Cote Dazur
Addicted to Fun and Learning
Truthear Hola
+1Truthear Hola
That's not a bad idea, although possibly hard to get 15 units cost wise, and also Amir would have to change his headphone measurement process in order to display the results - currently he displays one measurement, it's not an average of multiple measurements, and inorder to accurately portray the differences then multiple measurements of the same unit with reseats inbetween would be required to accurately describe each unit before comparison against the other units. You'd probably eventually want to do this unit to unit variation analysis with a few different headphone models split over a few different manufacturers for a couple of reasons: first it's not fair just to target one manufacturer, second it could help differentiate which manufacturers have the best unit to unit variation. This is really a massive project, probably most significantly from a cost perspective (but time too), Amir would probably have to commit to buying them all new to remove the user abuse & pad wear variable, and he'd probably have to commit to making the effort of selling the units after testing to try to recoup some of the cost of buying them in the first place. Unit to unit variation is an important aspect of headphone quality for sure, and we don't have a lot of visibility on this currently.I think it would be interesting to see a review of 15 of the same headphones to get a feel for how extreme unit variance is.
I was thinking a single graph (per metric) with different colours for each headphone. Also, there's nothing wrong with different ages - with enough of them any pattern of age vs frequency response should be clear even if there is unit variation. It would also be useful for donors to state where/when they bought them, some yardstick of how well used they've been (daily use for 5 years vs once a week for 2 years then sat in a drawer).That's not a bad idea, although possibly hard to get 15 units cost wise, and also Amir would have to change his headphone measurement process in order to display the results - currently he displays one measurement, it's not an average of multiple measurements, and inorder to accurately portray the differences then multiple measurements of the same unit with reseats inbetween would be required to accurately describe each unit before comparison against the other units. You'd probably eventually want to do this unit to unit variation analysis with a few different headphone models split over a few different manufacturers for a couple of reasons: first it's not fair just to target one manufacturer, second it could help differentiate which manufacturers have the best unit to unit variation. This is really a massive project, probably most significantly from a cost perspective (but time too), Amir would probably have to commit to buying them all new to remove the user abuse & pad wear variable, and he'd probably have to commit to making the effort of selling the units after testing to try to recoup some of the cost of buying them in the first place. Unit to unit variation is an important aspect of headphone quality for sure, and we don't have a lot of visibility on this currently.
Maybe there could be a way to help fund it if Amir had the project as a rolling/running project whereby he polled the users on ASR quarterly (4 times a year) as to what headphone they'd like to have measured next for unit to unit variation & then a donation fund would be set up for that headphone, and once the donations had reached their target then the units could be bought & then tested & reviewed. I'm not sure what would happen if target was never reached though, and if people would get their donations back in that situation. I also don't know if enough people would donate, I don't know the readership levels & how many would be willing to donate.
What I mean is that Amir doesn't currently show an average measurement, he just publishes a chosen single actual measurement in his reviews - if he were to start a unit to unit variation project it would require him to do multiple measurements of a unit with a reseat inbetween each measurement, and he would then take an average of those say ten measurements, and that would be the frequency response for Unit#1 for instance....he would then do the same process for Unit#2....then graph the average line of each unit on the same graph.I was thinking a single graph (per metric) with different colours for each headphone. Also, there's nothing wrong with different ages - with enough of them any pattern of age vs frequency response should be clear even if there is unit variation. It would also be useful for donors to state where/when they bought them, some yardstick of how well used they've been (daily use for 5 years vs once a week for 2 years then sat in a drawer).
Perhaps naively I'm interested in the drivers themselves not the pads. Remove the pads, measure the output.What I mean is that Amir doesn't currently show an average measurement, he just publishes a chosen single actual measurement in his reviews - if he were to start a unit to unit variation project it would require him to do multiple measurements of a unit with a reseat inbetween each measurement, and he would then take an average of those say ten measurements, and that would be the frequency response for Unit#1 for instance....he would then do the same process for Unit#2....then graph the average line of each unit on the same graph.
There's some significant & large differences associated with pad aging, no way you could get sensible results by using a random selection of used & new headphones. At the very least you would need to replace the pads on the used headphones, and it shouldn't really be the same new pad that you swap through each headphone either, as part of unit to unit variation can be variation within the manufacture of the pad itself. I think you'd have to be buying new units to measure them to get a fair/accurate representation of unit to unit variation. I know Oratory measures used & new headphones, but there's a logic in creating an EQ that reflects an average age population of headphones as it will be more accurate in taking in different degrees of aging of pad. I suppose there is an argument that if pad wear creates big changes in frequency response, then that itself creates real world unit to unit variation, and I'm sure some models of headphone are more susceptible to that than others....so there can be an argument for doing it the way you suggest re users sending in their headphones, as arguably a headphone design that doesn't vary much with age is a positive, although it doesn't quite fairly capture the market of people who change their pads regularly. I'm a bit more inclined to agree with you now I've thought this through as I've been typing, but I think ultimately it's more useful for the headphones to be measured with new pads as that is highlighting the actual unit to unit variation from the factory rather than being attributable to wear.
It would be pretty interesting to see an occasional speaker review where two or more units were measured on the Klippel to see what kind of differences we're talking.Perhaps naively I'm interested in the drivers themselves not the pads. Remove the pads, measure the output.
I appreciate that people say the pads make a difference but to me it's just another factor like head size/shape, do you wear glasses (and if so which type), how about hair etc. I recently-ish bought some new pads for my old HD 595: objectively there's no way to do a blind test and subjectively I didn't notice any difference at all. (I'm unlikely to replace pads unless they look "distressed" or are uncomfortable). I do EQ my headphones based off Oratory/Amir's suggestions and then changing it to my own taste (I always add a little to the high-end), so any changes per unit, new pads etc are just yet more factors I'm going to end up dealing with by ear with no objective right/wrong.
If you wanted to see if there was unit variance in the pads themselves then you'd surely just measure them all on one pair of headphones and get a feel for how they affect the sound but then perform the headphone tests proper with either any one set of pads no pads. If you were interested in seeing how well matched the drivers are you'd need to use the same pad for left and right ear - yet more work!
Unit variance could be tested on other products. It always amuses me to see criticism of Amir's tests as him having been given "golden samples" or something. Nearly everything's made on a production line so it's not clear how this or that instance of an amp/dac could behave any differently to any other (assuming it passed basic QC tests and survived the journey(s) from factory to user). But I guess QCing and attention to detail is partly what we'd be testing here - not so much "did he get a golden sample" but "is this manufacturer competent to mass produce stuff repeatably".
thieaudio ghost (with meze 109 pads) and meze 109 pro a well known youtubers claims they are almost the same....