Going to be building line arrays using the Infinity speakers made by Vifa from Parts Express. I am 100% sure buying 16-24 (some for backup) of the 7" Infinity drivers. I can still get them for $8 each...
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=299-493
What I'd like to know is should I just use all 7" drivers, covering 40hz up to the tweeter, or would it be better to use some matching 4.5" Infinity speakers as well ($4 each), for the mids? If I went that route I'd have to use a 3-way crossover. Here are the 4.5" speakers:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=299-492
I was thinking of doing 8 7" drivers per side, and if I went with the 4"s then maybe doing 6 7" drivers and 2-4 4" drivers. I could put the 7" on the bottom, the 4.5" on top to the left or right (depending which speaker it is) and put the tweeters next to the 4.5" speakers. That would look pretty good, I'd imagine. You guys know best!
Again, I'm a total newbie to this stuff so any info is GREATLY appreciated! THANKS!
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=299-493
What I'd like to know is should I just use all 7" drivers, covering 40hz up to the tweeter, or would it be better to use some matching 4.5" Infinity speakers as well ($4 each), for the mids? If I went that route I'd have to use a 3-way crossover. Here are the 4.5" speakers:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=299-492
I was thinking of doing 8 7" drivers per side, and if I went with the 4"s then maybe doing 6 7" drivers and 2-4 4" drivers. I could put the 7" on the bottom, the 4.5" on top to the left or right (depending which speaker it is) and put the tweeters next to the 4.5" speakers. That would look pretty good, I'd imagine. You guys know best!
Again, I'm a total newbie to this stuff so any info is GREATLY appreciated! THANKS!
Use as many identical drivers as possible
The approximation of an infinite line source depends on the near perfect coupling of a long line of drivers. Use as many identical drivers as you can afford. If you need to extend the low end get a sub. The 7"'s will be fine in the mids. Also, as they are 7's you want to cross over to the tweeter fairly low-ish - like 1500 to accomodate the rule of cone centers no more than one wavelength apart.
Also - use ribbbon tweeters, or if you can't afford then, get tweeters that are extremely small. They should be as close together as possible and the same length as the woofer line.
The approximation of an infinite line source depends on the near perfect coupling of a long line of drivers. Use as many identical drivers as you can afford. If you need to extend the low end get a sub. The 7"'s will be fine in the mids. Also, as they are 7's you want to cross over to the tweeter fairly low-ish - like 1500 to accomodate the rule of cone centers no more than one wavelength apart.
Also - use ribbbon tweeters, or if you can't afford then, get tweeters that are extremely small. They should be as close together as possible and the same length as the woofer line.
I'm sorry, I haven't been following your project closely enough to remember these details.
1) did you decide on a crossover point? A quick search seems to say that a 2.5khz crossover is what you're going for.
2) did you decide on a tweeter? 2.5 khz can be a little low for a tweeter to go, depending on the tweeter and the crossover.
If you've got a tweeter that goes there without trouble, I would say that those 7" speakers should go to 2.5 khz with no problem. My personal preference is to push crossovers as high or as low as possible (out of the critical range)- but if I were to use those 7's, I would cross them at 2 khz, a whole octave below 4 khz, where the funny stuff starts to happen... 2 khz also happens to be a frequency where they shouldn't have trouble with beaming.
Paired with the right tweeters, I think you're in good shape. Oh, and it looks like those 7"s don't go very low... 50 hz would be a stretch. Did you have plans for a subwoofer?
1) did you decide on a crossover point? A quick search seems to say that a 2.5khz crossover is what you're going for.
2) did you decide on a tweeter? 2.5 khz can be a little low for a tweeter to go, depending on the tweeter and the crossover.
If you've got a tweeter that goes there without trouble, I would say that those 7" speakers should go to 2.5 khz with no problem. My personal preference is to push crossovers as high or as low as possible (out of the critical range)- but if I were to use those 7's, I would cross them at 2 khz, a whole octave below 4 khz, where the funny stuff starts to happen... 2 khz also happens to be a frequency where they shouldn't have trouble with beaming.
Paired with the right tweeters, I think you're in good shape. Oh, and it looks like those 7"s don't go very low... 50 hz would be a stretch. Did you have plans for a subwoofer?
The One wavelength rule
Jim Griffin's guideline is pretty well researched. The wavelength of 1600 hz is 8 and 7/16th inches. Your woofers centers will be about 8" apart (being 7's). They way I read the formula if you try to go higher than that with the woofer you will be violating the rule, and get all sorts of nasty comb filtering in that zone.
see this:http://www.audiodiycentral.com/resource/pdf/nflawp.pdf
At 2500 hz the wavelength is 5 /38 inches, so your woofers centers would be further apart than the wavelength you are trying to couple. 1800 should be as far as you go. Note also, there's a big band of crossover in which the rule will be violated anyway even if you crossover much lower, depending on the order of the crossover. You might consider a 3rd order crossover.
