Latest. The GoodHifi glue is easier to work with (I'm almost sure it's PVA) but doesn't glue as strongly and requires compession to 'take' at all. Going to shim these, will let all know how they turned out.

Does anyone know where to get a recone kit for these?

More latest. Tried gluing one of the foams with the GoodHifi PVA, needs compression to sit properly. The rest were done with the SimplySpeakers glue, needs only light pressure to sit though it's stickier to work with... trick is to use it sparingly and wait a moment before it fully tacks before seating the foam.

My Penta 1 drivers were in a very poor state when I got them needing some light sanding to get rid of a botched refoam job. Decided to shim and fit as the cones were very much off-center. If the shimming didn't work, I'd intended to strip what's good and sell piece by piece. A 5 thou sheet of acetate later and they're perfect. Aesthetics not 100% as cutting and regluing the dustcap makes it look like what it's had (surgery) but the centering is perfect. The Penta 1's are saved, shimmed and an overnight cure away from remounting and running in.

Did the Penta 2 set similarly. It's so easy and effective, I'm not likely to not shim ever again.

GTS wrote:

Did the Penta 2 set similarly. It's so easy and effective, I'm not likely to not shim ever again.

We love pics, good job-

Give me a few days - I've got two more of these to do - my housemate spilled red wine on the last two foams (!) and having doubts about their structural integrity from there, I've got a few more coming via mail. I'll take photos with the cap cut off etc.

In the meantime if anyone wants the GoodHifi foams, first $20+shipping to wherever you are gets them with glue - all 16 of them (enough for two pairs of Pentas).

More latest.

Bear in mind I have a pair of Penta 3 that were professionally refoamed and are well run in as a benchmark. So the process is run one speaker at a time, compare to a Penta 3, etc...

Put the Penta 2 back together first. Swapped out the yellow lens covers for Penta 3 lenses off eBay as the yellow looks fairly horrid. Fired up the left first. As expected tight in the midrange initially, better after an hour but some warmth is missing. I'll run in a bit more tomorrow and if we're stil here, I'll pull it apart and have a look for something out of phase. Will get to the right tomorrow. Does anyone know if the left and right side 'midrange and tweeter section' are mirrored?

I put one of the Penta 1 back together also, I'm waiting on more foams to complete the second, was curious to see how these sounded. The drivers are older and badged differently to those in the Penta 2, the drivers are also measurably lower in impedance to the set out of the Penta 2 pair. Not sure if the difference in impedance is reflected in crossover differences, but they're immediately brighter. Really should check the 2's for phase again...

Pics of what they were like when I got them.

Penta 2 (never refoamed):

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Penta 1's, thee were refoamed very, very poorly when I got them (this one was the best of them):

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Of interest the 3's that were refoamed professionally used glue that's closer to the SimplySpeakers stuff. Possibly thinner.

Søren Mexico wrote:

GTS wrote:

Did the Penta 2 set similarly. It's so easy and effective, I'm not likely to not shim ever again.

We love pics, good job-

Sure. Here is a brief problem definition - four of the six culprits. L-R we have a Penta 1, Penta 1, Penta 3, Penta 2 (with the yellow lens swapped out). The Penta 3 have been my daily speakers for a few years. They are fed by some decent interconnects, an upsampling DAC and a generally lossless audio sources. It's said that blind tests between lossless audio and high-bitrate MP3 prove things to be indistinguishable, however most people that come over can pick FLAC/ALAC from 320kb/s MP3 with this setup. This from a speaker regarded as 'cloudy in the midrange' - go B&O! Settings are minimum bass, least sensitivity on the Pentas.

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The photos below are of the cosmetically worst driver from each driver pair.Taken with a cameraphone, they look much better to the naked eye.

This is a Penta 1 driver. Of those refoamed, these came in at the lowest impedance by a half ohm consistently and 0.15 ohm variance among them. They're badged ITT or SEL (4 each). The dust caps were purple when I got them (through age? Environmental conditions? Who knows. They'd come from a smoker's environment - lots and lots of cleaning here - and are the last time I trust an eBay seller with 'Perfect condition! Professionally refoamed!'. The refoam was awful. The foams weren't run in, which was good as three drivers had light contact and another three were borderline. They needed a light sanding to get glue off in pieces. Really not good. Since salvaged.

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This is a Penta 2 driver. These speakers were otherwise in pretty good condition. The drivers are all badged Nokia, and the dust caps were yellow/brown. Under the dust cap they're identical to the ITT/SEL drivers - six vent ports, some pretty loose tolerances for the piston from what I could make out.

