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using more speakers than the unit is made for

arrishort555

Standard Member
hello, im aaron and im a newbie on this forum so be nice!

as title says. is this good for the speakers etc and whats the best way?

atm i have a panasonic hihfi that can only take 2 speakers but i have 4, its working fine atm but will there be problems or is there an easier way to do it?


cheers
 

PSM1

Distinguished Member
This all depends on how you have connected the speakers and what resistance they are.
If you have 2 8ohm speakers in series then it is like having one speaker at 16ohm but if in parrallel it is like having a 4ohm speaker connected. If your amp is designed for 8 ohm speakers then the lower 4 ohm combination could cause the amp to overheat and cause damage over time to the amp. The 16ohm way could just make the speakers sound quieter but could cause damage to the amp too.
 

BlueWizard

Distinguished Member
This is an extremely difficult question to answer, but as PSM1 points out, it is not so much about the quantity of speakers, as it is about the resulting load impedance of adding those speakers to the amp.

Speakers in series add -

Rt = R1 + R2 + R3 + ...

Example, 6 ohms, 8 ohm, and 8 ohms -

Rt = 6 + 8 + 8 = 22 ohms

Speakers in parallel divide -

In this case, we take the impedance of one speaker, and divide it by the numbe of speakers -

Rt = R1/n

But this assumes speakers of equal value.

Example, three 8 ohm speakers -

Rt = 8/3 = 2.67 ohms

For TWO speakers of unequal value, we use this formula -

Rt = (R1 x R2) / (R1 + R2)

Example, 6 ohms and 8 ohms -

Rt = (6 x 8) / (6 + 8) = (48) / (14) = 3.43 ohms

MOST, amps can tolerate a load per amp channel of 4 ohms to 16 ohms. If ti drops below 4 ohms, the demand for electrical current gets to high, and the amp tends to overheat. If the impedance goes above 16 ohms, the amp tends to become unstable, and is prone to self-oscillation, which is similar to feedback.

Now some cheap amps have a problem with loads as low as 4 ohms. Some better amps can tolerate total per channel loads slightly below 4 ohms. The best consumer amps, as well as commercial PA amps, can easily handle very low loads, but you are not likely to encounter amps like this.

Though there is one exception, NAD amps. Even the very low cost NAD C315 has its dynamic power rated as low as 2 ohms, though I would certainly not recommend trying to run that low. But it indicates that the amp would be very stable running difficult 4 ohms loads, and should even tolerate a 6 ohms combined with an 8 ohms speakers.

So, it is not about the number of speakers, but about the combined impedance load that those speakers present to each amp channel.

In your case, the amps seems to be tolerating a pair of speakers on each channel nicely. Most amps have protection circuits, so if you are overheating the amp, or running it over current, it should shut itself down safely.

Steve/bluewizard
 

arrishort555

Standard Member
the base unit is a panasonic as-ak45
with two of the stock speakers and one mitshubushi from an old sa582 stereo and one sony from a old base unit.
one of the mitshbushi speakers wasnt working so i took it apart for spares.
so i will hopefully be building my own speaker soon and adding even more!!
ive heard of a box that plugs into the back that gives you more sockets?? is this true and how much?

cheers:thumbsup:
 
the base unit is a panasonic as-ak45
with two of the stock speakers and one mitshubushi from an old sa582 stereo and one sony from a old base unit.
one of the mitshbushi speakers wasnt working so i took it apart for spares.
so i will hopefully be building my own speaker soon and adding even more!!
ive heard of a box that plugs into the back that gives you more sockets?? is this true and how much?

cheers:thumbsup:

Aaron, you seem to have got away with it thus far, I think if you carry on it might be a case of one speaker too many.

If you do, take heed of bluewizard's earlier fine explanation.:smashin:
 

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