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In Reply to: what exactly is Hi Eff and why should I care? posted by Flyingsod on March 4, 2007 at 13:07:09:
Hello Flyingsod,Welcome! Regardless of which direction you end up going in with your speakers, the more you know the better choices you are likely to make. High efficiency obviously isn't all things to all people, but a good high efficiency system can do some things extremely well.
Generally speaking, high efficiency speakers give you better dynamic contrast than low efficiency speakers. This is because of "power compression". Most home audio speakers don't give you an honest 3 dB increase in loudness for a doubling of input power - they give you more like 2.4 to 2.7 dB increase. So when a 20 dB peak comes along (happens all the time), you may only get 17 dB out of low efficiency speakers. Since musicians use dynamic contrast to convey emotion, some of the emotion in the performance is lost right there. Many high efficiency speakers have negligible power compression at typical in-home sound pressure levels simply because there is less wattage going into heating up the voice coils.
Second, high efficiency speakers have less change in tonal balance with change in volume level. It is much more likely that woofer and tweeter have very similar power compression characteristics at normal home listening levels (which are way below prosound levels). In the case of a single-driver speaker, obviously this won't even be a consideration.
Third, horn-based or single-driver-based speakers tend to have more uniform radiation patterns than multiway direct radiators do. So here I'm really advocating horn & single driver speakers for a reason that has nothing to do with efficiency. I can go into detail about the virtues and vices arising from loudspeaker radiation pattern issues if you would like.
Fourth, I'm among those who believe specialty tube amps (SET and OTL designs) sound better than other types of amplifiers, and high efficiency and/or easy-to-drive speakers are required with such amps.
On the other hand, high efficiency will cost you in real estate if you also want deep bass extension. High efficiency and deep bass simply cannot be combined in a small enclosure - at least not by speaker designers, who are limited by the laws of physics. Marketing departments are under no such constraints.
Follow Ups:
Duke, I`ve read and enjoyed alot of your posts here, and this one hits the nail on the head. I`ve been in this hobby 30 yrs and it seems, the more I know, the less I know. There is alot of BS marketing out there, so much that I`ve taken the DIY path and I have more fun now. Your clarity is always appreciated, (as well as many other who post here.)
nt
True for so many things. First of all Thanks for your insightfull answer Duke. I think I would like to hear just a bit more on speaker radiation patterns. It sounds like what I am really interested in. Does it have to do with stereo imaging? Real estate isnt a problem for me although I don't need or want anything that thumps. I'll redesign the house if it'll make things sound better :)
Hi Flyingsod,Okay, on the radiation pattern thing:
Assuming you're in a non-anechoic room and sitting more than about 5 feet away from the speakers, most of the sound that reaches your ears is reflected rather than direct sound. The farther back you are, the more the reverberant sound dominates. We get directional cues primarily from the direct sound, but the reverberant sound contributes to loudness, timbre, and a sense of spaciousness.
So if you accept that the reverberant field matters (and not everyone accepts this), it would be desirable to "get it right". In my opinion "getting it right" has two parts.
First, we want to delay as much as possible the arrival of the first reflections, as early-arriving reflections are more likely to be detrimental to imaging or timbre or both. Typical first reflection zones are floor and ceiling bounce, and a bounce off of each side wall. We'd like a path length difference of at least 10 feet between the direct and reflected sound for those first reflections, and we'd like to have a time delay of 10 milliseconds or more before the onset of reflections. I like to use diffusion at the early reflection zones when it's practical.
Second, when the reverberant sound does arrive, we want it to be spectrally correct (not have a significantly different tonal balance than the direct sound) and be highly diffuse (which prevents image skewing and promotes spaciousness). We'd also like for the reverberant field to decay slowly (which means we don't want the room to be overdamped).
Now some of this is obviously room-related, and some is loudspeaker-related. A speaker with a well-controlled radiation pattern can be "aimed" to minimize early sidewall reflections. I like to criss-cross the radiation patterns slightly in front of the listening position, as this not only minimizes that first sidewall reflection but also gives a wider sweet spot. Let me digress here for a moment.
