Midrange dome drivers banned ?

[hardisj]

Simulations with VituixCAD seem to show that the closest spacing may not provide the best overall power response.

interesting.

 

[tuga]

Vivid Audio also uses midrange domes in some of their speakers:

 

[gene_stl]

I wonder why Troels Gravesen thinks he can design a better crossover than the engineers at Yamaha??
Oh yeah he sells them for 900 Euros the pair.

 

[PKAudio]

1. Yamaha or any other brand is no guarantee of well designed crossover, especially if that crossover was designed ~20-30 years ago.
2. Everybody wants to get paid for his work. Troels does not sell it. Jantzen does. Nowadays we could complain that everything is expensive, but do we really want? I mean, we either accept it and buy, or just leave it...but do not have to complaint about prices all the time. Anyone has a change to redesign, show, and sell for the price he wants.........but yeah it is easier to just criticize and complaint. The only thing that really counts is work done and shown results.

I wonder why Troels Gravesen thinks he can design a better crossover than the engineers at Yamaha??
Oh yeah he sells them for 900 Euros the pair.

 

[Ericglo]

The NS1000 was an exceptional loudspeaker at the time, and not embarrassing even now. See Figure 18.3. The only problem was that they were designed for a flat sound power target, so they were slightly bass shy - turn up the bass and/or turn down the treble for better balance. The NS-10 was also designed for flat sound power, and in a two-way that was most regrettable - although inexplicably many recording engineers got sucked into what can only be described as a "fashion". Truthfully it was an Auratone with more bass. The designer visited me at the NRCC and went away swearing never to do it again. He didn't, and subsequent Yamaha monitors were flat on axis. Section 12.5.1 in the 3rd edition discusses this and shows measurements.

Maybe Troels could do better. From Floyd's post, it looks like the designer would have changed it as well.

In a subsequent post, Frank Dernie said he did turn down the mid and treble.

 

[antennaguru]

I stopped using midrange drivers a long time ago because the lower crossover point from the woofer to the midrange driver was in too critical a frequency range within the audio band, and was always too easy for me and others to hear as a discontinuity, and find distracting. I am a believer in the expression that "there is no crossover, like no crossover", but unfortunately every single full range driver that I have ever heard fell well short of expectations, and had too many discontinuities in the highs, nor enough bass - and ended up adding subwoofers crossed over fairly high plus add-on super-tweeters to sound OK - but the overall response of the full range driver was still quite bumpy.

Accordingly, in my own design work a compromise evolved. I began to use stereo subwoofers crossed over below 80Hz, which is a non-critical crossover point to the ear, and then I crossover the mid-woofer in the main speakers to the tweeter in the main speakers higher than normal at around 3.5KHz, which is again a better place for a crossover point. Not having any crossover point in the critical center band (80Hz to 3.5KHz) has been a great improvement in my opinion. Today there are an abundance of mid-woofers that I have found can cover this range very nicely.

 

[gene_stl]

Troels sells it. Jantzen just takes the order.
I consider them to be slightly higher grade snake oil salesmen.
Everyone is entitled to their opinion. Even if it's wrong.
Loudspeaker systems are the last great bastion of superstition in audio. Most dearly adored "improvements" would not pass blinded testing.

 

[Frank Dernie]

I wonder why Troels Gravesen thinks he can design a better crossover than the engineers at Yamaha??
Oh yeah he sells them for 900 Euros the pair.

To be fair he doesn't make a big thing about it and when I read his article years ago I decided the measurements showed it didn't make enough difference to be worth it (for me)

 

[McFly]

Bliesma domes should be out this year.

If they pull off the same shot they did with thier tweeters, these will be REALLY good, and REALLY expensive.

 

[MrPeabody]

DIY builders enjoy fairly good availability of domes in the 2" range, whereas off-the-shelf 3" domes are less common. There are several 2" domes from Morel, also HiVi, but one that has been highly regarded for a number of years is Dayton Audio / PE RS52. Presently there is both a cloth version and an anodized aluminum version. My recollection is that the aluminum version was first and that the cloth version was recently added.

