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DIY FB1i anyone?

Discussion in 'd.i.y.' started by mikesnowdon, Jun 24, 2008.

  1. mikesnowdon

    mikesnowdon resU deretsigeR

    Im new to this so I apologise in advance for asking silly questions.

    Im currently working on the cabinet dims for the FB1. I have the external dims which can be downloaded from the pmc website. Ive managed to cut and paste the 'cut away' image of the FB1 (showing the TL and damping) onto the drawing with the external dims. Now all I need to do is find out what thickness the panels are and I'll be able to work out the rest of the dims. (A freind is a CAD expert so he will help me here) Does anyone know the cabinet wall thickness? (below is an example based on the OB1)

    [​IMG]


    Next question is of course on the xo. Ive been searching and searching for a schematic of some sort but nothing yet. Ideally I'd like the latest 'i' version but the '+' would suffice. Anyone here own FB1's or know the xo setup? (I found this website who sell the crossovers, pricey though: http://www.technosound.co.uk/nav.php?pageid=SpeakerSpares#PMC)

    This leads to the final question: Drivers.

    From what I can tell the midbass is either:

    Vifa M17WG-09-08 or Vifa M17WH-09-08

    The tweeter I believe is:

    Vifa D27TG-45-06 for the '+' version.

    For the 'i' version:

    [The PMC website tells us the tweeter is a 27mm SONOLEX* unit (*which I've found out is a trademark of SEAS). The unit PMC use also has a rear chamber.]

    Having looked at the SEAS website I've been able to narrow it down to this:

    H0881-06 27TFFC.

    Can anyone help with corect driver identification or crossover details please?

    Thanks in advance for your help and advice.

    Mike
     
  2. PigletsDad

    PigletsDad pfm Member

    SEAS and Tymphany (Vifa is one their brands) are both set up to do special OEM versions of drivers for manufacturers, so there is every chance that they are special versions tweaked to specifications that PMC set.

    As such, they are probably only available from PMC. If you use off the shelf drivers, the crossover will need to be redesigned to suit the devices you can buy; this needs measurement kit, software and some expertise.

    You are probably much safer working with a design for which the drivers are known and available. Here are two sites that offer lots and lots of designs, most of which are based round drivers that are available for DIY.

    http://www.zaphaudio.com/
    http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm
     
  3. mikesnowdon

    mikesnowdon resU deretsigeR

    Thanks for the advice and the links, both sites that I visit regularly.

    Your right about the drivers probably being tweaked versions, the faceplate of the tweeter is certainly a PMC only thing (whether it does anything or is just a gimmick is questionable). Then again they might br so simmilar to the OEM units that this project would be possible. If it were the case then I would only need one crossover which I would copy, exactly using the same components, so I have a pair.

    Niel @ Wilmslow audio has told me that the midbass is almost certainly a Vifa M17WG-09-08. I think I'll bite the bullit and assume the tweeter I have chosen is the correct one. If at the end of the day it dosent sound right I can always get Wilmslow to do some measurements for me and tweak the xo hf section accordingly.

    Is there anybody out there who owns FB1's and wouldnt mind removing the drivers and passing on the part numbers?

    Mike
     
  4. James Evans

    James Evans Bedroom Bodger

  5. mikesnowdon

    mikesnowdon resU deretsigeR

    Thats unbelievable, they look identical! Had a look at the Ornec website and they also have a Proac 2.5 lookalike? Who are these guys?
     
  6. James Evans

    James Evans Bedroom Bodger

    There's threads on various fora discussing these and the manufacturers are aware. Those FB1alikes had gone from the site until recently, only the tb2alikes were there last time I looked.
     
  7. PigletsDad

    PigletsDad pfm Member

    Unhelpful post removed.
     
  8. mikesnowdon

    mikesnowdon resU deretsigeR

    Removed.
     
  9. colasblue

    colasblue pfm Member

    Judging by the number of customer reviews they'll soon be getting into double figure sales when you consider all models together.

    I don't think the major brands have much to worry about

    be interested to know what they actually sound like though but the prices seem just too cheap to even cover the cost of the drivers!
     
