Radical toe in once more

@toro3 - thank you. Interesting!

I’ve been periodically playing with placement of my Tannoy Stirlings over the course of the past year and a half. Per their manual, radical toe-in is recommended. Historically I found the treble energy to be a little much while reducing the soundstage in exchange for a very solid and dimensional phantom center.

On a whim I went back to the radical toe-in for the past three weeks with the drivers crossing about a foot in front of me. For tone, I pushed the speakers a little closer together while giving more space between room boundaries. Perceived width of soundstage diminished a little, but I think to some extent this perceived width was artificial due to 1st reflection points which now seem more detrimental than beneficial in my room. This became clear after the radical toe-in which remains “insightful” in terms of depth and clarity, but not “too hot” in treble which I suspect is from the reduction of space between speakers and crossing of drivers in front of the listener (more so than previous experiments with speaker placement). I’ve found myself appreciating the depth and tone much more so than the width of the soundstage.

Room acoustics and what’s considered appropriate and not too “attention grabbing” continue to be a challenge. Speaker placement is one of the few things I can control as a listener which may explain periodic experiments and lots of tape and a tally of measurements in a notebook.

Very educational thread, OP.

A little update. The overall outcome of this discussion is that the speakers are toed in ca 40 - 45 degrees (much like the advice from Audiokinesis), with the listening chair closer to the speakers. Sound is a bit more headphone like. Yet the hot treble problem is less prominent (as long as I sit behind the point where the direct treble sound crosses).

So why did I prefer a different setup, for several years? With the speakers less toed in, pointing more towards the wall? Not sure. Some audio friends with good ears preferred this setup. I liked it, myself. I thought, there is something artificial when the treble drivers cross in front of the listener. No longer sure about that.

It may also have to do with changing listening and music tastes. When I got the Audiokinesis Dream Maker speakers, I was very concerned that they should fill my quite large (50m2) living / listening room. Big music (think Dark side of the moon) should sound, yes, convincingly big. Over the years I have relaxed more. If the music is big it should not need a lot of volume to prove it. And even if the radical toe in gives a more headphone and nearfield type of sound, the rest of the room is well served also, with these speakers. I had a big sub. I sold it. I had effect speakers. They went out. The Dream Makers are best on their own. Positioned as adviced by the designer.

Results do not surprise me at all. I have similar issues in my present main room but, in another room using 'crap' stuff I get the out of phase sounds from the rear and sides of the room as well. I conclude this has more to do with the room and set up than anything else. But I'm OK with it. If I really wanted a room full of sound I'd probably cheap out and just use an old fashioned Hafler set up but it has too many distracting problems in trying to get it set up, but as I recall (and I could be wrong) it relied on out of phase sound coming from 2 additional speakers in the rear of the room. An over simplified version of 4 channel sound requiring only an attenuator for the rear channels. I think you'd hate it! :-)

Just to be sure I tested with my Hifi News test LP, side 1 track 2, voice in and out of phase. Test: passed. No problem. The in phase sound is clearly centered between the speakers, while the out of phase sound is not, but rather floating around. Two modifications, though. The in phase sound supposed to be centered between the speakers is evident also a bit outside of the speakers, in my case. Maybe reinforced by sidewall reflection, allthough it sounds quite good, the timbre is the same as in the center, it seems spectrally correct. Secondly, the claim is that the out of phase sound should come from everywhere, but that is not quite true. It comes from the general direction of the speakers. Not from the other parts of the room.

Newbee, thanks again, I get it now.

What you say about recorded sound is mostly known to me, although it is nice to get it so well and briefly formulated.

On one level I agree that in and out of phase recorded sound has nothing to do with speaker performance. Yet the capability of speakers to reproduce out of phase as well as 'ordinary' in phase sound comes into the picture too. So, for example, how well are my speakers able to reproduce cases like Roger Waters: Amused to death, where some out of phase 'mystic mix' production is able to recreate sound not just floating around, but locate it precisely beside you, and even a bit behind you.