If are going to go to all that trouble to build a line array (and it IS a lot of work) you might as well follow the best advice out there.
Jim Griffin's guideline is pretty well researched. The wavelength of 1600 hz is 8 and 7/16th inches. Your woofers centers will be about 8" apart (being 7's). They way I read the formula if you try to go higher than that with the woofer you will be violating the rule, and get all sorts of nasty comb filtering in that zone.
see this:http://www.audiodiycentral.com/resource/pdf/nflawp.pdf
At 2500 hz the wavelength is 5 /38 inches, so your woofers centers would be further apart than the wavelength you are trying to couple. 1800 should be as far as you go. Note also, there's a big band of crossover in which the rule will be violated anyway even if you crossover much lower, depending on the order of the crossover. You might consider a 3rd order crossover.
If are going to go to all that trouble to build a line array (and it IS a lot of work) you might as well follow the best advice out there.
Thanks for all the replies.
I think due to size contraints I will be going with an 8 woofer array, MAYBE 10. I think 8 is a good number, especially for my first speaker project.
This was taken off Parts Express:
*Frequency range: 40-4,000 Hz *Fs: 41 Hz *SPL: 86dB 2.83V/1m *Vas: 1.03 cu. ft.
By those specs, shouldn't these drivers be able to hit 40hz, or is that the EXTREME? I still don't know what all those numbers mean. The Vas 1.03 cu. ft, does that mean optomially these drivers should have a cubic feet of airspace each? I've been reading about open baffles and such and it just gets more confusing LoL!
Also, I'd like for these to look nice, so if YOU were building them, which tweeters would you go with?
SO sorry for being such a newbie, but I am. Thanks a million, guys!
I think due to size contraints I will be going with an 8 woofer array, MAYBE 10. I think 8 is a good number, especially for my first speaker project.
This was taken off Parts Express:
*Frequency range: 40-4,000 Hz *Fs: 41 Hz *SPL: 86dB 2.83V/1m *Vas: 1.03 cu. ft.
By those specs, shouldn't these drivers be able to hit 40hz, or is that the EXTREME? I still don't know what all those numbers mean. The Vas 1.03 cu. ft, does that mean optomially these drivers should have a cubic feet of airspace each? I've been reading about open baffles and such and it just gets more confusing LoL!
Also, I'd like for these to look nice, so if YOU were building them, which tweeters would you go with?
SO sorry for being such a newbie, but I am. Thanks a million, guys!
Mazeroth,
A big part of a line array is that you make it tall enough to be in the "near field" and thus get less room coloration and more output, and less SPL falloff due to distance. If you don't make it tall enough, you lose the nearfield advantage.
Looking at those drivers, the crossover might be a bit tricky. The 7" has a nasty peak at 4kHz. Also before 1.4k the response steps up suddenly by 3db. This all suggests an xo point a bit lower than you might otherwise want. The off axis response looks much better (30D). The 4.5" looks a bit more manageable but looks like it won't go happily below 200 Hz. The 7" has a high Q and rolls off early. Not much bass at all. It might be a good candidate for trying open baffle!
In fact, an open baffle array with the 7" driver could be an interesting project!
It looks like a choice between using the 4.5" and having to add a woofer to cover up to 200 Hz (or 120 Hz at the lowest) or the 7" (with a bit more work on the xo to deal with the response over 1.4k and a subwoofer as even with this driver you won't get much bass.
A big part of a line array is that you make it tall enough to be in the "near field" and thus get less room coloration and more output, and less SPL falloff due to distance. If you don't make it tall enough, you lose the nearfield advantage.
Looking at those drivers, the crossover might be a bit tricky. The 7" has a nasty peak at 4kHz. Also before 1.4k the response steps up suddenly by 3db. This all suggests an xo point a bit lower than you might otherwise want. The off axis response looks much better (30D). The 4.5" looks a bit more manageable but looks like it won't go happily below 200 Hz. The 7" has a high Q and rolls off early. Not much bass at all. It might be a good candidate for trying open baffle!
In fact, an open baffle array with the 7" driver could be an interesting project!
It looks like a choice between using the 4.5" and having to add a woofer to cover up to 200 Hz (or 120 Hz at the lowest) or the 7" (with a bit more work on the xo to deal with the response over 1.4k and a subwoofer as even with this driver you won't get much bass.
Actually this is not quite correct. The Journal of the AES has published from a number of sources the fact that proper spacing of line array elements depends on the distance between their radiating planes, not acoustic centers. In other words it is the space taken up by the cone surrounds and driver frames, and the enclosure edges in multiple box arrays, that must be held to less than a wavelength at the highest frequency. Therefore at 2.5kHz the amount of space taken up by the woofer frames and surrounds must be no more than 5.4 inches, which is a fairly easy target.
