directional speakers

It looks like there is a divergence of opinion about how wide the speaker’s radiation pattern should be.

Given that the BACCH-SP system is using the spatial information already on the recording to present an exceptionally wide soundstage, rather than relying on strong early same-side-wall reflections to do so, I agree with Theoretica’s recommendation of speakers that are "more rather than less directional".

I pursue spatial realism in my speaker designs by a different route than what Theoretica is using, and in the course of product development I conducted quite a few controlled blind listening tests. I find a trade-off relationship between soundstage width enhancement due to strong early same-side-wall reflections on the one hand, and image precision, soundstage depth, and clarity on the other. I prefer the latter package of attributes, hence my preference for relatively narrow-pattern speakers, BUT my approach DOES give up some soundstage width relative to wide-pattern speakers.

The BACCH-SP arguably offers "you can have it all, and better than before", and in the context of what their processing does, strong early same-side-wall reflections are counter-productive.

Duke

@audiokinesis The tradeoff you describe is very interesting.  I,too, would choose imaging precision, soundstage depth and clarity over soundstage width.  We'll see if Bacch allows me to have my cake and eat it too.

Thanks

@treepmeyer, in my experience interaural crosstalk cancellation works; it significantly expands the soundstage in width and depth, and enhances the sense of being within the acoustic space on the recording.

I owned an electronic interaural crosstalk cancellator in the early 80’s and it worked but colored the sound, and Theoretica has addressed the coloration issue.

In the mid-80’s I made a passive interaural crosstalk cancellator using large foam wedges which worked but was impractical. Theoretica has addressed the practicality issue.

Polk Audio made, and I believe still makes, speakers that use a secondary array of drivers to provide interaural crosstalk cancellation. Ime their approach works too.

But Theoretica’s processing goes beyond interaural crosstalk cancellation; it also uses de-correlation, which ime further improves perception of the acoustic space already on the recording. And since the BACCH processing is extracting information from the recording itself, the sense of spaciousness won’t have the "sameness" from one recording to the next that can arise with synthesized spaciousness contributed by upmixing to delayed rear channels.

To the best of my knowledge, techniques for interaural crosstalk cancellation only work within a fairly small listening area, typically one person wide and maybe two people deep. So there is that limitation. My understanding is that some versions of the BACCH system do head-tracking and therefore work from a wide range of listening locations, but still only for one (or two) people at a time.

(I have no affiliation with Theoretica.)

Duke

@audiokinesis Everything you say is consistent with my understanding.  I'll report back in a month or so when I get the Bacch system up and running.

By the time we get enough money for good equipment, and good source material, and enough free time: we are old enough that our lack of sensitivity to high frequencies has begun, and will continue to diminish, thus the distribution of the narrowest frequencies are the ones we want to preserve, perhaps boost a bit and a bit more as we age.

Ignore the Space (at first)

One Listener, always dead center, narrower may be beneficial.

A bit OFF Center (i.e. two listeners): narrower may be detrimental.

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Measurements, published specs:

frequency balance (i.e. 45 hz to 35000 hz +/- 3db)

sensitivity (1 watt/1 meter away i.e. 89db)

are taken directly facing the speaker. (i.e. direct toe-in), most often in a space with zero reflections.

On/Off Axis (infrequently given by maker, mostly revealed by reviews with test reports). Polar graphs of individual drivers, and assembled speakers exist.

On/Off Axis shows the ’drop off’ of various frequencies as you sit off axis (off center), the narrower frequencies ALWAYS dropping sooner off center, and producing less volume than other frequencies. Horns, multiple tweeters, acoustic lens ... are meant to minimize horizontal drop off of narrow frequencies (often controlling/limiting vertical distribution)

Sit Dead Center: toe-in: aim the speakers other than directly at listening position,

narrow frequencies will be weaker in volume than wider frequencies. Detrimental to both frequency balance and Imaging.

Sit a bit off center:

narrow dispersion: the highs are weaker than other naturally wide frequencies, and Imaging is altered detrimentally.

wide dispersion: the highs are closer to the other naturally wide frequencies, and Imaging will be better than narrow dispersion.

Alternate Toe-In. DBX Wide Imaging System.

Aim left speaker directly at right position. Aim right speaker directly at left position. Each position gets ’more’ volume via directivity combined with ’more’ volume via distance to nearest speaker. Wide imaging is created. Great for 2 listeners and very important for home theater

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Imaging (not frequencies)

2 channel stereo: All is phantom, the engineers varying volume side to side, phase, other engineering methods.

narrow dispersion: successful imaging will be limited to dead center

wide dispersion: successful imaging will be extended a bit off center as well as center.

You, wherever you are, are not aware of whether distribution/imaging is from narrow or wide dispersion drivers, you only hear what that specific position receives. IOW, you are not aware if the distribution is narrow or wide, just whether the imaging is poor or good.

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Now Consider the Space (reflections off floor, ceiling, side walls, rear wall)

and Toe-In as it relates to the speaker’s directivity, and the space’s alteration of the speaker’s measured dispersion, NOW in a space with reflections..

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Get thee a SPL Meter, Tripod, and a Test Tone CD (not LP). Know what you are dealing with, what you are getting, at that location, in that space.

Oh yeah, old fashioned features: a balance control, tone controls, equalizer, or my beloved speakers with level controls combined with those features.

Then, adjust for your preferences and/or needs i.e. your hearing ability as revealed in testing.

Lastly, remote balance, a gift you give yourself.

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