Differences between small vs. large mid driver

I can smell the can of worms that just opened in this thread : )

My personal thoughts are that 100 Hz is too low for a driver expected to cover the entire upper midrange region. I also agree with Trelja's comments that optimal woofer crossovers are quite low. What to do?

Well, if you use a "filler" driver aka a "upper bass /lower midrange" driver to fill in the gap, you've now got more dispersion, phase, impedance, etc.. characteristics to blend together. On top of that, you've just made your three way a four way. More cost and far more complex. As such, it is a step forward or backwards?

As far as larger drivers covering the range above 1.5 KHz, there are a LOT of variables here. The size of the voice coil, the contour and slope of the cone used, the type, size and shape of the dust cap, the type and size of the surround, the design of the motor structure ( magnet & pole piece ), etc... All of these things will alter frequency response, dispersion characteristics, transient response, etc...

While not the "perfect" driver, take a look at this Eminence Beta 12LT. The bandwidth that they get out of this driver is VERY impressive for its' size to say the least. I'm using these as midranges in PA cabinets as they easily cover that entire pass-band with admirable results. The cost is phenomenally reasonable for what you get too. Maybe not "hi-fi" quality, but it just goes to show what proper engineering can do. Sean
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The midrange driver range that I suggested (600 to 3000) is based on what I have seen done in three way speakers. I think that Nighthawk agreed with me, and provided all the details.

If you suggest that a woofer is good to 2500Hz, what's wrong with using it to 600 Hz?

I think the issues that Nighthawk and Sean raise are very cogent. Speaker design and building is a craft of tradeoffs. Do you push a driver a bit out of its optimal zone, or introduce an additional driver with the added complexity of dispersion characteristics and crossover? Pick your poison.

I used to be a stauch 3 way guy. Now, my tastes lean towards the two way, due to its inherent simplicity. Do believe anyone who tells you that it is night and day easier to build a good two way than a good three way ala the crossover. Of course, Bud Fried will tell you that the series crossover makes As Nighthawk pointed out, my Coincidents go down to about 40 something Hz, filled in by a subwoofer on the bottom for that last octave or so.

Eldartford, 600 Hz for a woofer has been fine for many in the history of audio. However, many do try to keep a crossover out of the midrange, and 600 Hz is a frequency that most people can hear loud and clear. My preference is to stay far away from that as a crossover point. The three way Frieds we'll be selling cross the 8" to the 6.5" at 200 Hz, and the 6.5" to the tweeter at 2700 Hz.

While I agree with the gist of the above, I beg to differ slightly. Since I listen to large orchestral music, I need authority, dynamics -- the ability to excite lots of air.
So, for the ~100->8-10kHz part I would use a wide-range 8-12" (supravox, lowther, goodmans, etc). The trade-off here is beaming...
For the upper range, a super tweat to over 25kHz. The trade-off here is the difficulty to align the acoustic centres of tweet & wide-range (at 8kHz the lambda is very small => the margin of error is high).
For the lower register:
At least one 15" per channel for bass (two for open baffle).
At least one 18/24" per channel for 20-45Hz. The trade off here is cost and cost (cost of drivers, cost of amplification).

Overall, such a construction ideally needs a minimum of three amp channels per side. Passive filter for crossing to tweet; Leave the wide-range free on top, cut it with a soft LPin the bottom. Active or PLL for the rest.

Wishfull thinking, eh?

I think your opinions are very good, Gregm. I also am particularly enchanted with the sound of the Lowthers, and should have mine mounted in a cabinets I am building within a month or so. The speakers that Audio Note Kondo Japan was running at HE2004 were very much as you described, and they sounded fabulous to my ears.

You may or may not know that Bud Fried was the original importer of Lowther (also true of Quad), and when I spoke to him recently about speaker projects I was working on for fun, I mentioned them. I expected him to tear them up, but he recalled an anecdote from long ago where a dear friend of his bought some very expensive AR speakers, and they both found out that they could just not do justice to the piano, which the Lowthers had always handled with aplomb.

Piano is PARTICULARLY important to Bud, as his wife Jane is a pianist. He still holds the Lowthers in extremely high regard. Believe me, if Bud doesn't rip something, it's a compliment. If he praises it, it's more than a tribute to how good a component actually is.