|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
207.167.13.69
In Reply to: RE: Interesting way to wire speakers…??? posted by stevethe4th on May 12, 2015 at 16:39:59
...story, don't it? ;)Cheers,
Presto
Edits: 05/13/15Follow Ups:
The speaker wire has zero resistance, isn't the electrical schematic of the first two diagrams identical?
Well...
If you reduce everything to nodes...
Thing is, the resistance really isn't the most interesting feature, even though theoretically there is basically half of it. Half of zero... right. Still half. What's neat is the ability to choose where the current divides up. What many people overlook is that the current flowing in the high-pass filter's "feeder" conductors is different than the current flowing in the low-pass filters "feeder" conductors, by virtue of the different transfer functions (impedance against frequency) of each filter/driver combination.
If the total current produced by the amp is I(total) then you can write:
I(total) = I(hp) + I(lp)
In the single wire case, the currents divide up after the jumper, which is at the binding posts of the speaker. In the bi-wire case, the currents also divide up after the jumper, except now the jumper is effectively at the amp.
Here's an idea. You can use a cable that is great for bass because it has very low resistance and lots of copper and it's great for maintaining damping factor, and you can also use a cable that is not as good for bass, but perhaps excels at high frequencies - such as fine wires or ribbon cables. The ability to bi-wire allows the user to use different cables for the high and low sections, "optimizing" each one, and resulting in far more iterative possibilities. What audiophile could resist?
Now try passive bi-amping with identical amps and identical cables. The current flowing in each AMP is now dedicated.
Now try passive bi-amping using different (gain matched) amps but one that has incredible bass power and the other one has a more refined high end, despite being somewhat too polite...
Now imagine two CD players and two DACs and two pre-amps. You press play on both DACs simultaneously. You could "bifurcate" your entire signal chain, even the source material...
I find it interesting that bi-wiring is not as often ridiculed as passive bi-amping. If anything, passive bi-amping is less of an insult to "all too common common sense" because by virtue of having two amps you now NEED two cables.
Then again, those who protest bi-wiring tend to ignore than when the current to each respective filter/driver combo divides up at the amp, so do the magnetic fields that exist along the length of the cable. You're not just separating the currents, you're putting the magnetic fields for each respective filter/driver combo in different places in physical space.
Hmmm.
Cheers,
Presto
As it turns out, passive biamp, which I DO UTILIZE will not really net you any power.
By the time you add a line-level crossover and delete the speakers crossover, you can net as much as 3db 'extra' power.
In my execution, I have VERY short speaker cables and 1 stereo amp per speaker.
If I ever get around to figuring out a line level crossover, I'll be good to go.
Too much is never enough
In theory, it's correct - you don't get more power per se... You're using voltage source amplifiers, so instead of one amp seeing the impedance of two networks in parallel, you have two amps each seeing one of two impedances. The amp powering the LPF will see high impedance at high frequencies and the amp powering the HPF will see high impedance at low frequencies. The amp powering both sees nominal impedances at *all* frequencies by virtue of a LPF and HPF in parallel. Low frequency current flows into the LPF and high frequency into the high pass filter.
So, those who say "passive bi-amp with traditional parallel crossovers *does nothing*" are really not being entirely truthful. You *are* doing something... you're using one amp for low-pass current and the other for high-pass current. Who's to say removing current pulses associated with bass reproduction from the amp driving the high pass filter can't offer benefits?
Another thing you could do is specialize the amps so long as one or both amps have adjustable gain. Once the amps are gain matched, you could use an amp with a massive power supply that you think excels for bass/mid reproduction and another for high-end that you think excels at mid/high reproduction. Do you want the same amp "sound" for the mid of both low and highpass filter in a 2-way? Some might argue "yes", but others might think of it as more possibilities for mucking with the final tonal balance of the system. Now you need to find two amps that do their respective frequency ranges well, including midband for both, and also work nicely together in the midband.
You could even make a hybrid tube and transistor tone.
Anywhere there is crossover overlap and you have two different amps... wow, I've never even thought of that before, even though in PA situations I've done that very thing (for DJs and performing arts folks who were on very tight budgets and said 'here are the amps'...) . But in PA applications I never sat around and pondered the concept of tonal balance effects by using two different amps for drivers which share a common crossover point.
Do you realize the endless amount of thinking, fretting and experimenting an audiophile could do with this?
I'll be in my lab...
Cheers,
Presto
couple 'a thoughts:
The amount of power per 'way' depends entirely on the crossover frequency. I'm told and will just accept the idea that the 50:50 power point is somewhere in the 300hz -> 400hz region.
An amp will 'amplify' whatever it's fed. So, fullrange siganl to each of 2 amps which THAN are into a crossover, lowpass and high pass for a 2-way speaker will NOT reap the full benefits of biamp.
Once you limit out of band needs, you'll gain as much as 3db power.
Going to 'pairs' of amps helps with all those timbre / tone matching problems and even the gain matching problems associated with tube/ss mish-mashes.
My panels cross at 600hz which is close to the 50:50 power point. Given that I cut the lowest bass to the panels, that reduces the need for power in the low end AND moves the 50:50 point higher in frequency.
And yes, for the obsessive / compulsive tinkerer, biamping is tailor made to provide a LIFETIME of nuttiness. You could go in small circles for decades without conclusion.
Too much is never enough
That's right - passive bi-amping will not reap the *full* benefits like active bi-amping or PLLXO will. Anytime passive crossovers are used, there are additional losses to take into consideration.I'm just saying that it's untrue that a passive bi-amp "does nothing" as some claim. It certainly does do something - it reduces the demands placed on each individual amplifier. In electrical terms, you're basically halving the source impedance w.r.t. the speaker crossover and driver impedances. The biggest benefit, in my mind, is not having that heavy bass current dragging down the tweeter amp's supply rails. Plus, the bass amp is also seeing less current - probably not 50% since most crossover points are between 1.8k - 2.5K. But still, an improvement nonetheless.