The ear localizes sound by two mechanisms: Arrival time and intensity. If the speakers are pointed straight ahead or only toed in a little, the image is pulled to one side pretty severely for an off-centerline listener because the same speaker wins both arrival time and intensity - the latter because he's moving more on-axis of that nearer speaker. Now if we criss-cross the speakers' axes in front of the listening position, an off-centerline listener still gets pretty good soundstaging because one speaker wins arrival time but the other speaker wins intensity, since he's now more on-axis of that farther speaker. With a well-controlled radiation pattern, this extreme toe-in also virtually eliminates that early same-sidewall reflection.
Okay the next thing a fairly uniform radiation pattern does is maintain good spectral balance in the reverberant field. Most speakers have poor spectral balance in the reverberant field, so the perceived tonal balance is skewed accordingly. Below is a link to SoundStage measurements of a 6.5" two-way. Its response is amazingly flat on-axis, but off-axis we see a dip where the woofer starts beaming and then a broad peak at the lower end of the tweeter's range because the tweeter has such a wide radiation pattern. The problem area is that lower treble region (3-5 kHz) where the tweeter is putting out a lot of extra energy into the reverberant field. This is right where the ear is most sensitive, so there's a pretty good chance this speaker would sound a bit bright and forward despite its excellent on-axis performance.
The ear is constantantly analyzing incoming sounds to see if they are reflections of a recent signal or brand-new signals. If it's a reflection, then the directional cues are ignored - this is how we tell the direction of a sound source in a reverberant environment. The ear makes this comparison based on spectral content. So if the spectral content of a reflection is way off, the brain has to work a bit harder to correctly classify it as a reflection. I believe that a long-term result of this "increased CPU usage" can be listening fatigue.
So in my opinion radiation pattern matters for natural timbre, sweet spot width, and reducing listening fatigue.
Duke
Hey Duke,Thanks again for the call. You have mentioned reverberant sound and its importance many times. I was playing around and had an experience that I felt was related. I did make a post but it didn't attract attention. So let me ask this question, especially since I saw you post that you are fond of certain tube amps (as I am).
Imagine you have 2 speakers that you are basically happy with. Speaker A is rather particular about the amp. Perhaps even to the point of what music you are playing. But with the right amp and music it is pure hair raising, goose bump causing, copping wood, "magic". Speaker B on the other hand hardly cares which amp you use. It isn't that you can't hear any difference but it is much less, regardless of music selection, volume, etc. It sounds good with any amp, darn good even, but somehow it is never true "magic".
So what is your take on this? Is speaker A better because it does "magic" or is this "magic" just some anomoly caused by a freak chance of perfect impedance match (or something along these lines)? Could it be that speaker B is clearly better but maybe has something not quite right with the reverberant sound and therefore can't quite reproduce that last little subtle nuance that allows us to hear the "magic" that good tubes amps do so well?
TIA,
Russ
P.S. If you want to get bugged with a million questions, email me sometime. I'd even let you call me grasshopper and I'd worship at your feet (but from afar cuz they stink...lol).
Hi Russ,Well, I'd pick Speaker A, but without knowing specifics I couldn't even guess as to the cause of the difference you describe.
Speaker B's failure to differentiate much between different recordings tells me that it's imposing its own sonic signature over everything. That would probably get tiring after a while.
In my opinion a speaker must meet two criteria: First, it must do something magical. That something can be timbre, imaging, impact, coherence, dynamics, inner detail, whatever. But it has to do something so well that you can close your eyes and get lost in it.
The second thing is, a speaker must NOT do anything so badly that it ruins the illusion and jerks you back to reality like fingernails on a chalkboard. It can fall short in various areas, just not to the point of distraction.
From your description, the Speaker A is capable of meeting both criteria under favorable conditions, but Speaker B never meets the first although it apparently meets the second without too much trouble.
Just my $.02.
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