Direct vs Bipole

[Chris A]

Ok I need to know what is best for rear surround sound speakers. Direct speakers will send the sound straight forward. Bipole will be room filling. this is what I keep reading . What to do please help.

I totally missed the "bipole" remark, obviously thinking about "dipole" which is a totally different animal.

One of the characteristics of a bipolar-radiating speaker is that, at least in theory, it doesn't have the 90-degree off-axis-null of a dipole-radiating speaker. Klipsch obviously makes bipole-radiating designs that I understand are extremely good, as do other manufacturers.

One question is: why not just use a single constant-coverage speaker if you are going to mount these on the wall. This is actually an important question since the geometry of the listening positions in-room determines the answer. I believe that bipolar-radiating speakers are marketed for those folks that have a long and narrow seating area in their HTs.

Inkabod: In your HT that you describe, I'm not sure that you actually need a bipole-radiating speakers for surrounds since I assume that you have only one or two rows of seats. At issue here is the coverage pattern ("polars") of surround bipolar-radiating speaker. Horns can be designed to cover at least 110 degrees of arc in both vertical and horizontal dimensions in the mid-and-high frequency regions and need ony one set of drivers, whereas bipolar speakers usually use two sets of drivers.

The issue is interference between the drivers at the polar-coordinate mid-line boundary between like drivers. If designed well, there should be little to no image disruption at these critical polar angles. But it's probably easier to design a conventional horn-loaded speaker (midrange and hf) to cover your listening area. Toole talks about this in his book, and prefers conventional full-range speakers all the way around. I find his arguments compelling, and have set up my theater accordingly, using Cornwalls as surrounds, but note that I have only two rows of seating in my HT and a relatively live room toward the middle and rear sections of the room.

Chris

[Inkabodpain]

I was told by a klipsch support rep that if my seating was close to the back wall or against the back wall I should use bipole speakers. If my seating was 3ft or greater from back wall I then should use direct speakers. True or untrue?

[Chris A]

This is an interesting answer from Klipsch support...

I can only assume that they are counting on the first reflection from the rear wall to provide an additional "phantom" speaker image from the rear-facing drivers in the bipole speaker mounted on a side wall (notionally the shortest path to the closest wall). The bipolar drivers oriented toward the front of the room will cover the room front and bounce off the front wall, providing a sense of envelopment from the side surrounds.

However, if Klipsch support is referring to use as back-surround speakers mounted on the back wall, then the effect will be that the drivers pointed toward the center of the room will be the direct path, and the drivers pointed toward the outside will bounce off the side walls (which is a short path). Hmmm [:^)]

In both cases, the effect of side or rear wall bounce is accentuated with bipole speakers, but conventional speakers would mainly reflect off of the opposing wall only, and the "side lobes" of the conventional speaker would reflect off of the adjacent (closest) wall. Hmmm. [:^)]

I'm not sure that I fully understand the Klipsch Support advice. I bet it is related to the opposing wall bounce - bipolar speakers will minimize bounce in that direction, while conventional speakers will be max in that direction. Hmmm. [:^)]

Well...if you are using absorbing material on your side and rear walls, then I'd see the advantage of the bipoles, but if the walls are not treated with absorbing material, I would think that conventional speakers might create a more realistic image. Interesting.

I'd ask the Klipsch guys about their assumptions relative to your room (length of side walls, width of front/back walls, height, and absorption). Also, I'd ask about what they are trying to achieve - lots of "bounce" like a Bose speaker, or more "direct path" like a conventional speaker. Additionally, are they assuming that you would point your surrounds at your prime listening positions, or mount them flat against the wall.

Toole basically is saying that you should have the same type of speaker (performance-wise) all the way around in order to achieve an equal sound field in each channel. There is some wisdom to this, but the logic requires a bit more explanation, and is related to the pre-processing that is done for most 5.1 and 7.1 source material.

Chris

[jacksonbart]

I was told by a klipsch support rep that if my seating was close to the back wall or against the back wall I should use bipole speakers. If my seating was 3ft or greater from back wall I then should use direct speakers. True or untrue?

Klipsch support lies 30% of the time (joke). So if you call them back and ask them the same question 9 times.