-much below about 400 Hz and beyond a few feet distance from the source: pattern control is pretty much lost regardless of the implementation.
This isn't to say however that there isn't a difference, both with respect to the gradient as it gets close to the source and the interaction with the room, but rather that a practical difference in pattern control pretty much goes "AWOL" in a typical domestic condition.
Okay, you said it--so prove it. IOW, back it up with something other than your own assertions. Personal subjective observations can help, but they certainly need more to back them up.
I have to say that the only real factor that I can find is Toole's citations on binaural localization vs. frequency for certain types of sounds (which converts to directionality of the hearing system). As the frequency goes below the interaural distance, directionality begins to suffer. Elephants have extremely good directionality and low frequency extension of their hearing systems. Humans have less good performance. But other than that, I can find nothing else that supports what you say, and in fact my own subjective experiences strongly conflict with what you've said.
It's not that I don't believe you believe what you said, it's rather that I don't believe that what you said is actually accurate. I've found no reason to arbitrarily abandon directivity at 500 or 800 Hz--because that's the frequency at which 15" or 18" direct radiating woofers lose their directivity. I'm actually very disappointed to see that no one else is challenging these old notions--which I find are actually incorrect.
Chris
I have to say that the only real factor that I can find is Toole's citations on binaural localization vs. frequency for certain types of sounds (which converts to directionality of the hearing system). As the frequency goes below the interaural distance, directionality begins to suffer. Elephants have extremely good directionality and low frequency extension of their hearing systems. Humans have less good performance. But other than that, I can find nothing else that supports what you say, and in fact my own subjective experiences strongly conflict with what you've said.
It's not that I don't believe you believe what you said, it's rather that I don't believe that what you said is actually accurate. I've found no reason to arbitrarily abandon directivity at 500 or 800 Hz--because that's the frequency at which 15" or 18" direct radiating woofers lose their directivity. I'm actually very disappointed to see that no one else is challenging these old notions--which I find are actually incorrect.
Chris
Here's a polar plot for a Jubilee bass bin (anechoically measured by Klipsch) along with the predicted response. The plot's vertical axis has a typo in the units shown--which are in degrees, but other than that, the plot speaks for itself:
I've been in the chamber while it was testing, and listened in the room next door to the chamber, and I can say that this directivity is quite audible when compared to one, two and four 15" woofer reflex bins (sequential A-B comparisons), which I heard in the opposite corner of the room compared in A-B fashion at the same trial. The trials included a dialed-in B&C driver on a K-402 horn on top.
Chris
I've been in the chamber while it was testing, and listened in the room next door to the chamber, and I can say that this directivity is quite audible when compared to one, two and four 15" woofer reflex bins (sequential A-B comparisons), which I heard in the opposite corner of the room compared in A-B fashion at the same trial. The trials included a dialed-in B&C driver on a K-402 horn on top.
Chris
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Is that a typical domestic condition? I'd argue that most would be closer to 200 Hz.
Also, reflections from room surfaces take their toll - leading to something less directive at distance (measured). It's not just a matter of modal conditions.
As for a good measurement under this condition, I couldn't find what I was looking for.. likely because everyone is trying for an anechoic response.
(..having in the distant past tried to get good low freq. data (anechoic) from a mic. at distance in a typical listening room has been utterly useless, which is why it's sort of "automatic" to make a response like I did.)
In any event, I wouldn't expect you to take my word for it (..I'm really not that sort of person), if you've got a mic. available software/computer you could try this on your own system - with results that you could believe. And for your system/room/setup: I could be wrong.
Anyway, note Earl's response (a few posts down) to Rudolf here:
https://www.diyaudio.com/forums/roo...monopole-dipole-responses-46.html#post3203835
Also, reflections from room surfaces take their toll - leading to something less directive at distance (measured). It's not just a matter of modal conditions.
As for a good measurement under this condition, I couldn't find what I was looking for.. likely because everyone is trying for an anechoic response.
(..having in the distant past tried to get good low freq. data (anechoic) from a mic. at distance in a typical listening room has been utterly useless, which is why it's sort of "automatic" to make a response like I did.)
In any event, I wouldn't expect you to take my word for it (..I'm really not that sort of person), if you've got a mic. available software/computer you could try this on your own system - with results that you could believe. And for your system/room/setup: I could be wrong.
Anyway, note Earl's response (a few posts down) to Rudolf here:
https://www.diyaudio.com/forums/roo...monopole-dipole-responses-46.html#post3203835
It's normally in the area of 200 Hz and 300 Hz in living rooms.
But it's a transition and can be effected by building materials, windows, etc.
With my large mid bass horn I tend to see a flatter response around 150 Hz compared to other designs despite that dimensions of the room gives a theoretical higher schroeder frequency.
So your argument is that some listening rooms have terrible acoustics (including the rooms being too small and too lightly treated with absorption), so the loudspeakers (...all of them...) can ignore directivity requirements down to 100 Hz because of this?
