Reproduction Speaker Grill Cloth Buzzing... - Printable Version
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+--- Thread: Reproduction Speaker Grill Cloth Buzzing... (/showthread.php?tid=13220)
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RE: Reproduction Speaker Grill Cloth Buzzing... - mikethedruid - 10-02-2015
Yes, "sizing" is a substance like starch that is put onto cloth after it is woven to keep it looking nice and flat. It usually washes right out. It is just a thought, but I wondered if that could be the cause of the impermeability. I have personally never encountered that problem. Another problem might be from the speaker board itself on which the cloth is stretched. If it is de-laminating, that might make a noise like that too. If the noise is not present with the speaker out of the cabinet and away from the speaker board and grill cloth, worst case, make a new speaker board and cover it with something better, then remount the speaker with the new board and cloth.
RE: Reproduction Speaker Grill Cloth Buzzing... - bastardbus - 10-03-2015
I did some experimenting tonight and here is some more results.
Just to give specs the speaker is mounted via 3 bolts to the baffle board. That board has the cloth glued to the front edges and lays over the speaker opening. The baffle and speaker are then mounted into the cabinet itself via 3 bolts as well.
-With everything mounted as it should be I get the buzz-vibration about half volume and up depending on strength of the station and volume
-With the speaker removed from cabinet and the baffle there is NO BUZZ at all, It sounds GREAT.
-With the speaker mounted on the baffle board (with the new speaker cloth) but removed from the cabinet I get the BUZZ and it is basically the same as with everything mounted in the cabinet.
-This tells me there is NOT an obvious issue with the speaker or the cabinet themselves. It is when the speaker is mounted to that baffle with the new grill cloth that there is an issue.
-I took a piece of white paper and laid it over my speaker loose from the mount and cabinet and I could replicate the sound almost identical to the speaker in the baffle with the cloth.. I did notice if I laid the paper and completely sealed the speaker off it would NOT buzz at all. Only when the paper was covering the speaker with a small amount of air allowed to move in and out did the paper BUZZZZ like crazy. Thus I am thinking this speaker cloth restricting air movement but allowing just enough to cause a resonance in the cloth and maybe even the speaker cone itself. When something hits a resonant frequency everything starts to vibrate and buzz.
My only other alternative right now is to remove the new grill cloth and replace it with something else or better yet build a new baffle and experiment with with various other materials and see what happens.
I think the new material is restrictive enough to cause this issue with my particular speaker and board. It might not happen with another Philco 80. Mine is very loud and powerful....definitely not a wimpy little radio, she really cranks out. I also found I have no need for the "gimmick" or any other tricks this 80 it is plenty powerful and grabs tons of stations out of the air. I really wish I could get this old girl working as should...she sure is pretty and sounds wonderful for such a small thing.
T
RE: Reproduction Speaker Grill Cloth Buzzing... - mikethedruid - 10-03-2015
You say you "laid" the paper over the speaker board. Did the cloth also just "lay" on the surface for the speaker board ? If that is the case that may be your problem. You need to apply a glue to the whole front surface of the board before you stretch the cloth over it, and make sure the cloth adheres well to the whole surface after it is stretched tight and secured at the edges.
RE: Reproduction Speaker Grill Cloth Buzzing... - bastardbus - 10-03-2015
Mike, if you go back through the thread I covered that info a couple times. The material was glued in place with 3M 77 "just on the edges" until tacky then material attached exactly as the directions said. The material is on the baffle board and it is not coming off without destroying it.
The "paper" thing was a sheet of paper laid directly over the speaker (note NOT the baffle board) as an experiment to see if restricting the air flow similar to the new material and baffle would cause a similar reaction and it indeed did.
Thanks for the help though...
T
RE: Reproduction Speaker Grill Cloth Buzzing... - Warren - 10-04-2015
I think that if you used regular paper it would definitely rattle like that because there isn't much of anywhere for the air to go, it wont really go through the paper so it has to move the paper to get out and in. in concern to the cloth, As MiketheDruid said it could be because you didn't glue the entire cloth on to the backboard, you just glued the edges giving the cloth lots of places to vibrate against the backing. It should be glued entirely onto the backboard not just on the edges... makes sense and its worth a try to see.
RE: Reproduction Speaker Grill Cloth Buzzing... - bastardbus - 10-04-2015
As mentioned before the manufacturer's instructions are very explicit to ONLY apply 3M 77 glue to the very outer edge of the baffle board. Let it tack, then apply one side of the material. pull taught and apply the other edges.
I don't see gluing the entire area down making a difference. If you take a look at the Philco 80 there is a lot bracing and wood details that cover the speaker area that would not be glued down and seem to be the areas of concern. No way to attach the material over the speaker to anything. Should I try anyhow...YES....if I could. There is no way to lift the material off the baffle now that it is glues down. If you have ever used the 3M product mentioned it does not let go easily and would surely destroy the material. Once that happens what difference does it make anymore as I won't be buying another piece of this stuff...LOL So for now, until I find something else suitable to replace it I am leaving as-is and will keep in on the back burner if I find something better to replace it with.
I do think the solution is a different speaker cloth that is better designed for this purpose. I have dozens of large `50s era hi-fis and they all have very similar stiff and very porous materials with large open weave patterns over the speakers. These players are extremely loud and powerful and I have never had an issue with one of those units similar to this. In fact I never had an issue with THIS radio until the original grill cloth was replaced.