Most of the 2" domes use underhung motors the same as tweeters, with the height of the coil a few mm shorter than the height of the gap. This helps with keeping the moving mass low and the DCR low, both toward better efficiency and sensitivity. If the moving mass is greater this can easily be compensated so that the upper end of the frequency response won't suffer, but generally this requires a stronger motor which means greater electrical damping and thus low efficiency and sensitivity. The limiting factor in linear excursion is more likely the motor than the suspension, and this is likely true even with the exceptions that use an overhung motor. Xmax is typically only about 1 mm. This suggests that the improved dispersion (as compared to a small cone with the same piston radius) may be moot. By that I mean the 2" dome can't play clean low enough in frequency for the improved dispersion to be much of an advantage. DIY builders using 2" domes probably don't run them below about 1 kHz, i.e., about one octave lower than the typical crossover point for a 1" dome tweeter. This small advantage may be significant with a 4-way design, but 4-way designs aren't common, and with a non-esoteric 3-way speaker, the midrange needs to go low enough to meet up with a woofer somewhere around 300 Hz. Drivers this size, with piston diameter about 2", end up in a sort of no-man's land (both domes and cones). In order for a dome midrange to be readily usable in a 3-way design, it needs to be larger to improve efficiency and thus permit a lower crossover point. It is a curious thing that 3" dome midranges are the norm with 3-way active speaker designs but are not commonly found in passive 3-way speakers. The reason may have to do with the fact that a midrange that is less sensitive than the woofer is not a big deal in an active design whereas in a passive design this is ordinarily undesirable.


A concept that I find interesting is Morel's TM4055-8, where both a conventional tweeter and conventional midrange are both mounted on a single plate, closer together than is practically attainable with each of them mounted on its own separate plate. The drawback (other than the cost) is that the midrange dome is just barely greater than 2". If I were building a 4-way speaker I would seriously consider using it, but not for a 3-way speaker. Unusually, the motors (both the midrange and the tweeter) are overhung designs, with the coil heights greater than the height of the gap. As compared to a concentric pair, the essential advantage of this arrangement is that the dispersion of the tweeter is not restricted by the midrange. Smoothness in vertical directivity is probably nearly as good as with a typical concentric setup, while dispersion should be better than with most any concentric setup. Unfortunately, you still end up needing a bigger midrange to cover the gap from a few hundred Hz up to 1 kHz. I suppose you could use it in a 3-way design with a mid-woofer maybe 165 mm (6.5"). But I wouldn't build a 3-way speaker with a woofer this small. In any case it seems to be a unique and interesting approach.

https://www.madisoundspeakerstore.com/approx-2-midrange/morel-tm4055-8-tweeter-midrange/

 

[headshake]

Simulations with VituixCAD seem to show that the closest spacing may not provide the best overall power response. According to VituixCAD developer something between 1.2 and 1.5 fc wavelength appears to provide the best power response while 0.5 to 0.7 provides the worst case result.
With your assumption of 3000hz, 15cm (11.5cm x 1.3) should be a preliminary target, hence large physical diameter is not necessary a issue even if small diameter means more spacing freedom.

This kinda brings up the point: mid domes are for far-field speakers. You do want drivers close together if you want to sit close to the drivers for near-field.

Near field has different requirements because power response has not much effect and early reflections should be avoided. So very short c-c or coaxial would be better.

VituixCAD thread on diyaudio contains three examples with real life data and simplified theoretical study about c-c = 1.2 x wave length concept. It's actually quite common in practice. Traditionally XO frequencies 2.5-5 kHz were common, and sound of those speakers was typically smoother and more tolerable than (modern) low XO point. So I'm not trying to invent anything new or provoke. Just giving an answer why some sound features were better in the past; no blood from ears while listening 80s' Gary Moore or Iron Maiden.
Common (modern) opinion/statement is that c-c should be as short as possible. With "normal luck" it hits c-c = 1/2 wave length at XO which causes the worst possible power dip and balance break with conventional unidirectional box speaker. Also risk of power bump above XO point increases with conventional tweeters without wave guide. c-c = 1/4 wave length at XO is just an utopia - worthless to mention for other than XO between mid and woofer, or woofer and small full-range as a tweeter.

- kimmo

https://www.audiosciencereview.com/forum/index.php?threads/some-help-with-lobing.22661/post-753404

 

[Chromatischism]

I stopped using midrange drivers a long time ago because the lower crossover point from the woofer to the midrange driver was in too critical a frequency range within the audio band, and was always too easy for me and others to hear as a discontinuity, and find distracting. I am a believer in the expression that "there is no crossover, like no crossover", but unfortunately every single full range driver that I have ever heard fell well short of expectations, and had too many discontinuities in the highs, nor enough bass - and ended up adding subwoofers crossed over fairly high plus add-on super-tweeters to sound OK - but the overall response of the full range driver was still quite bumpy.

