Active crossover conversion

I am considering upgrading my system to active. Its currently triamped so it seems foolish not to (and it would remove the contraints on my preamp needing to have three pairs of balanced outputs so I could switch to S&B transformer approach). All I would need is a pair of active crossovers - probably Bryston unless anyone has any other suggestions. I would also need suggestions for someone to carry out the work - taking out the internal crossovers and doing the room measurements. I am based in the London area. Any ideas?

 

lots of nice crossovers

http://www.marchandelec.com/xm126.html

http://www.dolphinmusic.co.uk/page/shop/flypage/product_id/3586

http://sales.concert-systems.com/sales/CEL-DMS2065.html

http://sales.concert-systems.com/sales/LAB-ACN-3C.html

http://sales.concert-systems.com/sales/KLT-DN8000.html

http://sales.concert-systems.com/sales/TAN-TDX2.html

http://sound.westhost.com/project09.htm

http://www.proaudiokit.co.uk/eShop/show_product.php?ref=1184

get researching....it will teach you loads.

 

Why not buy PMC's ready-made solution?

 

I second that.

 

Markus / Tenson - Well because I already have pmc mb2 and bryston 4b-st *2 and 7b-st *2 and it costs a fortune for the active kit. The active mb2 is £18k and I would guess I would get £10k for my current kit so its £8k to upgrade. On the other hand I can get a pair of second hand bryston crossovers for £1500. The only differences will be that the crossovers wont be tweaked by PMC (unless I pay extra) and it will have the smaller tweeter. On the brighter side I will still be using the ST amps which I prefer to the newer SST variants and it will be much cheaper. Plus I think the £18k active mb2 doesnt use the Bryston 4/7 combination.

Daryl - which are your favourite and why? Have you compared with Bryston?

 

I suppose that makes sense. I think the large tweeter is nicer, but not worth £8k!!

I would go with Bryston crossovers if I were you.

Why do you need to measure your room just for crossovers though? I'd just find out from PMC what the speakers normally crossover at and with what type of filter then mimic it on the active platform. Got to bypass the current ones though and it must be tricky to thread the wire round all that transmission line!

 

If I am fitting crossovers I might as well get it matched for the room!

I just found this: http://www.proaudiokit.co.uk/eShop/Static/PMC/PMC_MB2-A.html

Anyone know these guys?

They are offering the mb2-a for £12k. I could get this and then sell my old mb2s and the one set of amps (I might get more for selling the SST amps anyway if I still dont prefer them). How much do you reckon I would get the the mb2s and the st/sst brystons?

Anyone want to buy triamped mb2s?

 

I think you should DO IT.

The Bryston crossover is supposed to be fantastic, much better than passive.

 

I think a significant issue is whether your current (in-speaker) crossovers are "textbook" or whether they are doing any curve-shaping. If the former, then a swap to a line-level crossiver ought to be quite straightforward (and relatively easy to select a suitable item - probably off-the-shelf-or-off-darrylfunk's-list). On the other hand, if the in-speaker crossover is doing fancy things you may have a harder task to replicate what it's doing.

And on the third hand, being able to do room-tuning might limit your options even more.

Sorry, I don't have anything specific to suggest.

 

The PMC actives use Bryston crossovers - but modified - so impossible to say if they are curve shaping or not.

 

From what I have heard PMC don't do any curve shaping with their crossovers, but that is just what I have heard. Better to ask them. They do use Bryston crossovers in their active designs. My AML1's use the same circuits as a Bryston 10B.

 

Then I can switch to a transformer based pre running straight into the crossovers - cant do it now as I have three pairs of 3m cables to the power amps (which I would then run between crossover and power amps instead to keep the pre to crossover cables short - say 25cm).

Thorsten - surprised you dont have any input here!

 

I feel that Thorsen and Bio-degradable Brown trousers are a match made in Heaven :MILD:

 

I can see it now Tag team audio wrestling

 

Hi,

Sorry, pre-occupied with all sorts of stuff....

