New line array project...need recomendations.

[chipco3434]

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!)

[BillFitzmaurice]

Having two midbass lines straddling a tweeter line will lead to serious comb filtering. Leave it at one midbass line and one tweeter line. As for tweeters the new Dayton ND20TB looks promising for LAs.

[chipco3434]

Fitz, thanks for your input. How many tweets would be required to compliment the woofer line?

[johninCR]

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.

[chipco3434]

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?

[Alidore]

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.

[johninCR]

Originally posted by chipco3434
JohninCR... fancy seeing you here.
Chip,
I can't help myself, I love arrays. Something I didn't bring up earlier is that you should try power tapering for improved imaging.

Not so fast John. I get to and from on the short bus.

Q1 What's a tamp from Target online?
This one http://www.target.com/gp/detail.html...sin=B00009W44B
Before I found some other sources even cheaper. It uses the 15 watt per channel Tripath amp and sounds great not even considering its price.


Q2 Why include another 4 drivers from the line in the "bass array"?
16 gives you enough output from 100 up. For the bass, you need as many drivers as possible.


Q3 A fellow could build a box with a plate amp right. You aready have he rumble filter built into the plates already.
That can work. Probably more expensive and more power than you need.


Q4 The Pioneer 4" is down to 80dB at 80Hz. Why filter out the rest. Can't it roll off on it's own?
Yes, but they are struggling trying to play the low frequencies. They'll sound better in their range if you don't let them play it. You'll also probably have a phase issue with a filter on only the bass portion.


Q5 I just want to understand you correctly... A triangular box is a box with 5 sides, right?
That's for my V shaped baffle (wings back about 60 degrees). No just 3 sides, a separate box in the back firing backwards unseen. Triangle to match the wings and not affect the rear radiation of my OB array. It would fit in behind my current wings. Below 100hz is not a big deal to fire backwards.


Q6 What would the box volume be for 40 of those drivers?

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]

T-amp.... The miracle of Opamp technology!

John, I'm glad I read your posts today. Now, I'm incrementally smarter than at 6:30AM. Thanks for the ideas!

The angled baffle would do nice to fill the room. Good ideas.

[chipco3434]

With an Fs of 105, isn't reasonable bass a lot to ask from these drivers? Wouldn't that be better handled by a real sub?

[BAM]

Yeah, get something like the Parts Express 8" Shielded DVC woofer and the 70 watt plate amp, and put one per side in a vented box.