Felix: I have no "fear" of any comments or corrections that you would like to deliver. As such, have at it. As i've mentioned before, i would prefer to be publicly corrected than to be mis-informed and spreading dis-information.
As far as the "acoustic blanket" goes, this is used to minimize / damp baffle reflections and diffraction, not to "limit dispersion patterns". This also helps to flatten any irregularities in the frequency response IF the material ( usually foam or felt ) is properly applied AND the correct type of materials are selected. If one did attempt to "limit dispersion" using this method, nearfield reflections would occur with the resultant irregularities in frequency response taking place. For the record, Dunlavy evidently didn't test each pair of speakers as well as he thought prior to shipping them out the door as Stereophile did make mention of just those problems when making their test measurements.
As a point of reference that i present to help support my previous statements, here are several quotes as taken from the
Stereophile review of the Dunlavy SC IVA's:
"Remove the grille and you'll note the same symmetrical arrangement of midrange drivers and woofers around the centrally located tweeter, with heavy felt around the tweeter and midrange (a method of diffraction control for which Dunlavy holds the patent)."
"There are a couple of early reflections noticeable, however, which I assume are from the relatively firm felt used in the tweeter's acoustic environment. These give rise to the small ripples seen in the on-axis frequency response, which are subjectively benign."
If your comments were correct regarding minimized horizontal dispersion for all MTM arrays and all versions of the Dunlavy products, you would literally have a speaker that had pinpoint dispersion characteristics. Since the MTM / D'Appolito design displays limited vertical dispersion by its' very nature, your comments regarding limited horizontal dispersion would mean that the speakers would have to be aimed directly at the listeners' ears in order to maintain any type of linear frequency response.
While this might have been the case with some of the earlier SC IV's, Dunlavy later corrected this by revising the mids and tweeters that were used, completely re-designing the crossover, fine-tuning how the felt around those drivers was applied and changing all four woofers used. Stereophile makes mention of both the design changes and the differences in performance that resulted in these comments being made in the above referenced article:
"The tweeter and midrange units are the same in the SC-IV and the SC-IV/A, but each has gone through three or four generations of improvements since the original SC-IV. (The tweeters and midrange drivers in my SC-IV's are the latest versions.)"
"However, there are many ways of designing and executing a minimum-phase crossover, and the SC-IV/A's crossover uses almost twice as many components as the one for the SC-IV."
"Where the SC-IV/A's did score over the SC-IV's was in their tonal balance and imaging for the off-center listener."
"Central imaging had that "holographic" quality, but the sound for the off-center listener didn't seem to fall off as much as with the SC-IV's."
As such, one can see that the limited horizontal dispersion that you make reference to was primarily due to the poor design of the original crossover and the selection of lower quality drivers that Dunlavy made use of in their earlier production runs. As such, i must assume that the comments that you made are based on familiarity with the earliest, lowest performance versions of the SC IV's. As can be seen in the previous Stereophile comments, these obviously lacked any of the later design revisions. If you are familiar with the later SC IV's or SC IVA's, then your comments seem even more out of place according to what Stereophile reported.
While i do not know the production date of the SC IV's that i worked with, i do know that i didn't experience the majority of problems that you mentioned. If i had, i wouldn't have said what i did about placement suggestions. Nor have i experienced that phenomena ( limited horizontal dispersion ) with other MTM designs.
For the record, most all of the information that i've presented here can be found in any decent manual dealing with speaker design. By no means am i repeating anything other than common knowledge that is available to anyone willing to read and learn.
Other than that, the custom designed quad-amped speakers that i referenced in my prior post made note of all of the design flaws of the Dunlavy's that Stereophile made mention of and took them into consideration when the project was initially started. By combining these corrective steps with all of the high points of the Dunlavy's and going even a few steps beyond that point, we've never run into any of the problems that you stated. This is true even though the inspiration for such a design was directly borrowed from much of Dunlavy's own R&D and finished products.
As far as your comments pertaining to what passes as "expert advice" here, nobody here claims to be an expert. At least not as far as i know. We are simply a community of music / audio lovers (with a few video fanatics thrown in for good measure) sharing various points of view from various perspectives and backgrounds. Sometimes there is mass agreement, sometimes we are all on our own in terms of personal beliefs / experiences.
Other than that, i'm glad that you were able to find a forum that you are comfortable with and can call "home". Tell Jasmine i said "hi" and don't forget to kick the dog on the way out : ) Sean
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