Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > I don't know how well the Logos amp was designed. I see that there is > evidence on the web that it incorporates a false claim in its > advertising claims, that its 8 ohm power doubles into 4 ohms; > > http://www.soundstagenetwork.com/index.php?option=com_content=article=1347:bhk-labs-measurements-pathos-acoustics-logos-mkii-integrated-amplifier=97:amplifier-measurements=154 > > " > Power output > > Output power at 1% THD+N: 155.0W @ 8 ohms, 237.4W @ 4 ohms (4 ohms > power = 142% of 8 ohm power) > " > > In fact its actual 4 ohms performance is about 40% more more than its 8 > ohm power, which is fairly typical for power amps, even some fairly > inexpensive ones. I expect in our commercial world, there's a lot of this kind of marketing hype about, sadly! What did you make of their "valves are better for voltage amplification, solid-state devices are better for current amplification" statement? It seems a bit too simple to be taken at face value to me. Having said that, they do stick the same twin triodes in the analogue stage of their Digit CD player (& used valves in the expensive & now discontinued Endorphin CD player which has to be a candidate for the sexiest looking CD player of all time). As far as the Logos itself is concerned, it's very well built & has more power than I need. I think the implementation of the Class A/B design is the most important aspect - it sounds good to me, don't know if anyone has investigated its transfer characteristics. Had it seven years plus now, it could be eleven years from new. Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Julf wrote: > Unless the filter was very steep, it would not do much good - it would > either affect frequencies well above 30 Hz, or mostly affect frequencies > where there isn't much signal in your average recording. Making a very > steep passive filter is very tricky, and you would probably end up > burning the same amount of power anyway, just that it would heat the > filter instead of the speaker voice coil. Hi Julf! I take your point about the difficulty of designing an effective passive filter to do the job. Obviously it would still be better to disperse surplus heat in a filter component intended for the purpose than to overheat your speaker voice coil. Neither my amplifier nor my speakers have shown any distress so far so hopefully I've got both sufficient clean power & resilient enough voice coils for it not to a concern in practice. Will sleep better now, thanks! Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > Passive speakers generally do not have any electrical high pass filters, > but most active speakers do. > > The reason why is as given above - below their low frequency limit most > speakers are quite willing to absorb power, but generally produce very > little acoustical output and/or mostly distortion. Thanks for prompt response. I suppose the massive magnets affixed to the drivers in close proximity to the voice coil, plus the fact that there will usually be cone motion induced by simultaneous higher frequencies in actual programme material creating a bit of a draught in the vicinity means that overheating is unlikely in practice. It's interesting that B do not recommend plugging the 805S ports with (the already supplied) foam bungs, which would reduce distortion at the expense of further LF loss when connecting the subwoofers. I suppose the subwoofers are best tuned to handle the really low stuff, and the imaging might suffer if the LF performance of the stand-mounts is further reduced. They probably include the bungs for situations where the LF content of the programme material itself is low, so that you can get less distortion (by avoiding the vagaries of the reflex reinforcement) on that sort of music. I haven't noticed any objectionable artifacts yet despite listening to all sorts of music however & I prefer not to fiddle about unnecessarily, so I'll leave the bungs languishing in the back of my cupboard. Having 4 stiff 8" long-throw cones in 2 opposed pairs does enable me to shove quite a lot of air in my room, & having the 2nd subwoofer has made the location of (either of them) much less critical. Can't detect the stereo soundstage of course, just reduces modal reinforcement in my room. Surprisingly musical sounding very low bass this way... Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > If you depart too far from the ideal in the direction of Class A you > have a problem with what is called gm doubling. This is a fairly deep > technical issue further elaborated on by Douglas Self in his various > well-known publications related to power amp design and also > 'Douglas-sel on SS power amps,' > (http://douglas-self.com/ampins/dipa/dipa.htm#5) as well as 'Solid State > amplifiers by teemu_kyttala_v1.0.pdf' > (http://www.thatraymond.com/downloads/solidstate_guitar_amplifiers_teemu_kyttala_v1.0.pdf). Hi Arny! Most impressed by the two references you have kindly provided, although they're going to take me some time to digest: Douglas Self is clearly summarising about half a lifetime's work, & the distortion figures his amplifier designs measure at are astonishing. I wonder how long we will have to wait for similarly impressive loudspeaker performance, & ultimately whether our ears are up to the task of discerning how clean they are. The second article is very wide-ranging & all the more impressive for having been written in a language other than the author's native tongue. It's very useful stuff & may well come in handy for all kinds of future purposes. Bedtime reading for a while! Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Golden Earring wrote: > > > What interests me however is what happens from the power amplifier's > perspective when a stand-mount receives signals at frequencies below its > LF roll off point, where air resistance within the cabinet is > mechanically reducing or preventing the motion of the LF driver. I > wondered at first whether this effect might in some way cause the > speaker impedance to rise for frequencies significantly below its LF > roll-off point, and spent some time scouring the internet for a > published impedance vs. frequency chart for my 805S's. I did finally > find one, although it had not been produced by B themselves, which > seemed to indicate that impedance did initially rise in the LF region, > especially in the reflex reinforcement range, but then seemed to fall > again so that for frequencies which would be audible to the ear but > which my stand-mounts would struggle to emit even faintly, it was back > around the nominal 8 Ohm mark or lower. > > This seems to me to imply that the speaker must still be drawing > significant power from the amplifier for such very low frequencies, > although it is producing little or no audible output. I can only assume > that this power must be dissipated by heating up the voice-coil of the > driver which cannot respond mechanically to such signals. This seems an > unsatisfactory situation which might in extreme cases cause damage to > the driver even though the signal was clean & not clipped. > > The extended LF response is certainly there at the power amplifier > output posts - that is precisely what provides the signal for my active > subwoofers. These have an input impedance of 10KOhm however, so draw no > power to speak of at all, which is why their addition has no effect > whatsoever on the performance of the stand-mount speakers. > > If this is true, why do stand-mount loudspeakers not include a steep > high-pass filter at 30Hz or so, to divert this power from the drivers > unable to turn it into sound, and presumably simultaneously reduce the > load on the power amplifier by increasing the impedance it is loaded > with below that frequency point? > Passive speakers generally do not have any electrical high pass filters, but most active speakers do. The reason why is as given above - below their low frequency limit most speakers are quite willing to absorb power, but generally produce very little acoustical output and/or mostly distortion. arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Golden Earring wrote: > If this is true, why do stand-mount loudspeakers not include a steep > high-pass filter at 30Hz or so, to divert this power from the drivers > unable to turn it into sound, and presumably simultaneously reduce the > load on the power amplifier by increasing the impedance it is loaded > with below that frequency point? Unless the filter was very steep, it would not do much good - it would either affect frequencies well above 30 Hz, or mostly affect frequencies where there isn't much signal in your average recording. Making a very steep passive filter is very tricky, and you would probably end up burning the same amount of power anyway, just that it would heat the filter instead of the speaker voice coil. "To try to judge the real from the false will always be hard. In this fast-growing art of 'high fidelity' the quackery will bear a solid gilt edge that will fool many people" - Paul W Klipsch, 1953 Julf's Profile: http://forums.slimdevices.com/member.php?userid=42050 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Hi all! Since it's all gone slightly quiet, I thought that I would ask the forum about an issue to which I do not know the answer. I'm thinking here of the contrast between my current 2-way B 805S speakers which are a ported design with a carefully shaped cabinet (which in fact has no parallel sides), a single mid-bass driver only 6.5" in diameter (although having a Kevlar composite cone to minimise cone break-up), a completely separate aluminium dome tweeter located on top of the main cabinet, and is claimed to have a very simple passive crossover circuit which has a high nominal crossover frequency of 4kHz and a pair of Spendor BC3 loudspeakers I owned back in the 70's, these were massive rectangular boxes of a 4-way design, comprising a 12" woofer, an 8" mid-range driver, a tweeter AND a super-tweeter above that. Despite the size of the these speakers the 12" driver was loaded in a reflex arrangement with 2 forward facing rectangular ports; the 8" driver had its own sealed enclosure concealed within the main cabinet; but most significantly the whole arrangement was controlled by a literally massive full 4-way, half-section passive crossover which had inductors the size of small transformers. As a consequence they represented a very difficult load with volatile & often reactive element dominated impedance. There were too many individual sound-sources to integrate easily within one loudspeaker and some problems with phase aspects around the 3 separate crossover points which if I recall correctly were 800Hz, 3000Hz & 12000Hz. Ok, there's the trade-off, agile & well-imaging stand-mounts but with limited LF vs. more complex (usually, not always) floor-standers with more extended LF & probably higher power capacity but often with larger, less agile woofers and inferior soundstage presentation. Off-axis response is also usually easier to control with a simpler design. However the most obvious reason to go for stand-mounts remains that they tend to work better than larger boxes in small rooms & are usually much less fussy about speaker positioning. This much I think I understand, but please feel free to comment or correct me if you disagree with anything I have suggested above. I would obviously accept that a poor implementation will remove the potential benefits of any given loudspeaker's basic layout. What interests me however is what happens from the power amplifier's perspective when a stand-mount receives signals at frequencies below its LF roll off point, where air resistance within the cabinet is mechanically reducing or preventing the motion of the LF driver. I wondered at first whether this effect might in some way cause the speaker impedance to rise for