Increase PA System Volume

[dmlee]

I purchased a cheap PA system online. Didn't expect much from it but the volume is way too low. You can only hear the person clearly if you're standing a couple feet away...which obviously defeats the purpose of a PA system.

I've taken pictures of the circuitry and was wondering if anyone can think of a way to increase the volume by replacing a chip or adding something. The only thing I could figure out is that 2 of the chips are amplifiers (last pic). I have no idea whether all I have to do is replace them with higher wattage chips or if I'll have to replace other things or if that'll even fix the issue.

If you need more details I can always open it up and take better pictures.

Microphone Front
**broken link removed**

Microphone Back
**broken link removed**

Speaker
**broken link removed**

 

[Sceadwian]

10 watts would be 'loud' from that distance, you're not getting 10 watts out, which begs the question what is the impedance of the speakers you have attached to the amplifier? The TDA2003 is only rated at 10 watts with a 2ohm load, which means automotive type or otherwise very low resistance speakers. If you're connect this to common household speakers which are often 8-16 ohms the only way to increase performance is to put more speakers in parallel.

Pictures of the speakers you're using might help as well, but impedance is most important.

 

[dmlee]

I have no idea what the impedance is. If you can let me know how to figure it out I'll post it.

This is the system that was bought. It's for our company. We wanted a cheap and easy way to inform employees of stuff like "We will be conducting a meeting in the conference room" etc. Doesn't need to be extremely loud but cmon... you should at least be able to hear it up to 25 yards away.

**broken link removed**

 

[Sceadwian]

25 yards away? That's 150 feet, in what type of environment? I think you may be drastically misunderstanding your requirements. The amplifier you purchased with even decent speakers may be difficult to pick up at 150 feet in anything more than modest ambient noise.

 

[audioguru]

25 yards away? That's 150 feet.

Your math is wrong.
25 yards is only 75 feet (across a small street) where a PA system is not even needed because you can easily shout across a street.

The PA system that was purchased is CHEAP. That is the problem.

 

[Sceadwian]

Wow, it's late =\ Yeah my math was way off on the distance. I'd still wager money that they primary weakness is the speakers, if you can put the maximum possible output of those two chips out to a pair of 2 ohm speaker loads you get 20 watts out (not the greatest quality mind you) but 20 watts should still be passably useful. But you have problems with wire runs then because the resistance of the wire runs becomes a large source of power loss. This is why most PA system are based 50-100 volt signal levels. The 10 watts at 2 ohm load means the voltage out is only about 1.2 volts RMS...

I'd be reticent to call that a power amplifier at all, other than technically speaking.

 

[Sceadwian]

As far as impedance with PA systems go (and only PA systems) you can generally measure the nominal impedance by using a DC multi-meter on the lowest ohm setting. Check the DC resistance of the + and - terminals of the speaker (disconnected from the amp) and report the results.

 

[audioguru]

The cheap speaker looks like a tinny-sounding horn which usually is very efficient at medium to high audio frequencies. But the horn is not a normal very efficient re-entrant horn speaker, it looks like a normal cheap speaker with a plastic housing in front.

I think the amplifier uses the 2 ICs in a bridge to double the voltage swing.
The cheap power supply probably has a 5W rating so the power to the 8 ohm horn is probably only 3W with 2W of heating in the amplifier which is shown in the tiny size of the heatsinks.

I found this CHEAP PA system in Google selling for $5.67US.

 

[4pyros]

I purchased a cheap PA system online. Didn't expect much from it but the volume is way too low. You can only hear the person clearly if you're standing a couple feet away...which obviously defeats the purpose of a PA system.

I've taken pictures of the circuitry and was wondering if anyone can think of a way to increase the volume by replacing a chip or adding something. The only thing I could figure out is that 2 of the chips are amplifiers (last pic). I have no idea whether all I have to do is replace them with higher wattage chips or if I'll have to replace other things or if that'll even fix the issue.
That thing is fryed. One of the 1K resisters is burnt. it looks like a cap blue apart and thare are other chared components in the amp. No wounder its not that loud.

If you need more details I can always open it up and take better pictures.

Microphone Front
**broken link removed**

Microphone Back
**broken link removed**

Speaker
**broken link removed**

That thing is fryed. One of the 1K resisters is burnt. it looks like a cap blue apart and thare are other chared components in the amp. Looks like one of the legs is blown off the out put chip. No wounder its not that loud.

 

[dmlee]

25 yards is only 75 feet (across a small street) where a PA system is not even needed because you can easily shout across a street.

Just to clarify, our production area is separate from the administration side and we were trying to make it easier to communicate information to them.

That thing is fryed. One of the 1K resisters is burnt. it looks like a cap blue apart and thare are other chared components in the amp. Looks like one of the legs is blown off the out put chip. No wounder its not that loud.

This unit is dead. I had it replaced and haven't returned the bad one yet. Another working unit is currently hooked up. I only took pictures of the dead one for circuitry purposes.

 

[dmlee]

As far as impedance with PA systems go (and only PA systems) you can generally measure the nominal impedance by using a DC multi-meter on the lowest ohm setting. Check the DC resistance of the + and - terminals of the speaker (disconnected from the amp) and report the results.

Will do as soon as I can.


So you guys are saying one thing or another is not good (powerful?) enough. Do you guys have suggestions on what to replace with or do you have to know what the impedance is first? I know this is a cheap unit. I'm used to diy projects and usually there's a way to improve things.

 

[alec_t]

What is the power source? Voltage?

 

[4pyros]

Just to clarify, our production area is separate from the administration side and we were trying to make it easier to communicate information to them.

What is your production? How loud is the production?

 

[dmlee]

What is the power source? Voltage?

12v on a 110v to 12v converter.

What is your production? How loud is the production?

I'd equate it to about 20 people talking on the phone. I'm not worried about the level of noise since we'll be repeating the announcement and once someone hears it they'll tell everyone else to shut up.

Also been busy so haven't found out the impedance yet but will post once it's figured out.

 

[audioguru]

So you guys are saying one thing or another is not good (powerful?) enough. Do you guys have suggestions on what to replace with or do you have to know what the impedance is first? I know this is a cheap unit. I'm used to diy projects and usually there's a way to improve things.

When we find out the impedance (resistance) of the speaker (probably 8 ohms) then a huge increase in volume will occur if you replace the cheap speaker with a half-decent PA re-entrant horn speaker. But if the microphone can hear the speaker you will have acoustical feedback howling.
Here is one that sells for $39.00US.

Electronically, you can increase the power of the amplifier if you use a bigger power supply and bigger heatsinks on the amplifier ICs. Then the cheap speaker you have now will soon burn out.

 

[dmlee]

Thanks for all your guy's help so far.

Just another bit of info.. the thing comes with built in "sirens" aka car alarm type sounds. Those sound plenty loud. Is this because they're just tones?

 

[Sceadwian]

Sounds like the 'speakers' you got are actually piezo units. You're never going to get any kind of quality audio out of what you have.