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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