Bi-wiring KLF-20's

[Lankhoss]

I still don't quite fully understand bi-wiring, so my question is about two different types of hookups, and what the advantages would be of each one. I originally just bought bi-wiring cable, and ran it out of one output. It has 4 terminals at the speaker end, one set for the low end, and another for the high. After thinking about it, and also talking with a friend of mine....I figured it might be more beneficial to hook up separate pairs of speaker wires from two different outputs of the receiver (using the "B" speaker outputs, and setting that output for front bi-wiring through the receiver). Originally, I thought that separating the terminals on the speakers would create two separate 16 ohm loads, as opposed to one 8 ohm load when both reds and blacks were shorted together.........thus, putting less stress on my amp. Obviously, it is far more complicated than that. Right now I have them setup the second way I listed, with two separate pairs of speaker wires. Although the one set of bi-wires actually has the low pair and high pair wrapped differently to pass the dedicated frequencies better, I still thought that running two separate outputs to the same tower would still be better than using one. It seems as though it sounded better with the one set of bi-wires though. Can someone explain to me the differences and benefits of each hookup, and in a way that I can understand it?

Thanks!

[lynnm]

Yeesh !!

Forgive me but as a technician I shudder at what you have done to yourself....You have taken every possible complication available - mixed them altogether - and not being especially experienced with the speakers in question - now find yourself wondering as to the best setup.

I admit that I am a wayward Luddite

IOW - I think the fundamentals should never be ignored but admit the possibility that improvements (while likely heretical) are possible.

My suggestion is that you revert to a totally 2 channel setup and then introduce the possible variations you have available a step at a time.

Do yourself the courtesy of not assuming that the advertising hype Re: multichannel uber alles is necessarily true ! T'aint Necessarilly So !

When you find the best setup - Then you have the best setup for you - Until the next time the bug bites !

[WMcD]

I, myself, believe that biwiring is worthless. But lets see what you're talking about.

I think you explain the wire and speaker end well. There are two jumpers (brass pieces) at the speaker, right? You did remove that?

You're issue is what is going on at the amp end. I'll also assume this an amp with an A and B speaker connection ("remote") rather than surround.

The typical amp just has a left and right amplifier. Then there is a switch to choose A or B, or A and B. That last one just puts the A and B output terminals in parallel, just like connecting a pair of wire to just A.

You might be able to confirm that for us. On A do you just hear the woofer and B just the tweeter? and both (full sound) on A plus B?

I don't believe any of this wire is better at highs and lows.

As you can appreciate from the above (if I've got it right) there is no difference in the load on the amp. You're just chaging the point of connection. With normal single pair wiring the split to bass and treble is at the speaker. With use of two wire pair to the A, the split is there. With the use of A and B, it is at the switch inside the amp.

But be happy, experiment. Watch that you got the wiring correct so to not short out the amp.

Gil

[Lankhoss]

Thanks for the replies, guys. Just to answer your question, I did remove the brass plates at the speaker terminals.

Gil,

Sorry if I didn't explain this too well. I have a Pioneer VSX-43TX receiver. It has 5 outputs on the A side, for the regular 5.1 setup. The receiver is also capable of THX 7.1. So the B side has a L and R out for the "surround back" speakers for that, if you want. I am also a technician, but I am not an audio technician. In fact, I had the most difficult time with transistors and amplifiers in school ;-) Anyway, I am trying to figure out if there's any benefit to hooking this up one way or the other.

I can get one set of bi-wire speaker cables. This has TWO terminals at the receiver end (black and red), then has FOUR terminals at the speaker end (red and black high; red and black low). I can use just one output of the receiver, and plug the bi-wire into both of the inputs of the speakers. Or, I can use two separate sets of regular speaker wires for the hook up. There are a few options I can choose from in the receiver settings for the B output. I can use it for the "surround back" speakers for the THX 7.1 field, or I can choose "Front bi-wire" where it sets the L and R out of the B side to send the same signal as the L and R out of the A side. So I have the L and R out of the A side hooked to the high in of both the left and right speakers, and the L and R out of the B side hooked up (through a totally separate set of speaker wires) to the low in of both the speakers.

