1) They generally result in tall speakers, and to my ears, speaker height is closely correlated with a sense of sonic scale and grandeur and life-like-ish soundstage size and height. State-of-the-art examples include Rockport Arrakis, Evolution Acoustics MM7, Gryphon Kodo, and Von Schweikert Ultra 11. More modest examples include Raihdo TD-4.8 and Von Schweikert Endeavor E-5 Mk. II and the PBN M2!5 Jeff Tyo Special Edition.
2) Conventional tweeter-on-top/woofer-on-bottom loudspeakers give me the sense that the low frequencies are emanating from the bottom of the speaker cabinet. Even if I do not actually hear this phenomenon (and I rarely hear it because I am not very good at detecting driver discontinuity), I sometimes think I hear it simply because that is how it looks. At the state-of-the-art level it just is something I don't want to even think about.
As much as I love the Rockport Lyra, I do not believe it will ever provide the sonic scale and grandeur of the Arrakis.
An exception is YG, because with those speakers, even though the woofers are in the bottoms of the cabinets, I cannot seem to talk myself into thinking that maybe, possibly, I think I am hearing the low frequencies come out of the bottom of the cabinets.
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On the other hand, I believe more than maybe anything else in high-end audio, that implementation trumps theory. There are many woofer-on-bottom loudspeakers I like including, among many others, Wilson Audio Alexx and Master Chronosonic; YG Sonja XV Jr., Sonja 2.3 and Haley 2; Magico S5 Mk. II; and Devore Gibbon X
First off all MTM configuration is ideal for lifting overall system efficiency by 3 db , secondly the dispersion is different.
The extra mid surface also adds to the illusion you re listening to the real thing .
I think that real music reproduction moves quit a lot of air so adding membrane surface adds to this illusion of it being real .
Always have preferred d’Appolito to all other configurations in a dynamic speaker. Was introduced to them years ago with Dunlavy. Owned SC-IV, SC-IV/A and SC-V. Now have Evolution Acoustics MM3 Exacts and have been enjoying them for years. All the other short, bass driver on bottom followed by midrange and tweeter designs just never sounded right. The soundstage didn’t sound natural and balanced top to bottom.
Thats one thing i have against the big stacked wilson designs i have heard , the soundstage is a bit elevated .
They use no woofer on top like EA or side firing woofers ., so you have the MTM on top of the woofer cabinet resulting in a high tweeter placement ( MTM)
If i would built a statement speaker it would be a HPL 2 tower design /per channel so 4 towers in total , probably i would get to around 96-97 db Efficiency , with a 7-8 ohm min impedance dip for the whole system
Paper mids , nomex kevlar / honeycomb structure lower mids , textile dome tweeter all in 1 tower( possibly 2 tweeters ) , basically a double up of my current design except for adding more LM ( low mid units )
1 seperate bass tower with 4 nomex kevlar ( honeycomb structure) woofers (11 and 12 inch ),(they are big stiff and fast enough).
All passive designs ,also easy to drive so you can also put tubes on the bass , i think a lamm 18 watts would be perfectly in control per 1 side ( 2 towers together per mono block )
Regarding solid state amplification 10 watts would be enough for absolute control as is currently the case for my XPE speaker , not 10 watts SE tubes , SE lacks bass control compared to a same watt SS ( i have compared extensively )
Its then basically a LM-LM -M-M- -T-T -M-M -LM -LM design meaning low mid-low mid / mid-mid / tweeter- tweeter / mid -mid /low mid-low mid .
It would knock the socks of of all audiophiles , it would cost around 120K dealer price.
PS. you ll save a lot of money on cables as well , on my designs you dont need that BS
This will just be my opinion, and I may ramble a bit.
The D'Appolito configuration, "MTM" (midwoofer-tweeter-midwoofer) offers the theoretical advantages of vertical symmetry, more midwoofer cone area (plus a second voice coil) for improved dynamic capability in that frequency range without resorting to bigger cones, and better floor-and-ceiling interaction. Imo the main disadvantage is that if you are at the wrong listening height, there will be two different arrival times from the two midwoofers, which can degrade clarity and/or imaging. If the crossover to the tweeter is low enough (say below 1 kHz or so), this does not matter as much as it otherwise would. Very close driver spacing also helps. The most crossover-lobe-free MTM configurations use odd-order crossovers, so the devils are in the details, and my understanding is that this is one of the many details John Dunlavy got right.
The narrowed vertical pattern in the midrange region reduces the MTM's interaction with the floor and ceiling. At lower frequencies the significantly different heights of the two midwoofers staggers their floor-bounce-dip frequencies, assuming their response extends that low.
"TM" (tweeter atop midwoofer) has the advantage of only a single arrival time from the midwoofer, so it is more forgiving of a wide variety of listening heights from that perspective, but may have crossover lobing in the vertical plane that still degrades sound quality for standing listeners. Getting all of these little things right can include a juggling of tradeoffs.
"TMM" is most often seen in "2.5 way" speakers, where the lower midwoofer's top-end is rolled off. This is often seen in narrow-cabinet speakers, where the additional low-end contributed by the bottom mid woofer is used for baffle-step compensation (something I'm not a big fan of). In cases where the two midwoofers both run all the way up to the crossover frequency, their effective acoustic center is much further below the tweeter than is normally the case, which should be taken into account in the design (perhaps by using a tweeter that goes unusually low).
An imo rather elegant alternative is the Coaxial, but it's not easy to get right. Andrew Jones comes to mind of course, but Mark Seaton does outstanding work in high-output coaxials. One of the things these designers both do right, in my opinion, is that they hand off the lower frequencies to dedicated woofers - ime this is especially critical with a coaxial. And getting a midwoofer cone to behave as a benign wide-pattern horn or waveguide requires intelligent tradeoff juggling. But the payoff includes coherence from virtually any reasonable listening angle, horizontal or vertical.
At the moment I have three designs in the pipeline, and it just so happens they include an MTM, a TM, a TMM. The MTM is for a recording studio wherein the speaker/listener geometry is known in advance, and the other two are for home audio. To be more precise, what I'm doing would probably be called an MHM, an HM, and an HMM, as I use horns rather than conventional tweeters. The MHM and HMM formats are arguably attractive for theoretically allowing better radiation pattern matching with rectangular horns, while the HM format is arguably better suited to a round horn, but once again the devils are in the details.