Old school stereo

[NW-Bound]

In 1975 my Fisher receiver was stolen and moving to Columbus a few months latter, I purchase a discounted quadraphonic, four channel receiver, at a distribution center. I don't think the concept ever took off. Anybody remember a FM station broadcasting in that mode/band? I think the receiver used a internal skewed equalizer per channel to give the four channel depth effect...not certain though.

You are a few years older than me, but I remember in the early 70s, Sansui and other makers had quadraphonic receivers. I forgot about that until now.

From the Web:

• 4-Channel Output: They contain four distinct amplifier sections to power four speakers, placing the listener in the literal center of the soundstage.
• Built-In Decoders: They feature specialized built-in decoders (like SQ or QS) designed to extract four channels of audio from encoded quadraphonic vinyl records or 8-track tapes

Why did they fail?

Quadraphonic sound was essentially an audio marvel before its time. It ultimately failed in the late 1970s because of competing and incompatible record formats, expensive equipment, and a lack of mainstream content

 

[explanade]

Quadrophonic systems were sold at Sears. Maybe there were high-end audio brands at the time which also tried to sell quad systems but quadrophonic was like home theater in a box at the time, along with the 8-track players those mass-market stereos they sold.

 

[YellowSubmarine]

Quadrophonic systems were sold at Sears. Maybe there were high-end audio brands at the time which also tried to sell quad systems but quadrophonic was like home theater in a box at the time, along with the 8-track players those mass-market stereos they sold.

You're right. My Quad system was from JC Penny's -MCS brand. It served it's ST function until I got some bucks for my Marantz and AR components (1979).

 

[NW-Bound]

Speaking of speaker crossovers, I just found out yesterday that I need to recap the ones inside my pair of Mordaunt Short tower speakers. I listened carefully, and the treble was weak and uneven between the speakers.

This crossover has 3 coils, 4 capacitors. So, one driver has a 4th order filter (24 db/octave), and the other has a 3rd order (18 db/octave). But which driver, woofer or tweeter, has which filter? The enquiring mind likes to know. I will trace it out to see.

But more important is the fact that 2 of the capacitors are cheap bipolar electrolytic type. They are the smaller ones soldered standing up. The blue one has its aluminum case bulging out at the top end. Bad, bad capacitors.

Why didn't the manufacturer use the better type like the two bigger caps soldered laying down (black body, yellow end)?

I am looking for replacement capacitors now.

I just repaired the above crossover by replacing the two electrolytic bipolar caps. Here's the weird thing. Instead of the values lowering, these failed caps have their capacitance increased. The black 6.8uF cap measured 8.3uF, while the blue 12uF cap measured 27uF. I have not seen this before!

I surmise that bipolar electrolytic are made by wiring two electrolytic caps back-to-back in series inside the same case. One section must have shorted out, and that could raise the capacitance 2x if the other cap stayed functional.

 

[NW-Bound]

The above capacitors are in the woofer crossover section, and not in the tweeter section. Then, how was the tweeter "weak" that caused me to notice the problem in the 1st place? By the way, larger capacitance values would lower the crossover frequency. This makes the woofer less loud in the midrange, and extends the tweeter coverage down to lower frequencies than it is designed for. This was not what I heard.

I took the tweeter off the enclosure and examined it. Its coil still measures at 4 ohm. But applying a tone signal directly to it shows that it is indeed "weak", meaning not sounding as loud as it should. What the heck?

Could the magnet get demagnetized somehow? Searching the Web for clue, I came to the theory that it is more likely that the ferrofluid in the air gap has dried up to a tar, and this gums up the voice coil. Oh bother.

I need to disassemble the tweeter to examine it further. On the Web, people have disassembled their tweeter, cleaned out the old ferrofluid and applied new fluid. But while some tweeters are built to allow this to be done, I am not sure this tweeter is amenable to such treatment. Taking it off will likely destroy the dome. Perhaps I can get a replacement voice coil to rebuild it. This, I have not done. I guess this is something to do to spend the time indoor in the dog days of summer.

 

[NameTaken2]

Continuing to see this thread in new posts -a derailment to share that it brings back the clear and very happy memory of the day in 1975 that I went to the dimly lit, small and very cool stereo shop run by hippie dudes and spent my hard-earned summer job $ on a Harmon-Kardon receiver, BIC turntable, and Advent Utility speakers.
Hearing is not so great these days -that setup contributed LOL.
Still have the speakers, re-coned many years ago!

