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[Antone Atmarama Bajor]

     I was thinking about the idea of Using LAB Subs/BT7's (Almost the Same thing) in horizontal Line Arrays.

    I've been playing with the old array show software trying to simulate a line of LABS/BT7's using 4 Clusters of 2,  and delaying the outer clusters to widen the radiation pattern.

     Its seems fairly promising except that I cant see any predictions bellow 50Hz.

    It would seem that this would give superior LF Dispersion (No Power Alley) than having a 4X2 Cluster on either side of the stage (Outdoors at least).  Has here anyone tried this with either the LABS or the BT7's?

    I'm assuming that LF extension would be better if 16 Cabs are used rather than 8 but that would force the stage height to be no less than 45".

    I don't have any fancy Sound Webs or anything like that to play with but I have heard Phase shading with All pass filters can work better than hard Delay.

    I guess the only way to know for sure is to try.

Antone-

[Iain_Macdonald]

Antone Atmarama Bajor wrote on Thu, 04 May 2006 19:16

I was thinking about the idea of Using LAB Subs/BT7's (Almost the Same thing) in horizontal Line Arrays.     I've been playing with the old array show software trying to simulate a line of LABS/BT7's using 4 Clusters of 2,  and delaying the outer clusters to widen the radiation pattern.      Its seems fairly promising except that I cant see any predictions bellow 50Hz.     It would seem that this would give superior LF Dispersion (No Power Alley) than having a 4X2 Cluster on either side of the stage (Outdoors at least).  Has here anyone tried this with either the LABS or the BT7's?     I'm assuming that LF extension would be better if 16 Cabs are used rather than 8 but that would force the stage height to be no less than 45".     I don't have any fancy Sound Webs or anything like that to play with but I have heard Phase shading with All pass filters can work better than hard Delay.     I guess the only way to know for sure is to try. Antone-

Hi.

One of my favourite subjects.

This has received extensive coverage in the lab. Also there is a tutorial from Pat Brown from SynAudCon on Bessel Arrays. This can be found in "Study Hall" You can also have a look at this paper from Don Keele on Bessel Arrays. It's #21 on:http://www.dbkeele.com/papers.htm

Arrayshow is fine for modelling this stuff. I find that using one of the LF Boxes gives a more realistic result than the point source. You do need to consider if there are any major boundaries nearby that might reflect back to the array. My understanding is that <50hz would have required a lot more programming etc. Don't hold your breath for any upgrades, because Mark Ureda is now with Harman/JBL.

Why not sign up for Mapp online from Meyer. Again it's free and you can introduce boundary conditions.http://www.meyersound.com/mapponline/

Have a look at this link http://www.meyersound.com/news/2004/isle_of_wight/
Yes it definitely worked. Power ally dissapears.

Whilst you are modelling with arrayshow you can also try a combination of the line and cardioid blocks.

Yes you can use allpass filters they do marginally improve the end result. But usually the use of the line and/or a cardioid solution makes such a difference, that the lack of allpass seems trivial. You also need to consider whether you are introducing a bumpy phase response and compromising the crossover to the rest of system. Remember if you do the line, then it will work just like a line array on its side.

I would suggest that you try a cardioid array to start with, using those custom subs you built. Nice and simple, but the difference on stage can be dramatic.

Have fun.

Iain.

[Antone Atmarama Bajor]

     Is there A database of devices for Array Show.  I only have one EV box available.

    I have been trying to simulate the horn BT7's By giving the Horn Mouth Several points placed equally appart, apart the seams between clusters I would set a point and apply half the delay that is applyed to the outer cluster.

    Very Tedious with Array Show.  It could use more automation features thats for sure.

    Trying to figure out Xover attenuation between drivers is fun.

Antone-

[Antone Atmarama Bajor]

     I've been playing with The Meyer MAPP software.  I'm not sure that any of their cabinets will accurately represent the BT7 or LAB Sub (I've used the M3d Sub and M2d Sub).

