I wouldnt say most Pros and Recievers do that automatically, it is gaining popularity but far from the majority. |
Most surround sound processors and receivers automatically detect reversed speaker wiring, which results in an out-of-phase test tone from the miswired speaker. The calibration microphone detects the initial sound wave deflection as negative when it should be positive, and the processor then tells you to correct the wiring.
This "feature" can occasionally be a problem with some multi-way speakers in which the polarity of one driver has been deliberately reversed by the speaker designer. In this case, the processor/receiver may show a polarity error when the wiring and phase are actually correct. |
"Another question just popped in my head. How many 1) actually follow this concept; 2) have ideal room setup/situation (unobstructed and equidistant); and 3) are willing, better yet know how, to adjust the processor to compensate for the setup shortcomings?"
I actually did design home theater cabinetry in this way. Protruding columns move the LR speakers close enough to for the correct arc. Also, this can be done with theater "screen walls" made of black acoustic speaker grille fabric. A fixed screen floats on the center of the wall. Behind the "screen wall" speakers can be set on stands and moved about as desired. If the speakers are set proper then timing, phase and level require little or no adjustment. |
Jackson - By all means I don't think you are picking on me. I have much thicker skin.
Your perception of phase is correct. However, when it comes to surround sound, it can take on a different "form", for a lack of better terms.
Hopefully this will explain things a little better. Fair warning, this goes completely against what you instruction manual or common surround expertise has to offer. If your system is fortunate enough to make the setup (no furniture, lack of other objects in the room, exactly the same distance), then this is of no use.
Take your front soundstage (L,C,R) speakers. For this purpose lets say your L and R speaker are 10ft. from the listening position. You dial in 10ft into the processor for the L and R. The processor "directs" or "coordinates" the necessary signal processing and so that the speaker ultimately produces the sound to arrive at the correct time based on the inputed distance. Now lets add the C. Again, if the speaker is located 10ft, just about everyone sets the C distance to 10ft in the processor.
Here's where the delay can effect the phase of the speaker. If the C is set to 12ft and its actually 10ft in distance, for example, the processor is essentially telling the speaker/drivers to speed up playing the information so that it would arrive at the listening position as if it where physically located 12ft away. Remember, you told the processor the C is 12ft, but its really 10ft. This equates to less delay and faster driver motion. The C is out of time sync with the L and R, and the phase has shifted for the C drivers in comparison to the L and R. FWIW, this goes hand and hand with the comments I've made in the past about having all 6 speaker (LCR, Rears and sub) playing as one. Thats another discussion for later, though.
Give this a shot. Whatever your C channel setting is, back the distance up in the processor (in smallest possible increments). If it's 10ft, tell the processor its 10.5 and listen to the change. Then do 11ft and listen. 11.5ft and listen. You will notice an increase in depth perception. Depending on your rear settings (same rules applied too) you will notice an increase of soundstage width. For reference, you may have to quite the C a bit too. Maybe a db or 2.
I hope I didn't confuse you even more. If so, I am truly sorry. If you still don't get what I'm saying, but actually care, shoot me an email. |
Cdwallce, I'm not trying to pick at you, so please don't take it that way, but I think your wrong. Phase, as I understand it, is when the cones move in motion with one another. You can have two speakers located at an identical distance from your listening position and still be out of phase with one another.
Of course having speakers located at different distances is of concern as well. However, this is something that virtually every processor I know of can easily account for with correct dealy settings. |
"Cdwallace, I really don't think this has anything to do with my question. I was talking about checking the phase, not delays."
Jack, is DSP (processor) based surround sound, when you have a speaker placed at a certain distance, and you tell the processor its placed at either further than or closer than the actual placement distance, it effects the phase of the drivers/speaker (in comparison to the other front speakers).
My comment may not have been directly related to your question, but it certainly is on topic and corresponds to the comment Steuspeed made.
Nevertheless, I'm glad your question was answered and issue resolved. I'll shut up now! |
Cdwallace, I really don't think this has anything to do with my question. I was talking about checking the phase, not delays.
Delays are easy to set in most processors, especially one's like my Arcam where you just plug in the distance from the speakers to your listening position and the processor employs the correct dealys. |
"The front speakers should all be the same distance from the seating position. If the Center speaker is closer, the processor can delay the timing. Typically its 1 millisecond per foot. If you can set them equidistant with no adjustment, that is ideal. "
Another question just popped in my head. How many 1) actually follow this concept; 2) have ideal room setup/situation (unobstructed and equidistant); and 3) are willing, better yet know how, to adjust the processor to compensate for the setup shortcomings?
IMO, this is a major reason why so many audiophiles simply give up on processor based surround sound (gimmick is the word they use most often), bypass discrete MC, and concede back to 2-channel for everything (HT and music).
Basic principals like the one discussed here are essential for surround sound. Few are willing to learn why. Sad but true! |
Thanks all. I think it's probably in-phase, but I'm going to roll the leads tonight just to check it out.
I haven't had any issues, but I do run my three front speakers full range and got to thinking about the phase of all speakers, especially since I use a different amp for the main channel. |
Mike has a good idea with switching leads but you can do this test he suggests and have better results by simply using your calibration test tone so you have a steady easy to hear signal. |
another simple test is to reverse the + and - speaker leads and see if the center image gets more diffuse or more focused. obviously if it gets more diffuse the original orientation was in-phase. be careful as not all program material has center channel info so the result could be misleading. i would make sure the recording you use has clear center channel content (voice is best).
personally; i have recently added multi-channel to my dedicated 2-channel room for SACD multi-channel. i feel strongly that a center channel for music only detracts from optimal performance for both multi-channel and 2-cnannel. i use an analog 6 channel preamp for my multi-channel......and have had it wired to create a 'phantom' center. the center channel signal is split and added equally to both front left and right channels. this gives me at least as good a center image as having a center speaker and eliminates the negatives of the center channel. |
Steuspeed is commenting on time alignment more than phase. I think the OP means is his center channel woofer moving out when the others are, and vice versa. There are a number of multichannel test discs, but my favorite (cuz it tests phase for all 5.1 speaker combinations) is MDG's Breakthrough Into a New Dimension DVD-Audio disc. It checks relative phase for l/r, l-center, r-center, etc. It's $19-25 at CD Universe, Acoustic Sounds, etc. |
Here is a great way to test phase, if you have any THX movie DVD's there are Optimizer menus where you can test for phase, if it is in phase it will sound properly anchored to its position, if it is out of phase it will be hard to place where the sound is coming from, if you dont have a THX disc try and rent one, the color tracks can be fun for casual TV tuing aswell. |
The front speakers should all be the same distance from the seating position. If the Center speaker is closer, the processor can delay the timing. Typically its 1 millisecond per foot. If you can set them equidistant with no adjustment, that is ideal. |