I am trying to apply what I know about electronics to this situation, and it is just baffling me! I believe that receivers either have separate amps, or at least separate amplified channels for each output. I would assume that using two separate outputs would be easier on the amplifier in my receiver, as opposed to using one output that just has the wires split to go into two connections at the speaker end. So I was just wondering if someone could sum this up for me, and let me know if there's ANY difference in the two connections, and what a benefit would be from each one. If I am not getting a benefit from using the two separate pairs of speaker wires then I'd rather go back to using the bi-wire cable (less wire, and less hassle!).

Thanks again!

[dbflash]

Try WWW.DAVIDMANNAUDIO.COM

Go to FAQ.

You will find a very good picture of how to hook up your speakers to biwire.

Is it worth it, only you will be able to tell.

I do have a pair of KLF20's biwired. They have been biwired for so long I don't remember how they sounded before I did this "upgrade".

Danny

[Lankhoss]

Thanks again for the reply, that page has a lot of good info. I know how to hook up the bi-wiring, however. I only have my receiver, no other preamps or external amplifiers. So I am wondering if hooking up one bi-wire to one output of my receiver is any different than if I were to hook up two separate sets of speaker wires out of two different outputs of my receiver. I can't seem to find anything that gives me details. The outputs are both regular outputs (not a low pass and high pass), I just hook one up to the low (woofer) inputs of both speakers, and the other output to the high inputs of both speakers.

I am wanting to know, basically, what the differences are in how my amplifier (my receiver) work with the two different configurations.

[WMcD]

This is something different than what I wrote about.

I can't view that as I type. However, I made an assumption your reveiver was something less sophisticated than you have. I hope that assumption came through. However it is not the case.

From what you descibe, your HT receiver has at least four independent output amplifiers. There are front left and right and surround left and right. (You probably have a fifth for "center". That is not in the picture here.)

It is possible, from what I understand, to feed front left and front right signal to surround left and right amplifier inputs and therefore the outputs. This would be two channel stereo sound with L and R appearing, in each case, at two amplifier outputs. So you can have La, Lb, Ra, and Rb. You have to look at that nomenclature I've come up with. (a and b being the identical signal) These amps are putting out full bandwidth.

If you're in surround mode the outputs would be Lf, Ls, Rf, and Rs (here the signals are different, with f meaning front and s meaning surround).

So, you have the capabilty of using a pair of amplifiers on each stereo channel. With biwiring, you can use them to feed the treble and bass inputs of the speaker box.

This is getting difficult to describe things without diagrams. Too bad I don't have a scanner to sketch things out and upload, and link the file to display it.

- - - - - - - -

It seems to me that there is a concern in your question about the amplifier working too hard, or the benefits of taking it easy on them.

Further, you may have a reasonable but inaccurate conception of the way the two inputs to the speaker box add in impedance. You're thinking this is overall an 8 ohm system, the bass and treble are in parallel with the brass jumper, and therefore, the individual sections must be presenting 16 ohm loads. And this might well, with the use of the two amps per channel, allow less current to flow.

However, that is not the way things work in this case. The joker in the pack is the crossover filter in the box. I'm going to present this in a simple way and not get into the variations in impedance in real drivers.

You know that the cross over filter "sends" the proper frequencies to treble and bass units. Lets assume the cross over frequency is 800 Hz. Above 800 Hz gets sent to the treble horn and the frequecies below 800 get sent to the woofer. That is correct of course.

Lets look at the two inputs at the back of the box (now not bridged). The effect of the filters is that the treble input presents an 8 ohm load above 800 Hz and "infinite" (or a very high number) ohms below 800 Hz. Similarly, the bass input presents an 8 ohm load below 800 Hz and infinite above 800 Hz.

