Need speaker repair advice
3I have a pair of old Fisher speakers that have rotted foam surrounds, and I want to replace them. However, the foam surrounds are u-shaped, and all the surrounds online that I’ve seen are n-shaped. Further, the foam rotted out around passive radiators and not on electrically powered drivers. I’m thinking the u-shape might be kind of important for a passive radiator. Does anyone know if this is the case? Do you think a standard n-shaped surround would work ok, or could it be too rigid and decrease the effectiveness of the radiator? I’m currently using making tape to hold the radiators in place, but it doesn’t stick very long. Here’s some pics of what I’m asking about:
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My two cents, from an audio dork with some schoolin’:
If you want to traumatize yourself with detail, https://en.wikipedia.org/wiki/Thiele/Small_parameters
we’re talking about how important matching the suspension resistance/compliance is. My intuition says ‘not terribly, and it must be better than tape.’
For bonus calculus points, you could probable compute the sensitivity of changing those values impacting frequency/phase response.
I did a similar swap on a subwoofer and it was definitely not noticeable.
Happy to be educated if there is an audio engineer around to tell me I’m all wet.
@kizen99 Good advice!
Also- If the passive surrounds are going, I’d inspect the speakers closely also.
@kizen99
Thanks for that. You’re definitely right about a surround sounding better than tape, but they actually sound pretty good with tape. It’s just that tape is temporary, but a glued surround might as well be permanent
@daveinwarsh
The surrounds weren’t going - they were long gone. Fortunately, the drivers seem to be in great shape.
@eonfifty There are some adhesives for this specific purpose - they aren’t easy to remove, but it is possible without destroying the whole thing.
Something like: https://reconingspeakers.com/product/white-latex-glue-1-oz-bottle/ would be a lot more forgiving than using superglue (cyanoacrylate.)
@kizen99
That looks like the same glue that’s included with the kit I was looking at. I’d imagine super glue would be a poor choice given it’s lack of flexibility…
@eonfifty I’ve fixed several pairs of speakers with the DIY surround kits with good results. They come with the correct glue. I suppose you could flip the surround upside down to make it match. The minute difference in box volume shouldn’t matter though.
Make sure if you buy a kit it is the correct diameter, because some manufacturers made odd size drivers. I had to get a specific kit for some 60’s JBL’s. After replacing the rotted surrounds, they sound great.
@kizen99 This makes a lot of sense to me.
If you need a source for parts/speaker components try: parts-express.com or https://www.newark.com/
@bluebeatpete
Unfortunately, I can’t flip them because the cone is angled without a flat rim. Another issue could be that the cones are rear mounted. It’s possible that n-shape, with the correct diameter, will hit the cabinet opening edges:
¯\_(ツ)_/¯
@bluebeatpete @eonfifty Kits are available for both flat and angled cone edges.
@eonfifty @kizen99 You are correct, super glue (cyanoacrylate) is a no-no! Most outfits sell refoam kits including proper glue, or it can be purchased separately.
Any pointers to troubleshooting a subwoofer that insta-blows the fuze?
It’s a 10" sub from Pinnacle Speakers.
I’m handy with a probe and a soldering iron. I’ve not seen any circuit diagrams or anything for it. Don’t know where to start, so any guides?
@mike808 I would start with ohm reading on the speaker itself. Move it around some - if it goes to zero (or <4, say) you have a short there. If it seems good, you are probably in amplifier black magic land.
@mike808 I assume it’s a powered sub with integrated amp. If so, pull the amp out and look for burned up components or darkened areas on the pcb. Check the power supply first, that’s usually the culprit. If it’s old school technology, hopefully it’s just a diode or regulator out. If it’s not the power supply, it’s likely a FET (the chips that make music louder). If it’s a FET you should replace the pair.
If it’s a newer class D amp, I have no experience or advice.
Good luck!
@mike808 My approach is to replace the driver, and while it’s very nonscientific and maybe a little wasteful, it hasn’t failed me so far.
@bluebeatpete @mike808 I’ll second this.
You have a power-ground short and if you open the thing up it might be obvious what the problem is. There might be a frayed wire making a contact somewhere. There might be corrosion on a PCB causing a short.
Check the power supply. Also, examine capacitors for any bulges. I think capacitors usually fail open, but it is possible for them to fail short. There is likely an inrush current limiting capacitor somewhere on there near the power supply.
Also, make sure you’re using the right fuse.
@bluebeatpete @Limewater I have replaced the fuse multiple times to no avail.
I just wasn’t thrilled at taking the thing apart in yet another project. Was hoping procrastinating would allow the problem to resolve itself. No luck on that approach either.
@bluebeatpete @mike808 I just meant make sure you aren’t replacing it with one of the wrong voltage or current rating. I mean, you probably aren’t, but you’ll feel really silly if you take the thing apart and then finally realize that was your problem all along.
Try www.simplyspeakers.com
@margav
I checked them, and they have a size I can try. But I think I’m going to order from speaker works.com. Their SWK8A has the closest dimensions (only off by a 16th or a few 32nds of an inch) to what I’m working with.
speakerworks.com that is.
/giphy stupid auto correct
I’ve done many foams. Yup angle attachment ( vs flat) to the cone. If first timer, there are on line videos, take your time, call them if needed, another option, https://www.midwestspeakerrepair.com/
https://www.simplyspeakers.com/
@gfreek I can second Simply Speakers. I’ve been ordering from them for years and they’ve always been great. Same with Parts Express!
I recently refoamed my beloved 30 year old NHT SuperOnes. Worked beautifully.
