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Original Message
RE: Outdated BG Radia thread over AC for Satie
Posted by josh358 on December 28, 2016 at 07:04:25:
OK, that would explain why the thread mentions the back cups. But why? that seems to me a recipe for issues at the M-T crossover point. Is he dong this to minimize cavity resonance and diffraction in the baffle?
The IRS appears to have a cardioid rather than figure 8 characteristic in the highs (24 front-facing tweeters, 12 rear facing = cardioid pattern). I remember a discussion of the IRS in which Nudell said that they'd experimented with various radiation patterns and found that a cardioid pattern provided the best imaging. I'd still say that the IRS produced the most holographic imaging of any speaker I have ever heard -- it was as if the instruments were hanging in space and you could thread your way between them.
It seems to me that monopole bass is a compromise. Dipole woofers run into trouble in the midbass because of cancellation from the rear wall reflection, but they confer partial immunity to the effects of room modes, which I think significantly improves bass realism. There are also issues at the crossover between the monopole bass driver and the dipole midrange -- the rear waves will cancel -- as well as the fact that one falls off linearly with distance and the other as the square of it. However, Nudell seems to have worked out the continuity issues in the IRS -- I don't remember the system sounding discontinuous like the Beta (actually, the Beta wasn't so much discontinuous as it sounded like the frequency bands were coming from different places!).