dragonfyr Posted July 24, 2005 Share Posted July 24, 2005 Recent posts have dealt with issues such as multiple drivers addressing the same pass band. Many are not aware of the interaction of multiple drivers and the relation between inter-driver spacing (center to center), the polar pattern, the frequency domain and resulting comb filtering. The attachments illustrate the effect of multiple drivers addressing the same pass band. Based upon inter-driver (center-to-center) spacing, the result is not simply an increase in gain, but also a significant modification of the polar and frequency responses due to the superposition of the signals within the time domain. The first illustration shows a normalized relation between the resultant frequency domain comb filtering and the polar anomalies. The second illustration, utilizing EASE, shows the 3-space polar plots of spaced drivers as well, but from a different method. This basic response is true for all cases of multiple drivers addressing the same pass band. Various configurations, such as line arrays attempt to use the anomalous result to their advantage (in this case a vertical line array will exhibit a broader horizontal response with a narrowing Q as the frequency increases along with a narrowed vertical response, thus minimizing reflections from the upper and lower physical boundaries. As these are most common in SR applications, I will not address this in much detail here, but if folks are interested in more information regarding this, I have plots that illustrate the frequency dependent behavior in depth. I will mention one unique combination of drivers that avoids this destructive interference, and that is the Bessel array. The unique characteristic of the Bessel array is that it may be used to combine individual drivers, or driver units (i.e.: speakers) in a defined manner with the result being that the polar and frequency response of the basic unit is preserved into what effectively becomes a larger, higher gain version of the original unit. This has rarely been employed commercially (an interesting story here!!), with exceptions being models offered by JWDavis and McIntosh (in their HF arrays). If folks are interested in this, I have finally been able to assemble some primary resources in PDF form. I also have in my possession one of two original copies of the original research (~4 inch thick stack of TEF scans done on 1U(unit), 2U - close and wide spacing, & 5U Line Array spaced individual drivers; and 5U, 7U, & 9U and 3x5U and 5x5U Bessel arrays) conducted by M. Lamm that formed the foundation for Don Keeles AES publication and the information in Sound System Engineering. While this research is not available for public distribution, I can attempt to address any response questions that are not addressed in D.B.Keeles publication, as well as the results for the 3x5U and 5x5U Bessels (to which Don alludes) and Line Arrays. And before others rush to adopt this configuration, there are a few aspects worthy of awareness, the most prominent (for all arrays) being the distance (number of inter-driver spacing units) required from the drivers in order for the field to coalesce, as well as substantial phasing issues between arrays. So if you have any particular requests for info, PM me and I will try to assemble those of interest.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Quote Link to comment Share on other sites More sharing options...
dragonfyr Posted July 24, 2005 Author Share Posted July 24, 2005 3-space models of multiple drivers sharing the same passband. Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 24, 2005 Share Posted July 24, 2005 Thanks dragonfyr!!! I especially like the visual of the 3D balloon plots. I haven't seen those before. I would love to see baloon plots of say the crossover regions of the woofer/squawker and squawker/tweeter of the Klipschorn with say 6db crossovers versus say AK-3 or AK-4 and ALK's Extreme Slope. What is amazing is to realize that this represents a very simple situation and to realize that as soon as a speaker is placed in a room you have in effect many multiple sources(REFLECTIONS)(ie:left/right side walls, floor/ceiling and front/back walls interacting with the speaker/speakers causing similar interferance effects). Its truely amazing how complicated the simple act of recreating music in our rooms is and that it sometimes works as good as it does. If you really think about this it should really bring home just how much the room/speaker interaction will determine what we perceive and why so many opinions differ on for just one example "the Khorns sound and imaging ability" simply because No Two Enviroments are the same that we listen in. To me the Room really is the WEAK LINK in our quest for reproducing music in our homes with todays technology. I would also like to say How Much I Appreciate and Miss The Great Work Of Richard Heyser. He was the first to open my mind to how amazingly complicated what appeared to be the simple act of reproducing music really is! Again Thanks for sharing this type of information with us! mike Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted July 28, 2005 Share Posted July 28, 2005 Mark, Many thanks for the help! Best regards, Terry Quote Link to comment Share on other sites More sharing options...
sunnysal Posted July 29, 2005 Share Posted July 29, 2005 good article and examples. thanks! tony Quote Link to comment Share on other sites More sharing options...
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