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Old 2nd March 2008, 12:00 AM   #21
bjorno is offline bjorno  Sweden
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Old 2nd March 2008, 12:02 AM   #22
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Old 2nd March 2008, 04:45 AM   #23
chops is offline chops  United States
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Thanks for the input and charts guys.

Auplater, very nice work! Would love to see what the rest of the setup looks like.

Bjorno, thanks for those simulations. Unfortunately, I'm not 100% certain of what I'm looking at, but I think I get the idea.


Anyway, I think I might have figured out a solution to this project...

First off, I'm going to scrap the entire idea of building the LA's with the Dayton Classic drivers. Not only are they too large, but they also have those midrange issues and will not match up to the Dayton planars properly.


So what I think I will do now is this...

I will buy a total of (20) GR M-130 drivers and a total of (15) Dayton PT2C-8 planars. The left and right channels will each have EIGHT woofers and SIX planars, the center channel will be exactly half with FOUR woofers and THREE planars.

This will keep me in budget (just over $1k for drivers alone), will provide better performance due to the better quality woofers, they are smaller and their C-T-C will be closer allowing for a higher xover freq to match up with the planars (2kHz), will be a nominal 4 ohms for the main channels (nominal 8 ohms for the center channel), the main channels will probably extend down into the mid-30's pretty well, and will be like the smaller, cheaper baby brother of the GR LS-6. :thumb:

From the looks of the plot on GR's website for the M-130, even off axis, a 2kHz xover point looks to be well within reach as the driver seems to be flat at 2kHz. Since if I am staying with the Dayton planars due to their price and performance, I am stuck with a minimum xover point of 2kHz and from what I gather, C-T-C spacing with 5.25" drivers at this freq shouldn't be an issue anymore.

So what do you all think about this idea? Am I finally on the right track this time?
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Old 2nd March 2008, 06:05 AM   #24
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Here is what I get from my line arrays plus woofers in concrete boxes:

Click the image to open in full size.

Dip on 7 KHz and roll off above 16 KHz are errors of measurement: I placed a large diaphragm condenser mic in the center between speakers. A mic has roll-off above 16 KHz.

Here is one woofer:

Click the image to open in full size.

Here is one array:

Click the image to open in full size.
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Old 2nd March 2008, 06:31 AM   #25
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Quote:
Originally posted by chops
I have a couple questions about the center channel as well...

1) What would be a good number of drivers to go with?
Zero.

Proper LAs give very good stereo image so no center speaker is needed. I also never use rear speakers but nobody misses that special effects in movies they are used for after the initial idea of "quadro sound" failed many years ago.
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Old 2nd March 2008, 07:11 AM   #26
chops is offline chops  United States
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Quote:
Originally posted by Wavebourn


Zero.

Proper LAs give very good stereo image so no center speaker is needed. I also never use rear speakers but nobody misses that special effects in movies they are used for after the initial idea of "quadro sound" failed many years ago.

Stereo imaging has nothing to do with needing a center channel or not. A center channel is required regardless of the quality of the main channels for proper dialog playback in movies.

Side and back surrounds are not an "initial idea" that will eventually fail either. They are required for proper playback of movies. Again, they have absolutely nothing to do with the quality of the main channels.

Besides, I have already answered my own center channel question in my previous post above.
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Old 2nd March 2008, 11:46 AM   #27
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Default rest of setup

BG-75 / ATC planar dipole construction

Click the image to open in full size.

Click the image to open in full size.

sub woofers..
Click the image to open in full size.
Click the image to open in full size.

C-T-C @ 5 1/2" will be asmaller issue at 2 Khz for sure... it's just whether or not you'll hear the lobing. It will definitely be an improvement over the 6 1/2" 'ers, though. wavelength @ 2100 Hz ~ 6.5", and ideally you'd like to keep the ctc distance well below that... to minimize irregular response... that's the problem

Jim Griffin's paper on the subject...
http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

John L.
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Old 2nd March 2008, 12:06 PM   #28
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Quote:
Originally posted by chops
Stereo imaging has nothing to do with needing a center channel or not. A center channel is required regardless of the quality of the main channels for proper dialog playback in movies.
The argument is that if you sit in the sweet spot whilst watching a movie and you also have mains that image well, then they should be able to throw a phantom image using the mono centre channel signal.

If these conditions are met, then its possible you could omit the centre and maybe even have a better system for it, the front sound stage would certainly be consistent.
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Old 2nd March 2008, 12:21 PM   #29
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Quote:
Originally posted by ShinOBIWAN


The argument is that if you sit in the sweet spot whilst watching a movie and you also have mains that image well, then they should be able to throw a phantom image using the mono centre channel signal.

If these conditions are met, then its possible you could omit the centre and maybe even have a better system for it, the front sound stage would certainly be consistent.
That has been my experience with my present setup using ML Prodigy electrostatics. (I am also fond of line arrays for their high SPLs at deliciously low distortion.)
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Old 2nd March 2008, 12:27 PM   #30
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Default center channel

Quote:
Originally posted by ShinOBIWAN


The argument is that if you sit in the sweet spot whilst watching a movie and you also have mains that image well, then they should be able to throw a phantom image using the mono centre channel signal.

If these conditions are met, then its possible you could omit the centre and maybe even have a better system for it, the front sound stage would certainly be consistent.
Ant is on the money here. My setup images the vocal tracks very well indeed w/o a center speaker. However, I also use the speakers built into my display as the center channel, giving the versatility of independently "bringing them up" if necessary on less than ideal video material. An even greater advantage of no default center channel is improved music reproduction in systems doing dual duty (as mine does)... you don't have to screw around with synthetic dsp modes and such when listening only.

With my recently acquired 7.1 channel Denon, I've managed to replace all the other gear and greatly simplify the operation of all the uses for this room (not to mention the rats nest of wiring behind the stack)

I'm getting too old to tolerate constantly switching cords, etc....

John L.
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