Thanks for sharing you experience. Just makes me more anxious to get my hands on my forthcoming pair of abbey kits!
Earl,
Maybe here would be a better place to give the available details on the Harper 8's, rather than sidetrack Matt's build thread?
Intested to hear more about these. Were you able to cast the whole baffle?
-Tony
Earl,
Maybe here would be a better place to give the available details on the Harper 8's, rather than sidetrack Matt's build thread?
Intested to hear more about these. Were you able to cast the whole baffle?
-Tony
Tony
You are correct of course. Its just a matter of where I am at the time.
Thge prototypes are not tooled parts, but hand made, usually with bondo and sanding and more bondo and more sanding and boy are my arms tired!!!
But yes, the Harper loks like a winner in the small category. Its small and inexpensive and I know that I will be useing four myself (for the surrounds). The prototype results are shown below.
Once I have a prototype that I like, I make permanent tools.
You are correct of course. Its just a matter of where I am at the time.
Thge prototypes are not tooled parts, but hand made, usually with bondo and sanding and more bondo and more sanding and boy are my arms tired!!!
But yes, the Harper loks like a winner in the small category. Its small and inexpensive and I know that I will be useing four myself (for the surrounds). The prototype results are shown below.
Once I have a prototype that I like, I make permanent tools.
paulspencer said:
I think that you mean for the surrounds. More and more information is coming out that supports the surrounds being monopoles and not dipoles. This is a change from pervious positions. The Harpers will be monopoles, but will be small enough to hang from the side walls. I'm going to look at the effect that the walls will have on the response and see what the best orientation would be.
Yes I meant for surrounds. In your HT book you had a pair of bookshelf speakers back to back hanging from the ceiling, so I thought this is probably what you were going to do with these. That's a curious shift from your previous position.
I'd be curious to find out more about the evidence you mentioned. Is this some of your work, or from others?
The idea of dipole surrounds always seemed to make sense to me. Yet with the number of drivers used, I also think why not just put a small array of shallow profile (or flush mounted) monopoles on the side walls. Instead of a single dipole with twice as many drivers - two monopoles.
I'd be curious to find out more about the evidence you mentioned. Is this some of your work, or from others?
The idea of dipole surrounds always seemed to make sense to me. Yet with the number of drivers used, I also think why not just put a small array of shallow profile (or flush mounted) monopoles on the side walls. Instead of a single dipole with twice as many drivers - two monopoles.
The evidence is from Floyd Tooles book and lecture. He claims that monopoles facing the listeners were found to be more appealing, but that the tembre of the speakers had to be the same as that of the mains.
Thomason Holman was the one who said that dipoles are the better choice, but that was quite a while ago. I'm not sure if thats still his position. I'm going to try the monopoles now that I have a speaker that suites me.
How to point the monopoles when one uses a fairly directive speaker is a different question and one that I want to look into. By default the surrounds in a small room have to be at a junction of two walls. One should take this into consideration in placing and pointing them, but the answer is not obviuos to me at this point.
Thomason Holman was the one who said that dipoles are the better choice, but that was quite a while ago. I'm not sure if thats still his position. I'm going to try the monopoles now that I have a speaker that suites me.
How to point the monopoles when one uses a fairly directive speaker is a different question and one that I want to look into. By default the surrounds in a small room have to be at a junction of two walls. One should take this into consideration in placing and pointing them, but the answer is not obviuos to me at this point.
"The evidence is from Floyd Tooles book and lecture. He claims that monopoles facing the listeners were found to be more appealing, but that the tembre of the speakers had to be the same as that of the mains."
As I believe you yourself said, it's awful to have the surrounds easily localizable.
The only way I can see for this not to happen in the above situation is to be a good distance from them, and most people don't have rooms that big.
I don't see how dipoles are feasible if one wants bass down to below 100 Hz, so that leaves bipoles or monopoles facing upward; I've read many times that they work very well and would be the simplest/cheapest to implement.
How about this - take one of the B&C 8" coaxes and stick it on the end of a wood conga drum shaped enclosure and tip it in, say, 30 deg from pointing straight up.
IMO it would look way nicer than any other surround speaker I've seen.
Wouldn't have your waveguide IP, Dr. Geddes, but you say you can sell B&C as cheap as anyone so why wouldn't people buy a kit from you?
The enclosures would be the tricky part (though I imagine the XO isn't that straightforward either).
There are lots of cheap, nice looking wooden congas on ebay; perhaps one could get the bodies only.
"Thomason Holman was the one who said that dipoles are the better choice, but that was quite a while ago. I'm not sure if thats still his position."
The rationale for it back then was to decorrelate the mono surround channels, and that's no longer an issue.
As I believe you yourself said, it's awful to have the surrounds easily localizable.
The only way I can see for this not to happen in the above situation is to be a good distance from them, and most people don't have rooms that big.
I don't see how dipoles are feasible if one wants bass down to below 100 Hz, so that leaves bipoles or monopoles facing upward; I've read many times that they work very well and would be the simplest/cheapest to implement.
How about this - take one of the B&C 8" coaxes and stick it on the end of a wood conga drum shaped enclosure and tip it in, say, 30 deg from pointing straight up.
IMO it would look way nicer than any other surround speaker I've seen.
