line arrary with PE buyout drivers??

[Jim Griffin]

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

[chipco3434]

Baffle step or not, would anybody else here agree that the open baffle line array has a very pleasing sound. Very musical and very powerful. When I listen to my box speakers, it just isn't the same. Not even close.

Does anybody else have the same opinion?

[TheoM]

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.

[sqlkev]

Originally posted by chipco3434
Baffle step or not, would anybody else here agree that the open baffle line array has a very pleasing sound. Very musical and very powerful. When I listen to my box speakers, it just isn't the same. Not even close.

Does anybody else have the same opinion?

i will find out possibly next week or two

[rcavictim]

Originally posted by chipco3434
Baffle step or not, would anybody else here agree that the open baffle line array has a very pleasing sound. Very musical and very powerful. When I listen to my box speakers, it just isn't the same. Not even close.

Does anybody else have the same opinion?

Yes, absolutely! Hi efficiency, low distortion, lightning fast transient response that can be further improved with tweaks, great throw, and a huge plus is no cabinet coloration. I'm spending almost all my loudspeaker R&D time budget now in this general direction.

[TheoM]

Hey rcavictim - what tweeks improve your transient response in your line array? thanks.

[rcavictim]

Originally posted by TheoM
Hey rcavictim - what tweeks improve your transient response in your line array? thanks.

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.

[Hybrid fourdoor]

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.

[bhg41088]

seems like the mass would just make them rolloff earlier, but they are still there, just playing at a lower level. Impedience should stay the same.

[TheoM]

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.