FritzS
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Post by FritzS on Dec 26, 2011 6:12:45 GMT
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Post by Deleted on Dec 26, 2011 6:30:38 GMT
Friedrich We have been through this before with you.. The majority viewpoint of RG members is that the K701 sounds far more balanced when fed from a 120 ohm source impedance.Frans and Ian agree too. The K701 sounds quite fatigueing when driven from a low impedance.Graham $lee even rolled off HF in some of his amplifiers to prevent users of the K701 blaming his amplifiers. Perhaps AKG sources that you keep quoting listen with their instruments instead of their ears ? They also claim that the K701 does NOT improve after a considerable "burn in" period. That is also contrary to reports from the vast majority of members who own them. Alex
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Post by Deleted on Dec 26, 2011 8:34:01 GMT
Those articles were written AFTER NwAvGuy (my evil twin) had contacted Tyll and preached his gospel (the O2 and it being all you need). If Tyll would have wanted to show IF damping factor is that important he should have run a second test where he upped the output resistance of his test amp from 2 Ohm to 16 Ohm for the 250 Ohm HP and to 38 Ohm for the 600 Ohm version. IF they measured the same / sounded similar with this simple test he would have shown the damping factor is of importance. Now all he has shown is the headphones behave sound different on the same amp. This was already known.
The WEIGHT of the membrane, and thus the way the the membrane swings out after a pulse, in headphone drivers is for a substantial part determined by the weight of the voicecoil and also by the weight of the membrane. 600 Ohm doesn't need much CURRENT when the same POWER is applied as in a 32 Ohm driver (in the latter flows more CURRENT). More current needs THICKER (read heavier) wires when the same POWER (reached SPL) is applied. Hence the 600 Ohm version has THINNER wiring and thus also the total weight of the moving part is different (lower). Because of this fact the lighter membrane is quicker and more easily 'halted' after a pulse (music signal) is applied. THIS different in weight causes the 32 Ohm to 'swing out' more than 250 and 600 Ohm. And yes, with a higher output resistance of the amp this doesn't get better as well and CAN affect sound reproduction in a negative way with CERTAIN headphones.
Why choose 32 or 250 or even 600 Ohm ? For portable use (even with low voltage portable amps) when you need max SPL choose 32 Ohm For hifi and studio business (read more of these in parallel) choose higher Ohmics. The condition is the output VOLTAGE swing (not output POWER) needs to be higher and thus not suited for portable use IF you want to reach max SPL.
For AKG there is little to choose in impedance for the K701.
I have found (with my ears) that K701, HD580, HD280, HD661 fare better on higher output resistances. (HD800 and T1 IMO also benefit) HD650, older DT990 and some low Ohmic headphones (modded HD681) sound better on low Ohmic (as will all armature drivers) amplifiers.
The reason most amps have a certain output resistance is to make them more compatible for different impedant headphones so the powers on low Ohmic headphones don't exceed the maximum ratings too much. It is a CHEAP way of current limiting. This resistance is ALSO determining the amplifiers 'sound' amongst other factors so an amp can 'stand out'.
It's your EARS that have to decide as well as the capabilities of the amplifier and properties of the headphone that should decide if you need a certain output resistance. I certainly do not like to listen to an K701 or HD280 on low Ohmic amplifiers.
By the way... AKG may tell you their headphones have to be driven by LOW Ohmic amplifiers, but most listeners report other findings. Tyll's article 'shows' how Beyerdynamic headphones need to be driven from low Ohmic headphones. Please ask them why their A1 has a 100 Ohm output resistance. -Output impedances: ……………………….100 Ω headphone output, (taken from their own datasheet)
I want to have a choice myself... hence all my designs have at least 2 different output resistances. Don't want to be limited to just ONE output resistance determined by a manufacturer.
Another way to have a choice between output resistances is to buy 2 amps (each having a different output resistance) and you will find some headphones 'synergize' better (sound more pleasant) with certain amps.
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elysion
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Post by elysion on Dec 26, 2011 9:10:33 GMT
Isn't the A1 a Beyerdynamic amp? It's a bit senseless to ask AKG about a Beyer amp.
