SDA in HT - Food for thought

deq15

On another forum I read this - the question isnt mine and I lay no claim to it but i thought you all would like to follow along here...

"In my mind there has never been a question that SDAs are great for 2-
channel music, but there is some discussion regarding their
suitability for home theater and multi-channel music. I posed this
question to Matthew Polk via Ken Swauger. "Below is my original
question and Mr. Polk's response."

[ Original question ]

"A very knowledgeable audiophile suggested to me that SDA speakers are
not really well suited for home theater if a center channel speaker
is used. As the name Stereo Dimensional Arrays suggests, these
speakers were designed for stereo applications before multichannel
movies and music was invented. In addition, it would seem logical
that sounds coming from a center channel speaker could adversely
counteract the signals coming from the SDA drivers and smudge the
imaging.

Before this question arose, I remember listening to music with and
without the center channel. At the time I though the 2-channel
version sounded better, but I attributed that to the fact that my SDA-
1Cs were simply better speakers than my f/x500i. Sitting in the
sweet spot I was amazed by the realism of the phantom center
speaker. I had to literally put my ear next to the center channel
speaker to confirm that I hadn't inadvertently left it turned on.

I'm thinking that because the dialog is so important in movies, and
to accommodate other listeners not seated in the sweet spot, that I
should continue to use the center channel for movies and accept some
degradation of the imaging. With multichannel music, which is
usually a solitary listening experience, I'm thinking that I should
turn off the center channel, but leave all other channels on.

Obviously I will continue to experiment to determine whether my
untrained ears can hear any change in imaging, but it would be
wonderful if Mr. Polk could share his thought on the subject of how
to best to use the SDAs for multichannel movies and multichannel
music. When I move I plan to build a new home theater. Would Mr.
Polk recommend other Polk Audio speakers for a dedicated home theater
and retire the SDAs to an other room for music? "

Here is Matthew's reply:

" Ken -

[the] impression that the phantom center image sounded better than
the actual center channel shared by many listeners and is not limited
to SDA systems. The primary reason for this is that the center
channel signal is usually a band limited signal or is otherwise
degraded in the decoding processed as compared to stereo
reproduction. Center channel quality is notorioulsy poor in Pro-
Logic. In Dolby Digital the center channel has the potential to be
of excellent quality but the recording techniques used to improve
voice intelligibility often degrade the signal from an absolute
quality point of view. However, things seem to be improving. When
Pro-logic is played back in stereo some of the steering artifacts of
the processing are eliminated. When Dolby Digital is forced to
stereo it is frequently an entirely different track on the disc
having an entirely different mix. In addition, there are certain
psychoacoustic advantages to phantom center images which arise from
the way we perceive the direction of sounds.

As regards SDA, multi-channel is actually one of the best uses of the
technology. However, it is not as dramatically different as it is in
a 2 channel setup. The big benefit of SDA in multichannel systems is
its ability to create strong lateral images far to the left and
right. A normal 5.1 speaker setup cannot do this. As Larry has
noticed, a stereo pair of speakers can create a very convincing
center image when the listener is seated facing the speakers, but if
the listener turns 90 degrees to one side, the phantom image
collapses. Because of the way we hear the direction of sounds two
speakers in front of us will create a phantom image between them, but
two speakers located left front and left rear will not create a
phantom image directly to our left. This is the situation in a
surround sound system and is the reason why surround effects that
move from front to rear tend to collapse towards the listening
position as they move from front to back. An SDA system, however,
has the ability to create strong lateral images and, with SDA
speakers front and rear you can actually pan the image from front to
back at a realistic distance from the listener.

-msp"
I hope this is helpful information.

Regards, Ken, Polk

Larry Chanin

Hi deq15:

Thanks for the interest.

I also posted Mr. Polk's response to me earlier in this forum in response to a small controversy regarding the suitability of SDA type speakers in a home theater.

Here's the thread:

SDA-2 in a home theatre setup ?

Anyone using SDAs in the front and rear of a 7.1 home theater?

Larry

deq15

Larry - this was MOST likely THE one you posted on yahoo - hope you dont mind...

Larry Chanin

Hi deq15:

No problem whatsoever. As I said, I'm glad you're interested enough to post it.

I'd like to get some feedback from someone who is in a position to comment first hand regarding Mr. Polk's observation.

An SDA system, however, has the ability to create strong lateral images and, with SDA speakers front and rear you can actually pan the image from front to back at a realistic distance from the listener.

Since SDAs in the front can occasionally throw sounds beyond the spacing of the speakers wouldn't it be interesting to hear this effect panning to the rear? I imagine in an ideal situation, it might be possible to hear sounds panning outside the confines of the walls of the listening room. Wouldn't that be a kick!?

