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LCD3 Measurements - Page 9

post #121 of 236
Quote:
Originally Posted by purrin View Post


      Quote:


I would ask you to send yours to me, but that may not be a good idea because are where you are.


I have already thought about it, but, as you said, it is not good idea, and not only because of the air mail cost (there is also the danger to double pay the taxes eek.gif).

And sorry to all the members for this off-topic sub-thread.

 

 

 

 

post #122 of 236
Quote:
Originally Posted by rhythmdevils View Post

I think Audeze made a mistake supplying their graphs.  It's got too much smoothing and doesn't show both channels and there's too much variance in the positioning for them to mean anything (according to yall anyways).  Or there is actual variance in the drivers.  Either way, the only thing they contribute is paranoia.  If I paid 2k and got a graph that had a weird valley I'd rip my own nuts off. 

 

I get why they wanted to, because professional speaker monitors come with them (or at least mine did) so it gives them that nice flava flave but they ought to either be meaningful or axed IMO, 



I have yet to look at the graph that came with my LCD-2 r.2.    

post #123 of 236
Quote:
Originally Posted by purrin View Post

 

  1. I've seen these types of dips now and then on horn speakers and other headphones. I can't seem to hear anything bad and I've confirmed via test tones (although not yet on the LCD3), that these dips aren't audible and are probably measurement artifacts (the odd cancellation caused by pads/enclosure, neutrinos moving faster than light, etc.


Hahaha that made my day!

post #124 of 236

Just like to add my thanks to Purrin for taking the time to produce these various measurements (and a crash course on how to read them to boot!) and those who apparently sent their headphones to him for testing. This was the first time I have been on head-fi in a long time and also the first time I was able to get really interesting technical info about a new headphon the first time I searched. Lastly, I am also QUITE impressed this somehow managed to escape the "abyss" sub-forum ( Sound Science). Seems like things have changed a lot since I have been gone... but then I checked the LCD-2 thread :P. Keep threads like this coming and I might just get hooked on forums again ;). TY again sirs.

post #125 of 236

Here is the frequency graphs for LCD3 vs. LCD2 from HeadRoom:

 

LCD2 vs LCD3.png

 

LCD3 is blue.

post #126 of 236

Fantastic reading, thank you !

 

I have a conceptual question though that I would like to formulate to you. The waterfall plot shown below would appear to be the results of a completely anechoic room/enclosure as I understand this, and might not be very relevant of what headphones should really sound like.

 

Is there such a thing as an ideal RT60 time for headphones ? Shouldn't headphone try to recreate an ideal listening room with some reverberation ? I read somewhere that ideal reverberation should be constant over the frequency spectrum (at least, from 80Hz and up). What do you think ?

 

 

Quote:
Originally Posted by purrin View Post
 
This is what a perfect waterfall plot would look like:
c518b311_perfect.txt.jpeg
For a perfect or near-perfect response, the decay should be immediate. We first see a wall (meaning all frequencies are excited) at the beginning. The next few fractions of a millisecond, the wall collapses into silence (meaning the driver is no longer vibrating or sound waves are no longer bouncing around inside the headphone enclosures.) The back wall at time = 0 is basically an uncompensated frequency response. Success plots over time move toward us.


 

 

post #127 of 236
Thread Starter 
Quote:
Originally Posted by shamu144 View Post

Fantastic reading, thank you !

 

I have a conceptual question though that I would like to formulate to you. The waterfall plot shown below would appear to be the results of a completely anechoic room/enclosure as I understand this, and might not be very relevant of what headphones should really sound like.

 

Is there such a thing as an ideal RT60 time for headphones ? Shouldn't headphone try to recreate an ideal listening room with some reverberation ? I read somewhere that ideal reverberation should be constant over the frequency spectrum (at least, from 80Hz and up). What do you think ?

 

The plot below represents primarily driver with partial enclosure diffraction effects. CSDs are never used to measure room effects, even with speakers (we gate the impulse response before the reflections as much as possible.)

 

As far as simulating the effects of a listening room, it would be impossible for headphones by themselves to do this for obvious reasons. There is an aural optimizer product out there that supposedly works well. I forgot what it's called. Anyone care to chime in?

post #128 of 236
Quote:
Originally Posted by purrin View Post

As far as simulating the effects of a listening room, it would be impossible for headphones by themselves to do this for obvious reasons. There is an aural optimizer product out there that supposedly works well. I forgot what it's called. Anyone care to chime in?


