Cumulative Spectrum Decay. What...?

[tolits]

Hi,

What does CSD reveal in terms of how a loudspeaker would sound.?TIA

Lito

[noodle_snacks]

shows the driver's energy storage vs frequency (afaik). If a metal coned driver has a cone-breakup resonance at a certain frequency then a long "tail" will be shown, indicating the driver is ringing at that frequency.

[soongsc]

It's really hard to explain just talking in general terms. But you can be sure that if you are using a non-cyclic signal through the driver and determine distortion levels from that, better CSD will have better distortion figures. This may not be true if you do distortion testing with sine waves. Different parts of the CSD has different effects.

[SY]

d'Appolito has a thorough explanation in his book "Testing Loudspeakers."

[Zaph]

In addition to comments by others, I would like to note that a CSD is not the most useful form of measurement because there is absolutely nothing in there that isn't shown in the frequency response curve.

Honestly, I'm not even sure why I post them myself. I think maybe it's because I'm impressed by pretty colors. But otherwise, it's just another way of looking at a response curve. Both are generated from the same impulse.

[soongsc]

I wonder which driver this CSD if for. It looks good for a super tweeter. If the starting marker can be moved to where the phase curve shows minimum phase, the CSD would be more clear. The focus of this driver may not be very good. I think you probably have this plot set at 8~10 samples per line? The 7K~8K region is where you will hear some sort of sonic signature unique to the driver, probably one specific note will stand out during listening if you XO lowere than 10K.

[Curmudgeon]

I find them quite important. The ringing causes the note to sustain, so the total power over time is quite high, higher than the peak alone would indicate. In addition, the note continues as the music "moves on", often increasing the audibility, as it is unmasked, or at least masked less well, than it was when it was originally stimulated by an instrument with fundamentals and harmonics. To try to be a little clearer; if the ringing is initiated by a second harmonic of an instrument's note, the fundamental, and fourth harmonic will be sounding at the same time. The ringing then will continue for some period of time (2,3, 5? ) ms after the note is cut off, and then the ringing will not be covered up to any degree by the fundamental and other harmonics. As a result, the audibility is quite high, and I've found in the case of woofer breakup (which tends to fall into the spectral area where the ear is most sensitive anyway) that it is necessary to suppress a ringing peak by 35 to 40 dB to be inaudible, which may well require a trap.

[soongsc]

Different charts let you look at the sound different ways just like a good doctor does trying to diagnos a problem. Even looking at the same chart, different doctors may come up with different conclusions. One is familar enough with the basic physics of the driver, one can play with the driver and see what changes result in audible results, and relate it with measured data.