Originally Posted by Mfusick
You have some canceling effect ?
I won't know until I run the measurements, but I don't think so. The issue from what I understand it is just how Audessey works. It calculates the distances, EQ, crossovers, Delay, etc. (Or it makes calculations on those things based on some things the AVR tells it) I'm sure I'm going to butcher this explanation somehow, but from what Mark Seaton discussed with me, there are things Audessey does very well, and things it doesn't. Especially in XT32, Audessey does an excellent job of implementing a good EQ without the need of manual calbiration but it doesn't do a good job of crossovers... that is to say, the AVR doesn't make a good decision of what should go to your sub and what shouldn't. BrolicBeast, who owns a pare of SubMersive F2s said himself that when he hooked them up and ran Audessey, his first thought afterwords was that he might have wasted his money. This had nothing to do with the subs, which are incredible, but everything to do with the AVR and how Audysset set the crossovers and LFE levels. Adjusting those slightly made a night and day difference and his subs came alive! Audyssey in combination with the AVR measure individual speakers, so the AVR determines my mains might be able to handle frequencies down to 40/50Hz with no problem, however that means that the LFE filters are not handling anything below that range, so raising those crossovers moves information in that range to the MultEQ filters, which are very good, and to your sub, which probably plays those frequencies better than your speaker anyway. Besides, anything 80Hz and below usually is more of an Omni-directional signal, meaning that the waves are too long for your ear to be able to determine where they come from, so the fact that they come from a specific speaker is sort of irrelevant unless the speaker can play that frequency better than the sub.
The two things that Audyssey did on my system was :
1) Set the Bass Gain levels way too low, given the crossover settings. (This might not be necessary to change if you change the settings in #2, as it results in a lot more bass!)
2) Set the cross overs as if I had no sub at all. Most of my speakers were set at the 40-50 range as far as crossovers, including my rears. On top of that, it set my LFE filter to 120Hz, but it should always be this since that is what information on the LFE track is mastered to. Yes, most of the Big Bass notes we often talk about tend to be in the 20Hz range, but these crossover settings were preventing the subs from receiving a lot of the signals which make a sub come alive. 80Hz is the THX standard regardless of size, but changing those crossovers will impact your entire sound stage. 80 might not be perfect, but it showed me right away that the settings were the primary factor in my lack of bass in the room. I could maybe take the front speakers a bit lower due to their listed capabilities, but it would take some tweaking. Basically, even if the speakers could play the frequencies below 80 well, they don't need to. The load would be removed from all of those speakers and placed upon the sub instead.
See Chris Kyriakakis' (Audessey) thoughts on the "Small/Large" blog on the issue: He basically states, "If you have a subwoofer, all of your speakers are Small"
He (Chris) was also asked the same question on the "Subwoofer setup and MultEQ" FAQ on the Audyssey page. Question "Audyssey set my mains/center to 40Hz and my surrounds to 60Hz, I have in the past changed these to 80, in your opinion, is this correct?" And Chris responded, "It's OK to move the crossovers higher. This sends more content to the subwoofer MultEQ filters that have higher resolution." he also stated in his 101 page, "Sending more content to the sub is a good thing if you have MultEQ or MultEQ XT because the filter resolution in the sub channel is 8x higher."
If you've ever tried to read the entire Audessey thread, you will get a lot of contradictory statements. Some people say exactly that, no matter what set all of your speakers to "Small" and have 80Hz crossovers. Others say with XT32 you should just calibrate your system and use it as-is. This is "What reference bass should be". I think the answer is somewhere in between. I do agree that the bass is much more tight and controlled without adjustments in the pure-Audessey config, but it also has no "Impact". The "All 80" setup had a LOT more bass. A lot more rumble.
I'll tell you right now, these Axiom subs were rated well, but they only have 1/4 of the amp that a SubMersive has. If I did the same EQ settings with two of those in my room, I'd probably take my panels off of my walls unless I did some serious -db settings!
Another thing that Mark mentioned to me in regards to my sub positioning was that I should be using them as one sub. He stated that there was little to no benefit of running each sub independently when they are on either side of the center channel, since the room would respond to them almost identically. In fact, it could actually cause problems in things like delay because they are so close and Audessey isn't perfect. He recommended that any two subs that I run in those locations should use a Y connection, or a daisy-chain from one to the other, to threat them as a single sub that gets the same signal. The multiple sub-outs was primarily designed for configurations like one on each side of the room or a sub on the front and a sub in the rear.Edited by damelon - 7/31/13 at 8:06am