I am Not hurting anything right ??


I have a pair of Sonus Faber Concertinos that have bi wire posts. I have Bi wire Cable but have told NOT to Bi wire these Speakers. so I left the jumpers on the back and pluged in the cable as normal(standard bi wire configuration). Speakers sound great. But am I running any risk as to damaging the speakers?

Best Regards
vongwinner

Showing 2 responses by sqjudge

I used to teach basic electronics at a Vo-tech. I feel a need to clarify the bi-wire issue because I believe that some do not understand the electrical circuit. As Sean describes above a true bi-wireable speaker has a electrically separate crossover for each driver. Most speakers have separate crossovers for each driver but they are not electrically separate because the input to both of the crossovers (in a two-way speaker; one a high pass to tweeter, the other a low pass to the woofer) are tied together to the single pair of input jacks on the back of the speaker. In a bi-wireable speaker, if the jumper is removed between the two pairs of inputs and only one of the pairs has hooked up, then only one speaker will produce sound. This is a sure fire way to see if the crossover sections are independent.

Sdcampbell you are partially correct that you are feeding the same VOLTAGE to both sections of the crossover. Both pairs of wires connect to the same + & - terminals on the amp and then each pair of wires is connected to the drivers thru the crossovers. This is like connecting two toy DC motors to a single battery, both motors will 'see' the voltage and both motors will turn.

A speaker is a current driven device. The current flowing thru the voice coil reacts with the magnet to produce movement of the cone. (yes, I am sure you all know this but I am only trying to be complete) It is the job of the crossover to direct the appropriate audio current into each driver. This is done by what is called the voltage divider principle. This principle is based on Ohm's law that states the current flowing thru a circuit is proportional to the voltage applied and inversely proportional to the resistance. If you were to take two 6 ohm resistors and connect them in series and place them across a 12 volt battery, 1 amp of current would flow. (ohm's law) If the resistors were doubled in value then the current would be cut in half. Now, lets look at the voltage. The voltage across one of the resistors is determined by taking the current thru it (1 amp) and multiplying it by it's resistance (6 ohms) to arrive at a voltage of 6 volts. The 12 volt battery has been 'divided' down to six volts. The crossover in series with the speaker works the same way, only it is frequency selective. In the case of the woofer crossover, it only 'passes' the low frequency voltage to the woofer and blocks the high frequencies.

The major advantage to stretching separate wires to the woofer and tweeter is the separation of the audio frequency currents in the wires. Even though the voltage is the same on both pair of wires, the currents are not. If speaker cables were perfect, then we would hear no differences in cables. If they were perfect, it would not make any difference if both high and low frequency currents flow in the wires. It is the separation of the currents in the cables that does the most to affect the sound. Does it not seem possible that the large woofer currents could affect the small tweeter current while it traveled down the wire? It is the fact that the currents are different that makes me think one could 'tune' their speakers by using different cables on the top and bottom.

A manufacturer might not recommend bi-wire because he has voiced his speaker to take into account the interaction inside the single cable. (I am not sure how this could be done, but it always possible) If everyone were to follow recommendations, why would anyone try a different cable than the one recommended. I believe the answer is found within the context of taste. I like my 'sound' to be a certain way. I position my speakers and use 'xyz' brand equipment to make them sound the way I want. Just because a manufacturer doesn't recommend bi-wiring, does that automatically mean that I won't like it that way? It is a personal choice and I feel strongly about the option to make that choice! If I feel a speaker sounds better upside down, what is wrong with me using it that way?

I want to thank all of the Audiogon posters for their comments about the sound of equipment in this and other posts. I reside in the middle of no audio land. I really like to read the opinions of others on equipment. I believe our motives for saying something good or bad about a piece of gear is at least NOT ruled by our paychecks!

I really hope this dissertation sheds light on the bi-wire topic and will help guide all in the pursuit of good sound.
Paulwp as others have said, the voltage is the same on both pairs of wires but the currents are not. To get a grasp of this think of a tiny electric motor and a really big motor hooked to a battery. Because of the impedance difference in the motors they will draw different currents from the battery. If two resistors were hooked to a battery the amount of current flowing thru the resistors would depend on their values.

In a tweeter if it was connected directly to the amp, it would try to move with the bass. It would probably quickly burn out. The crossover (the simplest is just a cap in series) acts as a high impedance at low frequencies and because little current flows in a high impedance circuit no force is generated on the cone of the tweeter at low frequncies.

In the woofer the crossover (just a coil in the simplest) as the frequency gets lower the coil passes more voltage to the woofer which causes more current to flow thru it. In other words at really low frequencies the woofer 'feels' all the voltage that the amp puts out.

To sum this up, at the crossover input terminals both high pass and low pass sections see the full voltage of the amp. At the output of the crossover (the driver terminals) only part of the full amp voltage is felt which is totally dependant upon the frequency. Since the voltages applied to the drivers terminals change with frequency so does the current. It is this change in current with frequency in the high/low pass circuits (which include the wires) that I was describing.

It should be easy to rationalize that the big currents flowing thru the woofer could not possiably flow also in the tweeter circuit or it would surely burn it out. If the speaker is connected with only a single pair of wires then both woofer & tweeter currents are combined at the amp but get seperated out in the crossover. In a bi-wire speaker the currents leave the amp together but get sepersted out at the amp terminal and only the tiny high frequency current flows into the wire connected to the tweeter crossover.

Hope this helps ... I will be out for 5 days and therefore can not respond unless I get on the net in Az. Chris