How do I bi-wire and bi-amp?

Power amps are QUAD 405 but with only one speaker output.

Suggestions gratefully received...
CHEAPEST great way is to buy Canare S11 starquad, and use two each of the 4 conductors for each set of connections on the back of the Quad 12 you have. THEN you can muck around with designer cables later if you wish.
If you want to bi-amp, you'll need an active cross-over and an additional amp. (stereo or a pair of mono's.) Subaruguru's response was for bi-wiring.

What speakers do you have?

Bi-wiring is just running separate speaker cables from the single terminal on your amp to the two sets of terminals present on bi-wire compatible speakers. Doesn't have to be special "bi-wire" cable--you can run two sets of normal speaker cables if you want and just stack up the spade connectors on the amp end. (There is usually a jumper plate connecting the two sets of terminals on the speakers that should be removed).

Bi-amping is running the separate terminals (generally representing the "high" drivers and the "low" drivers for the speaker) on the speaker off separate amplifiers.

In the former case, the "split" occurs after the amp and before the speaker. In the latter case, its a line level split after the preamp and before the amps. If you bi-amp, you can do it horizontally (one stereo amp for the low end, one stereo amp for the high end) or vertically (one stereo amp for the Left, one stereo amp for the right). Maybe I have that backwards, but you get the idea.

Jim, for the record, you don't necessarily *need* an active crossover to bi-amp--I'm bi-amping a pair of ML Prodigy speakers without an active crossover b/c, while MLs are set up for bi-amping, ML strongly counsels *against* active x-overs. For Bigthistle's info, there is a metaphysical debate as to whether I'm getting the full benefits of bi-amping. The debate (I'm simplifying) being balancing putting another active component in the signal path (passive bi-amping) versus allowing your amps to function better by having them only responsible for a smaller bandwidth of freqs. to deal with (active bi-amping).

I can attest, however, that I do get some benefits--I can hear them.

If you aren't using an active x-over, you need two sets of line level outs to feed the two sets of amps. Some pre-amps have two sets. For pre-amps that don't, you can get specialty line level Ys that create two. Or, you can get a funny solid metal block (for RCA connections) that turns one female RCA into two. That's what I've done.

Could someone enlighten me a little on this subject? If one is using two amps which run independently to the high frequency drivers (ie. one amp to the highs) and one amp to the low frequency drivers, what happens to all the low frequency signal that is being fed to the high frequency drivers along with the high frequency signal? Maybe I haven't asked this correctly but someone may be able to get what it is I'm trying to ask. It seems that one bigger amplifier that is bi-wireable with speakers that are bi-wireable would be the favored approach.

I have an active crossover arrangement and know that the unwanted information for a driver is eliminated before amplification. This makes all kinds of sense to me and is a huge benefit that only the deaf could not hear. I can understand the benefits of more amplification and can see how another bunch of watts could wake things up. I can also understand doubling the ammount of speaker cable perhaps benefitting. What I'm having a hard time grasping is how more cables, power cords, etc. is better than a single, more powerful amplifier when dealing with conventional crossovers. Inquiring minds want to know.

Patrick--the LF part of the signal going to the "High" input gets filtered out by the internal XO in the speaker. Same with the HF part of the signal going to the "Low" input of the speaker.

In my situation, the internal speaker XO can't be taken out of the path, nor does ML recommend use of an active XO, b/c the internal XO is really part of the ML Force Forward design. I gather there are some phase issues that go haywire with an active XO.

Perhaps I should have just bought "bigger" amps. But, I started with one that I had, and got a real good deal on the second one, so reality enters the picture (i.e., buy another VT100Mk III for $3K, or sell my one VT100MkIII for $3K and dump at least $6K beyond that on a pair of VTM200s). I can't bridge them to mono, and, even if I could have, I gather there may be bad issues with bridging resulting from halving the effective impedence seen by the amp, especially aggravated by complex low impedence loads like ESLs.

My rig sounds better now to my ears. Maybe that is because the loads presented to the two amps are easier to drive, even without bi-amping with an active XO. I have to believe the load presented by a high pass filter and an ESL panel is significantly easier for an amp to deal with than the load presented by a XO networked to an ESL and a conventional driver.

Thanks for the reply to my question. I hope I wasn't misunderstood as being critical, it's just that I couldn't (can't) grasp a benefit beyond a single, larger amp. I can certainly appreciate making the most out of a couple of excellent deals. :) The bi-amping as described seems to be a method of choice for a number of audiophiles. Many things that are discussed in the forums here are beyond my experiences with this being one of them. I have so many questions and life is too short to get all the answers. There are many ways to skin the audio cat.