Otherwise, I fully agree. I have a few amps with low output impedance and they sound NOT good with the K702. So far, my X-Can V3 with Little Pinkie SE is still the best option for my K702's, but its output impedance (85 Ohm IIRC) is still a compromise.
If I have problems with headphones, it's always the treble: K702, HD681, SR850, HD-560 OvII
Luckily, there are also a lot of headphones that behave almost always nice to my ears: DT 990 Pro, DT 770 Pro, HD-580, HD-650, HD25-1/II
I'd like to have more choices for the output impedance, but probably this will have to wait until I have enough time to search for an appropriate workshop and use the soldering equipment which I've bought this year. It will be interesting if I have a chance to cure the treble of the 'phones mentioned above. I'm in doubt that I will find a cure for some 'phones, especially the HD-560 OvII's are painful for my ears.
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Post by Deleted on Dec 26, 2011 9:18:29 GMT
yep... AKG is not Beyer. That's what you get when you keep editing posts. I originally made the remark because of the the beyerdynamics that were 'tested' in Tyll's article. oops... corrected. HD681 treble cannot be cured by increasing output resistance. the bass will get more pronounced/muddier on higher output resistances and the decrease in treble is not in the desired levels/range.
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rowuk
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Post by rowuk on Dec 26, 2011 9:34:29 GMT
Raising the impedance of the amp also changes the frequency response. The output stage feeds a resistor (in the amp) and a coil creating a RL circuit. With boutique cables, mentionable capacitance also leaks into the equation.
It has been known for a long time in the speaker world that you have to calculate the low frequency box parameters while considering the resistance of the speaker cable.
My personal opinion is that the resistor belongs in the PHONES not the amp. Every switch that the amp doesn't need improves the long-term stability. My 701s currently have 2 120 ohm resistors soldered in the jack.
That all being said, the mod that offered the most for the 701 was making the ear cushions about 1cm thinner. The bass response now matches the rest of the presentation. Acoustical, musical instruments give me a similar impression to what I hear on stage.
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Post by Deleted on Dec 26, 2011 9:48:52 GMT
If you include the resistor in the headphones you 'double' the resistance in case an amp is used that by itself also has an output resistance.
The A1 + AKG with resistors will be fed with 220 Ohm effectively. Also the K701 will play considerable softer (voltage devision) on portable gear and won't reach higher SPL's.
Indeed the frequency response is altered depending on the impedance of the headphone and output resistance. This may be a good/needed thing with certain headphones and may alter other headphones in a negative way.
most headphone cables are about 100pF/m even with 1nF/m and a 120 Ohm output resistor and 3m of cable the high cut-off point (-3dB) is still 440 kHz ! Low Ohmic amps MAY get in trouble with high capacitances AND when high impedance headphones are used. Ringing/oscilations (well above the audible range) may occur and COULD lead to degraded sound. That's why balanced armature drivers should not be driven from higher Ohmic amps.
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FritzS
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Post by FritzS on Dec 26, 2011 10:10:10 GMT
@sandyk
My experience with K701/K702/Q701 the most variances are in the first 20 hours, less till 100 hours, after this time, very less, so I could not reprudece them to 100%.
@solderdude
I read with concern about NwAvGuy's O2 and his philosphy - O2 is for my not basically different as C.H.AMP (I mean only the amp part), but NwAvGuy use only slow slew rate (and old types) OPA's and C.H.AMP use mid and high slew rate OPA's. (Please correct me if I dont right).
A little mistake AKG makes the headphones K701/K702/Q701
Beyer (Beyerdynamic) makes T1, DT 880 headphones (600 Ohm) and A1 (the amp for it).
But this output impedance could be that my WNA MKII sounds a little bit darker than Solo WNA MKII have 15 Ohm, Solo have 33 Ohm Impedance - Solo have a little bit better resolution.
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Post by Deleted on Dec 26, 2011 10:27:50 GMT
According to AKG there is NO burn in time.
