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The question is pretty broad, so I'll try and cover all the various answers.


(1) You can find prosound active crossovers that are 2, 3, or 4 way mono and stereo units that allow for easy adjustment of the crossover point and levels. These use state-variable circuit designs, and are typically considered to be inferior sonically. They also are designed for pro-level signal levels (+10v instead of -4v, though the scales of each don't exactly correspond) and may have problems integrating with consumer gear. In my experience, I've found that the input and output gain structure of these units allows for them to be completely compatible with consumer gear, even if the solution isn't "ideal." I've also found the impact on sound quality to be negligible... probably because any noise or distortion introduced by the state-variable circuit is swamped by the benefits of using active amplification and removing the frequency dependant nature of passive crossovers. Behringer, Rane, dBX and others make these crossovers... I have used the dBX in the past. I should note that I'm talking about analog crossovers here. These companies also have (most do, anyway) digital crossovers that include an extra analog/digital and digital/analog stage. These offer a tremendous increase in flexibility (user adjustable/programmable filter types, points, orders, levels, digital time delay, etc.), but may sacrifice sound quality due to the A/D and D/A stages. I have no direct experience with these types of crossovers and can't comment directly on how great the impact on sound quality may or may not be.


(2) Some companies make kit or assembled active crossovers (analog) that may suit your needs. The most well known (and the only one that comes to mind at the moment) is Marchand Electronics. They offer active crossovers of most designs, and the ability to select the crossover point/slope etc. before ordering. Some are made with a slot that can be interchanged for other slots (purchased separately) to "play" with various crossover points. I think they might even have versions that are tube-based. I don't know if they include level matching, however. The sound quality of the Marchand crossovers is reputed to be excellent, though I have no direct experience with these either.


(3) You can build your own active crossover using an available board layout. The most familiar to me, since I have used it in the past, is the board available from Rod Elliot . This board is a Linkwitz-Riley design that can accomodate a two-way crossover of 12 or 24 db/oct, and also has provisions for signal level matching/control. When using components of respectable quality, I can attest to the sound quality of this crossover - when I've experimented and made the bandwidth of the passband extremely wide (essentially an all-pass), I could not determine when the crossover was in or out of the signal path. I believe this crossover to have excellent performance. The filter type however isn't flexible (AFAIK), nor is the slope (6db and 18db/oct are not available, AFAIK). If it still meets your needs though I would recommend taking a closer look, as the value and performance are excellent.
 

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I bought a BRS active xover about 8 years ago. It's a switchable 2/3 ways.


I am not using it right now so if you're interested give me a PM or Email.
 

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Bryston makes some:

http://www.bryston.ca/crossel.html


Behringer makes some (1 is digital 24/96):

http://www.behringer.com/02_products...mid=2&lang=ENG


Deqx makes one with an extremely powerful processor:

http://www.deqx.com/


I'm sure there are others.


I use the Behringer Ultra Drive on my fronts and it works great. The passive x-overs were 2nd Order Butterworth and I replaced them with 4th Order Linkwitz-Reilly. The transition between drivers is now far more seamless and there is no more peakiness.


It sounds much better also because it takes less amplifier power to drive the speakers to the same SPL.


It's a very flexible unit for a bargain price. It contains Parametric EQ as well as time and phase correction.


I've been actively biamping since 1978 or so, and I definitely think that this is the new direction for loudspeakers.
 

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Discussion Starter #7
I am looking into building my own speakers for HT like the Andromeda—6 of them. I really like the design of the satellite speaker and would modify the sub cabinet ( design wise) to match it and find a different less expensive driver for the sub. I have looked at the LAB 12 by Eminence, and it seems to be a very good candidate. Tight accurate bass response is important to me. My understanding is that this is more a function Q rather than the size of the driver. The Tempest is also a consideration, but is a crossover point of 300 hz to high? Is a 15 in driver to big for tight accurate bass? The sub cabinets will be sealed.


The satellite speaker uses a Scan-Speak 9700 Tweeter and a Scan-Speak 8545 midrange.


The active crossover is for this satellite-sub combination. My amps are a 5 channel Sunfire Signature and a 5 channel Sony ES 9000. My current speakers are Krix HT.


I am going to start by building the subs and use active crossovers with the Krix speakers. Then eventually build the satellite speakers.


Rod Elliott gave the most compelling argument for bi-amping—the only compelling argument, for bi-amping that I have read. He is an incredible wealth of free information.


The crossovers are the biggest obstacle in the whole project. I am somewhat intimidated at the thought of building my own—yet, the cost needs to be kept under some control. I do not want anything that will induce noise into the system. I want the ability to equalize the room modes. The Beringer looks like a good option. The compromise in sound quality vs. building Rod Elliott’s design is an unknown.


Thank you all for the input. I hope my ramblings have clarified where I am going with this project.


JamesE
 

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If you use well respected, fast, quality opamps in Rod Elliot's crossover design, you can rest comfortably that any noise introduced will be far below your ability to hear (this might well be the case for many cheaper opamps as well, but with the minimal expense and "unknown" factor for you, it might be worth it to put your mind at ease and use quality components).


300Hz is pushing it for the Tempest. However a 15" sub is perfectly capable of producing "tight" accurate bass. IMO, most people associate tight, fast bass with the higher frequencies of bass insruments, and often with systems that lack flat response down to 20Hz. There is nothing inherent in a 15" driver that would make it "slow" for bass. Enclosure tuning and blending with midrange/midwoofer drivers are the critical factors. Other good sub drivers to take a look at are the Adire DPL12 and Shiva, Dayton Titanic line, and Stryke AV12 and AV15. Note that all of these will be somewhat stretched to crossover at 300Hz seamlessly.


Room modes are a low frequency problem. As such, I would suggest using a dedicated component to treat this low frequency region, and avoid building that EQ functionality into the crossover. For example, use Rod Elliot or Marchand Electronics crossovers in addition to a $120 Behringer Feedback Destroyer for low frequency equalization.
 

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>>Rod Elliott gave the most compelling argument for bi-amping—the only compelling argument, for bi-amping that I have read. He is an incredible wealth of free information.
 

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Discussion Starter #11
"And that would be the lack of phase error, the increased efficiency, the ability to tailor hardware? You say something cryptic like that, and then you don't share!"


Sorry, my links didn't post. Elliots link is http://sound.westhost.com/


His articles are detailed and I found them interesting. I'm still reading.



"Note that all of these will be somewhat stretched to crossover at 300Hz seamlessly."


The Scan-Speak 8545 midrange is flat to 100 hz. Where would you put the crossover?


JamesE
 
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