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Author Topic: Speaker Phasing Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-08-2006 01:36 PM                     Looking back on some of the old posts on this subject, I would like some more info on a few things. I noticed Steve said using a PN generator was risking at checking speaker phasing. I think I found that senario today. I use a 2 piece phase checker myself. While checking phasing with the bass drivers, all speakers were in phase. After setting levels and EQing, I checked phasing again with the generator. Left and right were fine together, but center with either left or right seemed to be out of phase. I say "seemed to be" because of this. When I send pink noise in phase to left and out of phase to lets say right channel, there is a clear drop in low frequency. When I compare left or right channel to the center channel however, its not so clear. Either way I sent the phasing to center, I really dont get much of a drop from the bass. Also, I dont get the same increase as you would when they are both in phase. Follow me so far?? I guess this is why Steve made that comment about not really using the generator to check phasing. My last question is about HF phasing. Is it as important? I havent really read anything about it. It all seems to be about the LF phasing. Most of the horns I checked so far were wired differently. Some in phase, some out. Also, on a lot of the HF diaphragms I have replaced, polarity is not marked.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-08-2006 04:55 PM                     Phasing is of absolute importance! It must be correct with respect to each driver within a speaker and each speaker with respect to the other speakers. Don't believe me...connect your L&R speakers out of phase with each other and turn off the surrounds...they'll sound like they are on! Phasing is important within the speaker so that at the crossover point, the pressure waves add with each other from the two drivers...otherwise you'll have a more notable dip at crossover. Since you experimented with phasing...try flattening your EQs and then try the PN phase test...I'll bet it is easier to tell. Steve  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-08-2006 05:53 PM                     I do understand that phasing is extremely important. I figured that the EQing probably had something to do with the PN results I saw with the center speaker. The HF phasing is something that has bothered me. You're saying that it's as important as the LF phasing, which I do believe you in that. My question is why I have never heard people talk about it as much as LF phasing. I have found so many more HF drivers out of phase than LF drivers. Also, as I had mentioned, the labeling on a lot of HF drivers that I have seen doesnt tell you + and -.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-08-2006 06:18 PM                     Well I always drag out the phase checker and test the Hf and LF units as matter of course Like the X curve it is part of the drill and when time alignment is completed the system is more transparent I have a breakout box that goes from the phase checker generator to the D sub for the aux input so I can switch t between cchannels and it passes throught the entire chain ensureing there are no hidden phase reversals  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 10-09-2006 10:16 AM                     I have experienced so many sound calls where phasing was the issue, especially on HF. Situations such as new speakers from the manufacturer miswired, different brands of amplifiers running in a rack, surround speaker terminations miswired, replacement components miswired.....phasing is the starting point  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-09-2006 10:55 AM                        Then remember that MOST JBL speakers are made out-of-phase compared to all others. (See THX instructions) Louis  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 10-09-2006 01:18 PM                     Louis, I have a theatre with 2 JBLs and 1 Altec and the phasing was indeed different between them. Also have a theatre with RCAs and an Altec, must be checked very carefully for proper phase or the results are very poor. KEN  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 10-10-2006 12:18 AM                        Is this valid for home systems too? I have one that has different branded speakers. Actually my surrounds came from another system, and weren't intended to be used with this one, they were hard wired. I cut the wires, and stripped them and they work, they are right impedance, but I still have to have them all the way up to balance them, and they're still a tad weak. Of course they simply could be less efficent, too. But not by that much.  |  IP: Logged Cameron Glendinning Jedi Master Film Handler Posts: 845 From: West Ryde, Sydney, NSW Australia Registered: Dec 2005 posted 10-10-2006 05:51 AM                     quote: Richard May My question is why I have never heard people talk about it as much as LF phasing. I have found so many more HF drivers out of phase than LF drivers. This has alot to do with the crossover and placement of the horn, 6db (90 degres out of phase,) 18db (270 degres out of phase) traditionally pos to pos termanal. 12db passive crossovers is 180 degress out of phase and traditionally pos to neg of horn, meanwhile the bass pos to pos as a rule. For the best result the magnets of the speakers should be lined up depth wise, with the horn slightly forward to compensate for the fact that the speaker is up at 2/3 hight of screen. this is time alignment non digital style and has a big effect on phasing. I have made speakers for cinemas that are wired identially but in one screen, the best result was by reversing the phase of the centre channel only (off the eq equipment) so trust the test gear  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-10-2006 12:18 PM                     Why are some speakers made out of phase like Louis says. Also, are there any reasons that you would leave a certain driver wired out of phase compared to the other drivers?  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 10-10-2006 12:39 PM                     Phasing standards vary with some sound manufacturers...with experience you generally know what is required for matching purposes. Sometimes the information is mentioned on the specification sheet, such as + voltage on red = forward excursion.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-10-2006 01:22 PM                        The story I got was that James B. Lansing was a lefty so he wound the cores anti-clockwise. Some newer JBL product is "normal." This is the equipment from off shore or from a "normal" sub-contractor. Louis  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 10-10-2006 02:30 PM                     If you run silent movies you can phase the speakers out. Sorry for the bad joke. Haven't been here in some time and felt like posting something  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 10-10-2006 05:22 PM                     There is an old trick of putting a 1.5V battery across the terminals. If the speaker cone moves outward, then plus on the battery is plus on the speaker.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-10-2006 06:19 PM                     Since James B also was Altec...and they are always + on red equals forward driver motion...the JBL being a lefty is out. However, when JBL was formed, I guess they just had to be different than their previous company and with the + on Red equals reverse cone motion (away from the listener). This continued on JBL well into the 90s. Since virtually EVERY other speaker manufacturer went with the Altec convention, JBL has made all NEW drivers with the Altec convention, unless they are a direct replacment of a "legacy" type driver. So...if you have a JBL 2225 driver (pre current manufacture) and replace it with a JBL 2226...all will be well...the 2226 is a direct decendent of the 2225. Likewise for the 2246 vs the 2245 and so forth. However, new drivers like the 2242 which show up in the current JBL subwoofers but are NOT replacements for say the 2245, carry the current convention (Altec). The 2241, on the other hand is a replacement to the 2240 so it uses the older JBL convention...confused yet? Presumming that the day comes when they depart from all of their legacy drivers JBL will have the same convention as all other manufacturers but until that day...one has to keep track of which driver they are dealing with.  |  IP: Logged

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