I just can't get enough of OB line arrays and I dig the SPL. So here's the latest project that was inspired by the McIntosh XRT-29.
Each speaker will run between 32 and 40 PE Pioneer 4" drivers. I will series/parallel them into a 4-5 ohm load. This will make for two columns of speakers.
Q1 Would they be better separated into a line of four inchers, then tweeter line, and another line of four inchers...
>>OR<<
a line of four inchers, andother line of four inchers, and then tweeters?
Any stagger to the lines?
McIntosh separates their drivers with tweeters... ????
Q2 What would be the "optimum" width for the baffle? And the "inset" of the drivers from the edge.
Q3 Can you suggest a tweeter to keep up with all these 4" drivers. I have used the Onkyo close outs but prefer the Dayton PE-2 to avoid the wiring struggle. Price is a consideration. JohninCR has suggested the Pyle tweets. (I crossed at 5kH on the last two sets.)
Q4 Is there any convincing argument to box these? I like the crisp sound of the OB's I have constructed to date but I'm willing to listen.
Come one, come all. All you OBLA guys, let's hear it. I'm all ears.
(JohninCR... sorry but a horn is out of the question. No room for a 48 foot mouth!)
Each speaker will run between 32 and 40 PE Pioneer 4" drivers. I will series/parallel them into a 4-5 ohm load. This will make for two columns of speakers.
Q1 Would they be better separated into a line of four inchers, then tweeter line, and another line of four inchers...
>>OR<<
a line of four inchers, andother line of four inchers, and then tweeters?
Any stagger to the lines?
McIntosh separates their drivers with tweeters... ????
Q2 What would be the "optimum" width for the baffle? And the "inset" of the drivers from the edge.
Q3 Can you suggest a tweeter to keep up with all these 4" drivers. I have used the Onkyo close outs but prefer the Dayton PE-2 to avoid the wiring struggle. Price is a consideration. JohninCR has suggested the Pyle tweets. (I crossed at 5kH on the last two sets.)
Q4 Is there any convincing argument to box these? I like the crisp sound of the OB's I have constructed to date but I'm willing to listen.
Come one, come all. All you OBLA guys, let's hear it. I'm all ears.
(JohninCR... sorry but a horn is out of the question. No room for a 48 foot mouth!)
Chipco,
Why go to 32 drivers? 16 to 32 only gets you an additional 3db, the same as going from 1 to 2 watts. The side by side mounting will degrade the SQ. Floor to ceiling with 24 or whatever it takes, sure why not.
2 arrays per cab with the 2 lines angled away from each other is something I have wanted to try with the idea being to create a giant "sweet spot". That kind of thing is done at concerts, but I'm uncertain how comb filtering comes into play with the lines being on different planes. I believe it may not be a factor since the frequencies would be above the baffle step point.
Another idea is to use the extra drivers to make some bass. 40 drivers with the main array being 16 drivers. Wire the 16 next to those plus 2 topmost and bottomost pairs separately as your bass only drivers. Biamping would be best. Just use on of those $30 Tamps from Target online. You'd need a rumble filter to block out below say 30-35hz to protect from over excursion. Then start a low pass filter of 18db per octave starting at the same point to flatten response, since you are using them below Fs.
If you go sealed with those 24 bass drivers, you should definitely
get some reasonable bass. Same thing as above except a 12db/octave slope on the low pass filter to match the driver roll off below Fs. I may also prove easier to match the phase difference with the 12db slope xover. This may prove to be an even better option than my horn idea, because the drivers are cheaper than wood and you don't have to give up OB for the main drivers. Add a 3rd line of 20 for bass, then you can lower the extension and probably make a subwoofer unnecessary for most music, or make it all OB. 44 drivers for bass is like 2 18's, so the 1mm excursion may be sufficient for some solid dipole bass.
Also, putting a high pass filter on the main 16 at 100hz will reduce alot of strain put on them running full range, so they can go much louder than your existing array.
This idea is so appealing to me that I'm going to add an array of sealed drivers in a triangular box on the back side of a V shaped OB array pair that I've been wondering how to improve.
Regarding the corner horn; the width of the mouth opening is less than a foot and you can use the wall to form the final flare and have a cab that has a 6" wide front, 15" deep, 13" wide at the back. I don't know where you got the 48ft mouth. 50hz turned out to be the pratical limit. 40hz used up 70% of excursion at 1 watt. Floor to ceiling would make 40 very practical though. No wider on the horn, just taller. Just something to keep in mind for your 3rd project. Let me make one I'm happy with first.
