ATC SCM150 Amp and Preamp recommendations

I am the US importer.  The actives will outperform the passives every time, not due to amplifier issues but do to control of phase.  There is no way to control phase in a passive crossover.  This a huge performance issue very few talk about. 

In a passive, a well built crossover has a TON of wire in between amplifier and drivers.  There could be hundreds of feet, especially in air core inductors.  I don't see in any scenario how that could be an improvement over hooking the amp directly to the driver with 1 foot of wire.

Next the ability to calibrate each amp precisely to the driver itself (efficiency of a completed drive unit can vary in the very best of the best manufacturing from 1/4 to 1/2 dB.  1/4 to 1/2 dB across an entire band is very audible.   .    

Next is the ability to sustain large bass dynamics while not affecting the top end HF amp or Midrange amp in any way.  A full range amp cannot do this, as the bass running the amp out of power is well understood.  The way most of us get around the obvious there is through massive OVER power delivered at the speakers, accounting for the loss of power and reduction of dampening factor down as little as 10 feet of cable.  Linear analog amps seem better at this as they have larger reserves inside a power supply.  The why ATC's own amps are class A/B and have a large linear power supply.

Maybe look at trying an ATC P2, which is 300W /channel as a first step.  that will tell you if it's enough and you need the Titan.  Keep in mind a 800w amp vs 300w amp is only about 3-4dB of average level increase.  At 110dB SPL, 3 db more SPL is a small amount.  DO the math on the 150s and see how loud 300W will be.  

Active ATC 150s will play at around 115dB or so long term, depending on dynamic range of the source.  I cannot listen that loud and I ve never run into a hi fi customer that does.  Most people cannot get much over 105dB SPL before they start freaking out.  The 95dB SPL is LOUD, and the 115dB SPL capability (20dB of reserve) is for peaks.     

Is this helpful?  I would think a 300W amp on passive 150s would make one very happy and allow some money to buy a great preamp and a great DAC, Streamer etc.

Brad

Lone Mountain Audio (ATC Hi FI USA)

TransAudio Group (ATC PRO USA) 

@ei001h 

You’ve put forth the only argument that wins.  It for this reason that we still build passives as many in the hi fi hobby love the ability to "craft their own" so to speak.  The technical virtues of "the lowest distortion way" dont always win as we can easily see with those that love tubes.

My experience is that when active is chosen, it does not diminsh this "craft your own" part of the hobby and actually strengthens it.   Once the distortion of so much wire is removed, and phase is now linear, the items IN FRONT of the actives take on new meaning and greater dimensionality.  Cables, turntables, line level cables, streamers all become more different, more obvious than before. I ahve found that changes in front of the actives are now even more significant than before.

All that being said what most people focus on is tone, how a trumpet sounds, a piano, a vocal; in this the active and passive are remarkably similar.  the times I have done this comparison, many in the room cannot tell the difference or just take a wild guess.  What does affect choice that is easy to miss is tiny differences in level, comparing two things; this can make a dramatic impact in perception of which one sounds more full or warmer.  Slight differences in level appear as better bass or less bass, more treble or less (thank you Fletcher Munson curve). 

The source material can also influence this choice as many records or albums have more or less bass or more or less treble than another record.  IF I play Led Zeppelin you’ll be convinced there is less bass  (these LZ records are notorius for no bass).  If I play Patricia Barber you will be convinced there is more bass and better midrange (I know the engineer who records her and he uses very expensive hand made tube microphones i sold him many years ago that have tremendouos definition) . 

The casual or rough demos we expereince in trade shows or at someones’s house can really lead you astray, as many factors influencing perception are hidden: look no further than continuously variable gain controls on preamps which are impossible to match or repeat from one source to the other.  A tiny 1 dB level difference will make you 100% certain one of the two things has more bass or treble.   Often we attribute differences that we hear to something other than level as level alone is tough to hear. 

For example, conviction that the 800W amp vs the 300W amp is signitificant   enough to hear the differences in dynamic range may not be true depending on just two factors: the efficiency of the speaker you are comparing them on and the "sound" of the amp itself on that particular pair of loudspeakers.  I think those two factors could sway your choice one way or the other, regardless of which one has the larger power output.  SO if you are actually listening at 85dB SPL on a 90ddB 1w/1m speaker, it may not show that a 800W amp as better than a 300W amp dynamically.  O a 80dB 1w/1m speaker, it may show this easily. 

Brad      

@ei001h 

Sounds like your journey ended up in the right place.  Ultimately the thing that makes ATC the MOST different is the low distortion drivers.  This is is something both passive ad active users can appreciate when it helps them hear things they otherwise wouldn't.   

Funny how distortion in drivers appears to our ears: not necessarily as a change in tone or audible distortion, but as masking, the veil obscurring information.  Remove that and a world opens up!

The only negative to low distortion is the recods you loved for the music can sometimes soumnd rather awful.  I remember the first time I heard Genesis "Selling England By the Pound" on a pair of ATCs and I was quite disappointed: NO bass at all, almost like it had been rolled off at 400 Hz!  This was likely caused by the mix monitors or mastering monitors having too much bass in the studio and therefore the engineers thought they had ait rght when they didn't.  This was common until they finally realized that a flat speaker or one with less bass was best to mix on.  Getting your monitors right is important to make sure that your fans get to ehar what they expect. 

Brad   

@onhwy61 

ATC actually did make an active crossover years ago, before they made the "amp packs" with everything built in.  I’ve asked about making another one over the years, but calibrating a system properly is not easy.  I use an Audio Precision here in our shop (10K piece of test equiipment) plus an expensive calibration microphone and a treated room; this is almost impossible at home.    This calibration is critical to the entire active idea.  Asking end users to do this at home sucessfully sounds like a lot of complaint phone calls coming in to me!  Its a complex process to correctly calibrate and check your work, especially when trying to stereo match a pair of speakers in different locations in the room.  A 1/2dB level difference across an entire band is quite audible.  Its nearly impossible to measure correctly in a living room with all the irregular surfaces and 1st reflections., windows, etc.  Using a DIRAC or REW or other such method makes it very diffeicult as all these systems look at a single point in space so it doesn apply to the entire room.  Trinnov is better, a lot of advantages in that mic they developed.     

Brad