Restoring 28 years old speakers - Worth it?

[Tassin]

After 28 years, the surrounds of both mid-ranges on one of my Acoustic Research 312 HO have cracked. I could import replacement surrounds from US to EU for an estimated 100 €. But, I was also thinking about replacing the entire midranges with new ones. I'm not a speaker designer and have no DIY experience, but I found reading about speaker design really fascinating.

So, basically, my question is whether it would make sense to replace the midranges with new ones?

Though the drivers don't have any information label, I know the AR 312 HO has the following technical specifications:

• 5.25" midranges in MTM
• Midrange enclosure volume: ± 1.9 L (116 in³)
• Crossovers at 180 Hz (2nd order low-pass) and 2.5 kHz (2nd order high-pass, with a 4th order bandpass filter for the parallel-connected midranges
• I measured one of the midrange's impedance using a simple multi-meter (fwiw): ± 6 Ohm
• 1" horn-loaded soft dome tweeter
• 12" woofer
• 94 dB measured sensitivity

Restauration, Part I

• As the midranges are connected in parallel, I assume it would be best to replace them with new ones that are rated 8 Ohm.
• The Scan-Speak 15W/8483G00 has minimum impedance of 7.1 Ohm and measures very nice and flat between both crossover frequencies (180 and 2500). That looks like a match.
• But this midrange has a sensitivity of only 87 dB. In the past, some owner commented that the woofer likely had a sensitivity more towards 89 dB. So, replacing the original midranges with ones with lower sensitivity might bring more balance.
• At 66.50 € (x4) the cost is not an issue. Unless the chance for success would be too low.

Restauration, Part II

Many years ago, one of the tweeters blew up. A friend offered to replace them and I trusted him. After all, I didn't have any knowledge back then, so I was happy with his help. When I started measuring my speakers with REW, I noticed a strange -6 dB dip at ± 4 kHz, starting at 2.5 kHz and ending at 5 kHz. After unmounting the tweeter, I looked up its specs and found that it has a recommended crossover of 5 kHz. That explains it all.

• What would be a suitable tweeter to go with the above Scan-Speak midrange?
• As the original design had a horn tweeter, I guess I'ld better stick to that.
• The Scan-Speak H2606/920000 might be a good choice with a recommended 2nd order crossover at 2.5 kHz, which fits with the AR's crossover.
• Though it has a rather high sensitivity of 95 dB, I've always found the ARs were rolling off too quick in HF. Other owners have reported the same in the past. Could this be related to the crossover? If so, then maybe a tweeter with 95 dB wouldn't be wrong.
• And I've got Lyngdorf RoomPerfect to EQ where necessary.

This is not a project about creating a perfect speaker, but just an attempt at restoring a 90's speaker. And improving it in one go.

What do you, experienced DIYers, think? Does a restauration make sense with above drivers? Or have I got it completely wrong, and maybe I'ld better pull the trigger on those Kef R11s i've been looking at for a while?

 

[Ron Texas]

Projects like this don't make economic sense. They are done because one wants a project to work on.

 

[Sokel]

For every new,different than the stock driver you will need extensive measurements and a whole new crossover.
So,either find the exact same ones or it doesn't really worth it.

 

[Raxumit]

Sokel has it right. If you aren't measuring, you're just guessing. So many things can go wrong with your accidental design that chances are good that at least one thing will go wrong.

And, as someone who has replaced rotting surrounds on old speakers, I encourage you not to bother. By the time you need to replace surrounds the speakers are by definition obsolete.

I say get the KEFs and be happy. If you want a DIY project build new speakers, perhaps starting with a flat pack kit.

 

[DVDdoug]

I'd probably go-ahead and try some less-expensive midranges if you can't get exact replacements... But for me, cost is always an issue.

I noticed a strange -6 dB dip at ± 4 kHz, starting at 2.5 kHz and ending at 5 kHz. After unmounting the tweeter, I looked up its specs and found that it has a recommended crossover of 5 kHz. That explains it all.

The midrange & tweeter may be out-of-phase. Try swapping the + & - connections to the tweeter. If it gets worse you can put it back.

It gets a little complicated but at the crossover point the low-pass creates a phase-lag and the high-pass a phase-lead. If the phase shifts are 90 degrees, you get a 180 degree phase difference between the two and the soundwaves cancel where they combine equally. And it can be confusing depending on how the crossover is marked...

