Originally posted by john k ...
"Dipoles and cardioids only achieve the theoretical radiation pattern in the free field. Free field means 3 to 10 wavelengths away from the source"
That’s surely a problem for most Dipoles or cardioid users?
The oft quoted guideline for distance off the wall for dipoles is “just” 1.8 m
at say 100 Hz, where wavelengths are 3.43 m, very few domestic rooms would have enough space to allow even one wavelength.
How suboptimal is half a wavelength, or say 1 m?
"Dipoles and cardioids only achieve the theoretical radiation pattern in the free field. Free field means 3 to 10 wavelengths away from the source"
That’s surely a problem for most Dipoles or cardioid users?
The oft quoted guideline for distance off the wall for dipoles is “just” 1.8 m
at say 100 Hz, where wavelengths are 3.43 m, very few domestic rooms would have enough space to allow even one wavelength.
How suboptimal is half a wavelength, or say 1 m?
The same is true for monopoles as well. Below the Schroeder frequency ALL speakers primarily feed the room mode pattern and not their inherent radiation pattern. Let the Schroeder frequency be 300 Hz. That would give a wavelength of 1,1 m. This distance from the wall would not be the optimum, but good enough to not trouble ones head about it.
Rudolf
I can verify by experience what Rudolf says!
My AINOproto is now in a small 9m2 room and the monopole bass sounds wonderful! The xo from W to dipole mid is 300Hz and yes, the bass is tight and articulated and when I close my eyes the bass instruments' sound comes from the dipole lower mid driver, not from the floor where the woofer is jumping!
My friend has a dipole 2xSLS12" H-frames per side in a heavily treated 15m2 room and they are marginally better except sub 30Hz area (to my ears).
john k's statement in another thread here launched my "easy way" decision to make a monopole bass solution for Ainos. A Finnish hifi-magazine recently had a comparison of Gradient 1.x against Gradient Helsinki 1.5 and they liked monopole bass more too.
Room and it's modes are THE main limiting factor for bass reproduction (<200-300Hz) and, excluding nearfield, you can't beat it with transducer's radiation pattern.
My AINOproto is now in a small 9m2 room and the monopole bass sounds wonderful! The xo from W to dipole mid is 300Hz and yes, the bass is tight and articulated and when I close my eyes the bass instruments' sound comes from the dipole lower mid driver, not from the floor where the woofer is jumping!
My friend has a dipole 2xSLS12" H-frames per side in a heavily treated 15m2 room and they are marginally better except sub 30Hz area (to my ears).
john k's statement in another thread here launched my "easy way" decision to make a monopole bass solution for Ainos. A Finnish hifi-magazine recently had a comparison of Gradient 1.x against Gradient Helsinki 1.5 and they liked monopole bass more too.
Room and it's modes are THE main limiting factor for bass reproduction (<200-300Hz) and, excluding nearfield, you can't beat it with transducer's radiation pattern.
Rudolf
I want to get very clear on the issue of placement.
John K’s statement about radiation pattern following theory effectively only above 3 wavelengths, suggested to me that the advantage of dipoles in bass might well be less than I (for one) thought
I recall that the area where dipoles have the *most advantage over monopoles is *below the Schroeder frequency, as their inherent radiation pattern means they are less subject to room modes
“Let the Schroeder frequency be 300 Hz. That would give a wavelength of 1,1 m. This distance from the wall would not be the optimum, but good enough to not trouble ones head about it”
Are you saying that while 1.1 m corresponds to as high a frequency as 300 Hz, that enough of the dipole’s advantage in radiation pattern remains below that - so even if you place dipoles as close as 1.1 m from the wall, you still get less room modes than a monopole, ie smoother bass down to 100 Hz, and even lower?
I want to get very clear on the issue of placement.
John K’s statement about radiation pattern following theory effectively only above 3 wavelengths, suggested to me that the advantage of dipoles in bass might well be less than I (for one) thought
I recall that the area where dipoles have the *most advantage over monopoles is *below the Schroeder frequency, as their inherent radiation pattern means they are less subject to room modes
“Let the Schroeder frequency be 300 Hz. That would give a wavelength of 1,1 m. This distance from the wall would not be the optimum, but good enough to not trouble ones head about it”
Are you saying that while 1.1 m corresponds to as high a frequency as 300 Hz, that enough of the dipole’s advantage in radiation pattern remains below that - so even if you place dipoles as close as 1.1 m from the wall, you still get less room modes than a monopole, ie smoother bass down to 100 Hz, and even lower?
John K also has a nice simulation of rear boundary effects for monopole, dipole and cardioid sources on his website: Boundary effects
The distance to the wall, judged by the notches in the monopole response, is about 0.5 m. Judging by the depth of the notches, I would estimate that observation distance to the source is about 4.5 m.
