Speaker "Toe in" and linearity. How important is it to aim speakers at your ear?

[j_garcia]

Cabinet edge diffraction is only a small factor. Off axis performance is determined by the combination of all the driver's response and is measured as such. Spacing of the drivers closer or further from each other affects how frequencies from each driver interact with one another (creating peaks or dips). The crossover can also be used to some extent to adjust the speaker's overall response on- and off axis.

I think in a symphonic performance the only people to enjoy that kind of precise soundstaging are the conductor and a few people in the best seats!

In a good auditorium, that will not be the case, but obviously there are definitely going to be seats that are better than others. One of the books I have on Acoustic Engineering actually has formulae and theory for designing for indoor and outdoor auditoriums and even churches; quite interesting actually, but it's over my head.

 

[Bevan]

Your girlfriend will be more on axis to one speaker than the other. and that will cause the problem in freq. response at that location. The speaker to which she is more on axis will sound louder, by how much depends on the off axis characteristics of the speakers. (see crude diagram)
Actually the axes should be crossed behind the listener. This is to ensure some dispersion still occurs and the sound stage does not collapse totally.

agreed, she will always be more off axis to one speaker. but will it be off to a greater degree if the speakers are toed in or if the speakers are firing strait ahead???

wouldnt it be the speaker that she is closest to that will sound loudest, irrespective of how off-axis it is??

i would agree that speakers most often sound best crossed behind the listner. but not always. i have seen quite a few high-end systems set up to cross in front of the listner.

cheers

b

 

[rushwj]

Bevan,
What systems have you heard that sounded better crossed in front of the listener? That doesn't seem to make much sense to me, either from a wave or a directional standpoint. Did they happen to explain why this was (was it an odd shaped room or a character of the speakers - such as horns?)
My 2 cents is that w/ my particular room and speakers (paradigm studios) that toeing in improves my sound stage, especially in "the sweet spot" w/ the crossing about a foot or so behind me. I played around w/ multiple angles and found this one to be best for my listening. I think it does make sense from a wave standpoint to meet behind your head w/ the waves passing along your ears at the same time.

 

[bigpapa]

Wouldn't the soundwaves pass your ear at the same time anyway?

No matter if axis is in front of you and behind you?

I'm not trying to dispute that it may sound better, I'm just trying to understand on a fundamental level.

The sound wave is generated at (essentially) the same point in space. Whether the tweeter is aimed (perfectly perpendicular to) behind your head, or in front of your head, it shouldn't matter as long as it's somewhere close to the axis of the tweeter.

I don't think this is a timing issue, more an energy issue.

I'm just trying to understand, because I don't see how it would make a difference.

wmx, where are you?

 

[bobbydigital]

Just trust your ears. If you can't trust them then just go with your eyes and pick what looks the best because if your ears cant tell the difference then aesthetics are the only thing left.

 

[Doug917]

This is a very interesting thread. I recently had my wife complaining that things do not sound like they are behind her, but to the side (she sits slightly to the right of my sweet spot). She was amazed when she moved over ~1.5 feet into my sweet spot. I am going to try to expand the sweetspot area a little bit. I don't want her to miss the greatness that I am hearing (it would also make upgrading equipment easier as well if she hears more of the benefits). I have Klipsch speakers currently toed-in in front. I am going to experiment a bit after I get my acoustic panels for the first reflections by reducing the amount of toe-in.

Not to hijack the thread, but the other issue I have with her seating position is the right surround is closer to her than the left surround as she sits toward the right wall. It causes the info from the surround back channels to be overpowered by what she hears from the right surround as well. I lowered both the side surrounds 2dB and this helped considerably, but I am left wondering if there is a better solution

 

[bigpapa]

Trust me brah...

Just trust your ears. If you can't trust them then just go with your eyes and pick what looks the best because if your ears cant tell the difference then aesthetics are the only thing left.

If it sounds good, I'm going to do it. I'm just trying to fully understand this principle.
One aspect of my career is making surround sound perform well in situations that are very difficult, and as well I have my own 5.1 with in walls.

I think my setup sounds good (for a room that sucks for sound), and I do a pretty good job (I think) of getting surround sound to sound good in crappy sound rooms.

Understanding this principle fully may help me do my job better. Mainly though, I just want to know.

The company I work for mainly uses two speaker lines, and they aren't available retail. One line (installed in my house) is supposed to have great off-axis response. The other line (not in my house, too much $$$ ) doesn't have specs available to me. I don't install and have had little experience with all of the other speaker lines discussed on this thread, although I've installed/used some of them before for other companies. That's why I'm interested in the off-axis response of them also, and whether they are sold or spec'ed with the measurements.

