IMF owners thread!

Discussion in 'British Audio' started by canuckaudiog, Mar 18, 2013.

  1. antennaguru

    antennaguru New Member

    Messages:
    11
    Location:
    here, there, and everywhere...
    I used this foam:
    https://www.ebay.com/itm/50-12-2cm-...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

    There are other sizes available with similar descriptions but that listing worked fine for my CM2, trimmed by scissors to slightly oversize and just pressed into place. I didn't have fresh silicone adhesive to use so I just friction fit them and they are just fine. I may go back and put a bead of silicone around the inside corner.
     

     

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  2. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    144
    Location:
    Australia
    The correct grade of the Reticulated foam used is 20 and not higher as that becomes denser thus choking the speaker enclosure. In Australia we are luck to have Joyce Foams on our doorstep as they sell to all over the world, but they are the manufacturer and not a retailer.

    More info here,

    http://www.joyce.com.au/foams/reticulated-foam/

    Cheers.
     
  3. antennaguru

    antennaguru New Member

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    How is that "20" calculated? Does Joyce Foams explain this someplace?

    I used to build a lot of speakers, and I bought many foam grilles sold as speaker grilles to mount on them. That sort of foam was a very open, very porous foam. It was about the same porosity as the fish tank filter foam I used on this project, as both are very open porous foams meant not to impede air or water flow. I don't really see foams being used for speaker grilles anymore, probably because they eventually decompose - like those foam speaker surrounds we used to use before we learned that they would fall apart too.

    There has to be a way to calculate filter foam porosity, either with air flow or using water to see how much water is retained. For example, a very open foam placed over a jar would only retain a very small percentage of water poured through it in so many seconds. OTOH, a denser foam would retain more water. That would probably be the best way to test porosity. For lack of a known way to measure against a standard I have just held a sample of the foam up to my mouth and blown through it to see how restrictive it was to airflow. The speaker grille foam is similar to the fish tank and air filter foams in this regard. You can actually feel the restriction from denser foams in how much the piece of foam deflects away from your mouth as you exhale...
     
  4. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    144
    Location:
    Australia
    If I recall correctly Joyce make a 20, 30 and 40 grade with the 40 being of the highest density. I replaced the foam from the ports in my Mk IV's and the 20 was the same as the original sample, or better still what was left of it.
     
  5. antennaguru

    antennaguru New Member

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    Yeah, mine came with the old decaying visible foam as well, and examining it with a bright light (since it was too funky to compress or apply pressure to it without damaging it further), its porosity/density visually looked like the filter foam I used - looking at the air gap size relative to the foam structure itself. The big difference was that after 30+ years the OEM foam would no longer decompress after compression, and the new foam would spring right back. The inner foam is very dense compared to this visible grille foam, had no funk going on, and would spring right back after compression - and I certainly wouldn't want to even consider changing that due to its high density being a part of the actual design.

    I am thinking that maybe the 20, 30, 40 are percentage of water retention figures? Water retention really correlated directly to density/porosity. Joyce does mention the same kind of open pore filter foam has the benefit low water retention for use as outdoor seating cushions - and is quick drying. It would certainly dry faster if it retains less rain.

    I will test some of the extra filter foam I had left over with two measuring cups and some water, and let you know what I find.
     
  6. antennaguru

    antennaguru New Member

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    OK, that's not what the 20 number reflects. I took two calibrated measuring cups and put 8 ounces of water (1 cup) into one measuring cup, and put a sample of the foam over the second measuring cup resting it on the rim of the receiving measuring cup. I then poured the 8 ounces of water through the foam into the second measuring cup over a 15 second pour, and all but about 2 teaspoons of water was immediately transferred into the receiving cup through the foam. The are 48 teaspoons in 1 cup (8 ounces). So 46 of the 48 teaspoons passed right through and only 2 were retained, which is only around 4% so well off the 20 figure...
     

     

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  7. antennaguru

    antennaguru New Member

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    Ah wait, I've developed measurement standards before. So maybe they apply a factor of 5 to bring out greater differences between the foam products, to avoid confusion and make selection of the correct foam porosity/density easier. 4% X 5 = "20" high porosity low density foam suitable for speaker grills and air/water filters.

    As a sanity check on this methodology I took a sample of nice dense seat cushion foam and poured the cup of water through it and 4 teaspoons, or 8% of the water was retained. 8% X 5 = "40" low porosity high density foam NOT suitable for speaker grills and air/water filters, but good for seating comfort.

