Stuck in my head, input needed
You might find this post interesting if:
- You like thinking about creative solutions for unconventional problems;
- You like unconventional box designs;
- You like more questions than answers;
- You like my weird thinking;
- You like long posts.
Designing the system of my dreams. I want to walk around the room and not deal with phase cancellation or beaming issues. My ideal speakers sound good at any listening position, can play loud, feel like they're 'breathing', and have an immersive and encompassing quality to them. I have boggled it down to some more concrete requirements. Please bear with me as my convoluted brain processes unfold themselves.
My demands:
- Full range system
- Response 40Hz to 8kHz
- Ability to fill 50m³ room (1766 cubic feet)
- Ability to play loud
- Omnidirectional sound dispersion
Let's break those down!
Full range: Self-explanatory. Definitely no crossover.
Response 40 to 8kHz: Okay, perhaps not full full range... I will be adding in biamped supertweeters (sue me!), but I have all that figured out already. These boxes will be run full range without crossover, and 40-8kHz is what they have to cover. I'm asking your help regarding solely these boxes that will be run full range.
Ability to fill room: 50 cubic meters at least, preferably more. The boxes will have to be able to do this without effort.
Ability to play loud: Sometimes I play metal music loudly and then I don't care much about the audiophile characteristics. Often I will turn down the bass frequencies to take some strain off the drivers. That said, I'm probably wanting drivers with above average Xmax, say 3-5mm (about 1/8th inch - 3/16th inch)
Omnidirectional sound dispersion: Here the interesting part begins!
Traditional omnidirectional speaker designs make use of an upward firing driver that shoots audio into a waveguide of sorts, usually a concave cone that reflects audio 360° [attachment 1]. The sound heard would be the sound that is reflected off the waveguide. Unfortunately, this leads to some loss of sensitivity (compared to the point-source measurements supplied by the manufacturer). A driver that is listed as 96dB/m (1W) will most likely measure around 93dB/m when integrated in this traditional omnidirectional box design. (Correct me if I'm wrong.) Loud full range drivers are rare to begin with, so losing sensitivity is tough when my other requirement is for these speakers to play loud.
This introduces some unconventional restrictions on the box design. For the last months, I have been weighing the pros and cons of two options:
- Upward firing driver into a flared conical waveguide [attachment 1]
- Multiple smaller drivers shooting upward into the air [attachment 2]
Let's break it down.
Option 1 - Upward firing driver into waveguide: This is the traditional omnidirectional design. I would want a high-sensitivity driver with a stiff cone that can handle about 40 Watts nominal, and has about 3-5mm Xmax. How about that for asking for the impossible…
Though I do think I would have some options here. For example, the Tangband W8-1808 is rated 93dB/m and 30W nominal, while having a stiff bamboo cone and an Xmax of 5mm (about 3/16th inch). Firing this driver upward into a concave cone might still yield ~92dB/m in the upper midrange and about 90dB/m in the lower midrange/upper bass. Combined with a bass reflex, extension to 40Hz could perhaps still be about 89dB/m, which is not unreasonable, if one considers all my demands. (These are educated guesses.) Often I turn down the bass a little bit when I crank up the total volume, so the driver should be able to play anything above 120Hz or so even louder, whilst the decreased bass in the input signal and a not-very-low Qts cause the conus to stay inside the Xmax boundaries. Extending a little outside of the Xmax when cranked is not a problem IMO.
While I think this design would be possible, it does greatly reduce my options regarding driver choice: not many drivers meet the required specifications. I think most drivers that remain are about 8"-10"-12" in diameter and will have to be cone-treated to ameliorate cone breakup issues. Beaming is not much of an issue because of the waveguide.
( In case of the Tangband: 100L ported box (about 3½ cubic feet) tuned to 40Hz. )
Option 2 - Multiple drivers firing upward: Another way to achieve omnidirectional sound dispersion is by having a driver fire upward. The sound you hear then is for the greatest part reflected sound from adjacent walls, and also the ceiling. This design is tried and tested and works great for omnidirectional sound dispersion, but has downsides. Having the driver fire up into the air greatly reduces perceived sensitivity at the point of listening (3dB/m at least, most likely more), since most waves hit the ceiling and the walls before they reach the ear. However, since no waveguide is hanging above the driver, it is possible to multiply the amount of drivers. For example, one could have 4 full range drivers firing upward in order to achieve omnidirectional sound. This would in turn lead to a higher total system sensitivity and a lower required Xmax per driver. Think of it like an upward-firing driver array… that eliminates comb-filtering because of its dispersion pattern. However, since beaming is a thing, smaller drivers would be required in order to achieve pleasant omnidirectional sound dispersion. Luckily, since there are a lot of small-ish full-range drivers (4" or so) out there, a lot more drivers that fit the specs remain as an option.
Other options that I have ruled out:
Angled bipoles: Nope I don't want the large dead spot down the middle
Angled dipoles: Too much drop in efficiency, especially in the bass
OB dipoles out in the room: Don't have enough space in my room to make those truly viable
So, according to my rationale, I'm stuck at a fork in the road, having to choose between the two options listed above. Even though I'm having tunnelvision and I'm missing lots of stuff, I would still like to compare these two options here. I find it hard to imagine whether they would satisfy my demands. I also find it hard to weigh their pros and cons in relation to the ideal that I have in my head.
Therefore I'm curious to your thoughts regarding the two options that I listed.
- Do you think either would satisfy my demands?
- Would you specifically advise against one of the two?
- Do you have experience with either option? Please share.
(Be kind!)
