It takes four satellites if you are not assuming that the located position is on the reference sphere of the earth -- i.e., if nonzero altitude relative to the reference sphere is a possibility. Also, it is called trilateration.
gedlee said:
Fair enough, but what if you were designing a surround system only for music listening, not film? Presumably you would do something closer to Toole's recommendation and use directional surrounds. Would you choose CD speakers similar (or identical) to your waveguide mains, or something different? How would you orient the axes? Or are these just not interesting questions for you?
gedlee said:
Dr. Geddes,
Thank you for confirming my previous post about the high frequency behavior of the Oblate Spheroid. I found it very interesting you stated that the power response can continue to be flat, while the axial response can still fall some. I guess I incorrectly assumed that axial response followed the power response more closely.
I too have found that a slightly falling high frequency response more pleasing to the ear. A speaker that is flat to 18KHz – 20KHz sound a bit too hot for me.
I also understand that we will not find a compression driver with a raising response. Its high frequency response must fall due to the reasons you already touched on. However, I was thinking about a cone driver. I can and have built some cone driven mid-range horns with phase plugs that had a raising power response. Out of curiosity I tried to see if I could model the Oblate Spheroid to do the same. After many different woofers and waveguide sizes I think I found what I was looking for. See below graphic for the simulation.
The goal of the simulation was to cover from 300Hz to 1.1KHz. As you can see this waveguide and cone driver combination has a raising power response throughout this range. This was designed to counteract the falling axial response of the Oblate Spheroid. However, from what you have stated it would appear to me that this raising response is unnecessary or even problematic. In addition, the radiation beam width is still narrowing throughout the 300Hz to 1.1KHz range so that alone should be enough to counteract the Oblate Spheroid’s natural falling axial response. My simulation might just be a “How not to do” guide. Never the less, I welcome your comments.
I understand that you have spent most of your time with compression drivers. There has probably been little incentive to experiment with cone drivers. However, I would be very interested in your thoughts and ideas on using cone drivers with the Oblate Spheroid waveguide.
Rgs, JLH
It takes the 4th to determine altitude, to complete the 3D positioning. 3 only gives 2D positioning.gedlee said:
During some tests, I have found that if drivers have strong resonance in this frequency range, the it is very unpleasant. However, if the resonance is about -40db or more in 0.3ms, the the sound becomes smooth. I have used drivers that extend close to 40KHz, and it sounded quite smooth with more detail.JLH said:
"One does not get any direct sound, only ambient sound from the room and this is what the surrounds are supposed to do.
Then there is Floyd Toole who swears the opposite."
I believe Dolby and Lexicon also do, and that their position is that with discrete surrounds all the ambiance that's supposed to be there is encoded.
"From my knowledge of these two indivisuals I would say that the preference difference comes from usuage differences. Holman is a film guy and Floyd is a orchestra guy. Not surprising that they might differ on expectation.
I only use the surrounds for film, hence I follow Holmans recommendations."
Interesting, I guessed the opposite, as the surround in music is pretty much all ambiance, whereas movies often have effects originating from the surround channels.
Then there is Floyd Toole who swears the opposite."
I believe Dolby and Lexicon also do, and that their position is that with discrete surrounds all the ambiance that's supposed to be there is encoded.
"From my knowledge of these two indivisuals I would say that the preference difference comes from usuage differences. Holman is a film guy and Floyd is a orchestra guy. Not surprising that they might differ on expectation.
I only use the surrounds for film, hence I follow Holmans recommendations."
Interesting, I guessed the opposite, as the surround in music is pretty much all ambiance, whereas movies often have effects originating from the surround channels.
Dr Geddes,
First off, thankyou for sharing your knowledge in an open forum like this. Your writings, together with Dr Floyd Toole's, are the most useful approach to domestic sound-system design that I have found.
Early in the thread Graff asked the following question:
You responded:
I invite you to comment on the JBL LSR6328P Monitor:
http://www.jblpro.com/LSR6300/LSR6328P.htm
JBL claim to be addressing many of the same issues you have identified as important, it even uses an "elliptical oblate spheroidal waveguide for precise pattern control".
I would be interested in your critique of this product. Would it benefit from a foam plug, & if someone were to do so then owe you money?
I am getting ready to pull the trigger on either ESP's from Thailand or kits from your good self. Two more question please:
1. Wouldn't the best waveguide profile include a reverse os contour for the mouth round-over, or at least a smaller catenoid, & if not why?
2. Which would you consider to be a better choice for a system that serves both stereo & ht duties (assuming correct placement of centre)... 3 Nathan/ESP 10's or 2 Abbey/ESP's?
thanks again, & good luck with the venture 🙂
BTW...why don't you try to arrange some professional reviews, I imagine there must be plenty of interest. The current reviews are useful (particularly drumdude's) but a 6moons review or similar might be all the marketing you need. I can't even find a single review of the ESP's... seems odd, particularly if you want to tap the domestic (non-pro) market, amirite?
First off, thankyou for sharing your knowledge in an open forum like this. Your writings, together with Dr Floyd Toole's, are the most useful approach to domestic sound-system design that I have found.
Early in the thread Graff asked the following question:
graaf said:
You responded:
gedlee said:
I invite you to comment on the JBL LSR6328P Monitor:
http://www.jblpro.com/LSR6300/LSR6328P.htm
An externally hosted image should be here but it was not working when we last tested it.
JBL claim to be addressing many of the same issues you have identified as important, it even uses an "elliptical oblate spheroidal waveguide for precise pattern control".
