Here are various measurement techniques used by Linkwitz in his monopole/dipole comparison. At least pictures 20./21. are worth seeing. Looks like avoiding 2 of 3 axial room modes does the primary job in achieving more articulate bass transient.
It would be interesting to see similar research where dipoles are compared with, lets say, 60+ monopole subs placed all over the room.
http://www.linkwitzlab.com/AES'98/aes-98.htm
Dipoles do not excite fewer modes than monopoles, they excite different modes. And at any rate minimizing the modal excitation does not lead to a smoother response, while maximizing it does. For each dipole preferred example one can create a monopole preferred example. It makes no sense to compare a dipole and a monopole in the same configuration because no one would do that. You have to compare what a dipole can do when optimally setup with what a monopole can do and then you come away with a different story. Dipoles have certain location advantages but extremely poor LF response. At ever lower frequencies the monopole beats the dipole, but at higher frequencies the dipole wins out. You have to pick your tradeoffs.
Did you intend to say maximizing modal distribution leads to a smoother response?
Maximizing the number of modes being excited in any given frequency band does tend to smooth out the response, especially when there is significant damping. Cancelling modes leaves the modal density sparser and hence rougher (because you can't cancel them all). Large rooms have smoother LF response because they have more modes not less.
Sometimes in a small room there can be a singular lone dominate mode which is best taken care of by EQ or a tuned absorber at that frequency, but good design can usually avoid such pitfalls.
Sometimes in a small room there can be a singular lone dominate mode which is best taken care of by EQ or a tuned absorber at that frequency, but good design can usually avoid such pitfalls.
With appropriate correction and multiple large drivers in small room it's possible to go with dipole as low as 20Hz and still get it "loud and clean enough". In my experience it sounded great while not being very practical in terms of applied energy and wasted room space. Perhaps more reasonable approach would be dipole midbass (80-300Hz) combined with monopole or bipole subbass (20-80Hz) to get the best of both worlds. I don't expect to feel nice bass transient below 80Hz, but above that, once I have heard it from dipole I haven't heard any better from monopole yet.
You should try a cardioid for the upper bass and mids. Because cardioids are unidirectional, reflections are less of an issue. In my experience a cardioid has the subjective speed of a dipole and the punch of a box. Also, timbre is affected by the room less.
At lower frequencies cardioids have the theoretical advantage that they are a mix of a velocity source and a pressure source, so they excite more modes but they couple to them less effectively. This should help smoothen the frequency response. Not sure if it actually sounds better in practice, but a full-range cardioid is being worked on at the moment 😀 .
At lower frequencies cardioids have the theoretical advantage that they are a mix of a velocity source and a pressure source, so they excite more modes but they couple to them less effectively. This should help smoothen the frequency response. Not sure if it actually sounds better in practice, but a full-range cardioid is being worked on at the moment 😀 .
This point gets missed too often, and appears to be the main (only?) issue with model region in small rooms. IF you have the option to only use one source (this itself is sub-optimal) then on average the cardioid will have the best behaved response. Just repeating what you said.
In the midrange a cardioid box speaker derives its directivity from both phase cancellation and addition of the rear-wave and driver directivity. In the midrange the on-axis efficiency can actually be (slightly) higher than with a similarly sized closed box. This happens when the delayed rear-wave adds in phase with the direct output of the driver.
However, at low frequencies efficiency of a cardioid is low. I don't think there is a way around it, because the directivity is achieved solely by means of cancellation. I think you'll lose a little less than the 6 dB/oct a dipole loses to lower frquencies, because of loss in the resistive damping material. Soon I'll be doing some experiments and measurements outside. Waiting for the sun.
However, at low frequencies efficiency of a cardioid is low. I don't think there is a way around it, because the directivity is achieved solely by means of cancellation. I think you'll lose a little less than the 6 dB/oct a dipole loses to lower frquencies, because of loss in the resistive damping material. Soon I'll be doing some experiments and measurements outside. Waiting for the sun.
If you want to do some work on the computer before hauling stuff outside, The programmer at work made several ap’s which can be used to design both end fire and cardioids arrays.
If you have an iphone, the ap’s to do that design work (and some others) are here (and free).
http://gpa.hms2k.cl/
If you don’t have an iphone or ipad, there is a PC program you can also use to design these called ddt.
It is more powerful and used in large system design and so, may require watching a couple of the how to video’s.
Danley Digital Tools | Danley Sound Labs, Inc.
DDT training videos | Danley Sound Labs, Inc.
