Size of Midrange Drivers

08-25-14: Psag
TAD concentrics use a 6.5" midrange.

Point?
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Johnnyb53 --

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Finally, the name of the game isn't just radiating area; it's air displacement. A 4.5" driver has a radiating surface of 15 sq. inches. My Mag 1.7s have a radiating surface of 456 sq. inches. Yet, a premium 4.5" midrange might have a maximum excursion of .2", which amounts to around 3 cu. in. of displacement. My big panel, if its excursion is .01" (I'm guessing here, but it's probably in the ballpark), displaces about 5 cu. in. of air even though it's spread over a wider area. So two of those 4.5" midranges would displace about the same amount of air at full excursion.

This is an interesting aspect. My impressions is that it's not without audible importance how a given amount of air is moved; either "gently" via a larger area, or "forcibly" through a smaller ditto. My preference - if it is indeed explained fundamentally through this aspect - is for the former, and this goes for the whole frequency spectrum.

Moreover, the number of point sources (convering the same frequency span) is also a factor. With regards to bass (and the rest of the sprectrum), generally, I'd rather have one unit covering what two or more units equaling the same radiation are can muster.

Phusis
My impressions is that it's not without audible importance how a given amount of air is moved; either "gently" via a larger area, or "forcibly" through a smaller ditto. My preference - if it is indeed explained fundamentally through this aspect - is for the former, and this goes for the whole frequency spectrum.

And I agree with you. The larger the radiating surface, the smaller the excursion required to achieve the same SPL. A 5" midrange has about 19.5 sq. in. of radiating surface; The Magnepan 1.7 has 456, or 23 times as much. The Magnepan's microscopic excursion has a profound effect on inertial artifacts--the mechanics of acceleration, stopping, ringing, and reversing. It results in a relaxed, natural presentation.

Note the expensive and herculean efforts to reduce this in a pistonic driver: the TAD coincident drivers are made of vapor deposited beryllium--brittle, fragile, but incredibly light to minimize inertial effects.

Moreover, the number of point sources (convering the same frequency span) is also a factor. With regards to bass (and the rest of the sprectrum), generally, I'd rather have one unit covering what two or more units equaling the same radiation are can muster.

I agree here, too The miraculous thing about the Maggie 1.7 is that it speaks in such a single, coherent voice for just $2K/pair. The TADs also do it with a 6.5" coincident driver that covers 8 octaves. Its point source would have an imaging advantage over the Maggies' line source, and the upper models have more bass reach, but at a significant price difference.

Bombaywalla --

I have a fair bit of world-wide listening experience & have listened to a lot of speakers (& a lot of electronics) yet to but yet to have a positive experience of a 12" midrange playing midrange. If you look at my systems I do own a Tannoy DMT10Mk2 which has a 10" playing midrange all the way up to 1.4KHz. It sounds good for the most part & is just fine for the use that I've put it to but when I had a time-coherent speaker with a 4.5-5" Eton midrange, the Tannoy was nowhere near that quality.

Having not heard the Tannoy model you own I still believe what you hear could be categorized under 'preference' with regard to certain aspects of sound. Take 6moons review of the Austrain WLM Diva Monitor speakers (for a hopeful illumination):

(excerpts)

10-inch paper cones with hard cloth surrounds simply sound different than 5-inch Beryllium or ceramic cones that are hung off loose butyl rubber. The former are more natural, relaxed and full to my ears. In turn, they're not as overtly 'resolved'. The sharpness and leanness often associated with accuracy is missing.

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It's a speaker that will tweak certain people because it lacks what they consider prerequisites for a hi-end worthy design - narrow baffles, small midrange drivers, exotic diaphragms, famous tweeters. WLM gets by with apparently lesser ingredients. Still and to my ears, the end result is a more inviting, tastier dish. What that really says about current high-end hifi sensibilities you may ponder yourself in some spare time.

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As our own Jeff Day reminds us, there's a music lover's perspective which deviates from the studio monitor credo of 'warts'n'all'. Music lovers first and foremost insist on an emotional connection with the music. Secondly, they insist -- very sensibly if you ask me -- that all of their music and not just a very narrow selection thereof be enjoyable. The Diva Monitor conforms perfectly to this omnivorous demand. It's a tone monster. That makes it a fabulous addition to the retro/vintage sector of loudspeaker design where large paper cones with pleated cloth surrounds remain en vogue. Those counter the over-articulated 'starving super model' ideal that's pursued to excess elsewhere. It returns us to the earthy curves of a Sophia Loren, the power and brio of Classic Rock and the soulful tone of a Mesa Boogie.

http://www.6moons.com/audioreviews/wlm/divamonitor_4.html

Time coherency of definately an important factor in sound reproduction, but it's a singular aspect attainable in many forms with many variables. The WLM Diva's are one way to get there, and going by the floorstander version of the Diva's it's a sonic imprinting I enjoyed immensely. In other incarnations though, despite being time coherent speakers, it could be an entirely different matter - to my ears at least.

Phusis,
thanks for the info & the excerpts from the 6mooons.com review. If nothing else, the speaker finish is very nice to look at.
In a similar view both in respect to "Made in Austria" & beautiful looking finishes - at RMAF 2013 I heard a very nice sounding stand mount speaker by Brodmann Acoustics called the FS from their Festival Series. In that hotel room it did much better than its floor-standing bigger brother which they were playing on Sunday morning. Some links to that speaker:
http://brodmannacoustics.com/index.php?id=116

http://www.stereophile.com/content/brodmann-acoustics-festival-series

Maybe I liked it 'coz it has a 5" midrange?? LOL!! :-)
here's a nice write-up on that speaker:
http://hans-deutsch-akustikforschung.com/pics/tests/avmentor.pdf
Look at its step response - exactly what a time-coherent step response should look like (note that it uses a 6dB/octave slope).