Increased spl from barn doors?

[The Boogie Man]

:D Hi all,

Now I know I've come up with some mad ideas and strange questions, but some feedback on this would help with the ongoing education. :P

 

Pubs and bars etc usually have strange shapes, some times wide, sometimes long. so getting even coverage can be "interesting" to say the least. The ideal would be good cabs (120db+ spl) above the crowd pointing to mid pack, but as all know throw in low ceilings and same said cabs will kill front rows to reach the back.

plus the dispersion pattern of some speakers can be sending your precious spl away from the target.

 

So I wondered, if you set a driver further back in a cab then you narrow the dispersion and increase the "perceived" spl by throwing the sound wave further ( or am I wrong? ).

But that means someone off axis receives less sound. The vertical dispersion "closing" could help with low ceilings, but if the cab is set at too high a height then targets close or nearly under the cab would miss the sound as well.

 

Its only an idea ( as no-one produces one I'm assuming, at the least, I'ts impractical or costly) but if you fitted barn doors ( no not that type :D ) to the front of a cab could the dispersion be "shaped" for differing applications. Or has the horse just bolted

[The Magus]

Effectively you would be adding a horn to the speaker, so you would modify its directivity. For a horn to work effectively across the frequency spectrum it must be properly coupled to the driver. Don't expect to fit 'barn doors' on to a full-range cab and attain uniform results across the frequency spectrum!

 

However, look at what Funktion One have created! http://www.funktion-one.com/products.htm and select '

'Double Infrahorn' which they describe as a horn extension! I've not heard it in action, but it certainly looks impressive!

[Rob_Beech]

never even saw the horse.

What you've described there is a basic version of a horn loaded speaker, a design that is common in many high end applications and has been for many years.

 

the idea behind horn loading speakers for mid and high purposes is to control the dispersion and concentrate the spl into this dispersion. this of course only works down to a set frequency. It can often allow cabinets to be arrayed better.

 

 

Your plan has a basic idea which follows a general design of how speaker are hornloaded. However there is ALOT more to it than that.

First of al you have the mathematical sides of things, you can't just put a "horn" onto something to make it work for you. Secondly there is the position.

the entire drive needs to enter the horn an the horn directs the sound.

 

I think we can conclude that unfortunatly where I see what you are trying to acheive there is much more to it, it will not work in this sense.

 

Despite that, I dont think you are going about solving the problem in the right way. Horn loading a speaker or using a horn loaded speaker is going to concentrate higher SPL direcly infront of it, if there are people there infront they are going to be there no matter what type of speaker you use. Nothing will get hrough them properly. A better idea would be to have these main speakers, and then have various fills and delays (time aligned of course) which would provide sound for the rest of the room.

 

Rob

[The Boogie Man]

Hi troops,

 

It was never a "plan" just an idea that I wanted to voice to see if the priniple had merit. right or wrong I learn a bit more, and that is the plan :P

 

cheers guys.

 

 

So sound carn't be "channeled" or focused in the same way as light.

[Bobbsy]

As others have said, at the most basic level your "principle" is already used by loudspeaker manufacturers...but the mathmatics and physics involved are far more complex than a basic barn door. Yes, to some extent sound can be channelled or focused...but the degree to which is is effective varies greatly with frequency.

 

You may find some interesting reading if you look at the details of how line array systems work...in effect, these are purpose built speakers to do what you're talking about. As I recall, both the L-Acoustics and d&b Audiotechnik sites have some technical background about their systems that may be interesting reading for you.

 

Bob

[The Boogie Man]

Cheers Bob, I'll have a gander at thoe sites.

[johnhuson]

This Page is the one you want to be looking at on the L-Acoustics site, I'll warn you now though they're very in-depth!

[benweblight]

the idea behind horn loading speakers for mid and high purposes is to control the dispersion and concentrate the spl into this dispersion. this of course only works down to a set frequency. It can often allow cabinets to be arrayed better.

various fills and delays (time aligned of course) which would provide sound for the rest of the room.

 

Rob

 

rob, delays?, in a pub? ** laughs out loud **

[Bobbsy]

rob, delays?, in a pub? ** laughs out loud **

 

Sure...could be. It's becoming more and more do-able these days with the advent of affordable digital board that give you all the delays you want. The 01V96 Yahoo list is full of pub acts using that board now. Just arrange your speakers differently to make use of them.

 

Bob

[Rob_Beech]

with budget desks digital or analogue with matrix capabilities its quite easy to assign different delays.

 

As Bob says there are many acts using this type of setup. I was thinking more for installation actualy but alto of small touring outfits implement this aswell.

 

Installation wise this can be done on a very tight budget. a Spare Aux off the desk could feed a budget 9and yet very good) processor like the DX2496. This would give you 6 outputs with delays. 2 spare aux and you can have 2 signals go0ing to 6 outputs etc. A slightly larger desk with matrix outs and you can pretty much do whatever you want.

 

When I'm installing a system into a building the first thing I look at is even coverage. I want to know what SPL they require in different areas and then I can look at how I'm to do this. Its one thing having its 95db a the back of the room but if its 118db at the front then its no good. A problem a higher roof solves almost instantly.

 

Rob

[paulears]

There is little real point in delays in a pub size venue. Useful in larger venues to get the spl up after the drop off on a fair distance, and this distanc means time alignment is important to restore the integrity of the sound. In a smaller venue, then loudness isn't usually a problem, and the distances are much shorter. In fact the left to right separation might be mor than front to delay distance making any delay calcs very confusing as front to back will almost certainly wreck left to right and any centrally panned signal will become a bit tricky to align with perhaps 4 (or more) sources. I'm not really sure it is worth it?

[Bobbsy]

As a person who rarely does pub acts, I might have thought that, Paul. However, as luck would have it, one of my very few forays into the world of pub sound absolutely NEEDED delays.

 

The pub in question was basically an "L" shaped room with the performers in the corner linking the two legs. The long axis was long and skinny (around 80 feet by memory), with an archway halfway along. They wanted sound in the whole pub.

 

To try and reach the back of the long axis with a single throw would have meant blasting those in the front section. My solution was time-delayed speakers the far side of the arch. Seemed to work a treat...at least the landlord was very complimentary about the sound "compared to what it usually sounds like". He actually offered more work, but pub acts are not my scene...I was only doing this as a favour for a neighbour who was in the band.

 

Bob

[Rob_Beech]

A venue very similar to what you mention springs to mind. may even be the same one, This is in Chelmsford, can't remember the name.

 

its a pub/club/restaurant where my band has played a couple of times. very difficult to get the sound to carry through the arch as the roof is only low. You have the option of having the speakers so low that the sound is directed through the arch, then its too low and people who stnad infront block the sound. Have the speakers just above head height and have it bouncing back at you. Or put delays in. I went for the 3rd option and it worked.

[Bobbsy]

Nope! This one was over here in Bedfordshire....so it looks like we've found at least two pub venues that work well with simple delayed speakers!

 

Bob

[The Boogie Man]

I did consider delays for pubs, but with some of the crowds I've had they might never come back from the audience .

The reason I was thinking about dispersion was to do with the strange shapes of pubs and multi use venues. If the sound could be stopped from travelling up or out side ways too far then feedback from low ceilings etc could be reduced and the sound level could be raised. It wasn't so much projecting the sound to the back as such, more focusing the sound.

cheers

baz