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“What is Active Bi-Amping/Tri-Amping?” Active bi-amping uses one amplifier for low frequencies and another for mid-to-high frequencies—per audio channel. Tri-amping adds one more amplifier for a 3-way system tweeter. This is done via the use of an active crossover unit which is inserted between the preamplifier and power amplifiers. “What are the advantages of active bi-amping/tri-amping?” It provides much greater driver control than a passive crossover/full-range-loaded amplifier configurations. It provides a better load for your amplifiers to drive, and an effective gain in each amplifier’s effective output. It will provide lower amplifier-originated intermodulation distortion (IMD). It provides much greater protection of your tweeter/midrange drivers under clipping/overload conditions. It provides the ability to use less expensive amplifier designs for each driver. It provides for time alignment of drivers within a single speaker (a “must have” capability) It provides for better crossover performance in both amplitude AND phase in the crossover region for smoother crossover performance, including more stable soundstage imaging vs. frequency. It provides stability of crossover performance relative to passive crossover drift during and immediately after under high-load speaker output conditions, i.e., it maintains electrical output linearity under heavy load conditions. It requires lower-quality wire/connectors than a similarly configured passive crossover/full-range amplifier configuration. It allows on-the-fly changes in crossover frequency, EQ and channel gain settings to support changes in your setup configuration, i.e., facilitating the fine-tuning use of tools like Room EQ Wizard [REW], replacing individual drivers, speaker position changes, and adding channels for playback (2.0, 5.1, 7.1, etc.). “What are the disadvantages of active bi-amping/tri-amping?” It requires two/three power amplifier channels per speaker (with associated wires/connectors). It requires an active crossover unit. “What is an ‘active crossover’?” An active crossover provides separation of frequencies of the incoming pre-amplifier output signals, breaking each upstream channel into two (bi-amping) or three (tri-amping) downstream channels: a woofer channel and mid-range/tweeter channel). It provides higher-quality equalization (“EQ”) capability for each channel. Digital crossovers typically provide for delay to allow for time alignment of the drivers within a single speaker. (This is a similar function to an AV Processor that time aligns speaker-to-speaker in a 5.1/7.1 array.) “Do I need to disconnect my speakers’ passive crossovers from my drivers?" Yes. At least the woofer (or low frequency driver) must be disconnected from the passive crossover to permit bi-amping. If your speakers are 3-way (i.e., woofer, midrange, tweeter in each cabinet), then you may retain the passive crossover between the midrange and the tweeter if using bi-amping (…but for tri-amping, all drivers must be disconnected from the passive crossover networks) Can I use ‘passive bi-amping’?” Passive bi-amping does not bring the benefits of active bi-amping, only the disadvantages of extra cables and connectors. Generally, it is not worth the expense of the extra amplifier. In particular, passive bi-amping does not provide for delay adjustment or filter/EQ parameter flexibility. What active crossover brands/units should I use? Many manufacturers make active crossovers, including ElectroVoice, dBX, Yamaha, Ashley, Behringer, Rane, Xilica, Lake, Marchand, Bryston, DEQX, etc. Prices go from $230(US) to many thousands of dollars. There are also lower-cost alternatives, such as miniDSP. Price is generally commensurate with sonic performance. Have I seen active crossovers used in configurations other than an active crossover box? Probably--the "powered subwoofer" channel found on most AV Receivers/Processors is a limited example of a for-purpose active crossover channel (i.e., mono bass channel). Usual features include gain control (at the integrated subwoofer/power amplifier unit), user selectable crossover frequencies, and sometimes GEQ/PEQ (graphical and parametric equalizer) filters built into the AVR/AVP. Delay adjustment for each speaker channel is usually included in the AVR processor functionality to correct for speaker distance room placement variances. Additionally, an "Audyssey"-like feature on some AVRs/AVPs features a built-in real-time analyzer (RTA) to help the user set up their speakers in a room environment. (16 Nov. 2010 edit) Can I use a 2-in, 4-out processor (like the EV Dx38) to Tri-amp my three-way speakers? Yes: if you disconnect two of the three speaker drivers from their passive crossovers, then connect the tweeter and (usually) midrange driver to the 2-in, 4-out processor, leaving the last (usually woofer) channel connected to one amplifier, and the other two outputs from the active crossover connect to the inputs of two other amplifier channels, then you can tri-amp your speakers. Note that this will take three amplifier channels per speaker. If you are like many here, finding extra amplifiers to drive your speakers in tri-amp mode is usually not a big issue. Note that you will not have the flexibility to change the crossover frequency of the woofer to the midrange, nor be able to EQ the woofer channel with the active crossover, but you will still be able to use the active crossover to EQ the most important portions of the spectrum and digitally delay the other two drivers in order to time-align your speakers. Some Klipsch models (e.g., Heresy, Cornwall) have a long midrange horn and a direct radiator woofer. This means the the driver with longest delay -- the midrange driver -- will stay connected to the original passive crossovers, and the other two driver channels (tweeter and woofer) can be digitally delayed by the active crossover to time-align to the midrange. EDIT: 14 Nov 2016-- New users of active crossovers looking for more detail on how to install them into the setups can refer to this thread on using Xilica active crossovers: _______________________________________________________________________ EDIT: 14 Nov 2016-- Users of active crossovers seeking to set their parametric equalization filters (PEQs) easily and rapidly will be interested in using Room EQ Wizard (REW) to generate and optimize those semi-automatically. A link to a tutorial thread on that subject can be found here: Chris
