...commercial movie theaters don't use them and employ front-firing speakers instead?

The next time you're at your movie theater, remember to take a look - all the ones I've been at here in Southern California use multiple, front-firing speakers evenly (or so it seems) spaced along the side walls.

Furthermore, the di-pole designs seem to create a sonic hole, or void, directly in front of them (where you, the listener would be sitting) while the bi-pole design seems to rely on focusing the lower and middle frequencies directly at you but then using two tweeters pointed in opposite directions to disperse the high frequencies away from you, at opposite ends of the spectrum. The Klipsch WDST design seems to direct the complete frequency pattern away, at close angels, from the listener. In the end, both "pole" designs seem to rely on "reflecting" sound - via the listening room's physical properties (i.e. walls)  while the Klipsch WDST design directs the sound away from the listener at two distinct, albeit close, angles. Any way you cut it, this seems to go against the entire Klipsch concept of using horns to control the frequency dispersion directly towards the listener in a focused pattern. 

That, therefore, brings me to this point: Whenever I think about "reflected" sound I think about Bose marketing their products throughout the 70s and 80s with their mantra that their reflected sound is more natural and therefore better. Needless to say, I've never heard a Bose system utilizing a "reflected sound" dispersion come even close to sounding "live" or "natural." In fact, this just seemed to make their cone-driven speakers sound even worse then a "conventional" cone-driven speaker because they were pointed away from you, and since they were all naturally low in sensitivity to begin with, facing them away from the listener, as per Bose, made them seem even more muted and even less efficent and even less realistic.   

I guess what I'm saying is that the whole surround sound concept using bi-pole, di-pole, or WDST speakers seems to stand in contrast to PWK's philosophy on controlled, directed sound towards the listener via his horns, not to mention that I've yet to sit in a movie theater that utilized anything rather then direct-firing, non-reflecting surround speakers faced directly towards the audience...and I live in the most densely populated section of the United States with lots of new construction to boot, so a lot of the theaters I've been in are pretty new.  

It begs the question as to why one should use bi-pole, di-pole, or Klipsch WDST for home theater use when the goal of the home theater is, after all, to re-create the commercial theater experience in your home?

I've thought about this for quite some time but never got around to asking the question openly on the forum; here's my chance...hope it pays off.

Thanks,

H2G 

Postscript: I heard or read that Klipsch professional cinema products were being used in approximately 1/3 to 1/2 of all new movie theaters being constructed today....or something to that effect. I don't know if this is true or not, but I just checked the website for their professional cinema products and low and behold, there are no bi-pole, di-pole, or WDST surround speakers to be found, only the direct-firing KPT-1201, KPT-8001, and KPT-250.  

First time I heard rs-7's, after hearing rf-15's, kg1's, rf-7's, rb-75's, rf-35's, rc-3, kv-3, heresy, cornscala, etc etc. - I was blown away, they were terrible. I imagine it would need to be 10 feet away from the nearest listener to be bearable; and it that case, not suitable for dvd concert material, just movies.

 Good observation, I always compare my ht "sound" to theaters, and the obvious differences in speaker layout.

I've been in several bad theaters. One, the center channel was way to the left of the center of the screen and drove me nuts.

 In the theater I saw transformers, there was one sweet lfe effect with almost a sine wave sweep down to very low, and their sub was just torn to shreds, bottoming, all kinds of mechanical noise, I laughed out loud.

Maybe to create non-localizable surround 'effects'? To mimic multiple direct radiators?

Keith

The professional cinema is also using a lot more surround speakers too...

I'll have to dig up a few articles as the concept of wide dispersion surrounds was discussed in it. I believe the intent was to create a more full surround stage and to reduce some of the distracting effects that would otherwise call your attention to the rear of the room (when the movie director would rather have you concentrating on the film in the front of the room).

I personally dislike them and strictly use front firing speakers in my HT probably because there is no Heritage version of them, but I suppose where room is limited and you want that echoey effect there is a place for them.  I can see them being used as the rear effects/centers but nothing more.