  10. mikesnowdon

    mikesnowdon resU deretsigeR

    The Von Masoch appear to be identical but of course we cant see inside. For all we know they could just be ported? At the end of the day there cheap fakes and the import tax, shipping makes the outlay, ca. £600ish. Its probably cheaper and alot more fun to Do-It-Yourself.

    Ideally I'd like to get a few people interested in this. I can do the cabinet plans, we can all chip in and but an buy an actual FB1i crossover to copy. And with a litlle detective work find out the exact tweeter used.

    If sucessful a OB1 alike could be developed, perhaps with a better midrange though, SS 12M4631G00 anyone? Sort of 'Ekta' with cheaper woofer, enclosure based on the OB1 TL? http://www.troelsgravesen.dk/Ekta.htm
     
  11. zener

    zener fluff

    Mike I have FB1's , with the old metal dome tweeter , so not much use for that or the crossover , but the bass/mid is the same as is the cabinet , I can pop the drivers out and measure what panels i can ie. thickness
     
  12. James Evans

    James Evans Bedroom Bodger

    Hi Mike. I was thinking about trying to diy my DB1s into DB1is a while ago and looked into the tweeter. I think I came to the same conclusion as you about it being the 27TFFC. It may well be modified to pmc's spec, who knows.... I have no idea on what xover changes would have been required. I think in my case the tweeter is deeper than the one in the original DB1 so it wouldnt have fitted in the cabinet (unless again there's been some pmc specification going on there...)

    Anyway, I digress, just wanted to backup your tweeter findings.

    Welcome back to the fold btw!
     
  13. mikesnowdon

    mikesnowdon resU deretsigeR

    Zener,

    If you could do that it would relly help with the cabinet plans, while you have the midbass out could you take note of the partnumber on the driver please?

    James,

    Im hoping the only difference with the tweeter is the groves around the faceplate. I think this is supposed to aid dispersion but I cant imagine it effecting the fr too much. Hopefully someone with the 'i' version can help us here.
     
  14. PigletsDad

    PigletsDad pfm Member

    A site with some useful background on transmission line speakers (and related designs) is Martin King's - http://www.quarter-wave.com/.

    I realise that you are primarily trying to clone an existing design, rather than do a new one from scratch, but some of his material, or one of his spreadsheets, may help tweak the design for the differences (if any) between the driver that PMC use and the Vifa M17WG-09-08.
     
  15. mikesnowdon

    mikesnowdon resU deretsigeR

    Good link, thanks.
     
  16. mikesnowdon

    mikesnowdon resU deretsigeR

    If/When we find out the tweeter and xo changes might be you can carefully rout out the tweeter recess if necessary. If you cant do it yourself, im sure a skilled carpenter could do it for a small fee.
     
  17. James Evans

    James Evans Bedroom Bodger

    It's actually the depth chamber as opposed to diameter, or depth of surround - the DB1 transmission line is pretty crammed in and is fairly tight up behind the original tweeter, which isn't as deep as the 27TFFC. I suppose this is where the requirement for pmc to redesign the cabinet came from (possibly...). From memory the diameter and screw hole placement is identical.

    Aren't the bass/mid-bass drivers different in the i series as well? Something to do with quality control at vifa going downhill after being bought out - the grey cells may be malfunctioning on that one.
     
  18. Dick Bowman

    Dick Bowman Well-Known Member

    Can't really see the point in DIY copying. Surely more to be had in getting to understand underlying principles and construction techniques, then trying something original.

    As for commercial duplicates where we can only judge the outsides...
     
  19. mikesnowdon

    mikesnowdon resU deretsigeR

    There is a simmilar SEAS unit wo rear chamber. Basically the same as 27TFFC but no rear chamber hence reduced depth. Would probably fit. Then you'd need to measure it in the DB1 baffle and tweak the xo accordingly. (If your lucky you might get away with upgrading the Caps and tweaking the resistor value, I did this in my TDL's without measuring and got a definate improvement) I know the midbass used in the OB1i is a Morel unit. I think the rest are still vifa though.
     
  20. zener

    zener fluff

    OK Mike my FB1's share the same bass / mid unit with the FB1+ , which is a VIFA M17 WG09. The panels are all 3/4" thick MDF type stuff.
     

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