Chris A posted a topic in Technical/ModificationsI recently acquired a Xilica XP-8080 active digital crossover on ebay...a new unit that had not been used, but sold as used. The Xilica XP8080 can accept up to 8 inputs and up to 8 outputs (hence its name), and is meant to be placed between your preamplifier's outputs and your amplifiers' inputs to replace your loudspeaker passive crossovers in order to directly couple your amplifiers outputs to your loudspeaker's woofers and midrange and tweeter drivers. Other Xilica crossovers in this series include the XP-2040, XP-3060, and XP-4080. These crossovers are 96 kHz sampling/24 bit units that I'd classify as "hi-fi" in terms of their sound quality. The XP-8080 is the only one in this series to use the Phoenix (a.k.a., "Euro") bare wire screw-down terminals, shown above in green, and below, disconnected: These terminal blocks are removable from the back of the unit for ease of assembly with the connecting cables. The other Xilica models use XLR (balanced) inputs, such as the following XD-4080 model: The XLR "microphone cable" connections are used on most quality multichannel preamp/processors to reduce line noise: These cables are also available with RCA "unbalanced" connections on one end (resulting in male and female cables) for those that have preamplifiers and amplifiers with RCA connectors only: Since I was replacing three other active crossovers in my rack with this one unit, I had a lot of the XLR-->XLR (male-to-female) cables on hand--most of which I bought at Guitar Center locally for about $6-$9 each cable--and I am using the XP-8080 with bare-wire connections (Phoenix), I simply chose to remove the XLR connector on one end of the cables that needed to connect with the XP-8080. Note that you can buy XLR--bare wire cables and save the cost of the extra connector. For a 5.1 multichannel system like my own, there are five input channels (+ one of subwoofer channel, usually handled separately). So I modified five XLR cables to remove the male connectors. Similarly, the XP-8080 has 8 outputs, so I modified 8 XLR cables to remove the female XLR connectors. I stripped the wires and inserted them into the respective terminal blocks and screwed them down, resulting in a cable-connector assembly looking something like the following just before inserting the supplied Phoenix connectors back on the unit: The connection of the amplifier outputs to the loudspeakers is your choice: you can assign input channels to output channels in software, as shown below. If you're using different types of amplifiers (tube and SS) the figure below is a typical connection for "horizontal bi-amping" for two channels: For the XP-8080 crossover, this one crossover is actually the equivalent of four stereo biamping crossovers in one box (assuming bi-amping all loudspeakers), or tri-amping two front loudspeakers and bi-amping a center loudspeaker...or in my case, bi-amping the front three loudspeakers, and mono-amping the two surround loudspeakers (two '79 Cornwalls using their passive crossovers). For me, one XP-8080 is crossing my entire 5-channel system, with my AVP providing the separate subwoofer channel outputs to two DSP front-end subwoofer amplifiers (Crown XTi-1000s) that do the EQ and amplifying for the two TH subwoofers (TH-SPUD clones). After I made the connections for the XP-8080's channels and connected their other ends to their respective preamp outputs (5 channels), and downstream amplifiers (four stereo amplifiers--including 3 Crown D-75A rack amplifiers and a First Watt F3 class-A single ended FET amplifier), I was ready to program the XP-8080 using their supplied XConsole software (Windows and Mac supported)... Next up: programming the Xilica using "XConsole" software
Chris A posted a topic in Solid StateLooking at the Active Bi-Amping/Tri-Amping FAQ, it was stated: This thread will provide insights and listening experiences on using solid state (SS) amplifiers for bi-amping and tri-amping, and the reasons for the disproportionate increase in sound quality (SQ). Let's start with the most obvious reason: 1) The reduction in the load that each amplifier drives. For example, it has been noted the there is an average power split between bi-amped loudspeakers based on the crossover frequency chosen, with the 50-50 power split frequency close to the 350 Hz band. If you bi-amp with a crossover point around 350 Hz, then you can expect to need only half the rated output power for each bi-amping amplifier. This is a real advantage for the low-wattage amplifier crowd, including tube/valve amplifiers and chip amps. By bi-amping, even sub-watt amplifiers can drive their loudspeakers to higher SPLs without accompanying distortions produced by each amplifier. Since these lower power amplifiers often cost much less than higher power amplifiers, the economic advantage of bi- or tri-amping becomes more attractive. If Tri-amping, the audible spectrum (i.e., 20-20,000 Hz) can be broken into three parts, with each amplifier requiring, on