It's very simple really. The reason you'll find so many dedicated HT speakers configured in the Diappolito(or similar) configuration with traditional dynamic drivers, is that this design tends to do the job better for perproducing movie soundtracks the way they were originally inteded for you to hear them, and mixed!!! Also, the Diappolito is smilar in pressentation a bit to the THX design type speakers, which use similar drive "sanwiched" configurations...these designs just work! Especially when you consider the wide variety of room sizes and shapes, the Diappolito design, all things equal, will tend to interact a bit less with the floor and ceiling when placed vertically,and thus reduce coloration. Also, Diappolito and THX design speakers tend to be more "focuses" and "dynamic" sounding on level playing fields, and they tend to make for faster sounding speakers, with better midrange/bass empysis(also tweeter empesis on THX multi tweeter designs), that make dialog and effects sound more pronounced and intelligeble.
Movie Mixers tend to conversely use these Designs of speakers for mixing and playback of movies and such, because the find they do a better job of portraying what's on their mixes.
Traditional stereo types of similar monitors, employing 2 way designs in "open driver" configurations, or tweeter and one driver above OR bellow, tend to sound less pronounced, with less focus to the sound, and more open in the soundstage,adding some coloration and taking away some of the specificity of sound.
My vast experience with these differences in speaker designs, leads me to conclude that, unless your using a smaller room/set-up, where your sitting disproportionately closer to the speakers than you are to the room boundaries on top and sides, the Diappolito seems to be the better choice for replaying HT mixes it seems. In smaller room set-ups, or set-ups were you have the main speakers out in the room much closer to your seating area's,and away from the walls, you can often times get good sound from movies if you set things up correctly. Overall however, your Diappolito configured speakers are going to do a much better job for this task in a wider variety of situations! Lucas Film THX spent litterally 100's of thousans of hours coming up with a desing formula that properly played back movie tracks, and they chose the more Diappolito "sanwiched" designs for speakers, because they work! Yes sometimes you can get away with some pretty good movie sound with other speakers in some situations, but it's often tricker to more difficult to get similar results over all.
Now that's simply adressing dynamic piston driver traditional speakers, comparing Diappolito's vs. more traditional stacked driver arrays.
I happen to first consider the Diappolito chioces for most of my HT system speakers, because they work! The do a great job in a small and large rooms a like, and just deliver the sound to you with more matter of factness and focus!..and usually dynamic effortlessness as well. I mean I think using dual mid/bass drivers (and sometimes multiple tweeters), tends to make for more empysis on the frequencies they're covering!..and thusely also tend to cancel out any differences/distortions the may produce between them...leaving more accurate info(if there's such a thing.). Largely, I think you'll find in a lot of bigger/modest sized room settings, when using traditional "stereo music" designed speakers(again, mostly tweeter on top/driver on bottom designs, the sound tends to be more laid-back and less involving sounding on movie mixes usually, and is a lot more colored/diffused/mixed in with dispersed sounds coming from the room as well! All of that makes for the antithesis of sound pressentation the original movie mixers intened really. Diappolito's tend to make for a more involving, immediate, dynamic, coherent and focused/pronounced sound, that just does movies right. Also I noticed Diappolitos tend to sound like they hold together better under higher levels of sound, and stay fast and tight sounding on the whole(quality speakers of course).
Howeve, all that having been sain, I personally, as of right now, use some traditional two way design "tweeter on top" and "woofer on bottom" designs in my small home theater/music set up however. Again, In small rooms, you tend to be able to get away with it a bit more because of the poximity to the speakers is often closer,and your hearing more dirrect to reflected sound ratio. Thus movies still work well on them when set-up correctly(and when using good speakers in general), and music sounds more open sounding,as recorded. I think you'll find that the MAJORITY of high end stereo/HT reviewers out there will use Diappolito's(or similar) for dedicated HT systems, and often have a variety of different choices of speakers they may use for 2 channel dubties! They are really two different animals when talking about recorded music and mixed movies...some would argue of course. Still the best of the best, "all out" top flight HT systems I've ever heard were all Diappolito bassed speaker systems! And unless your talking about using some radical higher-end horn design(wich acts like a diappolito a lot), or speakers with active amplification, used in the right set-up, Your really better off using the weapon of choice for the job...Diappolito's!
There are still some Diappolito design speakrs out there that excell at sounding more "open" sounding(as opposed to more closed in a bit with diappolito's) for music as well, but not as common. I doubt you'll find better music/HT friendly 2 way Diappolito's than the likes of the high sensitivity/ultra refined Wilson Cubs for standard Radiating passive speakers however! A speaker like this is really pretty ideal for a passive monitor for movies and music, when mated with a sub, and only surpassed by perhaps some ultra high end horns or "active" or "powered" ultra high end designs that I don't know about.
