Angling drivers left and right in a vertical line-array????

[ozziozzi]

Can anyone explain the disadvantages or possible problems if I splay out small wide-range drivers either side of straight ahead in a short or long line array? I appreciate that line arrays produce cylindrical wavefront, but I was hoping for better frequency response over a wider angle.

Best example I could find came from Elliot Sound Products hybrid ESL isobarik bass loudspeaker. http://sound.westhost.com/projects-b.htm where designer has splayed out four ESL panels to increase dispersion. In my case, 3" midranges will be mounted OB in vertical array like Fostex "tallboy" design, but probably more mid drivers (6-8) each channel. I could also angle ribbon tweeters in same way. Finished units are for stereo and 2.1 movie sound with external sub.

I posted this question previously in fullrange forum, received 121 views, but 0 suggestions. I hope posting in this wider forum is OK.

ANY comments welcome.

[Saturnus]

You get interference and cancelation problems. Meaning the dispersion will vary greatly with frequency and angle.

Best advice is not to it although it depends on distance between drivers and what frequency band each covers.

For example many professional line arrays are made up of many individual MTM speakers stacked vertically with the tweeters directly above eachother. These are often individually angled away from eachother.

[LineArrayNut]

personally, I would not do it.

http://diy-audio.narod.ru/litr/nflawp.pdf

[ozziozzi]

Yes, I have read Jim Griffiths White paper, but I don't recall anything about drivers having to be all pointing straight ahead. I am only thinking +/- 40degrees off-axis (maximum). The drivers i intend using are 3" which should go pretty high without combing effects--I intend building the array and then looking up suitable XO point to ribbon tweeters. JG spent a lot of time discussing center-to-center spacing of drivers WRT wavelength/crossover freq to minimise combing and I intend following his guidelines re minimum center-to-center spacing.

BTW the link you quote to the NFLAWP is a dead end.

Unless Dr Griffiths personally intervenes in this thread I guess I will just "suck and see" what happens ie: how they sound as i walk around the room. Altho it would be interesting to hear from someone who has actually tried something similar to what I propose.

[Jim Griffin]

I don't know "Jim Griffiths" but the Jim Griffin line array white paper is now located at:

http://www.audioroundtable.com/misc/nflawp.pdf

My opinion is that you should not splay the drivers in a line array. For the referenced Elliot Sound Products design remember that ESL panels often have narrow horizontal dispersion so for them splaying may help widen thier dispersion. If you using normal dynamic drivers and either planar or ribbon tweeters, you will have enough horizontal coverage so that a splayed configuration isn't needed. Hence, Saturnus' advice is right on.

Jim Griffin

[Pano]

Thanks Jim, for posting that. It's been a while since I've read it and had lost track of it. Now safely stored on my computer. =)

Speaking of angled drivers and that sort of thing. The very first "Hi-Fi" line array I heard - about 25 years ago - used a vertical pole in front of the drivers. It was a wooden pole about the size and shape of a closet pole or handrail. Sitting a few inches in front of the center line of the drivers on standoffs.

The idea was supposed to be that the pole would help form a better cylindrical wavefront. Since I had not heard it without, I asked how well it worked. The only answer I got was a shrug of the shoulders.

Never seen another like it. Was this ever used on other line arrays? Does it do more harm than good?

[LineArrayNut]

Originally posted by ozziozzi


BTW the link you quote to the NFLAWP is a dead end.

you just have to learn to internet.

click the blue hyperlink in the middle of the page.

poof!

you get a pdf.

http://diy-audio.narod.ru/litr/nflawp.pdf

lol

[ozziozzi]

Re: broken link: The LAST time I clicked on link (about a week or so ago) I received a not known at this address. THIS time I see the link to pdf of Dr Griffin's paper on the Cyrillic language site. As you can see from my Author box I have been on this forum since 2006 and on the internet since dialup modems. I think I can recognise a broken link when I see one.

My apologies for mis-attributing the NFLAWP article to Dr Griffiths. I can only blame not checking back to the original article. No offence intended.

Jim, if I read your reply correctly, you are saying that splaying drivers "in your opinion" is not necessary with (say) 3" wide range drivers and planar tweeters as the dispersion will be OK.
" using normal dynamic drivers and either planar or ribbon tweeters, you will have enough horizontal coverage so that a splayed configuration isn't needed. Hence, Saturnus' advice is right on."

I value all previous posters advice, but what exactly does JG mean by "enough" dispersion. Is the horizontal dispersion of a LINE of drivers less than, more than or the same as a single WR 3" driver? Is the sweet spot any wider? Would angling the drivers **destroy** the other line-array advantages? I appreciate Dr Griffin's contribution to the field of NFLA speakers, but I am just trying to "tweak" his ideas a little. I thought that was the spirit of DIY.

[ozziozzi]

Thanks Panomaniac, I appreciate your recollection about the pole in front of drivers. It's a pity the person you referred to had not removed the pole to see if it WAS actually an improvement.
I believe that there have been many individual or corporate experiments like that lost to later generations. Sure, some might have been a waste of time, but others could be useful ideas worth pursuing.

Saturnus, re: pro line-arrays. Thanks for your comment. I think the curved vertical line arrays seen in concerts are mainly to get uniform sound level (at all frequencies) to front, middle and rear of audience in large venues and they usually work well. My suggestion is similar in concept.

Cheers Ozziozzi

[Jim Griffin]

Some comments on your questions:

The horizontal dispersion in a line array is determined by the dispersion of the individual drivers used. In a vertical array you have tailored the vertical dispersion but you have not distrubed the horizontal direction (I am assuming that you have all drivers in a vertical line). Hence, you can expect the same horizontal dispersion from one or a hundred of those 3 inch drivers.

I find that the sweet spot in the line array near field is enhanced. You experience a more gradual sound fall-off as the composite sound includes both horizontal and vertical axes components. The line array image appears to be wider than that for point source drivers.

Again, horizontally angling the drivers in a line array isn't necessary and in my opinion will disrupt the sound for a listener who moves about the room. You likely would be able to sense variation in the sound as you wander around the room if you had an array with every other driver angled.

The reason that pro sound line arrays are skewed in their vertical axis is because they perform in both their near field and far field regions. The curving of the array is used to better cover the audience front to back. You notice that no attempt is made to alter their horizontal dispersion whatsoever.