Subwoofer crossovers

Hi Edorr
Yes the crossover applies to the mains and a lot of speaker manufacturers (like ATC) dislike the idea. Others do it out of compliance if they plan to sell a lot of small 5.1 systems in post-the customers (in this case post production engineers) need to hear exactly what the 5.1 mix will sound like.

Brad

The posts in this thread suggest you folks are knowledgable about bass management. It seems as though SACD discs output as DSD from my Sony XA5400ES or Oppo BDP-93 to my Cary Cinema 11a lack bass management. The subs are not invoked. OTOH, HDCD discs from the BDP-93 do invoke the subs. I read one of Kal Rubinson's remarks to suggest DSD might not carry bass management information. Do I need to output LPCM to get the subs to fire? Is it endemic to DSD or is it a problem with the Cinema 11a? I'm trying to understand this.

db

In case it's relevant to my previous post, the sub output from the Cinema 11a goes through a Velodyne SMS-1 to a pair of HGS-15s using XLR connectors. The 11a has movie and music modes. I use 80 Hz crossover to the mains for movies and 60 Hz or none for music.

db

You cannot apply bass management in either the Oppo or the Cary when playing in DSD Direct mode. However, when you play a 5.1 SACD you should still get information on your subs (this is the .1 channel), because this information is present on your source and does not require bass management to reproduce. When playing a stereo SACD (or a 4.0 or 5.0 SACD), you will not get any bass on the sub and need to convert to PCM if you want to use the subs. Try both modes and see if the benefits of bass management outweigh the loss in resolution of converting to DSD. Some have reporting no such loss exists, in which case PCM conversion is always preferable. To my ears the loss is substantial. IF you play a 5.1 SACD and you get no output on the subs something is wrong in your setup.

I'll take the other side of Brad's argument.

Unless you're using full-range room EQ (ala Audyssey), the most audible of the passive-treatment resistive, room induced, problems occur between +/- 60hz and +/- 110hz in most rooms (IME, anyway). Bassbusters are great, but their effectiveness starts to diminish below 100hz, and is generally, entirely gone by +/- 70hz, IME.

If you're using subs, you can address these thorny problems with careful placement of the subs and/or deciated subwoofer EQ (SVS or Velodyne). Either way, the subs need to be the source of the output in this mid/upper bass range if they're going to the tool used to fix the problem. This means the subs need to roll off fairly high: somewhere north of 75hz in every room I've set up.

This usually makes a good "hand-off" to unfiltered mains impossible, unless the mains have no bass at all. Something like the Sunfire Ribbon Monitor might work, but most high-end mains have sufficient bass to relegate the sub-woofer to deepest bass only. You can't run the subs high enough to fix the nasty problem that subs are best suited to fix - unless you low cut the main speakers.

That's a mistake IMO. I know many, many folks prefer to eliminate an active x-over, but at 80hz, I find that even a modest cost unit like the NHT x-2 is very, very hard to detect. Of course, this "undetectability" depends both on the system in question and the listener in question, but I've A/B'd the X-2 in some very high end chains and, with suitable program material (i.e. no bass at all), I can't hear the difference. Also, of course, YMMV, on that one.

It's entirely possible that a truly crappy low cut for the mains like that in the Velodyne SMS-1 may be a different story. I'd agree that decent active x-over is important. But, shy of that, I believe that any deterioration introduced by a decent active x-over is (IMHO) likely to be swamped by the benefits of crossing the subs out higher in frequency than is usually possible when the mains are run full-range.

A lot of people note that there are also benefits to relieving certain mains of the heavy lifting in the mid/upper bass, as well, but - IMO- that's just a little icing on the cake.

Just the other side of the coin.

Marty