliance' and mating a very compliant driver to a low damped amp. Is this generally, a good idea? Or a matter of taste? whether it sounds 'good'?
Or should there be a good balance between driver compliance and amp damping?
Is there a singular parameter that expresses driver compliance?
that feels better, got that off my chest. Thnx
Or should there be a good balance between driver compliance and amp damping?
Is there a singular parameter that expresses driver compliance?
that feels better, got that off my chest. Thnx
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