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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 5:17 am 
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Philosophil wrote:
libor wrote:
Phil......many articles on the net....you have your regular preamplifier....you run it into the active crossover..from that crossover you have low, mid, high (even 4 way or just you can ad another crossover) and you run low to your bass power amp (whatever it is) mid to your mid power amplifier for the midrange and you guessed it high to the tweeter amplifier...that is you can have 3 stereo amplifiers to run the whole system....and most of the good crossovers have gain, phase so you do not have to have any sort of gain adjust on your amplifiers. And the cherry on all of this...you can have some big power(SS, class D) amp on the bass...some nice class A (SS or tube) amp for the mids and some 1 Watt SET for your tweeters....

Thanks, libor. That's really helpful, especially the part about being able to use different amplifiers for different drivers.

Can you control things like frequency response as well, or would that require some sort of separate measuring system? I ask because I'm one of those 'weird' guys who prefers that the sound of things like the voice of CBC announcers be reasonably faithful to how they would sound if you were talking to them face to face. :wink:


Phil.

Many used pro electronic X-overs have specs that rival many of the esoteric high $$ audiophile offerings, I have 2 DBX driverack PA speaker management units with these capabilities:

• Setup Wizard Steps Through Speaker and Amp Selection and Levels
• Auto Level™ Wizard Balances Your System
• Auto EQ™ Wizard with 28-Band RTA Tunes Your System For The Venue
• AFS® Wizard Helps Eliminate Feedback
• Stereo Feedback Elimination with 12 feedback notch filters
• dbx 120A Sub-harmonic Synthesizer
• Classic dbx Input Compression
• JBL® Speaker and Crown® Power Amp Tunings included
• USB Firmware and Speaker Tunings Field Updatable With Harman HiQnet™ System
Architect
• Full time RTA function
• Front-Panel Output Mutes
• Pink Noise Generator (used with Auto EQ and Auto Level Wizards)
• Linked Stereo DSP Processing for ease of use
• 24-Bit ADC/24-Bit DAC, >113 dB Dynamic Range
• 2-Channel XLR Input and 6-Channel XLR Output
• 2x2, 2x3, 2x4, 2x5, 2x6 Crossover Configurations
• Dual 28-band Graphic EQ- Linked or Dual Mono
• Stereo Multi-band Parametric EQ
• Stereo Output Limiters
• Output Alignment Delay
• Power on/off Mute Circuitry
• Front-panel RTA-M XLR input with phantom power
• 25 User Programs/25 Factory Programs
• Full Graphic LCD Display
• Front Panel Input and Output Meters

System performance:

Dynamic Range: 110 dB A-weighted,
>107 dB unweighted,
THD+N: 0.004% typical at +4dBu, 1 kHz, 0 dB input gain
Frequency Response: 20 Hz – 20 kHz, +/- 0.5dB
Interchannel Crosstalk: <-110 dB, -120 dB typical
Crosstalk input to output: <-100 dB

These were a bargain when new and can be purchased used for $500 or even less if you are patient.

I understand that Behringer have units with similar specifications and are also used with some new speaker systems such as Emerald Physics.

These units can be tricky to set up, but once you have figured it out the flexibility is amazing.

If you are interested I can send you a copy of the DBX manual.

I use mine with used amplifiers and they all run cold (not even warm!) because they never get much above idle as they each are handling only specific frequencies and you don't use the power sucking, passive X-over to screw up the signal.

Regards

Mac.

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 6:16 am 
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Very interesting. I was wondering about pro gear for this kind of thing, as it seems like it would be right up that alley, so to speak. Can I assume that this would allow one to play around with different drivers and so on (with properly tuned cabinets for each driver)?

This kind of active setup definitely doesn't sound 'user friendly,' so I can see why it might not have great appeal in the larger market. Does it have much of a learning curve?

Finally, would active or powered studio monitors have an active crossover, or are most (if not all) still likely to have a passive crossover?

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 6:46 am 
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I am not certain but I think "powered" monitors use a single amp and a passive X-over and "active" monitors use multiple amps and an electronic X-over, I'm sure there are other forum contributors more qualified than I who know for sure.

While initially intimidating, the use and set up of the DBX units, seems almost intuitive to me now, I can dial in delay, crossover frequency, crossover type and slope, I have even sucessfully integrated ribbon tweeters with full range ported floorstanding speakers and subs, with (IMHO) excellent results.
I also acquired the RTA microphone for the DBXs RTA function and that allows me to set up either the whole system or individual L/R channels to be as flat as possible and then tailor the sound to suit my preference (essentially flat with a slight boost from 45 hz down).

Full disclosure: I also the use anthems ARC to for room eq with, in my opinion, amazing results.

It's unfortunate that you are located a considerable distance from me (I live in Oshawa) but if you are ever in the area you are welcome to come and visit to see (listen) first hand.

