I realize that the reponses to this question are going to be entirely subject to personal preference, hardware, room environmentals, etc. But I'm curious, what are your speaker settings?

I use a Rotel RB-1075 amp and I have B&W DM604S3 fronts, an LCR600 center, DM302 surrounds, and an old (kinda cruddy) Acoustic Research sub. My room is 12' wide and 26' long with my listening area roughly 11' from the front (shorter) wall. After much tinkering, I have found that the following settings work best for me:

All Speakers set to "Small"
Front X-Over @ 40hz
Center X-Over @ 60hz
Sur. X-Over @ 80hz

Why you don't use "Large"?

You should bi-amp your center; it doesn't look very strong. If your sub has high level input/output you can use it to bi-amp.

Also, you better cross center sub higher to avoid center hollow sound. Mid-bass is critical in center channel. Just my suggestion.

Speaker crossover settings are generally most closely tied to the speaker's range - how low a frequency the speakers can reproduce. With that in mind, I'm including the -3dB point for each channel.

All speakers set to "small"
mains: 60Hz (-3dB point: 30Hz)
center: 80Hz (-3dB point: 42Hz)
surrounds: 80Hz (-3dB point: 60Hz for side surrounds, 50Hz for rear surrounds)
six-channel analog bass management "on"

Your settings seem pretty reasonable for the speakers you're using. Have you tried going up one notch on some of your speakers (60Hz for the mains, 80Hz for center)? I've known several folks around here to suggest taking the -3dB point and moving up an octave (in other words, doubling that number) to get the crossover point, and while I haven't used that advise in every case I have found it to be useful for best integrating my mains and center to my subwoofer (an LFM-1).

I've gone back and forth with different settings and have to agree with Gonk. Raising the crossovers seems to strenghen the bass response. If you have a good/accurate sub, let it produce the lower base. The important thing to remember is that a crossover is a slope, not a fixed value. Setting a speaker to it's -3db point allows a significant amount of lower frequency data to be sent to that speaker.

Still, it seems to be a waste to have full range speakers sitting there with high crossovers.

Let your ears be the judge!

John

Sraber

I forgot to tell you one aspect of not using redirected bass circuitry is that internal processor will cut bass from the channel you set it to “small” and sent them to subwoofer, resulting a mono bass or “loss of bass”. That kind of bass usually sounds not very smooth compared to stereo full range bass. Since bass sounds have certain amount of directionality it is best not to cut them, if possible. Even if you are using small drivers (6.5 inch) you can still sent them full range signal (Large). Most of small drivers will start to roll off when they reached their low frequency limit; so don’t worry about damaging speakers.

You should always bi or tri amplified your front LCR channel with larger heavy duty drivers and an active crossover (the best and cleanest method, if allowed) along with full range signal to archive higher impact. Passive bi-amping with another powered large driver is more cost effective and will also improve the sound quality, but you may need some additional signal processing and some fine tuning. The redirected bass circuitry is more flexible, but at the expense of sound quality.

Interesting comments, theendofday. I haven't heard of the redirected "mono" bass being referred to as a "loss of bass" before - in fact, the reasoning behind bass management is that speakers (even tower speakers) can't reproduce low frequency material effectively (the DM604's output will have dropped 3dB - a halving of the actual volume - by the time a signal is at 39Hz). A subwoofer with a -3dB point that is 10Hz, 15Hz, or 20Hz (or more) lower than that will provide more bass than the speaker alone. With a single subwoofer, you will get a mono signal, but the general concensus I've always seen is that bass is not generally directional until you get above 80Hz at least.