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Post by Deleted on Dec 26, 2011 10:59:53 GMT
Don't AKG also state that they work well from low output impedance amps? What I find slightly strange about Mr Wavy Guy (Voldemort - the evil twin as opposed to our good fairy ) almost has a black and white view and then states how correct his view was with subjective. I like how he writes descriptions about how things work. Very good for people who'd like to know about the technicalities but it does seem stark black and white to me. Technically fascinating stuff but that doesn't make for real music in real headphones all of the time. Frans mentioned the thickness of material used in diaphragms and although measurements may come out nice on some thicknesses, the density of material and flexibility (damping) will all contribute to create a different sounding headphone. ie; lots of things need to be considered in measuring the gear and testers need to be sure that they are measuring the right things because it's not what they measure that I have a problem with - it's more perhaps what they've not measured and maybe missed something. It's a very complex process. I believe that our own good fairy considers these things in a more 'colourful' way than Mr Wavy and is more open to possibilities. I like the simplified descriptions that Wavy does though. Very clear. It seems that he is unaware of the differences in sound on the K701 with a different output impedance. (Perhaps he can't hear them) Frans' CH.AMP seems a really good compromise and really is an amp that can be altered to your own preferences, whether technically correct or not. I really like that idea. In the real world of audio, there are so many variables to contend with and having a subtle (if you like) tone control via output impedance for some of those 'jarring' recordings is a nice idea. So far, for my ears, the K701 needs an extremely powerful amp with 120 out before it even thinks about singing. Otherwise, it keeps trying to screech. However, many hi fi orientated people seem to think that screeches constitute hi fi.
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Post by Deleted on Dec 26, 2011 14:39:06 GMT
That mistake was caused by partial deleting/editing original writings. Already corrected (read the line again).
The ONLY thing the O2 and CHAmp have in common are both amps use opamps. That's about it. The CHAmp existed before the O2 came.
Power supply, power supply voltage, output powers, portable vs desktop, safety measures/features, ways of current limiting, position of volpot, used opamps, topology, bandwidth, output resistances, board layout all differ considerably. Of course NwAvGuy says the CHAmp is NOT a good design at all and showed poor design practices. Only his and the Benchmark, and now Tyll's stuff) is any good. I will say: there is little wrong with the O2 and will be a good sport. IMO there isn't much wrong with many designs b.t.w.
You will have to understand that even IF NwAvGuy now finds some headphones DO sound better on high-Ohmic amps he cannot possibly come back on his previous statements. I have the luxury of being 'independent' and may change my mind/views.
In the end it's not my or anyone else's theories that counts but your ears/preference/equipment/music that should be the decisive factor if something is 'good' or not. regardless if it is technically correct or found to be such by others.
So IF you prefer the K701/702/Q701 with low Ohmic amps then this is the right choice for you. If someone else preferes it with 120 Ohm then this is best for him/her.
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FritzS
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Post by FritzS on Dec 26, 2011 16:02:26 GMT
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Post by Deleted on Dec 26, 2011 20:08:52 GMT
I suspect more amps use the LM6171/2 as it is a good and very fast opamp but needs some serious PCB layout/decoupling to perform well. If used in a C'Moy they can give trouble. Meiers designs are good designs IMO, as are many other amps. There is not much in common with Meier's amps when looking at the schematics in-depth, except it uses 2 opamps and we are both Dutch . The opamps are only offset 2mA per opamp (to one side and half of them to the other side) so there is no class A nor anywhere near it. With an 8 Ohm load and all 44 opamps in parallel it is only 0.007W in class A. Most class AB amplifiers have an idle current of 50mA, the Meier power amp has 44mA so more class AB than nearing class-A in any case (nice gimmick though and a fine sales arguement) Of course it's just a claim, and every opamp (C'moy) in the world can have a 2k connected between the output and 1 power pin. In the headwize project the offset current is 10mA so it stops being in 'class-A' at 1.6 mW with a 32 Ohm headphone. If the resistor wasn't there it would not be in class-A at around 0.02mW. It's just numbers but the 'nearing class-A' claim is a bit OTT. As claimed in my article the CHAmp isn't a better amp nor worse than other designs. I only mentioned it for the output resistance thing, but all my designs (including the Sunrise) have this 'feature'. have been doing this for about 30 years now (having high and low output resistances to choose from). At that time I had also build an all opamp power-amp, long before Meier's poweramp design existed. There's pictures and a story on it in RG somewhere (can't find it that fast). We are getting off topic though. essence is some HP's sound better to some with a higher output resistance, some headphones (may even be the same ones) may sound better to someone else from lower Ohmic amps. There is no absolute right or wrong and for both cases there are pro's and con's, it is just opinions and personal preference that should be the dicisive factor not the theories behind it.