Things get problematic in the higher frequencies; you can't use dome tweeters that have wide frames, for instance. Ribbons work well here due to their higher radiating plane to frame width ratio. Frameless domes also work well, aa do horn-loaded tweeters, since on a horn the radiating area is the entire horn mouth.
Well, anyone sufficiently quaified to challenge this assertion would by dint of that fact be an AES member and thus should be quite familiar with the literature that I'm referring to. If they have issues they would have to take them up with the authors of that literature.
But really all one has to do is to log onto the EAW/Martin/EV/JBL/McCauley or any of a dozen other sites that have specs on their line array systems and they'll see arrays that work quite well despite acoustic centers that are well over a wavelength apart.
Ok, gonna go with the 8" drivers. If I do 8 per tower that tower is going to be at least 70" tall, which is about 6 feet. Think I should go 10 per side so they'll be about 7.5 feet tall? That's going to almost touch my ceiling!
Can you guys give me some nice tweeter recommendations? Seeing I'm only paying $8 for the woofers I don't want to spend a ton of the tweeters, but I do want quality. I'm used to listening to my Polk LSis which have the Vifa ring radiator, and it sounds unreal. If I had the $60+ to spend per tweeter I'd go that route, but I obviously don't. So, which would you go with and how many would you get? I'd like to order the stuff ASAP and read while I wait on shipping. I know I have a TON of reading to do.
Thanks! Sorry for being so stupid
Can you guys give me some nice tweeter recommendations? Seeing I'm only paying $8 for the woofers I don't want to spend a ton of the tweeters, but I do want quality. I'm used to listening to my Polk LSis which have the Vifa ring radiator, and it sounds unreal. If I had the $60+ to spend per tweeter I'd go that route, but I obviously don't. So, which would you go with and how many would you get? I'd like to order the stuff ASAP and read while I wait on shipping. I know I have a TON of reading to do.
Thanks! Sorry for being so stupid
Perhaps something you can mount closely, like the Audax TM025F9.
It has a pretty smooth response, and could easily be crossed over @ 2.5K-3Khz from the Infinity's. And their on sale for $13.80 each, so you could put 8 on each side, using a crossover scheme like this (just using first and second row (2 and 6 drivers))
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It has a pretty smooth response, and could easily be crossed over @ 2.5K-3Khz from the Infinity's. And their on sale for $13.80 each, so you could put 8 on each side, using a crossover scheme like this (just using first and second row (2 and 6 drivers))
An externally hosted image should be here but it was not working when we last tested it.
I see how those tweeters could work well, but they're out of my price range
Can I get away with 4 tweeters, at listening level, or is it better to have them going as low and high as possible in the array, like the woofers? Remember, this is my first project and pretty much a test so I'd like to keep it reasonably priced. I'm only 23 and going to med school soon
Can I get away with 4 tweeters, at listening level, or is it better to have them going as low and high as possible in the array, like the woofers? Remember, this is my first project and pretty much a test so I'd like to keep it reasonably priced. I'm only 23 and going to med school soon
I'll have to take issue with Bill Fitzmaurice on his AES statement about the various researchers stating their driver to driver separation. This is a short list of AES references from individuals who design arrays for JBL and L-Acoustics:
[1] M. Urban, C. Heil,and P. Bauman, “Wavefront Sculpture Technology”, presented at the 111th AES Convention, New York, September 21-24, 2001.
[2] C. Heil, and M. Urban, “Sound Fields Radiated by Multiple Sound Sources Arrays”, presented at the 92nd AES Convention, Vienna, March 24-27, 1992.
[3] M. Ureda, “Line Arrays: Theory and Applications”, presented at the 110th AES Convention, Amsterdam, May 12-15,2001.
[4] J. Eargle, D. Scheirman, and M. Ureda, “JBL’s Vertical Technology: Achieving Optimum Line Array Performance Through Predictive Analysis, Unique Acoustics Elements and a New Loudspeaker System”, presented at the AES Convention, September , 2000.
[5] M. Ureda, “ ‘J’ and ‘Spiral’ Line Arrays”, presented at the 111th AES Convention, New York, September 21-24, 2001.
Other papers are out there as well who establish that the center to center spacing of line arrays should be no greater than a wavelength. In fact the L-acoustics engineers promote a well reasoned half wavelength or less criterion in their work. JBL uses less than a wavelength in all of their papers that I have read.
While you can design beyond these guidelines, the likelihood of success will be lower.