Edesilva- I'm not at all familiar with your ML's, but am curious about how you cross over before the signal gets to the amps. If passive, are you able to adjust slope and balance? How do you then run speaker wire separately to the LF and HF drivers? From what you seem to be saying, you somehow do a XO before the amps, then run speaker wires to the ML's XO, which sort of sounds like a hybrid bi-amp/bi-wire arrangement. Perhaps you could describe your set-up? I have a pair of Maggies that I'm looking to experiment with bi-amping and would like to consider all options.

Patrick- One of the other advantages of bi-amping is that you can use amps with less power as both amps work more efficiently within their narrower bandwidth. Typically, the amp for HF is around half of the power of the LF amp as LF's suck alot of power. A 200 watt LF amp with a 100 watt HF amp plus the XO may outperform and play louder than one 300 watt amp.


The ML XO is in the speakers. I'm not using an XO prior to the amps... Being a tech dilettante, I assumed that a bi-wire capable speaker meant that the internal speaker XO is a high pass filter and a low pass filter that get split when you remove the jumper from the speaker terminals. That may be oversimplification and confusing. But, there are no filter or XO elements I use outside the speaker--pre goes to amps, each amp goes direct to a speaker terminal on the MLs.
Edesilva- THanks. I'm a little lost, but it's probably because I'm not familiar with the speaker. Sounds like it's a little closer to a bi-wire with with an amp for each wire pair?? I'll find a dealer and take a peek....

Like Edesilva, I also run ML speakers (I wish mine were also Prodigy's, but I am still very happy with the smaller Ascent's) with a passive bi-amplification setup. (Obviously, by default, if you bi-amp you are also bi-wiring.) I chose to use a vertical passive bi-amp, meaning that I use one amp, L & R channels, for the right speaker, and a second amp for the left speaker. My pre-amp has 2 sets of outputs, so I connect both "right" pre-outs to both inputs on the amp for the right speaker, and both "left" pre-outs to both inputs on the left speaker. I then use one channel of the right amp to drive the LF section of the ML's (using the internal XO), and the other channel to drive the panel. Likewise on the left side. Even though both amps are being fed a full range signal, and amplifying the full signal, the channel connected to the LF section "sees" the XO on the other end of the speaker cable, and the impedance is essentially infinite at frequencies above the cutoff frequency, so the current flowing through that cable is only at the lower frequencies. The same effect occurs with the channel driving the panels. The impedance for frequencies below the cutoff freq for the high pass section of the XO is essentially infinite, so the current flowing in the cables only carries the higher frequencies. This is the underlying theoretical benefit of bi-wiring, since it prevents the LF signals in your speaker cables from degrading the HF signals via magnetic interaction.

IMO, one of the biggest advantages of the vertical passive bi-amp is that each speaker gets its own amplifier, similar to using mono bloc's, so even though you are using both channels on each side, you only have the right channels music signal in the right channel amp, and vice versa. Therefor, no inter-channel crosstalk, the power supply for each channel is not stressed my large dynamic peaks on the other channel, etc... Further, I get significantly better sound with this setup than I did using the 2 amps bridged mono w/ bi-wire. This, like Edesilva mentioned, may have something to do with the electrical characteristics of bridging amplifier circuits and the difficult impedance characteristics of an ESL panel, all I know is it sounded very constrained when the volume started moving up. Dynamic constraint is DEFINITELY NOT a problem anymore.

One caveat for the vertical passive bi-amp, you MUST have identical amplifiers for both sides. If you want to use tubes for the highs and SS for the lows, or a more powerful amp for the lows, you have to go with a horizontal bi-amp (which I haven't tried yet, because I like the sound I am getting right now).

I you have 2 identical stereo amps, and 2 sets of speaker cable (these don't have to be identical), I would at least give a vertical passive bi-amp a listen. Again, I don't know which has a greater impact, the bi-amp effect or the bi-wire effect, but the end result sounds really good (to me!).

Mike- Thanks, I am now beginning to understand the basics of the ML arrangement and it seems like it might be a good (and less expensive!) alternative to a "true" bi-amp with the advantage of eliminating a separate XO. A couple of questions, though- Do you find that you need the same watts to the LF as the HF in order to balance the volume between HF and LF? If not, how is balance achieved? Assuming that HF and LF amps are identical, do you find a sonic difference and/or volume difference in going this route vs simply finding a similar amp with twice the power and bi-wiring it to the speakers? (In other words, could one accomplish the same thing by bi-wiring an amp of twice the power?)

As long as the gain of the amps matches, you don't need the same number of "watts" on the high and low side if you horizontally bi-amp... I was actually thinking of switching from from horizontal bi-amping with two ARC VT100s (100WPC tube) to a single ARC VT100 for the ESL (high) part, and an ARC D400 (200WPC SS) for the dynamic driver on the bottom. Since they are both ARC amps, the gain is the same, so the relative volumes for top/bottom won't change.