pwstereo Posted March 16, 2021 Share Posted March 16, 2021 Wikipedia uses the drive (not draw) terminology on the voice coil page. "By driving a current through the voice coil, a magnetic field is produced." Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 16, 2021 Share Posted March 16, 2021 (edited) 31 minutes ago, Ittaku said: On the surface this would appear to be good advice, but in my experience, the vast majority of speaker manufacturers "hide" just how hard their speakers are to drive properly. I was actually thinking of putting some sort of caveat. Yep. Quote On the contrary, I think this is very relevant to the topic that's why I put it there. Many have a significantly high output impedance (ie. are somewhat "current drive") and/or they also are often used clipping. Edited March 16, 2021 by davewantsmoore Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 16, 2021 Share Posted March 16, 2021 39 minutes ago, Steffen said: “Natural” was a word used in the linked article, I question it’s appropriateness in this context. Quote The speaker moves because of current flow. You can choose the current which is going to flow..... or you can choose the voltage, and let whatever current flow. Which one sounds more natural?! I don't. 39 minutes ago, Steffen said: By “easier” I meant the ability to either make a better sounding speaker at the same cost, or a same sounding speaker at a lower cost. There isn't going to be a general cost difference.... but there's a million ways to skin a cat. All else equal (when is it) ... it sounds better. 39 minutes ago, Steffen said: I think that’s a naive misrepresentation of physical reality. Voltage and current at a load are intrinsically linked. One isn’t better or more natural than the other. You need to think about the speaker some more. 39 minutes ago, Steffen said: On the contrary, P is all we’re interested in. P is (minus some thermal losses) the work that the membrane performs, pushing air around. It is (minus losses) the sound output of the speaker. No. Link to comment Share on other sites More sharing options...
Steffen Posted March 16, 2021 Share Posted March 16, 2021 3 hours ago, davewantsmoore said: No. Hm. 1 Link to comment Share on other sites More sharing options...
kukynas Posted March 16, 2021 Share Posted March 16, 2021 9 hours ago, aussievintage said: Doesn't help that they use the term 'VA' as unit for power that includes the non-real portion, and watts for real power especially when you are sourcing 65w r-core tranny and all you get back from the manufacturer is "we have only 65VA transformer sir" It seems last couple of hours were pretty busy during my nap time reading all the posts I first thought.... I have to open up my speaker cabinets and look for bunch of smurfs moving cones up and down, realizing my class D amplifier is basically a heater receiving unconsumed power from speaker and transforming it into heat and amplification of the music signal is just side effect, going back to school and apologize to all those who've been teaching me something about electronics.... most of it seems to be clear but not all, can anyone please point me into right direction about current driven amplifiers and speakers? honest question... as it seems I'm lacking a lot in this area thanks Dan 1 Link to comment Share on other sites More sharing options...
kukynas Posted March 16, 2021 Share Posted March 16, 2021 so I've used free services of Dr. Google and it seems there are current drive amplifiers called transconductors but most of the info is outdated nevertheless most talking about these amps in relation with fullrange drivers or horn speakers where flat FR and impedance curve is to be expected, in all modern "box" speakers voltage drive amplifier is preferred which would be in majority cases Am I correct in my readings? Never came across this before so... 1 Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 17, 2021 Share Posted March 17, 2021 (edited) 15 hours ago, Steffen said: Hm Yeah, I was in a rush... and I'm mindful that this is going miles of topic and down a deep rabbit hole. P is not the term of interest. I is the signal which moves the speaker. You are right that for a constant P, and a varying Z .... that I will vary (distort) ..... but P is not the signal. Current is. Current is held to the signal by the amplifiers feedback loop (irregardless of P, Z, V) .... ie. the current though the VC is undistorted vs the music signal. In the other scenario.... the current through the VC is distorted (by Z) vs the signal.... as the amplifier uses it's feedback loop to control V. Now.... I know what you are thinking. The cone movement is still distorted. Right. The cone still moves proportionally to the current though VC based on its efficiency (which you can see a representation of in Z). So Z still distorts it..... but the result is much less distortion. Essentially (without getting too far into it) the distortion signals in the speakers motion mix (intermodulate) with the wanted speaker motion dramatically less efficiently than the electrical signals mix with each other. It is tempting to use simple equations to say "it will be the same".... but observation shows it's not (distortion measurements). There are quite a few things out there comparing "voltage" and "current" drive which decide there isn't much difference (or not enough to be worried about) .... but they're all comparing THD and IMD off a low number of tones, (which doesn't represent real music, and) which doesn't allow the opportunity to see this intermodulation happen. Contrary to this being some esoteric thing ...... I think this issue is closer to the root cause of speaker