Bi-wiring

[Titanium Dome]

Okay, here is one of JBL's more comprehensive statements on bi-wiring. I'm only focusing on bi-wiring, so the bi-amplification portion is not included. Bi-amping is far more complex and not easily attainable (or practical) for most members here, and I'm including myself.

So, if you want to discuss bi-amping, start another thread please.

From the L7 owner's supplement:

[Titanium Dome]

More from the supplement:

[Titanium Dome]

And more from the supplement:

[Titanium Dome]

So there are four possibilities for bi-wiring according to this information:

One amp (single amp) bi-wire
Two amp bi-wire
Three amp bi-wire
Four amp bi-wire

Thus, JBL presents bi-wiring as a very flexible and progressive activity, suggesting that even the owner of a single amp can make appreciable gains by running two wires per speaker from the single speaker terminals on an amp to the separated terminals on the speaker.

JBL's comments on the effects of HF/LF separation resulting from the running of two wires even from a single source reflect this representation from John Risch's site:

http://www.geocities.com/jonrisch/page7.htm

We always need to bear in mind that the L7 network is not a simple or typical one, and that JBL's comments, while general on the benefits of bi-wiring, in this context are specific to the L7's network and its particular adaptations for this usage.

[Titanium Dome]

For your reference, the L7 network.

[Titanium Dome]

Here is a physical view of the networks.

Top: HF
Middle: LF (side view)
Bottom: LF (top view)

[Titanium Dome]

I've seen lots of flaming discussion on the 'Net, and none are worse than bi-wiring. The acrimony with which naysayers attack those who endorse it is epic. Some of the more nasty, insulting, and immature arguing I've ever read is between those who oppose the idea.

I don't know why this is such a big deal to some, but it is.

IME, sometimes it works well and sometimes it doesn't. It seems to work remarkably well with my L7s and S2600s. It seems to be built in to a stacked PT800/PS1400 Performance Series topology. OTOH, it makes little difference on an XPL200, certainly not of the magnitude of improvement one gets with JBL's optional external crossovers.

So, have you bi-wired anything successfully or unsuccessfully? Do you think it was the wire, the amp(s), and/or the internal crossovers that made it work or not work?

[Fred Sanford]

There are parts of this that make no sense to me as they're illustrated in these scans- if there's no active x-over dividing frequencies before the power amps, how would dual-wiring or even dual-amps reduce the intermodulation issues they refer to here?

"By using separate conductors for high and low frequencies (drawing L-C), unwanted treble modulation is avoided. Bass flows through one, treble through another."

Each cable/conductor would be carrying identical information (one-amp), or each amplifier would be amplifying the entire frequency range (all other scenarios). This one paragraph makes me question the validity of the entire article, but I'll consider the source and figure I'm reading it wrong...

je

[Zilch]

The HF goes through a separate set of wires, and is not subject to the varying voltage drop across the wire resistance (and other allegedly audible effects) in those driving the higher-current LF.

The frequencies are split by the separate passive crossovers (HF vs. LF) "drawing" the signal selectively through the two sets of wires....

[MJC]

It seems to be built in to a stacked PT800/PS1400 Performance Series topology.
So, have you bi-wired anything successfully or unsuccessfully? Do you think it was the wire, the amp(s), and/or the internal crossovers that made it work or not work?

I don't know if sub woofers really count when you talk about bi-wire, being subs have their own amp anyway. Either with a plate amp, as the PS1400, or as I have the SUB1500s powered by a Crown K2, but the signal is coming from the sub out on the receiver, not the speaker outs.

But if the subs and mains are stacked, as can be done in the PS and as I have with the PS/SUB1500, it is kind of like being bi-wire, I guess.
I kinda think of my stacks as full range as all frequenies radiate from the same point, though.
Too bad JBL didn't setup the PT800s like the L7 or L880/890, where the PT800 could be bi-wired.

[speakerdave]

How nice. Thank you, T-dome.

[Titanium Dome]

I don't know if sub woofers really count when you talk about bi-wire, being subs have their own amp anyway. Either with a plate amp, as the PS1400, or as I have the SUB1500s powered by a Crown K2, but the signal is coming from the sub out on the receiver, not the speaker outs.

But if the subs and mains are stacked, as can be done in the PS and as I have with the PS/SUB1500, it is kind of like being bi-wire, I guess.
I kinda think of my stacks as full range as all frequenies radiate from the same point, though.
Too bad JBL didn't setup the PT800s like the L7 or L880/890, where the PT800 could be bi-wired.

When the PS is stacked, I don't consider the LE14H-3 as a sub, rather a woofer. The crossover is up to 130 Hz, rather than the 80 Hz (THX Standard) or 100 Hz I might want for a sub. However, the feed is a single wire, not a bi-wire, so... :dont-know

[just4kinks]

From the other thread...

If the nominal impedence of a speaker system is 8 ohms and you then separate the woofer from the tweeter/mid, by bi-wiring, do you still have an 8 ohm impedence, or would it be more like 4 ohm?
Two 8 ohm loads, in parallel, become 4 ohms to an amp.

Don't forget that neither component is a perfect resistor with flat 8 ohm resistance across the entire frequency range. With the crossovers in place, the woofer has very high impedance at tweeter frequencies, and vice-versa. It will vary from system to system, but the overall impedance will be roughly 8 ohms through most of the frequency range.

[Fred Sanford]

The HF goes through a separate set of wires, and is not subject to the varying voltage drop across the wire resistance (and other allegedly audible effects) in those driving the higher-current LF.

The frequencies are split by the separate passive crossovers (HF vs. LF) "drawing" the signal selectively through the two sets of wires....

That's the part I'm just not "picturing", and I'll assume it's either a gap in my learning or a matter of me misunderstanding semantics. Passive crossovers, at the speaker side of the cable, "drawing" only select frequencies through the amp-to-cabinet cable...I'm just not getting it. I'd see that the reaction of the loads would differ between x-over/LF and x-over/HF in multi-amp scenarios, maybe it's the single amp having the wires common at the output posts that makes it a tough sell for me...but, maybe, with more time trying to picture it, it's looking like there's a difference. Hmmmm...I'll be quiet and watch the proceedings for a while.

je :dont-know

[JBL 4645]

[sarcasm]
Science be damned, use yer ears, man! THATS the tool!
[/sarcasm]

What’s a matter Heather, you seem to disapprove. I think that’s a good start please continue Dome, just make it a little more exciting.