I was referring to the recorded sound. Sounds recorded in phase will appear between your two speakers, not outside of your speakers. Sounds recorded out of phase will appear from all about your room, but not focused between your two speakers.

Listen to a test record which has music recorded in phase and out of phase. When you listen to a cut recorded in phase you should hear nothing outside the speakers (in a well set up system which has no 1st reflection point reinforcement). Likewise when you play a cut with no in phase sound you will lose that focused sound we all love. (Recording engineers do play with phase when recording music which can give an enhanced sound stage.) Getting your system set up properly entails getting reproduced sounds, either in phase or out of phase, as put down in the disc. The Sheffield/XLO Test & Burn-in Disc has such cuts with an explanation. With this and some other cuts it can be quite helpful in setting up your system. 

This has absolutely nothing to do with the performance of your speakers with which you seem to be concerned. That is an entirely different issue. 

@newbee wrote: "I see a lot of folks who think crossed axis’ compromise the sound stage."  Yes, I've recently read some of this myself. 

"What I think they hear are 1st reflection points and think that is part of a normal sound stage. They think in-phase sound outside of the speaker edges is a norm and if they don’t hear it something with there stuff or set up is wrong. Not so, it is right!"

I understand the first part. With radical toe in, the 1st reflection points are 'missing', relatively speaking. My experience also. And some folks miss that, just from habit. But I don't quite get your further point, about phase.

My speakers are bipoles, and as I understand it, all the sound - from the back as well as the front drivers - is in-phase. Dipoles / open baffle speakers are different, since the back sound is out of phase. What I observe with my speakers is that the sound from the sides of the speaker is much lower than from the front and the back. But I think it stays in phase.

Yes you are correct, they have ample space behind them. I measured: 6,5 foot from the middle of the front drivers to the wall behind them, 5,5 from the back drivers. I know that they may sound even a bit better half a foot or so more out from the wall, but we have some living room compromises...

Six feet is good! Do I assume correctly that they are also six feet forward of the wall behind them (front wall)? If so you're really good. FWIW this distance allows separation of the reflected  and the direct signal which give you a clearer sound of both.  

Thanks @newbee. Very interesting. I have the greatest respect for Duke at Audiokinesis, the designer of my speakers, who has been extremely supportive. And yes, I am now back to radical toe-in. I thought this was mainly a fix for small rooms, but obviously it is more than that. I will check out your theory of 1st reflection indoctrination / habituation. May well be the case among some of my "conventional is best" audio friends. And your out of phase "from all about the room" advice.

Maybe I should even give my LCS "effect" speakers a new try. Now that I am back to radical. The LCS - Late Ceiling Splash - is the forerunner of what Audiokinesis now calls Space Generator. It is kind of proto-Atmos, all in the analog domain. It didn’t quite work with my main speakers, but that was (mainly) with conventional toe-in. I’ll give it a try.

Having fun? You bet. I love this aspect of our hobby, how to improve things for low cost, and learn more about sound along the way.

One question - necessary distance of speakers from reflecting surface - advice from Duke - I have forgotten, or maybe not read it, can you repeat? I measured the distance from the middle of my front firing drivers to the side wall - almost 6 foot. The main sidewall reflection area is maybe 9-10 foot away from the drivers and a further 8 foot away from the sweet spot. I've tried some damping in this area, but never noted much improvement, even with conventional toe-in. Testing with more damping, and sometimes more dispersion, has been like, "well maybe, but it is quite ok as is". I've used DAAD columns with adjustable absorption and diffusion, plus home tweaks like a matress up the wall. Note that this is also a living room, not a designated music room. Compromises along the way.

