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Ping Earl Geddees! [message #18330] Thu, 15 December 2005 07:08 Go to next message
spkrman57
Messages: 522
Registered: May 2009
Illuminati (1st Degree)
I just have one question, "Why did you sell your JBL 4430's?"

With the different designs you have had and promote, I am curious how the 4430's fell within the group.

Ron

(Current owner of your old 4430's)

The waveguide [message #18331 is a reply to message #18330] Mon, 19 December 2005 07:25 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
The waveguide in the 4430's was vastly inferior to my current one. The rest of the 4430 design is OK, but could be improved. I had once thought of just replacing the waveguide, but then I concluded that there were so many other things that I could try at the same time. I have often refered to the Summa as an updated 4430, which was itself an updated A7. The general concept (2-way, CD) is sound (pun intended) but we know so much more today and have so much better components. I am not a nastalgia fan, if you couldn't tell. Nostalgia is for old recordings not old equipment.

Re: The waveguide [message #18333 is a reply to message #18331] Mon, 19 December 2005 14:29 Go to previous messageGo to next message
spkrman57
Messages: 522
Registered: May 2009
Illuminati (1st Degree)
Earl,
Thanks for the reply. One of these days when I have time I will have to search out the systems you reference and look them over.
Ron

The A7's [message #18334 is a reply to message #18333] Mon, 19 December 2005 15:38 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
The only speaker that I referenced besides the 4430's was the A7.

This is the Altec-Lansing A7 more effectionately know as the "Voice of the Theater". It was a 15" woofer and a 1" compression driver, as is the 4430's and the Summa.

The 4430's were an improvement in that the horn was axi-symetric and Constant directivity, the A7 was not. The 4430's had a better crossover.

The Summa's are an improvement in that the waveguide is not a diffraction device - the 4430's are - and it has a foam refractive plug for even lower diffraction in the waveguide. It has a low diffraction enclosure which is also more solid than either the A7 (which were pretty flexible) or the 4430 (better than the A7. Finally the Summas have a better crossover optimized for polar response not axial response.

So each of these speakers has the same basic design, but each of them uses more up to date technology and theory to achieve a better performance. If you liked A7's or 4430's you'd love Summas.


Re: The A7's [message #18339 is a reply to message #18334] Tue, 20 December 2005 12:49 Go to previous messageGo to next message
colinhester is currently offline  colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas
Illuminati (3rd Degree)
Earl, Did you ever mod the A7s? I know cabinet bracing is a big part of the process, but did you ever look at the xover?......Colin

PS. I have Spkrmn57's old A7s, which I love (the speaker, not Ron.) Maybe I can talk him out of the 4430s when he gets the Summas .

Re: The A7's [message #18340 is a reply to message #18339] Tue, 20 December 2005 13:11 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
I have not used Altec stuff for decades. I have some old drivers and horns for A7's if anyones interested. I simply don't believe in using old obsolete stuff.

I like the newer offerings from companies like B&C. Extremely good quality at very reasonable prices. And I prefer composit plastics to wood. Why go anywhere else?

Re: The A7's [message #18341 is a reply to message #18340] Tue, 20 December 2005 14:45 Go to previous messageGo to next message
spkrman57
Messages: 522
Registered: May 2009
Illuminati (1st Degree)
Earl,

How about a link to the Summa's you mentioned. The A7's I am already familiar with as I cut my teeth into high efficiency with them and then moved on to JBL with mainly my variations of the 4 Pi Pro system Wayne came up with.

I use (Bruce) Edgar wood horns with Altec 902's for most of mine though.

By the way, Colin is using stock N-501 8A crossovers which could be improved on.

Regards, Ron



Summas [message #18343 is a reply to message #18341] Tue, 20 December 2005 15:55 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
Simply go to www.gedlee.com and click on the Summa Link.

Aspect ratio [message #18345 is a reply to message #18334] Wed, 21 December 2005 09:21 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18791
Registered: January 2001
Illuminati (33rd Degree)

I respect you and I respect your work. But I don't like axisymmetric horns, never did. They're nice for mathematical simplicity, and easy to promote as a purist thing. But I can't think of a single instance where a symmetric coverage pattern is desired.

I much prefer a radial horn, maybe one of the other horn variants in your book would satisfy. Seems like I recall you mentioned a geometry that provides a rectangular pattern but that still provides some of the other benefits that you have worked towards in respect to reduction of high order modes and diffraction.

The rooms in homes are rectangular, and the desired pattern is wider than it is tall. We don't want the sound bouncing off the floors and ceiling, energy there is a waste. The coverage required in a prosound environment is almost always wide, whether inside small indoors venues or large outdoor events. If axisymmetric horns are used, they are best splayed so that they form what is essentially a multicell horn. So since we're working with a rectangular coverage pattern, I prefer a horn with a rectangular aspect ratio.


I can think of one [message #18346 is a reply to message #18345] Wed, 21 December 2005 12:47 Go to previous messageGo to previous message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
"But I can't think of a single instance where a symmetric coverage pattern is desired."

Find me a woofer with an asymetrical polar pattern and I'll agree with you. To me MATCHING directivity, DI, power response through the crossover is more important having a narrower vertical directivity.


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