Where did I state that ? My point was only that a direct radiator + waveguide as a system is also narrowing (until the waveguide takes over).
That being said: while a direct radiator is inherently narrowing per se (and I do understand why 😉), it can be made CD in a useful range by using it in a dipole. Optionally, that useful CD range can be (moderately) extended beyond the dipole peak by carefully designing the baffle+driver apparent size such that driver would start narrowing before the dipole peak is reached. I am working on such a design currently and hope I'll post some measurements soon.
Now there's the other thing: you want more directivity than the dipole can do at HF ? The yes, only a waveguide will help.
So.. when are you going to give it a try to that low midrange dipole/cardioid + your great HF waveguide 🙂
What's the compromise, apart from efficiency/power ?
I am sure you have solid reasons to state that, but I am a bit confused about "really necessary" and "does not matter so much". In Germany, where I currently live, they say there is no such thing as "a little pregnant" 🙂
It's certainly quite a bit unintuitive why 700Hz - smack in the lower midrange - should not matter. You mentioned a paper of Griesinger explaining why, could you point me to the exact reference ? I've found a page of his, but sure which one it is, might be this, did not read yet: http://www.davidgriesinger.com/direct_sound.doc
No speaker is perfect. Apart from efficiency, which would be your top 3 issues with dipoles ?
Top threes........hmmm. Dipoles? Inefficient, placement dependant and limited low frequency extension. For a dipole system to work for me, I'd need a dedicated room just for the speakers so I can place them far out into the room and still have space for the subs for the last octave.
"So.. when are you going to give it a try to that low midrange dipole/cardioid + your great HF waveguide
"
Earl andbzfcocon, do you know this cardioid bass+horn speaker by kimmosto?
KS-1804 MkII DIY Loudspeakers Kimmo Saunisto
Earl andbzfcocon, do you know this cardioid bass+horn speaker by kimmosto?
KS-1804 MkII DIY Loudspeakers Kimmo Saunisto
An externally hosted image should be here but it was not working when we last tested it.
That's interesting. I have similar observations and prefer a healthy combination of absorption/diffusion with normal objects in the room like soft furniture, carpets, books and stuff. The well treated rooms do have a tendency to mimic "headphones on a stick" somewhat and the stuffed concrete rooms will go more bass node heavy.
I like to think that the reflections, if the speakers off axis behavior is intact and linear, help the ears to understand the sounds presented to them in the room. It's easier to do the math with more quality information for the ears.
That's the main reason I like waveguides matching the dispersion and phase of the tweeter to the midrange. When you do this the need for a BBC-dip or presence recess is reduced to almost zero because the energy in the 3-7KHz region does not make your ears bleed from baby-screams no matter what volume you play the music. 🙂 It must have something to do with the information of the off axis sound is more intact and does not strain the ears with confusing information or noisy sound energy.
I've been trying to follow this thread. Unfortunately, most of it is still above my head. What I would like to have clarified is: Where is the waveguide supposed to kick in, at what frequency, is it from approx. 7000 Hz and up, or what? I might try one in a later system.
From 700Hz and up to at least 7000Hz. I would like it to kick in from 400Hz but that isn't doable without 2" throat waveguide and aditional tweeter.
Ideally a speaker should have constant directivity down to schroeder. A typical waveguide speaker only offers directivity down to 1200-800 Hz, which is in my opinion a significant compromise.
It's not only about imaging but frequency response. A speaker with constant Di low in frequency yields a flatter response and who doesn't want that? Plus the reflected energy get's less colored. Thus, saying that controlled directicity isn't important below 700 Hz makes little sense.
Whether the directivity should be wide or narrow depends on the usage, room and preference. There's no reason to be bombastic about what the ideal Q is. It depends. Either way, the vertical reflections should be avoided.
The speakers that can do this is a huge horn (waveguide is a type of horn), Don Keele's CBT, dipole or cardioid. I guess you could add omnis too (like MBL which is very flat horizontally at a certain height) but for small rooms they trigger the room way too much IMO.
Oh by the way, late arriving reflections can also be detrimental which several studies support. They are simply less detrimental then early ones, but should still be treated for a great result. Preferable they should be diffused.
The idea that everything later then 10 ms is beneficial and good is wrong. Not all reflections after 10 ms adds spaciousness either, that depends on the angle of incidence and time they arrive.
It's not only about imaging but frequency response. A speaker with constant Di low in frequency yields a flatter response and who doesn't want that? Plus the reflected energy get's less colored. Thus, saying that controlled directicity isn't important below 700 Hz makes little sense.
Whether the directivity should be wide or narrow depends on the usage, room and preference. There's no reason to be bombastic about what the ideal Q is. It depends. Either way, the vertical reflections should be avoided.