A main finding is that the speakers were designed with this in mind. The idea is that you don't need digital sound correction if you get the speaker and room matching right. You can do it in the analog domain, and that usually works better than digital correction (Audiokinesis has proved this especially through the Swarm distributed subs concept, a repeat prize winner from TAS and others). A large room is a big benefit, the Dream Makers need room to do their work. I see a lot of setups with speakers where the room is clearly too narrow to allow the speakers to breathe, sideways as well as to the back wall.

In my case, with a good room and speaker match, musical images become dramatic and engaging. Especially with top quality analog recordings, without any digital conversion. I also play digital, including DSD double speed recordings of my best albums. Some say you cannot hear any difference from the analog original. Well, I can, in my system. Even if the digital now sounds very good, and closer to the original. 

FWIW, I think you would be wise(r) to follow Duke’s recommendations. He knows his speakers and their proper set up. He takes it seriously. I’ve been doing crossed axis’ for some years and I was tickled when I saw him using/recommending this set up. BTW, I experience no difficulty in reproducing an excellent soundstage. If its on the recording I get it! I see a lot of folks who think crossed axis’ compromise the sound stage. What I think they hear are 1st reflection points and think that is part of a normal sound stage. They think in-phase sound outside of the speaker edges is a norm and if they don’t hear it something with there stuff or set up is wrong. Not so, it is right! All one should hear outside the edges of their speakers is out of phase sound and to quote a test record producer "and it should come from all about the room". Note that Duke also has recommendations regarding the necessary distance of your speakers from a reflecting surface. Follow them! You’ll get much greater clarity. Having fun yet? :-)

I find that I can use my listener chair as a volume control. Moving it backwards means less volume. It also means that I move back some seats in the listener hall, or the sound space of the recording. If I move my chair towards the speakers, I feel more like I am sitting in the front seat section, besides the greater volume. This is with the radical toe-in of the speakers. The effect is similar but weaker with conventional toe-in.

The listening chair position is also a kind of tone control. The closer I sit to the central axis of the direct sound the greater is the perceived output of the treble. This is easy to hear. The whole speaker becomes too beamy, insistent, in your face. I guess this is why most speaker manufacturers advice NOT sitting in the crosspoint. But adjust with toe-in.

When I do some gym, between the speakers, with my ears just few feet in front, they almost sound like my best headphones. They change character a lot, depending on position.

Maybe I should clarify that I am testing toe-in in a living room with natural living room damping from furniture, book and record shelves, etc, as well as carpets and some ceiling damping. I don't want to overdamp and have removed some measures. The speakers are designed to benefit from an ordinary, not heavily damped room. They should stand well into the room, with much space to breathe also to the sides. They should then be toed in for optimal performance, considering the effects of changing the sound from the back as well as the front drivers. They are made to sound spectrally correct, the timbre should be similar from wherever in the room you hear them. They sound best - I think - with radical toe in since this increases the time gap between direct and indirect / reverberant sound. Although maybe with some penalty regarding the front firing sound. The jury is still out. But with the axes crossing only a foot or so in front of me, it seems a small minus.

@atmasphere - the reason why conventional toe in also works quite well in my room is that it is quite wide, sidewall reflections are not so disturbing.

Thanks. Interesting diagram. And unconventional. Care to explain a bit?

The direct sounds from front speakers to a listener influence the sound-stage and sound images the most. Understanding the direction of direct sounds will help your speaker set up. The sweet spot should be around ears. Alex/Wavetouch

@mijostyn 

You can find this under my systems info.

Speakers: Audiokinesis Dream Maker v2 two-way bipoles. In phase. Big wide floorstanders made to "use" the reverberant sound.

Room: Dimensions: 8,30 x 6,10 x 2,62 m / 27,2 x 20,0 x 8,5 feet

@gumbedamit 

Get a buddy to swivel the speakers while you are in your listening position.  Simple!

thanks will try when i get the chance

Hi @avanti1960

Thank you. I have done some of this procedure before, and I have also investigated through measurements (REW, Cara etc). Basically I am back to using my ears. For now I think I am fairly close to ideal, but in the future I may try your ’back to basics / conventional’ method.

