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Old 10th March 2007, 01:27 AM   #1
TDWesty is offline TDWesty  Canada
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Default Re-foam of replace woofers?

I just picked up a pair of PSB 50R speakers in decent shape for a song, except the woofers need re-foaming. These speakers are 1987 vintage, and use the same drivers as the larger 70R model which have been my main speakers for 20 years now. (as you might guess, I like them - I'm hoping to restore the 50Rs for my den :-)

I had the woofers in my 70Rs re-foamed last year, but the service shop (sound hounds in Victoria, BC) had a hard time finding correct sized surrounds due to the lack of a flat area on the cone to attach to. (this design is actually mentioned in the PSB spec sheets:

"Since the flexible surround is attached to the cone without the usual flat section for bonding, the surround is effectively decoupled from the vibrating cone, minimizing its own tendency to generate sound."

Although my re-foamed 70R woofers seem to sound ok, and haven't fallen apart yet, I am wondering if a replacement woofer for my new 50Rs is a better alternative, seeing that some 8" woofers can be found for reasonable prices, and the re-foaming cost me around $95CDN for the pair. I am not confident in re-foaming myself, given the difficulty the service guy went through in finding the surrounds to fit, and actually having to cut them and re-glue to make them the right diameter.

I am aware that woofer specs can vary widely, so replacing with a different model is a gamble. Unfortunately, there is little to identify the original driver, except that it is made in Belgium.

Finally, if I decide to re-foam, I assume a competent shop can check for voice coil damage before proceeding? Impedance with a DMM on the speaker terminals shows 8-10 ohms, but one woofer is definitely rubbing the voice coil even with minimal power input, so I'm worried there may be damage. I only applied power for a few seconds to avoid possible damage.

Thanks.
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Old 12th March 2007, 04:03 AM   #2
TDWesty is offline TDWesty  Canada
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I've done a bit more research, and these surrounds are proving very hard to find. None of the ebay vendors have them. The problem is not the lack of a flat edge on the cone, as I said earlier, but that the "roll" of the surround is very thin for an 8" speaker - it is about 3/8" wide, whereas most seem to be 5/8" or more. ie: there is only 3/8" between the edge of the cone and the metal frame. Some JBL LE models use a thin surround like this, but the diameters are different slightly. I believe the JBL surround is what was used for my other pair, and the shop cut a section out and spliced them together to get a smaller diameter.

I am fairly certain these drivers are made by Philips, and bear the number AD 80652/W8. This seems to match the numbering scheme seen on a few other Philips drivers I've come across. Does Philips make drivers any more?

Given the choice of using a surround with the right outside diameter, but a wider roll, and letting it overlap the cone a bit more, and using a thin-roll JBL surround, and splicing it to fit, which would you think would be preferred in terms of sound quality and durability?

Surely someone here has used/seen Philips drivers? This is the only link I could find on google...
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Old 12th March 2007, 04:37 AM   #3
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I see an 8" Philips woofer for sale on ebay with number AD8066/W8.
They seem to have the narrow surround that you describe. Maybe worth a look.

Jeff
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Old 12th March 2007, 02:45 PM   #4
TDWesty is offline TDWesty  Canada
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Yes, thanks for that. I did spot those ones (ebay#270097950159), and the surround looks similar in size, but the octagonal frame is much different. Those units look pretty old to me, and I wonder what those lines of glue? are on the cones? They look like patches, but are the same on both. Maybe to reduce resonance?

I'm waiting to hear from PSB on the cost of new woofers or if they will sell surrounds. One concern about buying new woofers is how they will last if they've been sitting storage for twenty years - won't the foam be ready to fall out on them too?

In the meantime, if anyone knows of a dealer for Philips speaker components, please let me know.

Thanks.
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Old 12th March 2007, 05:15 PM   #5
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Maybe you should consider building speakers. Not sure what your size requirements would be, couldn't fine any images of your PSB's online.
There are lots of options to keep costs down etc.

Jeff
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Old 12th March 2007, 05:49 PM   #6
TDWesty is offline TDWesty  Canada
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Someday I plan to try building speakers, but I couldn't pass these up at $1... - see ebay #250088506913 for what the 50R looks like. The 70R uses same drivers, except a much larger cabinet and a 10" passive radiator instead of ported.

I've had the larger 70R speakers since 1986, and still like the sound of them. There were well known in the mid 80s as the CBC did a review of many speakers and chose the 70R as their standard studio monitors, stating they were equal in sound quality to the two closest competitors (one from UK, the other US) costing more than twice as much. At the time, I compared them with Rega and Boston models in the same price range ($600 CDN), and preferred the PSB.

I really don't know how they compare to current model speakers, as I have not listened to anything else in many years. Someday I'd like to build some small speakers for the family room, and get my big PSBs out of there.
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Old 12th March 2007, 07:21 PM   #7
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Quote:
I really don't know how they compare to current model speakers, as I have not listened to anything else in many years.
I think you would be shocked by the sound quality of speakers being built in this area.
A friend came by for a vinyl listening session (he owns Linn Ninkas), and just sat in stunned silence as music poured from my little Fostex FE127's. He asked where the other speakers were, I said there are no other speakers playing in the room. He said he couldn't believe the detail of my speakers compared to his Linn's, and them mumbled that he should sell them.

Jeff
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Old 12th March 2007, 08:27 PM   #8
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Except for aesthetics, there's nothing wrong with splicing a foam surround to make it fit. A good speaker tech should be able to make an acceptable repair.
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Old 12th March 2007, 10:16 PM   #9
TDWesty is offline TDWesty  Canada
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Quote:
Originally posted by Tosh
Except for aesthetics, there's nothing wrong with splicing a foam surround to make it fit. A good speaker tech should be able to make an acceptable repair.
Thanks for the info. Would you recommend a butt joint, or an overlap? The ones I had done last year were done with a butt joint, and it is barely visible. So far, no signs of weakness.
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Old 13th March 2007, 03:55 AM   #10
TDWesty is offline TDWesty  Canada
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Quote:
Originally posted by vinylkid58


I think you would be shocked by the sound quality of speakers being built in this area.
A friend came by for a vinyl listening session (he owns Linn Ninkas), and just sat in stunned silence as music poured from my little Fostex FE127's. He asked where the other speakers were, I said there are no other speakers playing in the room. He said he couldn't believe the detail of my speakers compared to his Linn's, and them mumbled that he should sell them.

Jeff
I admit I am intrigued by the TL designs, but I have too many projects on the go, and none near completion... :-(
I'd love to hear what all the hype is about some time.

Tonight I swapped the re-foamed woofers from my 70Rs into the 50Rs and had a listen, to make sure the tweeters and XO are ok. The smaller speakers actually slightly better imaging, possibly due to the stands they are on vs. the large ones on the floor. Part of this could also be the narrower front baffle (just guessing here). They sound very nice, definitely less bass, but very nicely balanced. I may even keep these in the family room. My wife would be happy with the smaller ones... :-)

Interestingly, I also swapped back in my 3020 after a few songs, and found it sounded a bit better than the 3125.

Do tweeters deteriote over time, or just fry all at once? These are Philips soft cloth dome units. Somehow the high end in the 50Rs sounds a bit nicer, but maybe it's just speaker positoning, as it is quite subtle.
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