Dipoles and Dolby Digital

[super8]

Hi while shopping for some bookshelf speakers for my sister I came across a pair of ex demo Mission M77 DS speakers for sale.

Currently running with image 404's and the matching centre for front of house and Tannoy M1's for rears which were left over from the last upgrade spree. Hooked up to an A1.

I haven't tweaked my system in a while and couldn't remember whether dipole and DD/dts were a yay or nay?

[michael w]

Nay on dipole rears in my book.

One of the main reasons for DD/DTS employing full range, discrete rear channels is to improve rear stage imaging and L-R/F-R panning, aspects of reproduction that demand point source dispersion.

Dipolar rears diffuse imaging and so dilute any gains made by using discrete rear channels.

There are some who say diffusion is in fact a good thing because you can't pinpoint the source of sound but that it pure bollocks with DD/DTS.

With a speaker array properly setup for DD/DTS that is not a problem.


cheerio

[Senator]

Can open - worms running everywhere!

Having used both dipole and direct radiating in my HT, I would have a tendency to prefer dipole. The overall immersion/expansiveness of the soundfield to me outweighs the "full range" benefits of direct radiating.

Sen

[Boris]

The layout of your room is a big factor. I think dipoles are recommended for THX rooms ie. rectangle with TV in the centre of one of the short walls. They need to be mounted on the side walls, above the listening position, beside the listener.

This wouldn't suit many real world situations eg. TV in corner, or open plan (no side wall). In this respect, I think directional speakers are probably more flexible.

If your room layout is OK for both, then it just becomes a matter of personal choice - michael vs senator. Neither is wrong, just different preferences. If you try and over-analyse it, dipole may suit some films and directional others. Then there's music DVD's. I vaguely recall reading about a speaker that could be adjusted either way - maybe? Someone else may know more.

As Senator said, worms all over the place! One of those grass is always greener scenarios too I think. If you have good quality rear speakers and have always been happy with them.....just leave it at that!

[HiFi Si]

I tried both with my Lexicon processor with Logic 7 processing.

I setteled for bipolar sides (all drivers operate IN phase) and this seemed to offer the best of both worlds. In a recent US HT mag (can't remember the name), subjective tests were done between dipole and monopole, and most people favoured dipole.

I agree that with discrete channels, more localisation is a good thing, but I feel (and have heard) monopole offering too much at the sides.

To add confusion, I used monopole rears as well, so I ended up with bipole sides and monopole rears.

It sounds fantastic, everyone should get a decent 7 channel processor!!

[michael w]

Not everyone can afford a Lexicon.

:p

I recall some Citation speakers of years past could be operated as mono or di-pole and some Denon AVRs had separate mono/di pole rear drive as well.

I'm unconvinced by dipoles for DD/DTS, like those simplistic Hafler matrix type surround decoders you end up with an immersive rear field whether it's on the soundtrack or not.

Not my cuppa tea.
I just want to hear what's on the disc , unembellished.

cheerio

[Michael Jones]

I'm surprised Max hasn't popped into this discussion - he's usually very vocal on dipoles vs monopoles for surround :D

I have Energy RVSS surround sound speakers. They are engineered to be dipole above 400Hz or so and bipole below that.

I know that this might sound like an oxymoron, but my Energys seem to give me both precise imaging anddiffuse sound at the same time.
:confused:

[Slippery]

Now that is interesting. I've currently borrowed a set of Dipoles to see how they go compared to my "normal" rears - Monopole.

Results surprised me - Dipoles better for live music DVD's, and the Monopoles are better for movies.

My issue is I watch about 50:50 so the RVSS surrounds sound like the Bees Knees!

Slippery.

[maxcat]

Against my better judgement I'll make the following point:

The dipole/direct radiator issue is actually not about speaker types. It's about who has control of the soundtrack - you - or the sound engineer who created it.

Once you identify what you are trying to achieve and recreate, the rest is simple.

