SLA DJ/Pro style

[guitarhiker]

Thanks for the clarification Bill. That makes more sense to me. I went back and looked at the charts in the Bose white paper and their rhetoric in the document as you say does not match what their charts show in the top two octaves. I guess the remaining question I have then is . . . do smaller drivers tend to give wider dispersion in general as Bose seems to claim eventually settling on a 60mm "full range" driver for their newer arrays? Of course Roger Russel uses the slightly larger 70mm auras on his array -- which by the way are on closeout on Madisound although still a little pricey if you are going to buy the quantities he uses. When I map out the floor plan of the church where I am at and think about other places I would need a small portable setup it really would help simplify speaker placement drastically for a portable system to get above 110 degree dispersion if that is possible. I guess I could go back to the cross-firing idea but from the comments I am a bit leery of the potential combing. Any other suggestions would be greatly appreciated. If I wasn't so lazy I would build a cab with the speakers on the same center axis in rotation but what a bear time-wise to create that kind of front on a cabinet.

[Bill Fitzmaurice]

do smaller drivers tend to give wider dispersion in general as Bose seems to claim eventually settling on a 60mm "full range" driver for their newer arrays?

All drivers eventually get to the point where they're too big and the radiation pattern is too narrow. At the other end of the scale the smaller the driver the less the displacement, and that means less low frequency output. To achieve a reasonable balance between low frequency output and high frequency dispersion one must use no less than two drivers in the 100Hz to 15kHz bandwidth, there's just no two ways about it. The Bose driver will neither go very high with good dispersion nor very low with good output, and thus the source of the phrase Got no highs, got no lows...must be Bose.

[guitarhiker]

That makes sense . . . I guess for my purposes staying with as small a driver as I can (maybe 3.5 to 5 depending on specs) and still get down to 73hz for the low D makes the most sense, and then maybe a dome tweeter array more akin to the standard SLA/TLAH for a little wider dispersion, or better yet go for a v array of piezos although I might have to attenuate them a bit for balance with the decreased sensitivity of most smaller drivers. May have to order your dr200 plans to get the scoop on the V array. Wanting to build some of those or maybe the 250's anyway for an annual outdoor music festival we started last fall at the church . . . we were seriously underpowered but got by for our first attempt with six Behringer powered cabs. Sometimes you just have to use what you have access to and with just a few hundred folks it was okay (sort of) but we need to take things up a notch this year as we are expecting to triple our numbers.

[Steve Regier]

Are you looking to build a cab for backline use or FOH? It seems that you may be overthinking things a bit. Combining aspects of designs can be dangerous. You can very quickly end up with very poor results. Ewetho and I built many of Bill's cabs before we wandered off and built the one at the begining of this post. I would suggest you build a single SLA/PRO exactly to Bill's specs with the 6 tweet option. Try it and see how it performs.

However, If you must build something "Off The Reservation", let me fill you in on some of our experiences. We built the original SLA's for Ewetho's home theatre. They were so impressive; by impressive I mean smooth and accurate with excellent off axis response and great imaging. We had some 5" MCM mid-bass drivers laying about so we decided to see what would happen if we made a larger SLA with those. We used the same Goldwood tweets as in the standard SLA. We called this model the SLA Extreme. You can see it in the picture below next to our test model of a boolshelf SLA. We found that the 12 tweets were a tad bright against the 6 - 5" bass drivers but a minor dab of EQ brought the cab in line. The next idea was to move a bit more air and even out the cab so we went to the 6" Mid-Bass drivers. These were a perfect match to the 12 tweets. The cab at the begining of this post has the identical sound characteristics as the original SLA just louder and with a larger sound front. We compared them to my Otop15's with melded arrays. The large SLA (we call it the 612) has a much flatter response and needs almost no EQ. It also has a sweeter sound than the Otop15. The Otop gets louder on less power but at 400 watts the SLA is in the 120Db realm so we are happy. The Otop15 melded and the SLA are very similar in off axis response with the Otop having a slight edge but not enough to be a deal breaker. We like the large SLA for indoor use due to it's pattern control and sweet even sound. Watch and listen to the video from Radian at the beginning of this thread. We use the large SLAs for FOH, Back Line and Monitoring. The Otops are now strictly for Outdoor use (we use 2 per side stacked).

Bottom line: Build a large SLA, I STRONGLY suggest Bill's design at least to start. You won't be disappointed. Then if you want/need more just build more SLA/PRO's and stack or spiral stack as Bill has suggested.

Let me also address your idea of one large cab. I too thought this way. I built the largest cabs Bill had for my purposes and figured one large cab is best. I WAS WRONG. After hearing Otop12's at our listening party, for instance, I see the flexibility and brilliance of Bill's designs. Today I would not have built my 4 Otop15s. I would instead build 6 or even 8 Otop12's. The same goes for my Tuba subs. Today I would and will build Tuba 24's in quantity not Titan 48's or Tuba 36's or 60's. You are better off with many scalpels than a single sledgehammer until you get outdoors.

