stupidhead Posted December 2, 2014 Report Share Posted December 2, 2014 Probably not, but I wanted to share the experience. So I was working on a set of 4x and noticed a seperation of the surround on the tweeter frames. A closer look shows after I carefully sliced free any remaining glued surround...then I carefully peel back with a flat edge...and with a dremel and a brush polish up the area...carefully...You may notice, the tweeter screws are out. By taking the screws out, desoldering the wires, removing residual duct seal and directing my work light in just the right direction I was able to easily polish, spin, peel back..polish, spin and repeat with little problem.Then I measured the tweeter (2 7/16") and found a glass with just the right diameter and put some Aleene's under the surround and pressed down with the rim of the glass.and then removed the glass, carefully cleaned the oozed out glue and repressed with the glass to be sure of adhesion. So, what have I learned? I did a set of 4x' last year and if I put some power (Marantz 2325 at 12:00) they had a "snap" to them. hmmmmm.....I wonder if those surrounds were compromised? Link to comment Share on other sites More sharing options...
stupidhead Posted December 2, 2014 Author Report Share Posted December 2, 2014 a couple of additional thoughts, the cone appears to have been treated with the same treatment product that is used on the cloth surrounds. It maybe added to the supple nature of the edges I peeled back for this procedure. The glue that was originally used had sort of crystallized from drying out over the years, and I will be sure to check this area on all future drivers.Also, while I had these out I checked with my meter and got a 4.5 and 4.6 ohm reading from them. Being that I am not schooled in this I am curious if this is correct. I have seen references to these readings in the past but I thought these were 8 ohm speakers. Do my ohm readings on these drivers suggest I have a problem with these? Link to comment Share on other sites More sharing options...
ra.ra Posted December 2, 2014 Report Share Posted December 2, 2014 Yes, the AR-4x is considered to be a nominal 8 ohm speaker, but someone else is better equipped to explain impedance ratings and resistance measurements. I just looked at some notes for several 4x tweeters and I find DCR values ranging from 4.4 to 5.2 ohms on mine. Yours should be fine. Link to comment Share on other sites More sharing options...
owlsplace Posted December 2, 2014 Report Share Posted December 2, 2014 Probably not, but I wanted to share the experience. So I was working on a set of 4x and noticed a seperation of the surround on the tweeter frames. A closer look shows after I carefully sliced free any remaining glued surround.......So, what have I learned? I did a set of 4x' last year and if I put some power (Marantz 2325 at 12:00) they had a "snap" to them. hmmmmm.....I wonder if those surrounds were compromised?Nice job on that. I've seen 4x's with replacement tweeters for probably that very same reason. There will still be issues with centering the voice coil. I believe this is what it looks like underneath:http://img14.olx.ua/images_slandocomua/114007939_3_1000x700_prodam-vch-dinamik-tweeter-ot-kolonok-acoustic-research-ar-4-akusticheskie-sistemy.jpgI'd say you are fine with the DCR ohm reading you have. You will either have a reading or they will be open if they were fried. The tweeter circuit resistance is varied by the potentiometer in the crossover.Here is a diagram from another post (#29): http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7798&page=2Roger Link to comment Share on other sites More sharing options...
ra.ra Posted December 2, 2014 Report Share Posted December 2, 2014 First off ...... belated birthday wishes to Roger - - I saw your mug in the CSP spotlight a couple days ago. I've never dissected one of the 4x tweeters, so the innards are unfamiliar to me, but I think Roger might be raising a valid point about the centering - - I mean, you wouldn't glue down the outer edge of a foam woofer surround before removing the VC shims, would ya? The OP's work looks very considered and skillful, but I'd like to know if the re-glued tweeter is performing well.I may be wrong, but I think the dissected tweeter shown in Roger's first link is not the 4x tweeter, but looks more like the 1-1/4" tweet found in the AR-6, 7, 8 and 4xa models. Three things lead me to this thought: 1.) the proportional (diameter) dimensions of flange-cone-flange are roughly in thirds; 2.) the thin unpainted outer flange perimeter is typical (why?) of this smaller driver; and 3.) the black goop shown at top is leftover from the specially-patented AR electrical tape which covered the tinsel wire leads. The second referenced link is from a thread I started asking for help with an oddball AR-4x, a mildly rare version which uses the older AR-4 woofer and employed two crossover caps. Roy and Kent and others helped me identify the components involved and confirm the schematic sketch as accurate. Those speakers do use the same tweeter as discussed here, but otherwise I'm not sure that particular thread has immediate relevance for the OP. Link to comment Share on other sites More sharing options...