In my view you have two choices:

1) The soundfield of the movie theatre

2) The soundtrack

My view says the job of the system is to recreate the soundtrack accurately as intended and as dictated by the sound engineer.

This approach is identical to traditional two channel stereo: the objective is to retrieve *without alteration or colouration* the information that is on the soundtrack.

This analogy still works for me: An envelope is to a letter what the HT speaker system is to a soundtrack. It is merely a means of delivery.

If your HT system interferes with the signal as created by the soundtrack engineer, that is distortion.

Dolby is in no doubt about the issue::

"Dolby has found by using Dipoles at home in a discrete digital system gives you too much diffusion on what is a completely
discrete signal. We have found that dipoles disperse the image such that it is utterly directionless, seemingly everywhere at
once which is not desired because the mixer has control of the signal placement when he does the mix ." (Mix magazine on "Multichannel replay" as taken from the Dolby press conference at AES).

DTS also subscribes to the same view: it's about recreating the engineer's soundtrack, complete with detail and spacial cues.

It's not (and never has been) about recreating the sound of an acoustic space (a theatre). It is about fidelity and accuracy to the source. The sound engineer has done the work and provided all the information needed - it's over to the system to retrieve it accurately.

If your system sounds like a movie theatre, you just did it wrong.

The movie theatre is not the reference: reality is.


Max Christoffersen

[michael w]

Everything Max said plus even THX , longtime promoters of diffuse surrounds have modified their stance.

The latest implementations of THX switch off the rear channel decorrelation circuit when a discrete rear channel signal is detected.

The real question with film soundtracks is how do we judge how close the reproduced sound gets to reality ?

Natural sounds sure but what about all the sound effects now employed that have no basis in reality ?

Sounds like screaming Orcs and phase plasma rifles etc etc.

Where's our reference ?


cheerio

[maxcat]

Michael - We use the same point of reference we do for electronic instruments (synthesizer) with no real-world-natural-non-amplified reference: That is how 'real' do we perceive it to be?

It is exactly the same reference point used when we listen to amplified voice or amplified music or musical instruments with 'uncertain' electronic origins.

The point is that the home theatre reference is reality - just as it is with two channel or multi-channel music.

The reference is not the way it sounded in the movie theatre or dubbing stage. That's where Dolby/DTS depart common ground from THX (and Holman's original spec).

This view provides some problems for those subscribing to the (flawed) view that the cinema is what we should be emulating. (I was among them for years). This is equally true of manufacturers as it is for enthusiasts who have yet to place the priority on the recording and not the room.

If you subscribe to this view, it requires a mind-shift back to where this all started - recreating and simulating reality through electronic means.

As a card carrying dipole owner, it took me years to figure out how simple this really all was and how fundamentally flawed the dipole argument was.

I would also go so far as to say the 'original' dipole argument for delocalising mono surround soundtracks was equally flawed due to the exact same reasons I have outlined in my first post: it's not about the sound in the theatre.

But as I say: work out what *your* reference is and the speaker type will be obvious and easy to choose.

And your mileage may vary...

Max Christoffersen

[super8]

Thanks for all the replies. I'll just stick to what I've got. As there seems no real reason to change.

Does anyone run or heard the image cw100 in action? Although they seem to be designed to diffuse the sound too?

[Slippery]

Max, that is really hitting the nail on the head. For years I was trying to have my room sound like a theatre. Now, I just want to reproduce the movie soundtrack with out the trickery etc.


With music it is different, I find the Dipoles work well with general atmosphere type sounds ie. concerts etc.

I think the problem is the word "surround"in descriptions of surround sound. I prefer the term "rear chanel".

The issue I still have is, with my rears there is often a "hole" behind the listening position. I am always frustrated by the lack of a sweet spot from almost any soundtrack with a rear chanel. And before you all start replying with tweaking and experimenting advice, I've tried it!!!!! It is why I'm trialing the Dipoles at the moment. I am trying to find how to "fill in" the hole behind the couch. My rears are the same as my fronts, I just can't seem to find THE right position for them.:mad:

Slippery.