RE: Reproduction Speaker Grill Cloth Buzzing... - bastardbus - 10-04-2015
Funny, just doing some searching and apparently I am not out of my mind about the speaker materials being able to pass air through them. Good first paragraph on this page.
https://acousticalsolutions.com/product-category/acoustic-fabrics/speaker-fabrics/?utm_campaign=Product_Type-_Fabrics-_Speaker&utm_medium=cpc&utm_source=google&utm_content=Product_Type-_Fabrics-_Speaker&utm_term=speaker%20grill%20covers&gclid=Cj0KEQjw-b2wBRDcrKerwe-S5c4BEiQABprW-MyiHkuqnYk_MPoaA95yI3_gCZwMUEje7gWCEb8stGIaAgXo8P8HAQ
RE: Reproduction Speaker Grill Cloth Buzzing... - sam - 10-04-2015
how about using a hair brush across inside maybe loosen fabric a little
not a real stiff one but one that has rubber tips on end
RE: Reproduction Speaker Grill Cloth Buzzing... - Warren - 10-04-2015
(10-04-2015, 02:13 AM)bastardbus Wrote: Funny, just doing some searching and apparently I am not out of my mind about the speaker materials being able to pass air through them. Good first paragraph on this page.
https://acousticalsolutions.com/product-category/acoustic-fabrics/speaker-fabrics/?utm_campaign=Product_Type-_Fabrics-_Speaker&utm_medium=cpc&utm_source=google&utm_content=Product_Type-_Fabrics-_Speaker&utm_term=speaker%20grill%20covers&gclid=Cj0KEQjw-b2wBRDcrKerwe-S5c4BEiQABprW-MyiHkuqnYk_MPoaA95yI3_gCZwMUEje7gWCEb8stGIaAgXo8P8HAQ
OK, I still feel if you were able to glue all the material to the backing it would probably stop the rattling, of course you cant glue it where there is no backing but if there is no backing then it isn't going to rattle at that place anyway.
Just to clarify, I wasn't saying the speaker cloth wont let air through it, it actually has to be able to do that. I was saying the paper you put over the speaker doesn't let air through it. Well, Good Luck on this.. If and when you try a few things and find out for sure why it rattles, let us know why. The Best, Warren
RE: Reproduction Speaker Grill Cloth Buzzing... - bastardbus - 10-05-2015
Warren, yes it is obvious the paper won't let air through. I used paper as an exaggerated example of what the cloth is doing as an experiment. If you go back and read my threads I think I stated that I actually left an air opening around the paper (not sealed completely) and it buzzed like a mother. There is no way to really show you how dense the material is via a picture online but it is VERY dense and does NOT allow hardly any air movement through it, unlike the original material which is very porous and almost transparent and designed for maximum air flow. My point was this new material is almost as impermeable as a sheet of paper and indeed both have similar results.
Gluing the entire cloth down now is out of the question without ruining it. I have mimicked gluing the entire cloth down by securing the loose areas with my hands and even a cut piece of cardboard with a circle in the center for the speaker opening to secure the material and I found there is still noise. I am now thinking the noise is not be from the material buzzing against the baffle or cabinet itself but something else. I am wondering if this new material is causing back pressure against and creating resonance in the speaker cone and possibly issues or misalignment of the voice coil and causing voice coil rub, the sound is very similar to that. But again without material covering the speaker, even at FULL Volume and strong signal, the speaker sounds A-1 but the moment you put something that severely restricts air flow over the speaker you get the buzzing. Again still an issue caused by the new material and only remedied by replacing it with a more acoustically friendly speaker cloth.
RE: Reproduction Speaker Grill Cloth Buzzing... - Warren - 10-05-2015
I have to agree, limiting the air that should flow through the cloth is not good and can cause various problems.
RE: Reproduction Speaker Grill Cloth Buzzing... - bastardbus - 10-06-2015
The sad thing is I think I am going to yank this repop stuff and try and re attach the original cloth back in place. It was quite faded and smoke stained and now torn in a couple spots from removing it but the radio sounded GREAT with it in place. It might not look as pretty as the new cloth but I find myself no longer listening to the thing now. I was listening to it every night before.
T
RE: Reproduction Speaker Grill Cloth Buzzing... - stangbuff - 10-09-2015
(10-06-2015, 12:11 AM)bastardbus Wrote: The sad thing is I think I am going to yank this repop stuff and try and re attach the original cloth back in place. It was quite faded and smoke stained and now torn in a couple spots from removing it but the radio sounded GREAT with it in place. It might not look as pretty as the new cloth but I find myself no longer listening to the thing now. I was listening to it every night before.
T
Instead of reusing the old fabric have you considered buying new, acoustically transparent cloth? Speakerworks (as well as your Acoustical Solutions link) sell transparent cloths. The fabric style and color options may be more limited (beige and brown for your radio) but at least you'd have new fabric to go along with a restored cabinet.
I've taken a chance on reproduction material for my 45L and opted for this pattern from Speaker Fabric Supply on Etsy:
https://www.etsy.com/listing/174033848/antique-radio-grille-cloth-fabric?ref=shop_home_active_3
It's a heavier piece of fabric than the original; probably a lot like the one you purchased. The diamonds with the brown flecks within the diamonds are more porous (obvious when held up to the light). Unfortunately I can't provide feedback on its acoustic properties because my electronics restoration is not yet complete. I'm not anticipating problems similar to yours because the cabinet design is much different.
PS Have you considered checking out material at a Jo-Ann Fabrics type store? They will have an ample variety of fabrics on hand and you'll be able to easily identify lighter/less restrictive options.