You mean the Smyth Realiser?

post #129 of 236
Quote:
Originally Posted by purrin View Post



 

The plot below represents primarily driver with partial enclosure diffraction effects. CSDs are never used to measure room effects, even with speakers (we gate the impulse response before the reflections as much as possible.)


Oh I see it was my misunderstanding... I assume then there must be some sort of software correction to remove the effect of the reflections hitting the microphone. So what those graphs are in fact implying is the effect of the energy stored and released progresively by the driver itself but without considering reflections that will form in the cavity of the earcup (kind of anechoic conditions) ?
post #130 of 236

The room reflections are excluded naturally (you only use the first few ms

of data before any reflection from a wall comes back). 

 

Those from the headphone enclosure are included, except that Marv's rig minimizes those in the earcup with his sound absorbing baffle mount.

 

Even in Marv's rig, reflections from the outer cup are there unaltered but more or less visible depending on the design (closed or

open design).

 

The perfect result shown was just that: a headphone free of driver or frame resonance and cavity wall reflection.

 

The analogy to room acoustics is very interesting though: we talk about reverberation time in that case. And indeed, I believe for a concert hall the ideal R T does not change with frequency. I think it's the same with a classroom as RT must not exceed a certain value to get reasonable speech intelligibility.

 

Interestingly though, we never use this type of csd processing in the case of room characterization but compute the reverberation time (T30, T60) from a room response which prealably goes through some octave or third octave band filters.

 

I always wondered if I'd get similar result by processing a room impulse response through my csd routine. I assume it would unless the room is dead quiet and all I saw was the ringing of the filters and other equipment who's dynamics are in the data (typically the speaker,amp...). Actually, this artificial ringing introduced by the filters is probably a good reason why you want to do a csd rather than t60 analysis of such fast decang system as a headphone...

post #131 of 236

Got it ! Thank you for clarifying.

 

Now, let me rephrase my previous question. Since some earcup reflections will always exist in a headphone, is there such a thing as an ideal theorical CSD ? Would this CSD aim for a constant decay (T30 ?) of a few ms from 100Hz (as an example) and up, just like it seems important for room reverberation to show a constant T60 in that same range ?

 

Can we assume that the early earcup cavity reflections plays the same role as room reverberation for our auditory sense ? Maybe this trick doesn't work with headphones, since room reverberation are more in the second range, while earcup reflections are in the millisecond range. But of course, distance for headphones is much shorter from the driver to the ear, so maybe there is some kind of correlation...
 

Quote:
Originally Posted by arnaud View Post

 

The perfect result shown was just that: a headphone free of driver or frame resonance and cavity wall reflection.

 

post #132 of 236

The best theorical CSD would llok like a wall, immediate drop to to bottom, no jaggies, no mountainous peaks and valleys, just a wall.

post #133 of 236


But this would only be possible with no driver resonance, no frame resonance, no earcup resonance... Dead sound, not really nice to listen to, similar to an anechoic room ?
 

Quote:
Originally Posted by khaos974 View Post

The best theorical CSD would llok like a wall, immediate drop to to bottom, no jaggies, no mountainous peaks and valleys, just a wall.



 

post #134 of 236

Hmmm, I guess the perfect CSD would depend a lot on the coupling used to measure it.

post #135 of 236
Thread Starter 
Quote:
Originally Posted by shamu144 View Post

Got it ! Thank you for clarifying.

 

Now, let me rephrase my previous question. Since some earcup reflections will always exist in a headphone, is there such a thing as an ideal theorical CSD ? Would this CSD aim for a constant decay (T30 ?) of a few ms from 100Hz (as an example) and up, just like it seems important for room reverberation to show a constant T60 in that same range ?

 

Can we assume that the early earcup cavity reflections plays the same role as room reverberation for our auditory sense ? Maybe this trick doesn't work with headphones, since room reverberation are more in the second range, while earcup reflections are in the millisecond range. But of course, distance for headphones is much shorter from the driver to the ear, so maybe there is some kind of correlation...


Good questions. My personal opinion and conjecture:

 

  1. Earcup reflections sound a lot different from room / wall reflections - this should be obvious subjectively if you have a speaker set in a room.
  2. Because the earcup reflections are early, they very heavily influence measured FR/CSDs, etc. - although there are ways to minimize the influence (Arnaud hinted at the method I am using.)
  3. The fleshy supercomputer between out ears is eventually able to filter early earcup reflections to a large but not complete extent.
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