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Post by PinkFloyd on Dec 26, 2011 21:20:52 GMT
Dr. David White and I always preferred the LM6171 for the sheer "speed" but, yes, the circuit has to be built around them.... they are certainly not "roll in" type opamps (unless you like motorboating and oscillations).... great opamps if implemented correctly though.
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Post by Deleted on Dec 26, 2011 21:38:04 GMT
Yes, and it seems better explained, and even corrects these misapprehensions about headphone driving impedances. A very nicely presented, and informative report Frans. Regards Alex
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Post by dalethorn on Jan 25, 2012 3:39:00 GMT
According to AKG there is NO burn in time. Is there any chance it's because AKG is pre-burning them? I asked the question 3 times at Innerfidelity. No response.
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Post by Deleted on Jan 25, 2012 3:59:13 GMT
According to AKG there is NO burn in time. Is there any chance it's because AKG is pre-burning them? I asked the question 3 times at Innerfidelity. No response. An AKG engineer stated some time back that there is no such thing as burn in with their headphones.
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FritzS
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Post by FritzS on Jan 25, 2012 6:47:15 GMT
An AKG engineer stated some time back that there is no such thing as burn in with their headphones. Alex, my experience with burning in from AKG headphones, the influence overplayd in some forums. I had the chance to compair some AKG headphones with differnent burning in time. 100 hours an later the changes can not be determined accurately - they are more than subjectiv
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Post by Deleted on Jan 25, 2012 6:48:31 GMT
IMO if a headphone needs several hundreds of hours break-in and others cannot hear a difference in the same HP it is highly likely it is either the pads softening up (getting flatter, better sealing) or the listener getting used to it than actual change in the drivers. at around 16 years old I used to be an addict to 'loudness' and didn't like 'flat' sound so someone told me to remove all the bass and highs and listen to that for a week. After that period set the tone controls flat again and presto.. all sounded 'good' to my ears and hated 'loudness' after that. It shows how the brain adapts to circumstances. Tyll's measurements are inconclusive and changes are so small from before and after they can easily be caused by moving the phones around. (he did and averages them out but small differences in 'coarse' positioning can do this) Some of his graphs do not show differences and some are a bit 'manipulated' showing differences. In his tests with the 3 DT880's he 'shows' the influence of damping factor (he believes), but IF damping factor is that important he should have run a second test where he upped the output resistance of his test amp from 2 Ohm to 16 Ohm for the 250 Ohm HP and to 38 Ohm for the 600 Ohm version. IF they measured the same / sounded similar with this simple test he would have shown the damping factor is of importance. Now all he has shown is the headphones behave/sound different on the same amp. This was already known.
Those that know me by now know I don't believe most of the claims made. I can tell, however, that for the HD681 (I have modded tens of them) there are a few that sound 'thin' or bassless right out of the box and after a few mins start to give normal amounts of bass. I could easily check this when directly comparing it to a burnt in one. The three HD661's I had didn't seem to be afflicted, then again most of the HD681's I modded also did not seem to change.
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Post by Deleted on Jan 25, 2012 6:57:13 GMT
An AKG engineer stated some time back that there is no such thing as burn in with their headphones. Alex, my experience with burning in from AKG headphones, the influence overplayd in some forums. I had the chance to compair some AKG headphones with differnent burning in time. 100 hours an later the changes can not be determined accurately - they are more than subjectiv Friedrich I can't speak for the AKG headphones, but I had a pair of AT W1000 from new, that just seemed O.K. IIRC , I had to move addresses shortly after, and loaned them to a friend until the move was completed and I settled in again. When they were returned, they sounded far better, and my friend also reported that he had noticed quite an improvement, just after 48 hours of being played continuously at medium volume while covered by pillows. Alex
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Post by Deleted on Jan 25, 2012 11:16:46 GMT
I don't know whether it's my inagination or not, but high impedance phones at 600 ohms seem to have better damping properties so bass is cleaner and hits harder. Trouble is that they need a lot of power to work properly.
