I can understand why poor off-axis response would matter in a venue, but in a dedicated listening room does a narrow "sweet spot" matter much? This room wouldn't be used for entertaining. Wouldn't beaming improve imaging as there would be less reflected sound from adjacent surfaces?
Jorg
Hello Jorg
That's a really good topic. I think it depends of your room and what you own personal preferences are. I have 2 systems up and switch between them all the time. One is using a 100x100 wave guide the other a 2307/H94 lense and an 077/2405. What really matters is having a sweet spot large enough to cover the area where your seating is. Both can methods can sound good if they are set up right and are compatible with the room they are used in.
Rob
Contemporary thinking is that uniform power response matters at home as well.
Reflections are occurring at other frequencies which have variably wider dispersions; the objective is to maintain them in a controllable fashion across the entire spectrum, hence constant (controlled) directivity....
http://www.harman.com/about_harman/t...eadership.aspx
Originally Posted by 89-300ce
I agree that it is a very good question and that your needs/preferences and room can play a significant roll in determining the relative importance to having a wider area of coverage.
It can certainly be shown objectively that beyond a shadow of a doubt a uniform power response is the ideal. That said, for those who do their critical listening primarily in the sweetspot and have proper speaker placement and rooms that are not overly live, there are many speakers out there with average to adequate power response that image better and just plain sound better than many others with remarkably uniform power response.
Essentially it is one of many variables. In pro sound I think it is significantly more important than it is in a typical home environment. If you use your system more of a "background" music system and want even distributed sound over a wide area it may be very important to you... if you have your speakers near reflective surfaces it may be very important to you... though simply having a narrower power response will also work, but if you have a more typical "audiophile" setup with speakers that are away from reflective boundaries, some room control, and listen from the "sweetspot" and require good imaging, I'd suggest it is less important than many of the other variables in quality playback.
Widget
In SR, we generally loath wide dispersion horns, and "stack the stacks" accordingly to avoid horn overlap minimizing the more audible of comb filtering. That said, in smaller, club systems with maybe only one main per side, wide dispersion is preferred to avoid "sweet" spots. So, both have applications.
For me, at home, I also prefer wider dispersion - it allows much of the listening area to be preferred seating...
I'm not sure this holds. Imaging can be quite effective - maybe more so? -in wide dispersion. With a wide pan to aspects of the mix, seating anywhere in the "preferred" seats - even hard L or R - can experience excellent imaging.
bo
"Indeed, not!!"
I think Jorg may have been thinking of the older style horns.....
It depends on what you mean by beaming. If you are refering to mutiple lobes in the near or mid field I would say it is less than satisfactory as a smooth horizontal disperison is prefered over say a 90 degree arc.
If your side walls are near the loudspeaker (within 2 feet) then yes early reflections have an impact on the sweet spot. Some people use it to advantage to broaden the sweet spot while others prefer a narrower sweet spot.
I think a lot depends on your room dimensions and where you sit and do most prime listening.
The newer constant directivity horns in domestic systems attempt to provide smooth dispersion over a controlled coverage angle and also control the far off axis dispersion to avoid room reflections.
When it comes to horns I favour non bi radial/constant directivity types although I have not heard the most recent JBL developments.
Wave guides are another option (see Earl Geddes web page)
Ian
- It may be time to bring up that JBL themselves have backtracked some ( at least to me ) at always employing a wide constant coverage horn in their top products. They seem to have done this for the sake of imaging .
- "Defined Directivety"( as I interpret 3 different systems ), is a means to an end to blend in ( and ultimately mimic ) factors that enhance imaging.
- One of those factors is a UHF pattern that's ultimately narrower than the pattern of the horn ( as found down at the crossover point ). If you look at both Everest Horns ( as well as the H3100 ) you'll understand what I mean ( it's all in the throats' entry angle being narrower than the final 50% of the horn bells' flare ) .
There's only one true "sweet spot," geometrically, where the listener is equidistant from the primary sources, L & R. Mr. Widget emphasized this point by sitting on Bo's coffee table.
Outside that plane, there are response anomalies, but at least with constant directivity and uniform power response, the fundamental response from each source is uniform.
The defined directivity horns combine that with amplitude compensation. The SPL increases off-axis inwardly to maintain L/R balance off center.
It's a "trompe l'oreille" that works to effectively generate a phantom center image from different listening positions. I believe it was abandoned in favor of a center channel, which does a better job of that, and also sells more speakers.
[Still good for two-channel music, tho, 'til multi-channel takes over....]
I agree.