The response of the cardioid sources seems unaffected except at very low frequencies. This seems to be consistent with my measurements. At about 0.7 m behind my speaker I can already measure the deep null down to about 80 Hz (haven't been able to measure lower without reflections). In room I haven't seen any significant boundary interaction, despite only 0.35 m distance from baffle to the front wall.
I've been working on a similar simulation based on point sources in Excel, so I can vary wall distance, listening distance and dipole/cardioid source separation. I haven't finished it yet for the dipole and cardioid sources though. Been busy lately so I haven't been very active here on DIY.
The distance to the wall, judged by the notches in the monopole response, is about 0.5 m. Judging by the depth of the notches, I would estimate that observation distance to the source is about 4.5 m.
The response of the cardioid sources seems unaffected except at very low frequencies. This seems to be consistent with my measurements. At about 0.7 m behind my speaker I can already measure the deep null down to about 80 Hz (haven't been able to measure lower without reflections). In room I haven't seen any significant boundary interaction, despite only 0.35 m distance from baffle to the front wall.
I've been working on a similar simulation based on point sources in Excel, so I can vary wall distance, listening distance and dipole/cardioid source separation. I haven't finished it yet for the dipole and cardioid sources though. Been busy lately so I haven't been very active here on DIY.
When someone talks about the "radiation pattern" of a dipole, this always rings "figure 8" in my mind. With regard to "figure 8" John K's statement is completely right IMHO.
That is generally right. But I would substitute "radition pattern" by "working principle". Below the Schroeder frequency I think of a dipole as two monopoles with opposite phase and a fixed distance between them. By rotating these monopoles you have an added degree of freedom to control room interaction, which the monopole doesn't give you. Apart from that you might have less excitation of floor-ceiling modes.
I don't think that "less" room modes is the target - it is "better control" of room modes. And I wouldn't say that dipoles do this better in each and every case. But they certainly do it in all cases, where all trials with monopoles didn't achieve acceptable bass quality. Individual room situations are too different to make one principle the "winner" and everything else "loosers". But having more degrees of freedom (see above) is helpful in every case. And yes, it is helpful below 100 Hz, even if you are only 1 m away from a wall.
Rudolf
Rudolf,
Quote:
“By rotating the (two) monopoles you have an added degree of freedom to control room interaction, which the monopole doesn't give you”
I hadn’t thought of it that way, but if the radiation pattern is figure-8, rotating could well bring a benefit
Quote:
“When someone talks about the "radiation pattern" of a dipole, this always rings "figure 8" in my mind”
Me too
Quotes:
“I would substitute "radiation pattern" by "working principle"”
“you might have less excitation of floor-ceiling modes”
“I wouldn't say that dipoles do better in each and every case”
My understanding of dipoles is mostly from Linkwitz' site. I’m pretty sure he didn't give a “disclaimer”. Maybe-probably you are simply being more realistic
I thought you might-could have less excitation in all three directions?
Quote:
“By rotating the (two) monopoles you have an added degree of freedom to control room interaction, which the monopole doesn't give you”
I hadn’t thought of it that way, but if the radiation pattern is figure-8, rotating could well bring a benefit
Quote:
“When someone talks about the "radiation pattern" of a dipole, this always rings "figure 8" in my mind”
Me too
Quotes:
“I would substitute "radiation pattern" by "working principle"”
“you might have less excitation of floor-ceiling modes”
“I wouldn't say that dipoles do better in each and every case”
My understanding of dipoles is mostly from Linkwitz' site. I’m pretty sure he didn't give a “disclaimer”. Maybe-probably you are simply being more realistic
I thought you might-could have less excitation in all three directions?
The figure 8 metapher only makes sense when room modes are dense. For low frequencies you better think of distributed point sources in the room. John K did some simulations about this in his Tech Studies .
Compared to SL I'm a daydreamer.
But when SL started his site he probably didn't intend it to be the final textbook on dipoles. I believe it was meant as a resource to help people to better understand the Orion concept. So there were - and are - aspects he has not covered. But which he certainly knows one or two things about!
Rudolf
Room has modes regardless of speaker type. Which modes and extent of excitation is dependent on speaker type and placement.
Simulations are great, but measurements reveal what is possible.
Here is link to cardioid system about 1m from side wall and 2m from front wall, and what may be accomplished with EQ: Cardioid
Here is posting of same elements located more central to listening space; monopole and dipole elements are run independently, and together. Results show that from listener perspective that monopole, dipole, and cardioid may be filtered to produce nearly identical response: Cardioid Revisited
I see no advantages, only compromises.
