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Old 21st July 2004, 05:08 AM   #21
sqlkev is offline sqlkev  United States
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hey chipco..
as i'm beginning to comprehend the paper Dr. Griffin wrote..
he mentioned power tapering at the end and showed an example to how different combinations of power feeding..
did u take that in account for ur current design? (if you stated somewhere...im sorry i missed it)

if u did not...do u experience the different in sound paths as u move around?

i think i'll stick with this example and play with 12 woofer drivers and 6 tweeters first..
maybe after that i'll experiment different things..

one more question..
i dont recall any mention of BSC in Dr. Griffin's paper..
does it not apply to line array?
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Old 21st July 2004, 12:46 PM   #22
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Quote:
he mentioned power tapering at the end and showed an example to how different combinations of power feeding..
Nope... just wired them series parallel.

Quote:
if u did not...do u experience the different in sound paths as u move around?
I noticed a giant wall of sound.

Quote:
i dont recall any mention of BSC in Dr. Griffin's paper..
That's because it's not in his paper. SRETEN on this forum is the BSC dude.

baffle step calculation and adjustment

This is a good little paper and it emphesizes the importance of the room relative to the BSC.
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Old 21st July 2004, 12:47 PM   #23
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Default Line Array Baffle Step Compensation

Unless you design your line array into an infinite baffle (a wall) or use it open back (dipole), you will need BSC. The amount of BSC will depend upon the placement in the room and such as it always does. Hence, line arrays are no different than point sources in this regard.
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Old 21st July 2004, 12:54 PM   #24
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...and if you can't find SRETEN, Jim Griffin will do.
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Old 21st July 2004, 01:03 PM   #25
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I guess the conclusion of BSC and, for that matter, the crossover was to pick a number and go with it. From a practical standpoint, redesigning a passive crossover and experimenting with new points and compensation would cost as much money as the drivers for this project. Add it up for yourself. Figure four coils and four caps for every test adjustment for a second order cross. I don't have any more projects to use the "surplus" caps and coils. One more speaker project and my azz is outa here.

I wired them up at a 5000Hz cross and put on some music. They sounded good. I left them alone. Not for ever, just until I get the MOX project built. Then I can fiddle alot.
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Old 21st July 2004, 05:08 PM   #26
AJ is offline AJ  United States
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Chipco,

I hear ya' about the passive components. I've got at least a 1000 bucks worth of stuff I'll probably never use laying around. I went ahead and bought an Ashly 3-way active XO yesterday and I'm looking for a third amp right now. I'm trying to find a Panasonic XR45 so I can ditch at least one of my current amps, but everyone's out of stock. I've been wanting to go 3-way active anyway, so now seemed to be the right time. I can just dial the XO where I like it and forget about it.

I've been going nuts trying to decide on a tweeter arrangement for these things. Since I only listen sitting down (my house isn't big enough to worry about walking around in) I've narrowed it down to two choices - I'm either gonna pick up two of the Fountek JP2.0 5 inch true ribbon tweeters from Madisound and try mounting them in the center of the array, similiar to Jim Griffin's Needles, or I'll start with four of the PE PT2 planars per side. It's about the same price both ways. I'm not sure what to expect, but my hearing is shot above 10k anyway so I'll probably love them regardless of any "effects". I can always try the tweeter array idea later.
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Old 21st July 2004, 07:52 PM   #27
sqlkev is offline sqlkev  United States
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chipco..
thanks again for the BSC link...
as i understand it...
ull need to make the baffle wide enough to help the lower end drop...
is that correct?
so in order for the driver to at least play at 190hz..the baffle has to be at least 2 ft wide?
(equation is f3=380/WB where WB=width in feet)

Dr. Griffin
i will mount the drivers on a baffle in an open back and the baffles will be 2-3 feet from the wall...BSC should be taken into account?
i'm trying to determine the F3...any help with this particular project?


i too like the idea of going active with any speaker project..but i need first to buy decent gears first...
before dropping money into amps/cables/xover+eq i'll stick with simple passives for now and see how it turns out...



AJ
if indeed ur ears are shot after 10k...i dont think u can truly appreciate the airyness of the ribbons (thats only my opinion)
i do hope u get to hear and appreciate ur ribbons playing the highs though
keep me updated with ur project as well..
i think ill begin this project next week (as i'm a bit busy for now )
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Old 21st July 2004, 09:50 PM   #28
TheoM is offline TheoM  United States
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Default LA Baffle effects

I found (but have not yet verified) you are likely to have a baffle effect on a line array that's unusual simply because the height of the box is unusual. You are likely to find a lump at the wavelength corresponding to the height of the box.
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Old 21st July 2004, 09:54 PM   #29
sqlkev is offline sqlkev  United States
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Default Re: LA Baffle effects

Quote:
Originally posted by TheoM
I found (but have not yet verified) you are likely to have a baffle effect on a line array that's unusual simply because the height of the box is unusual. You are likely to find a lump at the wavelength corresponding to the height of the box.
so that means the total surface area of the baffle has an effect on the overall FR ?

i think it makes total sense...
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Old 22nd July 2004, 01:00 AM   #30
TheoM is offline TheoM  United States
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Default line array baffle

No, I think its related to the hight, not the surface area. I think its just normal baffle step, but because in an LA you are typically dealing with a box 6 feet high or thereabouts, that you will have half-space on a wave 6 feet long, which is unusual. This would be in the 180 hz range.

Bill, Jim - or whoever - please correct me if I've got the wrong concept here.
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