The way a speaker interacts with the room is a big part of how it sounds, for better or for worse. Imo it is possible to design a speaker to interact favorably with a very wide variety of rooms, including "terrible" ones. Several basic principles come into play:
1. The earlier and stronger a reflection is, the worse it is. So we want a radiation pattern that minimizes early reflections, which implies a fairly narrow pattern. Then ideally we want to aim that pattern in the horizontal plane such that it avoids early sidewall reflections. There are several different approaches to radiation pattern control which are viable, and it is up to the user to analyze his room and make an intelligent estimation of which radiation pattern(s) would minimize early reflections in his room.
2. The direct sound should be what sets the tone for how the speakers sound, which means we want the reflections to have the same spectral balance as the direct sound, or at least come close. (When there is a significant spectral discrepancy between the direct and reflected sound, the timbre can be degraded and/or listening fatigue can arise.) So we want the off-axis response to be smooth; that is, it should not start out emphasizing some frequency regions more than others. Given that a "terrible room" may be one which is overly reflective or overly absorptive, we might want the ability to adjust the spectral balance of the off-axis radiation without affecting the direct sound.
3. For all practical purposes there is no such thing as "the direct sound" in the bass region. It takes time for the ear to recognize those long wavelengths such that by the time the ears actually perceive bass energy, it has already reflected off the room boundaries multiple times. So in the bass region we want to take this inevitable room interaction into account as much as possible. Viable approaches include level-adjustable powered bass sections, user-selectable port tuning, EQ, a distributed multi-sub system, and some combination thereof.
Imo amp + speaker + room = "a system within a system". The speaker should interact favorably with both the amp and the room... even if the room is "terrible".
Ime fullrange controlled-pattern dipoles and horn systems designed to have very low coloration tend to work well in "terrible" rooms when set up correctly because their radiation patterns largely taking the room out of the equation, at least over most of the spectrum. In the bass region, which approach(es) make the most sense depends on the specifics of that particular room’s "terribleness".
Erik wrote: "
I remember running into an audiophile who refused to consider anything
about room acoustics. He bought speakers specifically for live,
untreated rooms.
"Anyone else? What was your solution?"
I have at times built custom speaker systems for very live, totally untreated rooms, using the principles described above. I can go into specifics if you'd like.
Duke |
Tomic61 wrote: "amp + speaker + room +ear/brain = system"
Very well said!!
By the way I’ve yet to hear a pair of the Larsens, but their innovative approach makes a lot of sense to me.
Duke
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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 |
@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 |
@br3098 wrote: "omnidirectional speakers better mimic the music we prefer in the venues we typically listen live."
I get it! Good omnis have very rich timbre and convey a wonderful sense of spaciousness, especially when they have a bit of breathing room.
The omni and quasi-omni formats are already being done and done well; I see no window of opportunity for me to offer any worthwhile net improvements. This is one of the reasons why I’m barking up different trees.
"I don’t find that typical unidirectional dynamic drivers do as good a job of reproducing complex music... as do omnis."
Agreed!
Floyd Toole fell in love with the quasi-omni (technically "bipolar") Mirage M1 many years ago. Like you, he finds that a well energized, spectrally-correct reverberant field actually enhances the clarity of complex music. This is somewhat counter-intuitive, but it has has been my experience as well. Toole theorizes that the ear is better able to decipher complex music signals when it is given "multiple looks" via multiple spectrally-correct reflections.
I was pleasantly surprised when my first bipolar speaker design had noticeably better clarity than its monopole counterpart, which used the same drivers and essentially the same crossover.
Regarding dynamics, imo that is something a good narrow-pattern horn speaker does well, and not just because of its lack of thermal compression. You see, dynamic range is partially a function of how loud the in-room "noise floor" is relative to the direct sound. To the extent that the reverberant energy in the room constitutes a masking "noise floor", it can reduce the effective dynamic range. So imo there’s some juggling of tradeoffs involved in this area when it comes to radiation pattern width. Or, as you far more succinctly put it:
"Different strokes."
Duke |
@mapman wrote: "Note that Ohm Walsh are not full but rather pseudo omni (polydirectional?) to manage the reverberative field better in most rooms. The driver is physically attenuated with absorbing material inside the can in the wall facing directions." Now we are getting into the fine details of a highly evolved speaker design, the Ohm Walsh! Imo there is at least one very good argument for their choice. For the sake of brevity (which is NOT my strong suit!) I have been saying that the reverberant sound should have the same spectral balance as the direct sound, but actually it should have a little bit less top-end energy. This better approximates what we would hear in a large venue: Because of the long reflection path lengths in a large venue, the air itself somewhat attenuates the top-end energy in the reverberant sound, relative to the amount of top-end energy in the direct sound. So I agree with Ohm, and do something similar when "voicing" my own designs. For a more in-depth discussion, see Robert E. Greene’s article entitled "Records and Reality: How Music Sounds in Concert Halls": http://www.regonaudio.com/Records%20and%20Reality.html Duke |
Heaudio123 wrote: " I would argue that unless the speaker has poor/uneven off-axis response, then it is the room..."
