TOPIC: Stereo setup with a center speaker:

First excuse me for my bad English.
I want to use a particular stereo setup with a center speaker:
My right and left speakers are designed to be placed at the corner of the room (Klipshorn) .. But the distance between the 2 speakers is too wide (6m) this causes a sound hole between the speakers. They are bi-amplified (external active filter before amplification).

So I needed to create a center channel (addition of left and right channel) to fill this hole and I thought about SHD to create the center channel (better definition than other stereo or multi-channel mini dsp).

Is it possible ?

To do this I am thinking of using Output 1 for the left channel, output 2 for the right channel, and I continue to use my active filter at the output of these outputs, the SHD crossover will therefore not be used for output 1 and 2, the PEQ and gain / delay can be.

Output 3 will receive the left channel + the right channel, output 4 also (right + left), output 3 and 4 will be reduced (from -3 to -12db or more to test depending on the width of the desired stereo scene and the config used).
Output 3 will use crossover / PEQ and gain / delay and will do the center mid / high, while output 4 will do the bass of the center.
Will Dirac be able to manage this config? Since when the left channel plays the central will also play, and ditto for the right channel (impulse response, delay, since each of the channels (right and left) will be played by the left or right speaker and by the central.

What do you think, is this possible?
Merci.

Do you hear a 'sound hole' in the middle or have just read that you will have a problem? You may not have a real problem... If you do then I would replace your speakers with some which work where you want them.

I don't think any 'solution' that involves producing an additional center channel signal by using a miniDSP would work well.

@AlainHorn: Have you thought of buying and setting up a center speaker to "fill" the "hole"?

wizzy wrote:
Err..., yes they had, hence the OP .

@AlainHorn, why is it recommended to have your speakers in the corners? Weak bass if you don’t?

At the end of the day this is only a recommendation still. There are recommendations for every speaker ever made but not everyone is able to follow them to the letter.

Personally if it was me I would sacrifice bass and pull them closer together and toe them in more to not have a hole.

If you want a centre, then there has to be more complexity surely in its set-up which If you don’t get correct would probably muddy everything. Could you consider a “musical” AV processor and just not bother with surrounds?

But before all that is simply ignore the recommendations and push them closer together!! If the bass is then weak get yourself a sub.

@asx77 some speakers are designed to fit right into corners and probably would work poorly at frequencies higher than those covered by a subwoofer. I suspect the OP's fall into this category. No harm in trying I suppose but my guess is this probably isn't the answer here.

First step is to be sure there really is a problem that needs to be fixed .

Unlike other Klipsch speakers the Klipschorn MUST be placed in a corner since the corner completes the flare of the horn. Not just close to the corner, really as far into the corner as possible with skirting/baseboards removed. They can't be toed in any more than their natural fit into corners.

A centre hole with walls longer than around 5m is a known problem so this room is only just slightly bigger than what the speakers can handle. At various times in their history Klipsch have supplied centre speakers to solve this exact problem so I think the SHD should be able to supply a centre speaker feed in some manner as the OP desired.

Dirac itself will always see the combination of speakers as a simple Left/Right stereo system, no matter how many drive units you have, so if channels 3 and 4 can create a suitable centre signal it should be fine and in accordance with Klipsch philospohy.

Moving them in from the corners doesn't just lose bass it trashes the wonderful bass, So adding subs is a poor choice, the OP's desirre is likely the best.

I fail to see how a true 'hole' is possible acoustically.

Sorry to ask a perhaps dumb question but traditional thinking suggests the soundstage is created from the positioning of the speakers AND listening position. Could the OP not improve the situation by moving further away if the room layout allows?

asx77 wrote:
Yes, although my bet is this isn't practical here.

I should maybe explain why I don't like the center channel idea... If you have a mix of left and right channel signal from main speakers and center speaker then this will clearly mess with imaging/localising sounds as intended/recorded. If you only send the signals to a center channel then you'll have a mono system with everything appearing in the center.

Ultrasonic wrote:
Given that Left/Right 2.0 systems are a bit of a crude way of approximating plane waves with a full width sound stage anyway shoving centre speakers in at -12dB probably won't mess with things as much as you might expect. Its really just inserting the signal that should be there anyway but isn't in this particular case.

To be more precise if you had the centre speaker at the 0dB the soundstage width should reduce to 3m. At -12dB centre you wouldn't lose much width at all from 6m.

Most people living in small rooms will never have heard an acoustic hole in the centre but it definitely can happen in larger rooms or at concerts. And yes, the listening position would probably have to be 5m back from the speakers to hope to avoid the centre hole which would likely lead to other problems. With a near 6m soundstage width you can afford to lose a little bit of localisation precision I would think.

Althought I can't guarantee it would work really well or be quite as perfect as a pure 2.0 system I believe it would be a significant improvement on the current situation. The SHD and Dirac can definitely handle it so its worth trying. It also isn't at all obvious what Plan B might be so there possibly isn't much choice.

Would you need to make sure all three speakers were on a perfect arc from the listener or else how can Dirac get timings correct?

entripy wrote:
Only for a signal that is panned dead-center. For any other signals it is adding an additional/incorrect sound.

If any miniDSP were tried I really don't think it should be a Dirac Live capable one as the algorithm will not even be remotely be designed to handle a situation like this.

asx77 wrote:
You should always use REW to measure the speaker delays and correct time alignment in the SHD Plugin before using Dirac.

entripy wrote:
It would only be possible to achieve exact time alignment of left + center at a single spot. Dirac relies on multiple measurement locations, for which the variable delay between the two will result in signal variations that won't at all fit with the assumptions of the Dirac model.