The problem with comparing frequency response graphs is that you are given perspective based on the frequency at which the curve centers itself. Headroom makes the 1khz point 0 dbr as a reference point across all headphones, and while a reference is necessary and helpful in interpretation across graphs, it easily skews perception of how these things will actually compare when you put them on your head. At best measurement graphs are good for giving a general impression of what a headphone
might sound like. Remember that your earlobes and ear canals aren't shaped exactly like the dummy head used for measurement.
Here are some other perspectives. Only colors and y-axis position were adjusted from the original graphs.
Headroom graphs with curves centered at 3khz. These are the measured curves prior to smoothing, which you can see on the Headroom site by subtracting 1 from the graphID.
Both headphones feature a +10dB spike from 5khz to ~6khz. The PS1000 has a more intense 4khz spike by about 4dB. The PS1000 has more area under the curve (combined amplitude) between 4khz and 10khz. The HD800 has more area under the curve below 1khz. This graph suggests that the HD800 would sound fuller, or the PS1000 would sound brighter, by comparison.
GoldenEars graphs with curves centered at the dip in response between 3-4khz (also crossing several times between 1-3khz).
This measurement and alignment doesn't support a claim that the PS1000 treble spikes higher than the HD800. Additionally, it's hard to visually determine if the area under the curve between 4-20khz is significantly greater for either headphone. Neither is flat across 1-4khz. Both slope upward in amplitude as they extend lower in frequency from 1khz. The HD800 is of course flatter and extends further in the bass band in both the Headroom and GoldenEars graphs.
I haven't heard the HD800. I've only read hundreds of opposing posts on wether or not they are bright or if they have enough bass or if they need a cable upgrade or what amp will make them sound just right. All I can do is observe that both headphones, through the interpretation of these two datasets (collected with different equipment, under different variables, with different pairs headphones from each other) feature similarly measured peaks in the treble. Joe could find that his ears prefer one and Jane could find that her ears prefer the other when they actually put the headphones on their head (other system components aside). There is no accounting for system matching, differences in fit, differences in ear shape, musical preferences, taste in sound signature and presentation, etc. These are variables that no one can assume anything about for another member when they ask for advice. Both headphones have been loved and hated, praised and criticized. I guess the one that 'wins' is the one with the most vocal supporters.
I can only guess what I'd hear by comparison, but I know I don't hear at home what some people hear with the PS1000 during their brief meet auditions. I know that I can make my PS1000 sound brighter by shifting the position of the cups or adjusting the headband fit. Additionally, I've had three different pairs of G-cushions on hand at one time with the PS1000. Two of them were the fresh pairs shipped with two new PS1000s, one of which had been compressed a bit, perhaps by the weight of the cups during storage, the other which had not. A third pair of cushions were warped along the rim and wouldn't seal well. All three pads affected the sound differently. Only the thick, unwarped pair sounded right to me, given a firm fit and seal to my head and ears. The warped pair was brighter since it didn't seal, and the compressed pair was too full in the bass since the drivers weren't properly distanced. Seems to always be a toss up with Grado quality control, which is an obvious flaw with their business and a serious concern when you're paying so much for audio equipment. I contacted Grado by email about the pads and was told that since John hadn't changed anything about the pad manufacturing, there shouldn't be a difference. Well, there was, visually and audibly. Who knows what the shape of the pads are on all these pairs of PS1000 out there. Anyway, fit and seal is very important to the Edition 8 as well, which learned after a couple hours with them.
Meet impressions seem to make everyone an expert. It's not required to trial a pair at home to fully understand a pair of headphones in one's system, on one's head for adequate evaluation time in order to post an opinion on how a headphone performs. Comparing a dozen pairs of headphones at a meet and hearing that 'this one is brighter' or that 'this one is not as bright' to determine personal impressions with one's own ears is of value, but so is taking the time to build your own appropriate system and evaluating a pair of headphones that way. The pair of headphones I heard at a meet doesn't sound how it would with my gear in my home after I had adjusted all the variables to get the best sound I could. Easily, I can put on a pair of headphones, say 'this sucks', and then post about it on the forum to influence the purchasing decisions of others. I myself wouldn't want to do that, because that's not a proper evaluation. I value most the posts from those who have owned a pair of cans, compared it to others that they own on appropriate equipment, and determined that to their ears, this one is inferior to that one or this one is better suited for me than that one. Those posts are the most credible to me. I know the OP has pretty much ducked out of the thread, but I'm glad that he's buying one and considering buying the others later. He can decide for himself.
I wouldn't dispute that the HD800 are a reference and praiseworthy pair of headphones. I'd buy a pair build a system to get the most out of them if they were suitable for my music and tastes. But they aren't, so I chose the PS1000 and haven't regretted it. They are the reference and praiseworthy headphones that I enjoy every single time I listen to them.