as far as 3 inch dome midrange getting an fs less than 300Hz is tough for that you need a dome which is about 4 inch which works the range of 200hz to 2k but then it doesnt cover the maximum vocal spectrum.. 200hz needs more excursion as well not that easy with domes..
if you release a dome.. one thing you have to keep in mind is center to center spacing with the high freq driver... you need a very very small C to C spacing to super tweeter so you should design it accordingly
You should make a perfect three dome with very very small c to c spacing that would cover from 300 to 20khz with perfect wide dispersion
something like from 300 to 6500 on a 3" and 6500 to 13khz on 1" and 13khz to 40khz on piezo or something
or a 2 dome version covering from 700-800 ..
the two dome need to be perfectly matched in terms of dispersion, sensitivity and power handling.. (95db flat would be my goal)
also dont forget to produce some kind of flange to protect the dome or grill (that doennt affect SQ)
You should make a perfect three dome with very very small c to c spacing that would cover from 300 to 20khz with perfect wide dispersion
something like from 300 to 6500 on a 3" and 6500 to 13khz on 1" and 13khz to 40khz on piezo or something
or a 2 dome version covering from 700-800 ..
the two dome need to be perfectly matched in terms of dispersion, sensitivity and power handling.. (95db flat would be my goal)
also dont forget to produce some kind of flange to protect the dome or grill (that doennt affect SQ)
The toughest part in the dome mid design especially is that we need to have opening behind the dome and yet maintain the sensitivity and flux density. Its happening well but will take more time than what we have expected.
...and one suspects the results will remain so for some time to come!
I have recently responded to a number of questions concerning 3" domes and in particular ATC's versions of it in a recent thread that was started under the title "ATC SCM200 ASL Pro": Interested readers might also like to refer to that discussion. My response here is to detail some of the few possible improvements that might be considered to the deservedly well-renowned ATC midrange driver and some of its "copies".
Firstly it should be recognised that a substantial part of the success of ATC's 3" dome is attributable to the means by which it is manufactured - an aspect of real audio engineering that is seldom mentioned in this forum and which the normally-quoted design parameters do not convey. The reputation of the ATC driver in terms of not only its sound quality but also of its consistency and reliability in the field will likely remain only an aspiration to other drive unit manufacturers. There is a gulf that exists between more delicate "hi-fi" drivers and those that work at consistently high power outputs for many years.
Secondly in terms of the audio aspects of the design it is important to understand the engineering compromise that a 3" dome represents. The dome offers impressive structural integrity and rigidity with a maximally-sized (diameter) voice coil - and therefore maximal power handling capacity. The diaphragm diameter separately affords covering the important part* of a conventionally-defined mid-band. Contrary to common belief, the dome offers no advantage in terms of directivity - it is meant to be pistonic over its operating band. Nevertheless the 3" dome offers a very nice compromise overall - if it is implemented well.
*By important, I refer here to accommodating frequencies up to 4kHz-ish and low enough to nominally include the female vocal range. Low frequency extension to also cover the nominal full male vocal range would be nice but (as will be outlined later in this response) likely includes extra compromise. And it remains easier to accommodate extra drivers at the low frequency end (woofers or further arrayed mid-band drivers) than it is to accommodate something such as a 4" dome and a driver to cover from 2.5kHz-ish up to a tweeter.
Given the real-world demands of competent manufacturing and acoustic performance, there are however some modifications that might spring to mind - and are hopefully pertinent to this thread. Here I will detail some of my experiments that will also reveal some of the engineering that I believe lies behind ATC's 3" dome. Before continuing, we also need to keep in mind that ATC's own loudspeakers use the SL version of the driver that is not available to other manufacturers or to the public. Nonetheless in no particular order of merit:
1. FREQUENCY RESPONSE
As outlined above, the frequency response is limited by a compromise between low frequencies (maximising displacement volume) and high frequencies (minimising radiating area). There is little to be achieved here.