@o_holter 

If you are not sure how they are wired take an AAA battery and while holding the negative speaker lead against the negative pole of the battery tap the positive lead against the positive pole of the battery for a split second. If both woofers move out they are in phase and Bipolar. If one moves in and the other out then they are out of phase and dipolar. 

@newbee 

There is always a "right way" to set up well designed loudspeakers in good rooms with maybe 2 or 3 options. There is no good way to set up poor loudspeakers in either good or bad rooms.

@o_holter 

I may have missed this but what brand and model are these loudspeakers. The way the speakers are wire has a huge affect on how they operate. Are the drivers in phase (both front and rear drivers moving out at the same time) or 180 degrees out of phase (front drivers move out, rear drivers move in)?? In other words are they Bipoles or are they Dipoles. Planar loudspeakers like ESLs are dipoles, the front and back of the speaker are 180 degrees out of phase. Using dedicated front and rear drivers gives one the opportunity to wire them either way with extremely different results. Once I know how they are set up I might be able to make some suggestions.  

Get a buddy to swivel the speakers while you are in your listening position.  Simple!

Finding the best sounding firing axis angle is something that really needs to be determined by experimentation (as well as overall speaker positioning!) 

Are the frequency response measurement plots available for your speakers that show different amounts of on and off axis firing angles?   Ideally you would want to aim them such that the response of the top end gradually tapers off for the most pleasing sound.  

Get them in the best general position from room boundaries to give you the best sounding bass and aim them straight ahead, perpendicular from the wall. 

Listen for a few days with your demo songs and take notes, good, bad or other.  Listen for tonal balance, brightness, sound stage, center image, etc.   

Then aim them with some toe in- say 10 degrees or so (maybe ai inch from the inside front corner with tape marks.  Listen again.

Repeat the process inch by inch until you get to the extreme toe angle that aims a foot or so in front of you.  

Review your notes and put them in the best sounding spot!  

Lots of work but that is how you get the best sound out of your speakers 

Yesterday I bought Endresen and Wesseltoft: Out here, in there, on 2 x LP 45 rpm (Jazzland records). It sounded so good that my wife played the whole thing once more (doesnt happen often). So I think we're nearly there. The setup is much like @rhljazz described. Ca. 40 degrees toe-in. I don't hear any front wave disturbance with the female vocal. The treble is a bit tamed, which is OK in my case. In a sense, this whole thing is like going back to start. Following the speaker designer's advice, with some minor adjustments from there. It will be interesting what my audio friends think, since they preferred conventional toe-in, some years ago. Anyway, it has been an interesting experiment, so thanks again for all advice.

Is there an "inherent" problem with radical toe in, when the main sound from the front drivers cross in front of the listener, instead of the more conventional setup where the crossing point is behind the listener - and if so, what?

@o_holter Toe-in helps you to minimize side wall reflections, which are interpreted by the ear as harshness. I don't think there is a 'more conventional setup where the crossing point is behind' for this speaker. Generally if there are side walls nearby, that might not work out so well.

I have ESP loudspeakers in one of my systems.  These speakers are specifically designed for a 45 degree toe in.  In my summer home they are setup in a spare bedroom 10x13x8, technically too small of a room according to the instruction manual.  The speakers are 42 inches from the front wall, measured from the furthest edge of the front baffle.  My listening position is approximately 7 feet away.  In this setup, I ended up reducing the toe in to around 35 degrees so the intersection occurs just at the front of my chair.  The resulting soundstage is much to my liking.  Out of my four systems this is the only one that consistently delivers the “you are there” listening experience versus the “they are here” experience.  It is more of a concert like effect and I like that.

This room is a good sounding room to start with and is treated with two diffusion panels, two tube traps, and several absorption panels strategically located by listening.

I don’t think this degree of toe in will work with most speakers or rooms.  However, experimentation is the only way to find out.

