Recommendations for active crossovers

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Bigus Dickus

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My recording needs are all filled for the moment (thank God :D ), but the new home theater being designed is in desparate need of crossovers.

I'm hoping you guys can make some suggestions. I'd like linkwitz-riley 24db/oct slopes, and I need both three-way and two-way models. The option to sum low pass for a stereo pair would be nice.

So far, I've found this dbx XO that seems pretty nice - the right slopes, very flexible, and at $180 street the price is right. The only negative is the somewhat low spec'd 92~94 db S/N ratio. I would have thought an active XO could easily maintain 100+db.

I'm not all that familiar with the prosumer gear crossovers. There are some nice Rane and Marchand pieces, but they are pretty pricey. I'd like to keep it in the range of the dbx price of ~$100/channel if possible.

Any suggestions of what to take a look at?
 
Any suggestions?

Behringer has a very flexible and inexpensive option, but I've heard people complain that it introduced noise (high frequency hiss) into the system.

You guys know of good priced "quiet" crossovers?
 
Man, I can't find any specs on that unit listed on Peavey's site.


I was told by someone on another forum that, due to the pro gear being designed for +4dBu and consumer gear being designed for -10dBv, the self noise of these pro crossovers would be much higher (relatively) when used with consumer equipment. Thus, the S/N would be even worse than indicated.

Does that sound right? Is there any easy way to step up my line level voltages before the XO, and back down before the power amps, or is that completely unecessary? Can a +4dBu unit be modded to work more "correctly" with -10dBv equipment?
 
Ummmmmmm...how do you know that you need a 24dB slope at your crossover point?

The first thing I think of here is that most crossovers use a 12dB slope. A "few" have selection to go 18dB to interact well with JBL drivers (I can't imagine why ALL crossovers don't have at least an internal switch that would switch between 12 and 18dB, but who knows.....).

DO NOT use something that only works at +4 with -10 gear!!! If it doesn't work at -10 to interact with your other electronics, you will be having some operating level problems for sure.

Sorry, I don't have a recommendation that cheap.

Ed
 
I know I need a 24db slope for two reasons: it's the industry standard for playback systems, including Dolby labs, DTS, and THX recommendations; and unless I have a phase adjustment built in to the XO (or in a separate component) then 12db and 18db slopes are out due to phase incoherency in the crossover region. There's a reason people prefer the 24db Linkwitz-Riley slope. ;) Of course, even with the 24db/oct being in phase, there will still be time-alignment problems, due to it being 360 deg "in phase" instead of 0 deg. Much better than frequency dependent phasing though.


About the +4/-10 issue... damn! :( :D

I checked the dbx specs, and the input gain is adjustable from -12dB to +12dB. IIRC, the difference between the +4dBu and -10dBv is about 12dB, right? I wonder if that gain adjustment would allow the signal level to be brought up enough to function adequately? I could see how noise/hiss could be a problem. In fact, the output gain can only be attenuated -6dB, so you'd have a net +6dB gain going through the XO. Not too good! :)

Maybe +6dB on the input, and -6dB on the output would be "good enough." Oh well, for that modest price, I've ordered one to play with. If it's a complete flop, I'll take the loss selling it. Probably no other way to really find out if it will work ok or not.
 
This is for a home theater? I try to just listen to most technical recording/progear conversations around here, but I pretty well know my shit about home theater... So what are you talking about? You're confusing me.
What kind of equipment do you plan on using in this theater, and why do you think you need a cross over?
 
lol, yeah, I suppose some more information would help. :)

Here's the deal... I'm using Magnepan planar's all around for multichannel music/movies. IMO, they don't have adequate low frequency output, especially for theater.

For the fronts, I will only need augmentation in the true subwoofer range since I'm using decently large maggies (3.6's). The sub design will be a custom DIY build with outboard amplifier, so I'll need a 2-way crossover for the L/C/R channels (high-pass for the maggies, low-pass for the sub).

