Archived from groups: rec.audio.pro (
More info?)
Scott Dorsey wrote:
> Bob Cain <arcane@arcanemethods.com> wrote:
>
>>Scott Dorsey wrote:
>>
>>>See, room problems aren't frequency domain problems, they are time domain
>>>problems. The frequency response issue is only a symptom, it's not the
>>>real problem.
>>
>>Scott, I often see this stated but take issue with it.
>>Frequency and time _domain_ are exact duals. One is
>>entirely determined by the other and both imply a
>>transformation of both magnitude and group delay as a
>>function of frequency.
>
> Right, this is why you get those frequency domain symptoms.
What do you mean by frequency domain symptoms?
>>The problem is twofold. First, problems can't be fixed by a
>>box that only adjusts magnitude response (like a graphic
>>equalizer) without also fixing the group delay response.
>
> This is a minimal issue.
On the contrary, it is essential.
> What I mean, is that the room problems are the result of time delay
> and summing of delayed reflections. The frequency response issues are
> only the result of cancellation from the time delay issues.
Yes, the frequency response issues are caused by the time
delay and summing of delayed reflections, among other things
like frequency dependant absorption. You seem to be trying
to distinguish among, room problems, time delay and summing
and frequency response. They are all the same thing at the
point where your ear is located.
When you say "frequency response" do you really mean
frequency magnitude response? If so then we aren't on the
same page and that could account for our cross
communication. When I say "frequency response" I mean
everything that varies as a function of frequency.
> Well, it's easier to think of the delay in terms of the time domain
> and it's easier to think of response issues in terms of the frequency
> domain. When you go to explain them, you draw a scope diagram and
> a spectrum analyzer diagram respectively.
Yeah, we are saying similar things using opposing terms.
Technically, frequency response is composed of a group delay
response (phase for purposes of calculating interference
results) and a magnitude response. In the audio world, as
opposed to the physics, EE or DSP world, frequency response
seems to mean just magnitude response and that gets
problematic in discussions with engineers.
I think we would agree that you can't fix a room generally
by anything that even treats both components of the
frequency response, other than at a point, much less a thing
that only treats one of the components.
Bob
--
"Things should be described as simply as possible, but no
simpler."
A. Einstein