Which speakers do the hologram thing?

What Sean has heard with the AvantGardes, I've heard with the A-Capellas, which are also modern horn loaded speakers. I see his point about dipoles, radiating out of phase towards the back wall. However, when you listen to live music in a room or hall, you never just have sound reaching your ears in phase, having all sorts of reflections from everywhere in the listening area. This is probably one of the reasons, why a well set up pair of dipoles in a carefully treated listening room can sound uncanningly real, more real in fact, than the A-capellas, which though beautifully holographic, will sound just a tad too "pure", ethereal, speak artificial, compared to say Sound Labs or Quads. Though more holographic, they cannot really sound "dirty" like live music and dipoles often do.

I agree with everyone that has mentioned Spica speakers. But nobody has mentioned the best Spica speaker. The designer himself said he liked the TC-60's the best. I have to agree with him. These speakers in a large room throw an unbelievably large soundstage.

Detlof, the thing with live acoustic instruments is that all of the sound is initially reproduced in phase and then is "distorted" or "delayed" by room acoustics & reflections. A single full range driver that radiates omnidirectionally in phase follows the same basic principles of the instrument it is trying to reproduce AND falls prey to the same culprit i.e. "room reflections" in like manner. In direct comparison, a dipolar driver is already distorted in comparison since it is contributing out of phase output at the same time it is in phase. It only gets worse from there in terms of the even greater problems associated with room reflections, etc...

I wonder what a panel type speaker sounds like with the back wave effectively nulled ? I've heard of guys building carefully thought out "enclosures" onto the back of them and being VERY happy with the results. This would give you the excellent transient response associated with these designs, get rid of the out of phase contribution that the back wave produces, increase low frequency output due to the lack of cancellation, should make placement a little easier, etc...

My thoughts are that a relatively deep "D" shaped cabinet with a curvature at the top and bottom would work best for something like this. That type of a design would not have any corners to produce standing waves nor have any parralel surfaces to aid internal reflections. An open "pocket" directly behind the panel would act as air spring tensioning, maintaining the panels linearity. The walls of the cabinet would be lined with a thick layer of insulation for internal absorption purposes.

I know that Newform markets ribbons something like this ( not sure EXACTLY how they are built ), so that may be something to look into. I don't think that any of them offer enough surface area to do low frequencies though, so it somewhat defeats the purpose of what i had in mind. Then again, we would end up with a front firing design that would probably lack the dimensionality, space and air that multi-directional designs seem to offer. Oh well.... Sean
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Sean, you are dead right of course. It was the good old Quad 57, which had the backwave at least partially blotted out by a fairly thick felt layer and this speaker, especially in the HQD version threw an incredibly good soundstage. Many people preferred the 57 to the later iterations for just that very reason. Unfortunatedly the thing never played really loud and you had to sit exactly in the sweat spot to get the highs right. I've experimented with blotting out the back wave, but very dilletantly and unsuccessfully. I find the idea you bring up fascinating, but I'm not knowledgeable enough in these things to design or even dream of something similar. Besides, with my setup, it would be impossible anyway.

sean: the only speakers i've ever heard that produce a believable 360º dispersion pattern are the radiostrahler mbl 101d's. the first few times i heard them at dealers and ces rooms, i couldn't imagine anyone's wanting them, much less at the price demanded. i've heard them now, properly setup in a home listening environment. they're driven by a pair of accuphase a 50v's (they really NEED the power) from a boulder 2010 pre, a burmester dac and transport and all connected with tara, the zero ic's and tara, the one cables. they do sound fabulous. ( and why shouldn't they with >$110k in electronics and wire?) but, truth be told, i still prefer my 3-way boxes; i can, literally, walk from my sweet spot to a position behind the speakers and perceive at every point a holographic image. what's more, my speakers also pass another critical test, IMO. when heard from another room, they sound like they're producing a live, albeit amplified, performance. -cfb