    Mystery of Specification Solved.
     
  8. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    144
    Location:
    Australia
    Now that's measurement dedication I must say !

    What I will elaborate on as I'm no measurement specialist is that the 20 grade (28 cells per inch) foam still chokes the line and the speakers actually sound better at low volume without it, but aesthetically look much better with it installed.

    I'm more than happy to organise the correct grade, cut it up and send it to anyone at cost that wants it and can't get hold of it locally as it's rather hard to obtain. I guess I'm just lucky we have the factory here in Adelaide that makes it for all over the world.
     
    Last edited: Aug 12, 2018 at 4:51 PM
  9. 3kes

    3kes New Member

    Messages:
    3
    Got another question. After the restoration of my TLS50 MK2 (woodfiner, recapp, change mids to Monacor MSH115) I found out that the sound isn’t crispy and clear.

    I measured the super tweeters with a normal multimeter 46,5 ohm. Both of them read the same. With the other units disconnected and the volume pretty high I can hear the super tweeters but not much.

    Can I say that the ST’s are not functional anymore? In that case I’m going to order new ones.

    FYI, before restoring I never heard the TLS50MK2 so I don’t have a reference how they should sound.

    Thanks!
     
  10. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    144
    Location:
    Australia
    46.5 Ohms ? that's definitely no where near correct. They are Coles units which are still available new.
     
  11. 3kes

    3kes New Member

    Messages:
    3
    That’s what I thought also. Already visited Jerry’s site to order new ones. I’m considering new Audax tweeters also because the improvement of my other IMF set (SC2’s). It’s getting pricey
     

     

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  12. Nashou66

    Nashou66 AK Subscriber Subscriber

    Messages:
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    Location:
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    Make sure you measure them not connected, you might be reading the cross over resistance too.

    Athanasios
     
  13. dogwan

    dogwan Dogwan

    Messages:
    1,166
    Location:
    Portland, OR
    Should I be concerned about lack of communication with Falcon Acoustics?
    I used their contact page to inquire about full capacitor set for a very early set of IMF "The Studios". Jerry e-mailed me back asking for pictures of the crossovers, which I promptly provided with cap count and values. Ever since I have not heard a peep despite numerous attempts to get a response. Quite literally it has been 6 months since my first inquiry.

    Also wondering how special his caps are? I know everyone says that they are next best thing to the originals. But, are there other brands besides AlCap that get you within spitting distance? Maybe something that is readily available in the states if I can't get a set from Falcon?
     
  14. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    144
    Location:
    Australia
    Hi Nashou66,

    I would've initially thought that they were disconnected when measuring them, but now that you mention it you've raised my eyebrows over this point.
     
  15. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    144
    Location:
    Australia
    I'll have to say that this is a tad unusual for Jerry as he's normally pretty quick when it comes to capacitor kits etc. Actually he's pretty quick full stop regarding anything.

    He runs a worldwide customer based audience and sometimes things do go astray as they do in any business of this size.

    I'll see what I can do for you.
     
    Last edited: Aug 14, 2018 at 3:08 PM
  16. jerryb

    jerryb New Member

    Messages:
    6
    Location:
    Oxford, England
    Hi Dan. Sorry if you're having problems, but having checked the emails we advised you 15 June what values you needed ( you have an early version as you you know), having examined your pictures which you sent to us 7th June, and since then haven't heard from you. Not sure what additional information you're after? Happy to help. Best wishes Jerry ( Falcon Acoustics)
     

     

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  17. dogwan

    dogwan Dogwan

    Messages:
    1,166
    Location:
    Portland, OR
    I am guessing there is a mix up. I don't see any replies in my inbox and my name is Chris. Sent pics on 22nd February.

    I will go ahead and resend my original email with pics. (from: aboyandhisdog@*****.com)
     
  18. jerryb

    jerryb New Member

    Messages:
    6
    Location:
    Oxford, England
    Received, thanks , will reply by email.
     
  19. dogwan

    dogwan Dogwan

    Messages:
    1,166
    Location:
    Portland, OR
    Actually, since this is the main IMF thread I should post photos of my crossovers for posterity.

    20180218_173853.jpg
    20180218_173931.jpg
    20180218_173920.jpg
    20171108_184341.jpg
    20171108_184239.jpg
    20171108_184121.jpg
    20180218_173910.jpg
     

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