Looking at the distortion characteristics of these small drivers, they will most definitely benefit from reflex loading. And yes, a high-pass is basically mandatory.
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sphere shaped speakers
- Thread starter rokr
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restorer-john
Grand Contributor
Heitaro Nakajima set up a company for retired Japanese engineering colleagues and one of their pet projects were these:
more measurements: https://www.nhlab.jp/speaker
Sokel
Master Contributor
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Here's some material for your research,as Cabasse and spheres are synonymous:
www.cabasse.com
Cabasse: For demanding audiophiles
The Official Cabasse website. Discover our HiFi speakers and systems designed to give audiophiles the essence of pure sound.
www.cabasse.com
I might be mixed up, but I am not sure that this is how it works, although it's commonly repeated in these threads. The calculation for spherical modes doesn't appear to produce a big peak at that wavelength...?This is exactly the problem. Because you only have one dimension in al directions, you will have one pronounced resonance. This tends to be much worse than spread-out resonances.
https://www.acs.psu.edu/drussell/Publications/Basketball.pdf
The frequencies of resonances of a sphere also don't follow an integer ratio, unlike resonances you get from parallel surfaces. So in other words the resonances aren't evenly spaced.
I think this leads to a subjectively less objectionable artifact than evenly spaced resonances. My made-up theory is that the resonances interfere with music less because musical harmonics are usually evenly spaced.
We are all probably familiar with this unevenly spaced series of "harmonics" - it's why bouncing a ball makes such a recognizable sound.
If I check Table I in the above PDF the first resonance they captured was at 963Hz - I guess it would be more interesting to see the resonances below 200Hz
But then if I check Fig. 1 it does show response from 0Hz and apparently there is only one resonance between 0 and 500Hz (around 400Hz)
Does this mean that (at least in the experiment mentioned in the PDF) there was no resonance below 400Hz?
Also it would be great if anybody here with experience in COMSOL could actually simulate the standing waves in a sphere.....
- Thread Starter
- #46
This is what I call flush mount.
About this stand, is this a better way than using spikes?
Hi,
standing waves in enclosed space start from half wavelength and up, nodes at the boundaries. https://en.wikipedia.org/wiki/Standing_wave
If your sphere is 34cm in diameter, which is wavelength of 1kHz, then first mode would be 500Hz and no modes can form below that because wavelength is too long to fit inside the enclosure. Basically, on lower frequencies whose wavelength is ever longer, pressure inside the enclosure behaves rather uniformly, following movement of the cone.
So, to get resonance at 200Hz, which is about 1.7m in wavelength, diameter of the sphere would need to be about 85cm. It's hard to have sphere this big, but it's very common dimension with a floor standing speaker for example.
Out of any shapes, sphere has smallest surface area and shortest internal dimensions with given volume. Small internal dimensions mean all resonances inside are higher up in frequency and possibly outside of pass band than with any other shape. Small surface area means that even if the surface vibrates, the area is smaller than with equivalent volume cubicle, thus resulting SPL would be less. Well, perhaps that's too much simplification, but since it's one surface I'd imagine it cannot balloon without stretching, and if it vibrates there will be both positive and negative displacement likely averaging out each other. Also, no edges outside of the structure which means no secondary sound sources with diffraction. All of these combined ought to result in "less box sound".
I see no downside using spherical enclosure audiowice, other than some dictation for c-c spacing which has implication in system level. Sphere is relatively hard to manufacture traditionally though, and perhaps aesthetically not as nice as cubicle, which I think are the reasons why spherical speakers are not more common.
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restorer-john
Grand Contributor
It's Japanese and I don't profess to understand exactly what they were shooting for. Heitaro is R.I.P. , but every loudspeaker he had a hand in was truly amazing.
That egg speaker is a small driver, but likely a proof of concept design.
- Thread Starter
- #51
Well, the drivers for this sphere project will be mark audio's Chr70.3. When I inserted all the parameters to winisd everything looked good but then I got to cone excursion… this is a 20W driver, but according to winisd using 20W it will bottom out at 110Hz. Only when lowering the power considerably to 9W, it will stay under it's 4.3Xmax.