Re-reading my thread... rambling. Bye

 

[bigpapa]

Hey Doug,

Thanks for the compliment. This sure beats the "(speaker) vs (speaker)... What should I buy!?!?" threads.

Not to hijack the thread, but the other issue I have with her seating position is the right surround is closer to her than the left surround as she sits toward the right wall. It causes the info from the surround back channels to be overpowered ...

What kind of speakers do you have? I think this is the reason Dolby recommends speakers pointed away from you. But, lowering the dB is a good cheat. That's what I did.

Don't worry about hijacking the thread. As long as you don't bring up Bose or expensive/exotic speaker cables, it'll somewhat stay on track

Maybe you should widen your sweet spot to incorporate where your wife sits. It's a classic trade off... Play around with them and report back.

 

[Doug917]

I have Definitive Technology BP2X bipolar speakers for the side and rear surrounds. They are all four mounted about 3' above the listening level and the null portion of the side surrounds is directly to the side of the listening positions.

I did play with the fronts (Klipsch RF-25 L/R) and greatly reduced the amount of toe in so they are just barely tilted inward and the sweet spot suffered no consequences. My wifes seat was fine with movies, but 2-channel in her seat went to crap.

I'm not going too overboard as I will wait for final adjustments until I get my acoustic panels in place.

 

[WmAx]

No matter if axis is in front of you and behind you?

I'm not trying to dispute that it may sound better, I'm just trying to understand on a fundamental level.

The sound wave is generated at (essentially) the same point in space. Whether the tweeter is aimed (perfectly perpendicular to) behind your head, or in front of your head, it shouldn't matter as long as it's somewhere close to the axis of the tweeter.

This is stereo sound reproduction. There are NO standards; not for recording, mixing, mastering or playback. It's purely listener preference that defines what you should do.

Here is what happens with a typical front-firing, direct radiator multi-way speaker with average polar response(which is not very good, btw) in a standard rectangular or square room with centered listening position with a symmetrical placement of speakers in relation to the walls, based on your toe in vs. toe out scenarios:

Toe in to fire directly at your ears or in front of head: the tweeter is highly directional above 8-10kHz, so is the midwoofer in it's upper range of 3-4kHz; the direct sound you hear is basicly the 0 degree polar response of the speaker. The power resonse(off axis total response) is rather poor for average speakers, and the toeing of the speaker exaggerated this problem at the extreme relative angle to the 1st wall reflections. This will tend to increase imaging focus; because you have reduced the 1st wall reflections and increased the treble balance as compared to being toed out.

Toe out to fire far behind head--basicly speakers are pointing straight or nearly straight: the tweeter and midrange are now radiating a more linear response to the 1st reflections, but the direct sound arrival is ramping down in treble response, because you are now considerably off axis(30-40 degrees probably) from the speakers. You hear a more even/linear 1st reflections, but the dircect arrival response is compromised. This will result in a better quality ambient/soundstage width effects on music containing such material because the treble response being reflected from the 1st reflection points on the walls is now higher in amplitude resulting in a stronger phantom sound source point and the sound will be less agressive sounding due to the reduction in treble energy off axis as compared to being toed in. The stronger phantom sound source points will tend to diffuse imaging, as will the reduction of the treble response due to the off axis reduced treble power.

There is no clear winner in toe in vs. toe out; but in this particular case I would probably more likely toe in the speakers. If I found the treble to be too high in amplitude with toe in, I would put absorbers on the walls to reduce or remove the 1st reflections so that I could toe the speaker out as a form of treble adjustment without diffusing the imaging and overall clarity with the side reflections. But the treble balance difference due to toe out will reduce imaging somewhat.

This above is purely hypothetical; in reality I do not use average direct fire radiators. I was providing the above for reference only. I use speakers that have basicly a response approaching omnipolar; I use the unique 1st reflections from such a speaker to great adavantage, and I do not care if imaging is not as focused as is possible, because I place far more weight on realistic sound and ambience than I do on imaging. Tightly focused imaging is not something that will normally occur in real unamplified music circumstances unless you are sitting directly in front of the music source at a very close proximity.

