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

No. To accurately test the response of your system, you need either RTA software and a calibrated micrphone, or a test CD or DVD with warble tones or 1/3rd octave band limited pink noise in conjunction with your SPL meter. I know of no such CDs or DVDs, but somebody else might on the forum.

Test CDs or DVDs with steady state fixed frequencies are absolutely useless in determining the frequency response of speakers since the room's acoustics will swamp any valid reading of the actual speaker.

There are moments, that happen with pleasant regularity in this Saloon, where many of the seasoned Gunslingers just hit it out of the park.

This discussion sheds light on a often oversimplified subject, and provides all the readers here a way to look at their own systems, and understand why some of the Gunslingers choose other means to the end.

The use of stereo subwoofers, and the benefits of a separate LFE channel have been suggested as significant system enhancements many times. This discussion seems to support those arguments. In response to this bass management problem, Soundhound's stereo subwoofer solution could be employed in many of our systems, even if we have passive crossovers. My own system is similar to his in this respect.

The use of a separate sub for the LFE channel seems to make a lot of sense to me also. According to some Gunslingers, the majority of multi-channel audio recordings use the LFE channel as a bass booster, which creates double bass issues that might even be made worse yet with the bass management limitations discussed in this tread.

Thank you all for your contributions...

Allan

P.S.: The Stereophile Test Disk No. 3 has warble tones at 1/3 octave centers that I have used with some success, but a RTA is the best way to go. If you have a friend with the equipment and software, it can be done pretty easily. The next question is what do you do with the information...

Scott

All you need to do is listen by ear; tune everything to the way you want hear. If your current system sounds good to you, then it is the best and leaves it that way.

Friendly reminder: while the behavior of the acoustic combination of signals is somewhat different than the combining of electrical signals, mostly due to the effect of an acoustic environment and speaker placement, even if one manages to keep all bass individually isolated in several channels and reproduce them independently, loss and/or boost, similar to electrical combination of signals, will occur in the listening environment as the sound waves interact.

Some would say that environmental acoustic interaction is better than electrical, somehow more as ‘intended.’ I suppose that would depend on how the method of recording and/or mixing were done as a means of producing something ‘intended.’ Unless it were for a specific purpose, engineers generally seek to keep signals in phase on various tracks. If there is some small drift in phase, the lower the frequency, the less impact a slight phase shift has. The electrical combination of bass signals is not automatically a bad thing, especially if it allows access to the reproduction of low frequencies in a room via one or more subwoofers that would have otherwise been left unheard.

If one were listening via headphones, there would be minimal combination of signals prior to interaction/interpretation in the brain, and for a ‘live’ stereo/binaural recording, this might be close to ‘intended’ in the ears, even if it leaves out the feeling of tactile bass.

Personally, I like aural and tactile bass together.

Three speakers utilizing three 15” inch woofers with 97 DB output is lethal enough, man..... Surround and LFE won’t be needed. (for real.....)

I knew somebody would bring up this point, and in fact I was going to cover it in my original post on the subject, but here goes.......

Yes, there is in-room acoustic cancellation to some degree with stereo subwoofers, but if you read the lengthy post I wrote on the subject of stereo subwoofers, I mentioned that this acoustic mixing in the bass is exactly what happens in real life acousitic events. That's the whole point!

Bass is not mixed to mono and squirted through a single source in real life music heard in real acoustic spaces, but is all around you in random phase. Multiple subwoofers preserve this random phase relationship in the listening room, as picked up by the recording microphones.

When this acoustic mixing of multi-channel (or stereo) bass takes place in the listening room, it is sensed as enhanced performance space ambience due to the natural acoustic mixing of low frequencies, just as in the original performance space - this does not take place with mono summed bass which only contains peaks and dips with no directional ambience information being conveyed to the listener.

Bass phase interaction in the listening room matters, just like it matters with higher frequencies. Natural acousitic mixing of low frequencies makes recordings sound more live rather than "canned".

As far as recording engineers keeping bass mostly mono, well, this was a huge issue in the days of LP records which could not tolerate out-of-polarity bass signals in the grooves. This condition would result in vertical modulation of the groove which could cause the stylus to leave the groove and skip to ajacent ones. Great pains were thus taken to record with bass as mono as possible. As a further precaution, all LPs were cut with the bass frequencies below around 300Hz blended to mono before being cut into the master laquer record.

This is not an issue with digital delivery media and bass can be as random phase as any other signal.

In my work on scoring stages where music is recorded (and in studios before that), I know personally that engineers now days give little thought to keeping bass mono. It is just not a concern anymore. In the recording of popular music, bass will tend to be more mono simply because most insturments (including the sole electric bass) are almost always recorded with single microphones, onto single tracks on (increasingly) digital audio workstations.

Recordings (like the organ demo CD I recently circulated) that were recorded with spaced omni-directional microphones contain large amounts of random phase bass information, which contains the low frequency ambience that all real world rooms posess, in addition to the bass directionality from low frequency instruments distributed in different parts of the recording stage (bass drum, contra-bass, timpani, organ pipes etc).

Preserving these low frequency cues in playback in the listening room adds to the sense of hearing a "live" acoustic event.

This dimention is totally lost when bass is summed in purely electronic form and sent to a mono speaker as it is with bass management.

I guess I didn’t have the time to express all my thoughts either, but I think within the wording I used in my last posting I did leave room for everything SH just said to be absolutely true. Specifically:

I run stereo subwoofers, using an ICBM between pre/pro and amp, with reasons as SH states. But I do not have eight subwoofers for absolute segregation of bass to seven respective full-range channels plus an LFE sub. So, in my setup, I experience some signal summing of bass before the bass is acoustically reproduced. I combine some of the signals electrically in order to not miss out on the bass in the channels for which I do not have an independent subwoofer while preserving a measure of bass differential that may exist between right and left in channels in a recording.

In stating that recording engineers generally wish to keep things in phase on each playback track, I did not mean to imply a continued practice of purposeful manipulation of the bass as was done for LP’s. I meant that, unless there is a reason to do otherwise, the original phase relationship of the original recording is maintained. In those recordings where a mono bass signal is distributed during mixing to two or more channels, a stereo sub setup becomes ‘dual mono’ playback. During playback where the original bass differential has been preserved or an induced bass differential exists, I’m glad I’m running stereo subs. Even if a stereo subwoofer setup does not exactly reproduce the original propagation of sound waves, in my perception a ‘live’ feeling is revealed. I have spoken in favor of stereo subs in the Saloon before. My enjoyment of SH’s organ recordings is enhanced by stereo subwoofers.