    I've tried making arrays of similar size as the 8 BT7/LABs.  And compare the polar response to what Array Show Predicts and the Lobing is certainly different.  I'm thinking that a horn sub may be more accurately represented as a Large point source.  

    I've been trying to model it as 3 points (Horn Pair Center and half way points from center).  I've also been considering the junction between pairs a point source.  If delay is applied to the adjacent pair I have been splitting the difference and applying half the Delay.

    I don't know if there is a more accurate method of modeling the BT7/LAB I'd like to know.

    I'm shooting for predicting outdoor response so I'm not hugely concerned with reflections at the moment.

    Has anyone here actually played with Horizontal Horn Sub Arrays?

    It sounds like they where quite successful with the m3d subs at Isle of White.

    Building a cardioid sub sounds like fun but I don't have enough space or BS-212 to do that right now except as an experiment.

Antone-  

[Iain_Macdonald]

Antone Atmarama Bajor wrote on Thu, 04 May 2006 23:56

Is there A database of devices for Array Show.  I only have one EV box available.     I have been trying to simulate the horn BT7's By giving the Horn Mouth Several points placed equally appart, apart the seams between clusters I would set a point and apply half the delay that is applyed to the outer cluster.     Very Tedious with Array Show.  It could use more automation features thats for sure.     Trying to figure out Xover attenuation between drivers is fun. Antone-

Hi Antone,

This link will give you all that is available. http://www.electrovoice.com/Electrovoice3/files.nsf/Download sByFile?OpenForm&typeoffile=ArrayShow

I have been trying to simulate the horn BT7's By giving the Horn Mouth Several points placed equally apart, apart the seams between clusters I would set a point and apply half the delay that is applied to the outer cluster

I am confused. Are you doing a spaced line or a Bessel array? The spacing should be single boxes with equal spacing. That works the best in my experience. Yes you can vary delay at the ends but you are going to compromise something else. Xover to the rest of the system can end up being a problem. Though, no more than with a vertical line array and floor subs !!.

Very Tedious with Array Show.  It could use more automation features that's for sure.

Have inquired, but no hope of any developments. Mark Ureda the author, is now with Harman/JBL.

Has anyone here actually played with Horizontal Horn Sub Arrays?

Yes. They work fine if you set them up properly. Power ally is non existent. One thing to remember, is that bass at the sides is very low. Do remember that you might have people at the side of the arena/field. These can often be VIPs or guests. Check that they have enough sub or you might get complaints. I was experimenting with these concepts back in 1987 ! Along with Jim Cousins (now at Martin Audio), Simon Johnstone (ambassador of calm at d&b). Plenty of others have used this in Europe and the States.

While you're looking at different array configurations. Try modelling an end fire line array. These work well in smaller venues. But you still get power ally if the cluster is wide apart. But it does keep things of the side walls.

Best.

Iain
London.UK.

[Antone Atmarama Bajor]

     As far as I understand it the BT7 and LAB subs should be used at least in pairs (if not fours).  To make one large horn mouth.

    The entire 90" X 22.5" (90" X 45" in 2x4cluster) mouth is effectivly the Point? Source.  I belive.  I'm not exactly clear on how the Bessel Arrays are acomplished, accomplished of the outer boxes but is there a delay or phase shift applyed to the outer boxes in a bessel array?

    Since 4 Pairs of BT7's / LABS are around 16' long I haven't played with any spacing.  I'm assuming that you don't want more than 1/3 wavelength spacing between any cabs High Cut/Low Pass range.

     I have been setting up straight lines and applying varying amounts of delay to the outer boxes since delay is all I have available to me at the moment.

    My hopes are to acheive reasonable Polar Response from the array of subs from ~28Hz-80Hz-.  At least better Pollar response than having 2 stacks of 4 Subs on either side of the stage.

    Its just something that I'm thinking of playing with.  Any how thanks for everything.