Re hardcore science, well there are books (available on Amazon) on acoustics as they relate to audio systems, but I don't know how much they would help you in setting up your system.

I'm not familiar with the proper set up of bi-directional speakers. Forward firing boxes, panels, and electrostatics yes. I'm really not  familiar with  omni's or bi-directional boxes either, so I'm not a really good source of information for you.

The 'between the speakers" I referred to was from the inside of your forward facing drivers. I wasn't suggesting anything in particular, just that depending on the strength of the off axis signal that reflections off this wall could affect your systems sound (note I referred to 2d reflection points) but its contribution would be small(er) compared to the rear drivers reflecting off any of the walls sounding your speakers. 

But something I can rather confidently suggest you try is bringing your speakers out further into your room. This will give you better separation of the direct sound vs the sound of the rear wall, resulting in a clearer sound. At least 5 ft. Further won't hurt but be mindful of the change in bass response due to room nulls and nodes. 

FWIW.

Hi @newbee 

Jokes aside - I agree with most of what you said. Listen. Take time. Small changes can have a large impact. - This is all the more true with dynamic bipoles like mine.

Just to clarify: my room is large enough that radical toe-in is not needed in order to avoid sidewall reflection (or to enlarge the sweet spot). In fact for several years I have used conventional (slight) toe-in, where the speaker axes crossed some feet behind the listener position. It is just recently that I've changed to radical.

I also agree that listening for soundscape depth is important, and often intriguing. I find that radical toe-in is as good or maybe better in terms of depth (it was good before also). 

What I have not considered, or not so much, is the area behind and between the speakers. There, I have my stereo rack, and sadly, there is not much I can do about it, although I know its not ideal. Oh well. 

Here is what I did not understand: "What you have by doing 'severe' toe in is to point that off axis signal off the wall between your speakers." Are you describing the off-axis sound from the backfiring drivers? In my case, radical / severe toe-in means that the sides of the speakers point towards the middle of the wall with the stereo rack, yet the sides are 4 feet away from the rack, and there are no drivers mounted at the sides of the speakers (only back + front). So I hear less direct sound, when listening close to the sides. And the off-axis sound from the backfiring drivers hits the wall at the sides, not in the middle with the rack, but close to the corners. Maybe I should do the 'mirror test' for first reflections, but it seems to be a non-issue. I could also stack something in front of the rack, or use more absorption/diffusion on the wall, but Ive tried these things before, the improvement is only marginal. Thinking I am lucky, since I have the space to let the speakers 'breathe'.

One of the joys of experimenting with speaker positioning and toe-in is to discover more of the speakers' potential. Recently I brought a pair of stands to a holiday house and was amazed at how much better a pair of Audioengine A5+ sounded. And it was really easy to do mini-adjustments to get them "just right". I wish it was just as easy with my heavy floor standers.

Yet my experiments, so far, have confirmed my positive impression of these speakers. They are indeed chameleon-like, changing according to the music and production. When set up correctly, especially with the right material, they can sound like electrostats, but with dynamic punch, both in the treble and bass. This is also due to excellent amp and speaker matching.

The speakers are a sophisticated attempt to use "best of" reverberant energy in order to improve the perception of the sound as a whole. So, for example, the output is spectrally correct, or quite similar, wherever you are in the room, the main timbre is the same. This is way beyond Bose 901, which I used many years ago. A main 'trick' is to postpone the reverberant sound, so it arrives at least 10 msec later than the direct sound from the front of the speakers - and according to my experiments, 15 msec (by radical toe-in) is even better.

So yes, my ears guide this journey. I would welcome some hardcore science also - if there is a problem with the sound waves from the front drivers crossing in front of the listener, and if so, what is this, and in practice, can we hear it, or is it totally marginal.