I wasn’t sure if it’s a mistake I did, so I found that the official website has lots of suggested box plans. I found a simple plan (designed by mark Fenlon) which has a volume close to my sphere - https://www.markaudio.com/wp-content/uploads/2021/08/Fenlon-70CHR.png When I inserted to Winisd, everything lined up with the plans but again, needs to go down to 7W to avoid bottoming out. I also tried the fancier Alpair7 MS – got exact same results
Am I missing something or this what a tiny driver like that will give you?
I wasn’t sure if it’s a mistake I did, so I found that the official website has lots of suggested box plans. I found a simple plan (designed by mark Fenlon) which has a volume close to my sphere - https://www.markaudio.com/wp-content/uploads/2021/08/Fenlon-70CHR.png When I inserted to Winisd, everything lined up with the plans but again, needs to go down to 7W to avoid bottoming out. I also tried the fancier Alpair7 MS – got exact same results
Am I missing something or this what a tiny driver like that will give you?
Hi, If you confirmed another plan, which gives you similar readings as yours, then it's likely true. I have no experience of the driver so cannot say more accurately. I had 5" Jordan JX92s fullrange drivers and speakers at one point, which couldn't go very loud and were bottomed with my 40W amp.
If it is a reflex box you must use high pass filter to limit excursion, which goes wild below the tuning frequency with no audible output. You should high pass filter with any box for such small driver, low frequencies would eat all the xmax, while not being audible anyway, so you might as well high pass in order to have less excursion which means cleaner (less distortion) sound for rest of the bandwidth. In case of fullrange driver this means cleaner sound for the whole full range bandwidth. I really cannot over emphasize how important high pass filter is with such speaker.
Some words to give some perspective how system size relates to apparent output capability:
There is not much bass from a small volume displacement and this is the trade-off with fullrange drivers in general, wide bandwidth comes with low SPL capability. You could use 15" fullrange driver for more lows and thus SPL capability, but now the highs are compromised instead. It's better to compromise the lows, and just add more low frequency sources, like a subwoofer. Or any bigger woofer, perhaps back of the sphere, which would both increase SPL capability, extend low frequency bandwidth and also clean up sound of mids and highs.
It's the low frequency extension and SPL requirement that is the hardest to fullfill and usually determines whole system SPL capability. Low frequency extension and SPL is all about volume displacement. So, if one wants to listen full bandwidth low distortion audio at reference level around 80db or so, with dynamics to spare so say 95db capability at one meter, from say 30Hz and up, small speakers just can't do it no matter what the marketing material says. They can sound just fine, just don't except having a party with nice sound.
Speaker system with 15" woofers as bass is about cool, enough volume displacement that enables whole system sound dynamic and big and natural and so on, and allows do some partying. Simplified, the smaller the speaker system, the smaller the sound as well, which can be somewhat counteracted by shrinking listening distance. I do not know what would be smallest system for average living room with 2-3m listening triangle, perhaps volume displacement of average 12" or even 10" could be enough, or even 6" if there is great xmax, which makes the volume displacement equivalent to average 12" for example. As reference, even a cell phone can get pretty loud with it's microscopic transducer, there just isn't any lows with it, and the sound is heavily distorted. To surpass cellphone apparent loudness with fullrange capable system with low distortion is already quite a feat. There is dramatic difference in system size, so even if a speaker system has 15" drivers which might sound dramatic, really isn't that much more output capability, but sufficiently so to get apparently louder than a cell phone with full range bandwidth and nice sound quality. Still, far from live instruments played in the same room, hit of a snare drum makes so loud sound, even system with 15" bass would strugle to reproduce.
ps. chr70 has 50cm2 Sd and about 4mm xmax, so about 50x0.8= 40cm3 volume displacement. A 10" subwoofer Seas LROY26 has about 340cm2 Sd and 14mm one way xmax making whopping 340x2,8 = 950cm3 volume displacement, which is equivalent of about 23pcs chr70, which is roughly 24db more output capability at some low frequency you target for. Top of my head, perhaps something like 300-500cm3 might be enough for partyable sound in a livingroom, give or take, and the more the better party 40cm3 could do party loud on mids and highs,if lows are high passed.
If it is a reflex box you must use high pass filter to limit excursion, which goes wild below the tuning frequency with no audible output. You should high pass filter with any box for such small driver, low frequencies would eat all the xmax, while not being audible anyway, so you might as well high pass in order to have less excursion which means cleaner (less distortion) sound for rest of the bandwidth. In case of fullrange driver this means cleaner sound for the whole full range bandwidth. I really cannot over emphasize how important high pass filter is with such speaker.