Typically, in a 3-way system it's the midrange that's inverted and that puts woofer-to-mid and mid-to-tweeter back in-phase at the crossover points. The midrange is 180 degrees inverted in the middle of its range but that's not a problem as long as the left & right speakers are the same.

 

[Roland68]

After 28 years, the surrounds of both mid-ranges on one of my Acoustic Research 312 HO have cracked. I could import replacement surrounds from US to EU for an estimated 100 €. But, I was also thinking about replacing the entire midranges with new ones. I'm not a speaker designer and have no DIY experience, but I found reading about speaker design really fascinating.

So, basically, my question is whether it would make sense to replace the midranges with new ones?

Though the drivers don't have any information label, I know the AR 312 HO has the following technical specifications:

• 5.25" midranges in MTM
• Midrange enclosure volume: ± 1.9 L (116 in³)
• Crossovers at 180 Hz (2nd order low-pass) and 2.5 kHz (2nd order high-pass, with a 4th order bandpass filter for the parallel-connected midranges
• I measured one of the midrange's impedance using a simple multi-meter (fwiw): ± 6 Ohm
• 1" horn-loaded soft dome tweeter
• 12" woofer
• 94 dB measured sensitivity

Restauration, Part I

• As the midranges are connected in parallel, I assume it would be best to replace them with new ones that are rated 8 Ohm.
• The Scan-Speak 15W/8483G00 has minimum impedance of 7.1 Ohm and measures very nice and flat between both crossover frequencies (180 and 2500). That looks like a match.
• But this midrange has a sensitivity of only 87 dB. In the past, some owner commented that the woofer likely had a sensitivity more towards 89 dB. So, replacing the original midranges with ones with lower sensitivity might bring more balance.
• At 66.50 € (x4) the cost is not an issue. Unless the chance for success would be too low.

Restauration, Part II

Many years ago, one of the tweeters blew up. A friend offered to replace them and I trusted him. After all, I didn't have any knowledge back then, so I was happy with his help. When I started measuring my speakers with REW, I noticed a strange -6 dB dip at ± 4 kHz, starting at 2.5 kHz and ending at 5 kHz. After unmounting the tweeter, I looked up its specs and found that it has a recommended crossover of 5 kHz. That explains it all.

• What would be a suitable tweeter to go with the above Scan-Speak midrange?
• As the original design had a horn tweeter, I guess I'ld better stick to that.
• The Scan-Speak H2606/920000 might be a good choice with a recommended 2nd order crossover at 2.5 kHz, which fits with the AR's crossover.
• Though it has a rather high sensitivity of 95 dB, I've always found the ARs were rolling off too quick in HF. Other owners have reported the same in the past. Could this be related to the crossover? If so, then maybe a tweeter with 95 dB wouldn't be wrong.
• And I've got Lyngdorf RoomPerfect to EQ where necessary.

This is not a project about creating a perfect speaker, but just an attempt at restoring a 90's speaker. And improving it in one go.

What do you, experienced DIYers, think? Does a restauration make sense with above drivers? Or have I got it completely wrong, and maybe I'ld better pull the trigger on those Kef R11s i've been looking at for a while?

You don't need to import surrounds for €100 from the USA. There are enough shops that sell surrounds in the EU. €12-25 for a pair + shipping costs.
If you have the surrounds repaired, it will cost €80-140 for a pair, + shipping costs.
The repair is definitely worth it, as you'll pay at least four figures for speakers of this quality, not necessarily with a 1 in front

 

[muffinhumper99]

Projects like this don't make economic sense. They are done because one wants a project to work on.

Agreed 100% which is fine projects can be fun. But having said that it’s rarely worth it from an economic perspective. Im a noob but don’t most modern quality speakers best anything made a couple decades ago?

 

[tomtoo]

Good for some experience. Learn a simu, learn crossovers and have some fun.

Will it be a genelec or a neuman ?

But hey its all about the fun to gain some knowledge.

 

[Roland68]

Agreed 100% which is fine projects can be fun. But having said that it’s rarely worth it from an economic perspective. Im a noob but don’t most modern quality speakers best anything made a couple decades ago?

You should simply listen to current, 10-year-old, 20-year-old and 30-year-old top speakers in the same price range and form your own opinion.

