Dioples in an acoustically small room act as multiple monopole sources at low frequency. The dipole pattern is a far field result. But that doesn't mean that rotating them 90 degrees won't significantly reduce bass for a listener seated centered, left to right.
Here is a simulation of a symmetric stereo dipole set up: top listener centered, dipoles positioned normally and rotated; bottom, listener 0.5 M offset to side, dipoles rotated.
I have observed this result with dipole woofers set up in my room. Rotate he dipoles and the bass goes away at the listening position.
Here is a simulation of a symmetric stereo dipole set up: top listener centered, dipoles positioned normally and rotated; bottom, listener 0.5 M offset to side, dipoles rotated.
An externally hosted image should be here but it was not working when we last tested it.
I have observed this result with dipole woofers set up in my room. Rotate he dipoles and the bass goes away at the listening position.
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John,
Does this simulation take into account all walls? What happens when the distance to the side walls is varied? What happens when one dipole is reversed?
Does this simulation take into account all walls? What happens when the distance to the side walls is varied? What happens when one dipole is reversed?
It is a rectangular room simulator. It includes all walls, floor and ceiling. Obviously, I can not run every case. Generally distance from side walls should not be a significant factor with normal orientation. Rotated it will have a significant effect. I'll have to take a look at reversing one dipole. I presume you mean with woofers rotated.
ok, fair enough. Please then provide a way to calculate when and where a dipole stops being a dipole.
I don't want to put words in Doc Geddes mouth, but doubt that he (or other strict objectivists) do either. Neither do I, although I'd take it if I could get it.
Earl Geddes has achieved the results he desires using a strictly technical, objective approach. The results are good - I've heard them. But I believe that some of us achieve results just as good with other approaches. Use the tools you have.
I do find that the more technically accurate the subjective results, the better it sounds - up to a point. But there comes a point where the technical goals are determined by what sounds right or accurate. Otherwise, what's the point?
Also, let us not forget that the vast majority of listeners don't give a hoot whether it's accurate or not - they just want it to sound good. Usually, that means a lot of bass. 😉
I wish I could! I also wish there was a simple way of running FEM/BEM for my room and speakers. We're not there yet.
not to worry! 🙂
But are we then safe assuming that the longest room dimension is still a right way to assess the limit?
But are we then safe assuming that the longest room dimension is still a right way to assess the limit?
Somo body please define ACCURATE.
When designing a speaker any number of design objectives can be specified and when the speaker is completed it can be measured against those objectives and a level of accuracy in meeting those objectives can be defined by looking at the deviation from the reference the objectives define. But with a souind field produced in your room, how do you define accuracy? There is no reference. You most likely don't even have any idea of what the recordign engineer though it should sound like, let alone what the actualy perfromance sounded like. In your room it either sound the way you like it or it doesn't. There is no measure of accuracy because there is no reference to compare it to.
When designing a speaker any number of design objectives can be specified and when the speaker is completed it can be measured against those objectives and a level of accuracy in meeting those objectives can be defined by looking at the deviation from the reference the objectives define. But with a souind field produced in your room, how do you define accuracy? There is no reference. You most likely don't even have any idea of what the recordign engineer though it should sound like, let alone what the actualy perfromance sounded like. In your room it either sound the way you like it or it doesn't. There is no measure of accuracy because there is no reference to compare it to.
I'll reiterate my hobby horse- when it comes to transducers in a room, quo veritas?
That's very different, BTW, than saying that one's models and implementations needn't be validated by controlled listening tests, something that all of the speaker designers I mentioned earlier share (I'm speaking of commercial and research work, not hobbyists, though controlled listening is a great thing to do if you can pull it off).
"Objectivist" is a terribly inaccurate word- proper listening tests objectively measure subjective judgment.
edit- xposted with John.
The reference exists, it is the studio acoustics where the recording was created. If studios would adhere to strict standards, sound reproduction would be as easy as calibrating a TV screen.
Constant directivity (CD) does this. It has flat power and flat response along any axis. No direct radiating tweeter does this, so adding a second one might seem to help, except that it has the same problem as the first one so it really doesn't as John said.
I have always thought that SL claim that CD was desirable - except that his speakers aren't CD.
you see.. talking of objectivity.. SL's speakers do have limits to CD indeed, so do yours.. a subjective comment then 🙂
Will there be a cardioidified Geddes speaker so their directivity becomes more constant? 🙂
Sorry, I want the Gebouw, and the Boston, and Vienna in my room. 😀
Diversity is the best of humanity.
I know what you want but you probably have to accept what equipment and the people operating that equipment offer you.
+1