Accordingly, in my own design work a compromise evolved. I began to use stereo subwoofers crossed over below 80Hz, which is a non-critical crossover point to the ear, and then I crossover the mid-woofer in the main speakers to the tweeter in the main speakers higher than normal at around 3.5KHz, which is again a better place for a crossover point. Not having any crossover point in the critical center band (80Hz to 3.5KHz) has been a great improvement in my opinion. Today there are an abundance of mid-woofers that I have found can cover this range very nicely.

That sounds perfect for a small tweeter for wide dispersion and a broad sweet spot:

https://techtalk.parts-express.com/.../64968-sb19-tweeter-for-the-iron-driver/page5

And in a good waveguide it is exceptional (proprietary example):

 

[dfuller]

DIY builders enjoy fairly good availability of domes in the 2" range, whereas off-the-shelf 3" domes are less common.

Off-the-shelf 3" domes, I can only think of two currently available. One is the $107 Scan Speak D7608/92000-10 (which needs a sealed chamber in the cabinet as it's open back), and the other is the $500+ Volt VM752. You used to be able to get the ATC SC75-150, but no longer. As far as I know the ATC is the only dome you could actually comfortably cross around 3-400hz but I am also not super well versed.

 

[MrPeabody]

...
- kimmo
https://www.audiosciencereview.com/forum/index.php?threads/some-help-with-lobing.22661/post-753404

FWIW, I had some difficulty sorting out your post because with respect to the two lower inserts which were excerpts from other posts in other threads, the identification information is missing. And immediately below those two inserts, there is "-kimmo" which makes it seem that you are Kimmo. This was confusing.

When I read the post by @Savi I recalled encountering this idea a couple of months ago. It was a thread that @ctrl had started to present some simulations he had done, concerned with vertical polar response. That thread is titled, "Crossover filter - Effects on the vertical radiation". And of course it turns out that it was you who brought this up also in that previous thread.

The claim as I vaguely understand it is that from the perspective of the power response, it is better for the center-to-center vertical spacing of two drivers to be not less than 1.2 x wavelength at the crossover point. This evidently is based at least partly on a simulation study. One question that springs to mind is whether this is actually concerned with the room and ceiling reflections. If it is appropriate to prefer or eschew things on the basis of power response effects, then we should strongly disdain the use of phase-coherent crossovers where each driver's pressure response is -6 dB at the crossover point, because with this type of crossover, total acoustic power at the crossover point is half as great as the nominal acoustic power, away from the crossover point, notwithstanding that the pressure responses combine in a way that renders the pressure response flat through the crossover point, for detection points directly in front of the speaker and equidistant from both drivers.

For two drivers that are phase coherent for a detection point equidistant from both drivers, the + and - vertical polar angles at which nulls occur, caused by destructive interference, are related in a mathematically precise manner to the vertical spacing between the two drivers. (In order for the + and - angle to be equidistant from the horizontal plane, i.e., in order for the main lobe to not be tilted, we have to additionally assume that the two drivers are mounted with their acoustic origination points in vertical alignment.) The smaller the vertical spacing of the two drivers, the greater the angular separation between the two nulls. This simple, substantive fact is very persuasive to me, more so than something that has not been adequately well explained, that is concerned specifically with the power response, and that may incorporate assumptions concerning the height of the ceiling, the distance from the speaker to the listener, etc.

This claimed effect has now been brought up at least three times on ASR, in three different threads. As such it seems likely that this will occur henceforth, each and every time that anyone says anything about the vertical spacing of drivers. Perhaps there should be a thread on ASR dedicated expressly to this effect, not to vituixCAD generally, but to this one effect specifically. It is highly desirable with something like this for the underlying assumptions to be clearly identified, at least, and thus far this has not happened, at least not on ASR, to the best of my knowledge. As for the provided link to the vituixCAD thread on diyAudio, it is not remotely realistic for anyone to be expected to read through that 316-page thread to try and figure out exactly what this claim even is.

 

[headshake]

This claimed effect has now been brought up at least three times on ASR, in three different threads. As such it seems likely that this will occur henceforth, each and every time that anyone says anything about the vertical spacing of drivers. Perhaps there should be a thread on ASR dedicated expressly to this effect, not to vituixCAD generally, but to this one effect specifically. It is highly desirable with something like this for the underlying assumptions to be clearly identified, at least, and thus far this has not happened, at least not on ASR, to the best of my knowledge. As for the provided link to the vituixCAD thread on diyAudio, it is not remotely realistic for anyone to be expected to read through that 316-page thread to try and figure out exactly what this claim even is.

Yeah, his thread is a long mess to try to pull info out. There are sims of real speakers in there that do show what he is talking about. I've seen it, but don't have the links handy. If I can find the info I'll post it in the vert. thread and here.