As you stated all the theaters that I have been to use an array of multiple front firing speakers and I have never been disappointed with the placement of the effects. 

Those folks that use them as their primary rear speakers don't know what they are missing by not having fully capable front firing speakers in the rear.

Different strokes for different folks I suppose.

WDST for side surrounds only... Direct for the rears..

I AGREE!  If I could of fit a la scala as a side surround and somehow, I would of.  I think a lot of us would. You would have to maybe cheat it to spray some... hmmm how could I do that?? From a timber standpoint, this would be the perfect match of course too.

Can u imagine NINE LA SCALAS??  hehehehehe

I am quite happy with the THX 525's on the side walls... 

I think more so in most anyones HT, the side sounds good sprayed, because it gives you "depth" too.  Most rooms are rectangles and every speaker fits pretty good except the side ones.. Grrrrrrrrrrr   (Which should be to your direct side to 20 degrees behind you too.) Now people with multiple  seats on different levels  benefit from multiple side surrounds  that "may be" direct radiators.for better resutls to make it sound better.  Ask mOOn...   Most of us with HT seats need the sprayed sound in my opinion to give the depth necessary.

My 2 Cents 

 As a native of Oceanside and now a resident of New England, I can make but one tangiental comment to the direct-reflcting concept; "No highs, no lows..get Bose".  When I was growing up as a kid in So. Cal  I was used to open airy sound from speakers, when I first came east to go to college someone had Bose 901's..every one in the dorm thought they were the greatest things in the world...I thought someone had stuffed toilet paper in them.  When folks walked into my dorm room, where I had a pair of Heresy's they were amazed.   

 Forutnately as a collegiate wrestler I was able to kick people out as well as invite them in.  Now as a grownup (sort of) I have a pair of RF-52's and an RC-52, I love it.  I sitll keep a pair of heresy II's in the room, romanticism..

"but I suppose where room is limited and you want that echoey effect there is a place for them. "

There is nothing inherently echoey in the speakers at all. If you heard that you were hearing the room not the WDST surrounds.

The reason for the WDST is very simple... a single horn on top of a direct radiator results in a speaker with  a very uneven coverage pattern. The woofer is basically omni-directional at low frequencies (or 180 degrees if wall mounted) yet the horn has a controlled/narrowed dispersion at the top end. The coverage of the speaker is uneven which means what the speaker sounds like at different seating locations varies quite a bit. Surround setups typically need to have good coverage over a wider seating position then the fronts as they are usually closer to the seating positions and for those with multiple rows there isn't a single sweet spot for sides to aim at.  

The two horns in the WDST surrounds are run in phase. They are 'aimed' so that they have roughly 180 degrees of horizontal coverage... to match the coverage a wall mounted woofer is going to have. That mean they sound is more even over a  larger listening area. That same reason movie theaters have an area of surrounds.

As far as 'direct/reflecting' if one looks into Bose speakers they will see they directly aim drivers to bounce off the walls. The WDST doesn't do that, Remember, the horns control the dispersion. The horns are basically aimed so that their patterns converge on axis and the other edge of their dispersion is sort of shooting down the wall, not aimed into the wall. Not the same thing.

Shawn 

Maybe to create non-localizable surround 'effects'? To mimic multiple direct radiators?

Keith

_______________________________ 

Don't know much to say about this one expect that there has to be localization to the sounds because you have separate channels (Left Front, Center Front, Right Front, Right Surround, Left Surround, Right Rear and Left Rear) and the engineers direct the sounds on the soundtrack to the appropriate channel(s) in order to give the listener/audience the impression that they're immersed in the action and that although the screen is only two-dimensional, the soundtrack places you in a real-time three-dimensional environment by enveloping you (via precise locations) with multi-channel sound from the various speakers strategically placed around you. I guess what I'm saying is that I see (in my layperson's persepective) that the engineers want the sounds to be localizable, i.e. noticeably coming from the front (right, center and left), rear (left and right), left side, right side, etc...       