2. TRANSIENT RESPONSE
Since the drive unit exhibits minimum phase throughout its intended passband, there is nothing to be gained here.
3. FREQUENCY LINEARITY
(a) There is some benefit (at least in terms of peaks and dips in the magnitude response) from additionally coating the rear of the diaphragm in the damping material ("opanol") - but at the expense of reducing efficiency slightly.
(b) Audibly better than (a) in my experiments is to avoid using the black dye in the raw diaphragms. This obviously requires "scratch" building but produces a dome the colour of which will only be truly understood by those changing babies. (Presumably here ATC and other manufacturers have not chosen to pursue sound quality at all costs). I suspect the improvement obtained is not due to the absence of the dye per se, but rather the ability of the untreated diaphragm to better absorb the damping material.
(c) Adding absorbent in the enclosed rear diaphragm chamber has surprisingly little (no) audible benefit. I believe early ATC drivers might even include some such material?
(d) Machining an inverted horn-like rear chamber presents a compromise in the motor design structure. Since (c) above produces no benefit, we can probably safely assume that a small enclosed rear chamber is the best compromise.
(e) The wave-guide/horn also offers surprisingly little. A design that means being able to mount the driver on the front of a baffle is a welcome advantage, however.
(f) A nomex collar offers no audible advantage over a small balsa wood collar.
(g) A dimple as mentioned in this thread would appear only to offer some out-of-band performance gain - certainly the fundamental break-up mode requires attention in any crossover design. It is not known what the dimple would offer quantitatively but arranging the diaphragm press tools to produce corrugations in the dome as the material is drawn in can add significant stiffness to the structure too. Once again this is probably not a DIY fix, however.
4. SUSPENSION LINEARITY
I state outright that the double suspension in the ATC design is not only optimal but necessary for any design with pretensions to outperform this driver. Preventing rocking modes and allowing such a tightly defined coil geometry is an outstanding feat. As hinted earlier, years of reliability are testament to this feat aside from the highly renowned sound quality it offers.
I also state that increasing distortion at lower frequencies is an inevitable compromise of any suspension. Once again the important word here is compromise. In its intended frequency range the ATCs (low) suspension-related distortion represents the best compromise. As hinted above, for those seeking better or increased low frequency capabilities, arrays of 3" domes have proven to be very effective if a bit expensive.
Also of note here is that the double suspension provides an enclosed volume that is vented. This additionally lowers distortion slightly and contributes to overall driver damping; Its venting decreases the fundamental driver resonance by a factor of about two.
5. MOTOR (DISPLACEMENT-DEPENDENT) LINEARITY
(a) Increasing displacement is something of a non-starter since the inevitable compromises hinted at previously have the undesired effect of making the driver not work at all.
(b) In (a) we are restricting our account to short coils/long gaps whereas the Volt implementation uses a long coil/short gap intended (presumably) for increased low frequency output and higher efficiency. The latter might be achievable (?) but at the expense of increasing distortion compared to a short coil motor.
(c) The ATC coil (according to the manufacturer's specifications) partially exits the gap in its top 6dB of SPL output. We could thus consider extending the gap height to accommodate a larger proportion of its displacement. Whether such a change will offer any audible improvement is debatable since it will only be used in short-term peak outputs. We also note that the gap is magnetically saturated with angled pole pieces: Accommodating a longer gap is then not so easy or without compromise.
6. MOTOR (CURRENT-DEPENDENT) LINEARITY
(a) Neodynium magnets indeed offer better distortion than the ceramic magnets in the ATC drive unit and its "copies". The result is audible although not the dominant factor in this section. However the large amount of steel necessary to accommodate a ceramic magnet also affords a significant heat sinking capability. Here then is a real-world compromise - one that would be foolhardy to ignore - and an issue that can be circumvented to a large extent by other means.