If you noticed,Dunlavy SC1av's are a popular choice for inexpensive high performance movie monitors, that might need to do music as well. I like that chioce for not too much money as well.
Anyway, it's all a bit envolved when your trying to decide on which monitors to chose, and you gotta assess the room/system set-up/and listening chioces. However, the old saying is..."if it ain't broke, don't fix it!!"
Diappolito's work for HT soundtracks and mixes, so it's really the way to go to do it right largely....
...good luck
Movie Mixers tend to conversely use these Designs of speakers for mixing and playback of movies and such, because the find they do a better job of portraying what's on their mixes.
Traditional stereo types of similar monitors, employing 2 way designs in "open driver" configurations, or tweeter and one driver above OR bellow, tend to sound less pronounced, with less focus to the sound, and more open in the soundstage,adding some coloration and taking away some of the specificity of sound.
My vast experience with these differences in speaker designs, leads me to conclude that, unless your using a smaller room/set-up, where your sitting disproportionately closer to the speakers than you are to the room boundaries on top and sides, the Diappolito seems to be the better choice for replaying HT mixes it seems. In smaller room set-ups, or set-ups were you have the main speakers out in the room much closer to your seating area's,and away from the walls, you can often times get good sound from movies if you set things up correctly. Overall however, your Diappolito configured speakers are going to do a much better job for this task in a wider variety of situations! Lucas Film THX spent litterally 100's of thousans of hours coming up with a desing formula that properly played back movie tracks, and they chose the more Diappolito "sanwiched" designs for speakers, because they work! Yes sometimes you can get away with some pretty good movie sound with other speakers in some situations, but it's often tricker to more difficult to get similar results over all.
Now that's simply adressing dynamic piston driver traditional speakers, comparing Diappolito's vs. more traditional stacked driver arrays.
I happen to first consider the Diappolito chioces for most of my HT system speakers, because they work! The do a great job in a small and large rooms a like, and just deliver the sound to you with more matter of factness and focus!..and usually dynamic effortlessness as well. I mean I think using dual mid/bass drivers (and sometimes multiple tweeters), tends to make for more empysis on the frequencies they're covering!..and thusely also tend to cancel out any differences/distortions the may produce between them...leaving more accurate info(if there's such a thing.). Largely, I think you'll find in a lot of bigger/modest sized room settings, when using traditional "stereo music" designed speakers(again, mostly tweeter on top/driver on bottom designs, the sound tends to be more laid-back and less involving sounding on movie mixes usually, and is a lot more colored/diffused/mixed in with dispersed sounds coming from the room as well! All of that makes for the antithesis of sound pressentation the original movie mixers intened really. Diappolito's tend to make for a more involving, immediate, dynamic, coherent and focused/pronounced sound, that just does movies right. Also I noticed Diappolitos tend to sound like they hold together better under higher levels of sound, and stay fast and tight sounding on the whole(quality speakers of course).
Howeve, all that having been sain, I personally, as of right now, use some traditional two way design "tweeter on top" and "woofer on bottom" designs in my small home theater/music set up however. Again, In small rooms, you tend to be able to get away with it a bit more because of the poximity to the speakers is often closer,and your hearing more dirrect to reflected sound ratio. Thus movies still work well on them when set-up correctly(and when using good speakers in general), and music sounds more open sounding,as recorded. I think you'll find that the MAJORITY of high end stereo/HT reviewers out there will use Diappolito's(or similar) for dedicated HT systems, and often have a variety of different choices of speakers they may use for 2 channel dubties! They are really two different animals when talking about recorded music and mixed movies...some would argue of course. Still the best of the best, "all out" top flight HT systems I've ever heard were all Diappolito bassed speaker systems! And unless your talking about using some radical higher-end horn design(wich acts like a diappolito a lot), or speakers with active amplification, used in the right set-up, Your really better off using the weapon of choice for the job...Diappolito's!
There are still some Diappolito design speakrs out there that excell at sounding more "open" sounding(as opposed to more closed in a bit with diappolito's) for music as well, but not as common. I doubt you'll find better music/HT friendly 2 way Diappolito's than the likes of the high sensitivity/ultra refined Wilson Cubs for standard Radiating passive speakers however! A speaker like this is really pretty ideal for a passive monitor for movies and music, when mated with a sub, and only surpassed by perhaps some ultra high end horns or "active" or "powered" ultra high end designs that I don't know about.
If you noticed,Dunlavy SC1av's are a popular choice for inexpensive high performance movie monitors, that might need to do music as well. I like that chioce for not too much money as well.
Anyway, it's all a bit envolved when your trying to decide on which monitors to chose, and you gotta assess the room/system set-up/and listening chioces. However, the old saying is..."if it ain't broke, don't fix it!!"
Diappolito's work for HT soundtracks and mixes, so it's really the way to go to do it right largely....
...good luck