comb filtering correction techniques

[Jed]

One limitation of using a ribbon or Visaton MHT12 in an MTM is the comb filtering that is present when crossing over at a frequency where distortion is under control (3.5K or above). The observation is that one must keep his or her head in a fixed location to get an even frequency response. For some it may deter them from persuing an MTM with ribbon altogether.

So, what would happen in terms of comb filtering if one were to take the approach that Wilson does with their flagship speakers, which would involve tilting the midranges at 8-10 degrees inward toward the on axis plane/tweeter plane? Would this help or improve the limitations of using a ribbon or magnetostat, which both require higher crossover points?

Thanks,

Jed

[Johnloudb]

I don't know about the Wilson. But, with ribbons the sound does disappear when you stand up. When you listened to the R44 did you notice that this effect was significantly worse than with the R4s. Maybe lobing isn't such a big issue in that regard. I think planar tweeters have more vertical dispersion than ribbons, not sure.

I don't want vertical dispersion due the dead ceiling in our listening room. It absorbs the high frequency reflections making the highs sound more direct and "beam at you". So I'm sure I'll be happy with the R44.

[Jed]

It's hard to say, or at least make a comparison after the fact, when I wasn't really paying attention to this at the time. That said, I found the ribbons to have a more limited listening window on the vertical plane. Once I was listening in that window it sure was nice. I'm just wondering how much of it is the inherent nature of the driver or comb filtering from crossing at 3.5k, and how I can minimize it from a design perspective, if at all.

[PoorboyMike]

It's hard to say, or at least make a comparison after the fact, when I wasn't really paying attention to this at the time. That said, I found the ribbons to have a more limited listening window on the vertical plane. Once I was listening in that window it sure was nice. I'm just wondering how much of it is the inherent nature of the driver or comb filtering from crossing at 3.5k, and how I can minimize it from a design perspective, if at all.

I've thought about this too.

How much of the face plate can be machined off to match the radius of the W4? It looks like a huge face plate, so if you could take a half inch off each side, would the 1" less CTC spacing make much of a difference?

[Jed]

I don't think I'd want to go to that extent, Mike. I guess it all comes down to one's listening habits. When I'm doing critical listening, I sit on axis and it becomes a non-issue, for the most part.