As far as current goes, though, you're not going to draw more current with two amps than you will with one, save for doubling the amplifier losses, which would be a small percentage of power dissipated. You're not dissipating more power over all (as you point out), but each amp individually is dissipating less power, for a given SPL.
But absolutely, it's not anywhere near the increase in efficiency from going with active crossovers. And when you've gone active, you don't necessarily need identical amps for gain matching, and your amps don't even need to have attenuators - you can twist a knob at the pre-amp level and gain match there. In fact, according to the math passive bi-amping is LESS efficient because you have twice the cost of amps, twice the weight, twice the idle current and amplifier losses, and all this for no gain in power.
You do have a known-good working hot-standby if you lose an amp though! :)
Thing is, if an audiophile gets a second $1500 amp and he perceives an improvement, is the second amp worth that particular improvement? That's based on what (if anything) he hears versus how much $1500 means to him.
Make that second amp $15,000 and it might be a different argument - but not against doing it. Someone who can afford a single $15K amp in the first place might think spending another $15K for an audible difference is well worth it.
Cheers,
Presto
Edits: 05/14/15 05/14/15 05/14/15
I'm not sure you're 100% on this.
Please read the article from ESP = Elliot Sound Products
The article has pictures of scope traces which help explain WHY passive biamping doesn't reap power benefits…..
There is ALSO a 'Part II' which explains further.
Too much is never enough
No, I totally get it.The article compares passive single amp to active multi-amp, and does a fine job I have to say. (Nice explanation of how gain demands are reduced for individual amps in active configurations.)
But I was discussing differences between passive single amp and passive multi-amp. In the active/passive multi-amp comparison, active can get more watts per dollar/pound of amp compared to the passive equivalent.
In pro-sound environments, this is a no brainer since you want the most SPL for given dollar, weight and cargo space that gear takes up. In audiophile land these concerns may be a non-issue.
Case in point: Passive Tri-amp Versus passive tri-amp:
Passive 200W/channel amp x 3. Max potential output = 200W. (no gain in Max SPL).
Active 200W/channel amp x 3. Max potential output = 600W. Max used. 450W?** New max determined by reaching max output of any on driver or max output voltage of any one amp (clipping).
So, you have three choices how to use the increased efficiency of active:
(a) don't. You like passive multi-amp for other reasons than "more power".
(b) get smaller amps (less overall gain needed) for the same SPL as passive equivalent.
(c) use the same size amps and get more SPL than the passive equivalent - if speakers can do it.Nobody said active was not more efficient than active. I just said that max efficiency and max SPL per dollar are not necessarily design considerations for an audiophile. If a guy thinks (2) 200W amps sound better than (1) 200W amp and gets no additional efficiency or output capability (and doesn't care) then who's to bash his ideology if better sound was the *only* criterion for the upgrade?
The crux of my posts was that passive bi-amp is different from passive single-amp. Despite reproducing the full range voltage signal, they no longer reproduce the full-range signal current. Each amp only sees the current drawn by the respective low and high pass filter/driver combinations.
I did not say passive multi-amp offers the same benefits that active multi-amp does.
Passive multi-amp offers no voltage gain reduction, therefore does not make use of the increase in total available power.
Cheers,
Presto
Edits: 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15 05/15/15
The REFERENCE and starting point is a single channel of amplification and passive speaker level crossover per channel. A very large %age of stereo guys start and STOP right there.
Phase 2 is passive biamp using the speakers internal crossover
Phase 3 is either active or passive Line Level crossove which is where potential benefits REALLY pile up.
I think the 'efficiency' gain of a LL crossover comes from the out of band signals your amps are no longer asked to amplify. This, according to the ESP article, can amount to a maximum of about 3db. Roughly 2x the amp power, compared to the 'passive' biamped system. Given my panels low /mid 80s sensitivity, I'll take every watt I can get.
The drawings in the ESP article which show a HF and LF O-Scope 'trace' clearly indicate that the amp will Voltage Clip at about the same point as a single amp of the same power. I'll go with ESP on this.
I don't think we disagree about going to a Line Level crossover. That is my ultimate goal and the reason I went to a pair of stereo amps for my panels. And since my runs are short, I'm not overly worried about the PLLXO's inability to drive long runs of cable and its internal losses. Since each amp will have its own crossover, it will be locaed right AT the amp. From the crossover TO the amp may require 12" jumpers, certainly nothing longer. I can Duplicate, pretty closely, the crossover which came with the panels. Most of the Active crossovers I've see are high order and not generally to my liking. I'm not equipped to do a major crossover reengineering project for my panels. Most reports I've read say that 24db/octave filters don't necessarily sound 'right', anyway. I'd consider an active LL crossover using opamps, IF I could find a 6db / 12db octave schematic to evaluate.
Too much is never enough
I've been running DSP/ACtive for years now and I haven't looked back. Every time I try a different DSP crossover or an outboard active one, I start missing my DSP/Active (Thuneau) setup right away.
Maybe I'm just used to it... I don't know...
But all that rumination has me seriously wanting to play around with some passive bi-amping, for no other reason that I have bi-ampable two-ways here and a few amps kicking around...
I've never done a full-out PLLXO setup and I really want to try one... the upshot is the parts are small and not super expensive.
To the lab! :P
Cheers,
Presto
I think you've hit on one very good feature of a PLLXO setup.
You can basically build such a crossover into an ALTOIDS can and spend about 15$ EACH even buying the MOST EXPENSIVE components available. OK, add a few bucks for overpriced RCA jacks.
Too much is never enough
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: