Me and Dave Griesinger - I am satsified with that company. I'll stick with my opinion.
Where does Griesinger say "Skip all the directivity nonsense"? He is fixated on early reflections (> 700 Hz) and those are controlled by directivity.
Markus - we must have read different papers. Does he or does he not exclude frequecies < 700 Hz in his calculation of localization?
This is correct and posses some issues, but I don't see them as significant. The premise of what he says about the phases of the harmonics is easily transfered to the small room reproduction situation with profound implications. This realization and his explaination of why this happens have had a profound effect on my thinking and I am someone who has studied this area in some depth. If Griesinger's claims do not completly disrupt your beliefs then you don't understand them. There is nothing like them anywhere else that I have read.
Griesingers approach is also supported by the paper that Rudolf posted (don't have that link on hand) on the ears ability to analyze modulation. This paper is also quite good. It show that the ear is very adapt at recognizing modulations < 10 Hz. This is strong support for my claim that thermal modulation of a reproduced soundis a significant factor. This is because those modulations will be strongest in the < 10 Hz area - the modulations will be greatest at exactly the place where our hearing is most accute. Not a coincidence me thinks.
Last edited:
My reference speakers control directivity down to 900hz. In the past I've used speakers that lost directivity control at a higher frequency.
Based on my own listening experience, I think 900hz is more than enough, and if I had to do it again, I'd likely go with a waveguide in the range of 10-12". (Cutoff of between 1350 and 1125hz.)
As in all engineering endeavors, there's a lot of tradeoffs involved here. It's not a simple case of bigger is better. For instance:
1) larger waveguide necessititates a larger center-to-center distance. Larger center-to-center spacing means you need to sit further back from the speaker to get the best integration. So a large waveguide could literally mean that you need to get a bigger home. This is the main reason my Summas are sitting in my garage. I went from a 2800' home to a 1500' home, and they simply don't fit in my living room. I *do* intend to buy a new home soon. But these speakers *really* need a big room, or at least a room that's long on one axis. I'm looking forward to running the Summas again soon, but it's very frustrating to have to buy a giant house to accommodate your loudspeakers.
2) These speakers are REALLY big. I could easily squeeze an Abbey or Nathan in nearly any room. So it's not just a question of getting far enough from the speaker, it's also a question of decor.
Patrick,
I completely understand what you are saying and if you look at my fuzzy avatar you will see a set of small waveguides for this very reason. The center to center distances are less than 1/4 wavelength apart for this simple reason of the blending of the sound sources in a minimum distance. All the waveguides use similar angular flares to again keep the polar responses as similar as possible. I understand your single point source designs and this is an improvement in regards to having no vertical blending needed. Doesn't mean your device is perfect either as you have other issues to deal with in the throat itself.
But at the same time are we to just forget about diffraction affects and edge diffraction below 700hz? That would sure simplify enclosure design if that be the case.......
I completely understand what you are saying and if you look at my fuzzy avatar you will see a set of small waveguides for this very reason. The center to center distances are less than 1/4 wavelength apart for this simple reason of the blending of the sound sources in a minimum distance. All the waveguides use similar angular flares to again keep the polar responses as similar as possible. I understand your single point source designs and this is an improvement in regards to having no vertical blending needed. Doesn't mean your device is perfect either as you have other issues to deal with in the throat itself.
But at the same time are we to just forget about diffraction affects and edge diffraction below 700hz? That would sure simplify enclosure design if that be the case.......
What do these subsonic modulations sound like?? Or should I ask how do they change the waveform so that they are audible??
Rob
They don't change the waveform per se they change the envelope of the waveform. But the envelope is a crucial part of what the ear uses to prcess imaging and the like. I am suggesting that this effect is what we call "dynamics" - some speakers do better than others.
Yes, he did, in the first paper in his three part series on "envelopment". You need to read those three papers. The one that you read is a different paper than what I am talking about, so we did read different papers.
Thats a slightly different issue than directivity, which is about reflections off of the walls. I would tend to agree that the attention to the diffraction below 700 Hz should be considered, but in reality it is. It's not like you can have high diffraction at 1 kHz and low diffraction < 700 Hz. Lower the difraction at high freqs simultaneously lowers it at lower freqs. Do the best that you can and that is the best that you can do.
But what always amazes me is how people neglect the diffraction from the room close by the speakers. It makes no sense to place a low diffraction speaker next to a high diffraction stero cabinet, but yet I see this done all the time. The entire space arround the speaker must be low diffraction as well as the speaker itself.
Do you have a source for this claim, or is it in the Griesinger papers?
I appreciate your comments. But your pluto clones are not how the majority listens: nearfield, away from reflecting surfaces, direct sound is dominant, and little volume capability. This is one way of solving the problem or raising the direct to reflected ratio. For others, who listen in the farfield, using speakers that need to play louder and are therefore larger, directivity is needed.