Powering LOTS of small speakers

[stereosanctity]

Hey guys,

I've been lurking here for a long time and have found a real lot of good information.  I'm currently planning a sound installation for my BFA thesis.  I need to figure out a way to power about 100 8 ohm, 3 inch, 1 watt speakers.  I'd like to keep it as simple as possible.  I was hoping to be able to have a simple power amp with 2 cables coming out with the cables spliced to power 50 speakers each.  Can you guys recommend a good simple way to do this?  Also will I need to output 100 watts of power to power 100 1 watt speakers?  Thanks for your help, I really appreciate it.

-Scott

[jacobyjd]

I don't really know the implications of using that many speakers, but my first impression would be to simply run them all in parallel, then make sure you have plenty of power...as far as power needs go, too much is better than not enough. You can always turn it down

[JKowalski]

You can group the 100 speakers into groups of ten in series, then put those groups in parallel. That way you have each group with   8 ohms x 10 speakers = 80 ohms, and the ten 80 ohm groups in parallel comes out to be 8 ohms, which is your standard speaker load. Then you just find a 100 watt amplifier set up for a standard 8 ohm load, and hook it up. This way you have it a little more organized as well, as you have only ten cables coming out of your amp and the series groups of speakers can be placed into certain sections of your installation.



This project sounds really strange 

[anchovie]

I would have 10 parallel strings of 10 series speakers - then you end up with an 8ohm impedance just as if you were using a single speaker. As for power, the 1 watt rating of an individual speaker is not a minimum requirement, it's how much it can handle. So I'd go for an amp lower than 100watts, maybe something like a Gainclone.

[R.G.]

I don't know what you're heading for, but have you read about the "Sweet Sixteen" speaker system from 1961?
See

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=3257

On your actual questions:
A single power amp ...can... do this, but it's a huge amount of wiring to do. A simple way to wire them? You're just going to have to string the wires.

You want to wind up with something like eight ohms presented to the amplifier when you get through. You have nominally eight ohm speakers to work with. Two eight ohm speakers in parallel is four ohms, two of them in series is sixteen. Two sixteens in parallel is back to eight ohms, so a group of four eight ohm speakers connected series/parallel is back to eight ohms.

That means you can get eight ohms by connecting four speakers in series/parallel, or sixteen speakers in four series/parallel groups. Likewise you can get eight ohms with sixty-four speakers (4x4x4) If you did two sixty-four-speaker arrays (2x4x4x4) in parallel you'd have four ohms presented to the amplifier and 128 speakers.

The reason for hooking them up this way is that the speakers are all putting out the same power each, not one louder than the other. This way you can put in 100W of power and get each speaker dissipating 100/128 watts. If you don't use symmetrical hookups, some speakers will be fed more power than the others.

Another way is to make small power amps and have each power amp feed one speaker or one group. The LM386 IC will do a watt or two, and could drive one speaker. Make 100 of these and you get each speaker driven from it's own amp. Or use something like the LM1875 power chip for 16-20W each, and drive sixteen speakers each from each amp.

Mother Nature insists that if you get 100W out, you have to put more than 100W in. But speakers work fine with less than their maximum power input. They just get quieter. So you could power the entire array from a 1W power amp - it just wouldn't get as loud.

[gmoon]

Seven 8 ohm speakers in parallel ==  1.1429 ohms, then connect seven blocks in series == 8 ohms.

That's 49 speakers. Pretty close to the goal of 50 per channel. Sneak the 50th in there-- it won't change the load too much  .

[stereosanctity]

Thanks guys.  All of your ideas are great!  The groupings of ten wired in parallel is terrific and definitely will work with what I'm doing.  For me building a 100 watt power amp is out of the question, I just don't want to be tinkering around with that type of power.  I'm sure I'll be able to rustle up some old 100 watt combo amp by the time next fall comes around.  Thanks alot for you help guys!  And anymore ideas would be great!