Some words to give some perspective how system size relates to apparent output capability:
There is not much bass from a small volume displacement and this is the trade-off with fullrange drivers in general, wide bandwidth comes with low SPL capability. You could use 15" fullrange driver for more lows and thus SPL capability, but now the highs are compromised instead. It's better to compromise the lows, and just add more low frequency sources, like a subwoofer. Or any bigger woofer, perhaps back of the sphere, which would both increase SPL capability, extend low frequency bandwidth and also clean up sound of mids and highs.
It's the low frequency extension and SPL requirement that is the hardest to fullfill and usually determines whole system SPL capability. Low frequency extension and SPL is all about volume displacement. So, if one wants to listen full bandwidth low distortion audio at reference level around 80db or so, with dynamics to spare so say 95db capability at one meter, from say 30Hz and up, small speakers just can't do it no matter what the marketing material says. They can sound just fine, just don't except having a party with nice sound.
Speaker system with 15" woofers as bass is about cool, enough volume displacement that enables whole system sound dynamic and big and natural and so on, and allows do some partying. Simplified, the smaller the speaker system, the smaller the sound as well, which can be somewhat counteracted by shrinking listening distance. I do not know what would be smallest system for average living room with 2-3m listening triangle, perhaps volume displacement of average 12" or even 10" could be enough, or even 6" if there is great xmax, which makes the volume displacement equivalent to average 12" for example. As reference, even a cell phone can get pretty loud with it's microscopic transducer, there just isn't any lows with it, and the sound is heavily distorted. To surpass cellphone apparent loudness with fullrange capable system with low distortion is already quite a feat. There is dramatic difference in system size, so even if a speaker system has 15" drivers which might sound dramatic, really isn't that much more output capability, but sufficiently so to get apparently louder than a cell phone with full range bandwidth and nice sound quality. Still, far from live instruments played in the same room, hit of a snare drum makes so loud sound, even system with 15" bass would strugle to reproduce.
ps. chr70 has 50cm2 Sd and about 4mm xmax, so about 50x0.8= 40cm3 volume displacement. A 10" subwoofer Seas LROY26 has about 340cm2 Sd and 14mm one way xmax making whopping 340x2,8 = 950cm3 volume displacement, which is equivalent of about 23pcs chr70, which is roughly 24db more output capability at some low frequency you target for. Top of my head, perhaps something like 300-500cm3 might be enough for partyable sound in a livingroom, give or take, and the more the better party
40cm3 could do party loud on mids and highs,if lows are high passed.
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*Disclaimer: I don't know anything about building speaker, so take everything with two pinches of salt!*
I think the idea with the bowls is great, and have played around a bit with WinISD, Vituixcad and CAD software.
I don't know if it comes close to reality, but this is the result (Would have to be active):
Red Speaker at the back: Dayton Audio E150HE-44 5-1/2" in approx. 7.5l Volume
Sharp Highpass at 20Hz and a 6dB Boost in the 30Hz region, it could reach a f3 of about 40 Hz (f6 @ 30Hz) or if you push it even harder a f3 @30Hz.
Violet Speaker at the Front: Maybe a Markaudio CHR70 or similar (or even smaller?).
I think the idea with the bowls is great, and have played around a bit with WinISD, Vituixcad and CAD software.
I don't know if it comes close to reality, but this is the result (Would have to be active):
Red Speaker at the back: Dayton Audio E150HE-44 5-1/2" in approx. 7.5l Volume
Sharp Highpass at 20Hz and a 6dB Boost in the 30Hz region, it could reach a f3 of about 40 Hz (f6 @ 30Hz) or if you push it even harder a f3 @30Hz.
Violet Speaker at the Front: Maybe a Markaudio CHR70 or similar (or even smaller?).
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- Thread Starter
- #54
Looks very interesting, but as I am also new to speaker building, I can't really give you technical feedback on this. It makes me think about a chimney style port at the top
What I can tell you is that one of the limitations of this build was using drivers up to a 100$, so these Daytons are way over the budget.
Another goal was to keep things as simple as possible, one driver, no crossover (preferably no filter at all), while reaching decent audio quality.
there are Speakers like fruggel horns, cibelius, and also smaller less sophisticated speakers that used this kind of drivers with good results.
