2" Driver Line Arrays - How to Angle Parallel Drivers?

[NickJ]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Concave. It minimizes CTC distance for minimal combing.

I may be about to be schooled, but this seems wrong to me. Geometrically, as long as the acoustic center is actually centered on the XY planes and the depth of the cone remains a constant, the distance that sound has to travel forward to meet its "sister" signal should also be constant despite changes in the relative z-angle as it will be a function of cone radius and depth. You should be able to test this practically by putting the two drivers on a hinge and holding a piece of string on the dust cap of each driver. There should be minimal difference in tautness as long as the drivers only change angle on not distance. In addition, in the concave version (where the drivers are crossing over), the more energetic area of the sound waves will be interacting, and thus I would think more potential for larger gating effects. On the other hand, at a "tangent" the less energetic parts of the sound waves would be interacting due to poorer dispersion characteristics for larger cones, no?

Ok, educate away.

[mikec]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Thanks Bill.
Probably will require some pretty fancy router work to shave a 15 degree incline every-other driver space :D ...wondering how much improvement in the off axis I could expect to achieve .

Any better or add'l ideas out there?

If I were attacking the problem I'd go to my drill press and tilt the table to 15 degrees. Use a hole saw to cut the holes and Forstner bit to drill out the flange relief.

I'd also probably use a fly-cutter instead of the Forstner bits, but that's a bit hairy for folks who haven't used them before.

[duanebro]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Question from a novice -- since there's a limit on how close together you can put drivers, and if you get them too far apart there's other problems, is there a "not too close or too far" distance where you minimize the problems??

Closer the better. This is why they are using smaller drivers...

[mikec]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Question from a novice -- since there's a limit on how close together you can put drivers, and if you get them too far apart there's other problems, is there a "not too close or too far" distance where you minimize the problems??

[Organcat]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

"Would like to hear from other musicians who are using their arrays in live performances as their sole "PA system", especially if they've been motivated to a 2-way solution incorporating tweeters. I've been following John Murphy's project, know he uses his system for live music production, and chose not to incorporate tweeters, citing the concerns he had about crossover coloration...and also the fact that he was corner loading his solution, and therefore he didn't need to worry about anyone ever being more than 45 degree's off-axis."

I've just built a 14-speaker 9 lb line-array column for pro PA use with a DIY sub. I used buyout BMI hi-wave 2" full-range speakers and my horizontal dispersion is almost 180. No tweeters needed. I can't believe the results myself. Check out the projects on my page.

[billfitzmaurice]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Perplexing debate. For Live Music, how much I should be concerned about the off-axis equal dispersion of frequencies abov ~8Khz?

Good off-axis response to 12kHz is recommended. Above that the source material rolls off, mainly due to the range of dynamic microphones.

With it's Sonic Maximizer function engaged at only about 30%, and I can bear witness to the improvement in definition/clarity that it brings to our live performances.

IME marginal speakers sound better with BBE, good speakers worse. Take that for what it's worth.

I know lots of folks like to kick the BOSE engineers around. But did they take the "cheap route" to maximize profits...or did they simply decide there were very marginal returns in going the 2-way route, and instead put a few more dollars into tooling for the fabrication of the their enclosure that alternatively angles their 2.25" drivers?

The cheapest method is how Bose has always done it. Too much $ invested in building their products leaves less $ in the advertising budget, and they learned long ago that advertising is what sells, not 'better sound'.

[axes4less]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Perplexing debate. For Live Music, how much I should be concerned about the off-axis equal dispersion of frequencies abov ~8Khz? If I reference this Musical Instrument frequency chart....for the most part, the range above 8Khz is beyond the fundamental tones in most performances, and the range where we capture harmonics and definition (described as breath, air, sibilance).
http://www.independentrecording.net/...in_display.htm

I've seen several DIYer arrays, like your TLAH solution, with a long line of 1" tweeters, or planars, aligned beside their 3-4" full range drivers, but I have not yet had the opportunity to personally A/B them to the single driver arrays like I have been building.

I run a BBE X3 Crossover in my system to split between my subs and the towers, and I cross at 175Hz. With it's Sonic Maximizer function engaged at only about 30%, and I can bear witness to the improvement in definition/clarity that it brings to our live performances. So if incorporating a line of tweeters into the tower solution really does extend the off axis ability to hear those frequencies above 8khz better, I'd probably be equally sold that the extra cost would be worth it.

Would like to hear from other musicians who are using their arrays in live performances as their sole "PA system", especially if they've been motivated to a 2-way solution incorporating tweeters. I've been following John Murphy's project, know he uses his system for live music production, and chose not to incorporate tweeters, citing the concerns he had about crossover coloration...and also the fact that he was corner loading his solution, and therefore he didn't need to worry about anyone ever being more than 45 degree's off-axis. He's using the ND90-8 3.5 drivers. So maybe my 2" GENTOs are already achieving similar off-axis dispersion (tho' I know they are crap when you'd compare distortion measurements...what you get for $1.25 each).

