There would not be any energy consumed, since there is no driver to drive. |
Many crossovers have a simple 1st order Butterworth section(an inductor) in series with the woofer Some let the woofer's natural inductance roll off the mids/highs. If there's more than that(a cap to ground after an inductor, balancing or EQ circuit resistors/caps/coils, etc), you will experience some loss/signal degradation. What's the low freq circuit of the x-over look like? A X-over that's designed for bi-amping/bi-wiring separates the entire hi/low-end section, via removing it's jumpers. If you can trace the low freq circuit of your x-over, and clip the positive circuit at the input terminal, you'll not have any further concerns. |
I agree with Rodman. It depends on the crossover configuration. If it is more than a first order crossover (i.e., an inductor in series with the woofer), you would want to open the INPUT to the low frequency part of the crossover network, not its output which is connected to the woofer.
Regards,
-- Al |
Contrary to audiophile wisdom, crossover networks "soak up" almost no power, even when all the drivers are connected. If they did they would get hot, and if mounted in a sealed enclosure stuffed with fiberglass or wool, very hot.
Disconnecting the load on the low pass leg may affect characteristics of the high pass leg. |
Contrary to audiophile wisdom, crossover networks "soak up" almost no power, even when all the drivers are connected. If they did they would get hot, and if mounted in a sealed enclosure stuffed with fiberglass or wool, very hot.
Yes, inductors and capacitors do not dissipate significant power. However I would think that there would be some sonic benefit with many amplifiers to disconnecting the woofer's crossover elements, because the reactive (inductive and capacitive) load seen by the amplifier would be minimized. Disconnecting the load on the low pass leg may affect characteristics of the high pass leg. I believe that is only true for the relatively small number of speakers which are designed with the crossover legs in series. In those cases, a low pass filter is connected across the high frequency driver, a high pass filter is connected across the low frequency driver, and the two filters (and consequently the two drivers) are connected in series. The unwanted frequencies for each driver are shunted (bypassed) around the driver. But that kind of design is uncommon, I believe. More typically, the multiple crossover legs are in parallel and do not interact. Koestner -- If you were thinking of leaving the low pass crossover elements unused, I'm not sure how you are planning to make the rolloff of the signal applied to the woofer complementary to the rolloff of the high pass part of the crossover. I think you would have to use an electronic crossover ahead of the low frequency amplifier, set to provide a low pass function for the woofer with rolloff carefully matched to what those crossover elements originally provided. Regards, -- Al |
Contrary to audiophile wisdom, crossover networks "soak up" almost no power, even when all the drivers are connected. If they did they would get hot, and if mounted in a sealed enclosure stuffed with fiberglass or wool, very hot. Agreed. They don't soak up much power. However they do act as a bottleneck or choke and any voltage drop across the crossover means less amplifier power reaches the speaker drivers. |
Perhaps you've never seen an EQing X-over, such as that in the Rogers, Harbeth, Chartwell, Spendor or KEF LS3/5A, LS5/9 and other BBC approved monitors, the Harbeth HL-P3(with it's 21 element crossover) and so on. There are a number of trim resistors, shunt coils(some that act as autotransformers), and caps that are in the notching/shelving circuits and go to ground from the positive input(the main reason they are so stinking inefficient). If these are not removed from the LF signal path, they WILL dissipate energy as designed, but even more as the woofer will not be in the circuit as a load. That's why I asked what his crossover looked like. There are too many variables to make a blanket(uneducated) statement. ie: What would occur in this system, if the woofer were simply removed: (http://www.syer.net/images/DAHLQUIST_DQ10Schems.jpg) YES- The best/most accurate way to bi-amp is via an active x-over, before the power amps. The second best, is to separate the HF/LF sections of the existing crossover, install two new terminals and use identical amps on both sections(either horizontally or vertically). |
Rodman99999...I don't have a schematic of such a complex crossover. Have you calculated the power dissipation? (I bet it is darned small). If you can't do it, provide a schematic and I will. |
What amount of power would be dissipated would not concern me. You brought that up. The signal degradation, resulting from by those devices dissipating energy, and the differences in a circuit's impedances brought about by removing a reactive device(the woofer) would be my concern. How accurately do you suppose the midwoofer in the system(schematic) I posted would perform, were the woofer removed from the circuit? What I'm pointing out is that it's foolish to make blanket statements, without knowing the design of the OP's crossover. |
Rodman99999...The originator of this thread was concerned about "crossover parts that make up the low pass to the woofer still using up energy from my amp".
If you check my prior comment you will see that I was also concerned about the effect on the high pass signals. |
You're correct on both those counts. I was stating what would be MY concerns in such a situation, and (again)addressing the blanket statements. It would be nice to hear from the OP, regarding the complexity or simplicity of his X-over, so his question could actually/accurately be answered. |
>If I was to unhook the wires to the woofer of my (non-biwireable) 3 way speakers, would the crossover parts that make up the low pass to the woofer still be using up energy from my amp, or is there no energy loss since the circuit is not completed?
You don't want to do that because you're going to loose baffle step compensation, the high frequency roll-off needed to sum-flat and any notch filters present.
Energy used is also the wrong way of looking at it.
Passive bi-amplification would be more appropriately called active bi-wiring because the same signal is being fed to each amplifier which is in turn limited by the peak voltage of the summed signals.
An amplifier good for 100W into 8 Ohms will swing 40V peak positive and negative, thus allowing for a 20V peak signal into each of the high and low pass filters of a 2-way or 25W per for 50W total with sine waves. I'm going to completely ignore that driver impedance is reactive and concede that's a simplification with the real numbers being more like 22V and 18V for typical 2-way cross-over frequencies for 30W and 20W for the same 50W total on sine waves.
