Stupid baffle question - Woofer beside tweeter, why not again?

[wigginjs]

I know that it is a commonly understood design rule not the place the woofer and tweeter horizontally beside each other in a two-way speaker, but why not again? Is it because it generally makes for a wide and thin baffle that requires more baffle-step compensation? What about in the case of an in-wall speaker, does it matter if the woofer is horizontally beside the tweeter? What is the theory behind this rule?

[sreten]

Hi,

Vertical dispersion anomalies are much less worse than horizontal.
Vertical alignment means no anomalies for each horizontal plane.

/sreten.

[wigginjs]

Hmm... So would that also mean that if the listener is sitting off axis horizontally (even slightly) will result in generally poor performance? Should all speakers be toe'd in then?

[dzzmiller]

Not poor performance, just not optimal.
Many people don't like how it looks, and don't do it. If your using a grill cloth there's little reason not to offset.

[Dr.EM]

Interestingly, the famous Yamaha NS10 studio monitor appears to be designed to be orientated horizontally. At least it nearly always is when I see them.

[wigginjs]

Often with center channel speakers in home theater there is a general rule of not taking a bookshelf and laying it on it's side. Also, there seems to be a consensus that "good" center channel designs will have a T/M on top of each other, with woofers on either side. Why is this? What is the problem with a horizontal MTM?

[breez]

Horizontal MTM has off-axis problems due to interference between mid drivers. A center speaker requires good response over a wide horizontal angle. Vertical MTM in main speakers is not problematic because the required vertical angle is much smaller.

[wigginjs]

So, a horizontal MTM configured as a 2.5way should not exhibit the same off-axis horizontal problems?

[breez]

Possibly so, but then we have the issue of horizontal non-symmetry. How severe this is depends on the design, wanted coverage angle etc. Probably not too bad as rotated 2-ways are commonly used as center channels. Then again horizontal MTM is ubiquitous in the market too! It is best to use a computer software to model the directivity of such configurations.

[gedlee]

Directivity is the missing aspect of most designs. Its not easy to estimate and it takes some work to model, but it is the diference between a good system and a poor one.

The vertical MTM will not exhibit "lobes" in the response vertically, but it will be much narrower vertically and both axis will exhibit a response change when the M polar pattern switches over to the T polar pattern.