Think of it this way
cardioid = 1/2 monopole + 1/2 dipole
The woofer of a passive cardioid is given two duties. It must function as a monopole and as a dipole. A reasonably sized woofer (say 8" or smaller) in a closed box has no problem playing down to 50 Hz, which is the monopole contribution. So far, so good. This is the reference to which you compare the distortion, by the way.
Now imagine you take the same woofer and mount it in an open baffle, to generate the dipole contribution. It must be equalized heavily to play 50 Hz at the same level and therefore it will be forced to move lots of air. This larger cone excursion means more distortion.
Tmuikku, AllenB and TBTL: thank you!
Fluid comment now make sense.
Allen, what kind of CD did you use with this waveguide? Is it the one in place within your corner loaded system?
I'm still impressed by this kind of 'plaster built'. Ellipson made a huge range in 60's built like that, including spherical enclosure and reflector based design.
Fluid comment now make sense.
Allen, what kind of CD did you use with this waveguide? Is it the one in place within your corner loaded system?
I'm still impressed by this kind of 'plaster built'. Ellipson made a huge range in 60's built like that, including spherical enclosure and reflector based design.
Was the test conclusive?
For wathever reason i thought OS profile could not be used in a synergy.
Clever use of hose!
For wathever reason i thought OS profile could not be used in a synergy.
Clever use of hose!
Conclusive for what? I was able to cross it below 250Hz but by 150Hz room modes become a problem.
Danley uses rectangular conicals but I notice one of the aims is arrayability.
Danley uses rectangular conicals but I notice one of the aims is arrayability.
You're welcome 🙂
The last link is a master's thesis discussing cardioid to lower frequencies. there is a lot of background at the start but it gets somewhere at the end. It is easy enough to poke holes in the methodology used but I think the experiments are interesting.
Getting high directivity at low frequencies is considerably harder to do and whether it is worth the effort/cost/size depends a lot on the use case.
Speakers like the 8c or the Kii 3 are being designed to overcome some of the problems of mixing in rooms that are really too small. The speakers cannot be far enough away from walls so directivity is being used to limit the interaction between the speaker and the boundaries, or make use of it where it is beneficial.
A 15" woofer in a box that is not too deep can have almost the same directivity down to about 300Hz without any loss of output. Room treatment and multiple subwoofers can deal with the rest if you are willing to use them.
A cardioid bass source makes more sense in a room that is not treated and where the speakers can/will only be placed in one position.
There have been a few threads where some well known people have argued the merit to cardioid bass.
https://www.diyaudio.com/community/threads/cardioid-bass.121590/
As has been already stated, if large enough, no problem.
Dave Gunness of Fulcrum Acoustic has figured out how to make passive subcardioid cabinets using single low frequency drivers in relatively small mid/hi and subwoofer enclosures.
The 12" CCX1295 is ~90deg @ -6dB at 500Hz:
I am very impressed with how well the Fulcrum Acoustic passive subcardioid designs work for the size.
Art
Again thanks all for your input. I still haven't found the time to read all the linked documents.
I'd personally always consider the use of subs to play the sub 100~150hz since it seems to help greatly with the constraints of the rest of the system
and seems quite easy to buy/build.
ok reading time now 🙂 thanks all !
tmuikku: yeah 1 meter starting to get quite large, but i've seen some pretty large bass horns that weren't to shabby to look at 🙂
Charles Darwin: Awesome link, i'll look at all their waveguides/horns with the details .. appreciated 🙂
AllenB: woa!! you are working on this right now ? do you have a thread with some details ? impressive 🙂
TBTL : yes seems very logical the same unit will be asked to work much harder for the same perceived output !
fluid : ic yes ... end use consideration is a must obviously . Still trying to understand the limits of what can be done within achievable limits
Could i ask why a 15" in a box that is shallow ? why smaller box ? Does it affect directivity or you are referring to output at lower frequencies ?I'd personally always consider the use of subs to play the sub 100~150hz since it seems to help greatly with the constraints of the rest of the system
and seems quite easy to buy/build.
ok reading time now 🙂 thanks all !
A cabinet that is wider than it is deep in most cases will produce a cardioid/supercardioid response through a reasonable range much more so that one that is a similar depth to width or deeper. It has to do with how the diffraction from the rear corners of the enclosure affect the pattern.
You can see an example here, where even at 293Hz the rear output is 10dB less than the frontal and -15dB around 140 degrees which is more supercardioid.
https://www.audiosciencereview.com/...e-platform-speaker-project.20407/post-1082442
fluid : I just finished reading through Geedes and PiSpeakers links ..what a superb combo of reading 🙂
much appreciated links ..i was also able to link many things i've learned here since 2-3 weeks with those and this time it was much easier to understand most of what was discussed !! ( to my surprise )
Ah that's super nice. So we can use the rear diffraction to passivly shape the from radiation ( or should i say the sides lol ) that low with the cabinet ?I don't have time today for the 3rd ( seems rather complex and long ) link but i will give it a try sooner than later.