Cheers,
Raoul
You might find this post interesting if:
- You like thinking about creative solutions for unconventional problems;
- You like unconventional box designs;
- You like more questions than answers;
- You like my weird thinking;
- You like long posts.
Designing the system of my dreams. I want to walk around the room and not deal with phase cancellation or beaming issues. My ideal speakers sound good at any listening position, can play loud, feel like they're 'breathing', and have an immersive and encompassing quality to them. I have boggled it down to some more concrete requirements. Please bear with me as my convoluted brain processes unfold themselves.
My demands:
- Full range system
- Response 40Hz to 8kHz
- Ability to fill 50m³ room (1766 cubic feet)
- Ability to play loud
- Omnidirectional sound dispersion
Let's break those down!
Full range: Self-explanatory. Definitely no crossover.
Response 40 to 8kHz: Okay, perhaps not full full range... I will be adding in biamped supertweeters (sue me!), but I have all that figured out already. These boxes will be run full range without crossover, and 40-8kHz is what they have to cover. I'm asking your help regarding solely these boxes that will be run full range.
Ability to fill room: 50 cubic meters at least, preferably more. The boxes will have to be able to do this without effort.
Ability to play loud: Sometimes I play metal music loudly and then I don't care much about the audiophile characteristics. Often I will turn down the bass frequencies to take some strain off the drivers. That said, I'm probably wanting drivers with above average Xmax, say 3-5mm (about 1/8th inch - 3/16th inch)
Omnidirectional sound dispersion: Here the interesting part begins!
Traditional omnidirectional speaker designs make use of an upward firing driver that shoots audio into a waveguide of sorts, usually a concave cone that reflects audio 360° [attachment 1]. The sound heard would be the sound that is reflected off the waveguide. Unfortunately, this leads to some loss of sensitivity (compared to the point-source measurements supplied by the manufacturer). A driver that is listed as 96dB/m (1W) will most likely measure around 93dB/m when integrated in this traditional omnidirectional box design. (Correct me if I'm wrong.) Loud full range drivers are rare to begin with, so losing sensitivity is tough when my other requirement is for these speakers to play loud.
This introduces some unconventional restrictions on the box design. For the last months, I have been weighing the pros and cons of two options:
- Upward firing driver into a flared conical waveguide [attachment 1]
- Multiple smaller drivers shooting upward into the air [attachment 2]
Let's break it down.
Option 1 - Upward firing driver into waveguide: This is the traditional omnidirectional design. I would want a high-sensitivity driver with a stiff cone that can handle about 40 Watts nominal, and has about 3-5mm Xmax. How about that for asking for the impossible…
Though I do think I would have some options here. For example, the Tangband W8-1808 is rated 93dB/m and 30W nominal, while having a stiff bamboo cone and an Xmax of 5mm (about 3/16th inch). Firing this driver upward into a concave cone might still yield ~92dB/m in the upper midrange and about 90dB/m in the lower midrange/upper bass. Combined with a bass reflex, extension to 40Hz could perhaps still be about 89dB/m, which is not unreasonable, if one considers all my demands. (These are educated guesses.) Often I turn down the bass a little bit when I crank up the total volume, so the driver should be able to play anything above 120Hz or so even louder, whilst the decreased bass in the input signal and a not-very-low Qts cause the conus to stay inside the Xmax boundaries. Extending a little outside of the Xmax when cranked is not a problem IMO.
While I think this design would be possible, it does greatly reduce my options regarding driver choice: not many drivers meet the required specifications. I think most drivers that remain are about 8"-10"-12" in diameter and will have to be cone-treated to ameliorate cone breakup issues. Beaming is not much of an issue because of the waveguide.
( In case of the Tangband: 100L ported box (about 3½ cubic feet) tuned to 40Hz. )
Option 2 - Multiple drivers firing upward: Another way to achieve omnidirectional sound dispersion is by having a driver fire upward. The sound you hear then is for the greatest part reflected sound from adjacent walls, and also the ceiling. This design is tried and tested and works great for omnidirectional sound dispersion, but has downsides. Having the driver fire up into the air greatly reduces perceived sensitivity at the point of listening (3dB/m at least, most likely more), since most waves hit the ceiling and the walls before they reach the ear. However, since no waveguide is hanging above the driver, it is possible to multiply the amount of drivers. For example, one could have 4 full range drivers firing upward in order to achieve omnidirectional sound. This would in turn lead to a higher total system sensitivity and a lower required Xmax per driver. Think of it like an upward-firing driver array… that eliminates comb-filtering because of its dispersion pattern. However, since beaming is a thing, smaller drivers would be required in order to achieve pleasant omnidirectional sound dispersion. Luckily, since there are a lot of small-ish full-range drivers (4" or so) out there, a lot more drivers that fit the specs remain as an option.
Other options that I have ruled out:
Angled bipoles: Nope I don't want the large dead spot down the middle
Angled dipoles: Too much drop in efficiency, especially in the bass
OB dipoles out in the room: Don't have enough space in my room to make those truly viable
So, according to my rationale, I'm stuck at a fork in the road, having to choose between the two options listed above. Even though I'm having tunnelvision and I'm missing lots of stuff, I would still like to compare these two options here. I find it hard to imagine whether they would satisfy my demands. I also find it hard to weigh their pros and cons in relation to the ideal that I have in my head.
Therefore I'm curious to your thoughts regarding the two options that I listed.
- Do you think either would satisfy my demands?
- Would you specifically advise against one of the two?
- Do you have experience with either option? Please share.
(Be kind!)
Cheers,
Raoul
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