(b) Adding copper in the coil gap will reduce third harmonic distortion as eddy currents are reduced in the magnetically non-linear steel pole pieces. This approach reduces field intensity and therefore sensitivity. It also reduces inductance that will improve sensitivity at higher frequencies. However, it will also reduce the heat sinking capabilities of the motor structure above ATC's own solution...
(c) ATC adopt non-conducting polymer pole pieces to reduce the currents circulating in the remaining steel structure. This increases inductance, reducing efficiency further at higher frequencies but offers greater heat sinking capabilities. As mentioned above, this drive unit is not available to other manufacturers and DIY builders, however.
(d) The 3" drivers of which I am aware use Kapton formers. The only thing relevant here is to avoid conductive aluminium foil formers.
CONCLUSIONS FROM MY EXPERIMENTS
(i) Don't try and fix what is not broken. Engineering expertise is sometimes well hidden from simple design parameters and restricted measurements.
(ii) Adopt current drive. For DIY builders this will circumvent the motor current-dependent third order non-linearites and offers a noticeable improvement in sound quality. It also offers a complete absence of thermal compression effects that are often wrongly ignored** as well as imparting other advantages that are best left to another thread.
(iii) If you want to take one apart, try additionally coating the diaphragm rear - opanol is just a 50:50 mix of water and ethanol I think (?). But remember it will also lower sensitivity too. If you want to re-build one you might also like to try it without the black dye. However, I absolutely refuse to take any responsibility for anyone that does take one apart!
(iv) If you are short of SPL capability, try adding more complete speakers as this will add further advantages too. If that cannot be done, try an array of domes such as three in a vertical line with the outer two curtailed to the lower octaves or so.
(v) If (iv) is too expensive then spend time getting the bass section better. An undersized enclosure free of in-band resonances combined with (sub) bass drivers can work wonders here.
** Here I refer not to the audibility of thermal compression in a single driver but the overall magnitude responses changes that can occur due to the heating (and cooling) of the different drivers in a multi-band system.
I am absolutely sure there are a lot more gems in this thread to discuss that this hastily typed response has overlooked. But hopefully this is enough to be going on with for now...
I have recently responded to a number of questions concerning 3" domes and in particular ATC's versions of it in a recent thread that was started under the title "ATC SCM200 ASL Pro": Interested readers might also like to refer to that discussion. My response here is to detail some of the few possible improvements that might be considered to the deservedly well-renowned ATC midrange driver and some of its "copies".
Firstly it should be recognised that a substantial part of the success of ATC's 3" dome is attributable to the means by which it is manufactured - an aspect of real audio engineering that is seldom mentioned in this forum and which the normally-quoted design parameters do not convey. The reputation of the ATC driver in terms of not only its sound quality but also of its consistency and reliability in the field will likely remain only an aspiration to other drive unit manufacturers. There is a gulf that exists between more delicate "hi-fi" drivers and those that work at consistently high power outputs for many years.
Secondly in terms of the audio aspects of the design it is important to understand the engineering compromise that a 3" dome represents. The dome offers impressive structural integrity and rigidity with a maximally-sized (diameter) voice coil - and therefore maximal power handling capacity. The diaphragm diameter separately affords covering the important part* of a conventionally-defined mid-band. Contrary to common belief, the dome offers no advantage in terms of directivity - it is meant to be pistonic over its operating band. Nevertheless the 3" dome offers a very nice compromise overall - if it is implemented well.
*By important, I refer here to accommodating frequencies up to 4kHz-ish and low enough to nominally include the female vocal range. Low frequency extension to also cover the nominal full male vocal range would be nice but (as will be outlined later in this response) likely includes extra compromise. And it remains easier to accommodate extra drivers at the low frequency end (woofers or further arrayed mid-band drivers) than it is to accommodate something such as a 4" dome and a driver to cover from 2.5kHz-ish up to a tweeter.
