question about 5.1 vs quadraphonic simulation

[DVDdoug]

"But are connected anti-phase"

I think that's being misinterpreted...

The out-of-phase information in the recording comes-out of the rear. You also get left-only and right-only (the same in both rear speakers). The in-phase information (usually including centered bass and lead vocals is eliminated).

If you do a simple subtraction, the rear waves coming out will be in-phase with the right OR left. Dolby shifts the rear information by +90 and -90 degrees to get the 180 degree phase difference, so when decoded the front and rear are only out-of-phase by 90 degrees

I mentioned Audacity in another thread and I told you how to get that "vocal remover" effect which would be sent to the rear. But that's just as a demonstration/experiment because it makes a mono file. The mono file would be OK for the rear, but you want the stereo-front at the same time.

So what if I sum the L/R for the rears?
You'll get mono (dual mono) out of the rear.

 

[Chrispy]

This is not just flipping the phase in the rears and lowering the volume, right? I guess I’ll just play all my speakers at 0 phase to keep things easy, but I like lowering the volume of the rears by 3-6dB. They are not the same speakers front and back.

Are they of same sensitivity?

 

[olds1959special]

Are they of same sensitivity?

They are powered speakers, Dynaudio BM5As in front, Yamaha MSP5’s in the back.

 

[Chrispy]

They are powered speakers, Dynaudio BM5As in front, Yamaha MSP5’s in the back.

So from a level matched output, you just prefer the second stereo pair to be of lower volume?

 

[olds1959special]

So from a level matched output, you just prefer the second stereo pair to be of lower volume?

The rears are a bit further back and I’m much closer to the front speakers. I’m just trying to see if there’s a way to make the rear speakers useful to me. I like the ambience of having sound come from the rears. So the Hafler thing would be perfect but I would need a way to accomplish this.

I listened to stereo music upmixed to 5.1 and when I listened to the rear speakers by themselves I could hear the “Hafler” sound that I’m wanting at home.

I guess I could get a miniDSP SHD since it’s balanced.

In the mean time, for the rears, reversing the phase, summing to mono, and the slight added delay (from the drift correction) seems to give me a little bit of that ambient feel. I’m not sure what else I can try.

 

[krabapple]

Why are you doing this?

If you're just trying to simulate surround sound from a 'stereo' source, use an upmixer.

 

[Chrispy]

The rears are a bit further back and I’m much closer to the front speakers. I’m just trying to see if there’s a way to make the rear speakers useful to me. I like the ambience of having sound come from the rears. So the Hafler thing would be perfect but I would need a way to accomplish this.

I listened to stereo music upmixed to 5.1 and when I listened to the rear speakers by themselves I could hear the “Hafler” sound that I’m wanting at home.

I guess I could get a miniDSP SHD since it’s balanced.

In the mean time, for the rears, reversing the phase, summing to mono, and the slight added delay (from the drift correction) seems to give me a little bit of that ambient feel. I’m not sure what else I can try.

Use an avr with pre-outs?

 

[olds1959special]

Why are you doing this?

If you're just trying to simulate surround sound from a 'stereo' source, use an upmixer.

I would need an interface with 6 output channels right? And a center speaker…

 

[Chrispy]

I would need an interface with 6 output channels right? And a center speaker…

Like an avr? Good upmixers will adjust for lack of particular speakers in the mix, whether a center or sub....

 

[olds1959special]

Use an avr with pre-outs?

This would be the easiest way to upmix to 5.1. The problem I think is that receivers tend to be very big and bulky and there isn't always enough room in a desktop setup for a receiver.

 

[Chrispy]

This would be the easiest way to upmix to 5.1. The problem I think is that receivers tend to be very big and bulky and there isn't always enough room in a desktop setup for a receiver.

Well there are the slimline Marantz models....but wasn't thinking desktop, don't use desktop stuff in retirement Then again a 5.1 system at a desk didn't have much use for either.

 

[olds1959special]

I am now using a second interface (with drift correction) to output sound from rear speakers/subwoofers, without using the Hafler circuit setup. I simply reverse the Left and Right since I'm facing the front usually.

But I am also experimenting with reversing the polarity on the rears, and I think it sounds okay and gives things a spacious effect. It seems this is not a normal practice, but interestingly I'm not sure if it's better or worse this way, at least going by ear. The nice thing about this is how the sound seems to combine in the room. There is less frequency build-up and more of a diffuse sound.

This led me to re-read this thread but my ears can't really tell me why having the polarity of the rear speakers/subs in my setup is such a bad thing.