The claim is easy to see in vcad. Model two drivers in vcad, make an XO, and play with the v. spacing. The DI will change.

We mess with the X moving speaker from the walls. We mess with the Y when we position the tweeter in space. Is it so odd to position the drivers for a sphere at Z in space? This is my newbie view of it. Many of you have forgotten more than I know so let me know if this sounds wrong.

 

[MattHooper]

One of the most coherent sounding speakers, with one of the most beautiful rich, natural midranges I've ever heard in my room, where surprisingly enough Shun Mook Bella Voce speakers. They used a dome mid driver:

 

[Wolf]

TMK, Morel uses underhung arrangements in their dome drivers.

I have a love for mid domes, and have several awaiting designs. They just do some things very right.

My favorites include the ATC and derivatives, Usher 9845, and Morel MDM55 and EM1308.

 

[MrPeabody]

Yeah, his thread is a long mess to try to pull info out. There are sims of real speakers in there that do show what he is talking about. I've seen it, but don't have the links handy. If I can find the info I'll post it in the vert. thread and here.

The claim is easy to see in vcad. Model two drivers in vcad, make an XO, and play with the v. spacing. The DI will change.

We mess with the X moving speaker from the walls. We mess with the Y when we position the tweeter in space. Is it so odd to position the drivers for a sphere at Z in space? This is my newbie view of it. Many of you have forgotten more than I know so let me know if this sounds wrong.

It's just that considering that this has been brought up several times, it seems to me that there should have been stronger effort to explain why this particular vertical separation, 1.2 x wavelength, is deemed superior to all other choices. I did a calculation and found that with this specific vertical separation of the two drivers, the null in the lobe pattern (the null that divides the main forward lobe from the secondary lobe above the main lobe) will be aimed at about +/- 30 degrees from the horizontal. Surely this is the primary consequence of using 1.2 x wavelength for the vertical separation, and as such it seems reasonable to infer that what the recommendation comes down to is the belief that +/- 30 degrees from the horizontal is the optimal angle for the aiming of the null (the null caused by destructive interference between the two drivers, at the crossover frequency).

I thus pondered the question of why this particular angle would be deemed ideal, and preferable to a more vertical angle. All I could think of is that with this angle, the null is likely to strike the ceiling directly over the listener's head, such that the first reflection of the null, off the ceiling, would not influence the sound perceived by the listener. But of course if this is the correct understanding, it incorporates assumptions with respect to seating height, speaker height, listener distance from speaker, and ceiling height. If it happens that this is the correct understanding of why 1.2 x wavelength is deemed optimal, then I don't understand why it wouldn't have been explained in a manner like this: "In a typical home setting, if the vertical spacing between the two drivers is made as small as it can practically be made, this is likely to result in the listener sitting directly in line with the ceiling reflection of the null, and since this will most often be true, it is preferable for the vertical separation between the two drivers to equal 1.2 x wavelength, so that the null will strike the ceiling above the listener's head."

Manifestly there is a tradeoff for aiming the null at 30 degrees from the horizontal: when you are walking around the room close to the speakers, the occasions when your ears encounter the null will be more frequent for this low angle as compared to steeper aiming of the null. Given that there is this obvious tradeoff, and given that the 1.2 x wavelength criterion makes several assumptions with respect to listening distance, ceiling height, etc., it does not seem proper to give the impression that 1.2 x wavelength is optimal in an absolute sense. Yet this is the impression that has been given, i.e., that 1.2 x wavelength has been determined to be optimal in an absolute way. And this is what I found annoying. My immediate reaction was that contrary to how it had been presented, it is not likely to be optimal in an absolute sense, but only under particular circumstances which might not apply and which were not identified, and even then accompanied by tradeoffs.

 

[MrPeabody]

TMK, Morel uses underhung arrangements in their dome drivers.

I have a love for mid domes, and have several awaiting designs. They just do some things very right.

My favorites include the ATC and derivatives, Usher 9845, and Morel MDM55 and EM1308.

