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Old 20th February 2013, 05:40 PM   #21
Face is offline Face  United States
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Quote:
Originally Posted by Pallas View Post
Cardoid down to 120Hz? Do you have a thread about the build/design?
I'm going to give this a try with the AE TD15M.
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Old 20th February 2013, 10:41 PM   #22
Pallas is offline Pallas  Pakistan
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I'm going to give this a try with the AE TD15M.
Are you going with a U-frame or porous side-walls (or both)?
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Old 20th February 2013, 10:47 PM   #23
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Are you going with a U-frame or porous side-walls (or both)?
I'm going to experiment with porous side walls first.
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Old 22nd April 2013, 06:14 AM   #24
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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?
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Old 22nd April 2013, 07:06 AM   #25
Rudolf is offline Rudolf  Germany
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Quote:
Originally Posted by otto88 View Post
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"
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.

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Old 22nd April 2013, 04:43 PM   #26
Juhazi is offline Juhazi  Finland
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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.
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Old 23rd April 2013, 08:00 AM   #27
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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?
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Old 23rd April 2013, 08:53 AM   #28
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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.
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Old 23rd April 2013, 10:23 AM   #29
Rudolf is offline Rudolf  Germany
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Quote:
Originally Posted by otto88 View Post
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
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.
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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
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.
Quote:
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 ... down to 100 Hz, and even lower?
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.

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Old 24th April 2013, 07:44 AM   #30
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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?
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