Given the real-world demands of competent manufacturing and acoustic performance, there are however some modifications that might spring to mind - and are hopefully pertinent to this thread. Here I will detail some of my experiments that will also reveal some of the engineering that I believe lies behind ATC's 3" dome. Before continuing, we also need to keep in mind that ATC's own loudspeakers use the SL version of the driver that is not available to other manufacturers or to the public. Nonetheless in no particular order of merit:
1. FREQUENCY RESPONSE
As outlined above, the frequency response is limited by a compromise between low frequencies (maximising displacement volume) and high frequencies (minimising radiating area). There is little to be achieved here.
2. TRANSIENT RESPONSE
Since the drive unit exhibits minimum phase throughout its intended passband, there is nothing to be gained here.
3. FREQUENCY LINEARITY
(a) There is some benefit (at least in terms of peaks and dips in the magnitude response) from additionally coating the rear of the diaphragm in the damping material ("opanol") - but at the expense of reducing efficiency slightly.
(b) Audibly better than (a) in my experiments is to avoid using the black dye in the raw diaphragms. This obviously requires "scratch" building but produces a dome the colour of which will only be truly understood by those changing babies. (Presumably here ATC and other manufacturers have not chosen to pursue sound quality at all costs). I suspect the improvement obtained is not due to the absence of the dye per se, but rather the ability of the untreated diaphragm to better absorb the damping material.
(c) Adding absorbent in the enclosed rear diaphragm chamber has surprisingly little (no) audible benefit. I believe early ATC drivers might even include some such material?
(d) Machining an inverted horn-like rear chamber presents a compromise in the motor design structure. Since (c) above produces no benefit, we can probably safely assume that a small enclosed rear chamber is the best compromise.
(e) The wave-guide/horn also offers surprisingly little. A design that means being able to mount the driver on the front of a baffle is a welcome advantage, however.
(f) A nomex collar offers no audible advantage over a small balsa wood collar.
(g) A dimple as mentioned in this thread would appear only to offer some out-of-band performance gain - certainly the fundamental break-up mode requires attention in any crossover design. It is not known what the dimple would offer quantitatively but arranging the diaphragm press tools to produce corrugations in the dome as the material is drawn in can add significant stiffness to the structure too. Once again this is probably not a DIY fix, however.
4. SUSPENSION LINEARITY
I state outright that the double suspension in the ATC design is not only optimal but necessary for any design with pretensions to outperform this driver. Preventing rocking modes and allowing such a tightly defined coil geometry is an outstanding feat. As hinted earlier, years of reliability are testament to this feat aside from the highly renowned sound quality it offers.
I also state that increasing distortion at lower frequencies is an inevitable compromise of any suspension. Once again the important word here is compromise. In its intended frequency range the ATCs (low) suspension-related distortion represents the best compromise. As hinted above, for those seeking better or increased low frequency capabilities, arrays of 3" domes have proven to be very effective if a bit expensive.
Also of note here is that the double suspension provides an enclosed volume that is vented. This additionally lowers distortion slightly and contributes to overall driver damping; Its venting decreases the fundamental driver resonance by a factor of about two.
5. MOTOR (DISPLACEMENT-DEPENDENT) LINEARITY
(a) Increasing displacement is something of a non-starter since the inevitable compromises hinted at previously have the undesired effect of making the driver not work at all.
(b) In (a) we are restricting our account to short coils/long gaps whereas the Volt implementation uses a long coil/short gap intended (presumably) for increased low frequency output and higher efficiency. The latter might be achievable (?) but at the expense of increasing distortion compared to a short coil motor.
(c) The ATC coil (according to the manufacturer's specifications) partially exits the gap in its top 6dB of SPL output. We could thus consider extending the gap height to accommodate a larger proportion of its displacement. Whether such a change will offer any audible improvement is debatable since it will only be used in short-term peak outputs. We also note that the gap is magnetically saturated with angled pole pieces: Accommodating a longer gap is then not so easy or without compromise.