When you split the signals before the speaker level cross-over, each amplifier sees the same input and clips at the same place it would (assuming competent amplifier design) with just a single amp. With two 100W amps, or even a beefy 200W amp on bass and 100W on the tweeter you're still getting only 50W total out (with a 3dB crest factor; 25W with a 6dB crest factor, etc).
That's not interesting.
You can come up with all sorts of pseudo-science about not having the DC resistance of coils in the picture, although their tenths of an Ohm are inconsequential against the 5+ Ohm DC resistance of an 8 Ohm driver's voice coil.
To get performance gains you need to split the signals before getting to your power amplifiers and scrap the speaker level cross-overs. Typically that's done with active circuits although passive line level implementations are also possible.
That needs to be at least as good as the transfer function provided by your passive cross-overs which includes compensation for baffle step, rising response, driver resonances, differences in the acoustic centers, etc.
Obviously none of that is present in an off-the-shelf unit or even a programmable one just set for cross-over points and slopes.
You're not going to duplicate that without measurement capabilities and filter design knowledge; so if you want to bi-amp for performance you need to buy speakers with an outboard line level cross-over or build a proven design that works that way. |
All that's why I replaced my modded Dahlquist DQ-LP1, with a modded TacT RCS 2.2X, after 23 years. It was Linkwitz's writings, in the early eighties, that got me started bi-amping at home. I'd been doing it for years before that, in live venues, but his articles inspired listening room experimentation, and the first LS3/5A's that I built. |
Sorry to get back so late. The speakers are Mag 20.1 and I disconnected the woofer by not hooking the wire from the crossover to the woofer inputs on the panels. I am using open baffle subs for 110 Hz and lower and it sounds great. I split the signal from my preamp. One leg to my amp and then to the Mags and the other to a Velodyne SMS1 and then to another amp where the output signal has low pass of 110 Hz at an 18 db/oct filter. This is what Magnepan recommends as a frequency and slope if I choose to bi-amp. As to why I did this, is because the Mag woofer is the worst part of the speaker. The mids and highs are glorious, but the woofer is not very dynamic and need tons of power. WTH, who needs that? This is just an experiment though, but I must admit, it does sound good. Thanks for all the feedback. |
The 20.1 crossover is jumpered, and as long as you are removing the LF signal from the input, via an active x-over(with jumpers removed); you shouldn't have any issues. I'm, using a modded TacT 2.2X to actively bi-amp my Maggies, with tubes above 250Hz/SS below w/a 10th order slope and transmission line woofers. Open baffled woofs would(of course) be accurate/fast enough to seamlessly blend with planars also, if driven with amp that can control them, and avoid excessive overhang(amp and woofer have to trace the signal faithfully). An interesting balancing act. |
Koestner -- Since the Maggies are designed for both bi-wiring and bi-amping, and you are using their passive crossover to feed the mid/high frequency section, why didn't you just disconnect the low frequency section by removing the jumper from the low frequency crossover input? Rodman99999: The 20.1 crossover is jumpered, and as long as you are removing the LF signal from the input, via an active x-over(with jumpers removed); you shouldn't have any issues. It sounds like he is not doing that. He is supplying a full-range signal to the Maggies, which goes through the speaker's passive crossover to the high frequency panels. And he's using an electronic (active) equalizer to provide a low-pass function for the signal which is applied to the separate open baffle subs. I suppose that's within reason, if not ideal. Regards, -- Al |
I am not familiar with other Maggie crossovers, but the MG1.6 crossover, while simple in concept, has features which many external low level X/O lack. High pass is a simple 6dB filter. Low pass is 12 dB. The break frequencies are not the same, and the highs are connected out of phase. Evidently Magnepan has designed its crossover to accomodate characteristics of the unique drivers. I would have to think twice before biamping a MG1.6. Rather, I rebuilt the passive X/O using high quality parts. |
The 20.1 X-over's Hi-Pass section has 120.3uF of capacitance after the jumpers and before the signal is further split into MF/HF. If he's not removing the LF via an active x-over b4 the main amp, he's basically "passively bi-amping". Not the cleanest or best way, but it'll work. |
Yes, it seems that I am passivly bi-amping the Mid/high by sending a full range signal through the maggie crossover. I did this because I did not want to mess with the best part of the speaker. I couldn't do a better job at voicing the speaker than the manufacturer could. So all I am doing is cutting off the woofer panel and actively powering the lows (<110 Hz.) through an open baffled bass module. I tried removing the jumpers and hooking to the mid/high of the external crossover but I got no sound at all this way. I don't know why. |
Are you the first owner of those Maggies? Perhaps someone modded the X-overs? If they are original, and you get no output, correctly hooked up/jumpers removed; something's amiss. |
Inductors and capacitors do not soak up power and get hot in the sense that a resistor does......and therefore don't produce lots of heat.
However, given improper design, you have a situation where the current and voltage are out of 'sync'....This can be measured in degrees of displacement. At 90 degrees, for example (never seen in a loudspeaker) there is NO POWER delivered to the load. So, even if you had a 500 watt amp and 93db sensitive speakers, they would be silent, at least at the frequency where the 90 degree displacement occurred.
Lesser amounts of displacement result in power loss as well.
This is called POWER FACTOR and is the real reason some speakers can be considered a BAD LOAD, not simply low impedance.... Or my Maggies, though power hungry, would be considered such a bad load. They present a fairly benign phase angle situation above and below the 600hz xover.
This is also the difference between VA and power in Watts, also measured as the product of volts and amps..... |
