@ adol...

An IB center with EB's would work, but at that point, why not have an IB2 LCR? The difference with the EB MF driver and the IB2 MF driver is pretty significant. From wider and flatter frequency dispersion to higher power handling, the PMC 75mm Soft dome would get the highest recommendation.

As far as timbre matching, the difference would not be one of great concern. With EB's you would already be at a level of resolution that is very comfortable to listen to. I've seen systems mixed and matched in most configurations. I've seen some people who actually prefer the bigger and better center over what the L&R would be. With an IB2 center your surround would just be kicked up to a higher level with the performance the IB2 yields.. As with surround your center channel is doing a lot more. I don't know what your listening would be consisting of, with more broadcast, or more surround music & cinema, or more two channel, or evenly with all of the above.

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PMC, Bryston, Purist Audio Design.