sound, than not. If we look at the distortion in the impedance charts.... this isn't some nice "harmonic distortion". It is ugly.... it's probably as bad as a mildly clipping amplifier, and it's happening constantly, and rising with both the complexity and magnitude of the signal. I think it explains the root of why high efficiency speakers work better (many other common explanations can be "debunked") ..... and explains the conundrum around why zero feedback voltage amplifiers (remembering to correct the frequency response when comparing) can sound better.... and why w end up with two camps one who says "feedback sounds bad" ... and others who say "feedback is essential, say theory"...... it's that pure voltage sources (typically high feedback) sound bad. Anyways.... there's more depth to it for sure. Other aspects too (like V generated from the VC movement, aka "back EMF" products mixing into the voltage amplifiers feedback). Bruno holds the record (or so they say) for the making the amplifier with the lowest output impedance ever (ie. the most total voltage source) ...... but, when he made a speaker (the Kii Three) he took his amplifier and added current drive output stage to it.... and said: goes beyond merely a better amp – it actively improves the distortion performance of the drive units which contributes significantly to the extreme resolution of the speaker The Kii Three uses a woofer which cost less than a pint of beer in a fancy pub.... and a tweeter which costs less than the short taxi ride home. Edited March 17, 2021 by davewantsmoore Link to comment Share on other sites More sharing options...
DJGopal Posted March 17, 2021 Share Posted March 17, 2021 Why are people discussing volume? CONTROL is what's important here. Does the amp have enough current, damping factor and a fast enough slew rate to CONTROL the loudspeaker properly during impedance dips and dynamic peaks is the real question. I like to use the analogy of a weak person picking up a heavy weight, they might be able to pick it up, but they'll be shaking the whole time (distortion). A strong person on the other hand can pick it up easily and is also able to stop the lift at any desired point and hold it steady. (control) Arguing about decibels and watts is completely irrelevant to the issue. Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 17, 2021 Share Posted March 17, 2021 14 hours ago, kukynas said: most of it seems to be clear but not all, can anyone please point me into right direction about current driven amplifiers and speakers? honest question... as it seems I'm lacking a lot in this area It's difficult to do from behind a screen.... I like whiteboards and beverages. All speakers are "current driven".... in so far as they move when current flows..... power and voltage are not directly relevant. Some amplifiers turn the input signal into voltage, and control that voltage with feedback (which causes current to flow) ..... some make the input signal into current, and control that current with feedback. Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 17, 2021 Share Posted March 17, 2021 3 minutes ago, DJGopal said: Why are people discussing volume? CONTROL is what's important here. Does the amp have enough current, damping factor It is important that the amp can allow enough current (and disappear enough power) as clipping of this sounds bad. But.... damping factor (equated to control) is a myth. It is true that as the damping factor is lowered .... the speaker will play louder (move further) where it is more efficient..... and if this is not what you want then could be seen as "unwanted movement" and could be called "lack of control". However, it covers up what is really happening. At the end of the day, if you speaker is designed to expect a certain damping factor..... then you need to use that. Changing it will only lead to sound which is not what the designer intended. But.... with more degrees of freedom (ie. we design the speaker with a response we want, despite the low damping factor) .... and we compare (measure) the responses..... we see that the generalisation that "more damping factor controls the speaker better" is complete bunk. When we design two otherwise identical speaker (one with high DF and one with low DF) to have identical response...... we can see that their large signal cone movement is identical (which it has to be if they have the same response). When we look deeper, we see: Small signal non-linearities favour the lower damping factor (there is less distortion) When the signal is stopped, and "the cone keeps on moving on it's own"..... we see: a) People have dramatically overstated how much this happens ..... it's not significant under any circumstance b) High DF speaker return to rest quite violently, often with accompanying distortion..... it's arguable that high DF is better in many situations, if not most. (which is it's "claim to fame"). 3 minutes ago, DJGopal said: I like to use the analogy of a weak person picking up a heavy weight, they might be able to pick it up, but they'll be shaking the whole time (distortion). A strong person on the other hand can pick it up easily and is also able to stop the lift at any desired point and hold it steady. (control) If you are talking about clipping.... the yes. Clipping is bad sounding distortion. If you're talking about "damping factor".... No. 3 minutes ago, DJGopal said: Arguing about decibels and watts is completely irrelevant to the issue. Not necessarily. It come up because primarily you want to avoid clipping..... and if you want to predict that, then they're relevant. 1 Link to comment Share on other sites More sharing options...
