Look into my eye... Fisher XP7 refurb

Here's step one of rebuilding my Fisher XP-7 speakers. We've been talking about their relative merits in the speaker forum. My take is they are tube-amp speakers and not up to modern high-power stuff. Still, they have a coolness and they're original, so we'll see what we can do to get them back in working order without buying any new parts.

I'm not sure if the sound will be worth the effort, but we're going to try!

First off is the orange-eye dome tweeters. They're assembled with nothing more than tape, which has long ago lost all adhesive. The suspension is short strips of rubber, now hard and brittle.

I popped off the side caps by gently prying under the lip with the point of a knife. A small pad of insulation was glued in on both sides, the only glue I've found so far that still held!

Here's a pic showing the internals. Next step will be to remove the tape and get the dome out of the basket so we can glue in new rubber strips.

-Ed

Over easy

The tweeter above was overheated, this caused the rubber to melt and stick. So I moved on to the other one. The dome was tilted and stuck in that position but the rubber was a little more live. There was evidence of the coil rubbing but it didn't wear through.

Once apart, you could see what was left of the odd little rubber suspension. Looked like an octopus with all its tentacles chopped into Vienna sausage. The inside of the dome was filled with neatly cut disks of insulation.

All the kings men...

...had the weekend off. Here's all the pieces of the tweeter.

Sunny side up

Thanks to another thread here, I learned these are supposed to have an outer surround. A ring of chamois was used as a replacement and no attempt was made to replace the octopus with anything as all I could think of for that was a condom and I was fresh out!

The chamois let the cone move quite freely. The sound was nice for a midrange but not for a tweeter, so I stiffened the chamois with a coat of Vinac. I don't have a properly working original to compare it with, to me it is still a bit subdued in volume, but it seems to work fine.

Here it is back in the cabinet.

Ok!

A shot of the entire front, with handwritten inspection "OK."

That was then, this is now. We still have the woofer and maybe a midrange to disassemble and repair next session.

I had a good listening session with them today, with substitute tweeters installed. They were actually brighter-sounding than most of my speaks. With the dome back in, it is a much closer match to the XP7B but is still a bit weak in the bass. It also seems slightly more efficient than the B.

My opinion of it keeps changing as I listen to different things on a couple amps, not to mention the tweeter alterations. I'm liking them more as I go, but still doubt it could keep up with the NS-500's on the big system. As I dig further into it, looks like overdriving is what got them into the shape they're in. One is definitely worse off than the other.

This model has no level adjustment, while the B has a 3 position switch. The cabinets are identical in size but again the B has some added detailing that helps set off the front better.

Next time we'll also take some pics showing the differences between the drivers in the XP7 and the XP7B.

-Ed

wrap it up

Nobody seems to care much about this XP7 thread so we'll post the comparo shots and call it a day.

In all cases the XP7B is the better-looking part. Um, the painted ones.

The XP7's woofers just have weak spiders so I should be able to get them going without hassle. One egg tweet is still stuck, but if we keep these they will go anyway. Ron's sending me his so there's still a chance to make up a pair of working tweets.

One inductor came loose, so we have to check that out too. That's about it for the internals on these two similar but very different speakers.

The woofers:

the mids...

The crossovers... [EDIT] Shown first is the XP7, then the XP7B, finally a crude schematic of the earlier XP7. Can't wrap my mind around the reversed woofer polarity.

-Ed

Interesting

Hi Ed.

Looks to me like you are a patient man who also takes great pride in both servicing and restoring vintage equipment. Good thread and good work done.

I doubt that there is a lack of interest in your work. I do not vit DIY often and opened your thread only out of curiosity as I had no idea of what a Fisher XP-7 was.

Perhaps if it had been posted in the speaker forum you might have got a few more people looking at it. If I were you, I would ask the admins to see if your thread can be moved to the Speakers forum, where I think it belongs. You may find that you will help some others with similar spkrs or at least find more people are interested in your work than you think.

Regards,
Joe

Ed,

Did you take that little octopus thing completely off the tweet, or just leave it as it was?

Thanks,
Clay

Hi Joe,

Thanks for the reply. I'm anxiously patient I guess. I can wait a long time but when I'm ready to go, I'm full tilt. Drives my wife nuts! I mentioned in another thread I'd be posting the Fisher info here, maybe just adding a link there would be what's needed.

It's a speaker battleground here, got 4 pairs and a couple oddballs I'm testing now. Rebuilding my Yamaha NS-500's too.

Clay, I removed the octopus. Didn't see any way I could rebuild or fabricate anything like it. With the rubber gone the voicecoil gap is pretty big. I tried to make up for the missing compliance by slightly stiffening the chamois. The rebuild just had way too much travel as it stood.

It has a nice, smooth sound but is weak in output compared to the other drivers in the XP7. The crossover is next on the list to see if there's leaky capacitors or other issues besides the inductor that's hanging free.

