Speaker toe-in & stereo imaging

Recommendations seem to range from turning the front LR speakers to face the prime listening area directly to slightly turning the speakers in toward the prime listening area. What do you use, or is this question too speaker specific?

I'm going to be using a pair of bi-wired KEF Reference 104/2s for the front LR speakers, along with a pair of Velodyne HGS-10 subs crossing over at 50 Hz.

Toe-in can be speaker specific, and also can be influenced by your room and intended listening position. It has been my experience that speaker owners' manuals often suggest optimal speaker positioning, including toe-in.
This is a speaker specific question. A lot of dynamic speakers like to be fired straight ahead, listening to the tweeter on axis would be too hot (Theil speakers come to mind). Others like a mild toe in and, as you mention, some want to be heard on axis. It all depends on the horizontal dispersion of the tweeter. Just keep an open mind when setting up you speakers and listen to them in several variations of toe in. When the highs seem natural and blend well with the midrange you've probably found the right spot.
I agree wholeheartedly with Newbee's comments suggestions above.

I would also like to add that the wider you space the speakers apart, the more likely you will have to toe them in. The more toe in that you use, the narrower that the sound stage will be. If the speakers are situated where you have a lot of gear / equipment / TV situated between them, you may end up having to toe them in slightly more. How much the gear in the middle affects the speakers will depend on how solid that structure is, if the speakers are in front of / equal to / behind the structure, etc...

I posted a method that i use to locate speakers that works pretty well in most any size / shaped room. This approach allows one to take into account the individual types of speakers used and the listening distance that one would normally use. That was a LONG time ago though and it requires having a "mono" switch on your preamp. Some newer gear doesn't have this feature, so it may be harder to achieve optimum results even if you were to find and follow the directions i made in that post. Sean
If you can, go with Sean's mono method. If not, try to position yr spkrs ~65degrees apart fm each other as seen at listening position. Play with tow-in fm there. As newbee notes, a lot has to do with upper frequencies drivers' vertical dispersion.
If you go to our resource page there's a link to an article we wrote on speaker placement titled "Loudspeaker Placement Guide". One of the issues is toe in. It agrees with Newbee and Sean, just gives you another method of accomplishing the goal.

Rives Resource Page
Rives, your website has grown and improved substantially since last I visited (which has admittedly been some time). Thanks for providing a nice resource.
I think you're correct to assume that this would be speaker specific, but as others have mentioned don't limit yourself strictly to the manufacturer's recommendations either.

I have three different pairs of ProAc speakers and in their manuals they recommend toeing in the speakers so that only the front baffles are visible from the listening position. I've found this set up to yield a very precise center image without sounding bright, but I have always preferred to have them angled out a bit so that I can see roughly an inch of each speaker's inner sides. In my room, this creates a wider soundstage without sacrificing focus very much.

I've heard 104/2s facing straight out and wondered if toe-in would help them. I also felt that they needed a sub. How is the HGS working with them?
Where a loudspeaker has a line array configuration, like a Magnepanar, and the tweeter section is on the outside, (per Magnepanar instructions) this has the effect of toe in, so you may want to keep the speakers physically straight. But then I have heard some people say that they like their Maggies with the tweeters inside, which would be toed out. Go figure.
When I ran Uni-Q equipped KEF's, zero toe-in provided locked in, pinpoint imaging across and within the soundstage. Watching the KEF's images was almost as much fun as listening! Toed in, the KEF's treble seemed a little too much in my face.
Thanks for the informative responses. I do not yet have the pair of 104/2s (they are being shipped), and have never heard these speakers. I bought the pair based on reviews I've read, and on experience with my four 102/2s and 100C. I really like the sound of my bi-wired 102/2s and 100C, and they blend seamlessly with my Velodyne HGS-10. I realize that the 104/2s do not have the Uni-Q HF driver, whereas the 102/2s do. Even though the pair of 104/2s are said to be late serial number bi-wired units, I doubt they will come with a manual. I plan to add a second HGS-10, and a techie at KEF suggested setting the crossover at 50 Hz -- I use 80 Hz with the 102/2s.

Just a few thoughts to add to those above:
A speakers crossover point (and woofer dispersion/size) will also effect toe in especially since some 2 way units will drive their woofers above 4K. The beaming that results will cause a greater variation in the upper mids between on axis & off axis response.
The distance from the speaker pair & the proximity of the side walls can also be very significant. Trying a variety of positions is the key. Changing the location, height or angle of a speaker usually changes the sound far more than many often spoken of tweeks or cable changes.
It is such an easy thing to test yourself with your own speakers in your own room, it is speaker and room specific.

In my experience most box type speakers with tweeter etc sound best overall with toe in about half way between straight ahead and directly pointing at listener. If speakers are very close together less toe in required. Want best compromise of wide sound stage but solid deep center.
I usually start with no toe in and go from there. If your speakers are on the brighter side you will most likely use very little toe in.