Additional line array technical papers (and some of the above) are on the JBL web site under www.jblpro.com (look under their technical documents on line arrays--JBL's Vertec line at :
http://www.jblpro.com/pages/tech_lib.htm
L'acoustics' web site list a few of the above papers if someone wishes to read more at:
http://www.l-acoustics.com/anglais/retdgb.htm
Bottom line is that I have yet to read any AES papers that support Bill's claims.
Perhaps he needs to print his list.
Jim
[1] M. Urban, C. Heil,and P. Bauman, “Wavefront Sculpture Technology”, presented at the 111th AES Convention, New York, September 21-24, 2001.
[2] C. Heil, and M. Urban, “Sound Fields Radiated by Multiple Sound Sources Arrays”, presented at the 92nd AES Convention, Vienna, March 24-27, 1992.
[3] M. Ureda, “Line Arrays: Theory and Applications”, presented at the 110th AES Convention, Amsterdam, May 12-15,2001.
[4] J. Eargle, D. Scheirman, and M. Ureda, “JBL’s Vertical Technology: Achieving Optimum Line Array Performance Through Predictive Analysis, Unique Acoustics Elements and a New Loudspeaker System”, presented at the AES Convention, September , 2000.
[5] M. Ureda, “ ‘J’ and ‘Spiral’ Line Arrays”, presented at the 111th AES Convention, New York, September 21-24, 2001.
Other papers are out there as well who establish that the center to center spacing of line arrays should be no greater than a wavelength. In fact the L-acoustics engineers promote a well reasoned half wavelength or less criterion in their work. JBL uses less than a wavelength in all of their papers that I have read.
While you can design beyond these guidelines, the likelihood of success will be lower.
Additional line array technical papers (and some of the above) are on the JBL web site under www.jblpro.com (look under their technical documents on line arrays--JBL's Vertec line at :
http://www.jblpro.com/pages/tech_lib.htm
L'acoustics' web site list a few of the above papers if someone wishes to read more at:
http://www.l-acoustics.com/anglais/retdgb.htm
Bottom line is that I have yet to read any AES papers that support Bill's claims.
Perhaps he needs to print his list.
Jim
mazeroth said:I see how those tweeters could work well, but they're out of my price range
Can I get away with 4 tweeters, at listening level, or is it better to have them going as low and high as possible in the array, like the woofers? Remember, this is my first project and pretty much a test so I'd like to keep it reasonably priced. I'm only 23 and going to med school soon
Well maybe the Onkyo tweeters are more in your price range. At $0.69 each you could afford 8 or so a side maybe? They have a pretty good response from 3Khz and up with the shield removed.
I don't think it will matter as much, as long as the line is relativlly center with the listening position. I think the Onkyo's above might be a better investment, since its your first like you said.
Also don't be frightened by the Big Boys around here. The only way you'll enjoy this hobby and help others is building stuff and getting your own "war stories".
My first real project didn't work out to well, they were trashed within a month
Actually my first project was a very long time ago, when I tried to recreate my parents BOSE acoustamass sub in junior high shop class. I didn't know a thing about anything. I used a cheap Radio Shack 8" woofer, a Radio Shack 2 way network (used the 2Khz low pass for the sub
). 1/4" Plywood, and the smallest enclosure I could make (hey those BOSE are small right, right?!?!?). It was utter trash....but it was fun 
PS: See Bill I told you someone would get defensive!!
driver spacing
Thanks for you input Jim. I agree. I could not find any doucuments that support Bill.
For mazeroth,
Here are 2 tweeters that would work well, but may be out of you price range.
The BOHLENDER GRAEBENER would work best with the 7 inch drivers because of its low crossover point.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=264-713
The second tweeter is less expensive.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=275-085
You should use about six of these per channel.
Thanks for you input Jim. I agree. I could not find any doucuments that support Bill.
For mazeroth,
Here are 2 tweeters that would work well, but may be out of you price range.
The BOHLENDER GRAEBENER would work best with the 7 inch drivers because of its low crossover point.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=264-713
The second tweeter is less expensive.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=275-085
You should use about six of these per channel.
Thanks for the motivation, Hybrid, and the input
This question is probably dumb, but I know, I'm a newb so bear with me!
Say I do (8) 7" woofers and do (8) tweeters, but the woofers I want to get 75% of the power...the crossover can handle this, correct? Maybe with some kind of resistor? God, I have TONS of reading to do, and I'm sick of reading with my schooling etc...
Also, can you recommend maybe a $2 - $3 tweeter? Thanks!
This question is probably dumb, but I know, I'm a newb so bear with me!
Say I do (8) 7" woofers and do (8) tweeters, but the woofers I want to get 75% of the power...the crossover can handle this, correct? Maybe with some kind of resistor? God, I have TONS of reading to do, and I'm sick of reading with my schooling etc...
Also, can you recommend maybe a $2 - $3 tweeter? Thanks!
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