Need some advice on restoring old speakers

[Namakwalander]

Hi there

This is my first post in this forum. Apologies if it is in the wrong section or if I should have made my first post elsewhere.

Anyway. I got some old Pioneer speakers that I am looking to restore slightly to replace a set of (what I believe to be) Chinese speakers currently in use in my house.

What they look like. Old Pioneers.


Stands are disintegrating.


Some chipping in the veneer.


The speaker and tweeter.


I have listened to the radio on them (in my garage) and they are not bad. Would love to try them in the living room if my wife allows me to carry them in (they are huge), but would like to fix the stands and chipping first. Also sand and put some varnish or something.

I have some questions:
1. The high pass for the tweeter has a cap that is only marked "4". I am assuming this is 4uF which would give this high pass filter a cut off of around 8000 Hz. Does that sound right? And can I replace the cap with a new bipolar electrolytic from Communica, assuming that it is out of spec after all these years? The speaker is a paper cone with ribbed paper suspension (not sure about all the correct terms).

2. At some point I would like to try my hand at making LC filters for both the speaker and the tweeter by winding my own coils, but I have no equipment to test the inductance. How accurate will my filter be by just following an online calculator for a coil and just building it?

3. Would there be any benefit in replacing the speaker and tweeter at a later stage for wider frequency range, using cheap-ish off the shelf speakers (I think I know the answer to this one)?

4. Anything else?

Thanks for letting me join and looking forward to the replies.

 

[mygoggie]

Looks like a good project to understand speaker cabinet design and building.

If you want to fix the veneer, there are only two real ways. Use a filler and paint the cabinet or remove a strip around cabinet and replace this with a darker veneer to form a “frame”. If you want to restore to the original splendour you will need to replace all the veneer.

@Family_Dog will know more about the caps etc.

Most importantly, the fact remains that you must have fun with this project!

 

[Namakwalander]

Looks like a good project to understand speaker cabinet design and building.

If you want to fix the veneer, there are only two real ways. Use a filler and paint the cabinet or remove a strip around cabinet and replace this with a darker veneer to form a “frame”. If you want to restore to the original splendour you will need to replace all the veneer.

@Family_Dog will know more about the caps etc.

Most importantly, the fact remains that you must have fun with this project!

Thanks for the reply.

I don't think I will be able to do a perfect restoration, and that is not really the plan, but I have an idea (seen in a YT video) to repair the veneer with filler and various colours of wood stain. Well, I am going to try. I have already soaked all the chipped areas with thin super glue to prevent any further damage.

 

[mygoggie]

Just use some thinned down artist acrylic to paint over the filler. Much easier and cheaper.

 

[Family_Dog]

I have some questions:
1. The high pass for the tweeter has a cap that is only marked "4". I am assuming this is 4uF which would give this high pass filter a cut off of around 8000 Hz. Does that sound right? And can I replace the cap with a new bipolar electrolytic from Communica, assuming that it is out of spec after all these years? The speaker is a paper cone with ribbed paper suspension (not sure about all the correct terms).

Sounds about right, the replacement cap would be highly recommended after all these years.

2. At some point I would like to try my hand at making LC filters for both the speaker and the tweeter by winding my own coils, but I have no equipment to test the inductance. How accurate will my filter be by just following an online calculator for a coil and just building it?

First decide on which speakers you will be using, find a suitably matched crossover and you can certainly try your hand at winding your own coils but I would suggest getting a Digital Meter that can guide you in measuring inductance accurately.

3. Would there be any benefit in replacing the speaker and tweeter at a later stage for wider frequency range, using cheap-ish off the shelf speakers (I think I know the answer to this one)?

While Pioneer had some pretty good stuff in the past, their range extended from budget to high-end so yes, replacing the drivers with higher quality units would be a wise move. In this case, your cross-over needs to be purposely designed to match the new drivers. But don't rush into it, experiment with what you have, enjoy the sound and if you then still feel the need to upgrade, do so.

-F_D

 

[Shonver]

I have a further suggestion wrt the chipped corners: route out a square section and replace it with solid wood, glued in. Some furniture makes use the inverse of this to create a solid wood effect. They use an MDF or chip-board core, add solid wood edging, then veneer over it. So the exposed edge is proper solid wood.

With regards to the crossover, it might be possible to improve on this design with a re-engineering of the crossover. However, it is probable that in this case the crossover simplicity is correct for the chosen drivers and intended level of performance of the product.

 

[Namakwalander]

Sounds about right, the replacement cap would be highly recommended after all these years.


First decide on which speakers you will be using, find a suitably matched crossover and you can certainly try your hand at winding your own coils but I would suggest getting a Digital Meter that can guide you in measuring inductance accurately.


While Pioneer had some pretty good stuff in the past, their range extended from budget to high-end so yes, replacing the drivers with higher quality units would be a wise move. In this case, your cross-over needs to be purposely designed to match the new drivers. But don't rush into it, experiment with what you have, enjoy the sound and if you then still feel the need to upgrade, do so.

-F_D

I am very sure that these were on the budget side of the spectrum.

 

[Namakwalander]

I have a further suggestion wrt the chipped corners: route out a square section and replace it with solid wood, glued in. Some furniture makes use the inverse of this to create a solid wood effect. They use an MDF or chip-board core, add solid wood edging, then veneer over it. So the exposed edge is proper solid wood.

With regards to the crossover, it might be possible to improve on this design with a re-engineering of the crossover. However, it is probable that in this case the crossover simplicity is correct for the chosen drivers and intended level of performance of the product.

Unfortunately there is more damage than just the corners and my skill level is not up there to do a hardwood inlay type thing, but I think if that were done right it could have worked well.