I've seen this sort of thinking before. It usually results in doing everything the way that "we've always done it before"...in my experience. (It's also called "mediocrity for all".) I don't know about you, but I try to design my loudspeakers to exceed those kinds of constraints because over time I find ways to achieve a better environment for sound reproduction in my home.
YMMV.
Chris
Both the Kii Three's and D&D 8c's have controlled directivity down to 100 Hz. They are cardioid designs, but use two different approaches, one passive, one active to achieve this result. You can see the polars in the linked reviews.
The JBL 4722 I use with the 2384 waveguide and stacked double 15" woofers have constant directivity down to about 400 Hz. I use a JBL 2453H-SL 4" compression driver on the 2384 waveguide crossed at the factory recommended 630 Hz in a biamp setup. Sounds pretty good time aligned.
Came to this thread to see what other large waveguide options are available. The Synergy designs and the K-402 look interesting...
The JBL 4722 I use with the 2384 waveguide and stacked double 15" woofers have constant directivity down to about 400 Hz. I use a JBL 2453H-SL 4" compression driver on the 2384 waveguide crossed at the factory recommended 630 Hz in a biamp setup. Sounds pretty good time aligned.
Came to this thread to see what other large waveguide options are available. The Synergy designs and the K-402 look interesting...
in my particular case I'm going to use the system outdoors sometimes and in much larger than domestic spaces so controlled directivity as low as possible is desirable. I actually considered dipole sub bass just using enormous quantities of drivers but I decided that was just a bit silly and in small rooms using 4 sealed subwoofers is a known well performing and flexible solution in the HT community.
No. My "argument" (..it's not really an argument at all), is that if you are really interested you'll make the measurements yourself - because quite obviously ONLY that will satisfy you.
..and again, I've no problem with being proven incorrect for your setup.
I also don't think that directivity (constrained or not) or a particular type of loading (horn) might offer benefits owing to something OTHER than a particular polar-pattern in a "far-field" condition (in a typical domestic listening room).
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-because the environments are so dissimilar, DEFINITELY consider an "active" DSP implementation. ..minidsp is usually the "go-to" solution here.
A Cardiod solution is usually preferred out-doors, where it really does drop the spl behind the loudspeaker (..and sum's well with more directive upper freq.s).
With DSP, you can not only do a compound loaded arrangement (where you time-delay the front speaker relative to the rear speaker to get the directive pattern you want), but can also use a high-pass filter (low-freq. cut) on the design for out-door use so that you don't over-drive the woofers.
A bass array (floor/ground loaded) can also be useful for less pressure loss with distance.
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found a low cost'ish (compared to the k-402) very large constant directivity horn:
JBL 365359-001 2384 Horn/Waveguide for 3732 - Speaker Exchange
this is the wave guide from the JBL 3732 and 4722:
http://www.jblproservice.com/pdf/Theatre Series/4722-HF.pdf
381 x 762 x 381 mm
1.5" throat so presumably will also work with 1.4" drivers. Nominal Coverage: 90° horizontal, -30°, +20° vertical.
I already use a mini-dsp and have been using DSP since the days of kx drivers for the Audigy 2, I'm a big fan, everyone should use it. In terms of DSP platform my preference would be to develop my own using a FPGA but I'm probably going to use a DCX2496 on this system for the moment just for cost reasons. Cardiod would be great but I would need more amp channels and more drivers, like with a synergy horn the priority is to get something working quickly and then improve it rather than spending months experimenting. Old speakers can easily sold on.
JBL 365359-001 2384 Horn/Waveguide for 3732 - Speaker Exchange
this is the wave guide from the JBL 3732 and 4722:
http://www.jblproservice.com/pdf/Theatre Series/4722-HF.pdf
381 x 762 x 381 mm
1.5" throat so presumably will also work with 1.4" drivers. Nominal Coverage: 90° horizontal, -30°, +20° vertical.
I already use a mini-dsp and have been using DSP since the days of kx drivers for the Audigy 2, I'm a big fan, everyone should use it. In terms of DSP platform my preference would be to develop my own using a FPGA but I'm probably going to use a DCX2496 on this system for the moment just for cost reasons. Cardiod would be great but I would need more amp channels and more drivers, like with a synergy horn the priority is to get something working quickly and then improve it rather than spending months experimenting. Old speakers can easily sold on.
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Agreed about DSP being the way to go, but I don't think the DCX2496 is a step up from minidsps! At least go for something that supports FIR filtering -- not because "waveform accurate" or "linear phase" is essential to have, but being able to adjust phase independently of shape is one heck of lot more flexible. I'm using a 2x4HD and it beats the old DCX in every way I can think of.... and smaller, too.
The k-420 is 1002x648x422 WxHxD in mm
(Klipsch K402 replica build - DIY Audio Projects - StereoNET )
while the JBL 2384 is 762x381x381 WxHxD in mm
In the JBL 3 way its crossed at 1.2 kHz and in the two way its crossed at 630 Hz or 800 Hz depending on whether the active crossover option is selected. So its usable to 630 Hz even if its not maintaining constant directivity. so its
76% of the way there