I'd have a few questions if i may.
1- Would setting the drivers to an angle up ( toward the ceiling ) to some low degrees ( 0~30deg ) to help lower the VER from the floor help ? Pretty sure i've seen a few commercial loudspeakers with tilted mid/tweets but ..might be wrong here
2- A somewhat shorty waveguide for the woofer on a 2-way ( let's assume a CD waveguide HF unit with a 10-15" woofer 2 way )
with a smaller vertical angle than the horizontal, similarly to what we often see ( JBL and the 90X45 stuff )
Could it be done to have some effect to kinda " push " the directivity control down some more , while helping with the floor reflection and not creating a huge driver to driver distance problem ?
Hmmmm, I think we have to call something like that (tmuikku's) "cardioidish" 😉
..really, why not put a pro 15 driver in a muffler the length of the driver's depth and "call it a day" - that will provide something that's far more cardioid in that 100-400 Hz range. If driver Qts is a bit higher (with a large Vas and lower Fs) you'll even have some added pressure lower in freq. to combat some of the loss in pressure from the side-leakage.
Ex.
http://www.sbaudience.com/index.php/products/various-drivers/bianco-15ob350/
Still, I tend to prefer the result of a Dipole here (as adason mentioned) - even with the rear-wave reflecting off of the wall behind the loudspeakers.
https://www.diyaudio.com/community/threads/adventures-in-cardioid.142691/#post-1808306
..and this is what a real cardioid response should look like as it looses pressure off-axis:
https://www.diyaudio.com/community/threads/adventures-in-cardioid.142691/#post-1808323
..and this is what a real cardioid response should look like as it looses pressure off-axis:
https://www.diyaudio.com/community/threads/adventures-in-cardioid.142691/#post-1808323
btw, so far the discussion has omitted verticals.
Real-world that can be a problem (discontinuity/suck-out) with a design (often past a very small vertical window).
Real-world that can be a problem (discontinuity/suck-out) with a design (often past a very small vertical window).
This ‘muffler’ style is the basis of the Flare Zero system. They use small, highly curved resonant chambers in the surrounding materials to absorb the energy from the rear of the drivers.
https://www.flareaudio.com/pages/zero
This is by no means an endorsement of the sound that comes out of the system, but there are patent numbers at the bottom of the page which might be of interest.
Pretty sure the resistance is much higher with those and as a result is effectively aperiodic (..that's what it sounds like from their description), at least for most of the bandwidth (..though perhaps at very low freq.s there is extra leakage).
Still, cool design (if considerably less directive higher in freq.).
Still, cool design (if considerably less directive higher in freq.).
I think "supercardioidish" would be more accurate 🙂
https://mynewmicrophone.com/the-complete-guide-to-microphone-polar-patterns/#Supercardioid
If the loss in output and different looks are OK then no real reason if a specific pattern is the goal
I like dipole bass a lot myself but my comments were about how something works not what I think is best.Still, I tend to prefer the result of a Dipole here (as adason mentioned) - even with the rear-wave reflecting off of the wall behind the loudspeakers.
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You can skip to the end for the cardioid stuff and come back to the background later or never.
Generally a tilt to the speakers is an attempt to time align the mid and tweeter and give more options in designing a passive crossover.
It may not be obvious but when a waveguide is asymmetric with a narrower vertical dimension the vertical pattern control can be narrower only at higher frequencies. The smaller vertical dimension causes a loss of pattern control at a higher frequency in that plane. This is where you get pattern flip.
https://www.prosoundtraining.com/2010/05/24/understanding-horn-directivity-control/
https://www.prosoundtraining.com/2011/05/23/asymmetric-horn-patterns/
To make a waveguide with narrow vertical directivity to a low frequency results in quite an odd shape.
@fluid ah yeah now i remember reading about this , also not to forget the interference between HF/ML units to add to the complexity ...
The first link was very intersting, thanks again 🙂
So basically, to get some control down there, the waveguide needs to be quite large and probably symmetrical ?
The tilt angle i was more referring to having the driver pointed at a higher point than normal to try and help lower the early reflections to the floor since it is so close to the drivers in a normal setup.
Perhaps having the loudspeaker system higher in the air would help with that also ?
Although probably less WAF friendly lol
The first link was very intersting, thanks again 🙂
So basically, to get some control down there, the waveguide needs to be quite large and probably symmetrical ?
The tilt angle i was more referring to having the driver pointed at a higher point than normal to try and help lower the early reflections to the floor since it is so close to the drivers in a normal setup.
Perhaps having the loudspeaker system higher in the air would help with that also ?
Although probably less WAF friendly lol