Help to select amplifier type

Hi, am new to forum, hope I'll be accepted by your team...Please anybody could help...Let me explain what help I need from your team...
With 9 speakers (8 ohms - 50 watts each) in series/parallel (8Ω X 3 = 24 / 3 = 8Ω) with Resultant Impedance 8 ohms per channel, the max demand output per speaker is 15 watts with 20 watts PEAK from time to time, depends on speech rates. Would like to know the following:-
What will be the type of amplifier output : RMS or other?
What power output per channel ?
What size of wire from amplifier to one group of speakers when the length required is 24 meters ?
What will be the major problem in this ser/para wiring system ?
SPEAKER:- 8ohms 50watts but volume needed is 15-20 watts
NO Woofer or Sub woofer - Just midrange/ medium
Bass control will set at ---
Treble control will set at haft
Speakers mounting height 2.5 meters from floor.
TEST TONE:-
2.5v (please note that NEVER the volume be set at that high intensity) Then I make another test tone with a higher volume that we will set the system and the voltage tested was 1.2v.
ROOM:- 15 X 15 meters X 3 meters Height
MUSICAL TASTES:- Classic at reasonable sound level (9 minutes playing during 7 hours speech)
AMPLIFIER CHOICE: is it possible to use a HI-Fi amplifier for this system ?

If need add. data, kindly let me know.

Please and thanks for help.
 
Last edited:

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Have you seen this ?
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html

Its well worth a try and a test to see exactly what power requirements you might need.

The main problem with series/parallel combinations of speakers is that you alter dramatically their behaviour because each is not driven from a low impedance voltage source anymore. They all interact and modify each others response. For PA applications and voice it may not be much of an issue as overall clarity is what counts.
 
Thanks for assistance
SPEAKER:- 8ohms 50watts but volume needed is 15-20 watts
NO Woofer or Sub woofer - Just midrange/ medium
Bass control will set at ---
Treble control will set at haft
Speakers mounting height 2.5 meters from floor.
TEST TONE:-
2.5v (please note that NEVER the volume be set at that high intensity) Then I make another test tone with a higher volume that we will set the system and the voltage tested was 1.2v.
ROOM:- 15 X 15 meters X 3 meters Height
MUSICAL TASTES:- Classic at reasonable sound level (9 minutes playing during 7 hours speech)
AMPLIFIER CHOICE: is it possible to use a HI-Fi amplifier for this system ?
I already inserted this part in first topic
 

KatieandDad

Member
2011-11-17 3:49 pm
UK
Have you considered the classical way of driving a lot of loudspeakers ?

It is usual to use the 100V line system. A 100V line output transformer is placed at the output of the amplifier and then all the speakers are fiited with a 100V line transformer and then the transformers wired in series.

As already mentioned, for voice a parallel / series combination will work but will not be good for Hi-Fi music.

As far as the amplifier is concerned, any amp will do as it only sees the combined impedance that it is driving.
 
Have you considered the classical way of driving a lot of loudspeakers ?

It is usual to use the 100V line system. A 100V line output transformer is placed at the output of the amplifier and then all the speakers are fiited with a 100V line transformer and then the transformers wired in series.

As already mentioned, for voice a parallel / series combination will work but will not be good for Hi-Fi music.

As far as the amplifier is concerned, any amp will do as it only sees the combined impedance that it is driving.
xxxxxxxxxxxxx
I greatly appreciate your advise too, So I want to help this association, these speakers has already been purchased before I get involved, I just need help to set the system, we have some time to establish the schematic and advise.

Please note that Speech/Talk is only soft speaking, NO pop music, Just Religious music playing at 15 watts / 20 watts PEAK

Note that a tiny system already exist in a permanent way in small church:- 6 speakers (15watts each) with drive amp 45 watts x 1 channel. since over 1 year.. Just to tell you that we don't need a loud system, Thanks for understanding..

I need answers to questions on first topic, any advise will be mostly apreciated.
 

turk 182

Member
2012-10-26 3:03 pm
Steeveax
your profile doesn't give any info as to where and who you are.
as far as i can tell from the limited info you've shared you would need an amplifier that is capable of at least 400w or less depending on final volume but headroom in terms of availability to overcome potential losses such as losses from long cable runs despite uprating wire gauge should be considered also speaker sensitivity is a factor.
are you planning to cluster the new speakers or are they being distributed each approach requires different wiring techniques and each will have strengths and weaknesses that can be utilized in obtaining a final result.
as far as using a hi-fi amp in this application ask your self if the price/quality ratio will lead to any significant benefit.
in this situation there are a lot of good commercial amps for reasonable cost that you should certainly consider
protection features, types of output's (70 v and or low impedance 8,4 ohm) input source selection and balanced or unbalanced inputs
 
