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

What would you recommend for this 5.1 setup (70 percent music, 30 percent movies):
Fronts M80 HP
Center VP180 (non-HP)
Rears M22
Sub EP800
Amp Rotel RMB-1575

Rear at 80 is obvious. Question is front array with these possibilities:
80 80 80
60 80 60
60 60 60
40 60 40
Thoughts please? Thanks.

Also, I have “original” EP800. If anyone possibly knows, curious about the subsequent changes? Just amp programming, or actual different amp and/or physical change to drivers?

I have the 800v4. I know the amp is definitely different than the original that Tom Cumberland engineered. Besides the continously adjustable phase control and the lack of a USB port, I don't know what all the differences are. Andrew also got rid of the room gain knob which was nothing but confusing for me. I bet the DSP code is better (lower distortion, etc), the firmware and hardware more robust and reliable and it just plain sounds better than the original. I also think the drivers and cabinet are much improved. I am taking mine to my grave. I lived with the curse of the 600v2 for 11 years and thank Ian that a year ago he let me trade in for an 800v4. The v4 DSP subs are simply amazing. You might want to consider trading yours in for a 600 instead of an 800 if cost is an issue.

Geez, that looks like a nice amp. Congrats! It's tough to make a call on what sounds best for cross-overs because it depends on room, ears and gear. I've found my system sounds best with the 160v4 and QS10HP at 40Hz and M5HP at 80Hz. My Onk's Audyssey XT32 found them all at 40Hz by the way.

without any knowledge of your dimensions, processor or listening level all I can say is that a higher crossover setting will allow greater phase adjustment relative to the main channels.

Higher crossover= shorter wavelength= more possible relative delay (phase rotation)

To better understand your answer did some further reading and came across this:
https://jlaudio.zendesk.com/hc/en-us/art...obile_site=true
A similar situation exists with home theater (e.g. “surround“) setups where the customer thinks that the front speakers are ”full range“. Even so, the best approach is to seal the ports, operate the 5 channels as ”small", crossover at 80 (or even a bit higher, but never lower) and correct the timing issues inherent in all modern subwoofers by setting (in the receiver or processor’s setup menu) all the distances the same, and to a small number such as 7 feet; then set the subwoofer to 12 feet more (i.e. 19 feet) and then use the variable phase control on the subwoofer to fine tune the relationship at the 80 Hertz crossover point.

Bang on!

The only thing I would caution is the phase control knob on the back of a subwoofer isnt really an accurate solution. It is not as granular an adjustment as the actual distance setting in the processor. Also, a phase knob on the subwoofer can only retard its position in time relative to other channels, not advance.

In a 5.1 setup, set all your speakers to 80hz. You would need fantastic bass from the M80's and a really bad sub (not the case for the EP800!) for 40hz to win.

I'm reminded every time at how good the EP's are when I cycle through sound modes and hit direct and my L/R go full-range and the sub is turned off. Let the sub do what it does best.

This is how I solved the problem of standing waves with my M3s and yammie sub in my living room. I stuffed the sphincters of the M3s with foam. All issues disappeared without using any EQ.

I don't understand where he gets the numbers of 7 feet for speaker distance and 19 feet for sub distance. Those must be examples.

You stuffed the gorilla rectums with foam?

Oh hell not me, Phil. I'm scared of those damned things. I had one of my fem friends stick her delicate, little hand in there. She actually quite enjoyed it!

I stuffed the M5s and the 160 with foam in my main room and cut all speakers to 80Hz. I'm even more close now to not needing Audyssey. I have a very narrow band somewhere down low I need to knock down.

Incidentally, even with the sphincters plugged, the Onk found all my speakers at 40Hz which I find very surprising.

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.

I'd help you, Blair. The problem is, everytime I help some guy, his wife hates me because I end up throwing all the shit she's accumulated over the years out of the A/V space. I also re-arrange the furniture and speakers. I even pull most of the furniture out of the room. The guy then hears the end result and is so blown away, he can't wait until she moves out!

Serenity can help you over the phone and email. He does it for a living and uses science. I'm an empiricist myself because I enjoy aural masturbation.

We just had a discussion about our theater. Wine on the floor, monkeys and skid marks on my acoustically transparent screen were at the top of the list.
I love how my room sounds but I also know it's never been setup 100% ideal. In the many iterations I've tried they've never been digitally corrected. Best case YPAO, an uncalibrated app and my ears.

My wife claims ownership of 3 vhs tapes, 12 cd's, 2 dvds and about a half dozen bluray conerts in "our" theater.

Blair, I think I know what's confusing you about Trevor's very good analogy. The Ferrari and dump truck speeds are not always constant relative to each other and neither is the length of the towbar (phase angle is a function of frequency - and amplitude too!). Does this help? LOL! It's all so complex not even the hand of God can make it right.

Those VHS tapes of hers have to go. They're really messing with the spectrum above 1.28KHz.

Right.

Lowering the frequecy is like moving the finish line further. Raising moves it closer. The lap length is a function of cycle length. So we need to recalibrate.

We are limited by the AVR with how much delay we can apply. Maybe you cant sync right at 60hz. To get around this you can raise the crossover frequency. Higher frequencies require less delay to cover full cycles.

Head hurt more?

It's all good. I haven't seen it in person, don't really know where to start.
It already sounds good, just one more tweak. Lol.

The VHS tapes have special events recorded on them, SQ isn't the priority with them.

Blair, regarding the VHS tapes, it's not the audio that's on them that I'm talking about. If they're sitting on a shelf, they're affecting your listening because above 1.28KHz, their scattering characteristic is non-linear. So those tapes distort The Family of Curves Axiom worked so hard to shape.

I'm thinking of taking 3 months off work between February and April to busk with my 2-string cigar box guitar in New Orleans. If I stick around in Calgary, I'll let you know.