You make sense with the notion of those "pole" and WDST speakers trying to mimic multiple, direct-radiating surrounds that are found in the theater. This might have some traction, but it still seems to take home theater on a different course then what's found in commercial theaters. If there's truth to this, then the only way to "fix it" for the home theater environment would be to add even MORE speakers - direct radiating surround ones - on the left and right walls, and that doesn't seem feasible considering how small most home theaters tend to be. 

Again, I'm just throwing darts here... 

Shawn, thanks for the input. I understand what you're saying about the WDST theory, but aren't most home theaters pretty small inasmuch as only having one typical sweet spot (where the couch and/or lazy-boy-type chair(s) tend to be) wherein the listeners generally sit? If you follow the THX instructions from the website on the placement of the surround speakers, that'll mean that they'll be placed exactly to the left and right of where you'll be sitting in your home theater, assuming that you have it set up like the THX website with your seating area more or less in the center of the room. With that being the case, the WDST format will have you sitting off axis of the the two horns that are shooting 90 degrees each but converging at their ends in order to form the 180 degree arc, yes? 

The WDST design surely seems better to me then either the bi-pole or di-pole but still seems to be be coming up short because it appears to be an approximation of the commercial theater setup. The immediate, major difference I think everyone can see between home theater and commercial theater speaker placement is in the surround speaker category. It seems reasonable to me to say, therefore, that until home theaters utilize direct-radiating surround/side speakers (be they only one per wall or multiple units, depending on the size of the room and/or listener/audience location within the room) then they'll continue to come up short of the real experience, or real deal, irrespective of what audio manufacturers, Hollywood studios, or THX may say.

- H2G

PS - The WDST, bi-pole, or di-pole surround theory must not hold water in a performance or professional/commercial sense, because if it did, the theater  conglomerates would realize a reduction in their newly-constructed theater costs by replacing the multitude of direct radiating surround speakers with fewer speakers of a WDST, bi-pole, or di-pole design. In today's world, every company's trying to pinch their dimes tighter then ever on practically every level (except on its Officer or Board compensation it seems) so I imagine this notion has already been examined thoroughly and has since been rejected.

Thanks to Masterxela, Frzinvt, and Indyklipschfan for chiming in and Dr. Who, I'd like to be able to read those papers if you can find them and post them.

Best,

H2G 

"but aren't most home theaters pretty small inasmuch as only having one typical sweet spot (where the couch and/or lazy-boy-type chair(s) tend to be) wherein the listeners generally sit?"

All of my systems in several different rooms have had multiple seats and required fairly wide dispersion to cover all the seats.

Put a couch up against a back wall. Now put two surround speakers at 110 degrees from center. A speaker with limited dispersion on the top end (like something like a RB5) won't have a coverage pattern that covers all the seats on the couch.

"If you follow the THX instructions from the website on the placement of the surround speakers, that'll mean that they'll be placed exactly to the left and right of where you'll be sitting in your home theater, assuming that you have it set up like the THX website with your seating area more or less in the center of the room."

I have two rows of seating. Second row is on a riser. Di-poles were created by THX.

"With that being the case, the WDST format will have you sitting off axis of the the two horns that are shooting 90 degrees each but converging at their ends in order to form the 180 degree arc, yes?"

Which makes you on axis. That is the point of WDST. It has wide coverage... you are on axis over that 180 degrees.

"The immediate, major difference I think everyone can see between home theater and commercial theater speaker placement is in the surround speaker category. "

I'd say room size is a little different too. In the theater with the array you get the coverage needed.

"It seems reasonable to me to say, therefore, that until home theaters utilize direct-radiating surround/side speakers (be they only one per wall or multiple units, depending on the size of the room and/or listener/audience location within the room) then they'll continue to come up short of the real experience, or real deal, irrespective of what audio manufacturers, Hollywood studios, or THX may say."

I have had it both ways (and with di-polars and bi-polars too) and the WDSTs work out very well. If you are coming up short compared to the theater you have work to do. I'm not coming up short...

Shawn

I believe you are pretty close to the mark in all your statements. I number my statements for purposes of discussion.  Not to be preachy.

