The floor acts like a mirror, that's also why the curve has a 90 degree angle where it meets the floor. PE used to have an interesting clip of a lecture by Keele where this is explained, hope it is still there.
By the way, what Keele shows is lobing in the vertical plane as seen from a side view of the speakers. This looks very good. However, physics predicts that there will be lobing in the vertical plane as seen from a front view of the speakers. The solution presented by JBL seems better in this respect.
@ Pano #2503
Pano,
Great, I'd like to do an experiment with 'phase panning'. I am with family now to do egg related stuff and eat some really thin old school crackers, but once home I'll post on why this could be important and how to do it, and make some calculations on the time delays required, which I will PM to you. Probably just reinventing the wheel, but who cares.
Pano,
Great, I'd like to do an experiment with 'phase panning'. I am with family now to do egg related stuff and eat some really thin old school crackers, but once home I'll post on why this could be important and how to do it, and make some calculations on the time delays required, which I will PM to you. Probably just reinventing the wheel, but who cares.
The reality is that all line arrays whether they are curved or straight are going to have lobing caused by comb filtering. It will be greatest with the high frequency devices at any frequencies shorter than the dome diameters. Manufacturers always try to show their own designs in the best light and the competition in the worst case. That is just how it is. Identical test conditions or optimization of each device is seldom the end case.
It's not the first time I have seen these, I have seen the presentation you talk about from Keele
. I have read all about it I could find and that's why I have these things that nag me.I also know that the floor is supposed to act as a mirror for the CBT. It is suggested to fill in the other half of the CBT. But that still means the loudest level of sound is on the floor. Trace back the origin of the sound and you end up on floor level. There is the acoustic center of your (virtual) point source.
That's why I said I would hang it from the ceiling. But I'd rather have a 60 degree version floating between the ceiling and the floor (if you have the space)
That's why a lot of straight array designs use ribbon tweeters like for example Scaena. Another solution that is supposed to help is floor to ceiling array, this was tested by macintosh for their speaker line. I'll see if I can find the quote, it is somewhere on this board.
Exactly!
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Wesayso, got your point.
The Greatful Dead half buried in your floor seems somewhat appropriate, but on first sight it would not seem to sound very natural. Ears are much worse in their ability to locate sound in the vertical plane than in the horizontal, but nonetheless the pinna is remarkeably effective in producing vertical cues. In all fairness, I never listened to these speakers, and according to Keele it isn't a problem. I hope someone on this site has first hand experience.
The Greatful Dead half buried in your floor seems somewhat appropriate, but on first sight it would not seem to sound very natural. Ears are much worse in their ability to locate sound in the vertical plane than in the horizontal, but nonetheless the pinna is remarkeably effective in producing vertical cues. In all fairness, I never listened to these speakers, and according to Keele it isn't a problem. I hope someone on this site has first hand experience.
IT WAS A PRESENTATION.
The sim.s are a point of reference or background to start understanding the design as it was altered.
Think of it more like a poor text-book rather than a marketing brochure.. (..the reality is somewhere in-between the two). (i.e. you need the background in chapter one - to progress to chapter 2.)
The ground-plane CBT is the *domestic* version, and comparing it to the domestic Revel - reveals it's advantages (..at least with a highly reflective floor).
Almost everyone would prefer a good sim. as reality, rather than reality.
As far as it being "unfair" - hardly IT'S STATED AS A SIMULATION. He then goes onto actually provide MEASUREMENTS . He isn't saying "you'll" get the results as simulated, he is saying these are the actual results under this condition.
Of course in a small-room context you won't get those results either - standing waves will intrude. Plus, most homes are likely to have more floor absorption than "perfectly reflecting".
OK, here's 3 more files, the same voice but differently panned. These are shorter and easier to hear the effect.
The direction should be much more obvious now, as I've panned the files 50% to one side in amplitude and delayed the softer channel by 5mS (~1.7 meters) to give it distance. Those effects combined pull the sound far left or far right. Amplitude or delay alone don't pull the sound as far as both combined.
For me, the "all pan" (full bandwidth panned) pulls entirely into one speaker or side of the headphone. The lo pan and hi pan don't, and sound different. Tell me what you hear. I find these similar on headphones and speakers, you may not.
