I get amazing depth of imaging with my old setup. The width is very good as well, it can go well outside the speakers, but it's the depth that I find astonishing. It's focused, and I can hear if something is 50ft behind the speakers or a few feet in front. I put this down to having quite directional old big panel 3 way speakers, Castle Conway IIs. I've cleaned up the sound a bit with better crossover components and internal wiring but mainly I think it's because there's 3 cone speakers that don't excite room resonances much because nothing much gets squirted sideways. I can have the sound really loud and stand to the side of the speakers and it's quiet, so there's nothing much to hit the walls and bounce off basically, so I don't hear the room acoustic, I hear the recording environment acoustic. Small sweet spot though, but with fantastic projection. Play one speaker and it still sounds like stereo compared with anything else I've tried at home.
No, fairly inert room here. By stereo I don't mean left/right. I mean back/front effects are still evident.
This can be very difficult to pin-down because it involves human perception. Soundfield depth production is a psycho-acoustic effect. To simplify finding an answer, I suggest that we eliminate the loudspeaker because the differing radiation patterns of different loudspeakers the issue. What's more interesting to note, as you do, that differences are apparent with a change only in the electronic components. What's, perhaps, even more interesting still is that differences in apparent depth (spaciousness?) which can be heard using only a single loudspeaker.
Getting back to basics, there are only three ways in which an electronic component can alter the waveform which is ultimately sent to a loudspeaker. Which are amplitude, frequency, and phase. Logically, perceived differences in depth must begin with physical differences in the manner in which a component alters one of those three physical parameters. Given this, one can see how two speakers aren't absolutely necessary to hear such changes. Amplitude, frequency, and phase changes can not only occur between channels but within a single channel. Not only could amplitude and phase be altered versus frequency, but frequency itself could be altered versus frequency, producing harmonic and/or intermodulation distortion. All within the same channel. Where does that leave us? Well, at the end of the reproduction chain waits our human perceptual system. Our hearing, and how it interprets changes in waveform amplitude, frequency, and phase determine all of the various audiophile effects which we perceive.
I suppose, the real question you are asking is, how can we predict which waveform alterations (or absence of alterations will improve our illusion of depth, and thereby, know which components or technologies (tubes vs. transistors, etc.) will provide some desired listening result. I suspect that the entire playback chain, including our hearing psycho-acoustics, are too complex to provide us a simple analysis metric. Perhaps, the best way will long remain a personal listening evaluation with our own ears, within our own systems, within our own rooms.
Getting back to basics, there are only three ways in which an electronic component can alter the waveform which is ultimately sent to a loudspeaker. Which are amplitude, frequency, and phase. Logically, perceived differences in depth must begin with physical differences in the manner in which a component alters one of those three physical parameters. Given this, one can see how two speakers aren't absolutely necessary to hear such changes. Amplitude, frequency, and phase changes can not only occur between channels but within a single channel. Not only could amplitude and phase be altered versus frequency, but frequency itself could be altered versus frequency, producing harmonic and/or intermodulation distortion. All within the same channel. Where does that leave us? Well, at the end of the reproduction chain waits our human perceptual system. Our hearing, and how it interprets changes in waveform amplitude, frequency, and phase determine all of the various audiophile effects which we perceive.
I suppose, the real question you are asking is, how can we predict which waveform alterations (or absence of alterations will improve our illusion of depth, and thereby, know which components or technologies (tubes vs. transistors, etc.) will provide some desired listening result. I suspect that the entire playback chain, including our hearing psycho-acoustics, are too complex to provide us a simple analysis metric. Perhaps, the best way will long remain a personal listening evaluation with our own ears, within our own systems, within our own rooms.
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My take on hearing stereo effects with one speaker with regard to psycho-acoustic effects is this... we just need to be able to hear everything! By everything, obviously it's frequencies, phasing, amplitude stuff, but when we listen to reproduced music/speech there's usually an awful lot of crud added in the form of resonances in mainly loudspeakers, distortions in both electronics and loudspeakers, and this crud masks the perception of low level information like subtle reverberation which gives spatial clues to our brains, so 99% of the time we never hear it and the soundstage is flat as a pancake. A great system lets us hear these clues because there's much less noisy junk masking them and we get the big soundstage. Perhaps some systems even enhance these clues?
I would make sure the foam was NOT cut in a circle around the tweeter, since that might set up a standing wave at the width of the hole. Instead try a star shape - think of cutting with pinking shears but much deeper. I had good results with four points, as described above, but more may work just as well. It's the two dimensional analogue of an anechoic chamber, save you're absorbing the surface wave leaving the tweeter instead of a plane wave in space hitting a wall.
Bob, would you be willing to share the details about what you did to the Carver Hologram?
My C-1 preamp already has a wide/narrow button from the C-9 schematic, and the -3dB EQ from the C-4000 schematic. I still have a button on the front that I don't use and I'm looking to make it into something else. I really like the hologram but still I listen mostly without it.
Regards,
Tom
Soundstage and some of the other greatly desired illusions can be greatly
altered by relatively small alterations. Just readjust the operating point of
something by a few percent and
poof....
In between digging out the last few days I've kept warm by soldering up a preamp. Started with 6BX7 in the Tubcad CCS style, it was warm, dark, full and rich sounding but way too noisy. A rewired it to a 6SN7 in the same topology. Lighter, more open but still with nice tone but also too noisy. Switched it over to SRPP at the same operating points. Noise was greatly lowered, sound stage opened up a bit (the others were very nice to begin with) but....sound was thinner, brighter less punchy but more detailed. Not the best synergy fro the class D module it was driving.
I went back to the CCS style and worked on the power supply to clean up the hum. Still needs work.
The point is....the same tube, power supply and parts but different topologies make enough difference to easily hear. Some things better some things worse.
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