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Author Topic: How to find a bad driver? Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 06-02-2009 03:20 PM                     I received a report that a speaker in a theatre sounds like it is blown. I have listened to the sound, but have not detected anything unusual. So, I'm curious if there is some test I can perform to stress the speaker in different ways to possibly find the distortion which was reported. The reported problem was a crackling sound during a normal volume dialogue from Spok during the movie Star Trek XI.  |  IP: Logged David Stambaugh Film God Posts: 4021 From: Eugene, Oregon Registered: Jan 2002 posted 06-02-2009 04:29 PM                        I dunno, Spock's been through a lot including death and living in at least 2 timelines. Maybe he just had a little phlegm that day.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 06-02-2009 04:33 PM                     You can climb backstage and hear your center speaker HF horn to see if that diaphram has cracked since it was during voice that the distortion was resulting from. You could also have alignment issues, tired amps - all sorts of issues that can cause speaker distortions.  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 06-02-2009 04:45 PM                     How to find a bad driver? Look for the person who is talking on their cell phone while behind the wheel. It could also be dirty connections, or switches.  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 06-02-2009 05:26 PM                     Generally, you use a tone generator and sweep up and down. Usuall, you will hit the exact frequency and then you will hear a rattle or something not right.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 06-02-2009 09:35 PM                        What kind of driver? Every time I get these kind of calls, I find either a bad amplifier module or, more likely, really bad EQ or levels in the processor leading to clipping. The last one was a pair of CP-500s (set up by Dolby employees) with the bass fully off and +-15db EQ in the mid range. Clipping was horrible on Star Trek. Louis  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-02-2009 10:09 PM                     Sweep tones are my favorite...Got a Dolby Jiffy test? Steve  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 06-02-2009 10:23 PM                        Move over to Mac where you don't have to uninstall bad "drivers".  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 06-03-2009 01:40 AM                     (a bad driver is when the face of the driver doesn't grip the ball too well when it's hit out of the teebox and it doesn't give it the reverse spin for good lift as needed causing the ball to drop and die way short of the shot....- okey, hit me )  |  IP: Logged Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 06-03-2009 10:13 AM                     quote: Steve Guttag Got a Dolby Jiffy test? No, but I wish I did. Does anyone know how I can acquire this test film? I do have a tone generator, so I'll give that a try. Clipping indeed is a great suggestion in the pre amplifier stages. Any suggestions on how I could introduce some test signals in this area which would expose an error in the EQ settings or would it just be better to perform a B chain from scratch and see what happens? As for the comic relief replies...thanks all...funny stuff  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 06-03-2009 02:40 PM                        Look in any Volvo! seriously: Plug into the power amp input with your oscillator and sweep. As regards EQ; us old-timers can just look at the eq settings and tell if there are "issues." 1. Are most settings "up' or "down?". 2. Are settings "violent" (fully up or down.) 3. are setting up and down right next to each other? 4. Is every setting somewhere other than zero? (Should be 8 or less in an average cinema room.) Louis Massive correction is best done with the bass-mid-high control, with smaller correction performed with the third octave controls. Louis  |  IP: Logged Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 06-03-2009 05:56 PM                     quote: Louis Bornwasser Plug into the power amp input with your oscillator and sweep. I was just thinking about employing this method. Thanks for the confirmation. The EQ looks fairly reasonable mostly centered around 0 for each band which may vary as much as 2 db boost or cut. The curve looks parametric and not jagged. For channels L, C, and R.  |  IP: Logged

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