Why go to 32 drivers? 16 to 32 only gets you an additional 3db, the same as going from 1 to 2 watts. The side by side mounting will degrade the SQ. Floor to ceiling with 24 or whatever it takes, sure why not.
2 arrays per cab with the 2 lines angled away from each other is something I have wanted to try with the idea being to create a giant "sweet spot". That kind of thing is done at concerts, but I'm uncertain how comb filtering comes into play with the lines being on different planes. I believe it may not be a factor since the frequencies would be above the baffle step point.
Another idea is to use the extra drivers to make some bass. 40 drivers with the main array being 16 drivers. Wire the 16 next to those plus 2 topmost and bottomost pairs separately as your bass only drivers. Biamping would be best. Just use on of those $30 Tamps from Target online. You'd need a rumble filter to block out below say 30-35hz to protect from over excursion. Then start a low pass filter of 18db per octave starting at the same point to flatten response, since you are using them below Fs.
If you go sealed with those 24 bass drivers, you should definitely
get some reasonable bass. Same thing as above except a 12db/octave slope on the low pass filter to match the driver roll off below Fs. I may also prove easier to match the phase difference with the 12db slope xover. This may prove to be an even better option than my horn idea, because the drivers are cheaper than wood and you don't have to give up OB for the main drivers. Add a 3rd line of 20 for bass, then you can lower the extension and probably make a subwoofer unnecessary for most music, or make it all OB. 44 drivers for bass is like 2 18's, so the 1mm excursion may be sufficient for some solid dipole bass.
Also, putting a high pass filter on the main 16 at 100hz will reduce alot of strain put on them running full range, so they can go much louder than your existing array.
This idea is so appealing to me that I'm going to add an array of sealed drivers in a triangular box on the back side of a V shaped OB array pair that I've been wondering how to improve.
Regarding the corner horn; the width of the mouth opening is less than a foot and you can use the wall to form the final flare and have a cab that has a 6" wide front, 15" deep, 13" wide at the back. I don't know where you got the 48ft mouth. 50hz turned out to be the pratical limit. 40hz used up 70% of excursion at 1 watt. Floor to ceiling would make 40 very practical though. No wider on the horn, just taller. Just something to keep in mind for your 3rd project. Let me make one I'm happy with first.
JohninCR... fancy seeing you here.
Not so fast John. I get to and from on the short bus.
Q1 What's a tamp from Target online?
Q2 Why include another 4 drivers from the line in the "bass array"?
Q3 A fellow could build a box with a plate amp right. You aready have he rumble filter built into the plates already.
Q4 The Pioneer 4" is down to 80dB at 80Hz. Why filter out the rest. Can't it roll off on it's own?
Q5 I just want to understand you correctly... A triangular box is a box with 5 sides, right?
Q6 What would the box volume be for 40 of those drivers?
Not so fast John. I get to and from on the short bus.
Q1 What's a tamp from Target online?
Q2 Why include another 4 drivers from the line in the "bass array"?
Q3 A fellow could build a box with a plate amp right. You aready have he rumble filter built into the plates already.
Q4 The Pioneer 4" is down to 80dB at 80Hz. Why filter out the rest. Can't it roll off on it's own?
Q5 I just want to understand you correctly... A triangular box is a box with 5 sides, right?
Q6 What would the box volume be for 40 of those drivers?
Straddling the tweeter line
I believe that you can get away with building two midbass lines on either side of a central tweeter line if you splay the midbass lines outward An angle of about 30 degrees to each side of the tweeter line would be a good starting point. This will give a fairly wide and uniform radiation pattern to the net three-driver array, and the horizontal symmetry would mean less tonal balance shift as you move side-to-side. The directionality inherent in the midbass drivers would cut down on comb filter effects, as the two sets of midbass drivers would be angled 60 degrees relative to one another.
I've never done this with line arrays, but it works on a more modest scale.
I believe that you can get away with building two midbass lines on either side of a central tweeter line if you splay the midbass lines outward An angle of about 30 degrees to each side of the tweeter line would be a good starting point. This will give a fairly wide and uniform radiation pattern to the net three-driver array, and the horizontal symmetry would mean less tonal balance shift as you move side-to-side. The directionality inherent in the midbass drivers would cut down on comb filter effects, as the two sets of midbass drivers would be angled 60 degrees relative to one another.
