Analogue and digital crossovers for active conversion.

sastusbulbas

sastusbulbas

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Hi guys,

What crossovers are recommended for active conversion of speakers? Interested in views of analogue or digital, for instance Bryston or DEQX as examples?

I have a pair of Kef R107 which I sometimes think of modding, but they use a Kube for EQ of the bass, and mid to some point is also EQ'd.

What sort of costs would I be looking at, and what potential problems?

Any links to UK retailers and other such info would be appreciated.

Cheers,
Steve
 
Hi
I have been using a DBX Driverack PA. If i was buying again I would consider the next model up as when you power it up it puts out a DC signal for a moment, so power amp needs to be off.
Having said that, I am very pleased with it. I use it to seperate the bass out from the valve amp and main speakers to a sub.
The question comes down to voicing if you are using room equalisation as i suspect that designers no not always engineer a flat frequency response.
I was messing about with Linn Tukans and Lowther Accousta, I swapped the Linns for the Lowther back after requests from my family but left the DBX crossover EQ's for the Tukan. The Lowthers sound better than when I set up the crossover specify for the Lowthers, hey ho....
So, yes I am a big fan of the digital crossover but i am only using it at a single bass frequency. The RITA room equilisation is a huge plus for producing a balanced even bass.
Getting the right sound balance is a personal preference.

Anyone have any info on target frequency curves in room for full range domestic monitors? Flat bass down to 20hz seems to be rather heavy on most non acoustic instrument music and rather unfriendly to any one else in the house...

Ta
 
No one has really replied because it is not really an easy task to 'convert' existing passive speakers to active. Crossovers are very carefully designed things so you can not just plonk an active xover in and expect results. That is not to say it isn't possible, but you really need to know your onions to do it right.

Active digital xovers are really for people who want to make their own speakers, or for use in concert venue PA systems.

If you want active speakers, buy some that are already that way.
 
Hi Tenson,

Yes I was under that impression. The Kef R107 speaker has a 24dB/octave crossover frequencies of 160Hz and 2.5kHz and as far as I am aware, crossover and drivers are in phase as the cabinet is phase aligned.

For some reason I wondered if the likes of a Bryston or DEQX would work as straight crossover point replacements but of course the Kube EQ's bass and adjusts the mid slightly, and offers adjustable LF cut-off/extension, gives you the option to adjust Q from 0.3 to 0.7 and gives the option of -/+ 3db shelf adjustment below 160Hz.

As this is RCA only and my set up is fully balanced it means compromise or tape loops with connection, there was a professional Kube available, but it was less adjustable, and the Meridian 602? pre amp also had Kube EQ in the digital domain.

If such EQ can be applied with an active crossover network I thought such an endeavour could be rather rewarding.

Though I guess something like DEQX or Tact 2.2x could replace the Kube?

Some of the details of the 107 are I believe roughly detailed in the Stereophile review.

Probably just pipe dreams I guess, Bryston crossovers with at some point a 2Bsst/3Bsst/4Bsst combination driving Kef R107 actively :)

Steve
 
The Behringer DCX2496 will do everything you need. It's also balanced.

The problem is even if the drivers are perfectly phase aligned, the drivers frequency response may not be 100% flat across the xover frequency. When you make an xover you need the combination of electrical filter and the driver itself to produce the target roll off. If the driver already has some deviations from flat then a text-book 1st/2nd/3rd/4th order crossover won't work right anymore.

You need to measure what you are doing, and you need to understand it.

You could use some audio transformers to convert the balanced signal to single ended just before the Kube, and then again coming out of the Kube back to balanced. I could put some of the ones I use in my Behringer mods in a nice little box if you are interested, just let me know.
 
Hi
With the dbx you choose a 3 driver program from the front screen.
For each driver choose the lower and upper crossover point, filter type and slope. 24db/octave - Linkwitz-Riley, are what i go for.
http://www.rane.com/note160.html
Then connect measuring microphone from listening position into dbx unit. Select RTA, required resolution, turn up volume for pink noise to listening level and then the unit takes a couple of minutes shifting volume to give flat frequency response. Then if you wish you select one of the post freq. curves and adjust the equalization to a curve you require, perhaps a little boost around 150 hz and a dip after 30 hz. §
I presume the Behringer DCX2496 is very simular but costs less.
ta
 
Pretty much except it doesn't try and set the volume levels itself or have preset EQ curves. You do it yourself, which to be honest I prefer. Auto systems never get it right anyway. I hated the TacT for that - don't tell me to set a target curve, just give me direct control! :D
 
BTW - I've got a DEQX PDC2.6 for sale. Its an amazing piece of kit and easy to use, and the manual is very good too. It can do various crossover types including up to 300db slope.

Worked wonderfully with a pair of Wilmslow standmounts without their own crossover, but have since changed speakers.

It just takes trial and error to get it right, actually there is no "right" just what works for your ears - so never mind the naysayers.
 

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