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?
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?
Nope... just wired them series parallel.
I noticed a giant wall of sound.
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.
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.
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.
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.
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.
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.
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.
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
)
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
)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.
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.
BSC for a Line Array
Theo,
I can not verify your observation but I would say that in my experience the BSC in a line array is likely a function of primarily the baffle width. This would especially be true for a near field array as you have very little vertical radiation (no energy toward the floor or the ceiling) from the ends of the array. Hence, only the baffle width should come into play.
Jim
Theo,
I can not verify your observation but I would say that in my experience the BSC in a line array is likely a function of primarily the baffle width. This would especially be true for a near field array as you have very little vertical radiation (no energy toward the floor or the ceiling) from the ends of the array. Hence, only the baffle width should come into play.
Jim
LA Baffle
Jim - My Line arrays are not done yet so no measurements - the observation came from Rick Craig at Selah as a "watch out" as he gave me advice regarding my project.
So, I take it you do not see this phenemenon (that is, a bump corresponding to the wavelength of the height of the baffle) in your arrays?
hmmmmm.
Jim - My Line arrays are not done yet so no measurements - the observation came from Rick Craig at Selah as a "watch out" as he gave me advice regarding my project.
So, I take it you do not see this phenemenon (that is, a bump corresponding to the wavelength of the height of the baffle) in your arrays?
hmmmmm.
Re: What tweeks?
Recognizing that many folks here are into DIY because they enjoy the challenge, perhaps I should not spoil the fun of discovery for them. I reserve my highest level of respect for DIY'ers that work at that level.
Hint, it is common sense stuff. Think about what physical factors impair a driver from launching a clean, fast risetime wave front. Think about tweeks that wll reduce basket ringing, cabinet ringing, mechanical system energy storage.....that sort of stuff.
TheoM said:
Recognizing that many folks here are into DIY because they enjoy the challenge, perhaps I should not spoil the fun of discovery for them. I reserve my highest level of respect for DIY'ers that work at that level.
Hint, it is common sense stuff. Think about what physical factors impair a driver from launching a clean, fast risetime wave front. Think about tweeks that wll reduce basket ringing, cabinet ringing, mechanical system energy storage.....that sort of stuff.
So heres a question, as far as tapering the frequncies of the drivers.
If you run all the woofers on the same crossover, say 0-4000Hz, but you apply some weights (mass) to the drivers on the outer edges they will lower there frequency extension and improve there Fs.
Now they lose there high end, say now the speakers only go to 2K or 3KHz. So even though they are on the same crossover network, if they can't play a certain frequncy do they now contribute to the load at that frequency.
For example 4 drivers on a 4Khz LP crossover network are presenting a 8 ohm load, but if two of them naturally only go to 2Khz, from 2Khz-4Khz does the amplifier only see a 4 ohm load from the other two (parrellel) drivers?
Does this make sense at all? Using all the same drivers, but making the outer ones unable to play higher frequencies so that you (hopefully) can limit combing. But not by using elaborate crossovers, just adding mass to the drivers.
If you run all the woofers on the same crossover, say 0-4000Hz, but you apply some weights (mass) to the drivers on the outer edges they will lower there frequency extension and improve there Fs.
Now they lose there high end, say now the speakers only go to 2K or 3KHz. So even though they are on the same crossover network, if they can't play a certain frequncy do they now contribute to the load at that frequency.
For example 4 drivers on a 4Khz LP crossover network are presenting a 8 ohm load, but if two of them naturally only go to 2Khz, from 2Khz-4Khz does the amplifier only see a 4 ohm load from the other two (parrellel) drivers?
Does this make sense at all? Using all the same drivers, but making the outer ones unable to play higher frequencies so that you (hopefully) can limit combing. But not by using elaborate crossovers, just adding mass to the drivers.
weights on outer line array speakers
I would not put weights on the speakers. I know there are circumstances where it might make sence - but not here.
Note from the post above:
Think about what physical factors impair a driver from launching a clean, fast risetime wave front.
The biggest one of those is cone mass. The different accerleration and momentum of the outer drivers will smear the detail - probably badly. ... and it won't really fix the comb filetering much - since that goes on all over the place, at many different frequencies and is a function of the interactions of all the drivers.
The best thing you can do to reduce comb filtering is follow the rules in Jim Griffin's paper relative to the distance betweeen cone centers being no more than a wavelength: To wit, but unformatted:
Comb Line Destructive Interferences
for Circular Drivers Line Arrays
[1], [2], [3],
[4]
§ Limit center to center spacing between
drivers to less than one wavelength
§ Use power tapering to reduce effect
If you read about the Line Arrays designed recently by Joe A Polito what I think he did was put a resistor on the outer drivers in a large array (like 12 woofers) to lower their gain. Anyway, the reasoning for that I'm not confident about so I won't comment - but I do think slowing down a woofer that is designed to be coupling with other woofers is a bad move. Ted.
I would not put weights on the speakers. I know there are circumstances where it might make sence - but not here.
Note from the post above:
Think about what physical factors impair a driver from launching a clean, fast risetime wave front.
The biggest one of those is cone mass. The different accerleration and momentum of the outer drivers will smear the detail - probably badly. ... and it won't really fix the comb filetering much - since that goes on all over the place, at many different frequencies and is a function of the interactions of all the drivers.
The best thing you can do to reduce comb filtering is follow the rules in Jim Griffin's paper relative to the distance betweeen cone centers being no more than a wavelength: To wit, but unformatted:
Comb Line Destructive Interferences
for Circular Drivers Line Arrays
[1], [2], [3],
[4]
§ Limit center to center spacing between
drivers to less than one wavelength
§ Use power tapering to reduce effect
If you read about the Line Arrays designed recently by Joe A Polito what I think he did was put a resistor on the outer drivers in a large array (like 12 woofers) to lower their gain. Anyway, the reasoning for that I'm not confident about so I won't comment - but I do think slowing down a woofer that is designed to be coupling with other woofers is a bad move. Ted.
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