So...I know lots of folks like to kick the BOSE engineers around. But did they take the "cheap route" to maximize profits...or did they simply decide there were very marginal returns in going the 2-way route, and instead put a few more dollars into tooling for the fabrication of the their enclosure that alternatively angles their 2.25" drivers? It's essentially the same quandary I'm asking as a hobbyist.....if I spend the money and the time, what are the chances that I'll decide later it was worth it? :D

[billfitzmaurice]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Thanks Bill.
So I'm back to the drawing board...sticking with a "single wide" tall array....and instead still trying to figure out how in my home woodworking shop I can design/cut a baffle that alternatively angles the drivers Left/Right about 15 degrees of each other...similar to what the current BOSE PAS solution does.

The reason they do so is that a 2.5" driver can't do well off axis above 8kHz, and rather than use a proper 2-way with tweeters they employ that offset. Why? Because it's cheaper that way.

[axes4less]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Sorry...Jim Griffin's paper only addresses some of this. The more extensive explanation of why hard-panning is important can be found on white papers written by the BOSE engineers that developed the PAS system.

[axes4less]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Having multiple arrays that are sending out the same source material would cause comb filtering problems at the points where their sound waves intersect. And....the performers and audience will lose the psycho-acoustical benefit of the "cocktail party effect". So things would actually be worse ....not better.

Unfortunately, I still constantly have to remind musicians I play with that it is actually BAD to have their sound split between multiple towers. It's much better to hard-pan to the tower that's closest to them...and have nothing coming out of the opposite tower. (We run LEFT and RIGHT towers for our band)

It's a common misunderstanding,.....a hangover from years of traditional PA systems and running stereo PA mains/monitors/backline amps etc. You have to reshape your mind :-)

If you don't understand these concepts...it's important that you learn. Go read Jim Griffin's white paper > http://www.audioroundtable.com/misc/nflawp.pdf

[DougP]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Double up on the number or arrays you are using. Go from 2 to 4 arrays. It also has the advantage of keeping the boxes lighter and easier to move.
Doug

[axes4less]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Thanks Bill.
So I'm back to the drawing board...sticking with a "single wide" tall array....and instead still trying to figure out how in my home woodworking shop I can design/cut a baffle that alternatively angles the drivers Left/Right about 15 degrees of each other...similar to what the current BOSE PAS solution does.
Probably will require some pretty fancy router work to shave a 15 degree incline every-other driver space :D ...wondering how much improvement in the off axis I could expect to achieve .

Maybe I just instead cut a single "veneer" board from 1/2" MDF at 15 degree angle....drill the driver holes...and then cut it apart into "shims" to glue in place (alternating angles) underneath the drivers ...which would thereby cock every other driver Left/Right.

Any better or add'l ideas out there?

[billfitzmaurice]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

the whole reason for exploring an angled baffle mount for the side-by-side 2" driver array was in hopes of achieving wider "quality" dispersion. If in doing so....I instead cause mid-high frequency SPLs to "beam" on axis....then any performer (or audience) who is ~30 degrees off-axis will be even more disadvantaged in what they "hear". ?

And there's the rub. Above the frequency where the drivers mutually couple dispersion of two drivers horizontally placed is half that of a single driver, so more often than not the result is the opposite of the intent.

[axes4less]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

Thanks for the replies.

I'm googling lots more articles...and starting to become more concerned about the effects of "beaming" by having the drivers 'side-by-side'. But everything I've read so far seems to support the advice to go with a concave vs. convex baffle mount....in that it would further shrink the c-t-c distance of the drivers and therefore further minimize comb filtering. Would appreciate further comments/advice on the "beaming" concerns. The whole reason for exploring an angled baffle mount for the side-by-side 2" driver array was in hopes of achieving wider "quality" dispersion. If in doing so....I instead cause mid-high frequency SPLs to "beam" on axis....then any performer (or audience) who is ~30 degrees off-axis will be even more disadvantaged in what they "hear". ???? So if this is a real concern, maybe I should dump the idea of parallel drivers in a column array altogether?
It is interesting to me that the BOSE column arrays never have side-by-side drivers...but the new solutions DO angle each successive vertical driver Left/Right several degrees.

R.e. the CBT...fascinating solution that I am enjoying learning more about. However, for the solution I am working on....which is portable sound reinforcement for live bands in small to medium size venues.....I don't think it is practical. Here's why > If I understand the solution correctly, the array must be curved as in the illustrations and photos I've seen so far. The club venues we play in Austin typically range from 1000-2000 sq ft...and the stage you have to set up on is sometimes as small as 16 x 24. So the ability to place tall/thin arrays directly against the back wall is a real advantage. A "C" shaped CBT array would simply take up too much space, let alone the complexity of moving it from gig-to-gig.

[bolland83]

Re: 2" Driver Line Arrays - How to Angle Parallel Drivers?

I would vote for concave, it would put the center of the drivers closer together thus minimizing the comb filter effect. I may be wrong about this but it would seem that the dispersion should be about the same in either configuration. The main difference being in driver center to center spacing.

Edit: Bill ^ and I must have posted a reply at the same time, haha!