Sokel
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Hi, sure, marketing can beat physics, easily
While bandwidth of the system is likely 30-27kHz as per the document, the SPL numbers are not related to the bandwidth but derived with some high mid tones, what ever magic trickery they got highest number with. They conveniently do not mention that the 115db is not at 30Hz.
Achieving 115dB@30Hz would require about 1300cm3 volume displacement ( in closed box, see chart in Diyaudio ).
Taking Dayton RS180 as an example, a 7" woofer, datasheet says it has about 130cm2 Sd. To achieve 1300cm3 volume displacement, the xmax would need to be about 5cm, to one direction, 10cm of cone travel in total, that would be quite violent show.
If the 7" woofer had 5mm xmax, there would need to be 10 pieces of them to make 115dB@30Hz capable system.
Single 7" woofer, a really good one with great xmax of 1.5cm for example, could do 300-400cm3, which could make bit over 100dB a 30Hz.
The RS180 I used here has 6mm xmax, and could do about 150cm3, about 95db or so.
A ported box could add another 6db output around the low knee, so 100-106dB is the actual maximum output from one speaker, with 10% distortion which is often tied to xmax, or more, because xmax readings can be tweaked to almost what ever. Looking Klippel data from audioexpress test bench for example, many many woofers reach audible distortion due to nonlinear suspension or Bl lot sooner than datasheet xmax.
So, take say 15db headroom for dynamics a speaker with 7" bass could be listened roughly with 90db@30Hz with great audible distortion, at one meter. Very low frequencies are ruthless, small woofers just don't cut it.
For reference, single 15" woofer with about 7.5mm xmax could do 115db@30Hz full tilt, in sealed box even. It would take many hundrez watts of power and be quite loud and start compressing soon when heat builds up. A serious reflex box would be better, or even better two 15", or bigger. This is PA territory. Nobody listens these levels at home so capability of 115db is not really needed. But, a speaker with 15" bass is a lot more fun than speaker with 7" bass even with typical listening levels, and allows occasional party fun
While bandwidth of the system is likely 30-27kHz as per the document, the SPL numbers are not related to the bandwidth but derived with some high mid tones, what ever magic trickery they got highest number with. They conveniently do not mention that the 115db is not at 30Hz.
Achieving 115dB@30Hz would require about 1300cm3 volume displacement ( in closed box, see chart in Diyaudio ).
Taking Dayton RS180 as an example, a 7" woofer, datasheet says it has about 130cm2 Sd. To achieve 1300cm3 volume displacement, the xmax would need to be about 5cm, to one direction, 10cm of cone travel in total, that would be quite violent show.
If the 7" woofer had 5mm xmax, there would need to be 10 pieces of them to make 115dB@30Hz capable system.
Single 7" woofer, a really good one with great xmax of 1.5cm for example, could do 300-400cm3, which could make bit over 100dB a 30Hz.
The RS180 I used here has 6mm xmax, and could do about 150cm3, about 95db or so.
A ported box could add another 6db output around the low knee, so 100-106dB is the actual maximum output from one speaker, with 10% distortion which is often tied to xmax, or more, because xmax readings can be tweaked to almost what ever. Looking Klippel data from audioexpress test bench for example, many many woofers reach audible distortion due to nonlinear suspension or Bl lot sooner than datasheet xmax.
So, take say 15db headroom for dynamics a speaker with 7" bass could be listened roughly with 90db@30Hz with great audible distortion, at one meter. Very low frequencies are ruthless, small woofers just don't cut it.
For reference, single 15" woofer with about 7.5mm xmax could do 115db@30Hz full tilt, in sealed box even. It would take many hundrez watts of power and be quite loud and start compressing soon when heat builds up. A serious reflex box would be better, or even better two 15", or bigger. This is PA territory. Nobody listens these levels at home so capability of 115db is not really needed. But, a speaker with 15" bass is a lot more fun than speaker with 7" bass even with typical listening levels, and allows occasional party fun
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Yes. Would love to hear the LS50 Meta driver used.I would try a coaxial driver instead of a full-ranger - we're on ASR, after all
The budget is rather restricting (quite impossible if crossovers are accounted for) but the SB Acoustics SB12PFCR25-4-COAX gets pretty close
CJH
This is really cool, LOVE IT!!!
Congratulations @rokr !
I have ordered four CHN110 drivers, I am planning to do the same sometime next year
May I ask what you put under the speakers? That little wooden thingy
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