Steffen Posted March 17, 2021 Share Posted March 17, 2021 1 minute ago, davewantsmoore said: Some amplifiers turn the input signal into voltage, and control that voltage with feedback (which causes current to flow) ..... some make the input signal into current, and control that current with feedback. I think you mean, almost all amplifiers turn the signal into voltage, and very few (typically inside active speakers) turn it into current? But thinking on from what you said earlier... Virtually all speaker drivers I looked up the specs for had: a more or less flat frequency response to a constant voltage input (measured at low level, i.e. small coil excursion) a rollercoaster impedance curve Now, if we posit (as you do) that the speaker driver will behave differently (distort more) at high input levels, due to its changed impedance at large coil excursions, and that we should feed a constant current instead, then this means: the current delivering amplifier needs to “know” the small-signal impedance curve of the driver, and correct for it, so that at small input levels the resulting voltage over the driver is constant across the frequency range (because we know that gives us a flat frequency response) at high input levels, the current delivering amplifier would then apply the same impedance curve, resulting in a somewhat different voltage over the driver across the frequency range, because the impedance and therefore the voltage drop changes at high excursion This would imply that current amps and speaker drivers need to be matched, and that this is only practical with active speakers, correct? Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 17, 2021 Share Posted March 17, 2021 37 minutes ago, Steffen said: I think you mean, almost all amplifiers turn the signal into voltage, and very few (typically inside active speakers) turn it into current? Yes..... since most amplifier and speakers are designed without reference to eact other.... then that's what happens. Some type of tube amps (specially "older" designs) tend towards current... and a few people make solid state ones too. Lots of DAC chips output a current signal, and the box contains an I to V amplifier. 37 minutes ago, Steffen said: But thinking on from what you said earlier... Virtually all speaker drivers I looked up the specs for had: a more or less flat frequency response to a constant voltage input (measured at low level, i.e. small coil excursion) a rollercoaster impedance curve Random woofer. https://www.daytonaudio.com/images/resources/295-432--dayton-audio-ds270-8-specifications.pdf If you convolve the SPL with the Z .... that it makes flatter (in the big picture sense anyways .... this one has some misbehaviour between 1 and 3khz which obscures that) 37 minutes ago, Steffen said: the current delivering amplifier needs to “know” the small-signal impedance curve of the driver, and correct for it, so that at small input levels the resulting voltage over the driver is constant across the frequency range (because we know that gives us a flat frequency response) 37 minutes ago, Steffen said: at high input levels, the current delivering amplifier would then apply the same impedance curve, resulting in a somewhat different voltage over the driver across the frequency range, because the impedance and therefore the voltage drop changes at high excursion The fact that the impedance is unstable vs excursion is an issue for both I and V drive ..... just the results are worse for V. Link to comment Share on other sites More sharing options...
kukynas Posted March 17, 2021 Share Posted March 17, 2021 10 hours ago, davewantsmoore said: All speakers are "current driven".... in so far as they move when current flows..... power and voltage are not directly relevant. I've already asked my Doco to prescribe a stronger model as my current one can't handle this 10 hours ago, davewantsmoore said: It's difficult to do from behind a screen.... I like whiteboards and beverages. yes me too otherwise I get your point and example with Kii 3 Link to comment Share on other sites More sharing options...
davewantsmoore Posted March 17, 2021 Share Posted March 17, 2021 13 hours ago, kukynas said: otherwise I get your point and example with Kii 3 It would seem really arrogant of me if I said 99% of what you will read in mainstream modern commentary on this subject... even from a lot of "industry leaders" who should really really know better..... are somewhere between "twisting the truth" and "I have no idea what I'm talking about". Whoops... .did I just say that? ..... 1 Link to comment Share on other sites More sharing options...
