Sign in   |  Join   |  Help
Click here to tell us about your new email address

Penta Refoam surround sizes.

rated by 0 users
Not Answered This post has 0 verified answers | 11 Replies | 3 Followers

Gavin
Not Ranked
Sydney
22 Posts
OFFLINE
Bronze Member
Gavin posted on Thu, Jan 22 2015 3:57 AM

Hi all,

I'm restoring a pair of Penta IIs. The component upgrades are going well - thanks Martin.

I'm now doing the foam surrounds. I ordered a set from GoodHiFi which arrived promptly with good customer service and communication. I have three questions for people who have done this job:

 

  • Do the new surrounds fit to the inside edge of the metal frame or sit inside by 2-3mm?
  • Do you glue both the cone and surround or just one?
  • After applying glue to the existing cone exactly where the glue was previously, I'm finding the lip of the foam doesn't line up to the glue line. The glue sticks to the flexible part of the surround, not the lip where it is supposed to. e.g. the lip of the foam is too far towards the dust cover in the centre. Is it just this particular surround or do they all do this? (See right hand side of pic)

 

I've ordered another set from Audiofriends in the hope that the size is slightly different. I don't want to do this job with 90% accuracy. I'd like to get as close as possible to the original.

Any advice appreciated - thanks

Update: after typing this I found another thread which says it better than I could:

http://forum.beoworld.org/forums/t/1813.aspx?PageIndex=1

The question still remains, is the Audiofriends foam a better fit than GoodHiFi?

To be clear, I'm not having a go at the company. They have been very efficient with the order.

Also, if anyone is interested, I've taken pics of all the steps if you want photos of any of the before and after shots.

 

Cheers

 


All Replies

leogoeswild
Top 50 Contributor
Helsinki, Finland
1,371 Posts
OFFLINE
Bronze Member

I have the ones from audiofriends. Mine sits with a few mm of space to the outer metal ring.

Would you please post a picture of the ring lying down all the way. It looks like that one is a better fit than the ones I have.

 

I did the refoaming myself on my own penta´s, and on a pair that I sold to a friend.

There has been no problems, except one funny thing we noticed the other day.

While having a blind-test on playing the penta´s with the original Beolab 200 amplifier and ICEpower 250asx2, we noticed something very strange.

This song: Yiruma – River Flows In You - Original <- it is clickable

And most of the songs by Yiruma..

They all gives a distortion to the mid-range. I tried on mine, and they play fine.

All other music plays fine on my friends penta´s, but that song gives distortion.

So they can´t be perfectly fitted :(

 

Gavin
Not Ranked
Sydney
22 Posts
OFFLINE
Bronze Member

Thanks for the reply. I'm enclosing some pics.

The reason for the post is that I don't want to buy another set and find they are the same or worse that what I already have. The other linked post suggest SimplySpeakers if the Audiofriends kit fails to match the original.

 

I think the key differences are the outer diameter which doesn't bother me so much as long as it creates a seal all the way around, and the bump in the foam known as the 'roll' which I think needs to be thinner to allow the inner foam edge to locate properly.

 

I have yet to master the art of uploading multiple pics :(

 


beotkn
Not Ranked
13 Posts
OFFLINE
Bronze Member
beotkn replied on Thu, Jan 22 2015 11:03 AM

double post

beotkn
Not Ranked
13 Posts
OFFLINE
Bronze Member
beotkn replied on Thu, Jan 22 2015 11:04 AM

I recently finished refoaming a  pair of Penta IIIs using the foam rings and glue from GoodHifi.

The result and sound is very good and I don't see a reason not using the GoodHifi surrounds. 

For the inner ring I put the glue on the foam and not on the cone and as a last step I filled the small gap between the outer ring and the metal frame with glue.

leogoeswild
Top 50 Contributor
Helsinki, Finland
1,371 Posts
OFFLINE
Bronze Member

Yours looks just like mine.

Regarding my previous post: I did not mean that the surrounds can´t be perfectly fitted, I meant that I can´t get them perfectly fitted with my skills.

I read about someone who tried with rubber vs foam surrounds, and they could not hear any difference. 