I've never done this with line arrays, but it works on a more modest scale.
1 to 2 litres each gives you a Q of 1-1.2 , a bit high. In your case, I'd design it to try OB first, with say a 6" deep divider between the bass units and the main array. If the OB doesn't get satisfactory bass, then first try quasi Aperiodic with 2" then 4" of foam rubber stuffed in behind the drivers. If that doesn't give you enough, then seal it up.chipco3434 said:
What's critical is that the tweets be mounted frame to frame and that the two array heights are close to the same so that they have the same radiation characteristics at the crossover.
It doesn't work. Wherever you're in the field of both lines you have combing based on the pathway differential. Crossfiring the lines does work up to the frequency where the distance between radiating planes is a half-wavelength, above which response rolls off.
No, it gets you 6dB if you parallel wire, 0 dB if series, and which you do depends on where you're trying to go impedance wise as well as sensitivity wise. With 8 ohm drivers of 85dB sensitivity an array of 16 would give about 97dB sensitivity at 8 ohms, 32 would give 103dB at 4 ohms.
The lower the frequency the less space efficient a line array is, not to mention less cost effective, as the drivers get larger and more expensive. At about 80 Hz the size/cost advantage switches from an array, which can use very cheap drivers, to a folded horn, which can get the requisite SPL from a single moderately priced driver.
That's more or less true, and if you've got a listening room that's very short and very wide with audience well to either side of the speakers that could be worthwhile, though as noted above there's going to be serious combing where the soundfields overlap. By and large -6dB at 30 degrees off axis is quite adequate and a single line of four inchers will give that up to 6kHz no problem.
Absolutely, which is precisely why I did mine that way.
Both. You want each driver of the two lines frame to frame,or as close as you can get to that, to properly integrate their outputs into a single wavefront. You want the two lines as close as possible to each other to minimize combing where their outputs overlap. Also use at least 3rd order filtering for the same reason, to minimize the frequency overlap range. Your sitting and standing positions should lie within no more than 5 degrees off the vertical axis either below or above the line, but with one this big that's a mighty big sweet spot.
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With "frame to frame" he's saying that with arrays of tweeters, they need to be as close together as possible. With many tweeters that still isn't close enough due to the width of the frame.
Of course there are easier ways to get bass, maybe not more cost effective, but easier. $16/side worth of larger woofers isn't going to get you even close to keeping up with your main arrays. I thought Chipco wanted to use 40 drivers anyway. Another benefit is that the "woofer" array is going to pick up at least some efficiency from the line array effect despite the fact that your listening position probably won't be in their near field.
My thought process of dual angled lines was exactly for a wide room. Narrow rooms don't need it, because the much lower effect of distance on arrays makes you more able to hear both speakers when off axis to one side. I planned to place the lines very close together and use narrow dispersion tweeters to eliminate overlap at the point comb filtering comes into play.
Of course there are easier ways to get bass, maybe not more cost effective, but easier. $16/side worth of larger woofers isn't going to get you even close to keeping up with your main arrays. I thought Chipco wanted to use 40 drivers anyway. Another benefit is that the "woofer" array is going to pick up at least some efficiency from the line array effect despite the fact that your listening position probably won't be in their near field.
My thought process of dual angled lines was exactly for a wide room. Narrow rooms don't need it, because the much lower effect of distance on arrays makes you more able to hear both speakers when off axis to one side. I planned to place the lines very close together and use narrow dispersion tweeters to eliminate overlap at the point comb filtering comes into play.
chipco3434 said:
If you are happy with your high frequencies in the current setup, just fill the rest of the baffle with 4"s filtered only to play bass. The gaps for the tweeters will make 0 difference.
If your amp can handle lower a lower impedance load, allocate more power to the woofer array by wiring them with a lower impedance. You probably can't get to subwoofer type bass output, but you can surely fill out the bottom end than what your getting now, but done properly new amps may be unnecessary.
My array friend Dmitri uses 32 drivers sealed and 64 drivers OB using 4" drivers as single subs down to 30hz or so for his OB arrays. I think it would be very worthwhile to try, especially if you already have a bunch of the NSB's
I see what you did with the tweeters, on for sitting, one for standing. Fill the open area between them with more pt2s and it will work a lot better. The distance between them is enough to minimize combing but you're not getting a nearfied condition or intergrated wavefront from them while you are from the midbasses. I suspect that the SPL of only two pt2s is way short of the midbasses as well.
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