You have to consider the immediate above for a moment. It means that the filter network is "sending" the frequencies though to the correct driver. However, it also tells us something about HOW it is doing it. Outside of the working range, the filter is presenting to the amp, an infinite impedance, or "an open circuit". Amperes = Volts (from amplifier) / Ohms. When ohms are a big number, there is no current (amps). No amps, no power.

Now we can see what happens if we put in a signal to the amp feeding the speaker, assuming one amp and the bridge at the back of the box. Sweep the frequency up. Up to 800 Hz, there is an 8 ohm load presented by the woofer, above that, there is an 8 ohm load presented by the tweeter.

I'll belabor the point. When the woofer is turned off above 800 Hz by the filter, the input terminal for that one acts like it not there. When the tweeter is turned off below 800 Hz by the filter, the input terminal acts like it is not there. The combined effect, though, is one 8 ohm load.

- - - - -

So, ya say, this is all well and good. But with the bi wiring and the use of two amps we have a special situation. One amp "sees" 8 ohms below 800 Hz and infinite ohms above. The other "sees" 8 ohms above 800 Hz and infinite ohms below. One is chugging out the bass notes and the other is handling the highs. Does this make them more "happy"?

Probably not, within limits. The little old transistors or tubes only know current and voltage as they are caused to flow because of the waveform of the music.

When a bass note and treble note combine, there is a higher level in the summed waves. We can imagine a situation where the amp(s) are being driven very hard, near clipping. If the two frequencies are fed to two different amps, then maybe we avoid clipping.

However, that situation is very "special". It assumes that the bad boys are split across the range where one amp and the other are functioning. There are some considerations in your set up which I'm not quite sure of, if we're going to this "near clipping". The two amps are both being fed the entire range, yet the load is not sucking out amps over the entire range. In classic "bi amping" there is a filter ahead of the amps.

- - - - -

Overall, I don't see any big advantage to the use of the rear amps as helpers unless you're driving them to the limits of their performance. That is dangerous in any situation.

Gil

[Lankhoss]

Gil,

Thankyou so much for the informative post!!! You summed an EXTREMELY difficult situation up about as well as one could. I was actually thrown for a loop when I tried to manually measure the impedance across each input with a volt meter, and found the high input on both speakers to be infinite (like an open). The way you described it explains that situation. I greatly appreciate the time you took to write out the lengthy reply, and it hit right at home with me. This is the first time someone has really explained to me how a bi-wireable speaker works, and not just HOW TO HOOK IT UP. Thanks again Gil, that was a lot of good information!!

[JohnA]

As is normal Gil presents a well thought out reply to what's become a complex question.

The "correct" way to biwire your speakers is to use the special cables you bought with 4 terminals on the speaker end and those cables alone. It will not stress your receiver more than a single pair of wires.

Trying to use the mains channel and some of the surround channels to drive a single pair of speakers will result in, at best, what is known as fool's biamping (2 amps/speaker without an electronic crossover before them). Depending on how your receiver is made, it may do damage. Without detailed information, we cannot be sure what is going on inside to know what might happen. I cannot see anything good coming from using the mains and surround amps on one speaker. I would not do such a thing.

In the stereo days, receivers/amps had A/B switches. Like Gil explained, Speaker A and Speaker B were connected to the same internal amp and the extra terminals on the back were purely for convenience. Initially, we all must have thought this is what you had. Using 2 wires from both terminals on this kind of amp would do no harm and would be as convenient and cheap as biwiring would get.

[Lankhoss]

John,

Thanks for the info!! I actually thought I had a slightly better sound with the bi-wires than the way I have it hooked up now. I am more interested in the stress on my amp and/or speakers than the sound, considering the difference is nominal. I will definitely go back to the bi-wires. Thanks again for all the help!

[WMcD]

The behavior of the ohm meter makes sense if you can visualize the structure of the crossovers.

