A good tweeter can give you the same immediacy as an electrostat but there is no real substitute for the type of sound that an electrostat produces. A ribbon tweeter or a magnetic planar speaker could give some of the same magic I guess.
An overly simple answer for being able to potentially replicate an electrostatic with a dynamic speaker is getting a dynamic speaker which has the capacity for very high resolution/transparancy, but not artifically up tilted. Not easy to do and not especially cheap. However there are several designs that come close.
The results are easily compromised by improper electronic's, in fact the more transparent/resolved the speakers the more critical the electronic's become, however you can use lesser electronic and all you will do is reduce the speakers sense resolution/transparency, you need not experience poor sound as a result.
Electrostats on the otherhand have built in compromises as well. They are usually set-up critical because they radiate equally in two directions and the treatment of the rear wall and placement from it are highly critical. Compared to dynamics they are usually compressed dynamically and limited in maximum output levels. The really good ones are also very sensitive to the electronic's, crap in = crap out, no cream and sugar to cover up the effects of inadequate electronic's.
Dynamics are usually more easily accommidated in smaller rooms if you cure 1st reflection point issues. Electrostats usually have fewer side reflection point issues but that rear wall and placement can be a killer if you want the best sound they can produce.
Personally, I have gone thru very good dynamic's, to planars, to electrostats and back to high resolution dynamic's. In my 13x19 room my dynamic speakers just match the room's acoustics and set up possibilities much better than in my previous home where my Quad's ruled.
I would suggest that either could sound great if properly set up and driven in the right room. You have to evaluate your room's potential before you can make an intelligent choice.
a sealed enclosure is the best of both worlds.
An electrostat, direct-radiator dynamic, or horn system succeeds to the extent that it reproduces the illusion of a live performance.
Transparency varies more from speaker to speaker than from amp to amp or preamp to preamp.
Low coloration (including smooth and extended frequency response and freedom from resonances & diffraction) is crucial to good transparency.
In my opinion, much of the open and transparent presentation of a good electrostat is related to the radiation pattern. Electrostats have unusual radiation characteristics: Usually line source (emphasizes first-arrival over reverberant sound), usually relatively narrow pattern (minimizes early floor, ceiling, and sidewall reflections), and lots of relatively late-arriving energy to add richness and spaciousness (largely the result of the dipole pattern). In addition, several of the more successful manufacturers go to some effort to keep the radiation pattern reasonably uniform, which is beneficial to timbre because it preserves the spectral balance of the reverberant sound.
In my opinion a low-coloration horn system in an acoustically "live" room does many of the same things well that a good electrostat does. In my opinion it's a bit harder to get the same sort of presentation from a direct-radiator dynamic system. Direct radiator dynamics give you deeper bass and typically better imaging in a smaller package.
If you like the presentation of a good electrostat but for whatever reason neither electrostats or high-quality horns are practical for you, you might consider Maggies, Audio Artistry, Gradient Revolution (I sell these), Linkwitz Orion, and Eminent Technology. If you have the financial resources but not the space, you might consider the Acapella LaCompanella.
In your opinion, why is the sealed enclosure the best of both worlds? What would be a good example?
"Electrostat transparency from conventional speaker"
Yeah I agree the Electrostats are deficient to the Dynamics except the transparency part, you can see right through most electrostats...not to be confused with magneplanars. :)
Only reason people tolerate electrostatic speakers today is because they are dipoles, thus they are a functional 4 channel systems or primitive surround sound system (2 direct ch., 2 delay ch. (see audioK's post) Fact is without Quad's and Magneplanars, most panel type speakers aren't that good for the $$$'s charged. As a once proud Martin Logan (QuestZ, CLSz) owner I can only shake my head at what is available now for the $$$.
My solution to hard to position (Magneplanar), fragile (Apogee), over-priced (ML, Sound Lab) temperamental (Quad)electrostats was surround sound. I have the big dipole soundstage, endless detail (due to the three channel array) and full range sound (sub) without compromise. And a wonderful engaging warm sound to the music that is easy on the ears from a fatigue standpoint. Its proven that the addition of rear channels engages (ie emotional impact) the listener to a much higher degree than any other device will that doesn't amount to a gross quality difference in playback performance.
