I currently own the Sherwood RX-4109 stereo receiver and I was wondering that is it totaly ok to connect just one pair of 4 ohms speakers to this receiver? I' am pretty sure there will be no problem doing it right? Since speakers are just speakers and they are made to connect to any receiver.
NO!, you can just connect any speakers to any receiver. Different impedance on different speakers as well as different power outputs on receivers lead many to be incompatible unless you add your own resistors or tweak other stuff. If you connect 4ohm speakers to an amp that can handle only 8ohm, it can lead to bad things.
Its got nothing to do with technology, this stuff has been around for many decade, its about how good the product is. If your amp is designed for 8ohm impedance, and you hook up 4ohm speakers, it'll fry itself. Expensive amps can withstand 6ohm, 4ohm and some even 2ohm. If you connect a resistor to your speakers to make them 8ohm, it will work.
that is just it , it comes down to how good your equipment is , i wouldn't expect a sherwood to be that good ,but it is hard to say until you try . now it also depends on how hard are you going to push the 4 ohm speaker . if this 4 ohm speaker is low wattage it is probably safe. now if you are talking about a car subwoofer it may not be such a good idea , for your amp's sake. now alot of yamaha's receivers are capable of 6 and 4ohm loads and few even down to 2 ohms . part of the problem with running a lower ohm load than what the amp is designed for is that lower resistance means more wattage which means more heat and stress on circuits , some amps just simply are not stable in these conditions.if you have an amp rated at 100 watts at 8 ohms and you connect a 4 ohm speaker you have now cut the resistance in half so the potential to flow double the wattage now exists and most likely the amp will try to produce more wattage .now if you want to play it safe and have 2 of these 4 ohm speakers you could wire them in series maybe and have them in series present a 8 ohm load to the amp . i have had quite a few receivers and stereo systems over the years and yamaha's receivers has treated me the best. hope this helps you understand , if you try wiring these in series and want to confirm that you have done it right a volt meter set to read ohm should read within 1 ohm of your target number if correct.
it is more expensive to build an amp that can work with more than 8 ohms.
the result is dependant on the capacitors being able to remain stable, as well as the power supply that feeds power to the capacitors.
if the caps will work, that doesnt mean the power supply will allow the extra amperage through.
and resistors or other things also have to be able to handle the extra load.
to an engineer.. it could look something as simple as having a 100 watt amplifier with 200 watt pieces inside of it.
and if you ask for all 200 watts, those pieces might be at their limit and fail.
maybe you need 250 watt or 300 watt pieces inside of it to help make the pieces last.
i think the pieces are getting less tolerant to fluctuations.
they are ment to do one thing only.. and it is supposed to be cheaper as well as give the ability to make the piece do one thing better.
if the situation is calling for double the work effort, the power supply might start to get cranky and the whole flow of electricity stalls.
it is a team effort, and all teams are only as good as their weakest link.
I have a Sherwood 6500 (same amplifier stage,but multichannel), and design speakers. The sherwood will go into "protect mode" if a 4 ohm "minimum" impedance is reached. The nominal impedance isn't the part thats critical. Anyway try the speakers you have and if your ampifier shuts off when the amplifier "clips" you need to make other arrangements.
I believe sherwood suggests a 6 ohm nominal or higher as a safety margin.
If your using a seperate subwoofer, you can try using " bass blockers" in series with the speakers you have to releive impedance dips at low frequencies. Anyway good luck, I like sherwood equipment , but it does have limitations.
but i think jimbates has given the best advice thus far.
most of the impedance dips are towards the bass frequencies.. so if you use a bass blocker to block the bass.. you will also block the low impedance the amplifier would see.
since everybody and their cousin wants junk 2-way speakers with no bass output.. everybody should use these bass blockers to keep their amp safe (or out of protect mode)
if your receiver has a digital bass blocker for the speakers, you might be able to use them in replacement for the bass blocker.
maybe your digital bass blocker doesnt go high enough..
maybe some low frequencies still do happen because of overtones with the speaker cone movement.
those impedance curves are for ONE tone at a time.
when you start to combine one tone on top of another one.. overtones happen that can drop the impedance again.
that bass blocker can actually give an injection of electricity during those moments the impedance drops.
just check to make certain the added bass blocker doesnt drain dead OR drop the resistance to something dangerously low when a cap does go dead.
about the more or less expensive..
when you are driving high ohm speakers, you need a bigger torroidal coil.. and more voltage across the entire amp, all the way until the voltage leaves the amp from the speaker outputs.
if the high voltage parts are cheaper than the lower voltage parts (with the same sine results)
then the high watt amplifiers would be cheaper to build than the 100 watt per channel versions.