For the surrounds, I'll be using smaller maggies that could really use some mid-bass supplementation as well (MMG's). I could just use a 2-way and send that information to the main sub, but at the somewhat higher mid-bass frequencies I would prefer to retain the directional cues (especially for multichannel music formats - DVD-A and SACD). Therefore, I am toying with the idea of adding a small sealed mid-bass enclosure at each surround location (L/R sides/rears). Thus, I'll need a 3-way crossover for each surround channel (high-pass to the maggies, mid-pass to the sealed mid-bass enclosure, low-pass to the main sub).

That's a total of seven channels of active XO's. AFAIK, there just aren't any "packaged" seven channel XO's on the market. Outlaw audio has a six channel that isn't nearly as flexible as I'd like. Paradigm has the X30 which is similar. Preamp/processors usually have some bass management ability, but not nearly as flexible as I'd like (and they tend to to not work at all when using analog inputs from DVD-A or SACD :( ).

"Audiophile" active crossovers aren't cheap, either. Even in kit form, Marchand XO's would cost me around $400 per channel, and have an essentially locked XO frequency (meaning you have to spend more money for extra modules for extra XO frequency points if you don't guess correctly the first time around).



Enter pro-audio gear. Active crossovers are cheap (from $40 to $200 per channel) and flexible (essentially infinite XO frequency points, input/output gain, phase inverts, low-pass summing, etc.). If I can find a way to make one (dbx, Behringer, Rane, Peavey) work for my home theater needs, it could save me between $1200 and $2500!
 
OK, but what are you using for for a reciever, or are you using a surround preamp and amp(s)?
 
Pre/pro and separate amps. I currently have 10 matched channels of amplification, and will add whatever is necessary for the main sub (not the midbass...). I may add a more powerful amp than what I currently have to drive the Maggie 3.6's. If it turns out I don't need all the amp channels (i.e., if I decide not to add the midbass enclosures), I'll simply sell the excess. I picked them all up at great prices over the years (5 Rotel RB-981's), so no harm done.

My pre/pro is an analog Rotel prologic unit, and I'll probably keep it until they standardize some kind of digital link between DVD-A/SACD and processors. Even then, I don't expect the digital crossover in a pre/pro to give me the ~14 channels I'm considering.

I've had mixed suggestions on the cheaper pro crossovers like the dbx and Behringer. Some say they're fine for full range, some say they hiss and/or are noisy, some say the level matching is impossible to work with, some say they didn't have any problems at all...

I'll find out for myself soon enough - but if you have some other options I should consider, I am all ears! :)
 
You can't buy an infinte baffle sub as a nice packaged unit with amp. ;)

No, this is something I'll have to build into the room. Outboard amplifier - probably something from the prosound world... QSC, Crown, etc.

Besides, even if I had a powered sub with its own crossover, that would only produce the low pass sub signal, and on some brands a high pass line level output for the satellites. If you wanted low frequency information from seven channels to be summed for the sub, the crossover would be useless for generating the high pass satellite signals.

So, I'm still stuck at square one... needing quality active crossovers at a decent price. The dbx should be here in a day or two, so I'll know soon enough if the prosound XO's are going to be a viable option or not.
 
Not to mention, the components that you've mentioned simply deserve better than berhinger or dbx!
 
My current pre is the RSP-960AX. Dolby prologic only, and it does have a sub out. Unfortunately, the single crossover frequency will not be adequate for the whole system, and it still doesn't high-pass the signal for the maggies. In fact, very few preamps get anywhere close to the level of bass management I desire, and those that do still fall short.
 
Cool Bigus. Sounds like it will be a hell of a system. :) I don't play around with any of that dolby/thx/dbx surround stuff so wasn't aware of crossover requirements of the drivers.