Yes, better than two channel!! hard to imagine but its true. My solution was born of frustration 12 years ago and I have never looked back to dipoles. I like having control of the delay so my Viola's don't grow to 6' tall :). A luxury of modern technology i've grown very accustomed too.
PS: the solution is not universal so don't think some primitive Proceed processor is going to do the job! Like any problem it helps to have the right tools to fix it and there is a right way and wrong way to do surround. Don't stray from the textbook.
You might want to consider Spicas. My local dealer said that the Angeluses came closer to the sound of Quads (which he also sold) than any other dynamic speaker. Of course, this was many years ago, and the state fo the art has certainly progressed.
I'd say your best chance at doing that would be to find a dynamic speaker that has nearly full range out of a single drive element. And one who's drive element has exceptionally low mass and also has a very strong magnetic drive motor.
There are some drive elements that are made primarily for low power SET systems that come close to this equation, although none will actually equal the electrostat for speed.
hales, dunlavy, duntech, allison, older AR are five examples, but certainly not the only ones. these brands and others sought a flat response from top to bottom. no exageration of the frequency range and since they are not ported, the roll off in the lowest frequencies is quite gradual. they are generally not as fussy about room placement too. transparency, flat response, tonal accuracy, and if the recording has it....real weight and dynamics...the spica 50 and the chapman t7 are two others. it is more popular, even at the highest end of audio to woo the listener with a combination of detail and staging. this makes for a great demo, but also makes for an unsatisfying pair of loudspeakers when you get beyond audiophile recordings.
The Chapman T-7's are uncanny, out Quading a Quad, if you can find a pair.
>Only reason people tolerate electrostatic speakers today is because they are dipoles, thus they are a functional 4 channel systems or primitive surround sound system (2 direct ch., 2 delay ch. (see audioK's post)
The physics do not agree with common sense. Although direct radiating speakers only have drivers on their front-side, sound waves in half the musical spectrum are large compared to domestically acceptable speakers so there is substantial off-axis radiation, even behind the speakers. Within the human vocal range, a mezzo produces foot-long waves at 1000 Hz and a barritone hits eleven feet at 100Hz.
The same wrap-arround occurs with the front and rear waves of dipoles. Since they are 180 degrees out of phase, they cancel when they wrap arround and meet. Dipole off-axis response is reduced by 20 log cosine alpha dB compared to the direct resonse. This means -3dB @ 45 degrees, -6dB @ 60 degrees, -12dB @ 75 degrees, etc. There is substantially less (1/3, -4.5dB) total power radiated for a given on-axis SPL compared to the ideal monopole which a conventional speaker approximates with decreasing frequency.
So dipoles generate less ambiance than conventional speakers and their reflections in the typical listening room are less deletrious. In my 13x19x8' room with the listener 11' off the front wall and speakers 4' off the front wall 8' apart measured from the tweeter dome apexes toed in to face the listeners, dipoles generate first reflections -6.5dB below the direct sound 4ms behind it off the ceiling and -11.2dB below 3.5ms behind off the side walls. In the range where the direct radiator doesn't have rear-ward output, the dipoles have a second reflection at -6.8dB below and 9ms behind. This is definately preferable to the direct radiators first reflections at only -3.5dB/4ms and -3dB/3.5ms.
The way to achieve electrostatic transparency with a dynamic driver is to skip the box. Dynamic dipole midrange like that found on the Linkwitz Orions is more similar than different to the planar speakers, although the sweet spot is much wider and placement less finicky.
"The physics (theory) do not agree with common sense"
But the measurements do, just measure 1m from the back of the speaker and 1m from the front of a Dipole and a Monopole then measure at the listening position. Compare them, then we'll be in agreement about How a Dipole really works in a room and what all that math you copied equates too. Please note the high frequencies are the exact frequencies that matter most in why I made my 4 ch. comments (Orions are only dipoles to 1440hz>24db/oct). Which is why Electrostatic Dipoles image overly large and are vastly different in their behaviour to the Orions. SL's experience with center channels is exactly why you don't want Dipoles for surround and why they make better 2 channel speakers than Monopoles.
Not all of us are on the SL train especially when it comes to surround sound! The Orions are great speakers but...
...I'd like to note CDwallaces post said "conventional box speaker", so my rec's are limited to the restriction placed by the original post.
have a good one