-Ed

Ed, it may not be a lack of interest as much as letting you finish your thread out. Many times, if people start butting in and commenting, it turns off topic and the thread isn't nearly as useful as a DIY thread. This has happened in the past, so most mambers just respectfully peek in and see how it is going and wait till it's done to comment.
I personally am in awe of you taking the tweets apart :jawdrop: , gives me insperation to break a few of my speaks while trying to fix them.

Thanks, VJ, guess I derailed my own thread... ;-)

The complicated stuff's about done, I'm swapping some speaks in to see if there's any difference.

I put the XP7B woofer into the XP7 box for a day or two while I was working on the original woofer. At low volumes, the two woofers sound about the same, but I give the nod to the newer version for a bit stronger and lower bass.

Wiped the powdered corrosion stuff off the basket and gave it a spray of clear-coat on the back so it could be handled without spreading that stuff all over. The mids are covered with this junk too.

Got the woofer's spider stiffened up a bit with multiple applications of Vinac, which is special beads of PVC dissolved in Acetone. This still didn't stop it from bottoming too easily with the finger test. I'm wondering what the bottoms of the voicecoils look like, but haven't gone that far yet. Installing them into their sealed cabinets doesn't stiffen things up much more either, so I've still got my doubts these will serve in my big system.

Swapped in a more modern mid and tweet last night, now we're starting to change the sound.

I've tried rebuilding tweeters before and never had much success till just last week on one of the XP7B's tweets. That gave me the confidence to tackle the fried egg tweets.

On other fronts, I got the Yamaha NS-500 woofer reconed successfully and gave that its first test last night. Then I rebuilt a brand new $10 woofer that wasn't aligned properly from the factory, figuring it would cost almost as much to return it for exchange as I'd paid. Got lucky on that one and was able to hide where I sliced it apart behind the giant dust cap.

Getting closer to doing some serious listening tests. I'm playing with 5 different pairs of speakers I hope to narrow down to two pairs. But it's been real hard deciding which ones, since I want to keep them all. The wife's already figured she'll come home from her trip to find quad stacks in the living room, so this could work out well! ;-)

-Ed

Great thread! Now I'm prepared to take on my XP-7s!!! Thanks, Man!

CU, Glad it was of some help! Stick around, we're not done yet. I'm beginning to wonder about the project. Guess I was hoping it would be a couple easy fixes and on to the listening. Looks like we'll have to go into everything in both speaks before we can call it good.

I decided at least one of the woofers must come apart, it still rubs and travels too far too easily. The other one doesn't rub but is also "floppy." This is probably from being overdriven for too long, just flexed out to the max.

I'm messing with the XP7B at the same time, looked into its crossover last night. Looks like it's a 4-way, as the two mids each have their own capacitor and inductor. The tweeters are in parallel but have a resistor in series besides the control on the back. One of the mids is shot and will need a rebuild too. I've already repaired one of the tweeters in this speaker. I have no mate for this one, but if it compares well once we're done, I might look for another of those and let these XP7's go.

[EDIT] Added pics of the XP7 and the XP7B in as-received condition, then the XP7 cabinets as I've modified them. I used the B woofer along with a nearly matched woofer a friend had, new (non-matching) tweets and the original alnico mids. I made a couple changes to the crossovers as well.

-Ed

Nice work on the Fishers. You are obviously an exacting tech.

Which NS-500 set do you have? The 2-way with the Be dome tweeter or the 3-way with non-Be domed mid/tweeter? If it is the 3-way, can you post a pic? Thanks.

Thanks, YB-2! Don't know how exacting I am, but with speakers, I just go slow and careful. Had too many quick jobs go bad! It's probably a good thing I don't have to bill anyone on this, just trying to please myself.

I can gut 'em and get 'em back together easy enough. The real challenge is hiding the fact and having them work right afterwards. Sometimes you can only have one or the other, in which case I'll take working every time!

Edit: Forgot to say my NS-500's are the two-way. I believe these must be the Beryllium tweets. Unfortunately, they were blown and are hidden in a box somewhere in my shed! I have a map I got from a grizzled old fortune-teller. Treasure hunt and tweeter rebuild planned soon.

-Ed

If I knew how to post multiple pics in one message I would

But I don't, so I just change my avatar! That's the Goodyear Rubber Band, by the way.

Well, tore into the woofer tonite. The rubbing and bottoming got to me.
First we slice the dustcap off as it might tell us something that would avoid a total teardown.

This one is see-though fabric, so I can't make a hidden index cut. Instead, I put a piece of tape on it to help realign it later. Usually the cut wavers enough that parts can repositioned using only the slight curves and notches as a guide.

Makes for a better post total anyway

By flexing the cone far enough upwards that we clear the voice coil gap, we see what the problem is. The hammered coil edge has folded inwards. The arrow on the tape points it out.

How to proceed?

Here's how I flexed the speaker outwards to inspect the gap. Note the extreme flex this cloth surround allows.