THX Monopoles or dipoles for rear speakers?

[Lawrence_Chiu]

I am considering the Klipsch THX Ultra2 speakers for my home theater. This is a 7.1 setup.

I wanted to use the KL-650-THX for Left/Center/Right. This is a monopole speaker.

Also KL-650-THX for Left-rear/Right-rear. Same as above.

And KS-525-THX for Left-side/Right-side. This is a dipole speaker.

But my home theater designer hates the monopoles for the rear. He says I should go with more dipoles instead.

The designer says that using monopoles in the rear would cause listener fatigue, since the 2nd row is only 3 feet away. As a result, he says that no one would want to sit in the 2nd row. I asked him if I could mount the rear speakers higher, so they won't be pointing directly at the viewers, and he says that is not good either because monopole speakers does not have good off-axis response. He says I should go with dipoles in the rear too. He says monopoles are useless in the back because no one mixes directional sound for the rear channels for either movies or music.

I was wondering if there are any opinions about which is right. On the one hand, you have THX saying one thing (which is rear monopoles side by side), and on the other, a professional designer saying the opposite.

I'm so confused.

[Darren]

mOOn sounds like this one is set up for you!

I use the dipoles for surrounds, but only have a 5.1 set up and like the wider coverage. Not sure in a 7.1 setup.

A few months ago, mOOn was playing around with these options, but I was out of touch for over a month and don't know where he ended up.

[j-malotky]

I hate to say this, but, I think you should start to look for another HT designer. Listener fatigue - my hairy white butt!

I also prefer monopoles for surrounds, and with only 3 feet between your first and second row, monos should work well.

Usually the second row is only ocassionally used in most HT's, so the sides are set up for first row optimization, but if you want both row optimized, I would mount them 6-8" behind the first row head loacation. With only 3 feet between the two rows, this should sound great.

Mount them high, to give a good 3D sound, and angled down so your listeners get the best performance of your monopoles direct sound.

If I remember, M00N was having problems with his 3rd row and wanted to add a second set of sides, he abandonded the second set I believe. He has a very narrow room too, like 10' wide which makes it very hard to work with.

Where are you located? There are a lot of people here who do consulting and you may find one here to hook up with.

Ohh, I forget to mention ...Welcome to the Forum. Best of luck on your project.

JM

[easylistener]

Go monopoles. That is the only why to go.

[jdm56]

I would tend to agree with your H/T designer if your system is primarily to be used for HT, and not music, but ultimately, it's your call. You will have to live with it, so you don't want to be second guessing yourself. Listen to his best advice, then do what you dang well please! If multi-channel music is the thing you want to optimize, then do identical speakers all around! But even then, dipoles in back would have some advantages.

And btw, SACD is currently a 5.1 channel medium. There is no back surround - yet. DVD-A titles can have 6 channels, but I don't know if there are many that do, or if there is a concensus as to how they are used.

[T2K]

I suggest you talk to several people that have experience installing many HT systems in a variety of room sizes. One of the keys, IMO, is the distance from seating to speaker location. Good luck and welcome.

Keith

[Lawrence_Chiu]

Hey all, thanks for all the advice. I found an interview with John Dahl from

THX that says:

"How one places the speakers depends on a couple of

things. Our prime recommendation for consumers using

components with THX Ultra2 Certification and looking

for a single speaker arrangement for cinema and music

is the following: two dipole speakers to the side and

two direct radiators in the back touching side by side

with the ASA circuit engaged at a distance less than

one foot. (Figure 2). The ASA circuit takes the single

back channel signal and using the two speakers makes

it sound like one timbrally correct wall-to-wall

sound. In THX cinema mode, the balance is as recorded.

In THX Music mode, the sound is biased toward the back

to mimic the ITU recommendations for 5.1 speaker

placement in music recording situations."

...

"With any of these systems, be careful that no one is

sitting directly on axis and close to any of the

speaker faces. Loud on-axis sound above 500Hz is very

tiring to listen to when it's constant and outside of

the field of vision."

http://www.audioholics.com/FAQs/THXp2.html

What I am thinking of doing, is going with the

monopole rears, but putting them on a "turntable".

Then, they can either face forward (direct radiating),

or I can spin them 90 degrees (back-to-back) to face

their respective wall (dipole operation). Do you

think this idea will work?

[Joe Bagadonuts]

There is no higher authority on the subject than John. One thing that has not been mentioned, and that John did not go into detail on is what "sound" the THX Ultra 2 speaker configuration he describes will render. A well installed U2 system in a room that is reasonably acoustically friendly will do two very different things for THX Cinema (especially EX), and THX Music. If the back hemisphere of the room acoustically permits the system to render a symetrical surround field, then cinema-mixed sound tracks will be very enveloping, smooth in pans, and directional when required, especially to the back wall. In THX Music, the ASA processing creates a very convincing rear surround image on each side at about 120 degrees (the ITU music standard). This is not described often, but is the designed effect.

Placing the monopoles close together in your application will give the best results. Now, we are assuming that you will be using a THX Ultra2 receiver/controller, right? If not, forget everything that John and I have said. If you are using a THX Select receiver, then you are better to use two of the dipole surrounds, again up higher. They should be spaced about as wide as your central seating area, presuming two to four seats. This is the THX recommendation...but room shape and size can greatly affect what is chosen for the THX surround speaker array. You don't hear it much, but the THX training covers many room-driven possible scenarios. Your best bet is to make a sketch of your room, or supply a plan with notes to a local THX designer/dealer. He will be glad to look them over, and often they seek the advise of THX (usually John) which is a bennie of their certification.

Hope this is helpful. When you get your Ultra 2 system in, let us know how it sounds.