I want to see an actually measured frequency response graph. These debates are just endless without objective data.
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There is just so much craptastic dreck in the
Oppo PM-1 Planar Magnetic Headphone Impressions Thread - Page 19
Head-Fi's Best Sellers
Or he can fuel the fire further. From people's impressions, PM-1 seems to have frequency response Tyll usually likes a lot.
Hold on, the only clean way to do this by ear is not absolute sense but relative. In this case, I was under the assumption you identified deviations from neutral by direct comparisons to your speaker rig at the listening position where it's supposed to be flat.
As others have said, if you go by perceived loudness, it makes no sense whatsoever unless you're using rather close thin bands for evaluation. Loudness curves don't vary drastically with frequency, except if your ears are shot - might then get sharp drops at 4kHz and more or less wide / deep depending on how deaf you are.
I really can't imagine you can do this test practically using pure tones though, it must be hell of a work!
I wasn't clear I guess. It's a kind of complicated process and hard to put in a post, but I'll try to make it clearer...
I did a response check on three different beta versions of the Oppo cans. The first two betas I checked by listening to music with acoustic instruments that I was familar with from balancing my speaker rig. I did that with my third beta too, but after I was done, I called in my sound mixer friend to help me do tone sweeps to verify what I had found and to get more precise corrections.
My friend EQs using tones for a living. He is designing a new PA system for live venues that would involve carefully balanced EQ and horn loaded bass speakers that cover the entire range of human hearing. (That is a lot harder than it sounds, but he has some pretty interesting ideas on how to accomplish it.) When I told him that I was evaluating these headphones and that they seemed remarkably flat to me, he said he was interested in stopping by with some of his equipment and running them through their paces. He had some theories about the differences between speakers and headphones and wanted to hear flat headphones to compare to his flat speaker installation in his workshop.
When he EQs, he does sweeps in very small bands at a time, dialing the variable signal generator back and forth carefully, listening for bumps and dips. As he finds them, he corrects for them precisely using his digital equalizer. After he works his way up octave by octave from the lowest bass to the highest high, he ups the volume level and goes back to the lowest bass and repeats the whole process. With speaker installations he can end up doing that five or six times until the volume is on the edge of hurting your ears. We weren't as concerned with complete accuracy here, so we just did two passes- medium and loud. After we finished, we made note of all of the corrections on the equalizer we had made and he did a couple of quick passes making progressively wider and wider sweeps. I don't think he made any corrections in those last wide sweeps, but I wasn't paying a lot of attention to what he was doing. At the end, he was really spinning the dial on the frequency sweep as fast as it would go, so he must have been hearing most of the audible range in one sweep I would guess.
When all was said and done, there were two spots, 3kHz and 6kHz where we identified a 3dB boost, which was exactly what I had estimated the day before using my rougher system of EQing using music. My buddy is able to EQ much faster using tones than I can with my technique, and more accurately too. But I was happy to find that my system of balancing identified the two 3dB bumps in the beta version. The tone sweep technique revealed a handful of small 1 and 2dB narrow range bumps and dips that my rougher EQing technique and cruder equalizer weren't fine enough to isolate. After he did the wide range sweeps on the beta 3, I handed my buddy the beta 2 copy I still had on hand, and he did a quick pass by himself on them using the equalizer corrections we made for the beta 3. He determined that the difference between them was that the beta 2 had a slightly smaller bump at 6kHz. Aside from that, they were identical. Probably just variation in samples.
I just received the final retail version and compared it to the beta 3 copy I still have on hand here. It appears that the final retail version doesn't have the same bumps at 3 and 6. It sounds like those imbalances have been smoothed out. But I haven't called my friend to come run tone sweeps on the final version yet. In any case, nothing we found was bigger than +/- 3-4dB on either of the beta versions we tested, and most of the imbalances were in the range of 1-2dB. Below 1.6kHz, it was stone flat with no imbalances at all all the way down to 28Hz. That is a pretty damn good response curve and the final retail version sounds even a little bit better. I'd like to get my speakers as balanced as these headphones someday, particularly in the low end. Totally natural sound. Present and realistic.
Edited by bigshot - 4/6/14 at 3:05am
Here are the notes of the exact frequencies and level changes we measured over the entire audible spectrum for the beta 3s. You can plot it all of the data out on a graph if that makes it seem more real to you.
Below 25 drops off steep
-4dB at 25Hz
28Hz to 1.6kHz stone flat
-3dB at 2kHz
+2dB at 2.5kHz
-2dB at 3.1kHz
-3dB at 4kHz
-1dB at 5kHz
+3dB at 6kHz
-2dB at 7kHz
8 to 10kHz stone flat
-3 at 11kHz
flat at 11.5kHz
12kHz roll off starts
Based on comparing the Beta 3s to the final retail, I would estimate that the drops on either side of 3kHz are a bit smoother on the final retail. But something this small could be just sample variation too. In any case, it's nowhere near the 10 to 20dB bumps and dips on the Beats response graph posted earlier.
Edited by bigshot - 4/6/14 at 3:15am
What is the ideal frequency response for a headphone?
Are you saying that you heard the phones and that they are so good that one has to hear them to believe it?
Most headphones have a nice big hump on the left and a whole bunch of wiggles on the right. Is that ideal? (winky emoticon here)
Edited by bigshot - 4/6/14 at 3:21am
That sounds to me like a clarity issue, which would be a function of either distortion (which these headphones are remarkably free of) or frequency masking (which is eliminated by a balanced response). The attack and decay are exactly as they are recorded. Transient dynamics are super tight.
When I put my hands over the backs of the earcups, I don't hear any difference in sound if that helps.
Ok... I guess I won't try to convince you otherwise.
The stuff in bold is a bit worrying to me though... That's not how most open headphones react when you close the openings - the sound should be more closed in from my experience.
It's not known for sure yet. But what we know it's definitely not flat. Different researches show different results. One of them something like that.
Just a quick clarification... when I say flat response, I mean *audibly* flat, not mechanically flat. Flat response in the way we perceive a frequency response, not the way a machine measures it.
Edited by bigshot - 4/6/14 at 3:43am
The cups are built in layers like a sandwich. There might be other spots where it's open. It's hard to tell. The specs call it an open back design though.
No, it's not. There is an idea that because heaphone's driver is parallel (or almost) and very close to your ears it sounds bright because of the special form of the ear channel and ear conch .
There lies a problem. Imagine you and I have the exact same ears. You listen to music at 70 dB. For you it seems perfetly flat. But I listen to loudly, at 80 or 90 ( I don't care about my hearing for example). And the same headphones are not going to sound flat to me because of equal loudness contours.
Edited by qazxsw80 - 4/6/14 at 4:08am
if he likes it he'll say so but he doesn't hype gear. anyways there's always the measurements.
- Oppo PM-1 Planar Magnetic Headphone Impressions Thread
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