ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi there
Had a great experience with Goodhifi for my CX100 foams, the units supplied for my Pentas (I've got two pairs that need refoaming) is not so good. The foams are too small, with the roll not clearing the cone and the outer diameter being a good 1.5-2mm too small (critical, as the basket frame has a notch and these won't seal if it's not done right).
I could 'make' the parts fit though being too small, this would at best preload the driver and at worst not provide a full seal at the frame perimeter. Neither ideal.
Not a slight on the seller - the package was lost in post the first time and they resent at their cost without delay, and have been very proactive in attempting to placate me, I'm just getting the impression that getting a truly well-fitted foam is going to be a bit of a lottery.
Who's had good experience elsewhere?
Just a quick followup on this post;
If you're based in the US, foam surrounds of the correct size are stocked here - http://www.simplyspeakers.com - my 'already refoamed' set of these had their product in and it works well, perfect fit. The numbers quoted on their website are correct for the ITT midrange drivers in the Pentas.
Admittedly they don't manufacture, they're resellers, and the prices quoted are high at $24.95 per pair of foam rings with glue (clear not white) and shipping. I rang, explained that I'd need four kits per pair (and two of them); they proposed I'd probably not need eight tubes of glue, and produced a price that was honestly comparable with eBay prices - plus I got to speak with a real person over a phone call. I'm cautiously happy, if it all works I'll post follow up feedback here too.
So call them if you've needs for your Pentas. Ask for Tom.
I've just finished refoaming 16 Penta drivers with foamrings from GoodHifi and I don't have any problems with these. But to be honest, they could be a bit larger! Will tell them next time...
Brengen & Ophalen
My GoodHifi units were 4mm too small on the inside, 1.5mm too small on the outside, and the roll is 1.5mm too thick. They probably fit a 3" driver not an 8cm driver, which admittedly is close, and they're certainly not a fit for these ITT 8cm drivers. These are small dimensions but they count.
Could I have 'made' them fit? Sure, though the inner dimension already is a bit of an issue as gluing it down means going over the original glue line, meaning that the next refoam will involve tearing cone material - not ideal. The roll thickness and 'too small' size mean that if everything is glued down properly, there's pre-stress on the cone. Also not ideal, I want electric charge to move these cones, and not any stress in the cone to contribute. Any misalignment and there's a good chance of missing the keyway in the basket (the bit that's 'cutout'), then the driver won't seal and the cabinet design is compromised.
Appreciably it's a cheap component (the foam) though it contributes much.
They're lovely speakers, the Penta (not the most detailed in the midrange but lovely nonetheless) - poor-fitting foams will sound better than rotting foams, good foams will sound better than poor-fitting foams, 'older' electrical components in the signal path will limit things too... a game of perfection, no?
Simply speakers, thats what they do, I think Rich is buying there too, and you are right about not putting the small ones, stress on the surround must give distortion and less lifetime on the surrounds.
BTW put your location in your profile.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Updated! Thank you, Søren.
Søren Mexico: Simply speakers, thats what they do, I think Rich is buying there too, and you are right about not putting the small ones, stress on the surround must give distortion and less lifetime on the surrounds. BTW put your location in your profile.
I've only ever used Woofer Repair.
OK, the SimplySpeakers stuff arrived today. There are some significant differences.
The SimplySpeakers foam is on the left, the GoodHifi foam on the right.
The roll on the GoodHifi foam is too large and the inner diameter too much. This creates a slight pre-stress on the cone and means you're gluing over the factory glue line - looks fine today, in 10 years when they're up for replacement these will tear the cone.
It's hard to see in this photo but the outer diameter of the SimplySpeakers kit is a touch bigger. It's a better fit in the basket.
Here are another two photos of the foams, placed on a Penta midrange (please excuse the poor edge colour deletion - essentially the SimplySpeakers foam, to the left, covers the original glue line on the cone and nothing more, and the roll starts just beyond it):
Glues in the kits are also different. The GoodHifi includes what looks like PVA but may not be. The glue in the SimplySpeakers kit is clear and somewhat flexible when dried. I had thought the application required more of a caulking compound, something that dries quite hard. Probably this requires more investigation as to which is better; I suspect neither are optimal though hopefully we've forum members that can help here.
The SimplySpeakers stuff is also a little 'thinner', feels more flexible. Likely we've no idea which are closer to the original foam though given the cone mass on these drivers is significant for their size, it's probably not going to make a great difference either.
I'll be installing the SimplySpeakers kit on one pair and seeing how it goes, then I'll decide on the rest. If someone local wants to buy what's left (foam rings), I'll sell.
I used Good Hifi to re-foam my Pentas, and it went great, however I used the rubber rings, not the foam ones.
Maybe there is a slight difference in both dimensions, or could it be that they simply sent you the wrong rings ?
Christophe : I used Good Hifi to re-foam my Pentas, and it went great, however I used the rubber rings, not the foam ones. Maybe there is a slight difference in both dimensions, or could it be that they simply sent you the wrong rings ?
Not sure. I did explain the issues I had to the GoodHifi staff and they seemed OK with the dimensions. I didn't, I've ordered something else, I'm happier. I should stress that short of sending a reworked set of rings, they did do everything possible. When the initial order was lost in the mail, they send a second at no charge. The only issue I've got is fitment. Customer service has been good.
I'd have been reluctant to refoam with rubber - this said I've never heard Pentas with rubber rings. Have you been able to compare the sound to a pair with foam rings? You'll probably have the last laugh in 10 years when these need to be redone again!
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: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):
Penta 1's, thee were refoamed very, very poorly when I got them (this one was the best of them):
Of interest the 3's that were refoamed professionally used glue that's closer to the SimplySpeakers stuff. Possibly thinner.
Søren Mexico: GTS: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.
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.
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.
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.
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?
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).
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.
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….
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.