owlsplace Posted December 3, 2014 Report Share Posted December 3, 2014 First off ...... belated birthday wishes to Roger - - I saw your mug in the CSP spotlight a couple days ago. I've never dissected one of the 4x tweeters, so the innards are unfamiliar to me, but I think Roger might be raising a valid point about the centering - - I mean, you wouldn't glue down the outer edge of a foam woofer surround before removing the VC shims, would ya? The OP's work looks very considered and skillful, but I'd like to know if the re-glued tweeter is performing well.I may be wrong, but I think the dissected tweeter shown in Roger's first link is not the 4x tweeter, but looks more like the 1-1/4" tweet found in the AR-6, 7, 8 and 4xa models. Three things lead me to this thought: 1.) the proportional (diameter) dimensions of flange-cone-flange are roughly in thirds; 2.) the thin unpainted outer flange perimeter is typical (why?) of this smaller driver; and 3.) the black goop shown at top is leftover from the specially-patented AR electrical tape which covered the tinsel wire leads. The second referenced link is from a thread I started asking for help with an oddball AR-4x, a mildly rare version which uses the older AR-4 woofer and employed two crossover caps. Roy and Kent and others helped me identify the components involved and confirm the schematic sketch as accurate. Those speakers do use the same tweeter as discussed here, but otherwise I'm not sure that particular thread has immediate relevance for the OP.Thanks for the birthday wish.Probably right on the tweeter photo but it gives the general idea. I didn't know AR patented that tape, gee, I just used regular electrical tape. The schematic was just to show how the tweeter operated in the circuit and that there would be additional resistance from the potentiometer in the circuit besides the measured dcr of the driver putting it closer to the nominal 8-ohm speaker specification. Link to comment Share on other sites More sharing options...
stupidhead Posted December 3, 2014 Author Report Share Posted December 3, 2014 hi guys. thanx for the responses and yes happy birthday Roger! as my original post reveals, the peeled surround on this set was a new experience for me. to further reveal how "newbie" i really am it hadn't even occurred to me the vc might now be misaligned. one of them was entirely separated and the other was well more than half separated from the frame. i do recall thinking how the what appears to be fiberglass cushion under the cone was interesting and didn't give it much other thought. also the edges seemed to be very symmetrically lined up on the metal frame. i did try to eliminate any of the crystallized residue with canned air and vacuum. i don't know how they will do as i have not hooked them up yet but i will let you know as soon as i do.so, if there is a problem can i peel back the edge, play a certain tone through them and re-glue? to answer Robert's question, i would certainly consider shimming, if my research and reaching out for guidance suggested that was the appropriate course. but sadly i just proceeded caution to the wind as it were. i will keep my fingers crossed and let you all know. i defer to those with more experience and i am grateful for this forum. Link to comment Share on other sites More sharing options...
ra.ra Posted December 3, 2014 Report Share Posted December 3, 2014 Roger - - that tweeter pic was informative even if it was from a different speaker model - - I just don't know firsthand if the 4x tweeter is similar in construction since I've never put one under the knife. And yes, about that super special, military-grade, NASA-approved, FBI-sanctioned, fully organic, ion-free black electrical tape - - - well, let's just say that its presence on the baffle board of many models is not my favorite facet of these early AR's. And Geoff, your tweeters may be OK, we just don't know yet....wait and see. I admire your curiosity and industriousness and your restoration work, but I am only adding to the questions on this matter rather than providing knowledgeable solutions. As for shimming a tweeter, I've never heard of this practice, but maybe you can recruit some Lilliputians to do this delicate work. Link to comment Share on other sites More sharing options...