 

[NW-Bound]

More on the saga of the "weak" tweeter.

Yesterday evening, I spent almost 3 hours to restore the tweeter, and was successful. I was able to disassemble the tweeter, and separate the magnet from the 1" titanium diaphragm/voice coil without breaking the latter, which was glued to the front mounting plate of the tweeter.

The magnet gap was indeed filled with ferrofluid, which had dried to a gunk. This disgusting tar is of course magnetic, so it was tough to scrape it out of the magnet air gap, which was 1/2 mm wide. I started out scraping with a safety pin, then later graduated to an Xacto knife blade of 1/8" wide and 1/4 mm thickness. Again, the gunk had ferrous particles so it stuck to the magnet, and I could scrape away a speck at a time.

I looked for a solvent to dissolve or at least soften the gunk. Tried silicon oil, then 3-in-1 mineral oil. The latter worked much better. Near the end, I used a strip of paper a bit thinner than a business card to stick in the air gap to blot out the gunk that was dissolved in oil.

I reassembled the diaphragm and the magnet while the voice coil was driven with a signal to make sure the latter was moving freely in the air gap. I thought about ordering some ferrofluid to put in the air gap, but decided against it. Panasonic was the 1st to use ferrofluid in tweeters in 1979. It was useful to cool the voice coil, and lessen the risk of burning the voice coil under high driven volumes.

My vintage Sansui and Pioneer speakers did not have this terrible ferrofluid. The speakers also predated the foam surround popular with woofers. They had cloth surround suspension; these don't rot like foam surround, but the impregnating elastomeric dope that was put on the cloth does dry out and must be refreshed.

But back on the rescued tweeter. I did a frequency sweep of the speaker after everything got reassembled. The frequency response was reasonable and comparable to the other speaker of the pair which still had a functional tweeter. Initially, I was afraid that without the ferrofluid the tweeter may be louder, and that would make the speaker sound shrill.

By the way, the other speaker of the pair also had bad bipolar electrolytic caps. The measured values were also higher than the specs. At least, something was consistent here. I still don't know why one tweeter got its ferrofluid gum up, while the other stayed OK.

 

[finnski1]

More on the saga of the "weak" tweeter.

Yesterday evening, I spent almost 3 hours to restore the tweeter, and was successful. I was able to disassemble the tweeter, and separate the magnet from the 1" titanium diaphragm/voice coil without breaking the latter, which was glued to the front mounting plate of the tweeter.

The magnet gap was indeed filled with ferrofluid, which had dried to a gunk. This disgusting tar is of course magnetic, so it was tough to scrape it out of the magnet air gap, which was 1/2 mm wide. I started out scraping with a safety pin, then later graduated to an Xacto knife blade of 1/8" wide and 1/4 mm thickness. Again, the gunk had ferrous particles so it stuck to the magnet, and I could scrape away a speck at a time.

I looked for a solvent to dissolve or at least soften the gunk. Tried silicon oil, then 3-in-1 mineral oil. The latter worked much better. Near the end, I used a strip of paper a bit thinner than a business card to stick in the air gap to blot out the gunk that was dissolved in oil.

I reassembled the diaphragm and the magnet while the voice coil was driven with a signal to make sure the latter was moving freely in the air gap. I thought about ordering some ferrofluid to put in the air gap, but decided against it. Panasonic was the 1st to use ferrofluid in tweeters in 1979. It was useful to cool the voice coil, and lessen the risk of burning the voice coil under high driven volumes.

My vintage Sansui and Pioneer speakers did not have this terrible ferrofluid. The speakers also predated the foam surround popular with woofers. They had cloth surround suspension; these don't rot like foam surround, but the impregnating elastomeric dope that was put on the cloth does dry out and must be refreshed.

But back on the rescued tweeter. I did a frequency sweep of the speaker after everything got reassembled. The frequency response was reasonable and comparable to the other speaker of the pair which still had a functional tweeter. Initially, I was afraid that without the ferrofluid the tweeter may be louder, and that would make the speaker sound shrill.

By the way, the other speaker of the pair also had bad bipolar electrolytic caps. The measured values were also higher than the specs. At least, something was consistent here. I still don't know why one tweeter got its ferrofluid gum up, while the other stayed OK.

props for perseverance!

 

[YellowSubmarine]

More on the saga of the "weak" tweeter.