Thanks @newbee. I'll think about it...no no! on with the music : - )

Too much sound in your mind, not enuf in your ears I think. There is no right or wrong re toe in, it's what actually works for you. I would agree the aesthetically it might be a bit hard to think it could be right (for you) because few seem to do this. However, it is often done at audio shows to accommodate room/set up problems. 

You mentioned the tweeter off axis sounding better because it dials down the sound, but consider that the same 'off axis' can be achieved by pointing the speakers straight ahead. Much of what is achieved by toe in (or actually toe out for the really venturesome) is brought about by the change in sound from room reflections. Ditto diffusion/deadening wall treatment. 

One thing to think about, and much depends of speaker design, i.e. strength of the off axis signal, is what happens to the off axis signal when you change the speakers toe in. Pointed straight ahead you get a strong side wall reflection (if you have a side wall!) but toed in you change that reflection (but you knew that). Probably what you did not consider is what happens to the off axis signal on the other side. What you have by doing 'severe' toe in is to point that off axis signal off the wall between your speakers. Enter again the importance of the use (or not) of reflective/deadening/dispersive material between the speakers, not just  behind or to the side of, the speakers. For the really anal amongst us, don't fail to consider the 2d reflections points, they can be important as well. :-)

Too complex for the poor mind I think. It may be just simpler just to move your speakers about and listen to the results as you go. DON'T be in a hurry, beyond initial first impressions, the effects of moving speakers which are already established in a good place can be subtle and in my case affect the sound stage, especially image's third dimension, depth of image. No kidding, it probably took me over a year to set up my Quad 63'. And they don't have a strong off axis signal. My present speakers which are just forward firing boxes, not near so much!

Enuf for now, I'm even boring myself. :-)

Thanks everyone. Like I suspected, no consensus. Same thing from my web searches. I read about a guy who went back to conventional toe-in although radical sounded better. Why? It «looked wrong»!

Sure, I will follow my own ears, but in this case I’m not sure. Is there something slightly «artificial» with radical toe-in? Or just my imagination? The one effect that I am sure of, regarding the front sound, is that the tweeters are a bit tamed – less direct beaming – with radical toe-in. Which can be OK in my case. I am also fairly sure that there are positive effects on the back-firing sound, as mentioned, although some are debatable (like more bass but maybe less tight from the room corners). I can well understand listeners who have used a long time, getting the angle right!

Ceiling and floor reflections – yes this is a valid point. I first overdamped the ceiling, and later removed most of it, to good effect. A silk carpet does a good job on the floor (not wall-to-wall). The speakers are designed to sound lively and immersive in a normal (not overdamped) room. They are big and heavy, and my back is not so good, so quick A – B testing is not easy. Disconnecting the back drivers would defeat the bipole speaker design. Likewise a lot of absorption or diffusion behind the speakers, although a little bit is fine.

So what do I do? Go back to conventional and forget the rest? My wife says, maybe radical is better, so why dont we keep it that way.

Radical toe-in is the main suggestion from the speaker designer, although other positions may also work well in a large room like mine.

My thinking might change if someone told me I am breaking a basic law of audio, my membership here should be withdrawn and whatnot! Has not happened yet. So I will keep it radical, for now.

Two more thoughts. I can easily hear differences in the sound from the frontfiring tweeters, depending on their angle. They can sound strident, a bit hard and bright, if pointing directly at my ears. When they point in front of me, they are ‘tamed’, as mentioned. How much depends on how far in front the crossing point is. Someone wrote, one foot is best, and this may be right in my case also. One or two. It depends on the tweeter off-axis sound, too far off axis is not good. Note that I am not trying to widen the sweet spot, it is OK as is in my room. The other thought concerns the crossing itself. With radical toe-in the main direct sound waves from the speakers (esp the treble) cross before they reach my ears. Does this create a kind of disturbance? Or ‘pre-processing’? Just speculating, here.

Below the frequency defined by the baffle width, no difference at all as the sound is omni-directional to start with. Above that, it is all about the directivity of the tweeter. 

