Axiom Home Page Forums General Discussion Home Theater Please weigh in on crossover settings

I ended up unstuffing the speakers in my main room. It just didn't sound natural. I continue to be very happy with wide open sphincters.

The living room is another story. I'm finally enjoying tunes in there now with all holes stuffed.

Eventually the M3s may get replaced with M5s which are most definitely better if the M100s turn out to sound better in my main room.

The one flaw I find with many room calibration systems like Audyssey, MPACC, YPAO, etc... is that the measurements are done with one speaker at a time receiving the test tone, even if the system takes measurements in different locations. It is possible the fancy algorithms can predict what the standing wave results will be when all are firing but, as we have all experienced, the results are not always optimal. I think some of the higher end Audyssey and Dirac systems may actually take multiple microphone samples with multiple speakers firing but I don't know for sure as I don't have the budget to own such flagship systems.

What I have concluded is that the calibration systems are capable of determining the frequency a speaker begins to roll-off. In other words, depending on placement, our speakers are "capable" of 40hz sound reproductions. However, it may not do it as well as our subs... In fact, our subs are probably better at reproducing 80hz and below to our ears which is why many recommendations are simply to set all at 80hz.

That said, taking into account all things that will impact sound in your room (windows, walls, tables, kids, speaker placement, wall hangings, etc...) I highly doubt there is a specific configuration but more of a range of optimal performance. In other words, crossover between 50-80hz is likely to be almost imperceptible to your ears.

I LOVE to play around with the settings. It's an addiction. However, I've discovered what seems to work optimal with SACD's isn't my favourite for Ultra HD Blu-Ray movies. And don't get me going with Spotify, the quality of recordings is just all over the map! (OK, I get the same problems when ripping to FLAC, it's almost impossible to set volume levels equally across different recordings :-( ).

All this to say, if you have a capable sub and you use it, let it do the dirty work and let your speakers focus more on the mid and hi ranges.

Over the years I've read on multiple occasions to take the recommended or stated lowest frequency that your speaker in question can deliver and double it for the crossover. {Eg. 40hz. to 80 or 60hz. to 120}.
If you check some of the Subwoofer specialty companies or popular models. This is their common recommendation. When using line level or RCA jack.

Although if you check the REL sight and lots of stereo aficionados they actually recommend the high level input to mate the subs to speakers. For matching signals"better"

Using a high level input (speaker cable) should be a last resort. It is a compromised implementation of a subwoofer. I'm not saying don't do it, but you are leaving a lot of performance on the table.

Subwoofers are most effectively deployed in systems which have discrete channel processing. Ideally the knobs on the sub should not be used for anything other than the onboard amp gain setting. Low pass should be set to max or bypass. Phase should be left at 0 degrees.

There is a specific configuration that is optimal for subwoofer performance. It is unique to each setup and requires calibration using a transfer function tool to align phase properly. Not unlike using a colorimeter to calibrate a display. The results are quantifiable.

The difference between 50-80hz crossover requires a change in delay offset to properly re-align. Toggling between 50-80 without re-alignment is readily perceptible once you first properly align for either frequency.

When the sub is properly aligned with the mains you can get away with a slightly higher sub trim level without starting to bloat the presentation. You can load the room harder before problems start. This allows you to protect your mains from over excursion without loss of output or fidelity at higher SPL.

Hope this helps you chase the last few % TDIPablo

A continuously variable phase knob is a good thing to have because the receiver's sub distance setting may not be granular enough. Half a foot at 80Hz is about 15 degrees and that could be the difference between good and excellent.

When are you coming over here to witness how marvelous your sound panels are at converting acoustical energy to thermal energy?

I wonder if the argument for using high level inputs is to have confidence that there isn't a delay between the low level signal going to the sub and the amp output going to mains etc... that can't be adjusted out with typical sub controls ?

Seems unlikely but not impossible... I see what appears to be interchangeable use of phase and delay when the two are actually only related at a specific frequency.

Phase is the relative position between 2 waveforms.
Delay is the adjustment to align the waveforms better.

I know some of you get it, but for those that don't yet here is an analogy.

Two cars are at the starting line of a race. We want to end the race in a photo finish. One is a dumptruck. The other a ferrari. We have to let the dumptruck get a head start, because it is very slow to leave the line. The Ferrari will catch the dumptruck quickly, so we have to delay it leaving so it wont cross the finish before the dumptruck.

Lets say we let the dumptruck leave too early. It finishes a lap ahead of the ferrari, but still crosses the line at the same time. The dumptruck is now one phase rotation ahead of the ferrari. If we get it right, both vehicles will cross the finish at the same time on the same lap. This is what we want. In phase and in time.

We want to properly sum waveforms so that their impulse is at maximum amplitude and shortest duration. ie. in phase and on same cycle.

Using the high level inputs is like attaching a towbar between the ferrari and dumptruck. The ferrari tows the dumptruck at a set distance. Using the phase knob extends the length of the towbar. We cannot get them to photo finish. The best we can do is extend the towbar to one length of the track so the vehicles cross at the same time, but are one cycle apart.

Back to Calgary in March

Wow thank you for such an in-depth explanation.

Recently have been seeing recommendations for the high level, in stereo setups. REL subs come with a funny high level cable. Looks really thin. Think they recommend for matching Amp. signature through sound stage.

I hate my brain.
I read your explanation but I don't know how to get there.
I'm always in pursuit of achieving better sound with what I have, its too bad I don't live closer to one of you guys. I'd bribe you to come over and tune my room.