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Author Topic: point source vs. distributed (delayed)  (Read 1851 times)

mark ahlenius

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point source vs. distributed (delayed)
« on: September 07, 2004, 11:03:55 pm »

Hi,

I have a question regarding current designs for reinforcement systems for a sanctuary or auditorium.

Is there a move away from what I used to call point source sound systems, where the speaker was placed center stage above where the speaker stands or singers are?  

Someone mentioned that all the system designers were pushing a more distributed system (several speakers in different positions using delay lines, etc).?  That they could not get designers to use point source anymore.

I always liked point source, when the room was the right shape, because the sound came from the direction of the speaker or singer.

The only reason I could think that there may be a movement in this direction is to control the SPL levels more evenly.  I keep hearing that the SPL police may be coming soon ;-}

I also know that it greatly depends on the size and shape of the room, but for a small auditorium seating less than 600 folks, I am wondering what the best approaches are.

So my basic question is whether or not there is a movement away from point source designs towards something else (i.e. delayed-distributed types).

thanks much!

'mark
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gainreduction

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Re: point source vs. distributed (delayed)
« Reply #1 on: September 07, 2004, 11:54:25 pm »

Hey Mark,

In the last month I've put in both an overhead distributed system and a point source system with a delay and subs into two very different types of churches.

The overhead system was that way for several reasons;  

1) The ceiling was low 13' and the room was long 60', so even coverage from one speaker (or speaker cluster) was impossible.  For the folks in the back to hear, that one box would have to be cranked pretty loud, causing bad gain before feedback etc.
2) They have a more traditional worship style.  A vocal or two with piano/keys or flute type music, never drums or electric guitars.  The spoken word was most important.  There's no need for 18" woofers or big boxes because the program material didn't call for it.  A well tuned system with 25 or so high quality 8" ceiling speakers did the job great.

As you mentioned, SPL was important and w/ overhead spkrs so close to the listeners, the system has to be barely turned up for every seat to hear clearly.  Nobody complains how loud it is, but everyone hears clearly.  I put a few ceiling subs in just to add excitement when they watch movies and what not.  

It can be a bit strange to hear the voice of the pastor on stage coming from right above you, but the brain makes the adjustment quickly and after a second, most don't even realize where his voice is coming from, it just IS.

The second church was an upgrade from their previous system and they are gearing up for a more contemporary style worship (full band with drums, guitars, keys, choir)  A big 'A' frame church made it perfect for hanging a big box Renkus cabinet that EASE showed us would cover the first 15-20 pews or so, but we had almost 30 to cover, so we hung a smaller delay speaker for the back rows.  A few subs to round out the bottom end, a day or two of Smaart and TEF and they are rocking!  

It's all about the right design for the right room for the right purposes.  I feel bad now for selling JBL SRX cabinets & SRM450's with the generic 'these are GREAT speakers for almost ANY situation' for years at the Guitar Center when I now realize the true worth of real system design.

anyways, enough of me.  Cheers!

Steve.
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Tom Young

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Re: point source vs. distributed (delayed)
« Reply #2 on: September 08, 2004, 08:39:18 am »

I have not seen a trend to go one way versus others.

More often for me it is a case of programming, budget and/or architecture.  If the ceiling or peak is high enough, then a center cluster makes sense much of the time.  If programming dictates a benefit from stereo capability, then I will consider a split L&R loudspeaker system design. If there is a center architectural location where a steered column loudspeaker can live, then this becomes a very viable candidate.

Center clusters (of "spherical", aka: traditional 2/3-way loudspeakers) do have one known anomaly: there will be a down lobe that will wreak havoc with a center podium mic or an RF mic that moves through the center of the platform below the cluster.  The lobe is a result of the LF elements interacting with one another and are somewhat dependent on crossover design. The lobe can be reduced if your measurement chops are very good and you have a measurement system such as Smaart, TEF or SIM.  If you can "explode" the cluster and move the devices apart, you can also change/reduce the lobe in this manner.

The other architectural element of loudspeaker system design choice is visibility.  If the client cannot accept seeing a  big "clunky looking" center cluster, then I explore other ways to accomplish the needed goals.

I use distributed systems when the ceiling height is too low for loudspeaker positions that evenly cover the congregation from one position.  

These days I also consider column loudspeaker systems in either mono (as mentioned above) or stereo configurations.  These can be positioned low and are inherently less visually obtrusive.
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Tom Young, Church Sound section moderator
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com
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