 

[Doodski]

Agreed 100% which is fine projects can be fun. But having said that it’s rarely worth it from an economic perspective. Im a noob but don’t most modern quality speakers best anything made a couple decades ago?

You betcha some 40 year old speakers can sound very good if in proper operating condition. I have a lot of experience with some high end series of speaker manufacturers and many of them in the 1980s pricing would sell at retail for CDN $2500+ and would easily in a AB blind test be good speakers today.

 

[Doodski]

Have you frequency swept the drivers that are not rotted. That way you know the overall operating condition of the entire speaker and cabinet before investing in them. If the speakers are in proper operating condition then go ahead with new midrange surrounds. Do they have ferrofluid in them?

 

[Ron Texas]

Agreed 100% which is fine projects can be fun. But having said that it’s rarely worth it from an economic perspective. Im a noob but don’t most modern quality speakers best anything made a couple decades ago?

It's worth doing if one has the skills and the desire to put them to work. I think the more important the item is historically, the more interesting the project will be. The AR3a comes to mind.

 

[EERecordist]

I recently reconed 70's JBL monitors. I fortunately found a professional shop with original manufacturer new old stock (in Seattle, WA). My speakers bought locally had been abused in one each LF and MF drivers, supposably by a famous producer. With my reconing, I would probably break even reselling them.

I would ask myself does maintaining an old speaker justify itself in resale value? Many ASR participants invest in a calibrated measurement microphone and then can evaluate on-axis speaker response, original and replacement drivers, say outdoors with soft surfaces surrounding. I would doubt replacing a speaker driver with a random one would improve resale value or sound.

There are many DIY and vintage/restoration speaker forums to discuss where to go with that particular speaker. There are Acoustic Research enthusiast groups, try Facebook. You may find people parting out AR speakers, or you could part out yours.

 

[muffinhumper99]

You should simply listen to current, 10-year-old, 20-year-old and 30-year-old top speakers in the same price range and form your own opinion.

I mean bro, I love audio stuff as much as the next guy but I’m good on buying gear from the last three decades for A/B testing.

 

[kemmler3D]

whether it would make sense to replace the midranges with new ones?

As others have said, to do this correctly you almost need to redo the whole speaker from scratch. Whether it's worth your time to do this is up to you.

Or have I got it completely wrong, and maybe I'ld better pull the trigger on those Kef R11s i've been looking at for a while?

Sounds like you ALSO need to do something about having the wrong tweeter and crossover in these things.

It's arguably more difficult than a from-scratch speaker build because you also need to figure out some parameters of the existing woofer to proceed.

So if "restoring these speakers is virtually impossible" is what you need to hear to give yourself permission to buy the KEFs... buy the KEFs bro.

 

[egellings]

Projects like this don't make economic sense. They are done because one wants a project to work on.

Also, one can learn a bit along the way, too. There's also the satisfaction derived from finding a problem and coming up with a solution. I have repaired inexpensive stuff that I really had no need for didn't even want. It probably mirrors the satisfaction a cat gets when it 'gits dat mouse'.

 

[muffinhumper99]

It's worth doing if one has the skills and the desire to put them to work. I think the more important the item is historically, the more interesting the project will be. The AR3a comes to mind.

Yes I was agreeing with you just saying that from a pure economic/ROI perspective it's typically not worth it.

 

[egellings]

Yes I was agreeing with you just saying that from a pure economic/ROI perspective it's typically not worth it.

I agree with you about doing restorations. I have restored stuff just for the fun of it, and often didn't want the restored items at all. I either sold or gave them to anyone who'd want them.

 

[Lux_ury]

I've got 15 pairs mostly restored, foams are cheap so is mkp caps. I spent more on glue and silver solder than anything else.
Sound reflections and deadening makes the most contributions to improvement from none! Save as many as you can.
Labour of love IMO.(Smile emoji)

 

[Tassin]

I've got 15 pairs mostly restored, foams are cheap so is mkp caps. I spent more on glue and silver solder than anything else.
Sound reflections and deadening makes the most contributions to improvement from none! Save as many as you can.
Labour of love IMO.(Smile emoji)

I now have one pair of restored speakers.
I decided to simply order new surrounds to repair the midranges . I also ordered two new tweeters with specs that are more in line with the original ones.
Then I cut out a new foam to replace the original foam that had started brittling severely.
Finally measured with REW to confirm the expected improvement was achieved.