-Chris

 

[WmAx]

3. The Rub; how is off axis performance engineered in a driver? Shape, travel, power... moon dust?

Off axis performance of the actual driver is determined by the effective sound radiation area shape and size. But a lens or ofther reflective directivity system can be used to change this inherant response. Some tweeters and small midranges have s small device called a phase plug attached in the middle, that help to linearize higher frequency reflections, by way of reflective interference. Some tweeters and midranges are horn loaded, thus using a reflective lens system to change the off axis characteristics. Note that I am referring to the actual driver as an assembly, but I am not referring to a completed speaker system; as then other factors also determing components of off axis response. But regardless of final system design, no crossover or direct radiator cabinet will allow a driver assembly to have wider off axis response than it does inherantly.

-Chris

 

[bigpapa]

Thanks WmAx

Some tweeters and small midranges have s small device called a phase plug attached in the middle, that help to linearize higher frequency reflections, by way of reflective interference. Some tweeters and midranges are horn loaded, thus using a reflective lens system to change the off axis characteristics. Note that I am referring to the actual driver as an assembly, but I am not referring to a completed speaker system....

-Chris

Gotcha. Where I've been getting at with all this... can off axis response be improved (on a tweeter/driver) without losing on axis response? I realize it may not be a simple answer.

If I was an in wall speaker manufacturer, I'd pay a lot of attention to my off axis response.

This is a really important subject to me, because I make a living out of trying to create good sound out of horrible sounding rooms. Would I be better off shrinking the soundstage to mimize reflections?

I've been noticing that reflections have almost as much influence on sound as the actual speaker placement and design.

 

[bigpapa]

I use speakers that have basicly a response approaching omnipolar; I use the unique 1st reflections from such a speaker to great adavantage, and I do not care if imaging is not as focused as is possible, because I place far more weight on realistic sound and ambience than I do on imaging. Tightly focused imaging is not something that will normally occur in real unamplified music circumstances unless you are sitting directly in front of the music source at a very close proximity.

-Chris

I would agree with you in principle, but also would agree for a similar reason; most surround systems are meant to be enjoyed by more than one person at a time, and I would think the same principles apply. It seems like 1sts can be manipulated to advantage for music. Is this something I can utilize for surround?

Is it relatively simple to study and understand, or is this something I should be buying software for or studying? Or, should I just make a career out of pestering you for all the answers?

 

[WmAx]

Gotcha. Where I've been getting at with all this... can off axis response be improved (on a tweeter/driver) without losing on axis response? I realize it may not be a simple answer.

Yes, you can. The easiest way requires a very small horiztonal radiation area, as is found on some ribbon or some isodynamic tweeters; which allows the horizontal off axis response up to 15kHz at 75 degrees to be almost the same as response at 0 degrees. But thes usually entail other problems, such as requring a high crossover point, which then brings up an issue of the upper range ability of the midranges, and if using small midranges that will not have a problem with that upper band, then you have to consider the special considerations for a woofer and the cabinet space of that woofer and how it deals with resonances that would not otherwise be a big concern. Or you can use an intermediate midrange between a lower midrange and tweeter, making a 4 way system, but this will add cost and complexity. Or one can use a special, high performance lens system, but this will add complexity and cost. There is no free lunch. You'll have to give in to either raw cost or complexity(which actually increases cost; increased labor).

As far as limiting dispersion, you can't do this effectively with conventional direct radiator speakers. Because of the wavelengths involved, it is not possible to do for a wide enough frequency band in a small size speaker. This requires a very large horn loaded system(which have other technical problems), or a huge array system(very costly) or an ultrasonic intermodulation panel(experimental technology, not yet available).

-Chris

 

[WmAx]

I would agree with you in principle, but also would agree for a similar reason; most surround systems are meant to be enjoyed by more than one person at a time, and I would think the same principles apply. It seems like 1sts can be manipulated to advantage for music. Is this something I can utilize for surround?

Stereo has no standards. Surround for movies, on the other hand, is standardized. If you want the best response for the largest selection of soundtracks, then you should stick somewhat to these standards. At minimum, direct radiation left, right and center channels should be used, and the 1st reflections should be attenuated somewhat by use of diffusion or some absorbtion. However, you can effectively use omnipolars speakers as direct radiators; have large low weight panels to hang on the front and side wall 1st reflection points. Use them in place for movies, and remove them for music. But user preference will rule in the end; you might prefer movies with the omnipolar reflections, or you might enjoy music without them; I don't know your preferences. Alot has to do with the placement/distances from the walls, especially with a system where you are purposely using the reflections to add to the sound. It's time consuming to find the ideal placement so that reflection time and proximity is the ideal mix. This assumes that one is free to have a wide range of placement options, as well. In a restricted set up, an omnipolar is a bad idea for music or movies.

-Chris