how to...

[Rudolf]

Dipoles increase the sound stage depth due to the strong front wall reflection - basically they are creating a secondary phantom acoustic source - imagine that the front wall were a tinted glass mirror. The sound stage is made artifically deeper. It can be a desirable effect ... However, in other situations where you want a focused sharp image, dipoles don't perform as well. You don't get the same pinpoint imaging ...

Paul,
this probably needs to be discussed in more detail.
It is true that the Initial Time Delay Gap (ITDG) of front (and side) wall reflections will move the sound stage towards the front wall. This is desirable IMHO, not least because it very much helps to clear the sound from the speakers.

Now let’s look at fig. 5.2 in Tooles “Sound Reproduction” (page 70). “Image integrity and size” as well as “source broadening” is controlled in the 500-5000 Hz region mainly, centered around 2 kHz. We don’t need to eliminate all front wall reflections and for all frequencies. Just picking out the first reflection and the right frequency range helps a lot. I had great success with small (30x30 cm) patches of 4 cm Basotect BASF PlasticsPortal - Basotect placed at the mirror positions. They lowered the first reflection from the front wall to -20 dB. Fig. 6.7 will tell you that this is sufficient for most people.

Rudolf

 

[a_tewinkel]

I fail to see a qualitative difference between using a reverb and using speakers which spread their sound all over the place in an only lightly (or not at all) damped room.
Except that a reverb is more controllable.

Reverb should arrive from different angles and specifically from large lateral angles to lower IACC. Reverb which comes from the speakers will sound louder and less spacious because the brain has more difficulty with de-reverberation.