chekov
Member
A few months ago I picked up a pair of vintage Fisher XP-7s from a thrift store.
I was attracted by the solid, beautiful cabinets, woven grill cloth, and intrigued by the strange-looking tweeter. (I think this was the first dome tweeter- preceding AR’s)
When I got them home, I hooked them up to my garage system, and A-B'd them with a set of vintage Marantz HD-66 speakers.
They sounded bad compared to the Marantz. The sound was "hollow" and lifeless.
I tested each of the drivers- they were all working fine (producing sound at least).
I applied a sealant to the inverted cloth woofer surrounds- they still sounded bad.
I sealed the little hole where the tweeter wires exit the cabinet (I used silicone caulk) – they still sounded bad.
They weren’t even good enough to claim a spot next to my garage receiver. I stored 'em away while I decided what to do next.
I could replace the drivers and thereby improve the usability- or, I could keep them stock and preserve the vintage appeal.
I finally decided to open ‘em up- speakers in storage aren’t doing anybody any good.
I cleaned the white crap off of the drivers (I don’t know if that stuff is toxic, but I wore rubber gloves and a dust mask just in case!). I drew a schematic diagram of the crossover & measured the cabinet cut-outs to help select new drivers. I didn’t see any obvious problems (e.g., no leaking caps or loose wires). I got on the ‘net and selected some new tweeters.
That’s when I saw it – “aug 30, 1969” stamped on the crossover. In 1969 I was starting 7th grade- and way too poor to afford speakers like this. In 1969 Hendrix was at his prime and what we call “classic rock” was just called “rock”… I couldn’t do it. I couldn’t separate parts that had been together longer than most marriages. So I put everything back together.
I put some rope caulk behind the woofers & polished the outside with some “Howard Restor A Finish”. They looked better than ever- but they still sounded bad.
That’s when I started thinking- adjusted for inflation, these speakers cost over $1000. There’s no way they could have sounded that bad when new. So what could have changed? I hadn’t seen evidence of leaking caps, so I thought about the drivers. What happens to paper when it gets old? It gets dry & brittle. Speakers are supposed to act like pistons, but to do that they have to be rigid; and vibration within the cone needs to damp out. I decided that a speaker coating which is thin (so as not to add much mass to the driver), stiff, fast-drying (so as not to over-soak the paper) & somewhat flexible (for damping) might help. I’d had good experience with “Carver Tripp Clear Poly” water-based polyurethane for other applications. In addition to the properties above, it dries clear so it wouldn’t negatively affect the appearance of the drivers. I applied it with some artist’s brushes. I applied two coats on each driver, but NONE on the dustcaps. On the cotton tweeter dome, I had to make sure none ran down into the voice coil where it would gum things up.
After letting it dry for a couple of hours, I hooked it up. I felt myself grinning like a lunatic. The improvement was dramatic. I had to keep checking the speaker-selector switch… I couldn’t believe the Fishers were sounding better than the Marantz speakers.
It’s been a week- the coating is fully cured, and the speakers are still sounding good.
Would I try this with a set of speakers which already sounded good? Definitely not- any change to perfection is bad. But in this particular case, at least, I’m sure glad I tried it!
Now my problem is that these old Fishers are too good for the garage; I need to find some space inside.
I was attracted by the solid, beautiful cabinets, woven grill cloth, and intrigued by the strange-looking tweeter. (I think this was the first dome tweeter- preceding AR’s)
When I got them home, I hooked them up to my garage system, and A-B'd them with a set of vintage Marantz HD-66 speakers.
They sounded bad compared to the Marantz. The sound was "hollow" and lifeless.
I tested each of the drivers- they were all working fine (producing sound at least).
I applied a sealant to the inverted cloth woofer surrounds- they still sounded bad.
I sealed the little hole where the tweeter wires exit the cabinet (I used silicone caulk) – they still sounded bad.
They weren’t even good enough to claim a spot next to my garage receiver. I stored 'em away while I decided what to do next.
I could replace the drivers and thereby improve the usability- or, I could keep them stock and preserve the vintage appeal.
I finally decided to open ‘em up- speakers in storage aren’t doing anybody any good.
I cleaned the white crap off of the drivers (I don’t know if that stuff is toxic, but I wore rubber gloves and a dust mask just in case!). I drew a schematic diagram of the crossover & measured the cabinet cut-outs to help select new drivers. I didn’t see any obvious problems (e.g., no leaking caps or loose wires). I got on the ‘net and selected some new tweeters.
That’s when I saw it – “aug 30, 1969” stamped on the crossover. In 1969 I was starting 7th grade- and way too poor to afford speakers like this. In 1969 Hendrix was at his prime and what we call “classic rock” was just called “rock”… I couldn’t do it. I couldn’t separate parts that had been together longer than most marriages. So I put everything back together.
I put some rope caulk behind the woofers & polished the outside with some “Howard Restor A Finish”. They looked better than ever- but they still sounded bad.
That’s when I started thinking- adjusted for inflation, these speakers cost over $1000. There’s no way they could have sounded that bad when new. So what could have changed? I hadn’t seen evidence of leaking caps, so I thought about the drivers. What happens to paper when it gets old? It gets dry & brittle. Speakers are supposed to act like pistons, but to do that they have to be rigid; and vibration within the cone needs to damp out. I decided that a speaker coating which is thin (so as not to add much mass to the driver), stiff, fast-drying (so as not to over-soak the paper) & somewhat flexible (for damping) might help. I’d had good experience with “Carver Tripp Clear Poly” water-based polyurethane for other applications. In addition to the properties above, it dries clear so it wouldn’t negatively affect the appearance of the drivers. I applied it with some artist’s brushes. I applied two coats on each driver, but NONE on the dustcaps. On the cotton tweeter dome, I had to make sure none ran down into the voice coil where it would gum things up.
After letting it dry for a couple of hours, I hooked it up. I felt myself grinning like a lunatic. The improvement was dramatic. I had to keep checking the speaker-selector switch… I couldn’t believe the Fishers were sounding better than the Marantz speakers.
It’s been a week- the coating is fully cured, and the speakers are still sounding good.
Would I try this with a set of speakers which already sounded good? Definitely not- any change to perfection is bad. But in this particular case, at least, I’m sure glad I tried it!
Now my problem is that these old Fishers are too good for the garage; I need to find some space inside.
