Karsoncookie Posted March 9, 2016 Share Posted March 9, 2016 So I have these 2x15" 904 like bass bottoms. K 45 KP drivers. They supposedly have been in full time cinema duty for 20 yrs. Do I take the time and risk by spinning them 180 degree ? They have no existing rubbing feeling or anything. Lars Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 9, 2016 Author Share Posted March 9, 2016 I've googled it only to find opinions, nothing solid. Is this ever done as "Maintenance" , or is it BS ? Lars Quote Link to comment Share on other sites More sharing options...
Coytee Posted March 9, 2016 Share Posted March 9, 2016 I've had my LaScalas since 1979. They are still in the same position & work fine. In fact, I think I've only had one of the bottoms off (ever) just to see what it looked like in there. Ok, so that really didn't help you did it?!! Quote Link to comment Share on other sites More sharing options...
moray james Posted March 9, 2016 Share Posted March 9, 2016 twenty years of gravity. Its real. Flip them they are past due. There are Doctors who make their living with the help of gravity. 2 Quote Link to comment Share on other sites More sharing options...
WMcD Posted March 10, 2016 Share Posted March 10, 2016 If it took 10 years to get them off center by X distance, will it take 10 years to get them back to center? WMcD 2 Quote Link to comment Share on other sites More sharing options...
moray james Posted March 10, 2016 Share Posted March 10, 2016 the more efficient the driver the lighter the cone so the problem will take longer. cone sag is real. If you flip every ten years you should not have a problem. This is one of the issues with down facing subs if they do not use a DC bias compensation which very few actually do. Sorry but I don't have a definitive answer to your question but if you flip on a regular basis of say every 5 - 10 years it won't ever become an issue. Some of the suspension dope used actually flow and accumulate the bottom of the cone suspension which then compounds the problem with additional weight for the suspension to support. Quote Link to comment Share on other sites More sharing options...
JJkizak Posted March 10, 2016 Share Posted March 10, 2016 My 1965's have never been flipped and the bass is clean. JJK 1 Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 If it took 10 years to get them off center by X distance, will it take 10 years to get them back to center? WMcD That's what I'm picturing. After much searching, there seems to be agreement that it depends on the particular speaker. The recurring opinion is "generally not really necessary", UNLESS you have Lowther drivers. Supposedly more susceptible to Granny droop. Lars Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 Let me re ask this way - Is this a typical part of any Pro application maintenance program? Colter? Hendrix? Thanks again, Lars Quote Link to comment Share on other sites More sharing options...
jason str Posted March 10, 2016 Share Posted March 10, 2016 I'm with Moray on this one, best to rotate. Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 Even though I'm not a moron, or subject to seizures, and have worked on A LOT of things in my life, I still know every time we handle a loose heavy woofer it is subject to accidental damage. Either from the screwdriver, or fingers. I can certainly quickly make a "protection plate" with a small hole drilled in it for a screwdriver, covering the speaker face from slippage as insurance. Anyway, otherwise, asking. Lars 1 Quote Link to comment Share on other sites More sharing options...
mattSER Posted March 10, 2016 Share Posted March 10, 2016 So weird. Never thought about rotating woofers. 1 Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 So weird. Never thought about rotating woofers. Well, first off, We're not talking like every Saturday morning. But, after like 10, 15, 20 (in my case) years. You have some amount of weight, albeit small, "floating" within a very small gap of , I dunno, estimating here, like .030" or so,supported only by the surround on the front. So, logically, usually, not always, but usually, or often, stuff sags from gravity. So , ya, it happens, and if it gets extreme, the coil can rub, and worst case (probably rare) scenario is the coil windings rub off the insulation and short out. So, ya, it's a valid question. Lars If I'm wrong, somebody please correct me. Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 Let me re ask this way - Is this a typical part of any Pro application maintenance program? Colter? Hendrix? Thanks again, Lars I still go back to this post, for the collective historically supported real world answer. Lars Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 In my above post - "So , ya, it happens, and if it gets extreme, the coil can rub, and worst case (probably rare) scenario is the coil windings rub off the insulation and short out" Maybe difficult to "short out" because the parts are electrically isolated, ( the magnet is not "grounded" or in any way referenced electrically) and even if the coil winding should rub against the magnet core (Interior) it may be ok as long as the coil itself does not short, which would probably take quite a bit of abrasion due to the voice coil wires being round.. BUT, you still can have a rubbing that maybe could impede the speaker motion, or, I dunno, cause some physical noise. I dunno, again, if I'm mistaken here, please correct. Lars Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 So weird. Never thought about rotating woofers. Well, first off, We're not talking like every Saturday morning. But, after like 10, 15, 20 (in my case) years. You have some amount of weight, albeit small, "floating" within a very small gap of , I dunno, estimating here, like .030" or so,supported only by the surround on the front. So, logically, usually, not always, but usually, or often, stuff sags from gravity. So , ya, it happens, and if it gets extreme, the coil can rub, and worst case (probably rare) scenario is the coil windings rub off the insulation and short out. So, ya, it's a valid question. Lars If I'm wrong, somebody please correct me. Actually, to correct myself, supported not ONLY by the Surround, but also the "Spider". Sorry, It's important for me to not use words loosely, but to be technically accurate. Lars Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted March 10, 2016 Share Posted March 10, 2016 The spider holds the voice coil in place, if the speaker cone exhibits such sag over the years that it should become uncentered, no amount of force or gravity will bring it back into place. I have a set of KP600's that were left in a barn for decades and the cones are ruined because of this - heat and gravity (the cones were stored face down), sagged the material of the spiders so badly that the woofers are ruined. I've never in my professional life heard of anyone 'rotating' their woofers. Kind of like changing the air in one's tires. You could do it, but I don't think it'd do any good. 2 Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 10, 2016 Author Share Posted March 10, 2016 OK, thank you all, I think I will leave them as is. All posts make sense, but I'm goin with Colter - "I've never in my professional life heard of anyone 'rotating' their woofers". . Lars Quote Link to comment Share on other sites More sharing options...
mustang guy Posted March 10, 2016 Share Posted March 10, 2016 (edited) The spider holds the voice coil in place, if the speaker cone exhibits such sag over the years that it should become uncentered, no amount of force or gravity will bring it back into place. I have a set of KP600's that were left in a barn for decades and the cones are ruined because of this - heat and gravity (the cones were stored face down), sagged the material of the spiders so badly that the woofers are ruined. I've never in my professional life heard of anyone 'rotating' their woofers. Kind of like changing the air in one's tires. You could do it, but I don't think it'd do any good. Hey Colter. I had a KP22 that was like that. I bought it from a woman on Ebay who's ex-boyfriend left it in her closet. The VC was almost bottomed out. I sprayed regular old Windex on the spider and the surround and put a couple dry rags between the cone and the frame a bit beyond the neutral position and let them dry. Not only did they stay at neutral, they were not flimsy feeling any more. I swear I made a thread about that. It was a big win, and that KP-201 is goin' strong. Edited March 10, 2016 by mustang guy 1 Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted March 11, 2016 Author Share Posted March 11, 2016 Mustang Guy- So you are the one to credit for the speaker to come out of the closet? Lars Quote Link to comment Share on other sites More sharing options...
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