Regards

Mac

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 7:02 am 
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The DBX are great units, for sure, and very affordable. Even more affordable are the Behringer units, though I am not sure the quality is as high. I used a pair of their crossovers early on.
I thought it might be good at some point to try one of the DBX Driveracks, but am still wary of the DSP functionality since I'd prefer to keep everything in the analog domain.
Another issue I have with almost ALL 'pro' gear is that it is almost always using balanced connections. Most people do not run balanced systems and while you can custom make cables to connect the two, it's more hassle than it's worth to me ;)
The learning curve is quite high with any of this (especially when you start getting to the finer points involved with full DSP), and from what I've read online most people have a positive response by having a pro come in to dial in the system ;)
b

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 7:08 am 
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This topic has really caught my interest. In my mind active has always made sense. However a few things need clarification. Like anything quality makes a difference; there are decent active setups and not so decent. Lets talk dollars just on the crossover for now. What are we looking at in terms of price and features for an active crossover?


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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 7:25 am 
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Canadiansnowland wrote:
This topic has really caught my interest. In my mind active has always made sense. However a few things need clarification. Like anything quality makes a difference; there are decent active setups and not so decent. Lets talk dollars just on the crossover for now. What are we looking at in terms of price and features for an active crossover?


The choices, features and dollar amounts vary widely with your needs, so it's really very difficult to nail down. You can buy a behringer x-over for ~ $100, while an Accuphase will be several thousand $ (plus the cost of unobtanium frequency cards). One cheap-ish way to at least start is using a miniDSP to find slopes, x-over points, EQ levels, etc. Then from there you could either go with a more expensive DSP unit like the DBX, or others (I forget what the common 'audiophile' one is...)
Then, keep in mind that you need amplification for each channel, likely some sort of EQ (unless you buy one of the DSP units like the DBX) and associated cabling...
It's not really an exercise for budget-conscious people, and does take time to get it set up properly.
Byron

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 7:36 am 
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I have used or am using the DBX DriveRack 260, 4800, and 4820 as well as with the Bryston 10B and the Ashly XR-1001.

The first three are digital "DSP" crossovers/EQ; the last two are analogue crossovers without EQ.

The DriveRack 260 is extremely flexible and versatile (and the 4800/4820 even moreso), but to me the 260 imparts some digital harshness to the overall sound of the system, somewhat as you get with a budget CD player. They 4800/4820 are considerably more refined, but much more expensive as well.

After several years of experimentation with active amplification, I've moved to only using active amplification for subwoofers. At around $200 on the used market, the Ashly is a worthwhile unit, though the 24 dB/oct. slopes aren't always optimal.

It takes a lot of skill and experience to truly optimize an active system and I've learned that I just don't have that skill.

I do have two pairs of factory-made active speakers, though (Tannoy AMS-12A, Meyer Sound X-10T), and they're very impressive performers.


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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:17 am 
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O.K. So I get myself a crossover for say $500-$1000. I have an equalizer and I have QSC power amps in diminishing sizes from 500 watts down to power my bass, mid, and high. I can now retire a set of Bryston 7B sst power amps and the sound quality should be improved?


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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:20 am 
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dr.joe wrote:
It takes a lot of skill and experience to truly optimize an active system and I've learned that I just don't have that skill.

Lacking the skill needed to make something like this viable is what makes me question this kind of move as well. It might be worthwhile for someone who truly knows and understands what's going on, but it might take more time and effort than I can give for me to become that kind of person (assuming I even have the capacities needed to do well in these kinds of technical skills).

dr.joe wrote:
After several years of experimentation with active amplification, I've moved to only using active amplification for subwoofers.

So would a 'budget' active crossover, amp, and DIY passive subwoofer (I have a some spare woofers hanging around) have more potential for a novice than a 'budget' powered subwoofer (with built-in frequency adjustments, and so on), or would a novice like me be better off just buying a self-powered unit with it's own crossover built-in?

-- 18 Apr 2016 12:21 --

Canadiansnowland wrote:
O.K. So I get myself a crossover for say $500-$1000. I have an equalizer and I have QSC power amps in diminishing sizes from 500 watts down to power my bass, mid, and high. I can now retire a set of Bryston 7B sst power amps and the sound quality should be improved?

That's a good question, and straight to the point, as it were. :D

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:29 am 
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Canadiansnowland wrote:
O.K. So I get myself a crossover for say $500-$1000. I have an equalizer and I have QSC power amps in diminishing sizes from 500 watts down to power my bass, mid, and high. I can now retire a set of Bryston 7B sst power amps and the sound quality should be improved?


Well, that's a really loaded question, and one that really can only be answered by you. Sorry for the non-answer, but as in all things audio, YMMV -there is no cookie-cutter answer to this type of question...
In any case, if I were to buy speakers that were already passively crossed over I doubt I would do all the work necessary to make them active. In my case, I bought 3-way horns which were basically cobbled together with a mix of JBL and Altec drivers/horns. This pretty much necessitates an active setup since there was really no ready-made passive crossover for them, and passives get increasingly (prohibitively even) expensive to design and build as the complexity rises...
Byron

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:46 am 
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One thing about active equalization I haven't understood. What about the phase differences in the crossover areas? Many audiophile avoid tone controls and/or band octave equalizers because at the edges of the pass band the phase of the signals tend to shift. That would show up as issues in matching bass to mid, and mid to tweeter etc. Is this not a concern with active equalization?

