I am new to HT, so pardon me if this is dumb question.

What is the use of bi-wiring speaker cables? Are they only used if you have an amp that uses A and B Channels or if you Bi-Amp.

Let us say I have a regular recvr like an Onkyo 595 and I buy speakers that are bi-wirable, would I benefit by bi-wring them??
After several researches and trials, I've realised that biwiring your speakers can bring you more disadvantages than benefits since it changes an equivalent circuit of speaker-crossover combo. Another words your speaker cables become more to participate as a part of a speaker-amplifier circuitry adding more reactance. Reactance is non-ohmic components of overall impedance which we usually do not want to deal with in ideal case.
My first and the last experience with bi-wired cables was the following: I simply used the same cables in the single-wired setup in different positions: lower binding posts -> jumpers to upper binding posts and the same with upper binding posts and then trivial bi-wired connection. The first result brought me forwarded bottom and lower-midrange. The second result brougt me forwarded top-end with upper-mids which is certainly much brigher than the previous. The third result was balanced but everything was too airy with no presentation. Finally I've sold biwired and staying with bare wires threaded through the holes of the WBT binding posts of my speakers with no jumpers -- simply the best connection that I could think of.
Extra pairs of binding posts on your speakers can give you an advantage of biamping them rather than biwiring. There are some ideas to use for bottom end one pair of single-wired cables and for top-end another pair with best-on-your-ear matched brands -- at least that makes more sence to me than just blindly buying bi-wire cables IMHO.
Bi-wiring speakers doubles the cable going to the speaker - if the speakers are biwireable then each set of drivers gets a cable thus being driven individually from the amp with the same power going to each speaker - channel a and b do not go to the same speaker - L (a) channel goes to the left and R(b) channel goes to the right speaker. Some amps make it hard to run that amount of cable from its speaker out posts. If it is easy then there may be improved sound that comes from the speaker - this is always a source of great debate. Some confuse biwire with biamping which is a totally different story.
Marakanetz: I've read your post three times and I think you had things backwards or confused.

If you were running the speakers with the jumpers on you were not bi-wiring. (even if you were using Bi-Wire cables). The use of the jumpers negates any benefits, and makes your speakers the same as non-biwire speakers.

Now you are running separate single wires without using the jumpers in the binding posts. This is exactly what bi-wiring is.

If this is correct, then you may unknowingly believe bi-wiring helps.

Bi-Wire speaker cables are just combined in a single package as opposed to running separate cables to the speakers. This is called single bi-wire cables. Double Bi-wire is running separate cables for the top and bottom. Some companies make special bi-wire cables that are double the single cable in one jacket (MIT, Analysis Plus Bi-Oval, Nordost and others); These cables cost more that the single version, because there is more cable. Many use different size conductors for the top and bottom very much like you mention using using different single cables.

Other companies separate the mulitple conductors in their regular single cable version into four conductors at the speaker end (AudioQuest, Straightwire, Blue Circle, many others). These cables only cost a little more than the single version (more spade or banana terminations needed). One system of mine has double Audioquest even though a single cable can be made into a biwire. This is more costly because you need twice as much cable. For the regular single version audioquest uses the larger gauge cables for the bottom and the smaller gauge for the top.

RKolluri: If the speakers are designed for bi-wiring it is usually better to do so. (B&Ws for one)

If you try to bi-wire, either connect all the wires to the A or B (not both) on your Onkyo receiver. The A/B on your receiver is meant for running separate pairs of speakers. I am not sure the load will be right going to the same speaker from A and B.

Some amplifiers have 4 binding post made for bi-wiring purposes, which are all on the same circuit.

Whether you buy bi-wire speaker cables or use 2 pairs of single cable is up to you. The results will be different, but one way is not necessarily better than the other. Depends on many factors, including the quality of the cables and your system.

If you already have a pair of good single cables, you could just buy another pair to bi-wire. This may not work if you have bananas (you could re-terminate them). You can put spades/pins or bare wire in the same binding post in your receiver.

Sugarbrie, read Marakanetz's article again. He's talking about a comparison of single-wiring with the jumpers against bi-wiring without the jumpers. His final configuration seems to be a single cable threaded through both pairs of binding posts, thus replacing the jumper with the cable itself.

If it is more practical to hook one cable up to the Speaker-A outputs and one cable up to the speaker-B outputs, there's no reason not to. When the speaker A and speaker B outputs are both switched on, they are tied together at the same point inside the amp.
Orthonormal: Yes I guess you could be right. But if so, then it seems he may have been more interested in comparing various jumper configurations with various jumpers ("trivial biwire") and never took bi-wiring seriously.

RKolluri: I still do not think you should connect one speaker to both the A & B terminals on the receiver. I have my Onkyo HT receiver manual here and it sais specifically NOT to do it; including a diagram of one speaker connected to both terminals with a big X through it. I am not a electrician, but depending if something is wired in series or in parallel, will double the current and voltage. I guess you could blow your speakers depending on the way the A & B are wired. If A & B were the same circuit, Orthonormal is right, it would not matter. Since they specifically tell you not to do it, probably means otherwise.

I want to B-wire it on the speakers side. So if I understand these posts.

The first cable will run from recvr Speaker(A) Left to the Left Speaker (which will be B-wired)

The second cable will run from recvr Speaker(B) Right to the Right Speaker (which will be B-wired).

A-Left-Recvr ----< Left Speaker
B-Right-Recvr ----< Right Speaker

Am I right???
No - if your receiver has two sets of posts for two sets of speakers like speaker A and Speaker B with two controls in the front labeled as such then you would hook them up :(A - left) to Speaker left one set of post--then (A - right) to speaker right same post on that speaker as (A - left). Then (B - left) to Speaker left on the post not used - Then (B - right) to Speaker right on the not used post. To run the system you must have the Speaker A and B buttons pressed in on the front of the receiver. Make sure the jumpers from the speakers are removed.

Yes -- If you are saying A and B for your two separate channels for one set of speaker outs meaning left speaker and right speaker then A - Left receiver to Left speaker and then B -- Right receiver to Right speaker only you have to do two runs to each speaker from the same channel.
Make sure the jumpers from each speaker are removed.
You connect them to the receiver the same as you would single cable. Left A to left, Right A to right.
Thanks evryone!

Ljgj: I think I fall into the second option that you had mentioned. I have only one set of speaker outs from each channel. I had the jumper on till yesterday (defeats the whole purpose of bi-wiring) but I am learning...