Wouldn't have your waveguide IP, Dr. Geddes, but you say you can sell B&C as cheap as anyone so why wouldn't people buy a kit from you?
The enclosures would be the tricky part (though I imagine the XO isn't that straightforward either).
There are lots of cheap, nice looking wooden congas on ebay; perhaps one could get the bodies only.
"Thomason Holman was the one who said that dipoles are the better choice, but that was quite a while ago. I'm not sure if thats still his position."
The rationale for it back then was to decorrelate the mono surround channels, and that's no longer an issue.
Noah
My idea is this. Based on experience, the foam in my designs makes the sources very hard to localize, the speakers disappear. Anyone who has heard them will attest to that. So, perhaps, the Harpers may just be the right thing. Direct radiating surrounds that aren't localized. Thats my hope.
Coaxs would always be localizable because of the poor waveguides that they are forced to use.
My idea is this. Based on experience, the foam in my designs makes the sources very hard to localize, the speakers disappear. Anyone who has heard them will attest to that. So, perhaps, the Harpers may just be the right thing. Direct radiating surrounds that aren't localized. Thats my hope.
Coaxs would always be localizable because of the poor waveguides that they are forced to use.
"the foam in my designs makes the sources very hard to localize"
They don't disappear w/o the foam?
My experience is that lots of good speakers disappear if they're located w/enough distance from the back and side walls.
This isn't possible w/most surrounds, which are wall mounted, so other means must be used.
BTW, those polar plots for the Harper's look amazingly good.
When will you get to try them as surrounds?
They don't disappear w/o the foam?
My experience is that lots of good speakers disappear if they're located w/enough distance from the back and side walls.
This isn't possible w/most surrounds, which are wall mounted, so other means must be used.
BTW, those polar plots for the Harper's look amazingly good.
When will you get to try them as surrounds?
In my experience any horn or waveguide (except mine) are localizable and this has been one of my issues about them. With the foam they aren't. The foam takes away whatever it is that we localize to. I suspect that it is the HOM, but thats just a hypothesis. Without the foam the OS waveguide tend to disappear much better than most, but with it they are gone. Diffraction horns are always obvious where they are - you could never fool me with that type of device.
Some piston loudspeakers can disappear, but few. Most dome tweeters can be easily localized. So, to me, any dome tweeter system would not be a good choice for a surround if pointed at you.
Some piston loudspeakers can disappear, but few. Most dome tweeters can be easily localized. So, to me, any dome tweeter system would not be a good choice for a surround if pointed at you.
gedlee said:
Earl,
Does how intimately the foam is in contact with the waveguide have an effect? The reason I ask is that in order to attach the foam to the waveguide the former is sprayed with glue - I have found that this is never evenly spread on the foam.
So is the random nature of the glue breaking up the HOMs or is it the body of the foam that is de-localizing the sound?
Regards
Alan
I think it can be feasible. I did a quick test of dipoles against a side wall and found they went flat down to 80 Hz without eq. Not a very rigorous test, but enough to suggest it just might work if I try it in the future. I'm not sure if dipoles make much sense with waveguide-based speakers like the summa.
AlanElsdon said:
I've wondered about this myself. If the glue gets very thick, as it does if the foam is reused many times, then a clear effect can be noted. But I cannot tell anything is effected by the thin layer of the first application. There will be some effect, but I think that it is small if the glue layer is small.
gedlee said:
I actually talked with him maybe a month ago about this. I was asking about the THM speaker system, and what the surrounds were like. He was a little vague, I think intentionally, but I think eh was suggesting that he still prefers dipoles. He seemed to feel it was very room dependent, and suggested it was whatever makes the user happy. I think he felt that most rooms were of poor shape and size for a good theater setup, and that the surround were a key speaker to modify in order to fit the room, and best develop the desired experience. However, he seemed to indicate that with his new 10.2 system, or even the modern 7.1's to a point, that monopoles might be a better option in the right room. His requirement for monopoles to work correctly seems to be beyond any room I've ever had, but I'm sure is common enough in custom home theaters. The listener needs to be a fair distance from each surround speaker, relatively equidistant. My room is far too small for all but one person to be in that position. Additionally, my living room is open to my kitchen, so I don't have a side wall to mount those speakers on. He also mentioned liking the sound of a surround with mostly direct radiating sound, and some diffused dipole. I would suggest that this is very similar to what I developed for my surrounds using those M&K tripole enclosures I picked up.
Oh wait I forgot a key part of his 10.2 and suggestions. He said that systems should have both. The primary surrounds should be monopole while the other effects channels should be dipole. I believe he said that is how his system is to be arranged.
So who do we believe, Floyd or Thom? Hasn't that been the issue all along, people who basically invented these concepts or were influential in the standards, argue over which is best.
I don't have enough amplifier channels or surround speakers, but I am interested in testing Thom's idea of lot's of surrounds with a mix. He suggested a way to use the 7.1 to create the effect he was looking for with discrete 10.2. He felt that more monopoles helped reduce localization a lot, while improving the rear stage.
I don't have enough amplifier channels or surround speakers, but I am interested in testing Thom's idea of lot's of surrounds with a mix. He suggested a way to use the 7.1 to create the effect he was looking for with discrete 10.2. He felt that more monopoles helped reduce localization a lot, while improving the rear stage.
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