Yesterday evening, I spent almost 3 hours to restore the tweeter, and was successful. I was able to disassemble the tweeter, and separate the magnet from the 1" titanium diaphragm/voice coil without breaking the latter, which was glued to the front mounting plate of the tweeter.

The magnet gap was indeed filled with ferrofluid, which had dried to a gunk. This disgusting tar is of course magnetic, so it was tough to scrape it out of the magnet air gap, which was 1/2 mm wide. I started out scraping with a safety pin, then later graduated to an Xacto knife blade of 1/8" wide and 1/4 mm thickness. Again, the gunk had ferrous particles so it stuck to the magnet, and I could scrape away a speck at a time.

I looked for a solvent to dissolve or at least soften the gunk. Tried silicon oil, then 3-in-1 mineral oil. The latter worked much better. Near the end, I used a strip of paper a bit thinner than a business card to stick in the air gap to blot out the gunk that was dissolved in oil.

I reassembled the diaphragm and the magnet while the voice coil was driven with a signal to make sure the latter was moving freely in the air gap. I thought about ordering some ferrofluid to put in the air gap, but decided against it. Panasonic was the 1st to use ferrofluid in tweeters in 1979. It was useful to cool the voice coil, and lessen the risk of burning the voice coil under high driven volumes.

My vintage Sansui and Pioneer speakers did not have this terrible ferrofluid. The speakers also predated the foam surround popular with woofers. They had cloth surround suspension; these don't rot like foam surround, but the impregnating elastomeric dope that was put on the cloth does dry out and must be refreshed.

But back on the rescued tweeter. I did a frequency sweep of the speaker after everything got reassembled. The frequency response was reasonable and comparable to the other speaker of the pair which still had a functional tweeter. Initially, I was afraid that without the ferrofluid the tweeter may be louder, and that would make the speaker sound shrill.

By the way, the other speaker of the pair also had bad bipolar electrolytic caps. The measured values were also higher than the specs. At least, something was consistent here. I still don't know why one tweeter got its ferrofluid gum up, while the other stayed OK.

Impressive, Congrats... btw...lighter fluid is typically a good solvent we used in the lab for glues, adhesives, neoprene, rubber, etc.

 

[NW-Bound]

props for perseverance!

I don't mind spending a lot of time on a project. What I hate is when, at the end, I have nothing to show for it. In this case, you can imagine how happy I was. Prior to tackling this rebuild job, I already checked out a source for a replacement diaphragm+voice coil, and that would be my next step if the original dome got damaged during disassembly.

Impressive, Congrats... btw...lighter fluid is typically a good solvent we used in the lab for glues, adhesives, neoprene, rubber, etc.

I was thinking about gasoline or kerosene, neither of which I had on hand. I did not think of lighter fluid. I don't know where I could get some now.

 

[Slotracer]

I was thinking about gasoline or kerosene, neither of which I had on hand. I did not think of lighter fluid. I don't know where I could get some now.

Naptha at your local home improvement store is almost the same thing. As mentioned above it works great for loosening/dissolving unwanted gummy stuff and is relatively safe for a lot of base materials. I use it occasionally when rebuilding 90 year-old fountain pens.

 

[Pointby2]

I wish more people would post pictures of their vintage stuff. I don't recognize all the model numbers and I'd love to see them,

So, here's the speakers I've been hauling around the country since 1979. DS940 Design series, designed by Edmond May, who designed many speakers for JBL.

 

[Peter]

Quad ESL63 Electrostatics.

Great speakers, but fragile and high maintenance. Sadly too big for our downsized home and now stored in a closet awaiting their final fate. Whatever that turns out to be.

 

[YellowSubmarine]

I don't mind spending a lot of time on a project. What I hate is when, at the end, I have nothing to show for it. In this case, you can imagine how happy I was. Prior to tackling this rebuild job, I already checked out a source for a replacement diaphragm+voice coil, and that would be my next step if the original dome got damaged during disassembly.


I was thinking about gasoline or kerosene, neither of which I had on hand. I did not think of lighter fluid. I don't know where I could get some now.

b-q lighter fluid works as well.

 

[tizod]

I don't mind spending a lot of time on a project. What I hate is when, at the end, I have nothing to show for it. In this case, you can imagine how happy I was. Prior to tackling this rebuild job, I already checked out a source for a replacement diaphragm+voice coil, and that would be my next step if the original dome got damaged during disassembly.