Last edited:
Is 400 watts / 2 channel or per channel ? We have 2 channel of 9 sp each.
Cluster ? Yes, NO :- 9 speakers install surrounding 2 central concrete column.
Wiring 50/0.25mm as mains to each speakers circuit and further with 30/0.25 to other speakers.
Not really interested with HI-Fi amp for this system, am just solicited your valuable advise.
For 70v -we certainly take this advise during this year as we have this type of conference twice on yearly basis, If this series/para combinations fail our satisfaction, we probably choice 70v system.

Anyway all of you kindly help me find the good or the best way of helping others.
Thanks for all, May God bless all of you.
 
Last edited:
With three stacks of three speaker in series in parallel, each needing 20 watts, the current is 4.8 amps. For that you would need minimum 18 ga, for long runs you would need 16 ga wire. The amp has to deliver 4.8 amps which leaves out single output transistor pair designs, it has to have at least 2 maybe 3 pairs. Each speaker needs 11 volts at 20 watts, a stack of 3 needs 33 Vrms. Amps are usually rated at 4 ohms these days, so an amp rated at 273 watt (4 ohms) should be able to deliver that much voltage.
Non-hifi amps are called PA amps these days.
 
Thanks, The continuous wattage will be 12 - 15 watts with Peak 20 watts...You suggested an amp 273 watts (4 ohms) That means that the following circuits >> With 9 speakers (8 ohms - 50 watts each) in series/parallel (8Ω X 3 = 24 / 3 = 8Ω) with Resultant Impedance 8 ohms per channel << must be modified to 4 ohms, Please advise.
 
A standard PA amp rated 273 watts/ channel won't deliver 273 watts to your strange circuit. If you want 180 watts (33 volts rms) into your strange load, you have to buy an amp that will deliver 33 volts, which is 273 watts into a 4 ohm load. For example, a PV4 which is 200 watts per channel into 4 ohms, probably won't develop enough voltage.
If you really want to hear some low fidelity sounds, try to get 180 watts out of a transistor based amp that won't develop enough voltage. Clipping is what they call it, a very nasty sound on music. The sine waves get the tops chopped flat, which is awful sounding.
The wire gauges mentioned are for american wire gauge. You have since listed your location, which I don't recognize but your suppliers probably sell metric sized wire. I don't have wire amp tables for metric wire, you'll have to look up the wire manufacturer's website.
 
Last edited:

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
This is very difficult to advise on, for one thing I'm no speaker expert.

Lets see what we can make of it all though. The information you have added (the 2.5 volts rms) I take to be from the test I linked to in post #2. Yes :)

If so, then that equates to an amplifier "power" of around 6.25 watts into 8 ohms. The only difference 4 ohm loading makes (if 2.5 volts rms still give the level you want) is that the amplifier must be able to supply double the power... around 12.5 watts.

If its a venue that will fill with people then absorption will be a real issue so we could safely guestimate that a 40 watt/8 ohm amp should be plenty.
 
[indianajo;3375015] QUOTE:_For that you would need minimum 18 ga, for long runs you would need 16 ga wire
The wire gauges mentioned are for A merican W ire G auge. You have since listed your location, which I don't recognize but your suppliers probably sell metric sized wire. I don't have wire amp tables for metric wire, you'll have to look up the wire.QUOTE...

I found out the following equivalent, Hope it's right !
AWG..........mm...............Metric New standard
18 ............1.02 ..............24/0.25
16 ............1.29 ..............30/0.25
14 ............1.62
12 ............2.05
13 ............1.82 ...............50/0.25 (with this size the entire load remains 8 ohms)

QUOTE:- Wiring 50/0.25mm as mains to each speakers circuit and further with 30/0.25 to other speakers. QUOTE.

Thanks for all...
 
Last edited:
Dear steveax, please define your sound needs with a little more precision.
You speak of a 15x15M room .
You also speak of a 9 speaker cluster "24M away".
Confusing.

Will you put all speakers together (for some reason you don't explain) 24 M away from the amplifiers *or* you want to distribute them all around or as roof speakers for even sound coverage?
What will that room be used for?
Church/dance hall/school/sales room/...... ?
Draw a sketch of the room and where do you want your speakers.
 
Dear steveax, please define your sound needs with a little more precision.
You speak of a 15x15M room .
You also speak of a 9 speaker cluster "24M away".
Confusing.