Antone-

[Ivan Beaver]

You don't need processing for a bessel array.  It is a conbination of series parallel and parallel wiring with fliping the polarity on 1 driver.  It takes 5 driver to make a single bessel alignment.  

My books are at the shop or I would try to draw it out for you.  When done properly you should be able to get the performance of a single device with 5 devices ( a bessel array), just louder.  Of course that is in a single plane.  Ifyou want it in a true polar you need 25 loudspeakers.  Basically you make a bessel array out of a bessel array.

To be honest, I have no experience with it, just the very basic concepts.  Check out Sound System Engineering (Don Davis) for more info.

[Iain_Macdonald]

Antone,

These two links plus Don Keeles' paper will give you the full answer on Bessel Arrays.

Even though your exercise is "desktop pa", we are looking at two different concepts and end results. The spaced line is just that !  A spaced low fequency line array but horizontal. The bessel array allows you to create a center cluster or as Ivan says below clusters of clusters to create a smooth hemisherical radiation from the boxes.

If you really want to get advanced, try modelling in both the horizontal and vertical. ie variations of stacks. Do also try the end fire, spaced one behind the other with appropriate delay. Link for paper below.

Happy reading.

Iain.


http://www.prosoundweb.com/install/synaudcon/tt26_3/tt26_3.p hp Low frequency arrays and steering.

http://www.prosoundweb.com/install/synaudcon/tt25_4/tt25_4_p 1.shtml Pat Brown on Bessel Arrays.

http://www.jblpro.com/pub/technote/PD%20LF%20TechNote.pdf JBL Technote on Forward Steered Arrays. Another type of end fired array.

[Mike Pyle]

Check out this post from Mark Seaton and the thread it is in. There were actually a couple of threads right about that time discussing delay vs. filter shading for sub arrays.

http://srforums.prosoundweb.com/index.php/m/11108/1614/0///4 49/#msg_11108

[Iain_Macdonald]

Mike,

A very interesting thread. Thanks for the link.

I remember from other posts that you have SLS 8695. Do you use your subs flat on the ground or do you vertically stack next to the 8695. I just wondered which is better for this product. Also what size audience can you cover.

Iain.

[Mike Pyle]

Iain Macdonald wrote on Sun, 07 May 2006 11:19

Mike, A very interesting thread. Thanks for the link. I remember from other posts that you have SLS 8695. Do you use your subs flat on the ground or do you vertically stack next to the 8695. I just wondered which is better for this product. Also what size audience can you cover. Iain.

I usually use the subs side by side close to the columns, but sometimes center stack for better results. I have never used enough sub cabinets at once to gain anything by stacking them vertically.

The event pictured below had about 1500 spectators, in 5 levels of terraced seating. Four columns and four LA400 subs were capable of high levels anywhere in the room, but set at a moderate level for the center seats I thought the nose-bleed corner sections sounded a bit thin. I'll use delays for those areas next time.

[Doug Fowler]

I did this very thing for the Ultra festival in 2003, with 16x d&b B2 subs.  I used the "point source" cabinet in Array Show and ended up with something that worked pretty well.

The promoter had complained about the power alley in previous years and I was able to spread it out pretty evenly to around 140 degrees or so.  I was surprised how much delay was required as I got farther from the center.

If I were to do this again, I would investigate some of the other methods described in this thread.  But for that particular application, the delay method worked like a champ.

BTW the power alley from 16 B2s lined up, with electronic music for source, was sickening  

[Iain_Macdonald]

Mike,

Thanks for the reply and the photos.

Very impressive coverage for such small boxes. have you seen these products ?

http://www.alconsaudio.com/site/q_series.html

Iain.

[Iain_Macdonald]

"BTW the power alley from 16 B2s lined up, with electronic music for source, was sickening"

So you can imagine what it must have been like for Eminem at Milton Keynes Bowl here in the UK. Where his tech specified 32 run in infra mode.

A two wide and four deep end fire, models very smooth below 80hz.

Iain.

[Peter Morris]

Generally I have found vertical stacking better, you get more power and I prefer the sound quality.

