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View Full Version : OT Driving Cheap Speakers 3 ohm/ 6 ohm



garagemark
04-16-2013, 04:32 PM
I have a cheap surround sound system in my fifth wheel. The receiver went bad so I replaced it with another cheap system. The "plan" was to replace the 6 ohm speakers with the new 3 ohm units, using the existing ceiling mounted covers. But!....

The Chinese used an inordinate amount of glue to make getting the old speakers removed from the cases almost impossible. So, I either (and probably) destroy a case or two getting the old speakers parted, or I try to drive the old 6 ohm speakers with a receiver designed for 3 ohm speakers. Or, I spend more money for correct speakers (a very poor option).

Though I am an electrical guy, I don't normally play with anything under 480 volts, and usually work with 13.2kV, so I need help with this electronic stuff! Can I drive the 6 ohm speakers with the 3 ohm amp, or am I just hosed?

I am standing by with a Dremel tool to mangle the pretty white cases on your command.

garagemark
04-16-2013, 04:46 PM
Never mind, I found my answer... bleh!

darryl
04-16-2013, 06:14 PM
Yup. You can drive a higher impedance than an amp is rated for, with a loss of maximum possible output. In many cases you will never hear the difference.

Bruce Griffing
04-16-2013, 08:29 PM
One question is "can a given amplifier drive a given speaker impedance?". I don't know your amplifier, but it is probably capable of driving the 3 ohm speakers. If not, you could add some series resistance (at a slight loss in audible sound level - but of course this will change the damping factor). But the question of how it will sound is another animal. This link discusses one of the problems - damping factor. It is an old story, originally written for a tube type amplifier, but applicable none the less. Matching the speaker and amplifier, speaker enclosure and room (or truck) is something most folks don't bother to do because they don't know it can be important to sound quality. Here is the link if you are interested.

http://www.paulspeltz.com/tomcik/

darryl
04-16-2013, 08:57 PM
I see that you made two references- one was to replace 6 ohm speakers with 3 ohm, and the other was to drive 6 ohm speakers with a 3 ohm amp. Maybe you're really asking if the existing speakers can be driven with the new amp- or maybe you want to use the new speakers (3 ohms) with the new amp-

Since you have suggested that this is a new 'system', the speakers that come with it must be a safe load for the amp. The 6 ohm speakers will be an even safer load for the new amp. But maybe the new speakers are better than the old ones, and would give you better sound- that could be true. Seems like it would be a rather destructive process for you to make the swap, so - well it's your call which way to go. Very often you can't put a replacement speaker in an existing cabinet without messing up the frequency response, so even if the new speakers are better, they may not sound better in the old cabinets.

My gut feeling is don't change the speakers.

By the way, I've spent decades working with vehicle and home sound systems, and I don't recall ever seeing a vehicle system that wasn't rated to drive 4 ohms (3 ohms, close enough) Almost every speaker for vehicle systems is rated 4 ohms and not 8 (or 3 ohms, not 6). In pretty much every case you could replace an 8 ohm speaker with a 4 ohm and not hurt anything. You do have to be careful once you start adding second pairs of speakers to systems-