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Simple ohm questions

 

New member
Username: Tigercrest

Post Number: 1
Registered: Mar-05
When I hook up my 2 old 8-ohm speakers to my amp's speaker connections that are rated at 6 ohms, this shouldn't cause a problem, right?

This amp also has RC plugs for "surround speakers" that say 16 ohms. Speakers should never have fewer ohms than the amp they're plugged into, right?

Not trick questions--I just have not learned much about electricity--though I sure can spell well. Thanks.
 

Silver Member
Username: Cheapskate

Post Number: 129
Registered: Mar-04
i seriously doubt that it would. everything i've heard recommends against using speakers too low impedence for the amp, but not too much.

i'm currently using 8 ohm speakers with my yamaha boombox that was designed for only 4 ohms and have run 6 ohm speakers at full volume for extended periods with no incident.

the diference between 6 and 8 ohms isn't that great.

i'd worry more about using 8 ohm speakers in your surround channels. maybe the surround channels are lower output than the mains and the 16 ohm rating is internal to allow more power for the front amps.

i've never heard of a 16 ohm speaker except maybe in multiple speaker PA arrays.

are your surrounds dolby digital, thx or dts or are the dolby pro logic? i'd bet that it's an older pre digital reciever and that 16 ohm surrounds are it's normal mode.

you should contact the manufacturer if you don't have your owners manual anymore.
 

Unregistered guest
If I am trying to update an old PA setup and the speakers say 45 ohm but the amp is 8 ohm is this ok
 

Pentode
Unregistered guest
If you had a 6ohm tube amplifier and plugged in 4ohm speakers it would be better than using 8ohm speakers (with tube amps, a little lower is better than a little higher) but with a transistor amp it is the opposite (a little higher is better than a little lower). A half-decent amplifier (tube or transistor) will cope with small differences in impedance. The main issue with matching impedances is for sound quality.
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 3598
Registered: May-04


"The main issue with matching impedances is for sound quality."

Sound? Not stability? With transistors?



What exactly is a "6 Ohm tube amplifier"?






 

New member
Username: Sethmckiness

Des Moines

Post Number: 1
Registered: May-05
What I believe Pentode was eluding to was every amp is designed around a certain power envelope and load. the Load is the speaker. For a Transistor Amp you will never damage it by going to a smaller load, ie higher ohm. Now, a higher quality Amp will push a greater load then designed if done carefully.

I have run 2.3 ohm loads on a cheap 2 channel reciever that did have a mosfet design that was rated at 8 ohms.

I would just watch the amp, be aware of it's temperature and the condition of the power supply..
 

New member
Username: Audio101

Battle Creek, MI USA

Post Number: 2
Registered: May-05
Mark,
You asked:
"When I hook up my 2 old 8-ohm speakers to my amp's speaker connections that are rated at 6 ohms, this shouldn't cause a problem, right?"

If you are asking: Can I connect one speaker rated at 8 ohms to one amplifier speaker output rated at 6 oms?

The real answer to your question is: Yes, you can do this safely.

If you are asking if you can connect two speakers rated at 8 ohms in parallel to this 6 ohm output channel, the answer is: No.

The amplifier output impedance rating is the LOWEST load the amplifier is designed to handle on a long-term basis. It is primarily a statement of how much current the amplifier channel can supply to the load (your speaker). So, you should not connect any speaker load lower than 8 ohm to this output. (Paralleling speakers will LOWER the impedance of the load. Example: two 8 ohm speakers in parallel will present a 4 ohm load to the amplifier; this is less than the 6 ohm load limit.)

I hope this helps you.

John Loser
Audio101 Consultants
 

New member
Username: Cshorter

Atlanta, GA USA

Post Number: 1
Registered: May-05
A couple related questions:

What is the nominal voltage that home stereo systems operate at?

I ask to preface my next question.

I've got a crappy little Sony home theater system with 6 ohm speakers, and no A/B switch. I'd like to hook up some 8 ohm speakers to the front two channels, for use on my back deck. I don't see a problem doing this in an either/or situation, but I'd like to drive them in parallel. Obviously doing so will drop the impedence seen by the amp to 3.4A, which is no good. I ask about the voltage to see if I can't just add another 3 ohm load to the circuits in series to bring the current down. Is this reasonable or preposterous? I don't need to make a booming system out of this...
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 3719
Registered: May-04


The problem you are not addressing is the fact that speakers are not always a constant impedance. Depending on frequency the impedance may be quite a bit higher or, more importantly, lower that the "nominal" impedance the manufacturer lists. Buying a speaker selector box with a large resistor as a "safety" may make the situation work, but there is still the risk of damage to the amplifier if volume levels are pushed. An impedance matching transformer is the best solution.




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