[guitarhiker]

Me . . . over-think . . . never! Of course my teenage daughter says she has me to thank for her tendencies toward anal-retentive OCD behavior at times!

I played around the last couple of days with an small 3.5in 8 driver test array -- 1300 cu in cabinet tuned to about 75hz -- total cost about $25. It actually sounds better on vocals with a little Stewart PA50B amp than the tri-amped system with 5 crown amps at our church which they spent thousands on when the new building was built about seven years ago. It still seems to have too much vertical dispersion though, so if I am going to use that small a driver it needs more like 16 which would put it close to 60" high but it would be very light. Of course it rolls off in the top octave with no tweets, but with my old Peavey Autograph II and RTA mic it was pretty easy to get a smooth response -- just had to roll everything off from 63 down to not overextend the little drivers.

I get what you are saying and I'm not wanting to build a huge cabinet, just a taller one. In looking at your "big sla" with 6 drivers that's more what I am thinking and I like the idea of it not needing much eq. Regardless, it will be fun to play around with and the ideas I have gotten here on the forum and from Bill's plans are very helpful. As far as the melded V array -- it just looks fun to build and I don't need dr200's or omni top's till the festival late next summer so I thought it might be fun to add that into an sla or tlah although it might be a tight squeeze to fit it in with 6" drivers. For the festival I definitely buy into the several small cabinets idea -- going to have to order those drw200 plans or maybe just break down and get Bill's CD. For the acoustic stuff that I do one portable cabinet will cover it -- more of the back line cabinet idea of the Bose L1 but without the ridiculous expense. With the variety of inexpensive EQ's with RTA that are out now no one needs to pay for their proprietary eq-ing of otherwise non-remarkable speakers. In fact the little test cabinet covered well, but I had to raise it up about two feet and so I might as well make a cabinet in that height range rather than carry a stand as well. It didn't quite cover the very ends of the first two or three rows of seats -- maybe 100 degree dispersion with reasonable fidelity from what I know of the room measurements and where I had placed it. However, when doing the youth choir stuff in the summer I certainly would need a second cabinet, and in that setting the bigger sla would be the better plan over the small drivers.

As good as the little test box sounded in the sanctuary a couple of TLAH cabs with the subs already there would be fantastic. Maybe even pull the drivers from the big sub box and rebuild it into a tuba or titan configuration for increased efficiency. The 10" mid drivers and horns could go into the first couple of DRcabs for our festival. Too many project possibilities to play with . . . .

Thanks again for everyone's input. My daughter thanks you for feeding my neurosis as well! At least I'm not a germaphobe too like Monk!

[Tom Smit]

Get the CD!

[Mikey]

Guitarhiker, I have eight Dayton PA165-8 6" PA Drivers, new-in-box, looking for a good home in SLAs or TLAHs. Only $100 + shipping. See the For Sale forum if you're interested.

[guitarhiker]

Not sure if this is the best place to post this, but I was wondering in pro-sound applications as opposed to home theater is there any reason to do power tapering via the wiring sequence when using 8 or more drivers as in the Griffin white paper on line arrays?

[Bill Fitzmaurice]

Not sure if this is the best place to post this, but I was wondering in pro-sound applications as opposed to home theater is there any reason to do power tapering via the wiring sequence when using 8 or more drivers as in the Griffin white paper on line arrays?

Power tapering is a necessity when the listening distance is too short for the height of the array used. Some believe that an in-home line array should go from floor to ceiling; I'm not one who does. If you do so some sort of compensation must be used to account for pathway differentials, either mechanical (array shape) electrical or both.
In pro sound one's very unlikely to be close enough to the array for power tapering to be required.

[guitarhiker]

That was kind of what I thought but wasn't totally sure. Thanks for the clarification!

[David Sample]

Very interesting thread guys, thanks for the great back and forth!

[netwerks]

Ar

You are better off with many scalpels than a single sledgehammer until you get outdoors.

+1 especially in smaller rooms with notes and cancellation. That way you have more options to even out the coverage.

[ewetho]

Thought you might like to see NUMBER TWO.....

We now have a Right and Left and plan to use them in lieu of the OT15s for a school dance on Saturday.

[ewetho]

Minor finishing to go but they go to war Saturday Night!!!

Hat for the pole mounts are in and cab has been to war volume!

[setzer808]

Can't wait to hear how they performed at the dance!

I built some DIY line arrays last year around the time I built my T18 and love the sound of both together...however my arrays are only using the little 3x5 JVC's. I would love to build a pair of pro arrays.