jdire1 Posted January 21, 2003 Share Posted January 21, 2003 Does anybody know what the screen unside a K-77 tweeter does? Has anyone tried the tweeter without the screen? Please post your results. Quote Link to comment Share on other sites More sharing options...
Chris Robinson Posted January 21, 2003 Share Posted January 21, 2003 I'm going to guess it's for keeping the flies out of the ointment, i.e., to protect the fragile diaphragm behind it. It floats free on the subassembly, so I think it has no electrical function. My wild *** guess, anyway. Quote Link to comment Share on other sites More sharing options...
NOZ Posted January 21, 2003 Share Posted January 21, 2003 Most likely to protect against sharp objects from piercing the diaphram. There is a paper one as well, the same shape, that sits underneath it. Lets say some kid decides to take a pen and start poking around in there, the paper would be little or no protection. Quote Link to comment Share on other sites More sharing options...
nategr8d8 Posted January 21, 2003 Share Posted January 21, 2003 If you look at any industrial horn driver in either the public address or Hi-fi field developed in the 50's and 60's they will most likely have a screen to prevent foreign objects from entering the driver. This space is especially attractive to insects. The last thing that you need are spiders, wasps or flies nesting next to the delicate diaphragms. They tend to be very crunchy, messy and are difficult to remove without dissassembly of the driver. As far as the question on the screen impeding sound: As long as the screen does not resonate to any harmonics and maintains its original shape it is sonically invisible at audible levels. You will notice that the screens are domed on the K-55-V's. If they are puhed in use a dental pick or a solder pick to carefully pull them out. If necessary remove them and push them back out. I use a socket the size of the screen flange and a small machinist hammer to tap them back in. Quote Link to comment Share on other sites More sharing options...
WMcD Posted January 22, 2003 Share Posted January 22, 2003 The K-77 was built by Electro Voice. They have not published anything about it. So the factory is not talking it. I say that to be fair as to my source of information. I call them "bug screens". The nomenclature may obscure the virtue of the protection. The gap between the voice coil and the magnet in any design is very narrow. So it is important to have a filter to keep out foreign debris. The screens are not just something you find in the tweeters. I just bought some EV woofers off e-bay and there are similar screens in the vent at back of the magnet structure. They are very important structures which allow free flow of air, while preventing foreign debris from getting into the works. There were some fellows who thought that removing the screens would be a way to "hot rod" drivers used in the Altec horns. It is a natural suspicion. Maybe the designers put the bug screens in there to protect the drivers at the expense of better performance. So tearing them out would improve response. And they thought they heard some better results. I did this with an EV midrange driver and measured the results before and after with an LMS system. Nope, there was no difference. I suspected the inclusion of the screen might actually be something which evened out the load and so removing it would make things worse. My pet theory was disproved. I've not done it with a T-35 or K-77. Basically, I conclude the screens are there for good reason of mechanical protection, and they don't hurt any acoustic property. The guys at EV did it right to put them there. I'd be happy to reconsider the issue if someone can come up with measured responses showing that removing the bug screens improve response. Until then, I say, "Leave them where they be." Gil. Quote Link to comment Share on other sites More sharing options...
TBrennan Posted January 22, 2003 Share Posted January 22, 2003 Yeaqh Gil, no sh*t. I've lots of JBL and Altec drivers around here, some with screens and some without and I'm damned if I can hear any difference I'd credit to the screens. And these are drivers with extended high frequency response. Of my Altec 288s the one with screen intact measures slightly better than the one with no screen. Quote Link to comment Share on other sites More sharing options...
WMcD Posted January 23, 2003 Share Posted January 23, 2003 There, you see, Tom and I agree on something. Just kidding, I expect we agree on many things. I've taken apart some T-35 tweeters. There is a paper or cardboard gasket behind the screen, but it has a hole in it the same size as the opening. I.e., nothing paper in the way of the sound pressure. Again, I can imagine how someone will say, I don't have bugs or metal debris in my living room, and the screen must be degrading response. However, I don't find any reason to believe the latter. OTOH, the condition of anyone's living room is their own business. Gil Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.