Everything you say seems logical to me. What would be your suggestion on how to tackle the problem of good directivity control throughout the spectrum if not by horn and your oppinion on xover frequencies for multiway system ?
I do think that controled directivity should be as low as possible regardless of the >700 theory too. That's why i liked Kimmostos cardioid loudspeakers that much.
You said that you're working on a project of your own. Is it some dipole/wg combination or something else ?
cheers
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I like the idea of a tower of four 15" OB woofers personally with a central MTM section. It's in practical terms the best solution out there.......but not very practical in most rooms. Lol
I never said "unimportant" or "can be ignored", I said that they were not as significant as > 700 Hz and as such one need not weight them strongly in a design. In an ideal world we would have a DI of 12 dB all the way to 200 Hz. Its simply impractical and a bad choice of compromise to try and do so. Read 5thDimensions comments. One should do those things FIRST that make the most difference, but you have to draw the lie somewhere. He was right on the money.
So basically one cannot be a manufacturer and be right at the same time.
You understand that it was never my intention to make loudspeakers. For 30 years I was first and foremost a researcher, but what my research lead to was not available so I had no choice but to build my own speakers. Then others wanted them as well and somehow I became a manufacturer. A role that I have tried to get out from under for a while now.
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Seriously? Read your own website! It can't be that difficult to get out of business. Do just like the banks in the US;o)
I can just stop making speakers, sure, but then the whole technology just dies. That's what I am trying to avoid.
This is not what I said, but your incorrect conclusion could be fact which would indicate that any manufacturer may be right in a good day 😉
Problem is that the 'native reverb' comes from the 'direct' radiating front speakers! What is needed is not multiple 'direct' radiating channels, but also indirect radiating channels.
That's why LEDE/RFZ rooms can be called 'passive surround'. This brings up another point. In a typical living room there is too much absorption to get the effect - so use active/upmixed surround!
The hybrid approach does not satisfy the objection Earl identified to going active. The objection is that one cannot power the speakers with an AVR.
Wished my wife and my boss shared your opinion 🙂
Dipole (LF above transition freq, say 250Hz) + waveguide at HF. The transition from dipole to waveguide can be tackled in different ways/xover frequency:
1. dipole 250-700 + CD waveguide a la Geddes above. Pros: crossover simplicity, low number of drivers - fewer issues to solve. Cons: compression drivers are not everyone's cake, waveguide not trivial to build/engineer (not sure if Dr.Geddes sells it separately).
2. dipole 250 - 4kHz* + waveguided planar tweeter above. Pros: dipole all way up (a subjective argument, I know, but I simply like the disappearing trick of dipoles. To be fair though, I did not hear Dr. Geddes speakers), more uniform DI/power response, no HOMs to fight Cons: lower efficiency, lower directivity in the 1-4 kHz area, complex crossover
*this is typically achieved as a 2-way, meaning one more crossover in this area, which is undesirable. I'm researching an alternative - commented below.
I'm also currently thinking that directivity under 700 Hz might not be so low on the list of desirable features as Dr. Geddes put it - I'd comment on that later.
Simply put, I'm working on a way to achieve dipole-like controlled directivity in a range like 250 - 4kHz, without a crossover in this area. The idea is to use a 2-dimensional dipole array of acoustically small fullrange speakers (some that also have some low end capability) arranged such that their apparent acoustical size decreases as frequency increases. Above that, I would use a planar in a waveguide to match the dipole directivity.
Two vertical 5 unit bessel arrays flanking a central line of two vertical planar tweeters all in dipole configuration.
My main objection is precisely the lack of supporting evidence that the range <700Hz is "not to be weighted strongly". The Griesinger paper does not state that. It only states that the range >700Hz is dramatically more important in the perception of localization/engagement in concert halls. Other than that, it generally states the requirement of having a minimum D/R ratio - not in a specific range of frequencies.
Griesinger talks about concert halls and his definition of a "small room" seems to be "a small concert hall with less than a few hundred seats", which can hardly be assimilated to a typical living room, where I would expect the D/R under 700Hz in the first 100ms to be significantly lower (and thus detrimental) than in a hall, because the size of the room would make much more reflections to arrive in the first 100ms. But I admit I have no data to support that. Maybe there is something out there.
Obviously, this all does not necessarily demonstrates that more directivity < 700Hz is important. it just that it does not support the opposite.
AFAIK, many higher-end AVRs have parametric EQs. Pretty much what you need for a hybrid approach.
While Greisinger does not deal with the loudspeaker problem in small rooms directly his work is strong support for my opinion. Especially since there is no support for the contrary and we know that any need for directivity has to completely disappear in the modal region. It is only logical that its importance has to begin decreasing somewhere.
We really don't know. For example I know that bass radiator can be large and directive in the modal region. It must be large and directive enough for me as pure stereo if room acoustics is not capable to equalize enough clarity/resolution spectrum from low to high frequencies.
Remember that your subjective preference (and product) is not globally accepted and only truth.
But facts are facts.
In the modal region arbitrary wave propagation is not possible. The waves must move in directions prescribed by the mode(s). Thus any talk of "directivity" at modal frequencies is absurd. It can't happen. Model a room at Lfs and see if you can find any "directivity". It is simply not a concept that is applicable in the modal domain.
In the modal region arbitrary wave propagation is not possible. The waves must move in directions prescribed by the mode(s). Thus any talk of "directivity" at modal frequencies is absurd. It can't happen. Model a room at Lfs and see if you can find any "directivity". It is simply not a concept that is applicable in the modal domain.
We do know that the higher frequencies are what we use to define the sound stage accurately (or at least pre dominate). We do know that having directivity at low frequencies is pointless.
There is going to be some curve that sits at zero for the bass and gradually increases up to 100% by the time you get to a suitably high frequency and then it will most likely tail off a bit in the final octave.
Where this curve sits isn't going to be completely known but it is going to be dependent on the room, so the exact nature of it might not be critical.
If ones room is modal up to around 200Hz and directionality/directivity isn't going to do anything down that low, then the curve is only going to transition above zero when you go higher up in frequency. Clearly this is going to be a gradual, process, they all are, so it's clear that the region of least importance (for having controlled directivity) is going to be the region just above the modal region. Or are you trying to say that this isn't the case?
Yes...maybe. The only thing in a room that equalizes and has clarity/spectrun resolution from 20 to 20000 Hz is the (are the ...) ear
Picowallspeaker - except that the ear, as a sensor, is not really very good. Were it not for our brain the ear alone would be quite poor. But it is precisely the brains influence that is so problematic, because it can never be without bias. A measurement microphone, the ear is not.
5tth Element - how did you get so good at this stuff! You always have it right on.
5tth Element - how did you get so good at this stuff! You always have it right on.
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