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This is a Penta 3 driver. I used to think these were refoamed, as when I bought the speakers there was a receipt for this. Two local professionals assured me they could provide results that were cosmetically comparable with reshimming too. Despite the age, these could be the original foams. Who knows, opinions welcome.

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Results? They all sound great. In pairs, though, they sound different. And they only sound cohesive when run in their original pairs. The 1's are definitely the brightest (impedance? Crossover specs?) The 2's are closer to the 3's, possibly a little tighter in the midrange (the foams will wear in I'm sure) - though possibly a little lacking up top?

What would I change if doing things again?

• I'd hunt for some suitable dustcaps mercilessly. It keeps the cone mass closer to original, despite the notion that T/S parameters vary significantly between drivers of the same type and that the same modification to a set of identical drivers should affect each identically. Despite it being under a gripe, I kind of like things looking pretty too. Above all a new one would be easier to work with, though given the glue width on the original item, finding something suitable might be tricky.

• I'd use the SimplySpeakers glue again - it's light years better than PVA - but with a much smaller nozzle, something in the 1-1.5mm range. What's supplied is great for refoaming woofers, not 8cm drivers.

• I don't regret reshimming my Penta 1's, they were in very poor shape. But the 2's? Not sure there was much need, though no regrets. Don't get me wrong, they sound great, though they were pretty much on-tolerance. Shimming didn't reveal any great lateral misalignment issues in these speakers, which had been well looked after. Possibly just weighing down the cone on the centre of the dust cap would have done it just fine. The 1's had taken a beating by comparison, shimming fixed these properly - I was surprised how much alignment force is taken in the foam - it really is important to get it right, particularly if you're to run your speakers hard. The foam will weaken over time and what was centered when pressing up and down a few times using clothes pegs to hold it in during installation, probably won't work when it's oscillating hundreds to thousands of times a second at high amplitude a few years later.

• I don't regret not using the GoodHifi foams, whoever needs to redo these in 10-15 years - be it myself or someone else - won't be tearing the cone to get remnants of the last job off. (They have great customer service though and could probably very simply redesign their foams, after which I'd be a happy customer).

• We'll never recreate the original sonic properties of the drivers with new foams unless we're getting original foams from ITT - the two foam brands I have feel different in the hand, and would offer different damping properties. There's likely a bigger effect on T/S parameters here than in removing a bit of cone material, as the moving mass - for an 8cm midrange - is high.

• I still don't know that I'd let a professional refoam them. The best quote I had here was USD$30/ea - or $240/set. Quite steep. If money wasn't an object and time was, I'd probably have focused on the signal path. Given there are 18 moving assemblies with a pair of Pentas and a bunch of other things that age depending on environment and usage, we shouldn't be surprised that there are sonic differences in these three pairs. Replacing tired components in amplifiers and crossovers probably has a more tangible effect on rejuvenation than anything else - the midrange drivers are honestly a pretty robust design. They're clearly not the 'Rolls Royce' of drivers but they're judged here as part of a complete assembly, and considered on their own from a maintenance perspective, I've learned that they'll take a good amount of abuse regardless.

Now if I can only work out how to make a new Penta top cap… hmm...

Of interest, two more photos showing shimming.

The Penta midrange with the dustcap cut out (this one was in pretty good condition to start with - no contact/misalignment). The small imperfections on the former (the metal bits around the pole and bonded to the voice coil) are not the knife I used to cut things out, and were present on a fair few of these drivers. At this stage the new foam is glued on (appears distorted in this photo for some reason but was measured concentric within 0.5mm).

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Shimmed with 5 thou acetal sheet. Sit the shims in, move the cone up and down to settle the shims appropriately, lift up the outer of the foam and apply a bead of glue to the basket, let it tack (the wrinking seen here) then tap down to a smooth finish.

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Remove the shims, glue the dust cap down. Remove any excess glue, let it dry, check to see you've a seal and it's good to run.

Dear Sir,

At most pictures I see a kind of surround that almost must be a standard surround that incidentely also 'fits' on a Beolab or Beovox Penta. What do you think of under beneith repair?

Best regards, Fred

Beautiful isn't it? The Penta repaired in it ’s full greatness….

Best regards, Fred

Fred, there's nothing special about the speaker size - they're certainly standard-sized foams.

Whether they're mounted above of below the driver really doesn't matter. I think above is aesthetically better as we're mounting to a paper, not a poly driver cone, so mounting under will likely leave residue and may not tack as well given the surface quality.

Foam is better than rubber but we really don't know a great deal unless B&O releases the T/S parameters for the drivers and we do a pre/post test with each one for conformance. I didn't find anyone through B&O that'd actually go that far... so I did it myself.