Upgrading from passive to active

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anon_bb

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Well tonight I take delivery of a second hand active PMC MB2-A-XBD (my current pmc mb2 passive is up for sale in the ads section along with my 4 bryston amps if anyone is interested! I am prepared to split!). I will probably also sell the active xbd2 subwoofers if anyone is interested - it stands 12 feet high else!

As I am swapping a triamped passive system for an essentially equivalent active system I will post my findings re: room adjustments and overall difference in sound of passive v active.

I plan to put the crossovers under the pre and run long cables between crossover and amps. This will enable me to try out a passive or tvc pre as I will only have to drive a single 0.5m cable instead of 3 pairs of balanced 3m cables as I did for the tri-amp setup (using a custom built pre). If anyone has an Audio Synthesis 8m passive pre I can try out I would be very grateful!
 
I'm interested to know how different you find the change. I guess my gut instincts are that an active system is more convenient for studio use, but perhaps compromised compared to a top quality choice of amps with passive speakers.
 
The amps are bryston sst modded by pmc - they are not compromised studio amps. You are right though a good passive with a single good amp will beat an active with bad amps. Going active with good amps is very expensive. The mb2 system new would be over 20 grand.
 
brizonbiovizier said:
The amps are bryston sst modded by pmc - they are not compromised studio amps.
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I didnt say they were compromised studio amps. Please reread.

My point being my understanding is that having amps onboard with the speakers is somewhat of a compromise, but is ideal for studio installations. It also means you cant change the amps should you wish to do so. I'm not suggesting the amps which accompany the actives are compromised amps.
 
Hi,

Ah I see what you mean now, I thought you meant the design of the amps not the location. Your comment about the location is wrong so I misunderstood. In the active mb2 the amps and crossovers are external to the speakers and not onboard so you can change either or both.

Its not like the atc scm100a where its all one unit. I agree if you cant chop and change its too limiting.

Will let you know how it goes!

Nick.
 
Hang on, if its all separate stuff, what is the difference between this and simply adding an active Xover to your other system and bypassing the passive ones?
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Cost. Plus the customised amps and crossover. Plus the xbd. Plus the better tweeter. Plus lack of hacking. ;)
 
BBV,

Interested how you get on with this. I went from a Passive Linn system to an active tri-amped system a few years ago, not quite in the same price category as the PMC/Bryston setup, but I was surprised at how better the Linn Keilidhs improved.

The first thing I noticed was how much deeper the bass went, much tighter as well, also the Keilidhs started to actual image - something they never did before.

Certainly with the Linn system the cards that get placed in amps have settings which my dealer used to compensate for the room and this also made a difference from the passive setup.
 
What alternative amps and crossovers would you recommend greg?

Griffo - Geez my front room is full of 6 fridge sized speaker boxes, 8 Bryston amps and a spiders web of cable plus assorted stands. What a mess! I will report back on my findings - tenson is coming on saturday with a django and some room measurement equipment!
 
brizonbiovizier said:
What alternative amps and crossovers would you recommend greg?
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I dont recommend any. I just like the fact that should you prefer an alternative to Bryston at any stage, you at least have the option. My point above is an uncontentious one, just that my understanding of active pro systems was to provide a single solution and a convenient one for installations, rather than an active solution being so because it is a better concept. Just my impressions, but not based on any strong opinion.
 
I am considering the White Noise Audio or possibly the Borbely designs for amps and crossover in the longer term. I might also replace the tweeter on the active as I think it still lags behind the other two drivers. However I think for the time being I can get greater improvements elsewhere in the system. I have heard an airtangent on my deck and it was a startling improvement so I think that will be the next step.
 
Tenson came over today and helped me setup the system with my brother and then do the room measurements, crossover tweaking etc. We then tested out active eq using his behringer and he then let me have a listen to his django tvc pre. Many thanks to him for his help - hes a very knowledgeable chap and a gentleman to boot! If anyone needs his professional help for room eq or room treatments I wouldnt hesitate to recommend him.

Going active has made a big difference - probably the biggest single upgrade I have ever heard in my system. Adding in the django then took it to a whole new level - it seems I am going in the right direction by changing the WNA active pre to a tvc or resistive passive. I was also quite impressed by using the digital eq - it sorted out the bass a treat and made it all sound more even, tight and musical. When I move to a permanant residence I plan to employ Tenson to provide the room treatments.

Next time around I plan to try the eq in the analog chain as well as compare the django to a resistive passive pre. Sadly my phono died early on the proceedings so we werent able to test the former. If the degradation is outweighed by the benefits then I will use digital eq between pre and crossover. If not then I will rely on room treatments and then use digital eq for the digital chain only to provide further fine tuning.

Hopefully tenson will add his own findings and write up a (generous?) appraisal of my system.
 
Hi,

brizonbiovizier said:
If the degradation is outweighed by the benefits then I will use digital eq between pre and crossover.
Click to expand...

Hint, the Converters (ADC & DAC) in the Behringer DEQ are as good as any you find in Pro Gear. The DSP Chips are equally "standard".

Where the Behringer falls down is the Powersupply and analog stages.

I am waiting for prototypes of transformers I designed for interfacing the Converters directly to line level signals with a full scale level of around 3.5V RMS. When they work out they will become generally available.

The actual Digital circuitry in the DEQ2496 only needs one really good 5V supply if you subtract the active analogue stages, making an internal or external linear supply of 5V that is really good is not THAT difficult.

I would expect the result to be sufficiently transparent to be used between a good preamp and amplifier with the benefits seriously outweighting the drawbacks.

OF COURSE, if you bother going this route, why not ditch that analog crossover for a digital one, using the same principle modifications. Such a digital X-Over betters in my experience IN PRACTICAL OPERATION analog methodes by huuge degrees because it offers:

1) Driver Time Alignment in software, so any speaker can be made time coherent (if only for a fairly narrowly defined area).

2) "Perfect" X-Over slopes, using analog methodes invaribly is exposed to tolerance issues which means a real active x-overs is allways off the real curves needed and it gets worse as X-Over slopes increase in steepness. Hence drive units do not integrate as intended, a Digital X-Over always "gets it right".

3) Using a digital x-over and tailoring the dive unit response can be used to eliminate any dive unit sample variations and thus make sure that L/R channels match perfectly.

Give it a thought.

Ciao T
 
Yes you could put the input transformers on the DEQ2496 input, room correct, then send its output digitally to the DCX Xover to be converted to analog and out through step up transformers.

I am going to go a stage further and have the DEQ2496 and DCX before the preamp so I take digital in and then out directly from the DCX's DAC chips to a 4 channel TVC pre-amp.

I will write my thoughts about Saturday when I have more time.
 

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