Audio Amp HELP !!

[loowee]

Hello guys !

We are helping a customer with an amplifier problem that tried to setup his system himself but called us after 3 amps fried !
Since we do not specialize in audio and we mostly install pre-amplified systeme such as Grand-Concerto, I need some help with power ratings and tips for a good amp.


Here's the story :

- This one has 24 speakers in-ceiling and they all are 90w rated

- These 24 speakers are distributed trough 12 differents zones with volume controls that are all setup @ 2ohms

- The receiver input ( XM + FM ) is a Sony Stereo receiver that has 100w rated output per channel ( 200w total )

- He also has a 600W Sony Xplod car amp ( powered by a PC PowerSupply 12V ) that is connected after the Sony receiver so if my calculations are right, we have a rough 800w of power for a requirement of 2160w ( 90w x 24 speakers ).


My questions are :

- Am I calculating all this the right way ? I know Ohm's have to be taken in consideration but dont know how the formula works

- Should I just install a stronger 2000w car amp instead of the 600w Xplod and this will do the trick ?

- Any suggestions for a good strong amp that would provide enough power for a budget around 200$ ?

Thx guys !

 

[WayneW]

The speakers may be rated to handle 90W, but they don't need or draw 90 watts (at normal volume levels). So, you can pretty much ignore that number unless you are trying to do very high volume stuff.

They probably burned up their amps by having too low a resistance load. When you wire speakers in parallel, the resistance/impedance drops. His amps are probably only rated down to 4 ohms, maybe 2 ohms at the lowest.
But if the customers has a bunch of speakers and/or volume controls wired in parallel, they are probably only giving the amp a .5 or 1 ohm load and the amp fries.
Basically, some of those speakers will need to be wired in series to keep the resistance/impedance in the range supported by the amplifier.

 

[jwilson56]

Also that 2 ohms is a nominal rating as it really is an impedance so it could got lower than 2 ohms when your playing music. Most amps will not handle that low of impedance. Also if you plan on staying that low the speaker wires will start to become a problem unless you running low gauge wiring for the longer runs.

What is the actual impedance of each speaker (4 or 8 ohm is normal). They do make high end multiple zone speaker impedance matching equipment that can help keep things in order.

I myself stayed away from this type of configuration. I wanted a true multizone setup that could play different sources in each zone. This is not the first nightmare story I have read about when multiple speakers are being used.

Here is a good article that might help

http://www.smartbuyspeakers.com/multiple_speakertech

 

[DavidL]

Are you sure the "PC" power supply can supply enough current to run the amp? Why use a car amp?

 

[felixrosbergen]

wiring in series but letting each zone have it's own volume control sounds like a problem to me.

Time to do the math and likely get several smaller amps i would think.

 

[loowee]

Problem solved guys, we adjusted OHM settings on all volume controls and set up the amp in bridge mode...
Thanks to all cocooners for these helpfull tips !

 

[felixrosbergen]

but still an example of probably how not to plan a system... with many zones shut off..isn't the draw of the main amps grossly disproportionate to the speakers?

Unless you have parties all the time when all zones are active i would think multiple smaller amps or a multichannel amp would work a lot better.