Every room is different, every listener has their preference. Correct is what ever sounds best to you. 

Regarding planar/ribbon speakers.  I have the Magnepan 20s that are located 5 ff from the back wall with diffusers (also highly recommended).  With regard to toe-in Magnepan recommends  in its operating manual that the tweeter should not be closer to the listening postion than the base section whether the tweeter is on the inside or the outside.  I have played with the tweeter on the inside and the outside.  On the inside the toe-in is more dramatic.  The sound becomes a preference either larger sweet spot sound stage with the tweeters on the outside vs imaging with them on the inside.  Frustrating and fun process

Dipoles and omnis have their own set of 'feeding habits', esp. in the spaces one makes the habitat....but half the fun (or in some cases, frustration) is like the real estate mantra:

"Location, location, location."

Omnis don't 'toe anything', whereas dipoles in irregular spaces are the polar opposite....pun intended...

...and crippling a speaker on purpose?  Voids warranties on contact, so keep that to older or 'vintage'...

I disconnected the tweets, mids, and xover in a pair of 3ways, but only wanted the woofers (which explains them being upside down....). 😏😉

disconnect the back firing speaker

Interesting topic. I will (hopefully) have new speakers next week. They are of the Planar/ribbon design. I have been told that they should be placed with no toe in, no absorptive materials behind them or at 1st reflection points and place them about 4-5 feet from the wall that is behind the speakers.

Very new concept for me, so, I shall see what this leads to.

ozzy

I am just in two minds, regarding the front wave.

If you had never heard of radical toe-in you'd be happy?  Then pretend you don't know what it is and keep things conventional.

Something rarely addressed is the effect of floor and, more importantly, ceiling reflections. Crossing the axis of your speakers in front of you might get a more diffused soundstage (for the better?) because of changing ceiling reflections. Whatever, it does make a difference if you listen closely.

Thanks to both of you!

My room is quite large, I dont have major problems with side wall reflections or back wave boom, and the off axis treble response is quite smooth. So my speakers sound very good with radical toe in but also good with conventional toe in. I am just in two minds, regarding the front wave.

Is there an "inherent" problem with radical toe in,

The question is, what is ideal toe-in. 

It depends, and lots has to do with how tweeters and mids sound off-axis.  In many cases speakers are designed specifically for zero or no toe-in.  This allows for a wide sweet spot and may actually smooth out the tweeter and mid response.  Especially true for metal domes.  Listening on axis is actually wrong for a lot of speakers designed for the average home listener.

The radical toe-in idea comes from the idea of attempting to minimize side wall reflections.   The idea is to move more of the energy into the room before it gets reflected, hopefully improving imaging and spacial cues when other alternatives ( moving speakers away from side walls, absorbent panels, etc.) are not possible.

Take a look at figure 4 in this review for the MoFi coaxial speaker that's been in the news.  The off-axis response is superb, but still you can see how the tweeter output goes down off-axis.  Then also look at the on-axis response you can see how exaggerated the output is at the very top octave.   This is a speaker you probably want to listen to somewhat off-axis for best response, but which will give you a very nice broad listening area.

IME setting up bi directional speakers can be problematic. That back wave can be a killer if you don't treat the wall behind in in some fashion. I used dispersive material.  The success of crossing the speakers axis in front of the listener depends a lot on how much it is needed to reduce the effects of side wall/first reflections. It usually helps most when the speakers had to be placed close to the side walls. If side walls are not a problem then there really is little benefit other than changing the reflection pattern off the walls behind the speakers. I had Quad 65's for some years and it seemed to take forever to find the balance that worked best, butr I ended up with them pointed to just outside of my ears (no crossing over) and the rear pointing towards the room corners (I was 6ft off the rear wall). But, FWIW, it takes a long time (usually) to find the perfect placement for them to work, but do no minimize the need for rear wall treatment, Hell, I even tried Boston Ferns! Good luck.