The direction should be much more obvious now, as I've panned the files 50% to one side in amplitude and delayed the softer channel by 5mS (~1.7 meters) to give it distance. Those effects combined pull the sound far left or far right. Amplitude or delay alone don't pull the sound as far as both combined.
For me, the "all pan" (full bandwidth panned) pulls entirely into one speaker or side of the headphone. The lo pan and hi pan don't, and sound different. Tell me what you hear. I find these similar on headphones and speakers, you may not.
That is good to read. In a non tapered straight line array the loudest speaker will always be at ear level, sitting down or standing up (in theory) provided the array is long enough.
As Keele's array is louder at the floor I was wondering if it could influence the perceived height. Glad to hear from at least one listener that is not the case.
IT WAS A PRESENTATION.
The sim.s are a point of reference or background to start understanding the design as it was altered.
Think of it more like a poor text-book rather than a marketing brochure.. (..the reality is somewhere in-between the two). (i.e. you need the background in chapter one - to progress to chapter 2.)
The ground-plane CBT is the *domestic* version, and comparing it to the domestic Revel - reveals it's advantages (..at least with a highly reflective floor).
Almost everyone would prefer a good sim. as reality, rather than reality.
As far as it being "unfair" - hardly IT'S STATED AS A SIMULATION. He then goes onto actually provide MEASUREMENTS . He isn't saying "you'll" get the results as simulated, he is saying these are the actual results under this condition.
Of course in a small-room context you won't get those results either - standing waves will intrude. Plus, most homes are likely to have more floor absorption than "perfectly reflecting".
Okay, I'll think of it as that "poor text-book" from now on
.
A bump for this, wouldn't want to be the guy that made people miss this. I had fun with the last files. Will listen tomorrow
. Files are in this post: http://www.diyaudio.com/forums/multi-way/177403-linkwitz-orions-beaten-behringer-what-255.html#post3434806At BAF this year, we got to hear to hear Keele's CBTs and SL's new LX521 side by side... well, in side by side rooms, which were nearly identical. I didn't hear anything special from the CBTs and stayed for about half a song. With the LX521, I wanted to stay longer and keep listening.
I don't doubt the research, but just how much of it is audible or preferred? Are there any audible benefits to controlling directivity in the vertical?
I don't doubt the research, but just how much of it is audible or preferred? Are there any audible benefits to controlling directivity in the vertical?
It's not the first time I have seen these, I have seen the presentation you talk about from Keele
I also know that the floor is supposed to act as a mirror for the CBT. It is suggested to fill in the other half of the CBT. But that still means the loudest level of sound is on the floor. Trace back the origin of the sound and you end up on floor level. There is the acoustic center of your (virtual) point source.
That's why I said I would hang it from the ceiling. But I'd rather have a 60 degree version floating between the ceiling and the floor (if you have the space)
Wouldn't hanging a full-curve CBT from the ceiling re-introduce the floor-bounce effects it's intended to eliminate in the first place?
I thought the same . . . I didn't hear anything from the CBTs to distinguish them. But the rooms were far from ideal (even the LX521 had midrange problems there that I didn't hear later at SL's house), and the samples I heard on the CBTs were terrible (some woman deep-throating a microphone is not my idea of good demonstration material). It's also not the best place to demo "home" speakers (unless you live in a sparsely furnished concrete loft) . . .
Is it the point? Transition from horn opening to space is acoustic impedance mismatch resulting in reflected/diffracted radiation. In case of circular opening the impact is greatest on axis. Polar response over angles <2degrees is so large that ears receive different signals. Small head movements also reveal this, and leads to unmasking of speaker, and unmasking of speaker location.
The absorptive power of a room is the sum of products for each surface area with its absorption coefficient.
absorption = SUM(a1S1 + a2S2 + a3S3 + .......)
In simple case in which all surfaces are constructed with same material, total absorption is product of absorption coefficient with total surface area of room. The bigger the room, the more absorptive.
Decay of coherent sound into diffuse sound in small room is quicker than in larger room do to shorter times between reflections. The diffuse field builds quicker and is louder in smaller of two rooms constructed of same material. The smaller room is more masking of direct sound than is larger room. This is decrease in D/R sound, with loss of detail perceivable from direct sound.