Speaker Placement and boundary problems

[Sir Terrence]

Originally Posted by prerich

And great advice Sir T. I would also like to bring up the use of direct vs bi/di-pole speakers. I know with a dipole the nulls should be at the ears of the listener (not in height - but the part of the speaker with no drivers should be pointed at the listening position). I have in effect turned one of my pairs of Def Techs into Dipoles vice Bipoles (I wired the rear drivers in reverse phase of the forward facing ones). I find that these type speakers provide a wider and more natural soundfiled and allow for higher placement vs. the direct speaker method. I believe this is why Dipoles where inmployed in HT - because most people would not have the room to deploy 12+ rear channels. I tend to think that direct radiating speakers in the rear may offer sonic pleasure to the main listener but to others seated in less than optimum places - will suffer (IMHO). Critical speaker placement is very necessary with Direct radiating speakers - especially in the rear.

The reason dipoles were used in the DPL days has more to do with the "stereo in head" HTE that occurs when direct radiators are placed to the sides of the listening position, and firing directly at the head with a mono signal. In order to get rid of this effect, the direct path to the ears has to be changed to a different position, which causes you to lose the spaciousness that side placement gives you. The rule is side placement supports more spaciousness, and rear placement emphasizes directional characteristics. Dipoles can be placed to the sides of the room to emphasize spaciousness, and because their drivers do not fire at the ears, you do not get the "stereo in the head" effect. Bandwidth is a problem for most dipoles, as they roll off the bottom end by design. IMO the only way direct radiators really work is if they're in multiples along the side and rear walls. The have to be specifically placed apart at certain distances to de-emphasize the "directness" of the speakers. They should never be pointed at the listening position like they are in theaters. This would produce the same effect as a couple of bipoles on the side walls.

Question T, because of all of the discrete channel information have we negated or ignored the value of bipole or dipole speakers exclusively in the the rear channels? I remember in the days of prologic (before specialized speakers for surround in the home market) I used to imploy direct radiating speakers and point them at the ceiling to difuse them. I will thank Bose for one thing - I remember using a pair of 301's in an early surround system that produced a believable effects channel that didn't beam at me - but at that time surround channels were not discrete. However, I can still see the benifit of using Bipoles or Dipole speakers. What's your take on this (For you know much more than I ).

The problem with dipoles with stereo surrounds are the very thing that made them effective with DPL. They turn everything into a spacious environment, even if that is not the intended effect. With split surrounds anything from a wide open field to a closet can be simulted by the use of reverb and echo, or mixing it dry mono. The small room effect cannot be effectively simulated with dipoles, because they scatter so much sound around they always sound spacious. With bipolar surrounds you have the best of both worlds, without their problem. Bipoles are effective with "direct" effects placement, and are good at spaciousness as well. They do not suffer from the too directness of monopoles, and they do not have the bass roll off of dipoles. You can create a wide open environment, and they will accurately reproduce it. You can created an intimate environment, and they will accurate convey that. You can never get good voice matching with dipoles surrounds, and monopole front speakers, because they are both working off principles that are in complete opposition to each other. You can get accurate timbre matching from bipole surrounds and monopole fronts because you are not screwing with the phase of the speaker. I choose to use four bipolar speakers for one of my system(my review system for this site) because of that very reason. They are the best of both worlds, without the compromise of either world.