Speaker Height / Tilt


What are the benefits / drawbacks of putting speakers on shorter stands and tilting the speaker up?  Do you run into phase and time alignment issues when tilting speakers?  
b_limo
Nope. The real issue is to align the tweeter or mid correctly relative to your head, and it's all subjective.

I find a lot of speakers sound better if I listen below the tweeter axis, and sometimes with the tweeters not pointed directly at me.


Now, to answer you more specifically, what you want to avoid is listening above the tweeter axis. That's where usually the phase and lobing issues you are thinking of occur.
Hi @B_limo

For whatever reason, Stereophile hates e-mailing web links via e-mail, so here you go:
https://www.stereophile.com/content/monitor-audio-silver-8-loudspeaker-measurements


In case anyone is wondering, here is my reply:

If you mean dome tweeters, nope, they are directional, eventually. Worse, some suffer from resonance on axis which is dealt with nicely off-axis.

Now, the issue next is lobing. That is, how the tweeter's response adds or subtracts from the next driver down (in frequency).

With traditional multi-way speakers with a tweeter on top, a mid or mid-woofer below it, the sound is pretty good to the sides and below, but not so good on top.

Take a look at figure five in this review. Notice that at 4 kHz or so there's a significant dip at 15 degrees above axis. It's a little hard to see, but the reviewer put the cross hairs right on it.

Now, compare that to the chart above it, figure 4. To the left and right the drop off is equal and smooth. Further, note how much the top octave drops off axis. This is normal, off center response for this type of tweeter.


@erik_squires so if the treble is currently excessive, which way do I tilt the speaker - away from my ears ie. up or towards my ears ie. down
On the vertical access, you would most likely toe them in toward the center to minimize the side wall reflections that toe out would give you...
I’m not understanding how a dome tweeter is directional... I have a d’appolito designed speaker.  How does that change things.  

But seriously, how does a dome tweeter radiate sound below its axis vs above its axis?  Am I misunderstanding you?  I would think that a dome tweeter radiates sound uniformly top to bottom, side to side...

And if its okay to sit below the tweeter and not above, can you fix that by turning the speaker upside down?  

Last, if its not good to sit above the tweeters axis, why are manufacturers making shorter floor standing speakers with tweeters below a listeners ear level?

Measurable output decreases off-axis.  Just look at any of the Atkinson measurements of speakers in Stereophile.  Because of numerous variables, each model will differ in how a tweeter output decreases.

Also, some speakers are actually designed to be listened to off-axis (e.g. pointed straight ahead, rather than toed in).  Stand height and rake are other variables.  Just look at the instructions for setting up Vandersteens correctly.

I understand that tweeters sound / measure differently off axis, but I don’t understand how they radiate differently above vs below the axis. 

Also, changing tilt changes the tweeter axis, right?
So, here is the evidence tweeters are in fact directional. From the spec sheet of a typical tweeter:
https://www.madisoundspeakerstore.com/soft-dome-tweeters-vifa/peerless-dx25bg60-04-1-textile-dome-tw...
Notice the frequency response chart. Each line represents a different location off axis.


Next, please refer back to the measurements I pointed from Stereophile.

What happens is that the relative difference in distance to your ears causes constructive and destructive interference.  Speaker designers (like me) have to take the acoustic distance into account when designing crossovers.

D'Appolito is the exception in that above and below the tweeter axis is the same. As I tried to mention above, my comments about listening at or  below the tweeter axis applies only to traditional designs with the tweeter on top. With D'Appolitos it's the same amount of pain, and sometimes more so, below and above.

After he initially introduced his famous configuration, Dr. D'Appolito has suggested fixing this by increasing the steepness of the filters if you use his design. That is, if you'd normally do OK with a 2nd order (12 db/Octave) you should try a 4th order (24 db/Octave).
What erik says " I find a lot of speakers sound better if I listen below the tweeter axis, and sometimes with the tweeters not pointed directly at me"
That is exactly my experience with the Wilson Cubs. They sound best with the tweeters just above my ears & intersecting a couple feet behind my head. Same was true with my Tekton's, except those needed to intersect a few feet behind me (less toe in than the Wilson's).    
So there’s a "right side up" for raw tweeter drivers? If the mounting housing was round or square and symmetrical, you could actually position it 4 different ways and create different frequency responses?? Same true of mid-ranges?
Generally when you sit above the tweeter axis, assuming it has good dispersion you end up with a large hole in the crossover region (2-3K generally). This doesn't exist if you get a coaxial speaker.

Good example is the M106 once you go above axis:  https://www.stereophile.com/images/914Revelfig5.jpg
HI @twoleftears

You asked:
So there’s a "right side up" for raw tweeter drivers? If the mounting housing was round or square and symmetrical, you could actually position it 4 different ways and create different frequency responses?? Same true of mid-ranges?

Nope. The issue is the phase matching with the midrange or mid-woofer.

Others here, as well as the Stereophile link I shared, show this.

Basically, like @jcred pointed out, there is a hole that develops in the crossover region above the tweeter axis of a traditional T - M or T - M - W design.

Basically, imagine you take an ideal speaker, and start pulling the tweeter towards you. As you do, the distance between the woofer and tweeter changes. This causes the previously ideal relationship between the two drivers to suffer.

Hope that helps,
Erik
If anyone is interested and has access to a PC, you can try out Xsim with these crossover files.

You can literally simulate a speaker, and try changing the distance in the simulator.


https://speakermakersjourney.blogspot.com/2016/05/lm-1-bookshelf-crossover.html