Gary P said:
I don't compensate for the off axis response. I don't feel that better imaging comes with wider horizontal dispersion. I prefer speakers with a narrower dispersion angles to cut down on the clutter of reflections from the side walls. Reflection control is what led me away from true open baffle to the damped U-baffle. To my ears it seemed that the reflections off the rear were limiting the depth of the perceived image to the rear wall. With the damped U-baffle the image extends way beyond the rear wall of my living room. My thoughts on this is the reflected sound from the rear of the OB mids was louder than the embeded clues of depth from the main sound from the speakers. I'm much happier with less room reflections, and the narow dispersion of the Beta 8's at HF and the RT-8 tweeters supports this.
I took a look at the http://www.audio-consulting.ch/
webpage. I see what you mean
Gary
Trust me on this one.. room reflections at higher freq. responses in GENERAL do not alter the sound any more than to alter the freq. balance and and slighty diffuse imaging/soundstage. There are 2 significant deviations from this however:
1. Near correlation above (aprox.) the modal region - i.e. when the operating freq.'s length is within or almost within the reach of a boundry.
2. In-Phase reflections above (aprox.) the modal region - i.e. when the reflection is a product of reverse phase signal (i.e. the rear output of a dipole reflecting off of a boundry).
Now the large heil you use to have had a problem with number 2.. and the HiVi driver should not have this problem unless you have removed the back enclosure on it. (..and it sounds like you haven't.)
Other than that, most of your response (aprox.) above the modal region is omni (at least within the frontal 180 degrees) with a depressed off-axis response slightly between 1kHz and 6 kHz, and greatly depressed off-axis from 6kHz on up.
Imaging specificity and seperation are largely the product of amplitude from 1kHz up. With that in mind consider that we don't just hear the on-axis response.. NOR do we simply hear an averaged response (..because of our ability to seperate direct from reflected sound with time). What this means is that you are not getting the seperation (or width) that you should be getting (i.e. the images are being compressed between the loudspeakers). I'd bet you have never heard an image, (other than a phasey image from something like "q" sound processing), beyond the outer boundry of your speaker (even though on some recordings you should).
Essentially your premis is a derived misconception - that seems to have its genesis from SL's work. (..and BTW, its VERY common.) Strangely though you'll note that SL does not use a dipole higher in freq. - and its likely that what he likes about the midrgange as high in freq. as it is - has nothing to do with the radiation pattern, but instead the lack of reflections, pressurization, and air flow resistance that can come with a boxed midrange.
Well - I'll hope you consider this, and perhaps do some experiementation (..and hopefully achieve better sound as a result). I can't think of anyone on the electrical end of things I respect more (..well perhaps Sakuma San).
ScottG,
You've brought up a very interesting topic about "separation". Are you saying that to achieve the imaging outside of the width of the speakers requires good off axis response in the higher frequencies? I'm getting close to the response I want with my current work in process, but haven't really worried about off axis response. I was thinking that the outside the speakers magic would come through room tweaking, but what you are saying makes intuitive sense. I interpret you to say that for good separation we need good HF dispersion, so that the side wall reflections more naturally correspond in amplitude to the direct radiation of the higher frequencies, in order for our brains to interpret everything properly. Did I get the gist of what you are saying correct ?
You've brought up a very interesting topic about "separation". Are you saying that to achieve the imaging outside of the width of the speakers requires good off axis response in the higher frequencies? I'm getting close to the response I want with my current work in process, but haven't really worried about off axis response. I was thinking that the outside the speakers magic would come through room tweaking, but what you are saying makes intuitive sense. I interpret you to say that for good separation we need good HF dispersion, so that the side wall reflections more naturally correspond in amplitude to the direct radiation of the higher frequencies, in order for our brains to interpret everything properly. Did I get the gist of what you are saying correct ?
johninCR said:
V-E-R-Y interesting..
D .. this is something of "holy grail" topic that you'll have a difficult time finding elsewhere. A subject I would have broached and delved into in the "second look at SL's Pluto" thread I tried to start.. ah, well - to many putz's to little time.)It has NOTHING to do with side wall reflections generally. In fact you could just as well have no side walls (or side walls with maximum absorption) and achieve the same effect (..though without the increase in upper freq. averaged response or the slight diffuse character that reflections cause).
It has EVERYTHING to do with amplitude* and time, (from acoustic center), in the horizontal plane (primarily with in the frontal plan of 180 degrees) from 1kHz up to around 13kHz (depending on the direct sound being reproduced and its side-band decay).
That's all I'll say about this at this time.
*btw, I think it also has something to do with pressurization beyond amplitude (i.e. intensity vs. time in short intervals).
ScottG said:
V-E-R-Y interesting..
It has NOTHING to do with side wall reflections generally. In fact you could just as well have no side walls (or side walls with maximum absorption) and achieve the same effect (..though without the increase in upper freq. averaged response or the slight diffuse character that reflections cause).
It has EVERYTHING to do with amplitude* and time, (from acoustic center), in the horizontal plane (primarily with in the frontal plan of 180 degrees) from 1kHz up to around 13kHz (depending on the direct sound being reproduced and its side-band decay).
That's all I'll say about this at this time.
*btw, I think it also has something to do with pressurization beyond amplitude (i.e. intensity vs. time in short intervals).
Scott,
Yes, emphasis on the "very", and I hope "(not) at this time" means you'll share but are just too busy right now. It sounds like it needs it's own thread. Please include "separation" in the subject, so I don't miss it.
You lost me with side wall reflections not mattering, unless somehow we are able to sense the width of the direct wavefront and the amplitude along that width.
Sorry about hijacking the thread, but it seems worth the hijack.
johninCR said:
Yup, but we have expended more than enough of this thread - and it only *just* maintains a relationship with the topic. At some point I might - but you would be surpised at how venomous some can get on this subject - as if they have bought into a "religion" that could not possibly be wrong (..which makes me more than a little reluctant). I really extended a LOT of information here that I probably otherwise would not have - but I really respect Gary. (.. try looking over his website to see what I mean.)
http://www.pacifier.com/~gpimm/
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