Personally, I find the bi-radial designs to image rather poorly... they measure very well and are likely a boon to the pro-sound world, but in a monitor/home playback roll they tend to screw up depth perception (flatten it) and can be less specific across the horizon... these effects vary from horn to horn and are gross generalizations, but in my experience listening to quite a few variants, I am generally not thrilled with them.
Yep... though that spot is wider with some designs and tighter with others... the tractrix designs for example can be outstandingly holographic, but moving your head collapses the illusion.
It is kind of like a sonic "trompe l'oreille"... and it can be startlingly compelling to listen to. More than just a phantom center it can also create quite a sense of depth. This effect is more important to some and less to others, for me I really demand it from a better speaker... a speaker that only sounds accurate, dynamic, musical, etc. that can not create this holographic illusion is just not it for me... of course a high quality mini-monitor that is an imaging champ but can't reproduce the dynamics etc. of a 4333 is also a disappointment.
Maybe in SR... the qualities that make an outstanding SR system are not always the same as those in a monitor/home playback system.
Interestingly, I have heard for years that extremely wide dispersion is required for good imaging. I have also heard that it is critical to have your system time aligned for good imaging...
I have heard excellent imaging from wide dispersion, time aligned systems... but I have heard excellent imaging from beamy systems that were obviously whacked in the time domain. I do not profess to know what it takes to get a system to image well, but I do know a few factors that tend to mess it up.
Widget
This my be a little off topic but I know at least one thing that helps. Matched driver pairs and really close level matching between the drivers. I have found that can really help nail things down.I do not profess to know what it takes to get a system to image well, but I do know a few factors that tend to mess it up.
Rob
Widget
I only heard Kent's mod's Altecs for a short time. I was impressed with the horn treatment and the TAD's!
These days I am leaning more towards wave guides...to control early reflections which I think are part of the depth problem and because they offer a nice acoustic impediance match going from the large surface area ie a 15 inch driver to a small direct radiator ie a 1 inch dome.. while also offering significant reduction in distortion and power compression.
http://www.customanalogue.com/elsino...VER%20MATCHING
This is an extreme example. No I dont consider this type of waveguide to be a horn as such as they only offer gain an octave above the crossover point but they certainly control early reflections.
Anyway here is some food for thought.
Back to area 51 for the afternoon!
http://www.diyaudio.com/forums/showt...26#post1237926
http://www.diyaudio.com/forums/showt...threadid=93530
http://www.customanalogue.com/elsino...nore_index.htm
And this gest to the point Widget started to make a few posts back, about phasing and time-alignment.
It's like experiencing air conditioning for the first time - once you know the difference, there is no going back...
bo
"Indeed, not!!"
As Ian surmised, I was thinking of the older style horns, my 511b’s, which have a reputation for beaming in the higher frequencies. I can only expect that to increase when I try to augment their HF performance with the BMS drivers.
Like every question I’ve asked so far regarding speakers the answers are less clear cut and more complex than expected so I end up doing a lot of reading.
Zilch’s link to Harman had some interesting articles which, like the replies in this thread, suggest that good imaging is a combination of both speaker and room interaction and there are no absolutes, except I suspect, good driver level matching. For this driver level matching I would purchase components from a maker known for close tolerance manufacture. Sequential serial numbers would also help I suppose.
In an anechoic chamber off-axis performance to the outside of the speakers, away from the sweet spot, shouldn’t matter. I would expect a narrower sound stage, definitely not extending past the speakers, but otherwise ok. There shouldn’t be any room effect from the side walls to muddy the image.
Regarding the “sonic trompe l'oreille”. Wouldn’t this be similar to crossing the axis of the speaker ahead of the sweet spot? I’ve tried this and although the listening positions adjacent to the center where better, the sweet spot had lost a lot of the width of the sound stage. Wouldn’t, by extension, strong off-axis performance to the inside of the speakers also narrow the sound stage?
Depth. Is it possible to have depth in an anechoic chamber or do you need reflections from behind the speaker to achieve this?
Jorg
Yes, similiar, but the two sides must have constant power response (the FR can't be changing with angle,) while the SPL changes in a precise manner to maintain balance, i.e., the two sources must vary reciprocally with lateral movement of the listener(s).
The Everest I manual describes how toe-in must be used and finely adjusted to have it all work optimally, even employing those purposely-designed horns. I'd say the chances of getting that to happen using just toe-in and random horns is virtually nil, though the width of the perceived sweet spot expands somewhat in the alignment you suggest, with just about any drivers.
H2600/3100 horns seem to accomplish the effect more easily, even though they appear to be merely a truncated version of the Everest I horn. The trick works, and it is astonishing, even disconcerting, when first experienced....
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