advertisement


DIY FB1i anyone?

Really interested in the outcome of this thread, as the PMC FB1 made a great impression on me when I heard it many years ago.

I wondered if it were possible to re-jig the design and have the port fire out the rear, though that would defeat the purpose of a "clone" I guess, but in my opinion is the only aesthetic failing of the design, I can't argue against it's sonic quality!!!
 
Ive not taken this past the 'idea' stage unfortunately. Mostly because of other projects and also because Im really happy with my modified TDL RTL2's. Im building a new amp currently and after that big mods are planned for my CDP. After that If all works out well with regard to improving the system sound I might get on with one of the many speaker ideas I have. I remember towards the end of last year I worked on plans for a TL version of Troels Gravesens 'Exta' design, so it would be a choice between that and the FB1 clone. I would expect the Ekta TL to sound best (3-way scanspeak) but the drivers alone would cost over double that of of the FB1. Someday....:)
 
I almost forgot about this thread :D

Looks like its been 'moderated' the crossover schematics and close up pics of the PCB are gone...Good job I still have them here then ;)

Getting tempted to do this build now. The exact drivers are clearly not OEM for the "+" version nut might be tricky to find. I think both midbass and tweeter are discontinued. Anyone know?

PS: The little one had her 2nd birthday not long ago :)
 
Hi Just come across this thread, good work
could i have the plan of the speaker and crossover, any DB1 project
long live diy, great forum
Abes
 
Hi Just come across this thread, good work
could i have the plan of the speaker and crossover, any DB1 project
long live diy, great forum
Abes

Are you actually going to build them? I love to do it myself but the funds aren't there and the drivers are hard to find.
 
yes,but i need the plan.with the help of all the members of the forum i think we can have the drivers or equivalent.must have something out there
Abes
 
Hi Gents,

I also just stumbled across this thread and I am also looking for the FB1+ detailed views/schematic. I actually have a set of original FB1s which had crossover problems (I have a second set of drivers which I managed to get when I didn't realize the problems were in one of the crossovers). I bought a set of the original crossovers from someone who had done the FB1+ upgrade and that fixed all my problems (and having a spare set of drivers is good). After reading some mention on other forums I tried clipping off the phase disc on the aluminum tweeter on my spare set last night. The jury is still out on that one - it seems more detailed but slightly less focused.

I know the FB1+ upgrade involves new foam too, but I am interested in trying just the new tweeter and getting the parts to redo my old crossovers so I all be able to switch between FB1 and FB1+. The original crossovers seem to have the exact same PCB board posted here. The only difference seems to be the absence of the 56 Ohm resistor in the original crossover and the 3.3 uF cap is 3.0 in the original. The other caps and resistors are the same. The coils look identical but I guess its likely the values are different? Did anyone nail down the values for these?

Thanks in advance!
 
Mike, based on the above your xover is:

fb1.gif


quickly knocked up in ppt so boxes for inductors rather than coils, but it should be clear hopefully!

Very similar to the DB1 xover unsurprisingly

Hi James.

Any chance you still have the XO schematics? For some reason they disappeared from the thread.

Cheers.
 
Here you go Mike:

FB1.gif

Thanks for the schematic... I just compared against the FB1 and used some online calculators for 2nd order Linkwitz-Riley filters.

The LP circuit is identical to the original FB1 and the HP circuit adds a 56 Ohm to make an L-Pad attenuation of 1.5 dB compared to the original tweeter (original tweeter efficiency is 91 dB and new one is 92.5). The 3.3 uF vs the 3.0uF keeps the crossover at 3KHz with the extra resistance parallel to the tweeter resistance. I don't think the coils changed at all.

Also the 3.0uF cap on the original FB1 was Bennic branded (like the resistors here) and the FB1+ are Solen FC caps - and so far this is the only difference in xOver I can see that would allow PMC to claim the FB1+ had an improved crossover - all the other parts are identical and the extra resistor is purely for necessary attenuation with the new tweeter. I fact I would say the coils on my original FB1 crossover are wound more cleanly that the ones in the pictures here...
 
Now I'm confused:

http://www.solen.ca/pdf/vifa/d27tg3506.pdf

http://tymphany.com/files/products/pdf/D27TG-35-06 Website Specification Sheet Rev 1_0_0.pdf

Older version of spec sheet posted at Solen (where I ordered drivers from) - DCR = 4.6, Resonance = 650 Hz, SENSITIVITY 91dB (exactly the same DCR, Z, and Sens of D25AG-05-06 from original FB1)

Newer version of spec sheet from Tymphany site - DCR = 4.9, Res = 720 Hz, Sensitivity = 92.5 dB!!! This looks like the specs the new FB1+ crossover was trying to meet.

The mechanical spec depth is also significantly longer on the new spec sheet but both sheets claim double chamber.

I guess once I receive the drivers I'll measure the depth to decide which spec sheet to use (looks like the old one would be a direct swap in with the original crossovers)
 
Is it typical to have so many contradictory spec sheets for the same product?
You are assuming the published specs are accurate in the first place, or there is enough product consistency from one batch to another. The only way to know for sure is to measure the drivers yourself. Anything else is pot-luck.

James
 
Sorry resurrecting an old thread but I'm really interested in what PMC actually did here.

Didn't PMC have the Vifa D27TG-35-06 in their original designs such as DB, GB OB etc and then upgrade to a Sonolex tweeter in the i's? I cant even find those new Sonolex as parts.

https://www.falconacoustics.co.uk/vifa-d27tg3506-tweeter.html

Were they basically these with a fancy pattern ring stuck on the outside?

https://www.falconacoustics.co.uk/seas-27tffc-h0881-tweeter-prestige-series.html

The original Vifa D27s are considered good tweeters was it actually an upgrade to the Sonolex?

And what did they do with the + models? Did anyone actually compare models?

I will thank you for the clarification, it would be very much appreciated :)
 
I will thank you for the clarification, it would be very much appreciated
Given their length of time in the game and their order quantities it seems unlikely to me that PMC would use off-the-shelf DIY parts rather than something manufactured to their specification. Mind you they have been doing what looks to me like odd things with some of their home speakers and so I am not speaking with great conviction. If they are using off-the-shelf parts they would have to pay extra to remove the labels and so perhaps people seen standard driver manufacturer labels on PMC speaker drivers? Tooling for driver metalwork is expensive and so the frames being the same as off-the-shelf drivers is not a good indicator of a driver in a commercial speaker using off-the-shelf DIY drivers.

Do you know the specification of the foam used in the line which is likely to be significant given it's role in letting through just the right amount of low frequency sound while impeding as much sound as possible at higher frequencies?

If you opt for similar in looks off-the-shelf drivers and want a reasonable technical performance you may be forced to design an appropriate line and crossover.
 


advertisement


Back
Top