[warnerwh]

This is on measurements:

http://www.gedlee.com/downloads/Chapter4.pdf

[ctviggen]

What an excellent chapter!  I'll definitely be buying the whole book.

What's interesting is that I think programs like TACT use more averaging than a program like ETF.  I think TACT has to perform quite a bit of averaging in order to get a response on which to operate.  Without smoothing, the response would have too many peaks and dips.

[Ethan Winer]

Bob,

> I think programs like TACT use more averaging than a program like ETF. <

ETF can display frequency response averaged to 1/3 octave, and many other bandwidths. Select the log response display, then click the second button from the left on the bottom.

> Without smoothing, the response would have too many peaks and dips. <

Yes, but with averaging the true response is completely hidden!

--Ethan

[ctviggen]

Ethan,

What I'm saying is that the Tact would have to do some averaging.  The filters in the Tact simply can't respond to that many "wiggles" in the response curve.  When I look at my ETF curves, for instance, and compare with the unmodified TACT curves posted by others, my ETF curves have way more undulations than the TACT.  So, it's either my room is particularly bad or the TACT is smoothing the response.  I think the latter is correct.  The only way to know is to have someone use both TACT and ETF.  

And for all you TACT lovers, here's another thing the TACT (and any other digital room correction system) cannot correct:

"It may not be obvious, but the DI [directivity index] is not correctable by any electronic means. That’s what makes it
important to design [speakers for good DI] correctly. The current fad for electronic EQ that yields perfectly flat axial responses
does not improve, or even change, the DI at all. In other words, this kind of EQ will not actually
change the results for the two speakers shown in this example very much at all. The curves of
Figure 4-6 on page 65 may become a little flatter, but none of the other plots will change at all. So instead
of having two speakers that look reasonable good and similar on axis we now have two speakers
that look perfect and identical on-axis. The problem is that the better one is still better and they will
still sound quite different. The EQ has not changed any of that. Its not even clear that it has improved
anything."

Page 71 of Chapter 4.  

By the way, I had a chance to read more of this chapter.  I can't wait for the book.

[bpape]

...and this is why treating the room first and paying attention to speaker/sub/seating placement will do you more good at ALL seats than EQ will.

Lots of peaks and dips are a reality.  EQ is great for dealing with issues that are peaks, not dips, and also those that are relatively common across many seats.  However, when you have 2 rows and one has a peak at 50Hz and the other has a null, how is an EQ going to deal with this?  It can't.  You need to treat the cause, not the symptom.

[Steve]

I thought the Frequency response portion was quite interesting for electronic components. One sees (wild example) an amplifier with an FR of +/- 3db (actually 6db variation) from 30 to 15kc, alot of "in component" artificial flavoring(s) may be added. Depends.

1) One listens and notices the lack of bass and rolled off highs. An honest amplifier that is "true" to its frequency response.

2) At first it sounds like the accurate amplifier with a 20-20kc response, plenty of bass and highs. In this case, artificial flavorings have been added to beef up the bass and highs and mask the true response of the amplifier. Some parts and distortions are known to do this. This creates sonic signature(s).

Eventually, though, one will hear the differences between the two above amps, its "sonic signature(s)" manifesting themselves.