The only reason that they're used really is for sharing output jacks I guess so the amp sees a lighter load?
Probably, part of the breaking in is also pads changing plus your brain adjusting plus the drivers (over a very long time) lossening up.
The most dramatic change I ever heard were the Superlux. Within 30 minutes too!!!
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FritzS
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Post by FritzS on Jan 25, 2012 14:42:30 GMT
Friedrich I can't speak for the AKG headphones, but I had a pair of AT W1000 from new, that just seemed O.K. IIRC , I had to move addresses shortly after, and loaned them to a friend until the move was completed and I settled in again. When they were returned, they sounded far better, and my friend also reported that he had noticed quite an improvement, just after 48 hours of being played continuously at medium volume while covered by pillows. Alex My experience comes from comparing my burned in K701 with the burning in phase from the K702 and now the burned in K701 with the burning in phase from the Q701. I am not a burning in »believer« or ...? But on another foreside I have an »aha« experience .... my Solo »shining« more and more ... in comparison my WNA MKII are more and more »dull« This I noticed more and more in my comparison tests with Q701, K550, .... First I thought the headphones, but in comparison of all my headphones I got on it that it is the amplifier I would not thought as this is possible! And this after more than 200 ... 400 hours (I dont count them) PS: Today I have an AKG K1000 as a guest for a while first I must make an adapter - XLR 4 pins to a headphone jack. First tests are over a K1000 selector box - this use additional 25 Ohm in parallel. K1000 is a very greatful headphone ... old but very good
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Will
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Post by Will on Jan 25, 2012 19:23:42 GMT
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Post by Deleted on Jan 25, 2012 20:09:04 GMT
Very small changes, and not consistent either. One seeming to go up, the other down. It mostly looks like the top half is moving more than the bottom too which may account for people hearing less sibilance?
I wonder if the room temperature was changing?
Interesting since there do actually seem to be very slight changes in the drivers then?
Also, since one ear goes up and the other down, maybe the changes aren't consistent so that would account for different reports on changes with the same models of headphone from different users.
However, the movements are so small, it doesn't look as though it would be audible.
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Post by Deleted on Jan 25, 2012 20:21:34 GMT
cdn.head-fi.org/2/2c/2cccca83_111229_blog_burnin_RawFRBeforeAfter.jpegThese graphs are also from Tyll and show the differences are really small. Smaller than this (jumping in size too) comparison This is what Tyll says: Summary: Did I show break-in exists? No. There are too many variables still. Was it simply movement? I don't know. If I did it again to another brand new pair would I get the same results? I don't know. If I did it to an already broken in pair would I get the same results? I don't know. The differences are so small they might come from positioning on the measurement dummy. Simply measure the headphone 10 times in a row while repositioning them every time and you get the same results. www.innerfidelity.com/images/skullcandy_aviator_graph_fr.jpgThese graphs show the same HP (Tyll's measurements) measured a few times in a row and the average is taken. Notice that the graphs go up and down dB's in several measurements that are all taken with the HP moved a tiny bit on the head on each occasion/measurement to get an 'average'. a funny test: Simply move a headphone slightly on your head and hear how big the differences can be, especially in the highs where the path and angle are important. We are talking dB's just by positioning alone.. When you read his article about break-in and see the plots taken at various moments during break-in you will notice the utterly small differences (tenths of dB) go up and down but not linear over time which in itself shows the measurements have to be taken with a grain of salt or at least show time is not the only variable in the measurements . Superlux HD681 clearly shows it is real but the differences there are not 0.1dB or so but several dB's. and only change a lot in the first small time period... not talking about hours or hundreds of hours. I can't even accurately remember how something sounded 5 mins ago let alone several months. All we can remember is an impression we had and the impression you get after a certain period may be different due to MANY causes. In any case just like anything else in audio there will always be the yes and no camp. I believe many of the perceived breakin effects that are reported might be due to other aspects. I also believe some drivers do alter in the first few mins/hours.
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