Grimer Posted August 22, 2004 Share Posted August 22, 2004 Does Klipsch make a shielded sub? My 7 yr old 12 inch powered sub is turning my Sony 36"XBR purple under the TV in my new built in entertainment center. any suggestions otherwise? thanks Quote Link to comment Share on other sites More sharing options...
Malcolm Posted August 22, 2004 Share Posted August 22, 2004 Move the subwoofer. Quote Link to comment Share on other sites More sharing options...
Scp53 Posted August 22, 2004 Share Posted August 22, 2004 just don't use a sub Quote Link to comment Share on other sites More sharing options...
Grimer Posted August 22, 2004 Author Share Posted August 22, 2004 Though I appreciate the replies, move the sub, and just don't use a sub are rediculous suggestions. As I said, I have a NEW entertainment center, custom designed by me to have the sub underneath the TV. It was expensive and moving it or not using it is not an option. Anybody else? Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted August 23, 2004 Share Posted August 23, 2004 well you paid too much to have a custom subwoofer underneath ur tv. whose bright idea was that??? Quote Link to comment Share on other sites More sharing options...
Scp53 Posted August 23, 2004 Share Posted August 23, 2004 Grimer, I was just joking about not using a sub. maybe what you could do is buy a sheilding magnet(not sure of technical name) and put it on the end of the magnet of the subwoofer driver. I think partsexpress.com sells these. this should solve the problem. scp53 Quote Link to comment Share on other sites More sharing options...
Malcolm Posted August 23, 2004 Share Posted August 23, 2004 Actually, designing and building a custom entertainment center with the sub directly under the TV is ridiculous. You should have done your homework first. Any TV that uses a CRT depends on fairly weak magnetic fields to move the electron beam across the screen to paint the picture. Subwoofers generate fairly strong magnetic fields that can interfere with the ones in the TV. And the subwoofer's magnetic field can also magnetize the CRT's shadow mask so that even if you move the subwoofer away, the picture is still distorted. Then you have to degauss the CRT. If moving the sub, or not using it, is really not an option, then I think you are SOL. I am not aware of any shielded subwoofers, at least none that aren't toys. I think there are two reasons subwoofers aren't shielded: shielding a big magnetic field is not a trivial, non inexpensive, task, and the demand isn't their because most folks just don't put their subs under their TVs. Unless you can find a shielded sub, I guess you will have to get used to the distortion. FWIW moving the sub should not have much sonic impact. The human ear has difficulty localizing low frequencies. So subs work well when placed somewhere besides directly under the picture. Quote Link to comment Share on other sites More sharing options...
Grimer Posted August 23, 2004 Author Share Posted August 23, 2004 Well, you might want to be aware that there are quite a few that are shielded. Yamaha and Polk to name just two. They may not be Klipsch, but Polk makes a decent speaker. I don't know which route I'm going to take. I don't think putting the sub underneath is rediculous. I've seen it done a lot, mainly for the way it hides it. There is a site, LessEMF.com that sells magnetic shielding material. And from searching on Google I've found where one guy used 7 layers of heavy duty Aluminum foil which worked. Yeah, it's not a great situation to be in, but what are you going to do? I guess I didn't do all my homework, you're right. Quote Link to comment Share on other sites More sharing options...
Malcolm Posted August 25, 2004 Share Posted August 25, 2004 You are right, some moderate size subs that claim to be shielded are beginning to show up. Just goes to show you I haven't been in an audio store recently. Too busy learning to weld. If you decide to go with one, you might want to buy it somewhere you can try it before you buy it, or at least return it. Shielding is a relative matter. There is no cost effective way to eliminate the magnetic field from a speaker. All that can be done is to reduce the strength of the field at a given distance so you can place it closer to the TV before you start to see problems. The strength of the field will not be the same in all directions. Moving the sub a few inches, or rotating it a few degrees or 90 degress, can sometimes make all the difference. There is nothing magic about magnetic shielding although it is an art. All you need is a sufficiently massive, properly designed shield made out of a material with high magnetic permeability. The shield effectively short circuits the magnetic field by giving it an easier path that going through the air. Pure iron is very good for this. There are proprietary alloys which are even better. But they are generally very expensive because they contain expensive metals like nickel in high percentages. They are used where weight is important. Aluminum is very poor. A few layers of aluminum foil will not have a noticeable effect. Bucking magnets can also be used to partially cancel the magnetic field of the speaker. Speaker motor design also plays a part. There are some designs using alnico magnets that have relatively small stray magnetic fields. Unfortunately, the typical speaker motor design of today using a ferrite magnetic produces relatively large stray magnetic fields. People on occasion complain in these forums that their shielded center channel speaker, or shielded mains, interfere with their TV. My guess is that a resonably powerful sub shielded well enough to live directly under your TV is unlikely. Good luck in your search. Let us know what you find, good or bad. Post some pictures of your cabinet work if you like. There are lots of folks who would be interested in what you have done. Quote Link to comment Share on other sites More sharing options...
JewishAMerPrince Posted August 25, 2004 Share Posted August 25, 2004 Grimer First you should understand that so-called "shielded" speakers are not shielded at all. There is no way to effectively shield strong magnetic fields. Understanding that, how does a so called "shielded" speaker work it's magic? The answer is very simple;it uses bucking magnets to cancel the external effects of the drivers magnet. Bucking magnets are nothing more than large magnets of opposite polarity to the speakers magnet, and usually strapped right to the back of the drivers own magnet. That having been said, I would look up a speaker repair facility in your area. If you can find one with some real expertise they should be able to modify your existing sub with bucking magnets. I did that years ago with a KG 3 to create a center channel that could be placed on top of my RPTV. One word of caution, any attempt at "shielding" is never 100 effective, even in a manufactured speaker. You may still have residual problems with a "shielded" sub. Very simply, your subs location under the TV is not optimal. Jerry Rappaport Quote Link to comment Share on other sites More sharing options...
doudou Posted August 25, 2004 Share Posted August 25, 2004 what about buying a video projector? so no problems with magnetic fields. Quote Link to comment Share on other sites More sharing options...
neomartic Posted August 25, 2004 Share Posted August 25, 2004 If not a video projector, get a plasma tv. You could even use your subwoofer problem to help you persuade your wife or girlfriend that you need a new tv, otherwise everything is going to be a fiasco! Sounds good to me! Quote Link to comment Share on other sites More sharing options...
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