Totally agree!!
Heaudio123: "...and I don’t agree with your argument about Omnidirectionals amplifying room irregularity, as they actually have the opposite effect."
My wording was obviously poor; I am NOT arguing that omnis amplify room irregularities! Quite the opposite in fact. Here is what I should have said:
IF room irregularity was the problem THEN omnis would be a bad choice for "problematic" rooms; but omnis are clearly NOT a bad choice for such rooms, thus we can conclude that room irregularity is not the problem.
(In terms of syllogistic logic, my argument takes this form: "If A then B; not B, therefore not A".)
Having hopefully cleared up the above-mentioned poor communication on my part, I agree with pretty much everything else you have posted in this thread. In particular you mentioned line source speakers... ime the 45-degree-pattern SoundLab fullrange electrostats work extremely well in problematic rooms, given sufficient distance to the wall behind them.
Duke
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@nonoise wrote: " That bit of trivia just made my day. "
[Way off topic] As it was related to me:
Some of Gene LeBell’s judo students were doing stunt work for a Steven Seagal movie. Gene was there and objected to one particular stunt on the grounds that it was too dangerous. Seagal suggested that if Gene’s students weren’t tough enough to take the falls, then he’d find others who were. Pleasantries were exchanged, including opinions as to who could kick who’s @$$.
At some point Gene decided that further discourse was likely to be inconclusive, so he took Seagal down and choked him out.
Upon regaining consciousness, Seagal protested that that had been unfair because "I wasn’t ready." Whereupon Gene replied, "Are you ready now?" and took him down again, this time choking Seagal to the point of soiling himself.
I presume there was no more filming that day.
Anyway there was a lawsuit and a settlement and Gene is not allowed to comment on the alleged incident. [/way off topic]
Duke
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Dborden702 wrote: "I used to attend many audio shows. The first thing I would look at when walking into a room was how many acoustic room treatments and system tweak toys were in play. The speakers and systems that impressed me were the ones that had none and sounded great."
Nice to hear you notice and appreciate that when you come across it!
[brag] When someone speaks up at an audio show and says they like what they’re hearing in our room, I’ll sometimes say, "the secret is all the acoustic treatments we use." Whereupon they look around the room and notice that we aren’t using any. Just bare hotel room walls.
However the best was when we showed with an industry veteran electronics manufacturer who remarked that this was the FIRST time he had shown in a room where "we weren’t fighting against the room the whole time." [/brag]
On the other hand... having said all that, if the sound in our room sucks, I can’t very well blame it on the room now, can I?
Duke
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Erik wrote: "One secret, which an ASC guy told me once, but I agree with, is listen to the music in the hallway. You can go up and down the hall and quickly pick out the well tuned rooms without ever having to walk in."
From outside the open doorway, with NO line-of-sight to the speakers, ALL you can hear is the reverberant sound. And if that reverberant sound is spectrally correct (and the dynamics are preserved), there’s an excellent chance the sound in the room is likewise quite good.
This reverberant sound is dominated by the speaker’s off-axis response, and is of course modified by the room, but it would take some very capable targeted room treatment to "fix" a speaker which has inherently poor off-axis response.
On the other hand, an unamplified voice or acoustic instrument would sound totally convincing from outside the room assuming the room isn’t absolutely dreadful, imo in large part because the off-axis energy of the unamplified voice or instrument is inherently correct.
So while I understand what your ASC guy is saying, listening from outside the room can tell you a great deal about the speakers even if there are no acoustic treatments in play. Among other things, a spectrally correct reverberant field is conducive to long-term fatigue-free listening, assuming the direct sound is also correct.
I don’t have anything against using room treatment, but if your speakers start out with spectrally-correct off-axis energy, then your room treatment can be focused on enhancing something which is already pretty good, instead of needing to focus on fixing something which isn’t. (Examples on request.)
Erik again: "Honestly, I simply don’t know how audiophiles audition most equipment in a hotel room, at all."
I understand your skepticism which is why I had hoped we could cross paths at an audio show.
If the speaker system effectively takes the room out of the equation, then the room is no longer superimposing its signature atop every piece of music you play. This would be a situation where you could audition equipment in a hotel room.
Duke
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