Ed
 
Bigus Dickus said:
My current pre is the RSP-960AX. Dolby prologic only, and it does have a sub out. Unfortunately, the single crossover frequency will not be adequate for the whole system, and it still doesn't high-pass the signal for the maggies. In fact, very few preamps get anywhere close to the level of bass management I desire, and those that do still fall short.
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Forgive me, I'm still kind of confused... It sounds like you are trying to build a 7.1 system off of a prologic pre amp. Is that about right?
If that is the case I couldn't reccomend enough, a new pre. How do you plan on decoding 5.1, dts or anything beyond?

My preamp is a couple of years old now but I love the fuck out of it. It's an anthem avm2 made by sonic frontiers. It allows for a multitude of control on each separate channel and it sounds so fucking good that it alleviates all need and desire for anything between it and the speaker except for a good amp. And it sounds like you've got that covered.

You can't buy an infinte baffle sub as a nice packaged unit with amp.
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Yes you can. http://www.ruark.net/ has an example of one. I think it's called the log rythym.

My sense is that you are making things more complicated than they need to be if you had a newer pre. Granted that's going to take more than 100 or 200 bucks but it would be worth it for the sound difference. Plus Prologic is long dead, you need a different processor for a good theater, and you wouldn't be having to go through all of this with a newer pre/processor.


or...
Have you been here?
http://f20.parsimony.net/forum36475/
And I found a few other's but I lost em. Sorry.
 
also
My pre/pro is an analog Rotel prologic unit, and I'll probably keep it until they standardize some kind of digital link between DVD-A/SACD and processors. Even then, I don't expect the digital crossover in a pre/pro to give me the ~14 channels I'm considering.
Click to expand...
I'll admit I haven't studied up yet on what kind of link that may be. But just as an example, my preamp has rs232, firewire, and digital aes/ebu connections on it. And I know alot of the newer units in that class have mega upgradeability for the future.

And... Even if you run 100 channels off your current pre, it's gonna sound like shit (comparitively). More speakers in a hometheater do not necessarily mean better sound or surround, especially if your still only sending out prologic.

I guarantee you Bigus, if you were to upgrade your pre to a 5.1 or 7.1, quality unit it would change the sound so much that you wouldn't need any of this other stuff. I bet you wouldn't even recognize your speakers sound anymore once they all worked in true unison. Get a nice powered sub, or if you really want to build an ib into the wall, but FOR GOD"S SAKE don't use any cheapass pro gear with your hifi gear. I've blown alot of speakers mixing the two, and you'll never get close to your gears capability with that shit plugged into it.

Check this out.avm2 on ebay
I paid twice that and would do it again.

I know this doesn't help your xo question, but the new pre is the answer to your problem.;)
 
subtractor said:
Forgive me, I'm still kind of confused... It sounds like you are trying to build a 7.1 system off of a prologic pre amp. Is that about right?
If that is the case I couldn't reccomend enough, a new pre. How do you plan on decoding 5.1, dts or anything beyond?
Click to expand...
Damn, no wonder you're confused... I left out half the description! :D

In addition to the Rotel ProLogic preamp, I have a Marantz DD/DTS decoder as a stand alone unit. However, I certainly do plan on upgrading to a 7.1 prepro in the future (and the Anthem units have already caught my eye), but I'm not going to do so until they standardize the multichannel digital link and get rid of some of the multiple D/A, A/D, D/A, A/D, D/A stages required currently.

In building a new theater, it's important to thoroughly examine where speakers will go so that proper acoustical treatment and placement issues can be resolved up front. Therefore, I'm designing based on a 7.1 channel format, and will upgrade prepro when the time is right.

Yes you can. http://www.ruark.net/ has an example of one. I think it's called the log rythym.
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Well, that's not an infinit baffle sub, unless I missed something on that site. ;) I'm pretty firmly sold on the virtues of infinite baffle design, much as I am on the virtues of active crossovers and bi/tri-amplification. The theory is sound, I've heard it in practice, and I want it! And I have been to the cult of the infinitely baffled... very informative site.