Addicted to music Posted April 4, 2021 Share Posted April 4, 2021 @andyr. @Telecine @kukynas The Sanders Magtech has 10pairs of devices, all BJT per channel. This is where you can tell how capable a amplifier is when it comes to current delivery. When @sir sanders zingmore brought it around to my place and we compared mostly class D, a 100W MF integrated and my 240W @ 8 ohms Mosfet. The Magtech raised the bar and in a league of its own. No disputing it, no need for a DBT . Everyone in that room heard it! 2 Link to comment Share on other sites More sharing options...
Addicted to music Posted April 4, 2021 Share Posted April 4, 2021 Just now, Addicted to music said: @andyr. @Telecine @kukynas The Sanders Magtech has 10pairs of devices, all BJT per channel. This is where you can tell how capable a amplifier is when it comes to current delivery. When @sir sanders zingmore brought it around to my place and we compared mostly class D, a 100W MF integrated and my 240W @ 8 ohms Mosfet. The Magtech raised the bar and in a league of its own. No disputing it, no need for a DBT . Everyone in that room heard it! edited: these pics are modules I gain when I help a member here to replaced. Roger Sanders send this member 2 amplifier pcb and 8x 8200uf for replacement free of charge! I just got on board to replaced them... Also a very easy amp to service. Link to comment Share on other sites More sharing options...
andyr Posted April 4, 2021 Share Posted April 4, 2021 37 minutes ago, Addicted to music said: @andyr. @Telecine @kukynas The Sanders Magtech has 10pairs of devices, all BJT per channel. This is where you can tell how capable a amplifier is when it comes to current delivery. When @sir sanders zingmore brought it around to my place and we compared mostly class D, a 100W MF integrated and my 240W @ 8 ohms Mosfet. The Magtech raised the bar and in a league of its own. No disputing it, no need for a DBT . Everyone in that room heard it! Whilst I believe you, Peter I'm just gonna note that there are a number of folk here who will say ... "no DBT ... no believey "! Andy Link to comment Share on other sites More sharing options...
kukynas Posted April 4, 2021 Share Posted April 4, 2021 7 hours ago, Addicted to music said: @andyr. @Telecine @kukynas The Sanders Magtech has 10pairs of devices, all BJT per channel. This is where you can tell how capable a amplifier is when it comes to current delivery. When @sir sanders zingmore brought it around to my place and we compared mostly class D, a 100W MF integrated and my 240W @ 8 ohms Mosfet. The Magtech raised the bar and in a league of its own. No disputing it, no need for a DBT . Everyone in that room heard it! don't know why but my OCD's telling me that there's something's wrong with that blue trimmer , anyway, no wonder, it's hard to beat that amount of power transistors 1 Link to comment Share on other sites More sharing options...
Addicted to music Posted April 4, 2021 Share Posted April 4, 2021 (edited) 1 hour ago, kukynas said: don't know why but my OCD's telling me that there's something's wrong with that blue trimmer , anyway, no wonder, it's hard to beat that amount of power transistors Both those are the ones Roger asked to have replaced so these are just spares. He sent 2 brand new amp modules and told us “do not touch the pots “ . So I’m guessing the bias has already been set up. On switch on and after a 30mins of driving, I still get zero DC out.... so that’s a good thing! Also the heatsink to both stayed the same temp! Unlike b4. Edited: that blue trimmer is possibly the result of me transporting it, me bad! Edited April 4, 2021 by Addicted to music Link to comment Share on other sites More sharing options...
Addicted to music Posted April 4, 2021 Share Posted April 4, 2021 @kukynas Instead of me quoting it, a picture is worth a thousand works and it’s more accurate i though I post a closer pics of the Onsemi Devices. Note there is also a pair of Thermaltrak of these in use, the selling pitch is that they actively monitor the die via a thermal diode, so they are 5 pin devices.... that said I’ve known that there were some bad batches that gave wrong values, hence the reason it possible cause some modules to overheat which is what the complaint was that the Roger wanted just to replaced the whole lot! 1 Link to comment Share on other sites More sharing options...
kukynas Posted April 4, 2021 Share Posted April 4, 2021 4 hours ago, Addicted to music said: Edited: that blue trimmer is possibly the result of me transporting it, me bad! bit of soldering and it’s back on track 1 Link to comment Share on other sites More sharing options...
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