Speakers that sound great in terrible rooms

Omni speakers have been mentioned several times, and there is definitely something they do right which contributes to dealing with terrible rooms: Their off-axis response has the same spectral balance as their on-axis response. Thus their reverberant sound is virtually identical to their direct sound, modifed by the room’s acoustics of course.

Now I’m going to make a claim that will probably be somewhat controversial: In MANY cases, "terrible room" is actually a speaker design issue, but it gets blamed on the room! You see, if the room was the root cause of the problem, omnis would be the WORST speakers for such rooms because they send the most energy out into the room for the room to screw up. But here in this thread we have many people who are experienced with omnis and quasi-omnis telling us the exact opposite!

What many speaker do WRONG over most of the spectrum, relative to omnis (and quasi-omnis like the Shaninians and Larsens and many dipoles) is, their off-axis response is significantly dissimilar to their on-axis response. When the ["terrible"] room reflects back a lot this spectrally incorrect off-axis energy, what we perceive is a weighted average of the direct and reverberant sound, and we make the mistake of blaming it all on the room.

(Now there definitely are room problems which clearly exist, such as too much or too little boundary reinforcement, strong bass modes, excessive asymmetry, too much or too little damping, slap-echo, and insufficient size. Speaker design can only go so far in addressing these issues.)

The fact that omnis sound good in many "terrible" rooms is imo proof that, in THOSE rooms anyway, the issue was not the room itself.

A thought experiment comes to mind: How would an unamplified acoustic guitar sound in the room? If it would suck (like due to excess slap-echo), then the room really is terrible. But if it would sound good, then the room may not be the root problem.

Based on my own experiments omnidirectional is not my radiation pattern of choice because I have concluded that less off-axis energy is actually preferable. That being said, the success of omnis (particularly in "terrible" rooms) clearly tells us what the spectral balance of the off-axis energy should be: The same as the on-axis energy.

Duke

Good points by Duke.

I have honestly been of the opinion since my first encounters with Ohm Walsh speakers many years ago that more omnidirectional speakers do things right and others are inherently flawed in design.

Omnis radiate sound in a pattern more like if a real instrument were playing, whereas conventional more directional designs shoot all the good sound mostly forward in one direction only.

The pain people must go through to try and get directional speakers to sound good supports that the approach is inherently flawed.

My big Ohm F5s were hand picked for the troublesome L shaped room they run in. Planar and tower box speakers I tried in there prior just could not cut it at all.

The fact that omnis sound good in many "terrible" rooms is imo proof that, in THOSE rooms anyway, the issue was not the room itself.

Duke,

Having a pro in the thread is like cheating. :)

Can we define good though? I mean, I agree with the on/off axis description, but! What about imaging and detail?

How would omnis compare to dispersion limited speakers like big ESL’s, line arrays or horns with narrow beam pattern?  Pro acousticians I've read say that the better the dispersion control is, the less room treatment is required.

The Omni story flies in the face of this, unless we don't care about detail. (Yes, this is devil's advocacy)

Best,

E

@erik_squires wrote: "Duke, Having a pro in the thread is like cheating. :)"

"If you’re not cheating, you’re not trying hard enough." - Gene LeBell (off topic, but he’s the old guy who choked out Steven Seagal. Twice. In the same day.)

Erik: "Can we define good though? I mean, I agree with the on/off axis description, but! What about imaging and detail?

"How would omnis compare to dispersion limited speakers like big ESL’s, line arrays or horns with narrow beam pattern? Pro acousticians I’ve read say that the better the dispersion control is, the less room treatment is required.

"The Omni story flies in the face of this, unless we don’t care about detail."

EXCELLENT points!

Literally EVERYTHING you have said here is why I don’t do omnis myself. (I use constant-directivity waveguide-style horns.)

Experiments with varying the level of spectrally-correct reverberant energy convinced me that there is a "sweet spot" above which the reverberant energy is arguably "too loud" and clarity starts to be degraded. The "sweet spot" level for the reverberant energy is lower than one would normally get from an omni or from a dipole.

The arrival time of our spectrally-correct reverberant energy matters as well, and imo a dipolar or bipolar radiation pattern is generally preferable to an omni pattern because of geometry: The path length for a bounce off the wall behind the speakers is usually longer than the path length for a bounce off the near-side wall. Imo we want to minimize the reflections arriving within the first 10 milliseconds or so (for the sake of clarity and imaging), but then after that spectrally-correct reverberant energy is generally beneficial (for the sake of timbre and envelopment). Credit to Earl Geddes for that 10 millisecond figure. Siegfried Linkwitz says something similar regarding reflection arrival times, though the figure he arrived at is 6 milliseconds.

The approach I use might be called a polydirectional (credit to the late great Richard Shahinian for that term). I use fairly directional main array and then a secondary, similarly directional array aimed up-and-back such that its energy bounces off the wall and then off the ceiling before reaching the listening area, to maximize the time delay without requiring as much distance from the wall as a dipole or bipole would. The level and spectral balance of this secondary array are user-adjustable, so that different room acoustic situation can be adapted to.

Duke