Lets use a simple "first order" 6 dB per octave set up. You probably have something more complex in your box, but this is a good starting point.

Looking into the woofer connection we have an inductor wired in series with the woofer.

(+)--inductor--woofer--(-).

At some frequency, the inductor starts acting like an open circuit (800 Hz and above). Impedance = j 2 pi freq L. As you might have seen. Look at the freq term. When freq gets big, the impedance number gets big, and acts like an open circuit.

The inductor is a spool of wire and has some d.c. resistance. Probably less than 1 ohm. So, when you put the ohm meter (which measures the V/I relation at zero hertz, or d.c.) you are measuring the combined series resistance of the inductor and the voice coil.

Looking into the tweeter connection we have a capacitor wired in series with the tweeter driver.

(+)--capacitor--tweeter--(-).

At some frequency, the capacitor starts acting like a closed circuit (800 Hz and above).

Impedance = 1/ (j 2 pi freq C). As you might have seen. Look at the freq term here in the denominator. As freq gets big, the impedance number goes down, tending toword 1 and below.

The capacitor is actually two plates separated by a non conductor (oiled paper or a plastic like polyethelene). Therefore it can not conduct d.c. So your meter indicates an open circuit.

One thing to keep in mind is that your ohm meter only works at d.c. or zero hertz. So you can't use it to measure impedance at anything than d.c.

No sometimes this very handy. Voice coils of either the tweeter or woofer is a coil of wire in a magnetic gap. So the ohm meter will let you detect an open voice coil.

I hope that helps but another page into the overall picture.

Gil

[WMcD]

We've come so far, it seems a shame to not throw in a little bit more based on the above building blocks. I hope no one minds if I'm getting pedantic.

We've see that the cross over network is actually two filters wired to the box input terminal in parallel. One turns off (well almost off) at the crossover point, and the other turns on (well almost on). Of course this "view" assumes where sweeping up or down in frequency in our heads.

The filters are not brick walls by any means. That is shown in the equations which describe the impedance of the cap and inductor which are the critical parts of the two filters. They are a high pass filter for the tweeter and a low pass filter for the woofer.

One important feature is that at the cross over point of 800 Hz, we want the woofer to be half turned off, and the tweeter half turned on. That is a bit of tautology. We want them both at half power. They are both on their way to being more effective depending on the frequency.

If you look at my little typing diagrams above, we see that the cap or inductor is in series with their respective drivers. Now, think about it, how do we get a series circuit to work so that half power goes to the driver, or how do we get it to work at 1/2 power at 800 Hz?

The answer is that we assume the driver is a load of 8 ohms. If we can get the L and C impedance to be 8 ohms, then the power is split between the given driver and the L and/or C.

So we look at the equation for impedance for the cap or inductor. We have to plug in 800 Hz as the freq, 8 ohms as what we want the impedance of L or C to be, and crank the math. Ignore the j, it is square root of -1 and we don't worry about it here.

Let's go back to the typing diagram at the crossover frequency. We see:

(+)--8 ohms of cap impedance--8 ohms of tweeter impedance--(-)

and

(+)--8 ohms of inductor impedance--8 ohms of woofer impedance--(-)

So those are the loads "seen" at the connections at the back of the box, at 800 Hz. It makes a lot of sense. Each driver is getting half power because of the series impedance in its own circuit. In each series circuit the total impedance is 16 ohms. With the jumper in place the 16 ohm circuits are in parallel, and the result is 8 ohms.

It may seem like Voodoo Bookkeeping. None the less, this is how it works. As implied above, and perhaps more times than necessary, when you get away from the crossover frequency, the impedance of the L or C change so that the tweeter and woofer are effectively blocked by the C and L.

So that is story from Chicago. Now I can have a beer.

Gil

[Lankhoss]

Amazing submissions, Gil. Thankyou so much for the abundance of info. That is extremely interesting!