I was thinking about gasoline or kerosene, neither of which I had on hand. I did not think of lighter fluid. I don't know where I could get some now.

dollar stores have it. Always keep one under the sink. Gets off the dang stickum for all the tags, wine labels (reuse bottles) and more. Cleans many things well. Doesnt evaporate so fast so can soak some items. Great to always have. One thing my kids followed me up on - they have one bottle on each floor, close at hand!

 

[38Chevy454]

Thread tangent: back to those flat panel speakers. I made some for my detached garage. Bought the exciter drivers (4 x $15/ea on Ebay) and a 4x8 sheet of 1 inch thick rigid foam insulation board. I decided on 2 ft x 2 ft size. They do sound quite good, but as was mentioned previously they do lack low end bass. They are also kind of directional, but having four spaced around the garage I have plenty of space for sound distribution for working out there. It is not any kind of audio excellence, just for music when I am working. Used to have some bookshelf speakers, and these flat panel do sound better than those and can get much louder, although I just listen at normal level in the garage. I mounted them on some strong fishing line about 2 feet out from the wall, they don't work as well right next to the wall. Also the driver is mounted at a 3/5 offset in both X and Y planes, physics says this is better than directly in the center. Just thought some of you might like to see the DIY flat panel speakers. Lot of videos on youtube or any internet search if you want to get details on them.

Also my $20 yard sale receiver that powers the speakers. Not real vintage, but does the job for cheap. Less than $100 in the whole system.

 

[YellowSubmarine]

Thread tangent: back to those flat panel speakers. I made some for my detached garage. Bought the exciter drivers (4 x $15/ea on Ebay) and a 4x8 sheet of 1 inch thick rigid foam insulation board. I decided on 2 ft x 2 ft size. They do sound quite good, but as was mentioned previously they do lack low end bass. They are also kind of directional, but having four spaced around the garage I have plenty of space for sound distribution for working out there. It is not any kind of audio excellence, just for music when I am working. Used to have some bookshelf speakers, and these flat panel do sound better than those and can get much louder, although I just listen at normal level in the garage. I mounted them on some strong fishing line about 2 feet out from the wall, they don't work as well right next to the wall. Also the driver is mounted at a 3/5 offset in both X and Y planes, physics says this is better than directly in the center. Just thought some of you might like to see the DIY flat panel speakers. Lot of videos on youtube or any internet search if you want to get details on them.

Also my $20 yard sale receiver that powers the speakers. Not real vintage, but does the job for cheap. Less than $100 in the whole system.

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Good job, good find! I had some flat panel auxiliary speakers on my computer system in the 1990s. I liked the small footprint, had a power woofer on the floor. The speakers came with the old computer system. I didn't realize we still had them around. I haven't used them for many years...fwiw 8 ohms

 

[KevinZ]

The Musical Fidelity Tri-Vista 300 Limited Edition, only 500 units were produced worldwide.
And a pair of Martin Logon's.

 

[ERD50]

Thread tangent: back to those flat panel speakers. I made some for my detached garage. Bought the exciter drivers (4 x $15/ea on Ebay) and a 4x8 sheet of 1 inch thick rigid foam insulation board. .....

View attachment 64866

That's pretty cool. I have watched some of the DIY builds of these types on youtube. They share some characteristics with the flat panel speakers like Martin-Logans, or Magnepans (entire surface radiates sound, no 'box', so also no deep bass), but are also very different, in using a driver mounted to the diaphragm, vs the whole diaphragm being active on its own.

Sounds like they are serving the intended purpose for you. I really want to build some, just for the experience.

 

[Slotracer]

I really want to build some, just for the experience.

Yes! I spend a bit of time in the garage (too much?) and have music playing much of the time. Typical 80s or 90s 12" speakers (don't remember which brand) from the Restore in the back, pushed by a thrift shop Pioneer tuner/amp playing the local college radio station or mp3s off an old cell phone. Thinking about getting another pair of speakers for the front corners, but making four might be more fun.

 

[YellowSubmarine]

Back in the 60s, we had two stores for 'build your own' stereo (and electronics) system. Olson and Heathkit...both predate Radio Shack in Western PA. For $8.00, I built 2-way speakers in "walnut" cabinets. They sounded great with my reel-reel. I screwed up by connecting these to my bass guitar system...the voice coils just dangled there after a minute or so. I may had invented the first guitar fuzz box -missed opportunity you might say.
if interested in the Olson story...https://www.youtube.com/watch?v=v1jy10oDT-c

 

[NW-Bound]

I first learned of the audio transducer exciter from a YouTube channel called Tech Ingredients. The YouTuber raved about it as the "world's best speaker", but I was of course dubious. Still, it had to be reasonably good, more than one would expect. Thought I would experiment with it, but then promptly forgot. Too many things to investigate!