Best,
Tom
Tom
You should check out my polar software. I believe that it is the best on the planet. Its on my website (but may not be working right now due to some web updates in progress). You software looks pretty weak. Maybe I could help you out.
You should check out my polar software. I believe that it is the best on the planet. Its on my website (but may not be working right now due to some web updates in progress). You software looks pretty weak. Maybe I could help you out.
Keyser,
I found midrange cardioid polar response being too wide for small, reflective room. Of course I'm generalizing here, as it depends on particular design very much. So what average dispersion width you're meaning regarding cardioid midrange?
Dipole has competitive advantage for keeping dispersion narrow enough to avoid side wall reflections with only issue being rear radiation that asks for diffusive panels behind the speakers.
For medium-sized rooms and where wider coverage is needed wider polar response seems appropriate and cardioid is one and simple way to achieve it.
Rgds,
Markus - they are different directivities - or doesn't that matter? The dipole is narrower in the front, but has that problematic rear radiation and terribly low efficiency at LFs. So if directivity doesn't matter then why not just use a monopole?
^
Exactly my question. "What do we hear?" The answer to this question should dictate implementation. For the last 80 years we did it the other way around.
Exactly my question. "What do we hear?" The answer to this question should dictate implementation. For the last 80 years we did it the other way around.
So you plan to wait until all the answers are in before you do anything? For me, directivity at low frequencies is not a critical issue. Certainly in the modal range it doesn't even make sense, but even above that I have my doubts. But then again, my position is just based on what we know, which is not absolutely comprehensive.
And yet we have reports that there is a perceptual difference. What I'm interested in is what is causing it.
Markus, what is your question exactly?
Just to state the obvious, differences in perceived sound have to be attributable to reflections. That means that differences in sound will be caused by loudspeaker directivity, the room and placement of the speakers in the room. I guess it's difficult to isolate one aspect and assess the role it plays. I'll try it anyway and tell you how I perceive the sound of closed dipoles, closed boxes and cardioids in the low mids and upper bass.
My subjective experience with dipoles, cardioids and boxed speakers used in the low mids and upper bass is that dipoles sound lush and fast, but not very punchy. Boxed speakers in comparison sound more powerful, but also somewhat lumpy and they are more prone to cause coloration (effected by baffle-step perhaps?). To my ears cardioids sound as fast as dipoles, but with more punch and perhaps it's also easier to hear low level details.
Unfortunately these comments are based on uncontrolled listening tests, done in various rooms and with very different setups. I have done measurements on several of these systems and I believe that the cardioid suffers least from peaks and dips in the response. However, I may be biased.
We need more controlled listening tests and measurements that directly compare otherwise similar speaker systems.
Just to state the obvious, differences in perceived sound have to be attributable to reflections. That means that differences in sound will be caused by loudspeaker directivity, the room and placement of the speakers in the room. I guess it's difficult to isolate one aspect and assess the role it plays. I'll try it anyway and tell you how I perceive the sound of closed dipoles, closed boxes and cardioids in the low mids and upper bass.
My subjective experience with dipoles, cardioids and boxed speakers used in the low mids and upper bass is that dipoles sound lush and fast, but not very punchy. Boxed speakers in comparison sound more powerful, but also somewhat lumpy and they are more prone to cause coloration (effected by baffle-step perhaps?). To my ears cardioids sound as fast as dipoles, but with more punch and perhaps it's also easier to hear low level details.
Unfortunately these comments are based on uncontrolled listening tests, done in various rooms and with very different setups. I have done measurements on several of these systems and I believe that the cardioid suffers least from peaks and dips in the response. However, I may be biased.
We need more controlled listening tests and measurements that directly compare otherwise similar speaker systems.
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^
From tests we know that humans can localize sounds down to at least 80Hz. Now we put the source into a room. What does that tell our hearing? "Small room"? Is it important for our hearing to aurally recognize "small room" in order to hear through it? How does it affect perception of stereo which means listening in an interference field that relies on interaural phase differences that are caused by amplitude differences?
From tests we know that humans can localize sounds down to at least 80Hz. Now we put the source into a room. What does that tell our hearing? "Small room"? Is it important for our hearing to aurally recognize "small room" in order to hear through it? How does it affect perception of stereo which means listening in an interference field that relies on interaural phase differences that are caused by amplitude differences?
Keyser;
May the perceived better punch of cardioid midbass compared to dipole be due to increased sensitivity? They are both open baffles? (Ubaffle cardioid?)
May the perceived better punch of cardioid midbass compared to dipole be due to increased sensitivity? They are both open baffles? (Ubaffle cardioid?)
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