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alex918 8th January 2013 03:36 PM

need help for 100v pa system
hi i am a beach bar/coffee/food owner in greece and looking for some help on how to set up & best way to go about a 100v pa system. i have been doing research but cant figure out what will work. the watts seem really low that the systems come with(not expecting 150w continues speakers)!!
my problem is that i have been working for about 10 years with a power amp and its starting to get to me because its really loud in 4 spots (wear speakers are) so that i can cover the whole area.
let me give you a general idea of the area, i am dealing with about 700 square meters, 15m width and 50m long. in that area is a pool that seats 50 people and a sitting are of 30. on the beach i can seat up to 250 people but i will still use a the power amp down there.
my idea is that i would want 12 speakers that aren't back round music but a little more then that. basically you can speak without having to speak really loud but to have a good amount of sound and if need to go even bit louder. im thinking like 8 speakers around the pool area (a speaker every 10m) and 4 at the sitting area (150 square meters).
I am open to all suggestions and ideas and would greatly appreciate some help.
thanks alot

Enzo 8th January 2013 06:21 PM

Over here I think 70.7v systems are more common than 100v systems, but I could be out of date. In any case, the whole point of "constant voltage" speker systems is that you can connect many speakers to an amp channel without having to do strange things to keep impedance in line.

A place like a restaurant usually does not want to fill the place with sound from just a pair of speakers. That results in it being too loud near the speakers, and the coverage is uneven. SO we wire up a number of speakers each at lower volume than the old way. Each smaller speaker covers less area than the old pair of speakers did.

The amplifier puts out the constant voltage signal, and generally at each speaker there will be a matching transformer. Those generally have adjustments for power. And that allows you to program the relative loudness. For example you might have 10 speakers in a restaurant, but one of them is over the waitress station, where they call out their orders to the bartender. SO we might set the other 9 speakers at 1 watt, but the one over the waitress station at 1/2 watt or 1/4 watt. Now no matter what you do with the volumne control, that one speaker will always be less loud than the others. You can have even coverage if you want, or you can have different parts of the room set up at different loudness.

You can buy the matching transformers separately and use regular stereo-type speakers at each spot. Or you can use common restaurant ceiling speakers that come with a transformer right on themselves. Or both. The small inexpensive transformers you can get all over are usually limited to 10 watts. But there are heavier transformers available for higher power applications.

About watts. A band might come in with a 1000 watt PA system, and they will be pretty loud, not conversation level. But the typical 8" or even 10" ceiling speaker is really pretty loud at one watt, 4 or 5 watts would probably be all you'd need. Remember, it is right over your head, that band PA is in the corner trying to fill the hall.

sreten 8th January 2013 06:46 PM


The wattage of each 100V PA speaker will be low. Each one will have
a set of taps at various powers, varying the level of each one relative
to tho others depending on the relative tap settings.

The highest power tap determines the size of each speakers transformer
and thus cost, consider 100V speakers with different maximum powers.

If you have a 100W 100V amplifier, the total of all the speakers tap
settings needs to be below 100W, but as high as possible under
100W with your relative levels set.

You can then control overall level at the amplifier.

rgds, sreten.

wg_ski 8th January 2013 07:13 PM


Originally Posted by sreten (
You can do a cruder version using a normal amplifier and normal
speakers (and thicker cable).....

Or use a normal amplifier that puts out either 70 or 100 volts to begin with. 70 volts is 600 watts at 8 ohms, which can be a 300W/4 ohm 2 channel amp bridged. That size is common and cheap. For a 100V system it's 1250W at 8 ohms. Then connect your speakers with 70 or 100V transformers, up to the rating of the amplifier. There are plenty of commercially available speaker cabinets at pretty much all power levels with built in transformers and selectable taps. You're not just limited to ceiling speakers.

You can use an amp that doesn't put out the full 70 or 100 volts at full load, but you won't get full power. That won't hurt anything - it just won't be using full capability. To get full power you can load it more "heavily", but then you're back to calculating impedances again to get a correctly matched load.

alex918 9th January 2013 09:07 PM

thanks for the information, glad that there are forums that i can get good info out of. it is help full.
i went around to some shops here on the island of crete and the prices that they are giving me are outrages. so, i spoke to a friend and he said he has an amp that he will give me if i can make it work for what i want, a koda 266a (Koda KD-266A DJ PA Amplifier Bridgeable - 4000W Max at best price!).
i see on this amp bridged is 4000w, could i setup 12 speakers of 250w to it and if so what other machines would i need to do this?
i was told something about this machine Behringer: ULTRAZONE ZMX8210 that might be able to do what i want but the explanation was very bad because the guy i was talking to realized i was unhappy with the price he gave and that i wasnt going to get anything from him!!

AuroraB 9th January 2013 09:46 PM

What are you trying to do? Reasonably quiet background music in a bar/ restaurant, or are you trying to run a full frequency disco outfit with 100V speakers??

Read the first 3-4 answers over and over again until you understand what is said. Your last post clearly indicates you didn't understand what they said. Omit the last answer about running 600W to get 70V......

A 100-200W amp properly set for 70 or 100V sitribution will cover a restaurant of at least 150 sq.meters with ease, for background music.

EDIT : Reread your post..... 700 sqm... OK what loudness level do you really expect? Background?
With an area that large, forget about your 150-200W speakers..... and the 4000W amp.....
You need LOTS of smaller speakers, and probably several 100-200W amplifers will do better than one monster amp, feed all amps with a common balanced feed signal from wharever your source is located-
- and above all, it will probably be a lot cheaper......

wg_ski 9th January 2013 10:45 PM

Compare the prices of a "600W amp" vs. a much smaller but "proper" 70V BGM amplifier and it's not such a stupid idea after all. They just want too much for that stuff, because they think they have you over a barrel. If you're an installer or architect I guess they do. But if you know what you're doing they don't. Brand new an XLS1000 is only $300. 60 miserable watts of commercial sound amp will set you back that much and that would be marginal at best. When old QSC's and such can be had for next to nothing and are cheap to maintain they are very viable alternatives. I have an old QSC Model 41 that's perfect as a 70V line driver that just cost me a set of output transistors, 2 capacitors, and some time to blow the dust out of it.

AuroraB 9th January 2013 10:57 PM

You are partly right, I'll agree to that. I'm not so sure, though, that a regular low-impedance amp will be so happy with driving all those smaller trafos that are obviously needed to drive this large area.. that will be one really heavy inductive load....
that said, most 70/100V amps these days 'are' often fairly regular SS amps driving a stepup trafo.....
- which BTW are also sold separately and can be used with good second hand amps.

Speedskater 10th January 2013 12:16 AM

See Rane Note:

Constant-Voltage Audio Distribution Systems:
25, 70.7 & 100 Volts

wg_ski 10th January 2013 12:18 AM

Transformers are no more 'inductive' than loudspeakers. The magnetizing currents are small, and the increasing impedance at HF is no worse than a voice coil. You do have to be careful at too low a frequency because they can saturate and the impedance will drop - there will be telltale distortion. Engage the high pass filter if there is one on the amp, and/or run the 30 Hz slider all the way down on the EQ.

As far as impedance matching goes, 600 watts worth of 70 volt loads is right around 8 ohms. 10 loudspeakers on 60W taps (or equivalent) will provide that load. If you only feed it from a 200W 8 ohm amp, you'll just get 20W a speaker. Which might be exactly what you need.

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