Last Time I activated a big PMC Rig we used one of the BSS digital crossovers and Cary 805 SE Amp's on the mids, swapped the tweeters for Focal TC-120Tdx and used Cary 300BLX Amp's on these, Krell KAS 150 (IIRC) X 2 for the woofers.

Given that experience and my experience with discrete analogue crossovers I would never do it analog again. A decent Digital Crossover with suitable EQ, Timealignment etc. set up and widely variable slopes gets you much further than anything analogue will do, downside, you need to be able to measure what you are doing.

But in the end you can do an impulse coherent full-rage speaker with such a setup despite using multiple drivers and non-coincident sound sources and that with flat on axis response and excellent off axis response. The different to traditional methodes (analogue, non time aligned active or passive) on the same boxes is sufficiently large to classify as "night and day".

The downside is that with a fully adjustable fully active system it is MUCH easier to completely screw up the systems sound, especially when fiddeling without measurement gear and without knowing what is being done. Attaining that knowledge takes time and effort.

Ciao T

 

I was going to suggest digital Xover to begin with but Brizonbiovizier uses an analog source so unless he splashes out a lot on multiple DAC's then it may not be what he wants.

Thorsten the BSS must have very accurate time alignment to correct differences of only 1 or 2cm. How did you go about measuring it? Did you compare bandwidth limited impulse responses and adjust the BSS by hand? How good are the DAC’s in the BSS or do they expect you to add your own?

Sorry this is Brizonbiovizier’s thread, but it is interesting stuff!

 

Hi,

Maybe, maybe not. The Studio system we did this for also used analogue inputs....

We had a Crown TEF available and used that. It took a lot of tweaking to make it "just so". In this day and age a laptop, a Behringer ECM8000 and a small mike preamp possibly with USB output for Duplex and Speakerworx should do the job as well.

In the end the "implulse" coherence was done by measuing a step and fideling with settings, then re-measuring FR (which now was of course out) and flattening that and then fixing the pulse response again. The result gave a pretty decent step response.

The BSS used at the time the top of the cirrus logic (aka Cristal) chips, two per output and a single 24/48 Cirrus input AD chip..

The current Behringer DCX2496 has better ADC & DAC but worse analogue stages and is not really compatible with domestic audio levels, but neither was the BSS.

Here a domestic system including a later version of the BSS X-Over we used.

http://www.arduman.com/aa/Sayfalar/lecleach/lecleach.htm

Given that Behringers DAC's produce 2V RMS @ full scale and can drive 600Ohm (differential) I'd be tempted to mode a DCX to have an absolutely minimal analog stage. Perhaps very small nickel core 1:1 output transformers for the designated Mid/Hi Channels and a M4 Steel cored version (for 10db more level handling) on the LF channels.

Input could be floating balanced direct coupled using an MF-Audio Preamp direct into the ADC or via updated analogue circuitry.

Anyway, just some thoughts.

Ciao T

 

Wadia - I love your little jibes, however if you could add something of technical merit at the same time that would be simply scrumptious - that is if the mere act of providing techncial assistence to me isnt totally morally repugnant . Tag team audio mud wrestling? Even I am slightly uncomfortable with where your train of thought is leading.

Thorsten - would you say that the digital EQ is less degrading in the signal path than the analogue EQ? It somehow offends my sense that total analog is best but I am open to hearing the alternatives. Especially if it offers the total coherency that tony can only dream of. I may go for the bryston crossovers first to act as a reference point and then try digital eq. What is the dcx? I would prob just go for a custom bare S&B volco as I already have a switch - as minimal an approach as possible. How much are the bss crossovers? I will probably need room treatments as well - the next move will be permanant.

Dont worry tenson your questions are entirely in keeping with this thread.

Keep it coming guys!

 

You can normally get a s/h BSS for just over the £1K mark.

 

I assume I would need 2?