Keyser - I don't think that I would agree with the Schroeder frequency shifting as this frequency is dictated by the room. And it is highly unlikely that there is going to be any directivity in the modal region in a small room anyways. Auditoriums perhaps, but nothing in a home.
To me this speaker is all about "design by eye". There is nothing in it that looks like a good acoustical idea to me. Just "eye candy", plain and simple. There is absolutely no horizontal directivity control at all, so any claims about directivity being a factor for sound quality are incorrect. Minimizing the room interaction ("decoupling") means high horizontal DI, otherwise you get a maximum of room interaction (most of what we hear in a room is in the horizontal plane, not the vertical.) Those speakers have about 0 dB DI at almost all frequencies, hence there will be virtually no "decoupling" of the speaker and the room.
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It is as bad as earlier because calculates phase of diffracted wave as inverted and magnitude as full regardless of direction where the wave is heading. Image you attached shows very clearly that the result is wrong.
Thank you for your insight, humbly could you upload graphs for their listening window as a stereo pair with and without wall treatment
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I don't quite understand the question. Do you mean polar plots for line arrays? You just have to look at them to know that in the horizontal plane they will be very wide and not very constant. Not everything need to be measured to know how it will work. Line arrays are a classic example - we know how they work, there is no mystery. I have posted what I think is the most complete reference to various loudspeakers polar response, I just never did a line array. I'd welcome someone generating that data so I could include it. That would be most informative (although I think that most would find it disappointing.)
Wall treatments as a solution for too wide a polar response are known to be less than ideal.
Wall treatments as a solution for too wide a polar response are known to be less than ideal.
At times they are more ideal than a speaker (with a bigger foot print) that isn't allowed into a room by the other half 😉.
It took a huge panel, 3" thick with a bit of air behind it, using a combination of wool felt and fiberglass insulation but I'm not complaining. Documented results in my thread by the way.
Sorry, there isn't any practical way for me to get polar information.
Agree on the amount of absorption required and how it is not very practical.
It is very unfortunate that we don;t have any comparable polar patterns for line arrays. I'd love to see them for the OP's line arrays. I don't think they would look as good as is expected. That design would have lots of diffraction.
It is very unfortunate that we don;t have any comparable polar patterns for line arrays. I'd love to see them for the OP's line arrays. I don't think they would look as good as is expected. That design would have lots of diffraction.
The luck I had is they are hidden from sight (except for one, disguised as a poster) behind curtains, but by no means would I claim getting studio like performance from my room. I'm still far ahead on many projects that I've seen on here. At least I'm looking at what a room adds 😉. Most people just place their precious meticulously designed speaker in a room and call it a day. 🙂 And we are asked to believe their claims due to using top dollar drivers or crossover components.
I certainly agree to your concerns about that strange contraption made by McIntosh. There's not much engineering going on there that makes any sense to me. No marketing babble is going to make up for that.
I certainly agree to your concerns about that strange contraption made by McIntosh. There's not much engineering going on there that makes any sense to me. No marketing babble is going to make up for that.
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You are all correct the speaker at all frequencies is not decoupled from the room in the horizontal plane. The speaker displays a cylindrical dispersion upto 600Hz where it goes into spherical dispersion. The mtm or other configurations minimize the lobbing in the crossover frequencies. I still cannot account for the midbass toe in without measuring the actual speaker, but it maybe also to manage lobbing. Lets wait for the stereophile review.
Dr Geddes has the NS15 as one of his works of art and brings into question the suitability of line arrays in venues with four walls. Line arrays have a 3dB loss with doubling of distance as opposed to spherical dispersion which decays at 6dB per doubling of distance.
A room resonates below the Schroeder frequency and reflects above it. Horns and wave guides play a crucial role above this frequency but work by others including Linkwitz (will have to re read the paper) show that the brain can up to a certain degree post process what we finally hear. Below the Schroeder frequency the room is resonant, Linkwitz prefers dipole as it excites fewer modes. Several bass reflex woofers driven by a GNFB amplifier such as the 1DIFFQC also do well in such an environment as the do hard work to manage the resonance.