I will see what the speakers sound like in an environment that isn't my garage, and then see (or hear) what it does with new caps and then decide if I still want to play further with the crossover. Might be fun, but I might also mess up the sound and go back to standard.

 

[Family_Dog]

I am very sure that these were on the budget side of the spectrum.

More than likely yes, but even Pioneer's budget systems were pretty good back in the day. Pioneer systems were known for great sound back in their heyday.

Play with it and have fun!

-F_D

 

[Namakwalander]

What would be the best place to get capacitors for audio use? I have checked Cummunica, which can be on my commute, but they mostly just have generic capacitors. Although I guess I can just get non-polarized/bi-polar caps from them and give it a try.

I have also checked RS Components and Mantech, but again, not really for audio use as far as I can tell. Also, RS look like they mostly sell in large quantities.

Any other places to check around Centurion or should I buy online somewhere?

 

[Namakwalander]

Also as a general question about speakers, I see a lot of guys on Youtube buying cheaper speakers and then either adding or upgrading the crossovers to improve the sound. Well, they say it improves, but honestly no point in me listening to their updated speakers over my phone or TV.

So does it really improve the sound by adding maybe only an inline inductor to the woofer as a low pass at the same frequency as the high pass for the tweeter, or is it OK to just let the woofer "naturally" reduce volume at higher frequencies? Last time I checked, this is how most car speakers work as well as my cheap floor standing speakers (maybe "cheap" answers my question). Is there really that much to gain?

 

[ludo]

For the fresh capacitors, Communica has these going cheap.

1UF 250VPD15K22

100NF 250V Polyester Dipped Capacitor 22,5mm Kinked 10%100NF 250V Polyester Dipped Capacitor Additional Information Device Capacitor Type Polyester | Dipped Dielectric Polyester Capacitance 100nF Tolerance 10% Rated Voltage 250V Lead Spacing 22.5mm

www.communica.co.za

It's 1uF but 4 in parallel will work. 4uF with an 8 Ohm tweeter will give you a high pass filter at ~5kHz. The formula is freq=1/(2piRC) with resistance in Ohm and capacitance in Farad.

Looks like that tweeter has a 5 Ohm resistor in series with it though, so it's more like 1/(6.28 x 13 Ohm x 0.000004 Farad) which gives a ~3kHz high pass as I see it in the pic.

You might get a few extra and try caps up to the value of 6uF to see if a lower freq high pass filter sounds OK, or just terrible. (Seat of my pants says terrible...) Also see what 3uF or 2uF does. I would keep the resistor at 5 Ohm. Tweeters tend to be more efficient than woofers (they play louder for the same input power) so decreasing the series 5 Ohm resistor might first burn your ears, and then possibly also the tweeter.

The bipolar electrolytic caps go vrot in time. The resistors tend to hold up pretty well.


The rather famous AR18 has a full-range woofer and a first order high pass on the paper cone tweeter. Everything depends on a host of issues that are not simple to measure, but easy to hear. Massaging the sow's ear into a silk purse is certainly possible, but one can also go through quite a few sow's ears before you get the hang of it. I've probably spent more on piggy bits than it would have cost me to just go for the silk, but it has been quite enjoyable, in a roundabout way I'd say do the xover first and listen, then decide if the carpentry is worth doing.

 

[BrianB]

- good advice all round - if serious about speaker design going forward , invest in measuring. (equipment and software) Plenty info on YouTube , can be achieved with minimal $ outlay , eg REW and Xsim.

 

[Namakwalander]

Time for an update.

I have not got round to getting new caps and testing them out. I first want to clean the speakers up so that I can move them into the house to listen to them there. In the mean time they are standing on my table saw and I have to move them every time I need to do something in the garage. I actually do this on purpose so that if something bothers me enough, I will make a plan to sort it out.

I have taken a proper look at the veneer damage and decided that it is not so bad that I need to replace large pieces or make drastic plans. So I "stabilized" the bad parts and filled the chips with wood filler. This still needs to be sanded and then touched up with stain. But the part that has been bothering me the most was the bases or plinths (what is the correct term here?) of the speakers. So I am busy with that at the moment.

Unfortunately, my phone died over the weekend and the only plan I could make was to use a film camera and then send that picture via carrier pigeon to my myself (obviously joking, but it is quite an old phone). I used cheap plywood that I cut into strips and then added a little rebate into the front panels to help locate the sides. A 45 degree miter would have been better, but I suck at woodwork. I also added little squares in the corners to help keep it square and also to mount the frames to the speakers. So far everything is held together with glue, but I might add screws from the inside.



At least the crappy photo does not make my poor woodwork skills so obvious. And once I fix my broken sander, I will flat it and then use spray paint to paint it black similar to the original ones. I might even transfer the stickers and labels from the old frames, but let me first get this part done.

Oh, and obviously the sanding and varnishing of the outside.

 

[Namakwalander]

Ok, I managed to get a better photo. Also of the two frames complete.

 

[Namakwalander]

The frames received some more love with some pocket hole type screws (just don't zoom in on them). Then sanded smooth, wetted to raise the grain and sanded again. Then a very light coat of primer.


Three or four coats of satin black later.


And if you look real close, you can still see the wood grain. Maybe not to everyone's taste, but I like it (unfortunately my camera focused on the grass instead)


I also bought some capacitors. Although it might be the wrong kind. Polyester film or something or other. Oh well, I do not have a "tuned" ear, so hopefully it is fine.

Next step will be to sand the boxes and then seal. Then they should be good as new.

Only real cost so far was the caps (about R90 for 8 of them) and I guess you can add one can of spray paint to that. The rest I had at home.