Jeff, Are you sure? From everything I've read, 80Hz is a pretty safe choice because frequencies below that point are extremely difficult (if not impossible) to localize.

That said, I think Bob Stuart (of Meridian) claimed that while we can't perceive direction we can sense bass envelopment down to something like 40Hz. By 'envelopment' I mean the mono in-your-head bass vs externalized sounding bass that seems to surround you. This is probably why Lexicon's Bass Enhance processing works on frequencies below 80Hz.

Sanj

Moderately sure. I know that it's been said by many of the cognescenti of the SMR forums in the past. But no, I haven't verified the information myself.

Jeff

Jeff- Actually, with no sub you are quite correct. But if I didn't have a sub, I'd just go full range. That's what people did for years with just plain old "stereo".

Everything I have read (and heard), particularly Dolby and THX info, also says that 80 Hz and below isn't localizeable. In fact, I had a Yamaha receiver for a while with a 90 Hz crossover, and I didn't find a problem with that either. Very specific test tones tests and controlled conditions, maybe, but watching a movie with audio and visual input to the brain, I think that 80 Hz and below is pretty safe. That's why, for example, the official THX crossover setting is 80 Hz.


[This message has been edited by Kevin C Brown (edited July 15, 2003).]

Yes, and it's also why THX has often come under fire for its choice of the 80 hz crossover: many experts claim that it's too localizable and that THX should have chosen a lower crossover point.

Jeff

I think I missed the point that he didn't have subs - my mistake!

Maybe it is just a curse for me, but I can definately sense the pressure direction even below 20Hz (and I'm not just hearing harmonics or room noises). I think some of this is that I have 2 18" subs per side seperated by 22 feet, and they can really move the air with some authority.

Jeff, I think there are relatively few "experts" that claim THX should have chosen a lower crossover point. Bob Stuart, THX, Bose, Dolby, M&K and others have actually put trained ears to the test and found that it is extremely rare for people to be able localize the bottom two octaves. I got a practical demo of this when I visited the facilities of M&K Speakers a few years ago (I used to live near them in Culver City). I'll have to agree with Kevin: 80Hz is a pretty safe crossover point.

Sanj

I thought of a potential bad thing with using a crossover with no sub.

I *think* I remember Bossobass saying that the way that the 950 low passes the LFE channel, is that it applies the same crossover as the mains. So, for example, if you set the 950 up as mains = small, and then no sub, it will effectively eliminate the LFE signal. If you say mains = large and no sub, it will reroute the LFE to the mains. I guess the question would be: potential poor quality bass (distorted) vs no bass, in terms of the LFE channel.

I have the Axiom M80Tis whose Freq Resp is +/-3dB (Hz) 34-22K and +3dB/-9dB (Hz) 25-22K and I cross them over at 80 Hz to my home built Shiva sonosub and it sounds best at this crossover. It's difficult to explain. I don't have the technical lingo. I just trust my ears. At 40 or 60, the bass didn't have that distinct punch, but at 80 there is magic! And my Shiva sonosub rocks. I have it pushed by 400 watts mono. The other 5 speakers are driven by my 770.

"With a 24 dB/octave crossover network a good rule of thumb is to set the crossover point at least 1/2 to 1 octave away from the cutoff frequency of the speaker. Thus a satellite with a cutoff of 5o Hz at the low end that is used with a subwoofer requires a crossover frequency of 75-100 Hz. The subwoofer should then have a range extending 1/2 to 1 octave above the crossover frequency..." Dr. Phil (Marchand)

The variable in HT setups is that the HP is 12 dB/octave to mate with a sealed satellite which has a natural rolloff of 12 dB/octave. The combination sums to a 24 dB/octave slope to mate with the LP of 24 dB/octave applied to the sub.

If your satellites are vented (which have a natural rolloff of 24 dB/octave) the 12 dB/octave HP sums to result in a 36 dB/octave slope, while the LP remains 24 dB/ octave. This means that they do not sum to unity at the crossover point.

Add to this that the 'Q' of the HP is not known nor adjustable and can effect the response of the satellite at crossover, usually by causing a hump or a dip at the crossover point.

Conclusion: Pre-pros should have a selectable slope in the selectable crossover point menu because the majority of satellites are vented. The 'Q' of the HP should be adjustable. Speaker manufacturers should include a recommended HP filter 'Q' value in their specs.

In answering the original question of this thread, I agree with the venerable Gonk. There should be no HP applied to the mains, which should be set to 'large' and sub to 'no' so that the LFE is re-routed to the mains. Adding a HP to the mains causes the rolloff to be much sharper and possibly introduces a damping ('Q') problem at the HP point.

A thought on the 950's bass being less 'tight' than the HK's: I have a 'no dot' version 950 and have always thought the bass to sound very tube-like. Though I almost never listen to stereo CDs, the bass in SACD and movie formats through the 950 is excellent. Given the above posts, some tweaking to optimize your setup's low freqs is no doubt necessary to reach "sonic nirvana", so don't give up...I assure you the 950 will deliver it's part of the equation.