frequencies significantly below its LF roll-off point, and spent some time scouring the internet for a published impedance vs. frequency chart for my 805S's. I did finally find one, although it had not been produced by B themselves, which seemed to indicate that impedance did initially rise in the LF region, especially in the reflex reinforcement range, but then seemed to fall again so that for frequencies which would be audible to the ear but which my stand-mounts would struggle to emit even faintly, it was back around the nominal 8 Ohm mark or lower. This seems to me to imply that the speaker must still be drawing significant power from the amplifier for such very low frequencies, although it is producing little or no audible output. I can only assume that this power must be dissipated by heating up the voice-coil of the driver which cannot respond mechanically to such signals. This seems an unsatisfactory situation which might in extreme cases cause damage to the driver even though the signal was clean & not clipped. The extended LF response is certainly there at the power amplifier output posts - that is precisely what provides the signal for my active subwoofers. These have an input impedance of 10KOhm however, so draw no power to speak of at all, which is why their addition has no effect whatsoever on the performance of the stand-mount speakers. If this is true, why do stand-mount loudspeakers not include a steep high-pass filter at 30Hz or so, to divert this power from the drivers unable to turn it into sound, and presumably simultaneously reduce the load on the power amplifier by increasing the impedance it is loaded with below that frequency point? Have I missed something here? Dave (puzzled) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > Knowing when to be loud and when to be quiet was a survival skill in > those days. My children learned some things about that in modern times, > if you catch my drift! ;-) I hear you... :) "To try to judge the real from the false will always be hard. In this fast-growing art of 'high fidelity' the quackery will bear a solid gilt edge that will fool many people" - Paul W Klipsch, 1953 Julf's Profile: http://forums.slimdevices.com/member.php?userid=42050 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Julf wrote: > It is of course a gross simplification. Evolution has operated to ensure > human survival and reproduction. Whatever specific forms it takes is > harder to figure out. > > > > Do children make a lot of noise when they get scared? Perhaps they > mostly make a lot of noise when they want the attention of their parents > (as when they get lost/separated from their parents), and that has > proven to be a more sustainable trait? Knowing when to be loud and when to be quiet was a survival skill in those days. My children learned some things about that in modern times, if you catch my drift! ;-) arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Golden Earring wrote: > Hi Arny! > > Thank you for your clear response. > > I'm probably best off with my Class A/B Logos which at least sounds as > if it's done well, and save money by avoiding the pure Class A Inpol 2. > > I suspect you've just saved me from falling for an expensive > "down-grade"! > > Dave :) I don't know how well the Logos amp was designed. I see that there is evidence on the web that it incorporates a false claim in its advertising claims, that its 8 ohm power doubles into 4 ohms; http://www.soundstagenetwork.com/index.php?option=com_content=article=1347:bhk-labs-measurements-pathos-acoustics-logos-mkii-integrated-amplifier=97:amplifier-measurements=154 " Power output Output power at 1% THD+N: 155.0W @ 8 ohms, 237.4W @ 4 ohms (4 ohms power = 142% of 8 ohm power) " In fact its actual 4 ohms performance is about 40% more more than its 8 ohm power, which is fairly typical for power amps, even some fairly inexpensive ones. For example: https://www.soundandvision.com/content/denon-avr-x4200w-av-receiver-review-test-bench Denon AVR-X4200W A/V Receiver Review Test Bench " 0.1% THD Two Channels Continuously Driven, 8-Ohm Loads 124.3 watts Two Channels Continuously Driven, 4-Ohm Loads 215.9 watts " 4 ohm power is 73% more than its 8 ohm power which is actually very good. arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
cliveb wrote: > People are always banging on about how evolution has operated to protect > humans from predators, but it has always struck me as a somewhat lazy > assumption. It is of course a gross simplification. Evolution has operated to ensure human survival and reproduction. Whatever specific forms it takes is harder to figure out. > If avoiding bloodthirsty predators was so important to the survival of > the human race, why hasn't natural selection eliminated the gene(s) that > cause children to make a lot of noise? :) Do children make a lot of noise when they get scared? Perhaps they mostly make a lot of noise when they want the attention of their parents (as when they get lost/separated from their parents), and that has proven to be a more sustainable trait? "To try to judge the real from the false will always be hard. In this fast-growing art of 'high fidelity' the quackery will bear a solid gilt edge that will fool many people" - Paul W Klipsch, 1953 Julf's Profile: http://forums.slimdevices.com/member.php?userid=42050 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > Our hearing systems have evolved to maximize sensitivity to potential > existential threats such as large bloodthirsty predators... People are always banging on about how evolution has operated to protect humans from predators, but it has always struck me as a somewhat lazy assumption. If avoiding bloodthirsty predators was so important to the survival of the human race, why hasn't natural selection eliminated the gene(s) that cause children to make a lot of noise? :) Transporter -> ATC SCM100A cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