Bi-amping or tri-amping with active crossovers is certainly an ideal design approach. Actually doing it, however, is often prohibitively difficult. Soundhound here in our forum has done it, and built his own crossovers to do so, but the know-how to modify a commercially-made speaker in this way is significant. With DIY speakers (such as jhenderson is doing at the moment ), it is a different matter, of course, since in many cases the DIY speaker builder is dealing with crossover circuits anyway. The benefits of passive bi-amping alone for a speaker are a source of much debate, and the Rotel amp in sraber's system currently is pretty hefty, such that bi-amping may not add much or any benefit. I get the impression, however, that when you say "passive bi-amping with another powered large driver" you are referring to stereo subwoofers. That is an approach that many people use and enjoy, and one that can be implemented with commerciall available equipment. For example, setting the mains to large and placing an Outlaw ICBM or a pair of Paradigm X-30 crossovers between pre-amp and amp for both of those channels, using the subwoofer output of the analog crossover to drive the stereo subs. Of course, you still need to add a pair of subs to the equation, as well, so while all of the equipment is available off the shelf, the overall setup won't come cheap.

Gonk

Actually, the situation is a bit more complicated for “loss of bass”. When you redirect the bass to the sub, the bass management circuitry will simply mix the stereo bass signal together to create a mono sum and there are some problems with this approach. First, the center-panned portion in the stereo will be over-emphasized in the mono-sum signal. Second, any stereo bass effect in the stereo mix will be completely lost due to cancellation in the summing process. As I said, bass sounds have certain amount of directionality (especially in stereo signal) it is best not to cut them and redirect them to other speakers. If you really require extremely low frequency (below 30HZ) for your system I would recommend you to filter that small portion of frequency out from stereo and run it at a dedicated LFE sub; separate that low frequency with rest of full range channels untouched. I found not too many recordings contain frequency that low and it is not necessary to hear that low unless you are testing the special bass disk. For me, mid-bass is the most important. Maintaining highly correlated low bass in the stereo signal not only affords subjective advantages such as higher bass impact, but also technical advantages like higher bass efficiency. I usually buy raw drivers to assemble my own speakers. Even though Bi-amp or Tri-amp is not very cost effective; the performance is excellent and worth it. With active crossover, you can cross any frequency depend on driver’s characteristics with fine-tuning. I found if you really want truly “full-range” with dynamic and impact, bi or tri with larger drivers is a necessity. ICBM or Paradigm X-30 crossover is suitable for subwoofer.

Theendofday is absolutely right about the cancellation that takes place in the bass summing process that takes place with bass management. This could accurately be described as a loss of bass integrity.

Anytime that two (or more) audio signals (or any AC signals for that matter) of any phase other than absolutely in-phase (zero degrees) are summed, there will be peaks and dips created depending on the phase between the two signals - this is unavoidable in any summing process, and is just textbook engineering. Signals that are of equal amplitude and in-phase in both channels will receive a 3db power boost (6db voltage boost) over bass signals that appear only on one channel. Bass that is between these two extremes will have boosts between 0db and 3db (0db and 6db voltage).

The situation gets far more complex (and worse) when considering 5 active channels being summed in the bass as takes place in a home theater using bass management.

This is one of bass management's dirty little secrets that doesn't get acknowledged by the manufacturers or by any magazines.

Bass management is a compromise solution that allows the use of smaller than actual full range speakers in a home situation. Smaller speakers became popular with the advent of home theater since it was obvious that the vast majority of people (read-wives) would not allow 5 speakers in the (her) living room with 15" woofers. The cost of such large speakers was also a major consideration. Therefore speakers with 6" and below woofers became the norm, and woofers of this size cannot produce real bass below 50Hz or so, and many have difficulty even at that frequency.

A home theater with 5 speakers utilizing 15" woofers for the mains and surrounds, and thus real response to 20-30Hz, would have no need for bass management and could use a subwoofer for the same purpose it's used in a movie theater or on a film dubbing stage: for the LFE channel only (which is a true mono channel and therefore has no phase cancellation issues).

Ah, OK, that makes sense. I see now what you meant by "loss of bass."

And I think a lot of us tend to forget what the trade-offs are when it comes to bass management - I know I all too often do. Budget, room configuration, and know-how (among other things) may force a lot of us to accept those trade-offs, but it's still good to keep all the facts in mind. Good points from both of you. Thanks!

Gonk and Others,
Thanks very much for your replies. I have to admit, much of what was said was a bit over my head. Is there anyway that with a SPL meter and a test DVD (I have AVIA), that I can tell if I really am missing midrange or mid-bass as was pointed out earlier in this thread?


Thanks,
Scott