owlsplace Posted December 3, 2014 Report Share Posted December 3, 2014 hi guys. thanx for the responses and yes happy birthday Roger! as my original post reveals, the peeled surround on this set was a new experience for me. to further reveal how "newbie" i really am it hadn't even occurred to me the vc might now be misaligned. one of them was entirely separated and the other was well more than half separated from the frame. i do recall thinking how the what appears to be fiberglass cushion under the cone was interesting and didn't give it much other thought. also the edges seemed to be very symmetrically lined up on the metal frame. i did try to eliminate any of the crystallized residue with canned air and vacuum. i don't know how they will do as i have not hooked them up yet but i will let you know as soon as i do.so, if there is a problem can i peel back the edge, play a certain tone through them and re-glue? to answer Robert's question, i would certainly consider shimming, if my research and reaching out for guidance suggested that was the appropriate course. but sadly i just proceeded caution to the wind as it were. i will keep my fingers crossed and let you all know. i defer to those with more experience and i am grateful for this forum.Thanks for the birthday wish.Interesting project here. The only thing I might add is the voice coil gap needs to be as free from debris as possible. I would have probably used a faster setting adhesive like gasket cement or nitrile and tacked in place and tested before fully cementing the surround. The Alene's may be easier to reverse if necessary though.Roger Link to comment Share on other sites More sharing options...
RoyC Posted December 4, 2014 Report Share Posted December 4, 2014 It is common to find the glue failing around the edge of the 4x tweeter cone. If it is not completely separated, the safest approach is to smear new glue (ie Aleene's Tacky Glue) on and under the cone edge (where it has lifted). Lifting the entire edge for re-gluing does increase the risk of misalignment of the voice coil.Stupidhead's beer glass appears to be a very effective tool for this work Roy Link to comment Share on other sites More sharing options...
stupidhead Posted December 5, 2014 Author Report Share Posted December 5, 2014 And Geoff, your tweeters may be OK, we just don't know yet....wait and see. I admire your curiosity and industriousness and your restoration work, but I am only adding to the questions on this matter rather than providing knowledgeable solutions. As for shimming a tweeter, I've never heard of this practice, but maybe you can recruit some Lilliputians to do this delicate work. And I have now tested them! I unhooked the leads from the amp for the right channel, set balance to the right and turned down volume to zero. Hooked up the leads to one of the tweeters and slowly increased volume, and yes I was certain to have a source playing, in this case a MFSL Hotel California hi res rip from the trusty ipod. As I increased the volume I heard nothing! I increased a little more and still nothing. I started thinking "shit" I have a blown driver here, doesn't matter about the vc! Took the leads and hooked them up to the other speaker and the same thing. You all probably know what was wrong, and I realized I needed the leads to be the speaker end and not from the amp. Hooked up each one properly and am thrilled to announce that both sound fine up to about 12:30 on the Marantz 2230 rig in my work area. Didn't think I needed to go further with them, but you tell me, should I drive them with a little more power?I wonder if it was luck or what. I suspect the fiberglass(?) ring I detected under the cone may have something to do with it all staying aligned.Roger, I did what I could to keep debris from encroaching, but again I suspect the fiberglass(?) ring saved the day and acted like a dam for the debris. The glue seems to be dried up and crystallized contact cement-like residue.Roy, one of the edges was entirely separated to begin with. What measures can I take in the future to assure optimal results? Link to comment Share on other sites More sharing options...
owlsplace Posted December 5, 2014 Report Share Posted December 5, 2014 ....Roger, I did what I could to keep debris from encroaching, but again I suspect the fiberglass(?) ring saved the day and acted like a dam for the debris. The glue seems to be dried up and crystallized contact cement-like residue.....Sounds like hide glue. I hear you can dissolve it with vinegar but have never had the need to myself. I wouldn't crank those tweeters too high out of the cabinet. Roger Link to comment Share on other sites More sharing options...
RoyC Posted December 5, 2014 Report Share Posted December 5, 2014 Roy, one of the edges was entirely separated to begin with. What measures can I take in the future to assure optimal results?Geoff,The gap of this tweeter is relatively wide and forgiving which largely accounts for your success. Shimming with very thin shims after removing the dust cap is the only way to increase the chance of success. Unfortunately, replacement dust caps of this size and type are not easy to find, so careful slicing and re-gluing is required. Whatever, you did a great job!As discussed previously in this thread, it is simply prudent to be concious of the need to keep the voice coil as centered in the gap as possible. The vast majority of these old tweeters are still somewhat attached, so for most folks it is safer to work from the existing position rather than completely detaching it.Btw, the substance on the 4x tweeter cone is a damping compound, and virtually the same stuff as my woofer surround sealant. On many 4x tweeters it is still tacky after 40 years!Roy Link to comment Share on other sites More sharing options...
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