Some great posts here. Thank you all!
Most of the material on SL’s site on dipoles came out about the time of the Orion’s predecessor, the Phoenix c 2001.
Yes not intended as the final text on dipoles. A resource to help people to better understand his Phoenix; maybe also a guide to designers?
Thank you for pointing out refinements/ developments I was not aware of!
Which of John's Tech studies were you referring to? One of these:
The U-Frame Woofer
http://www.musicanddesign.com/u_frame.html
The Influence of Boundary Reinforcement on Monopole, Dipole and Cardioid Woofers
http://www.musicanddesign.com/Boundary_reflections.html
Design of woofer with varying directionality
http://www.musicanddesign.com/VariabDF.html
A configuration for subwoofers yielding characteristics of dipole bass
http://www.musicanddesign.com/DP_woofer_room.html
Barleywater, Thank you for your links
I have a dipole midbass 3/4 built, with a 15 inch midbass. It came to a halt when I moved house.
I’m now thinking that in a few months, when I have a workbench again and complete it, - maybe- I should try to allow a way of converting it between dipole and cardioid. See what works better/ where. So far I have not read much at all on cardioids
I recall one of John K’s earlier designs (on bass c 30 - 120 Hz) might have made this easy/ easier? A variant on the U-frame?
Anyone seen or done a convertible dipole/ cardioid that worked?
Most of the material on SL’s site on dipoles came out about the time of the Orion’s predecessor, the Phoenix c 2001.
Yes not intended as the final text on dipoles. A resource to help people to better understand his Phoenix; maybe also a guide to designers?
Thank you for pointing out refinements/ developments I was not aware of!
Which of John's Tech studies were you referring to? One of these:
The U-Frame Woofer
http://www.musicanddesign.com/u_frame.html
The Influence of Boundary Reinforcement on Monopole, Dipole and Cardioid Woofers
http://www.musicanddesign.com/Boundary_reflections.html
Design of woofer with varying directionality
http://www.musicanddesign.com/VariabDF.html
A configuration for subwoofers yielding characteristics of dipole bass
http://www.musicanddesign.com/DP_woofer_room.html
Barleywater, Thank you for your links
I have a dipole midbass 3/4 built, with a 15 inch midbass. It came to a halt when I moved house.
I’m now thinking that in a few months, when I have a workbench again and complete it, - maybe- I should try to allow a way of converting it between dipole and cardioid. See what works better/ where. So far I have not read much at all on cardioids
I recall one of John K’s earlier designs (on bass c 30 - 120 Hz) might have made this easy/ easier? A variant on the U-frame?
Anyone seen or done a convertible dipole/ cardioid that worked?
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Just to chip in, I am a owner of the Nao Note - the cardoid bass works - have to use the particular damping material prescribed by John K.
Bass spl is much higher than dipole when u are at the sweet spot - about 6 foot from speaker - I can hear the midbass and feel the low bass - all without eq and bass traps - the bass sounds almost the same with svs as-eq1, but with more resolution
And yet not in the sweet spot - no bass perfect for bedtime listening at night.
U frame rear is only about 40 cm from wall
The 4 peerless woofer for small room bass spl is on par with my old setup of 2 hsu-mbm12 and 2 hsu uls15
Hi,
... i agree to that statement.
But the initial post was about using a cardioid in a frequency range from say 120Hz to 400Hz. This is typically/often not the "pure" modal range anymore. Depending on the room's size and furniture there may be a "transitional" range above the "modal" range, before the rooms gets "statistical".
Above 120Hz many living rooms - especially when somewhat larger sized and heavily furnitured - may be well within the "statistical" range already and 120Hz in fact may be the range of the Schröder Frequency itself in many rooms.
A cardioid speaker may very well be dimensioned in a way to exhibit a "proper" radiation pattern over the 2 octaves requested and needing just a moderate displacement volume, which may be approx. double than that needed in a monopole speaker comparable in max SPL. To achieve that, the dipole path length should be optimally adjusted for that particular range of wavelengths to be radiated.
When designing for a somewhat lower crossover Frequency - say 80Hz - a more "independent" main speaker is feasible (as a satellite), which may be combined with a subwoofer system of choice matched to the given room and listener's requirements (multisub, dba, sba, one ore more dipole subs, ...).
Such a cardioid woofer from say 80Hz to about 400Hz should be a decent system, allowing for reduced early reflections (bottom, side wall, front wall, ceiling ). And it may also allow for rather close placement due to the front wall IMO, which is different to a dipole speaker. The radiation pattern may be "affected" by the room but still be "experienced", depending on the room's given Schröder Frequency.
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