1) A starting point is that surround is not quad sound.  We're not trying to create a rear channel(s).  Maybe everyone knows that but newcomers to surround seem to want to put surrounds in the back.

2)  Surround channel sound is a) suppose to come from everywhere in the room and b) not come from a single source which our ears can localize.  The last means that an ordinary speaker on each side wall will not do very well. 

3) What is fed into the surround channel should be room revereration from the hall, ambient sound like chatter in a restaurant, or ambient outdoor sounds like birds chirping.  Sometimes bullets wizzing.

4) Sometimes airplanes coming out of the screen or toward the screen (our reference in viewing) is also sonically presented.  Then there are bullet wizzing too. This sort of thing is the somewhat rare situation where there is interplay (panning) between the ambient and mains.

5)  As you point out, movie theaters use multiple speakers.  Mostly on the sides with a few at the back.  Per 1).  Note they are usually aimed over the audience rather than directly at them.

6)  But, there ARE multiple speakers in theaters for surround.  Therefore the surround sound is spread out and difficult to localize as one source; 'cause it does not come from one source.

7) In the home setting, there is the problem that most people don't use six or nine surround speakers.  Of course that would work.

8)  Looking at 2) again, we would like a speaker which a) paints the room walls with sound very well and therefore has broad dispursion (so we have a lot of reflections from everywhere) and b) does not direct sound (at least relative to dispursed sound) directly to the listener.  The parenthetical is important.  Some of this is relative levels at the listener. 

9)  Most direct radiator speakers have a narrowing polar projection as frequency goes up, so they are not good at wide dispursion and do project in a direction, probably toward the listener.  Note, multiple speakers in theaters avoid this by just having so many.

10) As you point out, dipoles (two drivers in a box facing left and right fed out of phase, or one without a baffle) have the the characteristic figure 8 polar pattern.  If the listener is in the null, no sound (or, actually, two out of phase signals) gets to the listener. 

All that is heard is sound which has been directed, otherwise, into the room and bounces off walls.  I understand that the first experiments with surround at home were done with Magnaplaners (sp) with the listener in the nulls. 

11)  Dipoles can work very well, if the listener is in the null.  It makes for a small sweet spot (say anti-sweet spot).

12)  The Klipsch wide dispursion uses two identical 90 degree horns fed in phase to make sure there is as much dispursion as possible.  I think there is no null or even a roll off in the combined pattern at the listener.  Again this is a relative thing. The good part is that placement of the speaker and listener is less critical. We are trying to paint all the walls with sound.  The small direct radiator is too small to be directional at low freqs, so it is wide dispursion too.

13)  There is rumor that Klispch wide dispursion technology will be used in movie theaters.  Theater owners, like home owners, would rather buy fewer speakers.

14)  Reports on the classic Bose 901s (?) are pretty much as you report.  For the benefit of others here, they had eight speakers at the rear of the box and one in front.  Some equalization to be put in the amps tape loop circuit.  And they were meant to be put on stands well out in the room.  They did put up a strong ambient field which was not common in those days.  But it was mostly a matter of special effects via the speaker.  Equalization may have helped what was otherwise an system with limited response.

15)  There is a humorous joke about this.  Mr. Klipsch and Dr. Bose see each other on opposite sides of the street.  Klipsch cups his hands in front of his mouth (a horn) and says in a soft, effective, voice "Hello Dr. Bose."  Dr. Bose turns around 180 degress and shouts, "Hello, Mr. Klipsch."

Gil

 "15)  There is a humorous joke about this.  Mr. Klipsch and Dr. Bose see each other on opposite sides of the street.  Klipsch cups his hands in front of his mouth (a horn) and says in a soft, effective, voice "Hello Dr. Bose."  Dr. Bose turns around 180 degress and shouts, "Hello, Mr. Klipsch.""

I've always heard that the other way. Dr. Bose saw PWK and cupped his hands to say Hello. PWK turned his back to him facing a wall and said Hello.

Shawn