Will you put all speakers together (for some reason you don't explain) 24 M away from the amplifiers *or* you want to distribute them all around or as roof speakers for even sound coverage?
What will that room be used for?
Church/dance hall/school/sales room/...... ?
Draw a sketch of the room and where do you want your speakers.


Be free to rectify my setup if wrong.
Wish to install in small Religious conference/hall 15 x 15 meters x 3 H: 2 channel of 9 speakers each (Speaker 8Ω - 50 watts each) in series/parallel with Resultant Impedance 8Ω (8Ω x 3sp = 24 / 3 = 8Ω)per channel, the max continuous demand output per speaker is 10 watts with 15 ± watts PEAK from time to time, depends on speech rates (NO crying).

The total length of wires for one channel is 35 meters from amp to last speaker. Just soft talk and some classic music at 15 watts per speaker from time to time.

SPEAKER:- 4- 8ohms 50-100watts
NO Woofer or Sub woofer - Just midrange/ medium
Bass control will set at lesser
Treble control will set at haft
Speakers will be fixed surrounding four central concrete column
at mounting height 2.5 meters from floor

Would like to know: type of amp, output, watts. wiring size.

This conference will be held in two month time.

Thanks for help
 
OK.
***Practical*** no frills answer.

Make 6 small columns with 3 speakers each, wired in series, so each column will be 24 ohms impedance.
You will have 3 such columns for each speaker channel.
Spread them evenly around the room.
You may mentally divide it in 6 sections, as in:
1/2 : Front L/R
3/4 : mid L/R
5/6 : back L/R
Each column should be pointed to one of those 6 room sections, to guarantee even coverage.
Connect all 3 left columns in parallel using 2 x 1 MM "220V type" cable, to the left channel, which will see an 8 ohms load.
Do the same on the right side.
If you can afford 1.5 mm or 2mm cable, even better, but if not, power loss into a 24 ohms speaker, only 15 meters away is nil.
And if the speakers in the back are actually slightly attenuated respect to the front ones, even better.
A 2x100W amplifier is more than enough.
In fact, any cheap 100W/4 ohms (obviously mono) powered mixer box will probably be enough to drive all 18 speakers.
But if you want to use more power, be my guest.
I have made tons of similar installations in small Churches, or larger Shopping Malls, etc.

Getting into line transformers and such is fine, but in much larger/complex situations, such as multi-story Hotels, Shopping Centers, Hospitals, etc.
Not *really* needed within a 15 x 15 meters single room.
 
Hi JMFahey
Make 6 small columns with 3 speakers each, EXACTELY
wired in series, so each column will be
24 ohms impedance.

You will have 3 such columns for each I'LL DO IT
speaker channel.
Spread them evenly around the room.

You may mentally divide it in BE SURE IT WILL BE
6 sections, as in:
1/2 : Front L/R 3/4 : mid L/R 5/6 : back L/R

Each column should be pointed to one of YES
those 6 room sections, to guarantee
even coverage.

Connect all 3 left columns in parallel using IT WILL BE
2 x 1 MM "220V type" cable, 30/.025mm SHORT RUN
to the left channel, which will see an 8 ohms load.

Do the same on the right side. NO PROBLEM

If you can afford 1.5 mm or 2mm cable, LONG RUN 50/0.25mm
even better, but if not, power loss into a
24 ohms speaker, only 15 meters away is nil.

And if the speakers in the back are actually OK
slightly attenuated respect to the
front ones, even better.

A 2x100W amplifier is more than enough. OK

In fact, any cheap 100W/4 ohms SHOULD I CONNECT TO 4 OHMS
(obviously mono) powered mixer box AMP OUTPUT WITH 2 CHANNEL
will probably be enough to drive IN PARA, WHEN YOU SPECIFIED
all 18 speakers. 100W - 4 OHMS OBVIOUSLY MONO ?

But if you want to use more power, be my guest. THANKS
I have made tons of similar installations in
small Churches, or larger Shopping Malls, etc.
Getting into line transformers and such is fine,
but in much larger/complex situations, such as
multi-story Hotels, Shopping Centers,
Hospitals, etc. Not *really* needed within THANKS FOR CONFIDENT YOU
a 15 x 15 meters single room. MAKE ME FEELING...

QUESTION: can I connect a sub amplifier from PRE-AMP or LINE-OUT of Master
amplifier, to drive speakers over Stage as return speakers ?


I REALLY APPRECIATE YOUR VALUABLE HELP, SINCERELY AM VERY HAPPY FOR YOUR
EXCELLENT AND TECHNICAL SUPPORTS.

Thanks once more for all.