6. MOTOR (CURRENT-DEPENDENT) LINEARITY
(a) Neodynium magnets indeed offer better distortion than the ceramic magnets in the ATC drive unit and its "copies". The result is audible although not the dominant factor in this section. However the large amount of steel necessary to accommodate a ceramic magnet also affords a significant heat sinking capability. Here then is a real-world compromise - one that would be foolhardy to ignore - and an issue that can be circumvented to a large extent by other means.
(b) Adding copper in the coil gap will reduce third harmonic distortion as eddy currents are reduced in the magnetically non-linear steel pole pieces. This approach reduces field intensity and therefore sensitivity. It also reduces inductance that will improve sensitivity at higher frequencies. However, it will also reduce the heat sinking capabilities of the motor structure above ATC's own solution...
(c) ATC adopt non-conducting polymer pole pieces to reduce the currents circulating in the remaining steel structure. This increases inductance, reducing efficiency further at higher frequencies but offers greater heat sinking capabilities. As mentioned above, this drive unit is not available to other manufacturers and DIY builders, however.
(d) The 3" drivers of which I am aware use Kapton formers. The only thing relevant here is to avoid conductive aluminium foil formers.
CONCLUSIONS FROM MY EXPERIMENTS
(i) Don't try and fix what is not broken. Engineering expertise is sometimes well hidden from simple design parameters and restricted measurements.
(ii) Adopt current drive. For DIY builders this will circumvent the motor current-dependent third order non-linearites and offers a noticeable improvement in sound quality. It also offers a complete absence of thermal compression effects that are often wrongly ignored** as well as imparting other advantages that are best left to another thread.
(iii) If you want to take one apart, try additionally coating the diaphragm rear - opanol is just a 50:50 mix of water and ethanol I think (?). But remember it will also lower sensitivity too. If you want to re-build one you might also like to try it without the black dye. However, I absolutely refuse to take any responsibility for anyone that does take one apart!
(iv) If you are short of SPL capability, try adding more complete speakers as this will add further advantages too. If that cannot be done, try an array of domes such as three in a vertical line with the outer two curtailed to the lower octaves or so.
(v) If (iv) is too expensive then spend time getting the bass section better. An undersized enclosure free of in-band resonances combined with (sub) bass drivers can work wonders here.
** Here I refer not to the audibility of thermal compression in a single driver but the overall magnitude responses changes that can occur due to the heating (and cooling) of the different drivers in a multi-band system.
I am absolutely sure there are a lot more gems in this thread to discuss that this hastily typed response has overlooked. But hopefully this is enough to be going on with for now...
Does anyone see the three domed speaker made by ECdesigns ?
If you want a lower XO, even lesser distorsion : simply add more dome midranges ? (polar map ?)
https://www.ecdesigns.nl/finesse.html
If you want a lower XO, even lesser distorsion : simply add more dome midranges ? (polar map ?)
https://www.ecdesigns.nl/finesse.html
https://www.thomann.de/fr/neumann_k...3e918034ea_2&gclid=CNGi2f3K8c8CFcGfGwodELwHCQ
What do they use as dome midrange ??? This is a very reliable studio monitor brand ! (unfornatully too flat curve according to me for home integration without EQ)
What do they use as dome midrange ??? This is a very reliable studio monitor brand ! (unfornatully too flat curve according to me for home integration without EQ)
If this is directed at my comments (?) then please note I see this approach as a further compromise which is not normally necessary. "Simply" ignores too the crossover design required in order to address the polar issues. I have however constructed large line arrays with 3" domes that measure like a text book example - although I believe a single 3" dome will prove more than sufficient for most domestic applications.
Company documents say it's a new, custom design dome driver. Neumann don't do their own drivers (afaik) so I would hazard a guess: scandinavian OEM unit made/modified to their specs, and they will made have sure it's going to be available for years since long service life is a key issue for Neumann and their customers.