[pazuzu]

http://www.electronics123.com/s.nl/it.A/id.1312/.f?

why?

as in, what principle are you trying to demonstrate? you said it was for school.

[Top Top]

http://www.electronics123.com/s.nl/it.A/id.1312/.f?

why?

as in, what principle are you trying to demonstrate? you said it was for school.

My guess is it is an art installation... might not be any particular principle. He's getting a bachelors in fine arts (according to his op).


I am interested to know what 100 tiny speakers would sound like, BTW, and how far apart you will have them....

[pazuzu]

me too man, that's why i googled the speaks, so i could buy them, but it's a little too pricey.

[sean k]

Actually I don't think you'll need 100 watts of power anyways but I'm just speculating. If you need 100W to drive one speaker you'll basically need the same power to drive 100 speakers... but do you even need 100W which is only four times louder than 1W.

I just built my first LM386 and put two 8ohm speakers in parallel... and that was plenty loud... for my needs anyways. So given the decibel to power ratio, which is double the loudness and you need 10 x the power, I reckon two little 12V driven ten watters.... which essentially means you might get away with using your average car stereo! 

Lots of TDA (1519B, 2030 etc) IC's designed for car stereo's out there and they're pretty cheap and easy to get working.

[birt]

it will sound different as you add more speakers. the impedance load might be the same but i'm pretty sure the inductance will not.

just to look at (way to expensive for me): http://www.philjonespuresound.com/PJWeb11_PCab8T24B.aspx

[Cliff Schecht]

I would have 10 parallel strings of 10 series speakers - then you end up with an 8ohm impedance just as if you were using a single speaker. As for power, the 1 watt rating of an individual speaker is not a minimum requirement, it's how much it can handle. So I'd go for an amp lower than 100watts, maybe something like a Gainclone.

I like this answer because it would look super cool!

[frank_p]

Keeping it together:
http://www.diystompboxes.com/smfforum/index.php?topic=73180.0

[Fender3D]

Actually I don't think you'll need 100 watts of power anyways but I'm just speculating. If you need 100W to drive one speaker you'll basically need the same power to drive 100 speakers... but do you even need 100W which is only four times louder than 1W.

I just built my first LM386 and put two 8ohm speakers in parallel... and that was plenty loud... for my needs anyways. So given the decibel to power ratio, which is double the loudness and you need 10 x the power, I reckon two little 12V driven ten watters.... which essentially means you might get away with using your average car stereo! 

Lots of TDA (1519B, 2030 etc) IC's designed for car stereo's out there and they're pretty cheap and easy to get working.

If you need to spread your sound in 100 different places, you'd better have 100 separate speakers, 'cause going several meters with low signal is bad...

When I did church PA systems, I did use 100V line to drive the clusters, each cluster had another transformer to drive the 8/16 ohms load.
This way you will not have any issue with long cable running.
(You will have several meters of cable involved to connect 100 speakers btw)

[stereosanctity]

Yo dudes,

Yeah! Still awesome input!  You're correct, its installation art.  For those that aren't familiar installation art focuses on the interaction between many different elements i.e. sound, video, sculpture, whatever.  I need the hundred speakers to basically be a large band going around the room.  Along with a full stack.  The speakers are just one element of the whole thing.  I've got loooooots of work to do between now and next fall!

[ashcat_lt]

it will sound different as you add more speakers. the impedance load might be the same but i'm pretty sure the inductance will not.

just to look at (way to expensive for me): http://www.philjonespuresound.com/PJWeb11_PCab8T24B.aspx

Considering that inductance adds the same way resistance does, and assuming all the speakers are nominally the same, the overall inductance will be the same as that of any individual speaker.

[pazuzu]

it will sound different as you add more speakers. the impedance load might be the same but i'm pretty sure the inductance will not.

just to look at (way to expensive for me): http://www.philjonespuresound.com/PJWeb11_PCab8T24B.aspx

[stereosanctity]

I want.

[pazuzu]

i'd like to hear it next to a traditional cabinet of the same wattage. honestly, i can't imagine that much of a difference.