von Schweikert designs are not time coherent.
Yet, Albert makes very nice sound because:
1) He knows how to get the most out of the 4th-order approach (the only one that makes sense if you have to/choose to give up time coherency).
2) He makes a good cabinet- with proper placement of damping materials inside (it sounds like), and they are strong, fairly slim.
3) He chooses linear drivers, unlike most of what is out there.
4) Really a part of (1)- Albert is one of a few designers that knows mathematically and empirically most of the factors that influence the selection of the actual acoustic crossover points. Not too many do, as it takes years of homework in Physics, and then years of listening, measuring and designing to prove to your ears what is right or wrong with that Physics-based math. Electrical engineers are not taught this math (since the world went digital)- which is why there are so many non-musical speakers out there.
Recommended recording- Hugh Masekela's album "Hope" (CD). Stunning dynamics and excellent musicianship! The Burmeister sampler uses one of the cuts found on this.
Hugh M. is a horn artist, so this disc is not pretty at nightclub levels on non-time-coherent speakers that have a crossover point in the 2-3kHz range. We'll play it in `Vegas on our Continuum 3s, at the THE Show.
Remember, Mr. Bischoff, that there are many physical, electromagnetic and acoustic factors behind achieving time coherence. Those specific design factors are a checklist of well-known concepts, any one of which ignored means no coherence.
They include factors most of us have heard about:
uniform diaphragm motion,
small diaphragm/cone/dome size vs wavelength,
diffraction reduction,
crossover time delays,
time delays caused naturally by the enclosure tuning.
What a layman lacks is a rule of thumb, some numbers, for when "uniform" is "good enough" (as nothing's perfect), or a diaphragm size is "small enough", or diffraction low enough, or what the actual acoustic delay times are vs. frequency.
Those give enough information for a layman to choose music that will reveal a speaker's flaws immediately- some of which he probably can live with. This info will be on our website shortly, along with a "recommended recordings" list that makes sense to challenge a system with.
In the long run, Mr. Bischoff, you would find that phase error in speakers affects dispersion vs. frequency. It also affects dynamics vs. frequency, and imaging vs. frequency. It affects hearing the rhythmic pulse, the emotional inflections. That is, if one plays a wide variety of music. But if a listener sticks to tried and true recordings only, then he is not investigating very far into any problem with the system or speakers. Using a wide range of material with which you've become familiar speeds up speaker evaluation and system tuning.
Anyway, thanks to all for their kind comments, and Happy New Year to everyone at AudiogoN!
Wish for Peace in the new year.
Best regards,
Roy Johnson
Green Mountain Audio