I know that passive equalization has the same issues in spades but in the case of passive equalization you have the speaker company spending their time and their extensive (in many cases) resources testing the transition areas and paying particular attention to seamless transition.

Of course you can do the same sort of tweaking using electronic means but I would think that would not be for the average home hobbyist.

Phasing not an issue?

ROVA


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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:50 am 
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mantisory wrote:
Canadiansnowland wrote:
O.K. So I get myself a crossover for say $500-$1000. I have an equalizer and I have QSC power amps in diminishing sizes from 500 watts down to power my bass, mid, and high. I can now retire a set of Bryston 7B sst power amps and the sound quality should be improved?


Well, that's a really loaded question, and one that really can only be answered by you. Sorry for the non-answer, but as in all things audio, YMMV -there is no cookie-cutter answer to this type of question...
In any case, if I were to buy speakers that were already passively crossed over I doubt I would do all the work necessary to make them active. In my case, I bought 3-way horns which were basically cobbled together with a mix of JBL and Altec drivers/horns. This pretty much necessitates an active setup since there was really no ready-made passive crossover for them, and passives get increasingly (prohibitively even) expensive to design and build as the complexity rises...
Byron


Now you have hit on a point I really do not understand at all in regards to passive crossovers. Drivers have specs from manufacturers in terms of frequency range, highest crossover point, recommended crossover point etc... As long as the crossovers fit within these parameters why does it matter where they came from or the brand? Picking two random names why can't I take a set of three way crossovers from a set of Infinitys and use them with JBL drivers as long as everything is within recommended parameters?


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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:53 am 
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mantisory wrote:
In any case, if I were to buy speakers that were already passively crossed over I doubt I would do all the work necessary to make them active. In my case, I bought 3-way horns which were basically cobbled together with a mix of JBL and Altec drivers/horns. This pretty much necessitates an active setup since there was really no ready-made passive crossover for them, and passives get increasingly (prohibitively even) expensive to design and build as the complexity rises...
Byron

That sounds reasonable.

I have some old speakers laying around and was thinking it might be fun experimenting, for example, with a budget active crossover on something modest like a pair of Minimus 7 speakers (which might benefit from an active crossover) matched up with a set of 12" woofers from an old set of Sound Dynamics three ways (a pair of Signature Series sd45's to be precise). Kind of like a 'mad novice' Frankenspeaker if you will. :D

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 8:58 am 
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Rova wrote:
One thing about active equalization I haven't understood. What about the phase differences in the crossover areas? Many audiophile avoid tone controls and/or band octave equalizers because at the edges of the pass band the phase of the signals tend to shift. That would show up as issues in matching bass to mid, and mid to tweeter etc. Is this not a concern with active equalization?

I know that passive equalization has the same issues in spades but in the case of passive equalization you have the speaker company spending their time and their extensive (in many cases) resources testing the transition areas and paying particular attention to seamless transition.

Of course you can do the same sort of tweaking using electronic means but I would think that would not be for the average home hobbyist.

Phasing not an issue?

ROVA


To speak generally, most often active crossovers are designed to use either 24dB or 48dB slopes, thereby keeping phase coherence (L-R alignment).
Check out this article: Linkwitz-Riley filter
Byron

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 Post subject: Re: Fully active x- over
PostPosted: Mon Apr 18, 2016 9:19 am 
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Rova wrote:
One thing about active equalization I haven't understood. What about the phase differences in the crossover areas? Many audiophile avoid tone controls and/or band octave equalizers because at the edges of the pass band the phase of the signals tend to shift. That would show up as issues in matching bass to mid, and mid to tweeter etc. Is this not a concern with active equalization?

I know that passive equalization has the same issues in spades but in the case of passive equalization you have the speaker company spending their time and their extensive (in many cases) resources testing the transition areas and paying particular attention to seamless transition.

Of course you can do the same sort of tweaking using electronic means but I would think that would not be for the average home hobbyist.

Phasing not an issue?

ROVA


Yes exactly. Passive crossovers often use different order high pass and low pass filters to smooth the transition between woofer and tweeter, sometimes also inverting the tweeter to give a better response in the crossover region. Speaker drivers are also rarely flat, so the crossover is designed to smooth out the response. Baffle step correction, time alignment and lobing management are other functions of the crossover.

So to simply replace the passive crossover in a speaker with an active crossover and equalizer and expect to replicate all the things that the speaker designer did originally in the passive crossover is rather optimistic. Especially without proper measuring gear and acoustic environment. For most, it would end up being a train wreck.

But, if you do decide to experiment, be sure to add a capacitor in series with the tweeter as even the smallest DC offset from the power amp can destroy the tweeter. The capacitor should be of sufficiently large value to avoid acting as a high pass filter for the tweeter. The amp may then do funny things if it doesn't have a DC load, so best to load the output of the tweeter's amp with a resistor to avoid squeaks or howls (or worse) when powering off.


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