The speakers that can do this is a huge horn (waveguide is a type of horn), Don Keele's CBT, dipole or cardioid. I guess you could add omnis too (like MBL which is very flat horizontally at a certain height) but for small rooms they trigger the room way too much IMO.
Oh by the way, late arriving reflections can also be detrimental which several studies support. They are simply less detrimental then early ones, but should still be treated for a great result. Preferable they should be diffused.
The idea that everything later then 10 ms is beneficial and good is wrong. Not all reflections after 10 ms adds spaciousness either, that depends on the angle of incidence and time they arrive.
For Griesinger try http://www.davidgriesinger.com/ica2010/paper1.doc
Dipoles, like piston sources are only constant directivity at very low frequencies, i.e. such that the wavelength is much greater than the source size. So dipoles do not really have any influence on the directivity where it matters, above 700 Hz. Below that they do help the directivity, but as I say, that is not all that important.
I have built dipoles systems. Dipoles < 700 Hz and waveguides above. They require active crossovers to correct the frequency response which is problem #1 (not everyone is willing to go active). They have very poor efficiency, which is problem #2. I am not sure that there is a third major issue, but the first two were enough for me to not pursue them any further.
Why did you end up with different conclusions?
It looks like Toole always seek for large directivity.
For example JBL implementation of the OS waveguide (EOS, as found in the LSR series) where always > 100°
I looks like they are now using (managed) diffraction to achieve smooth directivity behavior in the M2 and LSR308 loudspeakers.
If your studies led you to different conclusions then you should accept that other solutions/paths exist.
The waveguide should come in as low as practicable. But the size implication make 700-1000 Hz the lowest reasonable limit. Below that the waveguide just gets too big to deal with effectively. I have trouble making one that is 18" and that just gets down to 700-800 Hz. Bigger is just not feasible in a reasonable design.
So you don't buy Griesingers claim that 700 and above is the "key" frequency range?
You are nit-picking about early reflections. Only the most extreme cases of > 20 ms reflections would be received as bad. And yes, lateral reflections are best for spaciousness, which is why you should not use absorption on the walls. I do absorb the first floor reflection and diffuse the first ceiling reflection, but mostly we are discussing lateral reflections as they are by far the most important (again see Griesinger).
I believe that the discrepancy comes from the nature of the tests that were done. Toole used a given room that is built to an international standard (fairly well damped) and he uses preference as a metric. Imaging is never even mentioned in his criteria.
My rooms are custom built to yield very high reverberation in which the imaging is then controlled via the loudspeakers directivity. My approach yields good imaging and spaciousness. Toole's approach optimizes spaciousness but does so at the sake of imaging.
Yes, these are different goals and different goals will yield different solutions. I have never denied that. I have always been clear about my goals.
There's much that could have been said, but I've grew tired of debates and where I feel people are mainly defending their beliefs.
However, there's one thing here I want to ask/comment. You say you want to avoid absorption on side walls in order to have spaciousness. But on the other hand you say you design speakers to avoid side wall reflections. That's seems quite contradictional? Are you saying you actually desire reflections below the waveguide and only want to avoid them where the waveguide operates?
Early reflections are bad, thats what everyone says.
What are the read I should read that claims otherwise. I'm relaly interested. I'm in the process to do all my absorption panels, and they have resulted so far in major improvement. I have to admit that its much more adding the big huge bass traps that resulted in huge improvement, where as treating the side walls early reflection was more subtle....
I'm stunt by your claims because it goes against everybody in the acoustic world will say about how to treat a room.
One of the most major problems are early reflection like the side walls.
But you claim that you want those reflection to add spacisouness. Dont you think there a lot of detrimental effect of those early reflection, like lobing effects, lack of focus, imaging problem because of early reflections...
I have never seen anywhere someone adding early reflection absorption panels then removing them because it lacked spacisousness.
I, however, have seen many people complain that their room was too dead after treating too much their room highs with not proper low bass control because of bass traps with insufficient low absorption capabilities. Therefore absorbing too mich high energy and not enough bass, creating a imbalance.
Also, is there a huge difference between a studio and a audiophile room in how you want to treat your room? Most guys in the studio industry will say that you cnanot have too much bass traps in a small room, as long as you make sure too add a membrane on top of your bass traps that will help reflect some highs into the room, making sure too not make your room too dead is definitely important in my experience. Theres nothing more incomfortable then a room too dead....
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I am not in the least bit bothered by that fact. I have always gone against the prevailing views of the masses. But curiously enough I am almost in complete agreement with other experts like Griesinger and Toole (early reflection differences noted).
Which if you read my writings you will know that I solve this with the speakers, not the room.
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