Axiom Home Page Forums General Discussion Technical Questions 4 ohm towers Hooked to 6 ohm amp

I am a new user and have just completed my HT. Speakers Axiom system 80 hooked to Pionneer Elite vsx94txh,Elite Blue-ray
BDP-05FD,Epson Pro Cinema 1080UB front projector on Goo-system
screen.It "ROCKS MY SOCKS".I have the AV set at 6 ohms The towers
from Axiom are 4 ohm. I think this quality amp can handle it or Am I wrong.Cannot push the amp(140RMS) to the limits without blowing the door off the dicated HT Room. ( 12.1W x 20L X 8.5H )
Do I run the risk of damaging the amp and/or speakers.
Thanks

If your amp is not shutting down, you're cool. Congrats!

You could also try the AV in 8ohm mode as the 6ohm setting is just limiting the amps output to prevent it from overloading.

Either way glad you are liking the new system.

Thanks: I am working on sound panels to deal with the reverb in this lively room.

What those guys said. Unless your amp distorts (sounds bad) or shuts down, just enjoy it.

Sirquack had a really good pictorial essay about his adventure with room treatments (corner bass traps and other panels). Do a forum search on "Room Treatments" and you'll probably find more than you want to know.

I would turn your receiver back to the 8ohm setting, no matter the ohm rating of your speakers.

I'll just put my 2 cents in here...

P=I2R.

The amp is rated for a power level at 8 ohms. If you cut the ohms in half, you must increase the current by SQR(P/R). So, if your amp is 100W rated, in normal 8 ohm operation, it would supply SQR(100/8)=3.5A. Change the load to 4 ohm, it would have to supply SQR(100/4)=5A. 43% more current.

Some amps can handle it, some can't.

I know that some of you may believe that "if the amp doesn't trip" it's okay, and I also know that most of you know that the 8/6 setting will reduce the current limit, thereby reducing your peak power. But, it's there for a reason... Distortion.

Distortion has a better chance of damaging your speakers than connecting an amp rated higher than your speakers. Notice how all torture test blow the speakers using white/pink noise?

Even if the speaker doesn't blow, it most likely will clip the higher power levels. Not a true reproduction of sound.

I would recommend (albeit in contrast to many on this board) to use the 6 ohm setting.

From Gene at Audioholics...

"NOTE: Some Receivers have an impedance selector switch. DON'T USE THEM! The manufacturer puts them there for UL approvals as well as easing consumer concerns about driving low impedance loads. These switches step down voltage feed to the power sections which will limit dynamics and overall fidelity. Keep the switch set for 8 ohms regardless of the impedance of your speakers and ensure proper ventilation of the Receiver.


Update: 09/06/05



Upon further investigation on this topic we have discovered that in most cases the switch is doing nothing more than reducing the rail voltage. Please check out our measurements on page 2 of the Yamaha R-XV4600 review for more information on this.

As you can see the measurement differences between the "low" setting (less than 8 ohms) and the "High" setting (8 ohms or more). This is the reason I usually recommend keeping this switch in its default "High" setting and using common sense when mating a receiver with inefficient 4 ohm speakers in large rooms.

All the "Low" setting of the switch is doing is stepping the rail voltage down so when UL tests the amp at a specified distortion level, the amp will achieve that distortion level sooner since it runs out of headroom more quickly than it would in the "High" (8 ohm or more) setting. This in turn generates less heat since the amp isn't driven as hard. You really aren't buying any protection for driving low impedance loads as you actually risk clipping the amplifier more since it can run out of headroom more easily. The switch is there more for certification purposes. The reason you don't see this switch on separate amps is twofold:

They typically have more heat sink area, and bigger power supplies and can better manage the heat
They aren't UL certified and don't have to meet the requirement. "

I was just looking for that very same article.