As I previously discussed, these drivers are not usable much lower in frequency than about 1 kHz, due to the small volumetric displacement, with diaphragm diameter barely greater than 2" and with only 1 mm of linear excursion. Given this practical limit on the low end of range, this kind of driver is not optimal for a 3-way speaker, where the midrange should ideally cover more than three octaves, from about 300 Hz to about 2 kHz, in ballpark terms. The drivers that work best, for this operating range, are drivers with diaphragm diameter in the range of 4" to 6". Also, both of these Morel drivers are overhung, with coil height of 6 mm and gap height of 4 mm. This doesn't much matter, although it is a bit curious that the designers chose to do this given that the linear excursion range is not greater than the typical value for a typical 1" tweeter. The only downside is that there is a slight loss in efficiency and in sensitivity, although no matter how slight this effect is, it is for no benefit given that there is no improvement in linear excursion. In order to have improved the linear excursion the coil would need to have been made even longer than 6 mm. This would have further reduced the efficiency and sensitivity. If they had used an underhung design, using a shorter coil and a greater gap height, they should have been able to improve the linear excursion by way of increasing the gap height, with no loss in efficiency and sensitivity.

 

[MrPeabody]

If I were strongly inclined to use a dome midrange in a 3-way speaker, I would consider this dome by Peerless/Tymphany available through PE:

https://www.parts-express.com/Peerless-GBS-85N25PR03-04-3-1-2-Paper-Cone-Midrange-4-Ohm-264-1494

The diameter is better than it is with the more common 2" domes, but not by as much as you might think if you focus on the "3 1/2" description. The specifications from the manufacturer indicate that the "effective" dome diameter is 6.7 mm = 2.64", and this most likely includes some of the surround. However the slight improvement in diameter gives it a significant improvement in piston area, 35 cm^2 vs. 28 cm^2 for the more common 2.125" dome midrange. The linear excursion is given as 2.1 mm, twice greater than the typical 1 mm value for a 2" dome. The net effect of the advantage in piston diameter and linear excursion is that the advantage in volume displacement is 2.1 x 35/28 = 2.6. With volume displacement 2 1/2 times greater than it is with a typical 2" midrange, this dome midrange should be usable a octave lower, to perhaps 500 Hz, depending on how loud you want it to play. This is low enough in frequency that it would not be unreasonable to build a 3-way speaker using this dome midrange.

The reason for the greater linear displacement probably is more about the motor than the suspension. The coil height is not stated in the specs, but the gap height is given as 3 mm. Together with the low DCV, this suggests that the motor is probably underhung, i.e., that the coil height is probably about 1 mm, about the same as it typically is with a tweeter. Interestingly, the coil diameter is given as 25.7 mm, just barely more than 1", which obviously means that the coil former joins to the dome not at the edge of the dome but rather slightly inward from the edge of the dome. If the manufacturer's graph of frequency response is to be believed, it is extremely flat from about 150 Hz to 2 kHz. It would be interesting to see measurements of distortion for this driver, because it may well be the ideal midrange to fill the directivity gap between a 6" or 7" woofer and a typical 1" tweeter. For a woofer larger than this, I would still go with a larger midrange.

There is also a true 3" soft dome by ScanSpeak, however it seems to offer minimal advantage over the smaller domes because the linear excursion is .8 mm. It uses an overhung motor with coil height 2.9 mm and gap height 2 mm. This is a little surprising given that the coil is 3" in diameter. This suggest a somewhat high value for DCR of the coil and somewhat low efficiency and sensitivity. DCR is 5.7 ohm and sensitivity is quoted as 92 dB. However this quoted sensitivity value is very misleading because the response has a horrific peak. To be usable down to 500 Hz the peak will have to be squashed and the effective sensitivity will only be about 85 dB, not so good. The peakiness of the response will be further exacerbated by the high Q of the driver unless the enclosure for it is impossibly large, because total Q is 1.73. The same issue is encountered to a lesser extent with the Peerless dome, which is similarly open in the back, but which has Qts .63. While this is greater than is to be desired it is usable, even though it wants to be given as much volume as can be allocated to it. (Qts is greater than the maximum value at which the enclosure volume would be less than Vas for resulting system Q of .7; Vas is 1.6 liter. This suggests that in a typical application its response will likely exhibit a modest peak at the low end, however it should not be difficult to correct this in the applied high-pass filter.)

Once again the fundamental limitation of large domes becomes apparent. The large diameter of the coil implies greater mass and larger DCR, which confounds good efficiency and sensitivity. It is manifest that the motor should be underhung to avoid this fundamental drawback, but even when the coil is short, sensitivity is barely acceptable without using larger diameter for the coil wire, and larger diameter for the coil wire increases the mass, such that it ends up sort of like a dog chasing its tail so to speak. Ultimately in order to achieve a flat response to adequately high frequency it is necessary to use a coil that is both short and small in diameter, like Tymphany did with the GBS-85N25PR03-04. If I were wanting to build a 3-way speaker with a woofer not larger than 6.5", I would seriously consider using this dome midrange.