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Old 1st June 2011, 02:06 AM   #1771
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Location: Portland Oregon, USA
Originally Posted by AllenB View Post
There is no noticeable boom...although you can see on the plot there is a peak at 200Hz and I can hear that and I'm thinking of notching it.
I think what we perceive as boominess is really the uneveness of the lower mid and bass region. Any high points can and should be EQ'd down, but if you try to bring up a cancellation, you end up causing peaks in other locations of the room, so that is not recommended. I think flankers of some sort may be the only way to even out those particular boom causing cancellations.
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Old 1st June 2011, 10:03 AM   #1772
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Originally Posted by AllenB View Post
I have found a location where helper woofers 'help'. They are placed part way between myself and the mains on the perimeter of the listening triangle closer to the speakers. I believe that perhaps at least half of the sub 300Hz anomalies are floor and ceiling related.

Subjective thoughts are that this is better. EQ or no EQ, it simply sounds better. No amount of EQ could seem to fix the mains only result to sound as good.
You know Allen, my response used to look similar. But with more placement trial and error, you should be able to do much better.
Click the image to open in full size.
Click the image to open in full size.
Is possible through placement. I ended up turning the bass knob up a bit since that graph. It was down almost all the way.

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Old 6th August 2011, 12:41 PM   #1773
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Originally Posted by speaker dave View Post
Since we were discussing dipoles and I was voiceing a concern about extra full range energy that would bounce off the front wall, while others were saying "so what", I thought I'd do a reasonable simulation of it. Dipoles 5 ft in front of a wall were suggested so that would be a reflection delay of about11 ms. Rear output is out of phase (which sounded like it lowered all the resonance pitches when I did that in the simulation).

The only other variable would be the attenuation of the back bounce which is a combination of extra distance, actual radiation angle and wall reflectivity. I think the 5dB reduced reflection is realistic for a dipole in front of a non-absorbtive wall.

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This is a rather old post, but I remembered it while reading Toole's book just now. He claims delayed sounds from the same direction as the primary sound have a significantly higher threshold of audibility than reflections from other directions. There is no mention of the gross coloration audible with your sound samples. Interesting; maybe dipoles should not be disregarded too soon.

Originally Posted by Toole - Sound Reproduction (p. 82)
Another surprise in Figure 6.7 is that delayed sounds that come from the
same loudspeaker are more diffi cult to hear; the threshold here is consistently
higher than for sounds that arrive from the side or above, slightly for short
delays, and much higher (10+ dB) at long delays. Burgtorf (1961) agrees, fi nding
thresholds for coincident delayed sounds to be 5–10 dB higher than those sepa-
rated by 40–80°. Seraphim (1961) used a delayed source that was positioned just
above the direct-sound source (∼5° elevation difference) and found that, with
speech, the threshold was elevated by about 5 dB compared to one at a 30° hori-
zontal separation. The relative insensitivity to coincident sounds appears to be
real, and the explanation seems to be that it is the result of spectral similarities
between the direct sound and the delayed sound. These sounds take on progres-
sively greater timbral differences as they are elevated (or, one assumes, lowered)
relative to the direct sound. For those readers who have been wondering about
the phenomenon of “comb fi ltering,” which will be specifi cally addressed in
Chapter 9, it is worthy of note that this evidence tells us that the situation of
maximum comb fi ltering, when the direct and delayed sounds emerge from the
same loudspeaker, is the one for which we are least sensitive. (Encouraging
All this said, it still seems remarkable that a vertically displaced refl ection,
with no apparent binaural (between the ears) differences, can be detected as
well as a refl ection that arrives from the side, generating large binaural differ-
ences. Not only are the auditory effects at threshold different—timbre versus
spaciousness—the perceptual mechanisms required for their detection are also
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