Feel free to point out any misunderstandings. Looking forward to your glass works Dr Geddes.
Dr Geddes has the NS15 as one of his works of art and brings into question the suitability of line arrays in venues with four walls. Line arrays have a 3dB loss with doubling of distance as opposed to spherical dispersion which decays at 6dB per doubling of distance.
A room resonates below the Schroeder frequency and reflects above it. Horns and wave guides play a crucial role above this frequency but work by others including Linkwitz (will have to re read the paper) show that the brain can up to a certain degree post process what we finally hear. Below the Schroeder frequency the room is resonant, Linkwitz prefers dipole as it excites fewer modes. Several bass reflex woofers driven by a GNFB amplifier such as the 1DIFFQC also do well in such an environment as the do hard work to manage the resonance.
Feel free to point out any misunderstandings. Looking forward to your glass works Dr Geddes.
How could a line array ever have spherical dispersion?
This is true in the near field of a line source, but I have never understood why this matters.
This was shown to not be correct. The same numbers of modes get excited just in different ways. A paper that I did some time ago showed that at any given location in a room a monopole or a dipole could be better or worse than the other, but no source type was always better or always worse - it all depends. But the main point is that for single sources neither source type had very good response - it takes multiple sources to smooth the response. And I have always said that if you have multiple LF sources then it matters not what "type" they are (except that closed box subs tend to be the smallest option.) Once the LFs are EQ'd then they all work just as well.
I just posted my completed glass work in detail this morning. Enjoy. 🙂
You are right Earl. Technically what I said was wrong, the Schroeder frequency is dictated by the room (although it's not very precisely defined by it). In practice, directivity of the source and the position of the source and observer/microphone in the room affect where the apparent transition from resonant room to reflective room happens.
I'd say directivity is a property of the speaker. Dipoles and cardioids have directivity in the modal range of small rooms. They interact with a room differently, but one not necessarily more favorably than the other.
I'd say dipoles are better than cardioid in a small room due to less early reflections from the side walls. However in a small room cardioids can be placed closer to the front wall, it seems to me this is their only advantage here
Directivity is a property of the speaker, until you put it in a room, then below Schroeder, directivity as a concept must be altered. Let me give you an example:
Take a source, any source, in a room playing a tone at a strong resonance mode. This mode has a pattern, a specific way that the sound wave travels around the room. It is not arbitrary, this wave pattern is precisely defined in terms of its direction of travel, no other directions are allowed. So how can we talk about a sources directivity when only a single wave direction away from the source is allowed. This is what defines the Schroeder frequency: its when there are enough modes to allow for arbitrary wave propagation away from the source, and directivity becomes a viable concept.
Think of this in another way. Lets say I have a cardioid source with its assumed directivity. As I rotate it the sound waves in the room at the mode being excited do not change direction at all. They still travel in exactly the same directions regardless of the direction the speaker is pointing. They may or may not change amplitude, but this is probably not the same pattern as this cardioid would show in a free field.
I just think that talking about directivity of a source in the modal region of a small room must be done carefully because the concepts don't hold up very well.
Can a DI figure be found for a floor to ceiling line source (or other non-point source) so as to make a comparison with a point source? (eg in a room considering some walls but not others)
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One could not use the theoretical definition of DI for a line source because it requires a sphere surrounding the source and that would be a big sphere. But it is certainly possible to calculate a horizontal DI using only the horizontal polar pattern. I do that in my software. To me its the horizontal DI that is the most important.
still it's the floor reflection that is the worst, followed by the ceiling (for conventional speakers):
http://www.diyaudio.com/forums/mult...istortion-speaker-drivers-71.html#post5242177 (the Archimedes research project)
I understand that, but the vertical reflections should be eliminated by the room. One does not want strong absorption on the side walls because lateral reflections yield spaciousness, but vertical ones have no positive attributes. Once they are eliminated then only the horizontal DI matters.
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