I am satisfied with AudioFriends. Have used them for both Penta and CX100.

Lee
Top 100 Contributor
Newcastle upon Tyne UK
686 Posts
OFFLINE
Silver Member
Lee replied on Thu, Jan 22 2015 6:03 PM

I had a similar problem with mine making a slight buzzing sound particularly with piano music.. turned out one of the drivers was ever so slightly off centre. Re-re-foamed it and its been fine ever since :-)

Lee

Beobuddy
Top 25 Contributor
Utrecht, The Netherlands
3,109 Posts
OFFLINE
Founder

leosgonewild:

 

So they can´t be perfectly fitted :(

 

The Audiofriends surrounds are 99% accurate. I know this for sure as I'm the one who developed the surrounds in assocation with Audiofriends.

I'm no shareholder by the way and don't earn any penny with it.

 

The surrounds (at the moment mk3 or mk4)  fit very well. No disstortion at all.

The problem lies with the person who's responsible for glueing them WhistleBig Smile

Mostly the cause of placing them wrong (which causes distortion/scraping sound), is caused by placing the surrounds exactly around the dustcap in the middle. That's where it goes wrong. The dustcap isn't always placed exactly in the middle.
I've done I think a several hundreds of these surrounds with very good result. I test them with an B&O oscillator RC7 and an amplifier.

An example is down here. Look at the redish ring around the aluminium "coil" The distance from the red ring to the centre differs around the coil.

So when you place the surrounds exactly by eye around the dustcap, then you will end up some times with badly behaving mids.

As I'm almost doing this every day, I've have made a set of special rings with the right skew to the cone to align the surrounds the proper way.

If you place the surrounds right, then you have approximately 0,3-0,4mm space between the outer diameter from the surround and the inner diameter from the chassis.

 

 


Beobuddy
Top 25 Contributor
Utrecht, The Netherlands
3,109 Posts
OFFLINE
Founder

beotkn:

I recently finished refoaming a  pair of Penta IIIs using the foam rings and glue from GoodHifi.

The result and sound is very good and I don't see a reason not using the GoodHifi surrounds. 

For the inner ring I put the glue on the foam and not on the cone and as a last step I filled the small gap between the outer ring and the metal frame with glue.

These rings don't fit at all ! The inner diameter doesn't fit and is far to small. To much pressure has to used to get these fitted. And with that you're taking the the cone out of his "comfortzone". By using these,  the cone can hardly vibrate as it should be. Far to much tension on the cone.

Finally, if you will be able to get them fitted, then they become loose in time where the coil leads enter the cone. At that point the surface at the chassis is less and the Good Hifi rings can hardly be glued properly.

 

leogoeswild
Top 50 Contributor
Helsinki, Finland
1,371 Posts
OFFLINE
Bronze Member

Lee: Yes, it is only with piano music. No other music. Re-re-foam will be done :)

 

Beobuddy: I did not mean to give AudioFriends a bad reputation, and I tried to clarify that in  the next post where I wrote that it was my skills that were bad, not the surrounds.

Gavin
Not Ranked
Sydney
22 Posts
OFFLINE
Bronze Member

Just a quick update to let you know that one speaker is finished, and the results are great. The foam from Audiofriends fits very well as mentioned by others here. See pic.

I used glue on both the foam and the cone, waited 3 minutes for it to become tacky, then stuck them together. There is still time for minor adjustments before it dries completely. I also used a small wine glass rim to add pressure to the outer edges. Seems to work well, and very little residue has leaked out on the visible part of the cone.

Now for the second speaker....

On a slightly different topic, is it just me that finds getting the transformer back into the amp housing is a very tight fit?


NickNike
Top 500 Contributor
England
60 Posts
OFFLINE
Bronze Member

Hi beobuddy,

 

Are you saying that the surrounds (Audiofriends, about to order off ebay) are fitted correctly if the surround is concentric to the speaker frame outer lip, and that what is required is a constant radial gap all around between the surround outer diameter and the speaker frame lip inner diameter?

 

cheers

Nick

Page 1 of 1 (12 items) | RSS