Vandersteen VLR Speaker Review

[IPunchCholla]

"An important property of an impulse, not intuitively obvious, is that it if you break it up into individual sine waves you find that it contains all frequencies at the same amplitude. Strange but true."

"So my understanding is they are two different representations of the same thing and can be transformed back and forth."

Not quite. You can get the frequency response from the impulse response, but not the other way around. This is because the equal-amplitude sine waves in the (perfect) impulse have another property: they all have a maximum at time zero (the time of the impulse). But a flawed speaker (and they're all flawed) will not put all the peaks at time zero, but have the peaks at slightly different times. This is called "phase response". If you know both the "frequency respsone" (the amplitude of each sine wave) and the "phase response" (the offset of each sine-wave maximum from time zero), then you have enough info to reconstruct the impulse ressponse (what the speaker produces given a perfect input impulse).

Incidentally, a perfect impulse is mathematically a "Dirac delta function", invented by physicist Paul Dirac: https://en.wikipedia.org/wiki/Dirac_delta_function. I'm pretty sure this is why the Dirac room correction system was given that name.

Thank you for the clarification. That helped quite a bit. I somehow never really understood the last sentence.

 

[MarkS]

I somehow never really understood the last sentence.

The Dirac Live speaker and room correction system tries to correct the impulse response of your speakers plus room to make their overall impulse response more like a perfect one, which is mathematically described by the Dirac delta function. ("delta" is just the Greek letter that physicist Paul Dirac chose to use as the name of the function; it has no other meaning in this context.) I haven't ever seen the company give this explanation of their name, but it seems very likely to me.

 

[Holmz]

Maybe I confused, actually probably I am confused, but REW says this:



So my understanding is they are two different representations of the same thing and can be transformed back and forth. Why impulse response is important is:

One thing that REW Sort of implies, and which really adds a troublesome component is that the fact that there is a room.
Ideally the speaker is characterized independent of the room.
Group delay is a way to characterise the speaker.
As mentioned the Dirac delta function is what an ideal speaker should look like., and a non ideal speaker can be pre-distorted in a way to make it perform closer to the ideal.

All of ^that time domain stuff^ is independent of frequency domain room correction for destructive and constructive room modes.

And echos in the room, are time domain combs, which look like delayed impulses (If one actually shoots the pistol), or recreates that mathematically.

 

[Holmz]

For me, that's because the impulse response is a bit harder to conceptualize, even though it can be generated from the frequency response (and vice versa). I mean, I pretty much understand what being 5dB down at 1k will sound like, but have a much harder time gathering that same information from impulse response. Likely some of it is familiarity, but some is how the information is presented.

I think if we are talking abiout a piano or a harp, flute or french horn, then frequency domain sort if makes sense in a continuous wave sense.

Once we start looking at a drum stick tapping on the rim of a drum or striking a cow bell, then those are percussive and look like impulse.

But in either case, The signal pushed through the system’s impulse response, replicates whet that the system Is doing.