Just now, searched YouTube and found a channel called AmplifyDIY. This man did a fairly good evaluation of different panel arrangements, and what was impressive was that he recorded the test sessions with binaural microphones, and the actual recordings in this YouTube video should be heard with a headphone. The panels sounded quite reasonable, although I suspect they colored the sound in a pleasing way by generating even harmonics.

FWIW....

PS. It makes me wonder if one installs many small transducers over the entire panel, would that be equivalent to an electrostatic speaker or a Magnepan?

Back in the 60s, we had two stores for 'build your own' stereo (and electronics) system. Olson and Heathkit...both predate Radio Shack in Western PA. For $8.00, I built 2-way speakers in "walnut" cabinets. They sounded great with my reel-reel. I screwed up by connecting these to my bass guitar system...the voice coils just dangled there after a minute or so. I may had invented the first guitar fuzz box -missed opportunity you might say.
if interested in the Olson story...https://www.youtube.com/watch?v=v1jy10oDT-c

As a kid I spent hours drooling over Heathkit and Allied catalogs. Never heard or knew of Olson though.

 

[38Chevy454]

The only drawbacks to my flat panel speakers are:
1) They do not make good low end, for a better sound you need to add a subwoofer.
2) They are directional, I think more than a traditional speaker.
3) Without any finishing work on the rigid foam they are not exactly like nice wood finished cabinets. You could paint the foam or maybe cover with fabric if you wanted to look better. I did not even sand the cut edges or do any attempt to improve the appearance.

The advantages are:
1) Very low cost
2) They seem quite efficient and do not need a lot of power for the output volume.
3) Sound is (to my ears and in the less than optimum garage open space) quite clean.
4) The sound comes out both sides, so being spaced form the wall helps the reflected sound better.
5) Very light weight vs traditional speakers, especially using the rigid foam panel. You can actually use a lot of different materials the key being it has to be stiff and not flexible.

So try building some for those interested. It's an easy project that also has low cost. No special tools required. Since the whole panel moves, you can't mount them solid on the edges. That is why mine hang from the strong fishing line; and also out on the 1x2 extension pieces to space away from the wall.

 

[ERD50]

.... So try building some for those interested. It's an easy project that also has low cost. No special tools required. Since the whole panel moves, you can't mount them solid on the edges. That is why mine hang from the strong fishing line; and also out on the 1x2 extension pieces to space away from the wall.

From a physics view, I'm thinking that one should add a lot of weight to the back side of the driver(s), then hang the speaker from that added mass. When you hang the panel, the only thing opposing the force of that driver pushing/pulling the panel, is the mass of the driver (think equal/opposite reactions). The panels are light, so when the panel is pushed out (forward, toward the listener), that driver gets pushed back a slight amount.

But when he tried to mount the drivers to some supports, that's going to radiate vibrations into those supports, and that can cause some unwanted sounds radiating from those surfaces (which is why high-end speakers attempt to dampen the cabinet, even building in a gap filled with dry, loose sand).

That's why I think added mass, then hang from that mass to keep the vibrations from 'leaking' anywhere, would be a good approach. Whether any of that would make an audible difference is a whole 'nother story, but I think the physics of it is correct. I'd play with it, but I already have a list of projects to work on.

 

[YellowSubmarine]

Here's an elaborate version of a bone vibrator that's specified for audio and panel application. It has a 20-20k response curve. I'm sure there's many limitations to this device, but it's worth mentioning. In my former industry, audiology and deaf education, bone vibration was a media for hearing testing and therapy. Again, this is a take-off on the concept of transposing sound energy to vibration and on to audio waves except here we will apply the transducer to various, selected materials for sound field listening. This is very similar to the electrostatic approach. The vibrators we utilized had frequency limitations of 250 - 5000 Hz; but this one goes well beyond. I have no experience with this linked product but it seems interesting for a $70 experiment.

https://www.ebay.com/itm/314073301421?chn=ps&mkevt=1&mkcid=28&var=612737332138&google_free_listing_action=view_item&com_cvv=8fb3d522dc163aeadb66e08cd7450cbbdddc64c6cf2e8891f6d48747c6d56d2c