Midrange: Dome or Cone? - diyAudio
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Old 16th April 2003, 10:34 AM   #1
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Question Midrange: Dome or Cone?

Hi

Any opinions (and I'm sure there are) on the relative merits of domes v cones for midrange?

I'd really like to know if any here have used the Dayton or Vifa domes from Parts Express.

Thanks in advance.

Mos
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Old 16th April 2003, 04:15 PM   #2
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I have never used dome midrange but I think it as a better dispersion over cone.
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Old 16th April 2003, 05:38 PM   #3
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I've just finished building a set of speakers using the cheaper dayton dome mid and tweeter and I must say that they sound good.
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Old 16th April 2003, 09:32 PM   #4
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I use a Vifa 3" fabric dome and I'm really happy with it, but I discovered in the course of building my 3-ways and doing a lot of reading, that this is really dependant on; i) where (frequency) and how (crossover type, slope, etc) you put the low and high points for the bandpass crossover,
ii) the specs and capabilities of the other drivers.

I guess the ideal situation is for the drivers to share as much each of the frequency spectrum as possible, BUT a very important consideration for the crossover between the woofers and the mids is to avoid as much as possible crossing in really ear sensitive human vocal regions. (somewhere in the 500 to 1000Hz area). Unfortunately due to the typical capabilities and specs of most midrange drivers, this is exactly where manufacturers recommend that you cross them over!

I think that to get any advantage in using a mid at all, you need one that will be able to perform well over frequencies where you will probably be most likely to notice problems, so you do need to choose really carefully and integrate it with other drivers as smoothly as you can.

One way to do this is to use a good small cone because they are typically resonant much lower than domes and therefore you can often cross them around 300-400, but they can be less nice in the upper mid region, so if you choose to do this ideally you'd not want to cross to the tweeter too high.

The way I got around it with my domes was to use a nice steep (4th order linkwitz riley) crossover between the woofers and mids at about 500. I did use an active crossover though because higher order passive crossovers this low can be really problematic. A side note her: bi-amping this way was easily the single most noticable and satisfying improvement I have ever made!

I tried them at 4000 to the tweeter but they seemed to "ring" way too much so I backed it down to 3200 and now they are sweet. Used a passive 4th order linkwitz riley - complicated but worth it.

I guess if I was going to do it again I'd go for a high quality small diameter (maybe 4") cone crossed at about 300Hz to the woofers, but I got my domes for an excellent price given their capabilities.

As far as the comment made by François about dispersion goes, this again depends on the passband, but I'd guess domes may offer better dispersion over the higher frequencies.

I don't know what domes are listed in parts express but mine are Vifa D75MX-31-08's, 3" coated fabric dome.
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Old 17th April 2003, 05:31 PM   #5
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My impression is that shape of a driver has little to do with dispersion (except where the shape helps decouple part of the cone or dome, so that the smaller part acts like a smaller driver for higher frequencies --common in woofers). Cones and domes are usual shapes because their geometry makes them stiffer than a flat surface of equal mass.
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Old 17th April 2003, 05:36 PM   #6
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Oops -- sent reply off before finishing it: dispersion is determined by size of driver relative to wavelength of frequency produced. If the driver is small compared to the wavelength, it will be relatively omnidirectional, but as wavelength gets shorter, dispersion gets more and more restricted. The difference in dispersion patterns in the transition from a large woofer to a smaller midrange is part of the difficulty invovled in speaker design, since what is heard, even in the sweet spot, is not just sound directly radiated, but involves how the whole room is energised.
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Old 17th April 2003, 10:39 PM   #7
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"what is heard, even in the sweet spot, is not just sound directly radiated, but involves how the whole room is energised."

Yes. You are right. Totally.

Regards, Pierre Lacombe.
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Old 19th April 2003, 01:40 AM   #8
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Default Cone V Dome

I have used both over the years.

I find that the cavity that is associated with the shape of the cone has an effect on the sound. I guess it might be a kind of horn effect? So I have noticed variations in the sound of midranges based on the depth of the cone, and the size of the center dome, or lack there of in the case of the phase plug design.

Domes have no cavity, so they don't have the cavity sound. However there is a second devil in the details. Midranges also suffer from the rear wave being reflected off of the magnet and coming back through the cone/dome. Most dome midranges suffer from this reflection worse than their cones. If you disassemble the dome, you usually find the flat metalic face of the magnet structure directly behind the entire dome. Better designed dome tweeters now have a hole bored into the magnet to let the back wave escape ( B&W nautilus, JBL studio ). I don't know if there is a dome midrange of this design out there. I would guess that a soft dome would be more succeptable to passing this reflection, but I don't know if hard dome midranges are (metal) a lot better.

I think my favorite cone is made by Vanderstein. It has a miniscule magnet structure ( made possible by rare earth magnets) - to avoid reflections. I don't know if you can buy the driver separately.

There are also cone midranges that have the cone filled in (Phase Technology) So these would avoid the cavity sound and the thick cone would probably not pass the reflected sound off the magnet.

There ya go, way too much information.
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Old 19th April 2003, 04:05 PM   #9
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Thumbs up dome...

my speakers has the atc 3" middome.....to me there is nothing better...!

to dome or to cone - that is the Q...
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Old 21st April 2003, 02:32 PM   #10
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I agree with comments about sounding different, and about the problem of backwave reflection in both cones and domes, but the specific issue I was addressing was dispersion, not overall sound quality.

Quite a few domes have some sort of foam or damping material over the pole piece of the magnet in the hope that this will help minimise backwave. Venting the pole piece helps also, but the vents don't seem wide enought to actually completely stop reflections. Some also have the pole piece bevelled -- this ought to help.
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