CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

Lobby => Headphone Measurements => Topic started by: Marvey on February 15, 2012, 03:32:29 AM

Title: CSDs How Do I Read These?
Post by: Marvey on February 15, 2012, 03:32:29 AM

Cumulative spectral decay (CSD) or waterfall plots measure energy content over time across all frequencies based on a "sound burst" that excites all frequencies. They are sort of like a FR over time (technically not really as they measure energy throughout the band in successively smaller windows over time.) These plots are a good tool to "see" driver ringing or resonances (seen as ridges), which typically sounds bad (piercing, glare, shoutyness, etc.); and how fast and cleanly the driver decays (speed and extraction of low level information.)

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. Successive plots over time move toward us.

OLDER LINK / Types of driver ringing: http://www.changstar.com/index.php/topic,71.msg219.html#msg219 (http://www.changstar.com/index.php/topic,71.msg219.html#msg219)

Title: Re: How Do I Read These?
Post by: Marvey on September 08, 2012, 12:36:03 AM

Harmonic distortion notes:


Taken with headphones on sealed plate. White noise at 90db SPL A-weighted.


D2 = 2nd harmonic
D3 = 3rd harmonic


etc.

Title: Re: How Do I Read These?
Post by: rhythmdevils on September 20, 2012, 06:11:21 AM

There is also some good information on reading CSD's in the beginning of this thread

http://www.head-fi.org/t/580283/lcd3-measurements#post_7891455

Title: Re: How Do I Read These?
Post by: transparent201 on September 09, 2013, 05:38:40 PM

Hello Purrin.
Have you ever thought of IMD measurements on headphones? I think that IMD is more representative because real sounds are complex. Also, what is your opinion on multitone IMD distortion test combined with a psychoacoustic model to determine what is audible?
See here: http://www.gedlee.com/downloads/Distortion_AES_II.pdf

Title: Re: How Do I Read These?
Post by: takato14 on October 06, 2014, 12:02:40 AM

Quote from: transparent201 on September 09, 2013, 05:38:40 PM

Hello Purrin.
Have you ever thought of IMD measurements on headphones? I think that IMD is more representative because real sounds are complex. Also, what is your opinion on multitone IMD distortion test combined with a psychoacoustic model to determine what is audible?
See here: http://www.gedlee.com/downloads/Distortion_AES_II.pdf

This actually might be a very useful measurement to take, if possible

I've noticed a surprising sense of clarity and cleanliness from large, thick mylar diaphragm that doesn't flex while in use, despite the slow attack/decay caused from the excessive weight of said diaphragm

I suspect an absence of modal problems and/or IMD to be the cause of this