When the stack is vertical the vertical pattern is narrower focusing more energy into the audience.

The problem is you can’t use a vertical stack in the centre of the stage for obvious reasons.  The problem with a horizontal stack of this size is that the pattern could be too narrow. Sooo… unless you can curve the array you would probably need to delay things as you suggested.

This is not exactly what you are referring to but there are 125 Hz plots for an 8 meter stack, you can probably estimate what would happen with a 9.144 meter wide stack of LABs at say 60 Hz.

http://meyersound.com/support/papers/line_array_theory.htm

[Iain_Macdonald]

Peter,


Generally I have found vertical stacking better, you get more power and I prefer the sound quality.

I won't disagree that you might like the sound of boxes stacked vertically in some situations. As always, it depends.. Mostly to do with the acoustics and whether you are near another boundary, like a back or side wall.

When the stack is vertical, the vertical pattern is narrower focusing more energy into the audience.

Since we are talking about real subs, then I have to disagree with you. To get proper pattern control down to 30Hz then you would generally need an impractically high stack.

The problem is you can’t use a vertical stack in the centre of the stage for obvious reasons. The problem with a horizontal stack of this size is that the pattern could be too narrow.

If you are talking about 8 boxes. Then you can use an array of 5 in the front wired Bessel and three behind part phased/cardioid, or variations thereof. Don Keeles' analysis shows that a 5 box Bessel is the best. But you can try the 9 box Bessel, with your 8 lab inventory, because you only need 7 real boxes in a 9 box spacing.  

Best wishes,

Iain

[Peter Morris]

Hi Iain,

I never really consider the 30Hz stuff; most of the energy is in the 60 to 80Hz region so that’s where I consider the pattern control will have the most noticeable effect.

I also assume that when the subs are operating in half space their behaviour will be like a stack of twice the height. So producing a stack that is directional is not that difficult in the 60 to 80 Hz region.  An 8-foot stack would behave like a 16-foot line array in free space ( I think ?), so there should be some pattern control at these frequencies.

The problem with a Bessel array is the loss of efficiency caused by inverting the polarity of one of the boxes and running 2 at 1/4 or 1/2 power (what ever it is).  I think you would be about 8dB behind.

Regards Peter  

[Iain_Macdonald]

Hi Peter,

I never really consider the 30Hz stuff; most of the energy is in the 60 to 80Hz region so that’s where I consider the pattern control will have the most noticeable effect.

Being a realist I would tend to agree. But something weird happens at the extended lf level. Those of us who have used Tom Danley's ServoDrive product, notice that the mid-range level seems to appear cleaner. Also people tend to turn the whole system down. If you ever meet Joe O'Herlihy (FOH U2) he will say the same thing. It appears to be something to do with the ear trying to add in frequencies and doing other weird phase correction stuff. But very low frequency pattern control is useful in enclosed spaces. Tom Hidley started doing 20Hz & 30Hz rooms many years ago, and they  do sound subjectively better.

The problem with a Bessel array is the loss of efficiency caused by inverting the polarity of one of the boxes and running 2 at 1/4 or 1/2 power (what ever it is). I think you would be about 8dB behind.


Yes something like 7 or 8. "No such thing as free lunch". So that if you want absolute maximum output then this is not the answer. Hopefully people don't run their system at full limit all the time. (Hm mm) Bessel is essentially for smoothness when you can afford the power loss. Check out the Appendix of Don Keele's paper, and have a look at the charts comparing a 5 box block and a 5 box Bessel at +/- 45 deg off axis.