I would be interested in your critique of this product. Would it benefit from a foam plug, & if someone were to do so then owe you money?
I am getting ready to pull the trigger on either ESP's from Thailand or kits from your good self. Two more question please:
1. Wouldn't the best waveguide profile include a reverse os contour for the mouth round-over, or at least a smaller catenoid, & if not why?
2. Which would you consider to be a better choice for a system that serves both stereo & ht duties (assuming correct placement of centre)... 3 Nathan/ESP 10's or 2 Abbey/ESP's?
thanks again, & good luck with the venture 🙂
BTW...why don't you try to arrange some professional reviews, I imagine there must be plenty of interest. The current reviews are useful (particularly drumdude's) but a 6moons review or similar might be all the marketing you need. I can't even find a single review of the ESP's... seems odd, particularly if you want to tap the domestic (non-pro) market, amirite?
This is my understanding as well, that's why I thought the surrounds should have the same capability as the mains.noah katz said:
MEH said:
I don't know if they are not interesting, but I haven't thought about it. I've read Holman's explaination and it makes sense. Floyd's comments came via an E-mail discussion and was without justification so I guess I'd want to learn more before I decided.
I know that I really dislike to be "aware" of the surrounds and this is something that Holman stresses, that the surrounds should never be obvious. The lack of a direct sound helps this out a lot.
JLH said:
If you look at the data you will see that through this range the device is not CD, its directivity is changing, hence the axial response need not be flat. At the lower end of all these devices, where the wavelengths are large, the polar and power responses are not simple and most of the simple rules of thumb fail.
I have used pistons for sources a lot. Compression drivers always work better, they are designed to work into small apertures. But to save cost I have done a number of cone driven waveguides. The waveguide is a vast improvment over the baffled cone, but no where near as good as a compression driver.
About the JBL stuff, I know that a great deal of these designs relied heavily on my work, they admit that privately, but of course not publicly. These very small devices fall into that area that I was talking about above, where things are not so simple and the simple rules don't apply. These shallow waveguides are certainly a help, but in no way can be compared in performance to one of my waveguides. But clearly space and cost were issues in this design and my waveguides don't meet those criteria.
junglist said:
The JBL device is probably too small to have an effective foam plug, but there is no doubt that it would help. Infringmrnt woul depend on how they did it and waht the claims for my patent say when it issues.
The use of a catenoid on the outside edge is indeed something that I have considered. The outseide edge is far less critical than the throat however.
Get the two Abbey's, hands down. And for what its worth, I do sell fully assembled and painted speakers for those who fear the assmebly is a bit over their head. Its apparantly not as easy as some have hoped.
I know several reviewers, and, to me, this whole thing is a can of worms . There is nothing "unbiased" about it and you basically "buy" the review. Thats why, to me, the reviews that I posted are the most meaningful because I had no connection to any of those people at all and they had no connections to anything else either. They were as fair and unbiased as you are going to find. And the "professional" reviewers don't have any more credentials for doing this work than any of my reviewers.
Why people trust "professional" reviews is totally beyond my comprehension.
pooge said:
If thats the bi-radial waveguide patent, no, it wouldn't. IMO it isn't even a real waveguide. Its too short and shallow. The term "waveguide" sounds too cool not to apply it to everything in sight, hence everything is a waveguide.
Personally, I like this arrangement. The shape of the horn allows close vertical spacing, ensuring a wide null angle. You definitely don't want the vertical nulls too close to the forward axis. That's the main thing I've always been concerned with using large round horns.
junglist said:
Alright this is going back a few posts, but I can't resist the bad movie reference. In space it takes 7 points of origin to travel through the stargate.
I'm with Geddes on the dipole surrounds by the way. I have built a multitude of surrounds now, and even made some which had the ability to switch from dipbole to bipole to monopole. MY current design is a ripoff of the M&K tripole even using their old enclosures and top tweeters (Though modified with a rear chamber and new diaphragm). They have a switch to turn off the side drivers, and other than with music, I much prefer the side drivers on, it makes the rear speakers much harder to locate. I think what you choose will be very room Dependant to be honest. A proper rectangle shaped rooms which allows the surrounds to be to the sides and rear of the listener could get away with direct radiators better, but many of us don't have rooms that can do this, and so dipole designs can help hide these flaws.
I'm with Geddes on the dipole surrounds by the way. I have built a multitude of surrounds now, and even made some which had the ability to switch from dipbole to bipole to monopole. MY current design is a ripoff of the M&K tripole even using their old enclosures and top tweeters (Though modified with a rear chamber and new diaphragm). They have a switch to turn off the side drivers, and other than with music, I much prefer the side drivers on, it makes the rear speakers much harder to locate. I think what you choose will be very room Dependant to be honest. A proper rectangle shaped rooms which allows the surrounds to be to the sides and rear of the listener could get away with direct radiators better, but many of us don't have rooms that can do this, and so dipole designs can help hide these flaws.
gedlee said:
What?
Surely you're not claiming your speakers produce no vertical off-axis nulls.
A while back, I asked if you had vertical off-axis response curves for any of your speakers. Now would be as good time as any to show those.
You didn't read what I said:
You said "... too close to the forward axis" to which I responded "it doesn't happen" - they are not "too close". A listener is never going to be at a null.
You said "... too close to the forward axis" to which I responded "it doesn't happen" - they are not "too close". A listener is never going to be at a null.