My sense is that you are making things more complicated than they need to be if you had a newer pre.
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Very possible. In fact, if I waited long enough there will probably be a prepro that uses a digital link between DVD-A/SACD player and the prepro, does all crossover and parametric equalization in the digital realm, and has only one D/A stage after all processing is done with a possible 20+ channels of D/A conversion and analog output. That would be ideal, but it doesn't exist and probably won't for another two years or so. As an alternative, I'd be happy with one stage of D/A conversion and all crossover and EQ functions done in analog - but at line level, not amplified, to avoid all the nasties that passive crossovers exhibit.

Sorry for the confusion. I know what I'm seeking is complicated, but I truly believe the sonic benefits are worth the trouble. Seven discrete channels, and at a minimum active bi-amplification on all channels.
 
That would be nice.
But the approach your taking doesn't match with the equipment you have. I can't find anything that says the rb981's are biwireable. How do you plan on biamping with amps that are not wired for it? I assume this is where the crossover comes in. Am I right?
It's not the same thing.
You need voltage and current outputs on your amp(s), and speakers.
In my opinion biamping rear speakers, especially in 7.1 where you have a rear sub and rear center speaker available is unnecessary.
But if you just gotta have it...
You need to adjust your budget!

You have high quality gear. The secret to a good theater is quality components, and as few pieces in the signal chain as possible. Quality pre/processor>quality amp>quality wire>quality speakers.
There is no room in that equation for anything that costs $200, except for maybe 50-100 feet of speaker wire.
I wished you lived near so I could hook up my anthem with each of your amps bridged going into 5 of your speakers with a sub added on.
In my opinion unless those amps DO have voltage and current outputs your best bet is a new pre-processor and whatever sub solution. That your signal will be cleaner and your speakers will sound better. With a good sub, you won't notice any lack of low end on the planars, and your shit will sound like you never knew it could.
I say the rotel prologic pre and the marantz processor is where the problem is at.
I had 2 klipsch klf 30's in the front with the c7 center, klf 20's in the back AND the smaller surrounds (can't remember the model#), using a sunfire cinema grand 2 amp (5 x 405 watts rms), and I was driving it with one of denons best avr recievers and never knew how fucking bad it sounded till I got the anthem. It was night and day.
Let me know how the dbx works out.


And about that sub...



From our Contemporary Series comes the Log-Rhythm subwoofer. This uniquely styled unit features a highly specified 150 watt amplifier coupled to fully optimised long throw 12" drive unit. The elegant enclosure features isolation poles on each corner so the unit can be fully stabilised in operation and removable decorative veneered side panels, enabling swift change of finish to match customers needs.

The Log-Rhythm has been universally praised by press and public for its pure and accurate bass performance making it equally suited to both music and film sound-track reproduction.

System Type:
Infinite Baffle Sub-bass system with on-board amplification and active filtering. Fully optimised enclosure manufactured from critically damped 25mm MDF with corner steel isolation poles.

Drive Unit:
300mm high-efficiency unit. Extreme long stroke composite fibre cone driven by 50mm voice coil. Heavy-duty non-resonant steel chassis and fully optimised stacked magnet system.

Amplifier:
150W RMS DC coupled bi-polar

Inputs: High Level 100 ohm unbalanced via Neutrik Speakon connector
Low level 10K unbalanced via gold plated RCA connectors

Frequency respose: 30 - 120Hz

Nominal impedance/input voltage: 220/240v (110/120v) where applicable

Sensitivity/Features: Variable 180° Phase control
Input-Output facility
Automatic Standby Mode
High and low level mixing capability

Dimensions HxWxD: 420x430x430mm

Weight: 25Kg

Finishes: Slate Grey main cabinet with optional panels available in Natural Cherry, Red Cherry, Natural Oak or Black Oak Veneers


But my Klipsch ksw15 will stomp that little bitch!
 
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