Of course if you are operating at less than max level then a 5 box Bessel is a great way of getting smooth coverage. If you also add the extra 3 behind as a pseudo cardioid things get really interesting. Though I still like the 2x4 end-fire that I showed previously. With the proviso of having enough front of stage area. In the bigger events, then we are really looking at a spaced or simple line. At a festival situation you might have environmental noise considerations. So keeping LF away from houses and offices should be a consideration. I would also think a horizontal line would be good for street fairs. Keeping it off the buildings and sending it down the middle of the street. Cardioids are great for stopping LF going backwards in to areas behind the stage. One place they really can make a difference is, with outdoor band shells. Hollywood Bowl type of venue where they have strict environmental noise limits. These concepts are not just for the monster sound companies. A two box or three box cardioid, at centre stage or wherever, is very useful for a smaller company doing corporates or similar. Just think of the success people have with Nexo sub product. Of course you don't need to be a Nexo or whatever owner to benefit.

Pragmatism tells us that, maybe in many situations, two stacks either side of the stage is the only viable solution. But these various types of array, are a great tool to have ready and waiting.

Iain.

[Peter Morris]

Talking of pattern control, having used a block of 6 and 9 LABs together (albeit my 18 inch vesion) there is about 10dB less behind these without doing any caridiod phase cancellation tricks nor Bessel array. Low distortion, great phase response, solid to about 30Hz etc etc...the problem is they are big and ugly.

..... when I started using these the mid range was noticeably cleaner, I always assumed it was caused by the lack of 2nd and 3rd harmonic distortion from the subs “muddying” up the low mids.

Peter

[Antone Atmarama Bajor]

     I haven't been on the thread for a couple days now.

Glad to see its still kicking.

    It sounds like using Odd box configurations is best for Horizontal sub arrays?

    Which isn't an ideal amount of boxes for a Horn sub.  I'm also thinking that LAB's and BT7's (in pairs to make on large horn mouth) will start Beaming at around 75Hz.

    So it maybe problematic by nature to use a Horn loaded box in a Horizontal Line array if used freq is above 1/3 mouth Wave length?

    Again I was thinking of trying to use all 8 of them like this.

|___|___||___|___||___|___||___|___|
..1...2....3...4....5...6....7...8..

    I have rane digital delays available for me to play with.

    I'm thinking the Lab's/BT7's will act as an omni radiator up till 1/3 wave of the mouth ~ 50Hz.  I don't know If I have a very accurate method of modeling the beasts with array show or MAPP.

    I've had good to reasonable results with Array show modeling them as a bunch of point source devices (delaying the outer pairs.

    But I get differnt results with Mapp.

I haven't tryed modeling 6 cabs yet perhaps that would be easier to achive good polar across a wider range?

    Could even stack the other pair of subs in the center facing the oposite dirrection (direction its too tall now) an run a cardiod array?  I guess now that the weather is good I should play with my BT7 configurations.

 I want to set up the mega 4X2 Horn mouth and blast 30Hz @ 148dB or so.

Thanks

Antone-

[Iain_Macdonald]

Antone,

Yes we are still here. It has been much more civilised down here than up in the Lab Classic with flame wars going on. Yikes.

It sounds like using Odd box configurations is best for Horizontal sub arrays? Which isn't an ideal amount of boxes for a Horn sub. I'm also thinking that LAB's and BT7's (in pairs to make on large horn mouth) will start Beaming at around 75Hz

Well yes and no. As you will have seen from Don Keeles' paper the maths for a Bessel function gives you odd numbers of units. BUT. The individual elements/units can be made up of a number of boxes. Ivan pointed out that you make arrays of arrays. Remember that using the Bessel principle is to try to achieve an array that radiates like a single unit. The spaced line concept is used to achieve dispersion like a horizontal line array. The audience at the front only get to be close to a couple of sub boxes. Unlike stacking the boxes either side of the stage. Where people standing to the side hear far too much bass and the people in the middle can often have either not enough or suffer power ally depending on where they stand. Two different concepts. It all depends on what you are trying to achieve.

Both the single block and the line achieve roughly the same spl in the far field. In the nearfield the line has less spl because not all the boxes combine constructively. Same deal as a vertical line array operating at higher frequencies. Same principles apply, just the wavelength is different.

It will be interesting for you to try some real experiments. Not that many people have tried.

Iain.