An observation - the foam was very soft - that is - not stiff. I’d guess the geometry of the foam will matter little to the performance.
And since the foam is so soft, you might find that even if you have a flat vs angled (or visa versa) mounting surface, you can get the foam to lay flat on the cone.
Patience is your friend - in removing the prior adhesive and gluing the new foam.
BTW, I was pleasantly surprised to learn NHT has actually been extracted from the brand collector whores… and is back in independent founder hands.
They even do “factory” refoams.
But unlike the past, they focus their distribution thru home theater installers and on Amazon.
@RedOak
Removing the old stuff is another concern I have. I’m hoping any instructions will describe how to do it. Otherwise I’m going to try isopropyl alcohol and a toothbrush to clean up the cone.
@eonfifty @RedOak Much of the old rotted foam can be removed by hand (tip: do this outside) and what’s left will come off with gentle use of a razor, utility knife blade, etc. For remaining residue, you can use isopropyl (rubbing) alcohol or Goo Gone, depending on the surface type. (As always, try to test first, to ensure you won’t damage the surface!)
@eonfifty I used a brand new sharp xacto knife and isopropyl alcohol.
The scraping action was to wet the the remaining foam/adhesive whilst holding the blade edge perpendicular to the cone surface.
You have to be very careful when scraping with the blade parallel to the cone surface that you don’t slice into the cone.
But don’t over work it or you risk damaging/softening the cone material.
Patience. Patience. Slowwww.
And unless your voice coil suspension (the place where the cone is driven by the magnet) is fairly stiff, be very careful when glueing the new foam to keep the cone centered in the frame.
I’ve heard some kits come with jigs to center the cone.
Oh, and in case it wasn’t obvious, the pads on top of the foam have to come off carefully if you’re reusing them. All the foam should be scraped off the frame as well.
@RedOak
Centering should be fun as there is no voice coil. It’s a passive radiator, so it’s just a paper cone that will be glued directly to the inside of the cabinet.
@eonfifty @RedOak Actually since you’re not working with the tight tolerances of a voice coil inside a polepiece (magnet), refoaming a passive radiator like yours is much simpler. There’s no need to make sure the cone is perfectly centered…it will work just fine as long as there’s no air leaks!
@eonfifty @PooltoyWolf agreed - much easier! All you need is more acoustically proper Saran Wrap sealing that hole.
@PooltoyWolf @RedOak
Acoustically proper Saran wrap?
/giphy Acoustically proper Saran wrap
Do you have a model number for these speakers? My eyes can’t really tell from looking at the images, but the active driver in your photo appears to have a treated fabric surround on it, which under normal circumstances should never rot or fail. As for the passive radiator, some of those have really weird surround dimensions, and it may actually be easier to replace the entire radiator itself instead of trying to find a refoam kit to fit the cone and frame. On your speakers, was the foam for the radiators attached to a frame that unscrews from the speaker cabinet, or attached directly to the cabinet opening itself? I’ve refoamed many speakers myself, so I’m happy to lend a helping hand or two.
@PooltoyWolf
Unfortunately no, there is no model number. I’ve searched everything printed on the speakers with no results. The only thing that resembles a model number is MN298 which is printed on the insides of the cabinet. And there is no frame. They are glued directly to the cabinet, which might be noticable in this picture after the old surround was removed:
@eonfifty These look like they may be one of Fisher’s AirDyne line of speakers; is there a badge on the front grilles saying such? Sometimes there’s a date stamped somewhere on the cabinet. The good news is you were able to access the inside of the cabinet from the rear…a lot of these types of speakers are glued together. This means you can actually replace the surrounds on the radiators, as long as you’re able to find a pair that are the right size. (I have never glued surrounds directly to particle board/MDF, but I’m sure there’s a suitable glue that will stick.) You could actually try using staples or small tack nails to secure the surround to the cabinet after gluing it to ensure a seal.
If you do want to replace the entire radiator, it will be more expensive, but that’s also doable, provided there’s a radiator available that’s a fit for the openings in your cabinets. My personal choice would be to attempt a refoam first.
@PooltoyWolf
There is no badge or anything like that, but I searched images of AirDyne and saw a few that were similar, so that’s probably what they are.
@eonfifty Keep me informed if you need more help on these, I know you can do it
Let us know how you make out…
I ordered some surrounds yesterday, and they should get here sometime next week. I’ll do my best to document and post the repair process. Thanks for all the tips and replies
Update: The surrounds arrived today, and the cone-to-surround glue is setting on the first cone now.
I used an xacto knife to scrape the old surround off. After that, I used a paper towel soaked with alcohol to clean up the edge. It softened up the old adhesive enough to scrape it off, but I was also damaging the paper cone, so I left the majority of it on. The instructions said leaving the old adhesive on is ok in most cases.
As for the surround-to-cabinet part, I’m not going to be able to see if the surround is centered on the opening without taking off the fabric from the front of the speaker, and I really don’t want to do that, so I’m planning on centering it by feel and then marking the centered surround’s location with a pencil and use that as a guide when I glue it. I spent the extra dollar for the fancy glue (probably contact cement), and I think it will work fine for adhereing to the particle board cabinet. Also, it feels like n-shaped surround won’t rub against the opening. Yay!
I just checked the glue, and I think it’s set enough to proceed installing the radiator in the cabinet, but I’ve had a few beers waiting for the new goat to post, so I might wait until tomorrow.
/giphy wait until tomorrow
I couldn’t wait. It’s not perfect being off by a 16th of an inch or so, but at least the roll of the surround doesn’t touch the opening in the cabinet.
