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Old 25th January 2009, 01:26 AM   #981
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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
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Old 25th January 2009, 03:23 AM   #982
gedlee is offline gedlee  United States
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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.
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File Type: pdf prototype_1_09.pdf (29.8 KB, 170 views)
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Old 25th January 2009, 10:30 PM   #983
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Would that be in back to back dipole configuration?
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Old 25th January 2009, 10:42 PM   #984
gedlee is offline gedlee  United States
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Quote:
Originally posted by paulspencer
Would that be in back to back dipole configuration?
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.
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Old 25th January 2009, 10:46 PM   #985
Variac is offline Variac  United States
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Also might be interesting to see what the effects are if the surrounds are recessed (partially?)into the wall .
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Old 25th January 2009, 11:00 PM   #986
pooge is offline pooge  United States
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Quote:
Originally posted by gedlee


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.

Just curious. Where is that evidence located, and in what direction should the monopoles face?
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Old 25th January 2009, 11:13 PM   #987
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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.
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Old 26th January 2009, 01:40 AM   #988
gedlee is offline gedlee  United States
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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.
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Old 26th January 2009, 01:45 AM   #989
gedlee is offline gedlee  United States
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Originally posted by Variac
Also might be interesting to see what the effects are if the surrounds are recessed (partially?)into the wall .

I can't do that but its an interesting thought.
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Old 26th January 2009, 02:44 AM   #990
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"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.
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