And why not? 
Ok, I know, some people will suggest they lack of "dynamic" (??? again a questionable term ???) and that they can oscillate because of the surround only suspension (no spider), or will invoke the breaking modes.
But, when I was using a Dynaudio D54 in complement of an Audax PR17TSM, or of a Supravox 215 RTF, it was always much better. And at these days, no EQ.
Actually I know people that use 2" open back compression drivers, so finally mid domes ( D54 is vented too) and they don't complain of a lack of clarity or "dynamic"..
Here a study of the ATC (featuring a double suspension).
Ok, I know, some people will suggest they lack of "dynamic" (??? again a questionable term ???) and that they can oscillate because of the surround only suspension (no spider), or will invoke the breaking modes.
But, when I was using a Dynaudio D54 in complement of an Audax PR17TSM, or of a Supravox 215 RTF, it was always much better. And at these days, no EQ.
Actually I know people that use 2" open back compression drivers, so finally mid domes ( D54 is vented too) and they don't complain of a lack of clarity or "dynamic".
.Here a study of the ATC (featuring a double suspension).
They don't go low enough. You gain maybe an octave over a tweeter with good extension, but that doesn't get you low enough to use a really bass capable woofer without running into beaming and breakup on its high end. There's no shortage of good and inexpensive tweeters that work well down to 2000 Hz., and that makes it really tempting to want the midrange to go down to 200-300 . . . easy to do with small cones, not with "midrange' domes. So for a three-way big cone/small cone/dome just seems to make more sense than medium cone/dome/dome . . . especially since there are so many good small cone midrange drivers around.
That would be my guess, anyway . . . when I think three-ways putting a crossover at 700 Hz. just doesn't make a lot of sense . . .
That would be my guess, anyway . . . when I think three-ways putting a crossover at 700 Hz. just doesn't make a lot of sense . . .
ATC 3" and Dyaudio D54 are top notch in this group.
For manufacturers, cost is almost always the 1st consideration. A good dome midrange can deliver good performance, but might be somewhat lacking in cost-effectiveness. It's more so when the operation bandwidth is taken into account when discussing 'performance'.
Just my 2c
For manufacturers, cost is almost always the 1st consideration. A good dome midrange can deliver good performance, but might be somewhat lacking in cost-effectiveness. It's more so when the operation bandwidth is taken into account when discussing 'performance'.
Just my 2c
I'm still an very much an amateur at all this, and see how for the optimum 3-way system a driver handling pretty much the entire midrange (300-ish to around 4,000Hz) would be desirable. But how about if the speaker you were building needed to be more affordable or for its intended application it simply didn't need to be an "optimum" design?
A xover that low (300Hz) requires some rather pricey inductors and caps, so a xover point up around 700Hz would allow the price to drop way down for the mid's xover and you wouldn't have to use such a heavily-built tweeter to handle a relatively low crossover point, again, very probably saving some $$ and possibly gaining better performance at the higher frequencies it handles.*
I never considered this aspect.....well actually, this is the first I've heard of it!
I have wondered why dome mids cost so much vs. a similar-performance cone driver, though a dome's magnet structure is probably partly the cause of that, which almost always is rather large for some reason.
I always believed a dome mid's superior(?) dispersion would be an advantage over a cone driver, but maybe not enough of one to offset their increased cost.......
* this is ancient in the loudspeaker world I guess, but Infinity used a 3" polypropylene dome x'ed over at 500Hz back in 1992 in their Kappa 7.2i and (really ancient!) 550Hz for the 2" driver in the L710 by ADS (scroll down a bit past halfway) back in '80. So if they had the technology back then to build dome mids that could handle such relatively low frequencies, surely they could do so now
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I love the ATC, but the cost is a killer, and the high-ish crossover point does limit your choice of woofer. I was looking for a mid yesterday to go with some modded 15"s, and though there are some nice looking drivers out there, none would go nearly low enough to work well in my application. Shame.
Since the ear is still quite sensitive at 4kHz, it is good if you can push the XO even higher than that if your goal is semlessness. With the growing number of (from affordable to lots) drivers that can go 200-300 up to 20+ k, you can simplify further and just eliminate the tweeter.
Once you get that low (or lower) you really have to consider active. That said, 300 Hz happens to be in the area where a wide range mid (mid/tweetr) is and the woofr can be choosen with good behabior here, and wavelengths are long (meaning you can effectively mount the drivers co0incidently, so a 1st ordr XO can often be gotten away with. Series works particularily well.
I'm working on a 2-way right now with XO ~300 Hz. Need to fire up the measure system to further tweak, but 3mH + 30 uF sems to be pretty close (series, 4 ohm bass, 8 ohm midtweeter). I didn't find those bits overly expensive
And on the subject matter -- domes -- mids or tweeters -- that work decently get scary expensive.
dave
Bingo. On the low end, throw versus diameter, on the high end, directivity versus diameter.
My old Dynaudio 4-ways used a D54 to "fill" between the 12" woofer and 1" tweeter. The D54 was a marvelous driver- for about 1.5 octaves! I still have some D75s in my collection- these extended the range to 2 octaves, but at the high end had similar directivity issues as conventional drivers with similar diameters. Might as well use a cone, where the low end can be extended. The little SEAS cones in my current speakers are far cheaper and far better.
I've heard at least one very good design with a midrange dome. The Gershman Sonogram. A beautiful sounding tower 3-way. Vocals are very, very good.
But agree that the midrange domes seem to present to many design challenges to be popular.
But agree that the midrange domes seem to present to many design challenges to be popular.
In my ciare design I wanted the HM500 to cross a low as possible and wandered were the limits where.
My ciare design.http://www.diyaudio.com/forums/multi-way/183727-ciare-design-idea.html
pdf mh500
http://www.ciare.com/pdf/catalogo/HM500.PDF
With the sensitivety of our ears and with Winisd I could find out where the limits where and it isn't that bad because the extrusion is limited above 500Hz.
Because our ears are sensitive to frequencies above 300Hz the mid range will get about 2-12W when the woofers get 200W. For us to experience the same sound level
Note in my design I have made attentuation down to 87dB at 1W for the HM500. Now the midrange will reach xmax at 74Watt.
My ciare design.http://www.diyaudio.com/forums/multi-way/183727-ciare-design-idea.html
pdf mh500
http://www.ciare.com/pdf/catalogo/HM500.PDF
With the sensitivety of our ears and with Winisd I could find out where the limits where and it isn't that bad because the extrusion is limited above 500Hz.
Because our ears are sensitive to frequencies above 300Hz the mid range will get about 2-12W when the woofers get 200W. For us to experience the same sound level
Note in my design I have made attentuation down to 87dB at 1W for the HM500. Now the midrange will reach xmax at 74Watt.
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Why isn't the dome shape very strong and good for dispersion and hasn't it a good self damping behavior. Compared to a cone driver?
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