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-   -   Speaker Array (http://www.diyaudio.com/forums/multi-way/44407-speaker-array.html)

jawbreak 30th October 2004 07:39 AM

Speaker Array
 
Hey all, newbie question, getting into speaker building and just been reading as much as I can. Awesome forum.

My question is what is the purpose of spearker arrays? As in what are they designed to be used for mainly?

RJ 30th October 2004 02:23 PM

The beauty of an array is that the 5" drivers are doing all the work below about 2.5 kHz, and the bass from multiple small woofers is fast as lightning, musical and punchy.

I just got finished building an array with 10 - 5 1/4" woofers & 6 Planar Tweeters.

When I play "Down In It" by NiN the bass literally slams you in the chest. The bass is also very clear & defined. I can hear the fingers of the bass player in Diana Kralls "East Of The Sun" stroke the strings..

The imaging is fantastic. The ghostimage between the speakers is very well defined and pretty much stays put. There is no sweet spot but a sweet area. To read more into line arrays you have to read Jim Griffin's white paper on this subject. A must read.

http://www.audiodiycentral.com/awpapers.shtml

There's two ways to go about this. Use very good drivers for optimal sound. or use inexpensive drivers & close-outs. I used inexpensive drivers and I'm not sorry I did. I don't know if I want more clarity coming out of my speakers. The ones I have already reveal flaws & poorly engineered mixes on my CD's....
BUT - on well produced CD's, they sound great!!!

johninCR 30th October 2004 04:06 PM

Arrays are commonly used for large venues because of they project sound more evenly over larger distances, so much less equipment and power is needed to cover an area with sound. This is because of the way sound is dispersed from an array.

With a typical speaker (point source speaker), the sound disperses in a sphere. With an array, the sound disperses in a cylinder with relatively little sound dispersing above or below the ends of the arrays. This concentration of sound within the plane of the array makes it project over a greater distance. A point source speaker gets quieter by 6 decibels for every doubling of distance, but a line array by only 3 db. This is in the nearfield whose max distance is dependent upon frequency and the length of the array. Past this transition point an array disperses the same as a point source.

This difference is huge. For example, let's assume your listening position is 4 meters from your speakers (approx 13ft). Let's say you want to listen to something quite loud, say 100db. Your point source speaker is must play at 112db at 1 meter, vs the array at only 106db. Assuming the same overall sensitivity, the point source needs 4 times the power. Also, the point source will get louder much faster as you get closer to the speaker, so the array will sound more balanced at different locations in the room.

Because you have multiple drivers each one does very little work, so distortion is lower. Using the example above let's also assume that the array consists of 16 of the same drivers used in the point source speaker and they have a decent sensitivity of 88db at 1 watt at 1 meter. That point source speaker is going to need 256 watts to get 100db at your chair, but the line array is only going to need a total of 4 watts (1/4 watt per driver) to get you there.

This is what makes great results possible with cheap drivers. They just need to sound good, not sound good with a lot of power applied. Cheap drivers are widely used in radios, tvs, cars, etc. and many electronics parts houses carry a variety of cheap wide range replacement drivers, so you can listen to them and choose those that sound best to you. My favorites of those available here in Costa Rica are only $1.50 ea, which makes a nice line array pair possible for a total cost of less than $100.

As RJ stated, Mr. Griffin's paper is a must read for more detailed info on line arrays.

jawbreak 30th October 2004 10:53 PM

wow, thanks for the in-depth reply, I think I uderstand now. What Im looking for is to make something for music only and the array sounds like pretty good for that but I being a college student live in a small room. What would be my best bet for these listening conditions.

johninCR 30th October 2004 11:11 PM

I use a pair of 5 driver open baffle arrays for my desktop and I get the soundstage image of being on the front row of a concert. For a small room 8 4" drivers will probably do the trick. You want the drivers as closely spaced as possible and for your use the main thing to keep in mind is that you want to be within the plane of the array wherever you are listening because above the topmost driver the sound is significantly diminished.

You are likely to need either a high efficiency tweeter or an array of tweeters to fill in the top end and a sub to fill in the low end.

What's your budget and wood working capacity?

jawbreak 30th October 2004 11:36 PM

Well I was hoping not to spend more than $200 dollars and as far as wood working capacity, I live near my dad who has lots of equipment so that not a problem. Main problem is I've never built any speakers yet :) Is there any easy to follow systematics for these and is a small speaker array a good way to go or is like two 2-way or 3-way speakers better? Probably a matter of preference, but I'll ask anyways.

chipco3434 30th October 2004 11:58 PM

Quote:

Because you have multiple drivers each one does very little work, so distortion is lower. Using the example above let's also assume that the array consists of 16 of the same drivers used in the point source speaker and they have a decent sensitivity of 88db at 1 watt at 1 meter. That point source speaker is going to need 256 watts to get 100db at your chair, but the line array is only going to need a total of 4 watts (1/4 watt per driver) to get you there.
I have built a couple open baffle line arrays using the PE close out 4" drivers. Like JohninCR says, they are VERY efficient. Using a BrianGT NIGC, they will drive you out of the room. They'll make the CD skip. Total price for the whole shootin' match was less than $300, and that's with a $100 sheet of wood.

I'll never go back to boxed point source speakers.

johninCR 31st October 2004 12:09 AM

A lot depends on your musical taste and how into speaker building you want to get. I'm lazy, cheap and believe in simplicity, plus crossover parts are difficult to find down here. I prefer the open natural sound of dipole and I love the big soundstage of arrays. I look for the cheapest best sounding small wide range drivers that I can find and go from there keeping electronics to a minimum.

You can experiment very cheaply. Go out and find 4 or 5 cheap drivers that you like best. Get a piece of that posterboard with the styrofoam center that architects use for models. Cut driver holes with a knife and tape the drivers in with duct tape. Connect the wires and give it a listen. You'd be amazed at the result of less than $20 and 15 minutes of construction time.

jawbreak 31st October 2004 12:28 AM

Quote:

Originally posted by johninCR
A lot depends on your musical taste and how into speaker building you want to get. I'm lazy, cheap and believe in simplicity, plus crossover parts are difficult to find down here. I prefer the open natural sound of dipole and I love the big soundstage of arrays. I look for the cheapest best sounding small wide range drivers that I can find and go from there keeping electronics to a minimum.

You can experiment very cheaply. Go out and find 4 or 5 cheap drivers that you like best. Get a piece of that posterboard with the styrofoam center that architects use for models. Cut driver holes with a knife and tape the drivers in with duct tape. Connect the wires and give it a listen. You'd be amazed at the result of less than $20 and 15 minutes of construction time.

Wow, cool idea I'll definitely true some messing around thanks.

RJ 31st October 2004 12:28 PM

You could go to Menard's, Lowes or Home Depot and look for pre-formed enclosures like this fellow did;
http://ceramicsubs.web1000.com/4x4x42/index.htm
Good Luck!!!


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