average 1/3 the output power to produce the same loudspeaker output SPLs. 2) The elimination of amplifiers driving unnecessary resistive and reactive loads that passive crossovers introduce. This usually isn't talked about by the "old school", especially by those that otherwise "distrust" active crossovers, since it isn't pleasant to talk about when defending passive crossovers. . It isn't a secret that real-world acoustic drivers all have resistive and reactive characteristics. What's not discussed is how much more resistance and reactance is added by the passive crossovers. In some cases, the added resistance and reactance is greater than the drivers themselves. If you look at the older passive crossover designs used by Klipsch on it's Heritage loudspeakers (particularly the Khorn), you will see impedance swings from 4.2 to 43 ohms on the frequency vs. input impedance curve: Direct-coupled amplifiers are amplifiers that do not require an output transformer to couple to the loudspeakers without presenting a higher amplifier output impedance to the loudspeakers than the loudspeaker's input impedance. Solid state amplifiers are typically direct coupled amplifiers--with noted exceptions. SS amplifiers lose many of their advantages when driving loudspeakers with high levels of load reactance, of which unnecessary contributions are generated by passive crossovers. Direct coupled amplifiers "like" resistive loads. Most of the output power stage design differences between typical Class AB and Class D SS amplifier designs lie in how the amplifiers are designed to handle complex and non-linear reactive loads. By minimizing load reactance by direct coupling loudspeaker drivers without using passive networks, the amplifiers themselves can do a better job of faithfully reproducing the music via the loudspeaker. Driving highly reactive loads contributes negatively to the resulting sound. Additionally, the amplifiers in a bi-amp or tri-amp configuration are not driving any parasitic resistive loads that simply dump a significant fraction of amplifier output to heat: all the amplifier's output is going directly to the drivers themselves - direct coupled. 3) Reduction of modulation distortion (FM and AM), transient intermodulation distortion (TIM, i.e., "slew rate" distortion), and zero-crossing distortion via separating low frequency/high amplitude signals from high frequency/low amplitude signals. Much of the discussion centering on amplifier "classes" (A, B, AB, C, D, etc.) is tightly coupled to non-harmonic distortion types, including modulation distortion, transient modulation distortion (TIM, otherwise called "slew rate" distortion, loudspeaker impedance-coupled frequency response distortion, zero-crossing distortion (i.e., higher-order harmonic distortion) and clipping distortion (higher-order transient harmonic distortion). The objective of using the different types of amplifier classes or architectures is the avoidance of these type of distortions, not the introduction of any them into the signal path. By separating low frequency/high amplitude signals from higher frequency/lower amplitude, better choices for amplifiers of differing classes and strengths/capabilities can be used. For instance, amplifiers of very high slew rate (low TIM), low intermodulation via fewer gain stages and lower levels of feedback can be direct coupled to the HF drivers that typically exhibit capacitive reactance , while high output current/voltage low output impedance amplifiers can be direct coupled to the LF drivers, drivers that often exhibit large relative amounts of inductance reactance. Additionally, it is well known that LF drivers are usually much less efficient than HF drivers, such that output gain matching can be accomplished by the amplifier gain controls or the active crossover without resorting to increasing impedance or resistance in the signal path to pad down the HF drivers. This last point (reduction of non-harmonic distortion levels) using bi-/tri-amped amplifiers of differing types that are individually more optimal for driving the their respective loads at lower overall non-harmonic distortion levels -- is the greatest single advantage that is achieved via active bi-/tri-amping. This aspect of bi-/tri-amping is also the one that receives the least visibility and understanding, and that likely makes the largest difference in the sound quality improvements over typical passive crossover - single amplifier/loudspeaker configurations. Chris
I have been using an active crossover for some time (minidsp). The latest project I have worked on, Belle bass bin/prv horns with Ev drivers, in a two configuration. Has forced me to play around a bit. First I had to turn off Audessey, then a couple of weeks ago I had to remove all eq settings from the minidsp. Tonight I even changed the crossover setting to just 600hz. After spl matching all drivers at the sweet spot. Things are really sounding good. I remember DeanG giving me crap about playing around with an active some time ago. I wonder if he was referring to all the crap I was attempting to implement into the system ( as far as equing goes). I have often wondered how some passives would do me good on most of my experiments. My problem is dropping the $300-$400 minimal on passives, to find out they won't work. Especially when decent actives can be had for that amount. I don't want to turn this into a passives or actives are better than one or the other. But I would like to know how simple passives are compared to equing and time aligning with actives. This has been covered before, but how can we keep it simple to sound good. Are there lower cost passive designs that will sound as good if not better than setting a crossover and the spl level of each driver?