Larry

hoosier21

Always wanted a complete SDA theater, but I have doubts about the front to rear panning, I have doubts the SDA effect works with your back to it (like the rears would be). So to me any SDA speaker would be wasted anywhere except in the front channels. except for timbre matching.

Larry Chanin

Hi hoosier:

You make an excellent point. Our hearing from the rear is limited.

Also even if this wasn't a problem, this hypothetical SDA panning effect that I'm describing should only work where the rear pair of surround speakers are in stereo. This would mean that in a 5.1 setup the surrounds would have to be mounted in the rear rather than the sides. For 7.1 channel setups I believe that there are only two processors that deliver stereo surround back channels, the Lexicons and the Meridian processors.

So I suppose more accurately my question to the membership should have been, "Does anyone have SDAs in the front and rear with stereo rear surrounds?"

Thanks.

Larry

marvelous

I have the denon 3801 receiver. It has 7 & 5 channel stereo. I also have SDA 3.1tl in the front and rear. I am in love with the sound. The SDA effect does work in the rear. It may be an overkill but I also have CRS and my back surround. When I am playing the 7 channel stereo I am in another world. It even sound good when watching movies or audio dvd with dts. I also switch to 5.1 when watching some movies. I have a great deal of flexability. I agree with the SDA quote!

Larry Chanin

Hi marvelous:

The Denon receivers are excellent and I'm sure that your setup sounds great. No insult intended but, I'm pretty sure that although they have amplification and connections for two surround back speakers, they are not delivering a stereo signal to them. Since the signal to the surround back speakers is mono, I don't think it is possible for you to experience the SDA effect that I am attempting to describe.

Unlike conventional speakers that place audio images between the speakers, occasionally with the right type of stereo signal, SDA speakers can project an audio image outside the speaker spacing. In my room with SDAs in the front that makes the audio image sound like it is coming from the front of an adjacent room, beyond the walls of my home theater. Frankly, I don't hear this often, but when I do the effect is quite startling.

Despite my wishfull thinking regarding experiencing a similar rear SDA effect, I think that hoosier's comments about the limitation of our hearing for sounds coming from the rear would make the occurance of a rear SDA effect very rare. Since I hear the front SDA effect on rare occasions, it would likely be very rare where the conditions were right to sustain the effect whereby it pans front to rear and sounds like it is coming from outside the room(assuming I had SDAs in the rear). I have a Lexicon MC-1 processor that does provide stereo surround back signals, but my room layout would make it difficult, although perhaps not impossible, to mount a pair of CRS SDAs on the rear wall.

By the way, I'm sure nobody on this forum thinks CRSs are overkill for your surround back speakers. Personally, I don't think you can have too many SDAs.

Larry

DarqueKnight

Originally posted by hoosier21 So to me any SDA speaker would be wasted anywhere except in the front channels.

Hoosier, I used to think the same thing. I was running RT 55i's for rears with SDA 1C's for fronts and a pair of CRS+'s for center speakers. Out of curiosity, I replaced the RT 55i's with one of my other CRS+ pairs. I was mainly interested in seeing if I would notice much of a timbre match. In addition to a seamless front to back timbre match, I also immediately noticed more of a sense of being "enveloped" in sound.

Next, my mind started wondering what larger SDA's would sound like in the rear stage. Fortunately I had a spare pair of 1C's. I put on the openning battlefield scenes from Terminator 2 and the lobby gunfight scene from The Matrix and I immediately knew I couldn't go back to small speakers in the rear stage. It was like being surrounded in a 360 degree sphere of sound.:D

Overkill? Yeah, maybe, since most DVD's don't have a lot going on in the rear channels. For those scenes that do have sound pumping out of all channels, the effect is awesome. I have the interconnect cable connected on all three sets of SDA's.

The only thing I don't like about my setup is the bulk of the SDA's, particularly the CRS+ pair above my TV. I have been trying to talk myself into replacing the SDA speakers with the smaller, sleaker, LSi series, but I am not quite ready to give up the sonic impact of the SDA's.:cool:

rlw

Front and rear.

I had been running RT3000p's as rear surrounds. Moving to the SRTs - even without the best setup - was an incredible upgrade in terms of realism of image placement and a sense of space.

F1nut

raife1,

Just my opinion, but I don't think your CRS+'s look too big. In fact I'd say your set up looks awesome.

HBombToo

Agreed F1.

raife1 i'd drink a Beer and watch a film whiithya nyday!

Nice System!

hoosier21

Raife1 great looking set up. Hope my is put together soon.

Drinking and typing don't go together "Hope to put mine together soon."

marvelous

The sda HT sound is great.I would never change to anything else. Everyone that listen to my setup is left breathless. I am very please, however at time I do think about replacing my definitive tech 2300 center with another pair of crs. For now I am a very happy guy!